Infamous Dogfights of World War I & II

Infamous Dogfights of World War I & II


Dogfight of world war 1 ans world war 2

For most of you American Football fanatics out there, Dogfighting is very much like a combination of various offensive and defensive plays that are formulated during gameplay. Just as a receiver or a pass rusher is asked to run a route, it is with that same ideology that is applied to an aircraft in pursuit of enemies or in pursuit of protecting their fellow comrades. 

Dogfighting isn't duck soup

Don't take my word for it but take a look at history itself. We've witnessed several accounts of dogfighting over a span of 100 years! Yes, ten decades of consummate aerial dominance and aerodynamical prowess. The first ever documented aerial warfare had taken place in Mexico in the year 1913, during the Mexican Revolution. Two remarkable pilots who went by the names of Dean Ivan Lamb and Phil Rader had carried out their aerial dispute with a volley of bullets but surprisingly, neither one of them wanted to kill each other so they decided to intentionally miss their fellow targets. I wonder why? Well, one thing's for sure; we have sure come a long way into understanding the concept of dogfighting. Here's a look at some of the most paramount dogfighting battles of the century:

Battle Of Cer (Balkan Wars)

Most aviation pioneers knew the first dogfight had taken place during the Mexican Revolution but the dawn of Dogfighting had approached humanity as a whole in the backdrop of World War I. The first aerial dogfight had taken place during the Balkan Wars over Mišar in Western Serbia. Although this battle hadn't lasted very long, it played a significant role in impacting the world of aviation. Sergeant Miodrag Tomić, a Serbian/Yugoslavian pilot from the 1st Danube Division, was flying his Blériot and was on the verge of completing a reconnaissance mission when he ended up coming face-to-face with an Austrian-Hungarian enemy pilot. Although the initial confrontation showed no signs of animosity within each other, the enemy pilot had decided to pull a pistol and fire at Miodrag. Miodrag then fired back with his own pistol and thus, in the midst of it all, the world's first dogfight had transpired. Miodrag had escaped from this surprise attack but more importantly, within weeks, this iconic confrontation led to the addition of machine guns on top of the Serbian aircraft.

Dogfight of world war 1 ans world war 2

At the cockpit: Sergeant Miodrag Tomić (Left) and Lt. Milutin Mihajlović (Right) aboard the Blériot XI 'STORM'


Spanish Civil War (Rise of the Wingman Tactic)


Dogfight of world war 1 ans world war 2
A Spanish Republican soldier as seen here talks to a journalist. We can see Mr Ernest Hemingway at the back (back facing the camera) who served as a war correspondent during the Spanish Civil War.

During the years 1936 to 1939, Spain had seen a rise in confrontations between the Spanish Republicans and the Spanish Nationalists/Communists. The series of events had led to a full-fledged battle of the aerial aces. The advent of the Spanish Civil War had given birth to a new air combat strategy. Werner Mölders, a Nazi Luftwaffe pilot who had consociated himself with the Condor Legion (Army and Air Force unit of Nazi Germany who sided with the Spanish Nationalists) had come up with the idea of adding a Wingman to the dogfighting formation. Wingmen were imperative in defending and assisting the lead Aircraft during the war. Werner had also suggested that these two aircraft must be kept at a tolerable distance from each other instead of using conventional tight 'V' formations. Werner had also incorporated a system of pilot training during the night! The amalgamation of all these new tactics had been instilled in the Messerschmitt Bf 109 Luftwaffe Aircraft. It is with these very BF 109 Aircraft that helped annihilate the Spanish Republicans' Spitfires and Hurricanes. 


Dogfight of world war 1 ans world war 2
                                                   
Messerschmitt Bf 109 Aircraft


Dogfight of world war 1 ans world war 2

Werner Mölders (Left)


Battle of Britain (Domino effect of Dogfighting during World War II)


