Hypoxia in aviation is a problem of altitude.It is very important that pilots are alert on how the human body responds to flying at high altitudes when they transition from their light training airplanes to complex high performance aircraft’s that are capable of operating at high altitudes and high speeds.Before we get to know what hypoxia is, we need to understand the relationship of oxygen in our body with altitude.

Oxygen and Altitude

Oxygen is a colourless and odourless gas that makes up 21% of the earths atmosphere by volume. The brain weighs approximately 2% of our body weight but consumes almost 20% of the oxygen that our body needs for its normal functioning.Brain cells die if they don’t receive oxygen for 2 minutes.

Alveoli are tiny sacs in the lungs of a human body where the exchange of oxygen and carbon dioxide takes place through breathing in and out. Therefore it is clear that at anytime the concentration of oxygen should be high and that if carbon dioxide should be low in the alveoli.

According to International Standard Atmosphere (ISA) conditions, the standard pressure at mean sea level is 1013 hectopascal (760 mm Hg). As mentioned above if 21% of the atmosphere is filled with oxygen , it means out of the 760 mm, 160 mm is oxygen. This is what we call partial pressure of oxygen in the air. The human body takes its oxygen from alveoli in the lungs where the partial pressure of oxygen is relatively less (103 mm Hg) as compared to the partial pressure of oxygen in the atmosphere (160 mm Hg).

As we move up to higher altitudes, the amount of partial pressure of oxygen generated by the alveoli also starts reducing. Human beings living at higher altitudes like 10-12 thousand ft above mean sea level, their alveoli produces partial pressure of 55 mm Hg oxygen which is considered to be the minimum for normal operations.

Hence as we go above 10 000 ft, oxygen needs to be added to the cabins air supply .The oxygen that gets added is sufficient to maintain a partial pressure of oxygen that is similar to what humans require on ground (103 mm Hg). A stage is reached where 100% oxygen supply is required to maintain the 103 mm Hg of partial pressure ( what we breathe on the ground)

This stage is at approximately 33,700 feet. However this does not mean that we cannot go above 33, 700 feet, as we discussed above for our normal operations in the body we require a minimum of 55 mm Hg of partial pressure ( what we would breathe at 10 000 feet) . With 100% oxygen supply, this is reached at 40 000 ft .


Hypoxia ( HYPO= less , OXIA=oxygenation) is a condition where not enough oxygen makes it to the cells and tissues in the body. This can happen even though blood flow is normal. Hypoxia can lead to many serious, sometimes life-threatening complications.The most common causes of hypoxia in aviation are: flying, non-pressurized aircraft above 10,000 ft without supplemental oxygen, rapid decompression during flight, pressurization system malfunction, or oxygen system malfunction.

Types of Hypoxia and their Causes:

  • Hypoxic Hypoxia (H) :The reason for this type of hypoxia is the result of low levels of oxygen in the bloodstream. The main reason for this condition occurring in aviation is altitude. As we have discussed in detail above that with increase in altitude, there results a fall in atmospheric pressure and the consequent resultant drop in the partial pressure of oxygen leading to Hypoxic Hypoxia.
  • Anemic Hypoxia (A) :In this type of condition , the lungs are working perfectly but the red blood cells which are the carriers of oxygen in the blood decrease. The reason for the decrease in the count can be due to heavy bleeding, anemia, some type of cancer and lastly the intake of carbon monoxide.
  • Stagnant Hypoxia (S) :In stagnant hypoxia, there is enough oxygen available to breathe but the blood flow is compromised for some reason like a heart attack and the blood is not received by the cells of the body tissues to support their metabolism.Stagnant hypoxia also occurs when the body is exposed to cold temperatures because the blood flow is decreased to the extremities.
  • Histotoxic Hypoxia (H):In this category of hypoxia, there is enough oxygen to breathe and the oxygen is also being carried by the blood but the cells do not accept it. For pilots, some of the primary factors causing hystotoxic hypoxia are alcohol, narcotics and cyanide.

Signs and Symptoms of Hypoxia:

Hypoxia is easy to succumb to the human body and affect each body with varying intensities. even though the condition does not have an alarming warning system to protect us against us the treat, the signs and symptoms are easily recognizable if we identify them. As pilots we need to km=now that no matter the type or cause of hypoxia, the signs and symptoms for each type do not differ a lot and neither do they affect our flying skills in separate ways.

The signs and symptoms are mentioned below:

  • The onset of hypoxia can be accompanied by a feeling of well being, known as euphoria.
  • Impaired Judgement
  • Headache
  • Tingling in hands and feet
  • Hyperventilation
  • Memory and Muscular Impairment
  • Sensory Loss
  • Cyanosis (a bluing of the body extremities)
  • Tunnel Vision
  • Fornication ( a feeling of ants under the skin)
  • Hyperventilation (over breathing)
  • As hypoxia keeps intervening with reasoning, it gives rise to unusual fatigue and finally loss of consciousness or death.

Time of Useful Consciousness (TUC)

This is the period of time from interruption of the oxygen supply, or exposure to an oxygen-poor
environment, to the time when an individual is no longer capable of taking proper corrective and
protective action.It is also know as Effective Performance Time (EPT). We are clear by now that as altitude increases the risk of hypoxia increases and due to that our time for useful consciousness will decrease. Hence, altitude and time for useful consciousness are inversely proportional.The chart below will make it even more clear:

Immediate and Preventive Actions

  • One way to avoid the risk of hypoxia for a pilot to make sure that his aircraft is correctly pressurized above 10,000 feet.
  • In case the aircraft cannot be pressurized, carry supplemental oxygen (don your oxygen mask).
  • If both the above options are not available, it is safe to be flying below 10 ,00 feet and even if we fly above that altitude due weather or terrain, we limit our time to a maximum of 1 hour if flying between 10 to 14,000 feet and 30 minutes if flying between 12 to 14,000 feet.
  • The most important action will always be to use supplemental oxygen above 10,000 feet in day and 5,000 feet at night ( vision gets impaired at a lower altitude in the night due to hypoxia).
  • The most effective way to prevent hypoxia is through education and experience.When pilots are trained in the proper use and care of their pressurization systems and supplemental oxygen equipment, and are aware of their personal hypoxia signs and symptoms, they are safer and better prepared to meet the challenge of flying in an oxygen-poor environment.

Fact of the Week

Boeing’s Everett Site is heralded as having the largest manufacturing building in the world, producing the 747, 767, 777, and the 787 airplanes. Thousands of aerospace employees in Everett support aircraft fabrication and production, product development, aviation safety and security and airplane certifications. Other production areas at the site include the paint hangars, flight line and delivery center. Originally built in 1967 to manufacture the 747, the main assembly building has grown to enclose 472 million cubic feet of space over 98.3 acres.

In January 1967, the first production workers arrived at Everett, and on May 1, 1967, the major assembly buildings opened their doors for the first time. Thousands of people from all over the world visit the Everett site every year. VIP visitors have included U.S. presidents, international dignitaries, CEOs, astronauts and other celebrities.Click the link to know more about this huge airplane manufacturer building https://www.boeing.com/company/about-bca/everett-production-facility.page

We are done for this week. I hope you gained some new insight from this post and if you did please share with it with your fellow aviators and aviation lovers. I encourage you to like this post as it gives me great confidence from your’e interest in these topics. If you have any suggestions please feel free tom drop in a comment or an email, I would be happy to reply. Until next week , stay safe and stay healthy.



Fuel is a material used to produce heat or power by burning. The burning fuel can be used to generate power for lamps, heaters , stoves, lanterns and for running automobile and jet engines. Aviation fuel must meet the strict requirements for flying characteristics and are hence different from the fuel used in automobile engines.

Car Fuel vs Jet Fuel

An internal combustion engine is used to power a car where as a gas turbine engine is needed to power a jet. As mentioned above, they both would require some heat source by burning some sort of fuel to power the engine.

Where car and jet fuel differ is just the number of hydrogen and carbon atoms that are presenting the fuel. For example, car fuel ( gasoline) consists of hydrocarbons that contain anywhere from 7 to 11 carbon atoms with hydrogen molecules attached. Jet fuel, on the other hand, contains hydrocarbons more in the range of 12 to 15 carbon atoms, that is, kerosene.

