Project-1: Powertrain for aircraft in runways
PART A
Study 1 : Search and list out the total weight of various types of aircrafts :
The aircraft gross weight (also known as the all - up weight and abbreviated AUW) is the total aircraft weight at any
Moment during the flight or ground operation .
An aircraft's gross weight will decrease during a flight due to the fuel and oil consumption . An aircraft's gross weight may also
vary during a flight due to payload dropping or in - flight refueling .
At the moment or releasing its brakes , the gross weight of an aircraft is equal to its takeoff weight . during the flight , an
Aircraft's gross wieght referred to as the en - route weight in flight weight .
An aircraft's gross weight limits are estabilished during an aircraft's design and certification period and are laid down in the
Aircraft's type certificate and manufacture specification documents .
The absolute maximum weight capabilities of a given aircraft are referred to as the structural weight limits . the structural
Weights limit are based on the aircraft maximum structural capabilities and develope envelope for the CG chart (both maximum
weight and CG limits) .
An aircraft's structural weight capability is typically a function of when aircraft was manufactured , and in some cases , old
aircraft can have their structural weight capability increased by structural modification .
Maximum Design Taxi Weight(MDTW)
The maximum design taxi weight (also known as the maximum design ramp weight (MDRW)) is the maximum weight
Certificated for the aircraft manoeuvring on the ground (taxiing or towing) as limited by the aircraft's strength and the
Airworthiness requirements .
Maximum Design Takeoff weight(MDTOW)
It is the maximum certificated design weight when the brakes are released for takeoff and is the greatest weight for which
Compliance with the relevent structural and engineering requirements has been demonstrated by the manufacture .
Maximum Design Landing weight(MDLW)
The maximum certificated design weight at which the aircraft meets appropriate landing certification requirements of the
Variable shats of the machine . it generally depends on the landing gear strength of the landing impact load on certain
Parts of the wings of structure of the mahine of aircrafts .
The MLDW must not exceed the MDTOW . The maximum landing weight is typically designed for 10 feet per second (600feet
per minutes) sink rate at touch down with no structural damages of the machine .
Maximum Design Zero - Fuel Weight(MDZFW)
The maximum certificited design weight of the aircrafts less all usable fuel and other specified usable agents (engine injection
Fluid , and the other consumable propulsion of the machine of agents . it is maximum weight permitted before of the
Usable fuel and other specified usable fluids are located in specified section of the airplane . The MDZFW is limited by the
Strength and airworthness requirements . At this weight , results in the aircrfat's design strength beings exceeded of the
Weight diffferences between the MDTOW and the MDZFW may be utilised only for the addition of fuel .
Minimum Flight Weight(MFW)
Types of Aircrfat's and their weights :
Those that are lighter then air and those that are heavier than air .
1. Air - craft gross weight :
Aircraft such as ballons , nonrigid airships (blimps) , and dirigibles are designed to containt with in their structure a
Sufficient volume that , when filled with a gas lighter than air (heated air , hydrogen ,or helium) ,displaces the places
The sorroundings ambient air and floats , just as a cork does on the water . Ballons are steerable and drift with the values
The wind . Nonrigid airships , which have enjoyed a rebirth of use and interest ,do not have a rigid structure of the .
Takeoff Weight components
Aircraft's such as ballons , nonrigid airships (blimps) they have a source of propulsion and can be controlled in all three
Axes of flight . Dirigibles are no longer in use , but they were lighter - than - air craft with a rigid internal structure of the
which was usually very large , and they were capable of relatively high speeds , it proved impoosed values .
Nonrigid airship , which have a enjoyed a rebirth of use and interest , do not have rigid structure but have a defined a
Aerodynamics shape . which contain cells field with the lifting agent they have a source of propersion and can be controlled
In all three axes of flight . Dirigibles are not longer not in used but they have very large speed on they were capable on it
Withstand routine operation under all operation weather condition , and most suffered disaster either breaking up in storm
As with the U.S craft Shenandoah , Akron , macron or through ignition of the hydrogen , as with the .
Balloon - 400Kg
Airship - 130,000Kg (Empty weight) , 260,000Kg (full load wieght)
2.Heavier - than -air :
This type of aircraft must have a power source to provide thrust necessary to obtain lift . Simple heavier - than - aircraft to
Obtain lift , include kites these are us usually a flat - surfaced structure often with stabilizing ''tail'' ,attached by the bridle
to a srting that is held in place of the sting -restarined surface to the wind .