Dogfight of world war 1 ans world war 2


Right after the Spanish Civil War, World War II had taken over and dogfighting was prevalent. Nazi Germany's Luftwaffe constantly provoked the United Kingdom which in turn led to the retaliation by the Royal Air Force. This large-scale military campaign had led to the 'Battle of Britain' that consisted of the following belligerents: United Kingdom (Allies), Canada (Allies), Germany (Axis), and Italy (Axis). 
This battle had been a platform for inculcating and developing numerous tactical innovations in order to achieve the zenith of supreme dogfighting prowess. The German Luftwaffe had come up with various aerial formations such as the Rotte (Pack) formation wherein the Rottenführer (Leader) is followed by the Rottenhund (Pack Dogs) at an approximate distance of 200 meters. This allowed effective formation assessment by the pilots and avoided any time delays. It rather focussed on maintaining a close vigilance on a fellow pilot's blind spots. 
The Royal Air Force, on the other hand, had used a Vic Formation tactic in order to keep a tight formation of 4 sections each. Although the Luftwaffe did call it the Idiotenreihen (“rows of idiots”), the formation is used even to this day! The RAF eventually changed the formation to a tight finger-four formation similar to the one used by the Luftwaffe.


Dogfight of world war 1 ans world war 2

Vic Formation used by the Royal Air Force



Dogfight of world war 1 ans world war 2

Battle of the Aces! Spitfire and Heinkel He 111 go head-to-head.
(This picture was captured in 1940 during the Battle of Britain.)



Dogfight of world war 1 ans world war 2

As seen here, Group Captain Sir Douglas Bader sits on his beloved Hurricane. Bader was known for his Aerial Supremacy during the Battle of Britain. The movie 'Reach For The Sky' was a biographical film made in honour of Douglas Bader.


Pearl Harbour (The Battle of Midway and the rise of the 'Thach Weave' manoeuver)

After the attack on Pearl Harbour by the Imperial Japanese Navy Air Service, the United States had directly entered into World War II. This retaliation had given rise to a whole new series of Aerial Dogfights. One such series included the battle between Mitsubishi A6M "Zero" aircraft and the Grumman F4F Wildcats. This dogfight had taken place in 1942 during The Battle of Midway in the Pacific Ocean and its islands. Between the two aircraft, Zeros were considered to be more aerodynamically superior compared to the WildcatsLieutenant Commander John S. "Jimmy" Thach was one of the first pioneers to come up with a tactical plan in order to surpass Japan's Zeros. He ended up coming with a tactic called the Thach Weave with the help of matchsticks on a table. Hence, this tactic was consequently applied in the war. Although most of them deemed it to be less probable, the outcome was beneficial. Most of these Zeros were capable of flying at 295 mph and hence, the tight turns would augment the inefficiencies of the aircraft's manoeuvrability.  This allowed the Wildcats to execute the Thach Weave formation and leave the enemy plane vulnerable to attacks.

Dogfight of world war 1 ans world war 2

Grumman F4F Wildcat in action!

Dogfight of world war 1 ans world war 2

Mitsubishi A6M Zeros in action!

Dogfight of world war 1 ans world war 2

A standard Thach Weave Formation carried out as shown in the figure above.
(Pink denotes Japan's Zeros and Blue denotes the Wildcats)



And thus concludes some of the iconic dogfights that had taken place in the midst of World War I and II. If you'd like to check out more about dogfighting, then I'd suggest you click on the links below:






Until then, stay Turbocharged!

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Bell Boeing V22 Osprey

Bell Boeing V22 Osprey

Bell Boeing V-22 Osprey

© Chief Petty Officer Joe Kane (U.S. Navy)

Operation Eagle Claw - A rescue mission in the 1980s for 52 embassy staff held captive in Iran had failed when a chopper struck a USAF C-130 killing eight servicemen. This mission might be one of those missions, whose failure led to the birth of the most unique aircraft in the aviation industry - Bell Boeing V-22 Osprey.

Design : 


The Bell Boeing V-22 Osprey is the world's first tiltrotor aircraft. It has one three-bladed proprietor, turboprop engine, and transmission nacelle mounted on each wingtip. It might be the first of its kind which has both VTOL (Vertical Takeoff and Landing) and STOL (Short Takeoff and Landing) capabilities. This means that it takes takeoff like a fixed-wing aircraft with a small runway or like a helicopter if no runway is available at all. If it operates like a helicopter, the nacelles are in vertical position and the rotors are in a horizontal position. Once the aircraft takes off, the nacelles tilt forward 90° in 12 seconds for horizontal flight. This technique helps the V-22 Osprey to be a more fuel efficient and higher speed turboprop aircraft. With empty payload, it can fly up to 2100 nautical miles (ferry flight) and with payload, it can fly up to 1100 nautical miles (operational range). The Osprey is powered by 2 Rolls-Royce AE 1107C engines which can power the proprietors both through the wings and driveshaft.