Therefore, airplane fuel is derived from a much heavier chain of hydrocarbon molecules and the main reason for using it is safety. It takes a higher temperature to ignite kerosene as compared to gasoline. Kerosene is also easily transported and available throughout the world and can stay in the liquid form at lower temperatures which is very important as an airplane flies thousands of feet above the ground.

Understanding a Few Terms

  • Octane Rating/Number: It is a measurement of the quality or performance of the gasoline used. When you go to a gas station to fill petrol , the octane ratings are depicted by regular, mid-grade or premium. The higher the octane rating / number, the better the fuel burns in the engine and hence high performance cars have a need for higher octane ( premium) fuel. Similarly, the gasoline used in airplanes will have a higher octane rating than the gasoline used in cars.
  • Specific Gravity (SG) :Specific gravity also called relative density, ratio of the density of a substance to that of a standard substance.The usual standard substance used for comparing is water . Fuels have specific gravity less than water, which means that they float on water. This helps in identifying the presence of water in fuel during a fuel check .
  • Waxing Point : Waxing point, as the name suggests are the low temperature at which heavy hydrocarbons that are used in making jet fuels as discussed above, turn into wax crystals which clog the fuel filter. This could lead to operation limitations in the fuel system.
  • Flash Point: Flash point is the lowest temperature at which a liquid when exposed to an open flame will turn into vapour. Below the flash point, insufficient vapour is present to support combustion.

Types of Aviation Fuel

Aviation Fuel is divided into 4 categories:

  • Aviation Gasoline (AVGAS)
  • Jet Fuel (JET A and Jet A-1)
  • Kerosene-Gasoline Mixture ( AVTAG OR JET B)
  • Bio Kerosene

Aviation Gasoline (AVGAS)

  • AVGAS is the type of aviation fuel used in small piston engine powered aircraft within the general aviation community. These aircraft are predominantly used by private pilots and flying clubs and for tasks such as flight training and crop dusting.
  • The octane rating of the fuel is specified with the grade , for eg AVGAS 100 is a 100 octane fuel.
  • AVGAS 100 LL and AVGAS 100 are the most commonly used grades of fuel .
  • The AVGAS 100 LL (low lead) and the AVGAS 100 have a lean mixture octane rating of 100 while its rich mixture octane rating is 130 that allows high performance engines to operate safely.
  • The way to differentiate between these two grades of fuel is by their colour . The AVGAS 100LL is BLUE in colour whereas AVGAS 100 is GREEN in colour.A good way to never forget how to differentiate is by noticing that the word Blue and AVGAS 100LL have the letter L.
  • AVGAS 115 was a high-octane avgas mostly used in military combat aircraft in the late 1940s when there was demand for high power output. Now, most military aircraft use turbine engines.

Jet Fuel

  • Gas turbine engine aircraft’s use kerosene fuels.The two types of kerosene fuels used in civilian gas turbine engine aircraft’s are Jet A and Jet A-1.
  • Jet A is a kerosene type of fuel with a specific gravity of 0.8 at 15 degrees C. It has a flash point of 38.7 degrees C and and a freezing point of -40 degrees C.
  • Jet A-1 is similar in comparison to Jet A but has a freezing point of -50 degrees C. It is normally only available in the U.S.A.

AVTAG Fuel (Jet B)

  • AVTAG also called Jet B is a kerosene-gasoline mix type fuel with a nominal specific gravity of 0.77 at 15 degrees C.
  • Jet B can be used as an alternative to Jet A but it has a wider range of flammability as it has a lower flash point and hence is not generally used in civilian aircraft’s .

Bio Kerosene

  • Jet fuel is a type of fossil fuel and eventually will become expensive in the long term.
  • Biokerosene is a mixture of jet fuel and a biofuels which are being used since 2008. There have been approximately 1,50,000 flights that have used Biokerosene to power their aircraft.
  • However these fuels are more expensive than jet fuels and this cost premium is a key barrier to their wider use.


The primary types of contamination are water, particulate and microbiological material. In addition, contamination can occur from other fuel grades and chemicals that may be in multi-product transport systems. The fuel may also be rendered off-specification by either under-dosing/overdosing of approved additives, using an incorrect additive or from product testing issues not limited to, but including, poor sampling, incorrect test procedures and uncalibrated laboratory equipment.


Jet fuels composition allows water to absorbed easily. The degree of water present depends mostly on the temperature of the fuel. When the temperature of the fuel is less, some of the water particles that are already present in the fuel draw out of the solution and accumulate at the lower points of the tank. When the fuel is warmer, it promotes the absorption of moisture from the atmosphere and suspension in the fuel.

Microbiological Growth

Certain bacteria and fungi thrive on the presence of water where it interfaces with jet fuel. The growth of microbial organisms leads to the corrosion of aluminium, steel and rubbers components of the fuel system.


Particulate contamination can occur in a number of different ways. From dirt and sand getting in open ports to degradation of fuel system lines , particulates are constantly being introduced into the fuel system.

Fuel Inspection

During our preflight , if we carry the fuel inspection in a correct manner then the identification of any fuel contamination is not difficult. If a fuel sample appears cloudy of hazy , it could be because of two reasons, the presence of air or water. If the cloudiness appears to be moving towards the top of the sample then air is present , if the cloudiness appears to be moving towards the bottom of the sample then water is present as water has a higher specific gravity than fuel.

Picture Credits: BoldMethod

During fuel sampling ,fuel is drained into a clean and clear container that is filled at least halfway. After collecting the fuel sample, observing it against light helps in identifying water or particulates that could be present. Swirling the sample around by creating a tornado shaped vortex is another way of identification of fuel contamination. The absence of water at the lower points of the tank automatically leads to the elimination of microbial growth. The addition of jet fuel additives can also eliminate the growth of bacteria and other microbes.


A number of additives maybe blended into fuel either at the refinery or the airfield to improve the operational ability of the fuel. The most popular ones are:

  • Fuel System Icing Inhibitors (FSII) : A certain amount of water is present in fuels as discussed above. FSII contains an icing inhibitor and a fungal suppressant to deal with fuel contamination due to water and microbiological fungus that can block fuel system components.
  • HITEC (Lubricity Agent) : A lubricity agent when added to fuel can reduce the wear in fuel system components.
  • Static Dissipater: These additives partially eliminate the hazards of static electricity generated by the movement of fuel through modern high flow fuel transfer systems .
  • Corrosion Inhibitors: The corrosion inhibitors protect ferrous materials in pipelines, storage tanks against corrosion.

Fact of the Week

Concorde was born out of two separate French and British projects which joined forces in 1962. This partnership led to the British Aircraft Corporation (later British Aerospace, and now BAe Systems) and Aerospatiale (now EADS) of France to build a total of 20 Concordes, and became the foundation stone for the formation of Airbus.

Concorde recorded its fastest journey from New York to London on January 1st 1983, taking 2 hours 56 minutes.For most people, flying on Concorde is an impossible dream, the stuff of lottery wins and holidays of a lifetime.For the lucky few, ‘The Bird’ is a convenient method of travel, the equivalent of a bus or a train to the rest of us.Fred Finn was on the first and last Concorde flights and holds the Guinness World Record for the most Concorde flights as a passenger!. Click the link in the link here to know more about this iconic jet https://www.heritageconcorde.com/concorde-information–facts.

Picture Credits: Christian Science

This is to this weeks post. Thank you for reading and hopefully you gained some new knowledge about aviation from this post. If you did , please don’t forget to share it with fellow aviation lovers and don’t forget to comment down below for suggestions. Until next week, stay safe and stay healthy.


Fly-by-Wire ( FBW) Technology

One of the first lessons that student pilots are taught in their training is the relationship between the pitch attitude and power settings required to control the aircraft. Once you get more comfortable and experienced as a pilot, you start your instrument flying journey where you notice how important those initial lessons were on pitch and power as the margin of error is limited and your workload is at it’s peak.

Hence it could be so much easier if there was a system which could control the path of the airplane without the pilot constantly trying to adjust the controls and just obtain the desired pitch attitude and leave the yoke/side-stick without trimming or adjusting the power setting (with the help of the auto thrust – more on this later) . The fly by wire system makes flying much more easier by being that system. It not only controls the path of the aircraft but provides a flight protection envelope as well.