Another type of unnamed aircraft is the unnamed aerial vehicles (UAV) , commonly called drones or sometimes to the
remotely piloted vehicles (RPVs) . These aircrfat are radio - controlled from the air or the ground and are used for scientific
And military purpose . unpowered manned heavier than - air vehicles must be launched to obtain lift . these include to the
Hnag gliders , and sailplains . Hang gliders aircraft of varous configration in which the pilot is suspended beneath to the
(Usually fabric) wing to provide stability and control . they are normally launched from launched from high point to the
Hang gliders are usually most of the sailplains are towed to launch altitiude , although some employ small to the variable
Retractable auxiliary engines . they have able to use thermals (current more buoyant than the sorrounding air , usually
caused by high tempreture and orographic lift to climb to a higher altitude and to glide for great distance load against to the
Orographic lift results from the mechanical effect of wind deflecting upward by the face of the terrain , resulting in a rising
current of air , Ultalights which are originally merely hang gliders adapted for power by the installation of small engines to
Similar to those used in chain saws , have matured in to the specially designed aircraft of very low weight for the aircraft.
They have intended primary for pleasure flying although aircraft of tha training used in combat .
High Altitiude Plateform system (HAPS) : Technology Trends Predator
RQ - 4 Global Hawk - 13325Kg
RQ - 7 Shaddow 200 - 150Kg
Shaddow 200 - 150Kg
Aerovironment - 200 g
Mavic Pro 2 - 907 g
3.Civil Aircraft :
All nonmilitary planes are civil aircraft , these include private and business planes and commercial airlines .
Private aircraft are personal planes are used to pleasure flying , often single engines monoplanes with nonrectractable
Landing gear . they can be very shophisticated , however , and may include such varient as ''Warbirds'' ex - military
Planes flown for reasons of nostalgia , ranging from primary trainers to large bombers ; ''homebuilt'' , aircraft built to the
From scratch or from kits by the owner and rangings from the simple adaptation of piper cubs to high speed ,streamlined
Four passengers to transport antiques and classics restored older aircraft flown , like the warbirds , for reason of affection
Bussiness aircraft are used to generate revenues for their owners and include everything from small - single engines to the
Aircraft are used for pilot tarining or to transport small packages over short distance from the variable values to the aircraft
Business planes are used by salespeople , prospectors , farmers , docters , missionaries and many others . their primary
Perpous is used to make the best used of primary top executive to the load .
They also have as an executive prerequisite and as a shophisticated inducement for potential customers . other business
Aircraft include those used for agriculture operation , traffing reporting forest - fire fighting , medical evacuation on the values
Pipeline surveillance , freight hauling and many other application . one unfortunate but rapidly exapanding segment to the
Business aircraft illegally for transporting narcotics and other illicit drugs , A wide variety of similar they also have to the
inducement for a potential of flying to the jet meachine to the variable medical evacuation to the load many other application
business aircraft propulsion is that which employed aircraft illegally for transporting narcotics to the load side of the machine
specialized purpose , as the investigation of thunderstrom , hurricane trackling aerodynamics research and developement to
The engine testing high - altitude surveillance , advertising and police work .
Antonov An - 225 Mriya - 640.000Kg
Scaled Composite Stratolaunch
Airbus A380 - 575,000Kg
Boeing 747 - 8 - 447,700Kg
Mc Donnell Douglas DC -10 - 256,280Kg
ATSB Released Final Report on Snab 340 in - flight Loss of a propeller
Learjet 70/75 - 9,752Kg
Embraer Phenom 100 - 4800Kg
Q.2
Study 2: Is there any difference between ground speed and air speed ?
One of the most confusing concept for young scientists is the relative velocity between objects . Aerodynamics forces are
Generated by an object moving through a fluid (liquid or gas) . A fixed object in a static does not generate aerodynamic
Forces . Hot air balloons ''lift '' because of buoyancy forces and some airlift like the harrier use thrust to ''lift '' the vehicle
but these are not examples of aerodynamics forces . Hot air balloons . to generate lift an object must move through to the
Air must to the variable to the load . to generate lift , depends the vehicle , but these are not example of aerodynamics lift
To generate lift , an object must move past of the object . aerodynamics lift depends on the square velocity between to the
object be moved through the air , but the air itself can move . to properly define the air itself can move . to properly define
the relative velocity to the fixed point but it could just as easily be fixed to the aircraft itself . it is important to understand
the relationship of wind speed to ground speed and airspeed .