The Osprey has a modern glass cockpit with night-vision-goggle-compatibility and multi-function displays that display the navigation and vital system information. The flight controls consist of a central control stick, thrust control levers, and rudder pedals. The control stick can function like a cyclic control during helicopter mode and also a traditional airplane control stick during fixed-wing aircraft mode! The V-22 Osprey has triple-redundant fly-by-wire flight control systems with FADEC (full-authority digital engine control) systems. There are three flight control computers, three navigation systems, three hydraulic systems, and four generators. The Osprey can safely fly with just one of each of the systems. The Osprey has a Cockpit Management System (CMS) which allows for autopilot functions that fly the aircraft from 50ft without any manual interaction. If we talk about how fast it goes, the Osprey cruises within a speed range of 170 to 240 knots and flies at a speed of 170 knots during an instrument approach to during holding patterns. The Osprey’s fuselage is not pressurized. If the aircraft is flown above 10,000ft, the crew is required to wear oxygen masks

© Senior Airman Julianne Showalter, U.S. Air Force

© Airman 1st Class Russell Scalf
Check Bell Boeing V22 Osprey specifications here!

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Suggested article: What is METAR and how to decode it?

What is METAR and how to decode it?

What is METAR and how to decode it?

What is METAR?

In Aviation, weather plays a very important role in day to day operations. In fact, a pilot needs to check whether several times during the different phases of flight. Before the airplane is ready to leave the gate, he/she always checks the weather at the arriving and departing aerodrome in the pre-flight briefing. If they feel that the weather at and around the airport is not suitable for flying, they might decide not to operate the flight or even divert to their alternate aerodrome.
In aviation, the weather information of an aerodrome is broadcasted in a report called METAR (Meteorological Aerodrome Report). They are published in a fixed format which is common all over the world.

METAR is a string of abbreviations which denote various weather conditions around the aerodrome. You can learn all the METAR Abbreviations by referring to this document. With the help of this document, let us take an example of METAR of Chennai International Airport and decode it!

Eg: VOMM 131530Z 16006KT 4000 HZ SCT020 FEW025TCU BKN100 30/23 Q1009 NOSIG


Abbreviation
Indicates
Meaning
VOMM
ICAO Code
Chennai Intl Airport
131530Z
Date and Time
13 - Day of the month. 1530Z - Time of observation.
16006KT
Wind Direction
Wind direction is from 160 deg at 06 knots (denoted in Meters per second in Metric)
4000
Visibility
Prevailing Visibility at the airport is 4 km or 4000m
HZ
Weather Condition
Haze
SCT020
Cloud condition
Scattered clouds present at 2000ft
FEW025TCU
Cloud Condition
Few clouds present at 2500ft in towering cumulus form
BKN100
Cloud Condition
Broken clouds present at 10,000ft above aerodrome level
30/23
Temperature and Dew Point
The temperature at the airport is 30 deg. Dewpoint is 23 deg
Q1009
Sea Level Pressure / Barometer setting QNH
1009 hectopascals ( denoted in inch of Mercury - inHg in FAA)
NOSIG
Remark
No significant change in weather for the next 2 hours

SPECI Reports: 

A SPECI is a special report of meteorological weather conditions which is issued when one or more conditions match the specified criteria significant to aviation operations. It is also used to identify reports which are recorded ten minutes after an improvement to the SPECI conditions.

SPECI Example: SPECI VMMC 242341Z 10010KT 3500N VCSH FEW010 SCT018 BKN070 28/26 Q1004 TEMPO 5000 SHRA

SPECI Criteria : 



Element
Criteria
Wind Direction
Direction changed by 30 deg when the average speed is 20 KT or more.
Wind Speed
Speed changed by 10 KT when the average speed is 30 KT or more
Wind Gusts
Gust speed exceeds by 10 KT than the last reported speed
Visibility
When prevailing visibility is below the minimum operable limit of the aerodrome
Weather Phenomenon
When any of the weather phenomena such as thunderstorms, hail storms, sandstorms, dust storms, etc are reported in high intensity.
Cloud
When cloud cover (broken or overcast) is below the minimum operable limit of the aerodrome.
Temperature
When temperature increases or decreases by 5 deg since the last reported temperature
Pressure
When pressure increases or decreases by 2 hPa since the last reported pressure
Remarks
If the pilots repeatedly  report wind shear or other such weather phenomena

What is Black box?