Conventional Flight Control Mechanism

Picture Credits: Slideshare
  • The Wright Brothers used combinations of their body movements to deflect the portions of their FLYER, causing it to move in the desired directions.
  • In a conventional light weight trainer type aircraft , cables are connected to the controls in the cockpit through a bell crank and the other side of the bell crank is connected to the control surface.Movement of the cockpit controls transfers force through the cable to the bell crank, which moves the control surface.
  • However in a high performance aircraft, the control surfaces have great pressure exerted on them and hence it is physically impossible for the pilot to manually move the controls. Hence, hydraulic actuators (cylinders) are placed in the link to assist the pilot in moving the control surface.

Fly-by-Wire System

  • As discussed above, flight controls could be handled mechanically or hydro-mechanically.However, a fly wire system is an electrical way of controlling the flight controls in an aircraft.
  • The fly by wire system adds in an electronic interface to control the aircraft . The pilots command are converted into electronic signals that are interpreted by the flight control computers.The computers interpret the pilot input and determine how to move the actuators connected to the flight control surfaces,as necessary, to follow their orders.
  • The actuators are still hydraulically operated that are similar to the hydro-mechanical system.The computer monitors the aircraft’s response to the flight control movement and modifies its output accordingly to the actuators.

Airbus 320 Fly-by-Wire System

  • In the Airbus 320, there are 7 flight control computers and 3 hydraulic systems to take care of the primary flight controls (elevator, aileron, rudder) .
  • Each primary control has 2 hydraulic actuators, each fed from one of the three independent hydraulic systems.
  • The 7 flight control computers are :
    • There are 2 Elevator and Aileron Computer (ELAC) to control the elevators, ailerons and stabliser.
    • There are 3 Spoiler Elevator Computer (SEC) to control the spoilers ( more on the functioning of spoilers in a separate post) and elevators.In the event of the ELAC failing , the SEC will control the elevators and stabiliser.
    • The rudder is controlled through hydro-mechanical pedals by the pilot, however there are 2 Flight Augmentation Computers (FAC) that operate the rudder to keep the aircraft balanced in a roll.
    • The stabiliser trim can be mechanically controlled by the pilots trim control wheel.
  • To summarise, the elevators and ailerons have access to 5 computers in total and only one is needed for operation.There are 3 hydraulic systems out of which only 1 or 2 are needed for operation, it shows that the system has electrical and hydraulic redundancy built into it .
  • In the event of a total electrical failure, the pilot can control the aircraft manually using the trim wheel for lateral control and rudder pedals for longitudinal control.

Advantages of the Fly-by-Wire System

  • Reduced Weight :Mechanical and hydro-mechanical flight control systems are relatively heavy and require careful routing of flight control cables through the aircraft by systems of pulleys, cranks, tension cables and hydraulic pipes.Hence replacing these with actuators , sensors directly reduces the weight of the aircraft .
  • Flight Envelope Protection: The protection prevents the aircraft from performing manoeuvres outside the flight envelope. For example , stalling or over speeding.
  • Improved Flight Controls: With the help of the fly by wire system, the pilot need not provide excessive control inputs as the computer determines how to move the actuators connected to the flight control surface.
  • Increased Commonality: After the rise of the Airbus 320 family, In terms of Airbus aircraft’s, no matter how one aircraft varies in size or weight from another, fly-by-wire commonality allows the pilot to fly them in the same way because the computer “drives” the aircraft’s flight controls. This leads to considerable reductions in the time and costs involved in training pilots and crew to operate them.
Advantages of the Fly-by-Wire System

Disadvantages of the Fly-by-Wire System

  • Redundancy: The failure of an electrical system could lead to a complete shutdown where as the traditional mechanical flight control system fails gradually and makes the pilot more aware of the failure. The loss of the aircraft flight control computer could immediately make the aircraft uncontrollable.However, in commercial airplanes, this problem is solved by using redundant computers and providing mechanical backup in case of total electrical failure.As seen above, in the working of the Fly-by-Wire system of the Airbus 320.
  • Lack of visual feedback: As the control is not physically connected to the control surface, feedback is lost. The side sticks in the aircraft are not connected to each other that, this means that, the input provided on one side stick cannot be felt on the other and hence visual feedback from the stick is lost.
  • Over dependence on FBW: Murphy’s law states that : “Anything that can go wrong will go wrong ”. Pilots are sometimes guilty on relying heavily on automation. There is no doubt that computers aid pilots in making flying easy but Murphy’s law holds true and there is always a chance for them to fail.

History of the Fly-by -Wire System

  • AVRO CANADA CF-105 ARROW: The Avro Canada CF-105 Arrow (the Arrow) was a supersonic interceptor jet aircraft designed and built in the 1950s by A.V. Roe Canada (Avro). It was fitted with innovative technologies, including a fly-by-wire control system and a computerized control system that allowed the pilot to operate the aircraft electronically. It was canceled on the February 20, 1959 (known as “Black Friday”), a decision that remains controversial today.It was the first non experimental aircraft with fly-by-wire controls.
  • LUNAR LANDING RESEARCH VEHICLE (LLRV) : On May 25, 1961, President John F. Kennedy committed the United States to landing a man on the Moon and returning him safely to the Earth before the end of the decade.In December 1961, NASA Headquarters in Washington, D.C., received an unsolicited proposal from Bell Aerosystems in Buffalo, New York, for a design of a flying simulator to train astronauts on just that challenge.Bell Aerosystems delivered the LLRV-1 on April 8, 1964, where it made history as the first pure fly-by-wire aircraft to fly in Earth’s atmosphere. Its design relied exclusively on an interface with three analog computers to convert the pilot’s movements to signals transmitted by wire and to execute his commands.
  • F-8C CRUSADER: In 1972, NASA gave the world the next big thing in flight controls when the agency’s Dryden Flight Research Center showed how to use the digital fly-by-wire (DFBW) system, the computerized system is used today on everything from jet airliners to cutting-edge fighters and stealth bombers. Dryden’s DFBW aircraft — an F-8C Crusader given to NASA by the U.S. Navy — flew for the first time on May 25, 1972.The program’s chief research pilot, Gary Krier said “Everyone on the program knew that what we were doing was going to be a major breakthrough in flight control”.
  • AIRBUS Fly-by-Wire SYSTEM :One of the A300-600 and A310’s notable innovations had been the introduction of electrical signalling on secondary flight controls, replacing the web of cables and pulleys tradionally used. Airbus wanted to take this evolution further with the next Airbus aircraft – to computer-driven digital “fly-by-wire”, in which the deflections of the flying control surfaces on the wing and tail are no longer driven directly by the pilots’ controls, but by a computer which calculates exactly which control surface deflections are needed to make the aircraft respond as the pilot wishes.
  • DASSAULT FALCON 7X: From its inception, the Falcon 7X was destined to be a revolutionary aircraft, introducing business aviation to the industry’s first Digital Flight Control System.Not only does the 7X handle like a fighter jet, it’s controlled like one. In the cockpit, the pilot’s hand falls naturally on a side-stick controller. Pilots love the 7X intuitive responsiveness and precision. Passengers appreciate its silk-smooth ride and the contribution such an advanced technology makes to aircraft safety.


It was on February 10, 1929 that India got its first licensed pilot in Jehangir R.D. Tata, who qualified with number 1 on his flying license, giving birth to Indian aviation.J.R.D’s license, then called an ‘aviators certificate’, was issued by The Aero Club of India and Burma, an associate of the Royal Aero Club of Great Britain, which was authorised to issue licences by the British Empire’s Federation Aeronautique Internationale. The Aero Club of India and Burma was recognised by Federation Aeronautique Internationale as a sporting authority.

J.R.D. launched India’s first airmail service in 1932, when he flew into Mumbai in a De Havilland Puss Moth from Karachi’s Drigh Road Aerodrome to the Juhu Airstrip via Ahmedabad on the basis of this flying license.This later became the country’s national carrier, Air India.Click the link to know more about iconic figure in aviation history : https://www.tata.com/newsroom/wings-for-a-nation

This is it for this weeks post. I hope you gained some knowledge and if you did, please share it with your fellow aviators . Please feel free to reach out to me via Email, Instagram or Twitter, you’re feedback is always valued. Thank you for you’re support . Until next week , stay and stay healthy.



Aviation makes the world a smaller place and international airlines play a huge role in connecting people from across the globe with different cultures together.International airlines as many international companies all over the world hire people from different countries. For example, Emirates Airlines recruits pilots from all over the world and there are 52 different nationalities of pilots currently in the airline. The top three nationalities being British, Australian and Canadian.