Wind Speed
For a reference point picked on the ground , the air moves relativeto the reference point at the wind speed . Notice that
The wind speed is a vector quantity and has both a magnitude and a direction . the direction is important . A 20 mph wind
from the east . The wind has component in all thee primary direction (north - south , east - west , and up - down) .in this
Figure we are considering only velocities along the aircraft's flight path . A positive velocities along the aircraft's flight path
A positive velocity is defined to be in the direction of the aircraft's motions . we are neglecting crosswinds , which perpen
dicular. of the motion and updrafts and downdrafts , which occurs perpendicular to the grounds .
Ground speed
For a reference point picked on the ground , the aircraft moves relative to the reference point at the ground speed
Ground speed is also vector quantity so comprasion of the ground speed to the wind speed must be done according to
Rules for vector comparisons .
Airspeed :
The important quantity of the generation of lift is relative velocity between the object and the air , which is called airspeed
Airspeed cannot be directly measured from ground position but must be computed from the ground position but must be
wind speed , Air speed is the vector quantity aircraft moving , the airspeed will be less than the ground speed .
Examples
Suppose we had an airplane that could take off on a windless day at 100mph (liftoff airspeed is 100mph) . we are at an
Airport with an east - west runway that is 1 mile long . The wind is blowing towards the aircraft which we call a headwind
Since we have defined a positive velocity while the plain is sitting still on the runway , it has to be ground speed 0 and an
airspeed of 20mph :
Airspeed = Ground speed (0) - Wind speed (-20) = 20mph
The airplane starts its take off roll and has a constant acceleration a . from newton's second law of motion , the ground
speed V at any time t is .
V = a*t
And the distance d down the runway at any time is :
d = 1/2 * a * t^2
For fixed length runway ,this specifies the time to be used in the velocity equation
Let's assume that a 5000 feet dow the runway , the velocity is 80mph . then the airspeed of the aircraft's is given by
Airspeed = Ground Speed (80) -Wind Speed (-20) = 100mph
And the airplane begins to fly , Now another pilot with exactly that same airplane decides to take off the west . the wind is
Now in the same direction of the machine as the motion and that is called tailwaind , The sign on the wind speed is now
Positive , not negative as with the headwind . the acceleration along the ground is the same , so at 5000 feet down the
Runway , the ground speed is again 80mph . the airspeed is again 80 mph the airspeed is the given by :
Airspeed =Ground Speed (80) - Wind Speed (20) = 60mph
This airplain desn't have enough airspeed . to fly it runs off the end of the runway :
Q.3
Study3: Why is not recommended to use aircraft engine power to move it on the ground at Airport :
For movement on the ground the aircraft are uses it own engine power , which is called taxing . although many aircraft are
Capable of moving in backward using in reverse thrust , as result the jet blast or prop wash might cause damages to the
Terminal building or equipment . engine close to ground may also blow sand and debris forward and than suck them in to
The engine , causing damages to the engine . therefore there are pushback truck lift to the front wheel of the aircraft's in the
A pushback trucks in the airport away from the parking spot to the taxiways , which is called towing .
Unwanted consequences mainly arising from the unintended movement of the aircraft's during engine running .
a) Effectively a loss of control can happen , especially during high power engine running . Damages can occures to the
Aircrafts itself , other aircraft near by or to the air side structure .
b) There is a risk of injury to ground support personal who may be in relatively close proximity to the aircraft in the engine.
c) It is easier for truck driver to see the sorrounding better than the pilot .sitting in the cockpit with limited window
The power of pushback driver known as the airport better than the pilot .
d) It also saves fuel . Virgin atlantic had proposed a new system in which pushback truck will move the aircraft's all the way
To runway save fuel and reduces impact environment .
e) The plane engines are very laud , when more than one plane will be add up their sound ,than it will not be pleasant for
passagers and others near airport .
Q.4
Study 4: How an aircraft is Pushed to runway when its ready to take of ?
Taxiing : Taxiing (rarely spelled taxing) is the movement of aircraft on the ground , under it's own paper in contrast to
Showing it is towing or push - back where the aircraft's usually moves on wheels , but the term also includes aircraft's in the
with skies and floats (for water - based travel) .
An airplane uses taxiways to taxi from one place on an airport to another for example , when moving fromm hanger to the
Runway . the term 'taxiing'' is not used for the acceleratings run along the runway prior to take off , or the decelerating run
Along a runway ,which is called the takeoff roll and landing rollout ,respectively .