What is Black box?

What is Black box?


Accidents such as the Charkhi Dadri mid-air collision, Air India Express flight 812, Air France 447, Korean Air flight 007 were some of the air crashes which were an eye opener for the Aviation industry. Investigators were able to find the cause of these accidents because of the data they found within the black boxes. A Black box is a recording device installed on most modern aircraft as well as mandated by authorities worldwide. They are expensive and cost between $10000 to $15000 each. They record several unique performance parameters throughout the flight which is then stored on solid state drives as well as other high capacity memory devices.

What’s inside the Black Box? 

While a black box has several precision instruments in it alongside some very clever design components, the two major instruments that are of the highest priority to investigators are:

1. Flight Data Recorder (FDR), and
2. Cockpit Voice Recorder (CVR)

1. Flight Data Recorder : 


A Flight Data Recorder is one of the first devices that is searched for and consequently secured after an accident. It records various significant performance parameters such as airspeed, altitude, heading, pitch, etc. A modern FDR records a minimum of 88 parameters which is also the minimum requirement under the  United States Federal Regulations. When data is retrieved from an FDR, the investigators can render the data that reconstructs the flight prior to the crash.  An FDR records up to 25 hours of continuous data and has an impact tolerance off 3400Gs. It can resist up to 1100 Deg Celsius and a water pressure up to 20,000ft.

A sample of FDR Data: Click Here

2. Cockpit Voice Recorder : 

Cockpit Voice Recorder

A Cockpit Voice Recorder (CVR) is used to record the audio inside the cockpit. The audio is usually captured through the microphones of the pilot’s headsets along with the microphones present in the flight deck. A regular CVR is able to record 4 channels of audio data for 2 hours.

Modern-day block boxes store data in Solid State memory devices and use digital recording techniques which make them resistant to moisture, vibration, and shock. They also include a standby power source for redundancy should the aircraft lose its own electrical power supply
The black box is accompanied by an underwater location beacon (ULB) and an emergency location transmitter (ELT) that provide a consistent signal to special receivers which eventually help pinpoint their location after an accident. The beacon can ping up to 30 days with the available power source available inside.
Underwater Location Beacon

Why is the Black box not visually painted in a black color?


The color of the Black box isn't actually black as the name would suggest. The Black box is actually painted in Orange color. The reason for a majority of the vivid orange color on the outside is to aid its detection from a distance. The color is better visible against the dark color of the burnt residue in an accident which makes it easier to spot.

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Suggested article: What is MRO, Line maintenance & Base maintenance?

MRO, Line Maintenance and Base Maintenance

MRO, Line Maintenance and Base Maintenance

MRO, Line Maintenance and Base Maintenance

MRO, Line Maintenance and Base Maintenance

Maintenance is one of the pillars that supports the entire aviation industry. Similar to how all machines require time to time maintenance, even aircraft require regular maintenance to maintain its airworthiness. Airworthiness is the quality check of various aircraft components and structure which determine its suitability for a safe flight. A certificate of airworthiness is conferred from a local governing aviation authority and is maintained by performing the required regular maintenance checks.

MRO, Line Maintenance and Base Maintenance

Maintenance, Repair, and Overhaul (MRO)

The Maintenance, Repair, Overhaul refers to organizations involved with the maintenance, repair, and overhaul of aircraft and associated systems and components and continues throughout the life of an aircraft from its initial entry into service through to its ultimate disposal.
The MRO organizations carry out  activities include the following activities:

  • Maintenance that relates to the process of preserving a complete aircraft in an airworthy condition.
  • Repair or replacement of damaged items that are inoperable
  • The overhaul that relates to reconditioning a system that has degradation in performance or strength.