Need for Aviation Language

With such diversity in the crew, the focus on communication is very important. The flight crew, cabin crew , air traffic controller , in short, the entire aviation community need to communicate in a common language. In the history of aviation , a lot of accidents and incidents such as the Tenerife Airport runway collision or the Charkhi-Dadri Mid Air collision have time and again reminded us as aviators the importance of communication.

A)Controller: Descend two four zero zero feet.
In this message, the similarity between “two” and “to” led the pilot to understand 400 feet instead of 2 400 feet. The aircraft crashed into high ground.

B)Pilot: We are at take-off.
In this message, the controller understood that the pilot was waiting in position to begin the take-off, whereas the aircraft had actually begun to accelerate along the runway. It collided in foggy conditions with another aircraft.

The points A and B highlight the ease with which miscommunication can be of serious consequence and impact safety.

What is Aviation Language?

The field covered by the term “aviation language” is relatively broad. It could include all of the language uses of many different professions (engineers, technicians, commercial staff, flight crews, etc.) within the aviation domain.The sole object of ICAO language proficiency requirements is aeronautical radiotelephony communications, a specialized subcategory of aviation language corresponding to a limited portion of the language uses of only two aviation professions — controllers and flight crews.

The language spoken in aviation is called ICAO (International Civil Aviation Organization) English. The ICAO, recommended English to be the language for aeronautical radiotelephony communications in 1951 as most of the English speaking countries dominated the aviation market.English is a first language or a widely used national language in approximately sixty counties and is an important second language in many more.Non-native users of English outnumbered native users at the start of the 21st century by approximately 3 to 1.

Language Proficiency Requirements

Since the 5th of March 2008, every pilot or flight crew member coming into contact with international aviation communication including air traffic controllers must pass a language proficiency exam in compliance with ICAO regulations.

A language proficiency rating scale was developed as a guide to judge pilots and air traffic controllers over their command on the language. The scale was only tests speaking and listening skills and does not address reading and writing skills.

The scale is divided into 6 levels. Levels 1 to 3 on the rating scale assist the examiner on recruiting and training the candidate while Levels 4 to 6 set up a minimum operational requirement. Hence pilots need to need to make sure their language skills meet at least the ICAO Level 4 requirements.If a pilot gets a level 6 rating, he is granted an exemption from the need to be re-evaluated from time to time.

The Language proficiency exam tests consists of pronunciation, structure (use of tense etc), vocabulary, fluency, comprehension and interaction. However to acquire an ICAO Level 4 rating does not require high degrees of grammatical correctness and traditional English language .

Level 1,2 and 3 on the Rating Scale
Level 4 ,5 and 6 on the Rating Scale

ICAO Phonetic Alphabet

The International Civil Aviation Organization created the international radiotelephony alphabet, tied to the , English Alphabets . They were created to avoid the confusion between similar sounding alphabets such as B and D or M and N. Therefore on the radio the ATC will instruct the pilots the to “ Hold short of holding point APLHA” and not “Hold short of holding point A” .


The foundation’s of standard phraseology were laid in the Annex 10 Volume 2 of the ICAO Annexure. Standard phrases are of extremely useful in emergencies and unusual situation and helps keep communication concise.Therefore learning the new aviation alphabets is not the only difference in the aviation language, pilots and ATCs need to have these standard words and phrases registered in their memory.

There are about 300 standard words and phrases that are used. Some of the most common ones are listed below along with their meaning:

  • Acknowledge: Let me know when you have received and understood the message
  • Affirm: Yes
  • Approved: Permission for proposed message granted
  • Break: I hereby indicate the separation between portions of the message (to be used where there is no clear distinction between the text and other portions of the message)
  • Break Break: I hereby indicate separation between messages transmitted to different aircraft in a very busy environment
  • Cancel: Annul the previously transmitted clearance
  • Check: Used to examine a procedure or system
  • Cleared:Authorised to proceed under specific conditions
  • Confirm:Have you correctly received the message ?
  • Contact : Establish radio communication with …
  • Correction: An error has been made in the previous transmitted message. The corrected message is …
  • Disregard: Consider the transmission as not sent
  • I say again: Repeating for clarity of the message
  • Maintain: Continue in accordance with the condition specified . for eg, ‘Maintain VFR’ (VFR- Visual Flight Rules)
  • Mayday: My aircraft and its occupants are threatened by grave and imminent danger and/or I require immediate assistance
  • Negative: Permission not granted
  • Over: My transmission has ended and I expect a response
  • Pan Pan: I have an urgent message to transmit concerning the safety of my aircraft, or other vehicle or of some person on board, or within sight, but I do not require immediate assistance
  • Read Back: Repeat all, or the specified part, of this message back to me exactly as received
  • Report: Pass me the following information
  • Request: I wish to obtain
  • Stand by : Wait , I will connect with you in a bit
  • Wilco: I have understood your message and will comply with it

FACT OF THE WEEK: Mason Andrews, age 18 Yrs 163 Days became the youngest person to circumnavigate the globe in an aircraft when he completed his journey in Monroe, Louisiana, USA on the 6th of October 2018. Mason flew a single engine Piper PA -32 around the world in 76 days.

Andrews’s journey was only made possible by initially telling his parents he was flying solo across the Atlantic and no further. His parents were resistant to even allow this trip, but they were eventually persuaded by the scale and detail of his preparations. It was only later that they learned of the worldwide trip he was planning.

This is it for this weeks post. I hope you gained some new knowledge from it. Please share it with your fellow aviators and enthusiasts if you liked this post. Feel free to comment for suggestions. Until next week , stay safe and stay healthy .



The development of electronic communications over a period of time has been a big advantage for the aviation industry.The Airbus believes in Fly , Navigate and Communicate . With the help of electronic communication, the emphasis on verbal communication between the pilots and the air traffic controller has reduced severely .This helps aviators to concentrate on flying the aircraft which is of utmost importance.

Transponders and squawk codes help in reducing verbal communication and help maintain a silent cockpit.They assist the air traffic controller in knowing the aircraft position on their radars.



A transponder (XPDR) as the name suggest is a transmitter and receiver. It is an electronic device that produces a response to an interrogation signal sent by the air traffic controller.

It was initially used in the military to identify aircraft’s . It was termed as ‘Identification of Friend or Foe’ as a military aircraft sent interrogation signals to another aircraft to find out if they are their friends or foes .

However , in commercial operations, as we only have friends we do not use these terms . The Air traffic controller assigns each aircraft a squawk code which enable them to identify the aircraft on their radar and other aircraft’s collision avoidance system.

Conventional Transponder


The ground based equipment transmits interrogation pulse signals on a frequency of 1030 MHz (Megahertz) and receives on 1090 MHz.While the Aircraft transponder , transmits on 1090 MHz and receives on 1030 MHz .

Signals from the ground transmitter are transmitted in pair of pulses that are coded and each code is known as a MODE.There are a few modes that will be discussed down below. The replies from the aircraft are however in all directions.

The ground receiver then decodes the reply from the aircraft and displays the necessary information such as aircraft call sign, altitude , speed etc on the radar.


The different modes of transponder help us gain different information of the aircraft .

  • MODE A:This type of transponder provides an identification code only .
  • MODE C: In Mode C, along with identification code , aircraft pressure altitude is provided as well .
  • MODE S: In Mode S (selective) ,there are a number of details that can be provided along with aircraft identification code and altitude. For example, aircraft ground speed , destination of the aircraft , desired track etc.

A Mode C transponder is commonly found in general aviation aircraft’s where as the commercial jets are equipped with Mode S transponder. In the flight plan that is needed to be file before a flight , it is necessary to mention the type of surveillance equipment (transponder) installed on board. In the ICAO flight plan, the necessary details are included in box 10,that is , Equipment ( more on flight plan in a separate post).



Once the ground receiver has decoded the information, the radar displays the necessary information depending upon the mode of transponder. The different aircraft’s are shown as a blip or a trace on the radar screen.In the figure down below , the example shows the aircraft is equipped with a MODE S transponder.



A-320 Transponder

STBY: The Stand By function powers up the transponder and makes it available for operation.

ON : In the ON position, it will send primary information to the radar, that is , it will work like a MODE A transponder.

ALT:If the ALT RPTG is in the ON position , the transponder will send altitude data and will work like a MODE C/ MODE S transponder.