Line Maintenance

Line Maintenance comprises of any maintenance that is carried out before the flight to ensure that
the aircraft is fit for the flight. The aircraft is visually inspected and its aircraft
logbook is checked for various entries relating to system problems, failures or other maintenance. It includes troubleshooting, defect rectification and component replacement of an aircraft and requires 2 man hours to complete the checks.

MRO, Line Maintenance and Base Maintenance

Base Maintenance 

Base Maintenance is carried out in a hanger and covers a series of checks and MRO activities. Every airline has different maintenance schedules and procedures that relate to their specific aircraft. Base maintenance is classified into 4 categories each denoted by a letter.

A Check: Carried out after every 100 flight hours.
B Check: Carried out after 2 months or 500-600 flight hours. It involves a more thorough check than A Check.
C Check: It involves a very comprehensive and thorough check. Carried out after every 2 years. Some operators carry out a "3C Check" which is a subcategory of C Check and includes light structural maintenance, corrosion check, replacement of seats, etc.
D Check: It is the most comprehensive check-in Base Maintenance. Carried out after every 6 years and can take up to 2 months to complete. An aircraft on average undergo 2 to 3 D Checks before it retires.

Unscheduled Maintenance and Aircraft Recovery 

If there is a need to repair an aircraft is stranded at an airport away from the base airport, the operator may declare the aircraft as “Aircraft on Ground”. Repair to the damaged aircraft may require a specialist team to travel on site and carry out the repair.

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Suggested article: What are Visual Flight Rules (VFR)?

Visual Flight Rules

Visual Flight Rules

Visual flight rulea


If you are a true aviation enthusiast then at one or the other point in your life you must have come across the term visual flight rules (VFR). If you have ever got a chance to fly in an aircraft you must have popped out of the window to see that what does the pilot sees? If not I will tell you that it is just awesome to gaze out that window and the huge huge clear blue sky all around. It's not blue all the time though when you get those shaking cabin rides.

For the sake of this discussion, we would assume that the sky outside the aircraft is blue. Being a passenger you would always think that it's so clear outside, the pilot must be in full control of this craft! But is it correct? Flying around 150-200 pure souls is not that easy. Though the sky is damn clear still there are a set of rules which the pilot have to follow while flying the aircraft. These set of rules and regulations are called Visual Flight Rules. VFR may formally be defined as the set of rules that the pilot have to follow while flying the aircraft when the weather conditions under certain minimum control limits set up by the governing body of that airfield.

The minimum control limits of weather conditions are called as Visual Meteorological Conditions. VMC may formally be defined as a set of weather conditions which are clear enough so that the pilot is able to distinguish between the clouds and any obstruction that may lie on the flight path. This VMC vary in various factors such as what type of aircraft are we talking about,? the airfield over which we are flying? whether we are flying in night or day? etc...

Visual meteorological conditions
Visual meteorological conditions

Let us take an example of VMC conditions as laid down by the United Kingdom government.


Now as we have got an insight into what are the visual meteorological conditions lets take our discussion back to visual flight rules. If the VMC are satisfied then the pilot has to follow VFR while flying the aircraft. If the conditions of VMC are satisfied then the pilot need not fly the aircraft as per ATC directions he/she can fly the aircraft according to his decision-making abilities but still, a transponder is required on the aircraft so that ATC can get the exact location of the aircraft at any instance whenever required.

What are Visual Flight Rules?

As in the case of VMC the visual flight rules are also dependent on various aspects such as the type of aircraft being flown, time of flight etc. All these factors are studied by the federal agency of the country over which the respective airfield lies and VFR are decided accordingly.

For example let us consider that an aircraft is flying over XYZ city where the governing body is ABC , the VMC as prescribed by ABC are that in the case of day flying between 800 hours to 1600 hours above 700 ft from ground or sea with a clear visibility of 5 km then these conditions may be taken as the minima for VMC and the pilot has the right to fly as a VFR with the consent of ATC under which he/she has to maintain a distance of at least 600 m from clouds and to take decisions as per the spot and decide policy in which the pilot spots any obstruction and adjust the flight path accordingly.

What are VMC conditions are not fulfilled?

In case of a condition when the VMC is not being fulfilled then IFC can be carried out. IFC is defined as Instrumental flight control for which another weather and meteorological conditions by the name of Instrumental Meteorological conditions are defined.


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Suggested article: Can an aircraft overspeed?




Can an aircraft overspeed?

Can an aircraft overspeed?

Aircraft overspeed Airbus A350

An incident took place with a Ryanair flight EL-EBW on Jan 2017. It was Boeing 737-8AS. As the aircraft was descending into a high altitude jet stream, there was an associated increase or rise in the headwind which caused the aircraft to overspeed. In order, to control the aircraft's overspeeding, the pilot switched the autopilot to manual, which eventually led to a nose-up pitch input at the control column. This incident caused few crew members to collapse and undergo severe injury.

Overspeed is that situation or condition of an aircraft in which it's engine is made or forced to operate beyond it's designed limits. However, the consequences that arise when a particular engine is made to run too fast vary depending upon the engine type and the model used. Other factors that determine the type of failure or consequence on the engine on overspeeding are judged mainly by the duration of the overspeeding condition and the speed reached. Few engines can be affected severely by reducing their engine life or cause catastrophic failures even by momentary overspeeding. The engine overspeed is measured in revolutions per minute.

HOW DOES IT HAPPEN?

Overspeed conditions arise when an aircraft exceeds the Never Exceed speed or the Vne of the airframe. Although the speed level doesn't bother the engines used in an aircraft, it is preferable for the pilot to stay within the indicated limits.

An aerodynamic phenomenon, commonly known as Mach tuck, which is too involved to get into in a forum is experienced by Jets and speeding aircraft. But generally, it is observed that it's the aerodynamic regime that results to uncontrollability of the aircraft after the published speed has been exceeded, usually with a fraction or percent of margin.

Induced drag, parasite drag, skin friction drag and many other kinds of drag are created on an airframe as the aircraft flies through the atmosphere, few of them resulting to the point of uncontrollability or complete or partial failure when exceeded. These values are usually determined by the manufacturers of the aircraft. Regardless of being an aerodynamic failure or a structural failure, it is not often published in the POH when the speed is exceeded. To avoid these failures it is best expected for the pilot to stay within the published limits.

EPR or N1 and the EGT temperature present on the engine stack are used to monitor the overspeed factor of an engine.The limits for various flight conditions like take-off and cruise is provided in the POH, which includes the temperature and density altitude at standard conditions.

Aircraft overspeed


PREVENTION OF FAILURE FROM OVERSPEEDING

In most aircraft, designed to avoid overspeeding failures a governor or a regulator is often used to make the overspeeding condition impossible or very less likely to be attained and hence giving no chance for failure due to the same reason. For instance, Some of the aircraft are embedded with constant - speed units which have the capability to change the propeller pitch without any human intervention. This helps the aircraft or the engine to run at the optimal speed.

Aircraft overspeed prevention


Overspeed condition

In propeller driven aircrafts, overspeed conditions are attained when the propeller which is ordinarily connected directly to the engine of the aircraft, has been made or forced to operate at a very fast pace with high-speed airflow during the aircraft performing dive, or in case it moves to a flat pitch in cruising flight due to failure of the governor or any feathering failure from/in the engine.

Coming to jet driven aircraft, overspeed conditions are attained when the maximum operating speed has been exceeded by the axial compressor of the engine. As a result, we notice mechanical failures of the turbine blades or flameouts or even complete destruction of the engine.




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Suggested article: How the aircraft hydraulic system works?

Aircraft Fan Drive Gear System

Fan Drive Gear System

A very commonly boasted off phrase by aircraft engine manufacturers these days is, "The Ultra High By-Pass Ratio". Have you ever wondered what do they mean by this ultra-high bypass ratio? What is the reason behind the ultra-high bypass ratio?