IDENT: All modes (A,C,S) include an ident button.It reveals the identity of the aircraft to the ATC on their radar and helps them locate the aircraft too. For example, when the ATC requests the aircraft to ‘SQUAWK IDENT’ , the pilots need to press the ident button which leads to the aircraft blip on the radar to flash and enables the controller to easily identify the aircraft among many other that are near it.


What are Squawk Codes?

Transponder transmission usually requires a discrete code to identify the aircraft. These codes are assigned by the ATC to each aircraft in their departure clearance.

The squawk codes are 4 digit octal numbers from 0 to 7 and range from 0000 to 7777. Once the pilot receives his squawk code , he has to enter the 4 digit code so that he is visible on the radar .

Let’s take an example, the controller on your departure clearance assigns the pilot to squawk 1234. The pilot can enter 1234 via the numbers shown in the image below and the screen will display the squawk code entered.

Reserved Codes

There are a few transponder codes that have a predetermined meaning and should be used when the aircraft faces that occurrence.

In the above mentioned reserved codes, it is always a good idea to remember the last three codes as they notify the ATC immediately of the problem. As a good rule of thumb, I remember the word ice, that is, interference communication emergency and corresponding to those are the codes, which are, 7500 7600 7700.

Check the image on the right to have a better understanding.

FACT OF THE WEEK: This week we go back to the years where the Wright Brothers were busy making their first powered airplane . A powered airplane would require an engine for the aircraft to take flight. Charles “Charlie” Taylor a mechanic who worked at the Wright Brothers bicycle shop stepped up to help them in their pursuit and became the first man to build an engine that powered an airplane and the first aviation mechanic in history. If it hadn’t been for Charlie the first powered airplane would never have gotten off the ground.

Please click on the link to know more about Charlie Taylor https://www.faa.gov/about/office_org/field_offices/fsdo/phl/local_more/media/ct%20hist.pdf

We are done for this week. I hope you gained some knowledge from this post and if you did please like and share it with your fellow aviators.Please feel free to comment if you have any doubts or suggestions for further posts. Until then stay safe, stay healthy.



“CLEARED FOR TAKE OFF”- when a pilot hears these words from the Air Traffic Controller, he knows it is time for him to bring the highest order of focus he can for one of the most critical phases of flight , that is ,take off.

Need for Take off Segments

One of the significant emergencies that an aircraft can face is an engine failure on take off , it means that the engine is no longer providing the necessary thrust needed.In order for the aircraft to be safe from any emergencies that may occur , it is necessary that it achieves the minimum climb gradients and clears its surrounding area and obstacles with sufficient altitude. Hence the take off segments help in achieving the above requirements.

Understanding a few terms

Before we look at the different segments of climb, it is necessary to understand a few terms related to the take off segments as it will help us understand the post better.

SCREEN HEIGHT:The take off part of the flight is the distance from where the brakes are released to the point at which the aircraft reaches a defined height.This defined height is known as screen height.It is usually 35 ft (for class A aircraft) on a dry runway and if the runway is wet it can reduce down to 15 ft.

TAKE OFF SAFETY SPEED (V2): V2 is the target speed the aircraft should attain prior to or before reaching the screen height. The reason it is called take off safety speed is because it should be attained with one engine inoperative and avoid the aircraft from stalling or the pilots loosing control of the aircraft.


CLIMB GRADIENT:The ratio of change in height (altitude gained), during a portion of a climb, to the horizontal distance traversed in the same time period.It is expressed as a percentage. It also refers to the angle at which the aircraft climbs.For an aircraft to climb , thrust has to balance drag and a part of the weight as well . Hence we require excess thrust to give us the climb gradient or angle of climb .

Climb gradient =Excess Thrust *100/Weight

The take off climb segments start from the screen height that is 35 ft above the take off surface and end at 1500 ft above the take off surface and are divided into 4 segments.

Segment 1

  • The first segment starts when the aircraft reaches the screen height, that is 35 ft .
  • The aircraft keeps climbing at the take off safety speed, that is V2 speed, until the gear is retracted.
  • The objective of this segment is to expedite the climb and to make sure there is reduction in drag .
  • There are two ways to reduce drag in this scenario , retracting the flaps or the landing gear.
  • Since retracting the flaps very close to the ground is dangerous, we choose the option of retracting the gear .
  • The first segment ends as soon as the landing gear is retracted .

Segment 2

  • The second segment commences from the gear retraction point and the aircraft still has to maintain the take off safety speed (V2).
  • The next important step is to retract flaps so that we can start accelerating the aircraft .
  • However , companies have a set altitude from which the flap retraction can start for example , 400 ft AAL (above aerodrome level).
  • As the gear is already retracted in the previous segment, the main source of drag is removed.
  • This makes it easier for the aircraft to climb at a higher climb gradient than segment 1. The climb gradient should not be less than 2.4%.
  • The main objective of the second segment is to clear the aircraft from the surrounding obstacles by maintaining the necessary climb gradient .
  • The second segment concludes at 400 ft AGL or the height decided by the company from where flap retraction can commence .

Segment 3

  • The third segment begins from 400 ft or flap retraction altitude set by the company .
  • The main objective of this segment is to accelerate the aircraft so that the flaps can be retracted step by step .
  • The reason we accelerate while retracting the flaps is because the stall speed will increase when we retract flaps .
  • Hence as the aircraft accelerates from take off safety speed (V2) to a higher speed that is minimum drag speed or best angle of climb speed so that the aircraft doesn’t get close to stall speed .
  • Once the flaps are retracted , we can set the thrust levers to maximum continuous thrust (MCT) from take off thrust .
  • In the Airbus 320, take off thrust can only be used continuously for a period of 05 mins on both engines and in case of an engine failure , it can be used continuously for 10 mins.
  • The segment however ends once the thrust lever are set to MCT and flaps are retracted .

Segment 4

  • The fourth segment starts once the trust levers are set to MCT and flaps are retracted.
  • The climb gradient for the last stage should not be less that 1.2%.
  • In the fourth segment, the airplane is climbed to above 1500 ft AAL (above aerodrome level) where the take off flight path ends.
  • In case of an engine failure , the pilot can make a decision to land at the departure aerodrome or go on further to an alternate airfield.

FACT FOR THE WEEK: This week we talk about the worlds largest passenger carrier aircraft , the Airbus A380. It is a double decker behemoth with four engines and has a cabin that can be occupied by more than 500 people .It first took flight in 2005 and was first delivered to Singapore Airlines in 2007.The Airbus A380 is also sometimes referred to as the SuperJumbo.

In 2019, it was however announced by Airbus that it would stop the production of the aircraft and the ones already in production will be delivered by 2021.The reason behind this was majority of the airlines preferring the new Airbus A350 in comparison to the A380 . The SuperJumbo will be definitely missed.

This is it for this weeks post. I hope you had a good read and got to learn something new as well . If you did , please don’t forget to likely share it with fellow aviators and aviation enthusiasts. Please feel free to comment for any questions or recommendations on the blog or further topics .Until next week , stay safe and stay healthy .



Need For Aircraft Lighting

Lighting in an aircraft is another very important parameter that contributes to the safety of the aircraft. If you are driving your car at night without any lights on a dark road ,there is a risk factor involved no matter how skilled a driver you might be.The same applies in aviation, pilots are taught emergency procedures for example a “lights out” landing that is landing without lights during their training in case a need arises for them to deal with it.

Hence it becomes incredibly important for us as aviators to understand the lights installed in our aircraft, the positioning of lights around the plane, their appropriate time of use and the most important that is what if they stop working?. In this post well be looking at the lights installed in an Airbus 320 as I am familiar with the aircraft but most lights in any aircraft always remain the same as a need for uniformity.

Types of Lights Installed

picture credits: Pinterest


  1. The strobe lights are three synchronized flashing lights that are located one on each wing and below the tail cone.
  2. The strobe lights are very bright and flashy and are basically used for identification in the sky.
  3. They are switched ON only when aligned with the runway for take off and switched OFF after exiting the runway at the destination aerodrome.
  4. The strobe lights are not used during taxi as it disrupts the pilots front view if there is an aircraft ahead of him with its strobe lights ON.
  5. In the Airbus 320, there is an AUTO position that enables the strobe lights to be OFF when the landing gear is compressed. This means that if the switch is in the AUTO position, the strobe lights would come ON once airborne and go OFF after landing.
Picture Credit:Aviation technic


  1. Navigation Lights are a compulsion for night flying.
  2. They are also known as position lights as they do not really help pilots in navigation but help determine the relative position of another aircraft in the air.
  3. The navigation lights consists of a steady green light on the right side/ starboard side of the wing and a steady red light on the left side/port side of the wing and a steady white light on the tail of the aircraft.
    • To help remember this, I was taught port wine is red in color.It means that red color light on the left/port side .
  4. To make sure these lights are visible through all directions on the ground and in flight, each light covers a certain angle to be visible according to the ICAO annex 6 that is “OPERATIONS OF AIRCRAFT”. The coverage angles are:
    • A red light projected above and below the horizontal plane on the left side so that it covers 110 degrees.
    • A green light projected above and below the horizontal plane on the right side so that it covers 110 degrees.
    • A white light projected above and below the horizontal plane rearward so that it covers an angle of 140 degrees.
  5. Therefore if you are flying and you see a steady white light ahead of you, it would mean that you are looking at the tail of another aircraft.
  6. The navigation lights help us determining the right of way as well.
    • Looking at figure A below, aircraft A can observe the can view the red light coming from the port side of aircraft B. This helps the pilot of aircraft A to understand that aircraft B has the right of way and it has to stop until clear of the aircraft B .


  1. Logo lights are generally mounted on the upper surface of the horizontal stabilizer and are used for company branding purposes as the lights point towards the company logo painted on the tail fin.
  2. However, the main purpose for the logo lights as all other lights is safety.
    • For example, when an aircraft is on approach, it becomes easier for the aircraft at the holding point to identify the aircraft with the logo light as it gives a 90 degree view.
  3. In the Airbus 320, the logo light is switched on with the navigational light and there is no separate switch for it.
pic credits:IVAO


  1. Wing lights are beam lights fitted on each side of the fuselage and provide lighting on the wing leading edges and on engine air intake.
  2. The main purpose of these lights are to help flight crew, cabin crew and ground personnel detect ice accretion.
  3. The wing lights are also to help detect wing or engine damage and are specially helpful during night operations because of their high beam.


  1. Beacon lights also known as anti collision lights are pulsating red lights fitted on the top and bottom of the fuselage.
  2. The beacon lights in the Airbus 320 are to be switched ON before the engine is started and therefore is included in the before start checklist.
  3. Based on point number 2, it becomes clear that the beacon light also makes the ground personnel aware that the engine is about to be started and the aircraft is ready for push back.
  4. The beacon lights are then switched OFF after the engines have been shut down after landing.
  5. An anti collision is to fitted in an aircraft during night operation to attract attention.
pic credits: QUORA


  1. Taxi light is a bright white light connected to the nose gear strut and goes off automatically once the landing gear is retracted.
  2. As the name suggest, it helps improve the visibility for pilots while taxying and is generally turned ON once the taxi clearance is obtained from ATC.
  3. In the Airbus 320, there is a nose switch that consist of a taxi and takeoff light instead of separate ones but to only make sure the taxi light is ON the toggle switch can be placed to the taxi position as shown below.


  1. The take off light is connected to the nose strut gear and goes off automatically once the landing gear is retracted and is similar to the taxi light but has a wider beam than the taxi light.
  2. The take off light is switched ON just as we line up on the runway and as mentioned above the take off light will go off once the landing gear is up, it is necessary to place the nose switch to the OFF position manually.
picture credit: aviation stack exchange


  1. The runway turn off lights are placed just below the taxi and take off lights on the nose strut gear.
  2. The runway turn off lights point slightly left and right in comparison to the taxi and take off lights as they assist the pilots during turns on taxiways and light up the taxiway and runway edges.
  3. The runway turn off lights are turned ON before taxying and turned OFF just after take off , similar to the taxi lights.


  1. Landing lights are high intensity lights that illuminate the runway surface for take off and landing.
  2. These lights can be mounted on the wing, fuselage on landing gear strut. In the Airbus 320, the landing lights are mounted in the leading edge of the wing and hence they extend and retract in the wing.
  3. The lights control panel doe not have an on and off switch for landing lights.Instead it has an three position switch consisting of extend, retract and off.
  4. The landing lights are extended as soon as possible the take off clearance is obtained and retracted at a certain altitude for example 10,000 ft.Similarly, on arrival the landing lights are extended again at 10,000 ft and retracted immediately after landing.
  5. During night operations, it is necessary that your aircraft is installed with one landing light.


  1. If there is a light that is not operating before take off, you need to check the minimum equipment list to check if the aircraft is safe to take off without the lights not available.
  2. However, there are redundancies to this as well as if your aircraft has 2 navigation light systems then if one fails the other one can be used for operation.

FACT OF THE WEEK: KLM, The Royal Air Transport Company, was founded on October 7, 1909. It is the oldest airline in the world and the oldest still flying under its name. Although the first flight didn’t take to the skies until May 1920, KLM has been a major part of the international airline landscape.Throughout its nearly hundred years of existence, KLM’s commitment to innovation has been constant.This doesn’t just apply to its fleet either. The airline has also proved pioneering with its use of social media, introducing the first social media-driven flight schedule.

This is it for this weeks post.I hope you liked it and gained some knowledge out of the post. If you did please don’t forget to share it with your fellow aviators. Please feel free to share your views and any advice or recommendations on topics you would like to read. Until next week, stay safe and stay healthy.



Image Credits: Key Tech

Need for Airport Marking


Imagine yourself piloting your favorite aircraft out of Chicago O’Hare International Airport on a very busy afternoon for the first time and you’ve just received your taxi clearance, as you start to taxi there are no clear airport markings to guide you to the runway.If I was in your seat, I would be the most confused person at that airport.

A lot of things in Aviation require uniformity and standardization just like we discussed in Freedoms Of The Air.Hence, Airport Markings help enhance safety which is of prime importance and aids pilots avoid confusion during critical stages of flight that are taxi, take off and landing.

Types of Airport Markings

Airport markings are categorized mainly into :

  • Runway Markings
  • Taxiway Markings
  • Hold Position Markings
  • Other Markings
  • Mandatory Instruction Marking
  • Information Marking

Runway Markings


  1. A runway designation marking shall be provided at the thresholds of a paved runway. However it is also recommended on unpaved runways (grass, dirt, sand runways).
  2. A runway designation marking shall consist of a two-digit number and on parallel runways shall be supplemented with a letter.
    • For example, Runway 21 and in case of parallel runway runway 21 L or 21 R.
  3. On a single runway, dual parallel runways and triple parallel runways the two-digit number shall be the whole number nearest the one-tenth of the magnetic North when viewed from the direction of approach.
    • If The actual direction of the runway could be 206 degrees however we round it to the nearest one tenth whole number that is 210 degrees and hence runway 21.
    • If The actual direction of the runway could be 202 degrees however we round it to the nearest one tenth whole number that is 210 degrees and hence runway 20.
  4. On four or more parallel runways, one set of adjacent runways shall be numbered to the nearest one-tenth magnetic azimuth and the other set of adjacent runways numbered to the next nearest one-tenth of the magnetic azimuth.
    • For example, if we have four parallel runways of direction 202, 204, 206, 208 degrees we name one set of them as 20 R and 20 L and the other set as 21 R and 21 L.
  5. When the above rule would give a single digit number, it shall be preceded by a zero.
    • This simply means that we do not write 8 L and 8 R for runway designation instead it is designated as 08 L and 08 R.
  6. In the case of parallel runways, each runway designation number shall be supplemented by a letter as follows, in the order shown from left to right when viewed from the direction of approach:
    • for two parallel runways: “L” “R”;
    • — for three parallel runways: “L” “C” “R”;
    • — for four parallel runways: “L” “R” “L” “R”;
    • — for five parallel runways: “L” “C” “R” “L” “R” or “L” “R” “L” “C” “R”; and
    • — for six parallel runways: “L” “C” “R” “L” “C” “R”.


  1. A runway centre line marking shall be located along the centre line of the runway between the runway designation markings.
    • However at the intersection of two or more runways , priority is given to the more important runway markings except for the runway side strip markings.
  2. A runway centre line marking shall consist of a line of uniformly spaced stripes and gaps. The length of a stripe plus a gap shall be not less than 50 m or more than 75 m. The length of each stripe shall be at least equal to the length of the gap or 30 m, whichever is greater.
    • For example, the centre line marking can be 30 m long with a gap of 20 m between the next marking which makes it a total of 50 m however this total cannot exceed 75 m.