Aircraft Fan Drive Gear System

Before starting the discussion about the ultra-high bypass ratio and the fan drive gear system let us have a brief introduction to the basic composition and working of an aircraft engine. The engine consists of basically five sections
  1. Fan
  2. Compressor ( low pressure and high pressure)
  3. Diffusion and combustion chamber
  4. Turbine ( low pressure and high pressure)
  5. Exhaust Nozzle

working of the aircraft jet engine


The ambient air is sucked into the engine by the fan, the air coming inside from the fan is divided into two parts the bypass air and the secondary air. As it can be seen from the image the air entering the core engine is called the secondary air and the part of the air that does not enter the core engine and goes through the engine is called the bypass air. The air which enters the core engine is initially compressed in the compressor stage of the aircraft engine which increases the pressure and temperature of the air. After compression, the air is sent to the diffusion and combustion chamber where the compressed air is burnt along with air and fuel mixture which further increases the pressure and temperature values to a very high value. After this, the high pressure and temperature air is sent in the turbine section where high pressure and temperature air is expanded which increases the velocity of air to very high values at the expense of its pressure. The expansion process also produces rotary motion of the N1 and N2 shafts which is used to drive the compressor and fan. After expansion, the high-velocity air is passed through the exhaust nozzle which further increases the velocity of the air which is leaving from the aft of the engine. Now the thrust is produced as according to Newton's Third law of motion that for every action there is an equal and opposite reaction. The secondary air coming out from the aft of the engine is the action for which we get a forward push which is the reaction. Thrust is not only produced by the air coming out of the exhaust nozzle but also due to the by pass air. To know more about the construction of an aircraft and thrust production in an aircraft engine you can read here

A very interesting fact which should be remembered is that the major amount of thrust produced by an aircraft engine ( approx 80% )  is by the by pass air and the rest 20 % is produced by the air passing through the core engine. The ratio of the f mass flow rate of the by pass air to the mass flow rate of the secondary air is called the by pass ratio. For ex- 10:1 by pass ratio means that 10 kg of air passes through the by pass duct for every 1 kg of air passing through the core engine.

Airbus A320


As you all have understood about the by pass ratio, let us move our discussion towards ultra high by pass ratio. For a normal turbojet engine such as the V2500 engine the by pass ratio is around 5-6 :1 but in case of PW1100G-JM the by pass ratio increases to a value of 12:1, ye that is ultra high by pass ratio.

Advantages of ultra high by pass ratio

1. Lower fuel consumption ( upto 20% fuel consumption reduction )

2. Lesser noise created by the engine

Simple thrust equation of aircraft propulsion is

               

Here Pe and Po are the pressures at the exit and inlet of the engine.
        Ve and Vo are the velocity of the air at the exit and inlet of the engine.
        Me and Mo are the mass flow rate at the exit and inlet of the engine.

 We can very clearly see that as the value of Me that is the mass of air leaving the engine increases the value of thrust force F provided by the engine increases. You will be easily be able to relate to the fact that increasing the mass of air coming inside the engine would surely increase the mass of air leaving from the engine hence a very high value of by pass ratio would increase the thrust value.

Now the other method of increasing thrust would have been increasing the velocity of air leaving the engine. The only method of doing that is to increase the mass of air fuel mixture burning inside the combustion chamber which would increase the fuel cost.

So we can say that having an ultra high by pass ratio is better than burning more amount of fuel both environmentally as well as economically.

After knowing about what is ultra high by pass ratio and what does it affects now let us examine the technology behind ultra high by pass ratio.

THE FAN DRIVE GEAR SYSTEM

Fan drive gear system was initially named as ATFI Advanced Technology Fan Integrator then the it again got a new name as Geared turbofan technology and now we know it as the Fan Drive Gear System. Though the name of technology has changed over time but the engineering behind the technology has always remained the same.

Aircraft engine fan


 If moving the larger mass of the air is the solution then we can simply make the fan blades very large and make them spin very slowly or we can make more air to pass through the core engine. But both the situations have some shortcomings in the first case as we have the fan coupled directly to the low pressure compressor hence we can not rotate the fan at lower speeds as that would require higher compressor stages. Now if we move the fan at a higher speed then we would get a disadvantage in form of tip losses at the tip of the fan blade hence lowering the engine's efficiency. Now the next solution was to make more to pass through the core engine, that would create a great hike in the fuel requirement as well as a major increment in the noise produced by the engine due to the friction of air.

To counter these problems a person at Pratt and Whitney brought a new technology after working for around 20 years endlessly. A 3:1 ratio gearbox is used between fan and the low pressure compressor shaft, (assuming that you have read the above mentioned article at least once) now the fan is rotated at slow speeds as required and the LPC is made to rotate at high speed compared to the fan and that too in opposite direction. The high pressure spool connecting the high pressure compressor to the high pressure turbine and the fan rotate in the same direction but the fan rotates at a much lower speed as compared to the fan and the low pressure compressor along with the low-pressure turbine rotate in the opposite direction as compared to both of them hence apart from solving the first problem as we discussed earlier we also get a rotational balancing in the engine.