  1. A threshold marking shall be provided at the threshold of a paved instrument runway and also on a paved non instrument runway with code number 3 or 4 and the runway is intended for use by international commercial air transport.
  2. The stripes of the threshold marking shall commence 6 m from the threshold.
  3. A runway threshold marking shall consist of a pattern of longitudinal stripes of uniform dimensions disposed symmetrically about the centre line of a runway.
    • The number of stripes in a threshold marking depends on the width of the runway.



  1. Where a threshold is displaced from the extremity of a runway or where the extremity of a runway is not square with the runway centre line, a transverse stripe should be added to the the threshold.
    • displaced threshold  is a runway threshold located at a point other than the physical beginning or end of the runway.
    • A displaced threshold occurs due to runway repairs, obstructions and this results in the displaced part not being used for landing.
  2. A transverse stripe should be 1.80 M or more wide in length.
  3. Where a runway threshold is permanently displaced, arrows conforming shall be provided on the portion of the runway before the displaced threshold.
  4. When a runway threshold is temporarily displaced from the normal position, it shall be marked as shown in the figure below and all markings prior to the displaced threshold shall be obscured (make something difficult to observe) except the runway centre line marking, which shall be converted to arrows.


  1. A touchdown zone marking shall be provided in the touchdown zone of a paved precision approach runway.
  2. A touchdown zone marking shall consist of pairs of rectangular markings symmetrical from the runway centre line with the number of such pairs related to the landing distance available.
  3. The pair of touchdown zone markings shall be spaced at a distance of 150 M beginning from the threshold.



  1. A runway side stripe marking shall be provided between the thresholds of a paved runway where there is a lack of contrast between the runway edges and the shoulders or the surrounding terrain.
    • The runway side stripes help in providing a visual contrast between runway edges and the abutting terrain which sometimes could be tough to differentiate.
  2. The stripes are continuous white located on each side of the runway.



  1. Taxiway centre line marking shall be provided on a paved taxiway, de-icing/anti-icing facility and apron so as to provide guidance between the runway centre line and where the aircraft stands.
  2. Taxiway centre line marking shall be at least 15 cm in width and a single continuous yellow line except where it intersects with a runway-holding position marking or an intermediate holding position marking.
    • It should be noted that although the taxiway centre line markings keep the aircraft along the centre they do no provide wing tip clearance.


  1. Enhanced Taxiway Centre Line Markings should be provided to denote the proximity of runway holding position.
  2. They should also be installed at runway/ taxiway intersections if possible.
  3. If provided they shall extend from the runway hold position to a distance of up to 47 M in the direction of travel away from the runway.

Hold Position Markings


  1. The hold position markings on the taxiway are indications for the aircraft to stop before entering the runway .
  2. Air Traffic Clearance is required for aircraft’s to enter the runway however while exiting the runway to a taxiway, air traffic clearance is not needed unless stated by the controller.
  3. The hold position markings consist of 4 yellow lines, that is , 2 solid and 2 dashed and 3 spaces at 0.15 M each.


  1. Intermediate hold position markings are used at an intersection of two taxiways.
  2. It shall be located across the taxiway at sufficient distance from the near edge of the intersecting taxiway to ensure safe clearance between taxiing aircraft.
  3. An intermediate holding position marking shall consist of a single broken line.
  4. When instructed by ATC to hold at a particular taxiway, the aircraft must stop and not cross the intermediate hold position marking until advised by ATC.


  1. The ILS (more on the instrument landing system in a separate post) hold position marking consist of two yellow solid lines spaced two feet apart connected by pairs of solid lines spaced ten feet apart extending across the width of the taxiway as shown below.
  2. A sign with an inscription in white on a red background is located adjacent to these hold position markings.

Other Markings


  1. A VOR aerodrome checkpoint marking shall be centred on the spot at which an aircraft is to be parked to receive the correct VOR signal.
  2. A VOR aerodrome checkpoint marking shall consist of a circle 6 m in diameter and have a line width of 15 cm as shown below.
  3. These markings should be preferably white in color with a black border to provide contrast and necessary to be different from the taxiway color markings.


  1. Aircraft stand markings should be provided for designated parking positions on a paved apron and on a deicing/ anti icing facility.
  2. These markings should include information like stand identification, lead in line, turning line, stop line and lead out line.
  3. The lead in line should include stand identification information (number and/or alphabet) that is visible for the reader from the cockpit.
  4. When two sets of aircraft stand markings are superimposed on each other then to make it understandable for the pilot the aircraft identification should also be added with the markings.
    • For example, 2a-A320 AND 2b-B737.


  1. Apron safety lines should be provided on a paved apron as required by parking configurations and ground facilities.
  2. These markings define the areas to be used by ground vehicles and other aircraft servicing equipment and provide safe separation from aircraft’s such as wing tip clearance.
  3. The apron safety lines should continuous in length and 10 CM in width.


  1. A road holding position marking should be provided at all road entrances to a runway.
  2. These markings shall be in accordance with local road traffic regulations.

Mandatory Instruction Marking

  1. Mandatory Instruction Marking assist in prevention of runway incursions. A mandatory sign should be installed and in places where it is impracticable to install signs , mandatory markings are used.
  2. The markings on taxiways shall be equally located along the taxiway centre line and holding side of the runway holding position marking.
  3. The marking should consist of an inscription in white on a red background.
    • For example, “No ENTRY” written in white on red background for a no entry marking.

Information Marking

  1. Information Markings are helpful when there are complex taxiway intersections and when information signs are not available.
  2. An information marking shall consist of :
    • An inscription in yellow upon a black background, where it replaces or supplements a location sign.
    • An inscription in black upon a yellow background, where it replaces or supplements a direction or destination sign.

FACT FOR THE WEEK: Beijing Daxing International Airport (PKX) is the largest international airport in the world.With its opening in September 2019, it spans over 7.5 million square feet and took over 11 billion dollars to build it.Based on the starfish theme, it ensures convenience and eco friendliness.It takes about a total of 8 minutes for passengers to travel from security to their gate. The first phase of the airport project is designed with a target of 72 million passengers, 2 million tons of cargo and mail and 620,000 aircraft movements in the long term.

This is it for this weeks post. I hope you liked it and learnt something new from it. Please don”t forget to share it with your fellow aviators.Until next week, stay safe and stay healthy.



It was a cold windy morning when the Wright Brothers took out their flying machine from their sheds at the Kill Devils hills in North Carolina on the 17th of December 1903. At exactly 10:35 am, Orville Wright flew a distance of 120 feet and was airborne for approximately 12 seconds.The Wright Brothers used their successful glider to build this flying machine which they named the “FLYER“.However they had to increase the wing area considerably to install the engine and the propellers.

Orville Wright on the control of the FLYER as Wilbur Wright assists him . Credit:DAVID McCULLOUGH’S “THE WRIGHT BROTHERS”

If you are interested in knowing more about the Wright Brothers, I would highly recommend you to read “THE WRIGHT BROTHERS” by DAVID McCULLOUGH or visit https://airandspace.si.edu/exhibitions/wright-brothers/online/fly/1903/

The “FLYER” certainly turned out to be one of the inventions of the century that led to the evolution of the aviation industry and the diversification of airplanes.This leads us to categorizing several airplanes and differentiating them further into various classes.

Please note that this post will not be covering information related to the ratings associated with different classes and please do not get confused between classes and type and their related ratings. I will cover the subject related to class and type ratings in a separate post.


According to the FAA, an aircraft category refers to the intended use or operating limits of a particular group of aircraft.The FAA then differentiates aircraft category by their characteristics and physical properties which are broken down with respect to the Certification of Airmen or with respect to Certification of Aircraft.

Certification Of Airmen

For purposes of ratings on a pilot certificate, there are SEVEN different aircraft categories:

1.AIRPLANE: An engine driven fixed wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.In level flight, there are four forces acting on an airplane. the weight of it is counteracted by the lift produced by the wing and the drag is counteracted by the thrust developed from the engines.

2. ROTORCRAFT: It denotes a heavier than air aircraft that supports the dynamic reaction of the air against its rotors on a vertical axis.The rotor generates its lift by using the rotor blades.

3. POWERED LIFT: A heavier-than-air aircraft capable of vertical take-off, vertical landing, and low-speed flight, which depends principally on engine-driven lift devices or engine thrust for the lift during these flight regimes and on non-rotating aerofoil for lift during horizontal flight.They are a combination of an airplane for horizontal movement and rotorcraft for take off and landing.

4.GLIDER: A non power (without engines) driven heavier than air aircraft that derives its lift chiefly from aerodynamic reactions on surfaces that remain fixed under given conditions of flight.A paper plane made in school is the simplest example of a glider.The most obvious difference between a glider and an airplane is that the later flies without an engine and hence the drag created has to be counteracted by the lift in comparison to an airplane where the engine balances the drag.

5.LIGHTER THAN AIR: Any aircraft chiefly supported by its buoyancy in the air.These aircraft contain a sufficient volume of gas that is lighter than air which when heated creates the necessary lift required.

6.POWERED PARACHUTE: It is a powered aircraft comprised of a semi rigid or a flexible wing so that the wing is not in position until the aircraft is in motion.The fuselage consists of an engine, a seat and is attached to the aircraft landing gear.The thrust from the engine pushes the cart forward forces air into the leading edge of the wing resulting in an inflated and pressurized wing that helps to fly, as it keeps its airfoil shape.

Certification Of Aircraft

With respect to certification of aircraft, it is given in terms of intended use or operating limitations.According to the FAA, they are categorized as follows:

  • TRANSPORT: Multi-engine airplanes with more than 19 seats or a maximum takeoff weight greater than 19,000 lbs must be certificated in the transport category.
  • NORMAL: Aircraft with a maximum take off weight of 12,500 lbs (5700 kgs) and a seating capacity of 09 passenger seats.
  • UTILITY: Aircraft limited to limited acrobatic operations with a maximum take off weight of 12,500 lbs (5700 kgs) and passenger seating capacity of 09 seats.
  • ACROBATIC: Aircraft with no flight maneuver restrictions other than posted by flight tests.They have a maximum take off mass of 12,500 lbs (5700 kgs) and a passenger seating capacity of 09.
  • RESTRICTED: Operation of restricted category aircraft is restricted to special purposes identified in the applicable type design.These special purpose operations can be agricultural work, aerial advertising, forest surveying etc
  • LIMITED: A limited category special airworthiness certificate is issued to operate surplus military aircraft that have been converted to civilian use under guidelines mentioned by the regulatory.
  • PROVISIONAL: A provisional category special airworthiness certificate is issued to conduct special purpose operations of aircraft with provisional type certificates.Class I certificates may be issued for all categories and have a duration of 24 months.  Class II certificates are issued for transport category aircraft only and have a duration of 12 months.


Aircraft class relates to a broader grouping of aircraft having similar characteristics of propulsion, flight and landing.The categories of aircraft are therefore broken down into further classes.As mentioned earlier, the categories of aircraft are divided into certification of airmen and certification of aircraft.Both the categories will have their classes but we will be discussing the classes based on the category of airmen.

1.AIRPLANE: The airplane category is divided into 4 classes:


2.ROTORCRAFT: The rotorcraft category is divided into 2 classes:


3.POWERED LIFT:The powered lift category is not divided into classes.

4.GLIDER: The glider category is not divided into classes.

5.LIGHTER THAN AIR: The LTA aircraft are divided into 2 classes:


6.POWERED PARACHUTE: The category is divided into 2 classes:

  • Powered Parachute Land
  • Powered Parachute Sea

7.WEIGHT -SHIFT-CONTROL:The category is divided into 2 classes:

  • Weight shift control Land
  • Weight shift control Sea
Categories and Class of Aircraft

Every week we discuss a fun fact about aviation and this week we talk about Amelia Earhart.

FACT:Amelia Earhart became the first female aviator to fly solo across the Atlantic Ocean on the 20th OF May 1932.Earhart set off from Newfoundland, Canada in her single engine Lockheed Vega 5B. After a flight lasting 14 hours 56 minutes during which she contended off several problems, Earhart successfully landed in Northern Ireland. Earhart’s accomplishments in the field of aviation inspired a generation of female aviators to join the air force and continues to inspire female pilots around the globe #GIRLPOWER.

That is it for this week everyone.I hope you gained some knowledge from this weeks post and liked it as well.Please don’t forget to like and share it with your fellow aviators. I would love to know which category of aircraft do you fly or would love to fly in the comments below.Until next time stay safe and stay healthy.




The great Dalai Lama once said,“Once a year, go someplace you’ve never been before.”

The Second World War had a major effect on the strategic use of the aeroplanes for the movement of humans and cargo and thus laying the foundations of air travel .The question of commercial rights was raised for airlines of one country to fly in the other or through their territories.

Through the Chicago Convention held in 1944, the delegates of 52 nations agreed on the development of various policies for the commencement of civil aviation in a safe and orderly manner. One of the policies developers for commercial rights was ‘Freedoms Of The Air’

According to the Manual of Regulation of International Air Transport, the International Civil Aviation Organization (ICAO) states a total of 9 Freedom of Air however the ICAO characterises the freedoms beyond the 5th freedom as ‘so called’ because only the first 5 freedoms have been officially recognised as such by international treaty.

So hence on today’s blog we’ll be discussing the first 5 freedoms of air.

The 5 freedoms are further divided into 2 categories

1.Technical or Transit Freedoms Of The Air

The first and second freedom of the air are included in this.

First Freedom of the Air – According to ICAO, the right or privilege, in respect of scheduled international air services, granted by one State to another State or States to fly across its territory without landing (also known as a First Freedom Right).

Explanation: It simply means that an airline is granted the rights to fly over another country without landing in it. For example, a flight from New Delhi to Melbourne would be given the rights to fly over Singapore or Malaysia and other countries on route . However obvious this may sound, technically each country owns the airspace above it and charges the airlines a fee to fly in that particular airspace also know an overflight fees .

To know more about overflight fees charged by India you can visit the following link:https://www.aai.aero/sites/default/files/Airport-Charges-2015-16.pdf

Second Freedom of the Air – the right or privilege, in respect of scheduled international air services, granted by one State to another State or States to land in its territory for non-traffic purposes (also known as a Second Freedom Right).

Explanation:The Second Freedom allows airlines the right to make a ‘technical stop’ at a country on route if required. For example, we take the same flight from Delhi to Melbourne and instead of flying over Singapore we land at the airport for refueling or other technical purposes and take off from Singapore for Melbourne.


2. Commercial Freedoms Of The Air.

The third, fourth and fifth freedom of the air are included in this.

Third Freedom of The Air – the right or privilege, in respect of scheduled international air services, granted by one State to another State to put down, in the territory of the first State, traffic coming from the home State of the carrier (also known as a Third Freedom Right).

Explanation:The Third Freedom is granted to almost all International Airlines.It gives the right to airlines to fly passengers and cargo from ones own country to another.For example, Air India can fly its passengers and cargo from Delhi to Singapore.

Fourth Freedom of The Air – the right or privilege, in respect of scheduled international air services, granted by one State to another State to take on, in the territory of the first State, traffic destined for the home State of the carrier (also known as a Fourth Freedom Right).

Explanation:The Fourth Freedom goes hand in hand with the above mentioned Third Freedom. It allows the airline to fly passengers and cargo from another country to its own country. For example, Air India would be allowed to take passengers and cargo from Singapore back to Delhi.

Fifth Freedom of The Air – the right or privilege, in respect of scheduled international air services, granted by one State to another State to put down and to take on, in the territory of the first State, traffic coming from or destined to a third State (also known as a Fifth Freedom Right).

Explanation:The Fifth Freedom offers airlines to fly passengers and cargo from one country to the second country, pick up more passengers or put down passengers and depart for the third country. For example, Air India flying from Delhi to Singapore and allowing more passengers to board at Singapore before departing for Melbourne.The Fifth and the Second freedom are very similar however Fifth Freedom allowing airliners more opportunity commercially.


As mentioned above, the first five freedoms we were the ones agreed in the freedoms treaty but the freedoms sixth to ninth are equally interesting and I would request you to have a quick look at them as well . You can find them at https://www.icao.int/Pages/freedomsAir.aspx.

At the end of every blog post I have decided to share a fun fact about Aviation in general.

FACT: On the 8th of August 1908, Wilbur Wright successfully completed his first public flight at Le Mans in France as the Wright Brothers showed off their flying machine. 08/08/1908, a date fairly easy to remember, isn’t it?

I hope this blog helped you in some way and please don’t forget to like and share it with your fellow aviators.If you want a specific topic to be addressed on the blog you can always email me at aviatorsguide08@gmail.com. Until next week , stay safe and stay healthy .