This ends up discussion about the fan drive gear system apart from creating the ultra high by pass ratio the FDGS have many other advantages such as reduction in compressor and turbine stages and more......

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Suggested article: How aircraft hydraulic system work?

How Aircraft hydraulic system works?

Aircraft hydraulics system

Aircraft hydraulic system

Today, an aircraft in the modern times uses a hydraulic system to operate many of its critical components. Taking time back, hydraulic systems well still incorporated into the aircraft as a form of hydraulic breaks. With the passage of time, as the technologies evolved, so did the use of the hydraulic system. At present, hydraulics are used in many aspects in the aircraft, which includes, landing gears, brakes as well as flight control surfaces. Regardless of the size and shape of the aircraft, the basic principles and functionality of the hydraulic systems virtually remain the same.

The main reason behind this increased usage of the hydraulic systems are;

- They are very cost effective to install,
- Relatively easier maintenance,
- Can operate at maximum efficiency even at the toughest flight conditions.

 Apart from this, the components used in a hydraulic system are typically lightweight, their installation is not complicated and they process a simple investigation methodology. Adding to their design and incorporation of fluid dynamics, the hydraulics have maximum efficiency with negligible frictional losses.

BASIC COMPONENTS OF A HYDRAULIC SYSTEM

All though hydraulic systems have proved to be an extremely safe and durable introduction in the aircraft industry, certain redundant systems are embedded into the aircraft to enable safe operation in case of failure of the hydraulic systems.

The basic components of a hydraulic system are:

Pump – The pump is a device that is used to generate power in order to pressurize the system.

Reservoir – The reservoir is the vessel that is used to store the hydraulic fluid which is supplied to the system.

Actuating Cylinder – The actuating cylinder is that part where the major function of the hydraulic system is operated. For instance, these cylinders are installed at the flaps of the aircraft so that the pilot can withdraw and extend them as per his/her requirements.

Pressure Relief Valve – The pressure relief valve is used to protect the hydraulic system in case of excess pressurization.

Heat Exchanger – The heat exchanger is a device used to help maintain the hydraulic fluid at an optimum temperature.

These are basic elements that constitute a hydraulic system. However, in larger aircraft or in aircraft with more scope have additional components.

Aircraft hydraulic system


WORKING OF A HYDRAULIC SYSTEM

The hydraulic system of an aircraft works on the principle that, it uses a pressurized liquid to help in movement of certain body components from one position to another position. The hydraulic system has a wide range of pressure capacity from a few hundred pounds per square inch to more than 5000 pounds per square inch. This wide range of the hydraulic system is to cope with different sizes of aircraft and different loads.

Pascal's law is the main science used behind this principle of hydraulics system, which states that when you apply pressure anywhere onto a liquid which is enclosed in a system will exert the same pressure by distributing it in the surrounding medium.

During the flight, the pilot brings the hydraulic system to activation method by switching on the input or flight control device. As the pump starts operating, the actuation begins to move.

The actuator forwards it's motion by directing it to a control surface or any other device that needs to be moved to the desired motion. The pressure is released when the system needs to be moved in the reverse direction.

Aircraft hydraulic system


HYDRAULIC FLUIDS

Hydraulic fluids majorly function in order to convey power between components. However, they are also used for other reasons such as protection of hydraulic machine components. There are many important factors that one needs to keep in his/her mind before selecting an optimum fluid to be used in the hydraulic system, they are:

Supposed to be non compressible ( with high bulk modulus), Less volatility, Moderate heat transfer, Optimum thermal capacity and conductivity, good viscosity, be able to minimize internal leakage, High viscosity index, Special function, Fire resistance, Friction modifications, Radiation resistance, Environmental impact, Low toxicity when new or decomposed, Biodegradability, Functioning life and Material compatibility.

Usually, hydraulic fluids incorporated are based on mineral oil or water. Skydrol is the widely used hydraulic dluid in the aircraft.

Thanks for reading!


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