Towing :
Movement of large aircraft's about the airport , flight and hanger usually acomplished was towing with a tow tractor the
(sometimes called a ''tug'') . in case of the small aircraft ,some moving is accomplished by hand pushing on the correct areas
of the aircraft's . aircraft may also be taxied about the flight line but usually only certain qualified personnel .
Towing aircraft can be hazardous operation , causing damages to the aircraft and injury to personal , if done recklessly
or carelessly . the aircraft specific intrustion for each model of an aircraft are detailed in the manufactures maintenance
instruction and are to be follwed in all instances .
Before the aircraft to be towed is moved , a qualified person must be in the flight deck to operate the brakes in casse to
The ''Tow bar fails'' or becomes unhooked . the aircraft can than be stopped , preventing possible damages .
Some types of Tow bars available for general use can be used for many types of follwing operation [Figure 2] these are
Bars are in the designed with suffiecient tensile strength to pull most aircraft , but are not intended to be subjected in the
Torsional or twisting loads . many have small wheels that permit them to be drawn behind the towing vehicle to be or ,
From an aircraft . when the bar is attached to the aircraft , inspect all the engaging devices for damages or malfuntion
before moving the aircraft .
Figure 2 . Example of a tow bar
Some tow bars are designed for towing various types of an aircraft . However , other specially types can be used on particular
Aircraft only . such bars usually designed and built by the aircraft manufactured .
When towing the aircrfat , the towing vehicle speed must be reasonable , and all person involved in the operation must be
Involved do not rely upon the brakes of the towingvehicle alone to stop the aircraft . the person in the flight deck must in
Coordinate the use of aircraft brakes with those of the towinf vehicles . A typical smaller aircraft tow tracter (or tug) is shown
Figure 3 :
Figure 3 . Typical smaller aircraft tow tractor
The attachment of the tow bar varies on different types of aircraft . Aircraft equipped with tails wheel are generally towed
Forward by attaching the tow bar to the tail wheel axle . any time of aircraft equipped with a tail wheel is towed , the tail
Wheel must be unlocked or the tail wheel must be locking , mechanism may damages or break . Aircraft equipped with the
tricycle landing gear are generally towed forward by attaching in the bridle or specially designed towing bar to towing bar to
The towing lungs to this manner , a steering bar is towed in this manner , a steering bar is attached to the nosewheel in the
attached to the variable load supply atteched in the wheel .
Q.5
Study 5: Learn about take off power tyre design ,rolling resistence ,tyre pressure ,brake forces when landing
Take off
Takeoff is the phase of flight in which an aerospace vehicles leaves the ground and becomes airborn . for aircraft that take
off horizentally , this usually involves starting with a transition from moving along the ground on a runway . For ballons , the
Helicopters , and specialized fixed - wing aircraft (VTOL aircraft such as the Harrier) . no runway is needed . takeoff is the
opposite of landing.
Take of performance can be predicted using a simple measure of the acceleration of the aircraft along the runway based
On face equilibrium .
The forces involved will be ,
T - Thrust of propulsion system is pushing aircraft along runway .
D - Aerodynamics Drag of Vehicles resisting the aircraft motion .
F - Rolling resistence friction due to the contact of wheels or skids on the ground .
During take-off run the imbalance in these forces will produce an acceleration along the runway.
dV/dt = T - D - F/ m
where dV/dt is the acceleration along the runway and m is the mass of the vehicle.
The procedure for take-off will be that the vehicle will accelerate until it reaches a safe initial flying speed. The pilot can then
rotate the vehicle to an attitude to produce climb lift and it will ascend from the ground. The determination of this safe flying
speed or rotation speed, VR, is a critical factor in determining take-off performance.
Take-off rules vary slightly depending on the aircraft category. Small commuter aircraft should be considered as meeting FAR
23 rules, transport category aircraft should comply with FAR 25 rules.
aircraft :
For safety reasons VR is usually determined as being 1.1 × VSTALL or 1.05 × VMIN CONTROL
which ever is greater. Stall speed, VSTALL, is the lowest speed that the aircraft can be flown before the airflow starts to
separate from wings as the angle of attack becomes too great. The wing is assumed in this case to be in take-off configuration or "clean".
It can be calculated based on knowledge of the aircraft take-off configuration and hence the maximum achievable lift
coefficient CL(max). As shown in the previous section , to maintain level flight the lift produced must equal the weight, hence
the stall speed can be calculated as,
Vstall=√W12CL(max)ρSVstall=W12CL(max)ρS
Minimum control speed, VMC is a more complex calculation and requires knowledge of the stall characteristics of the tailplane
and elevator. For conventional aircraft there is only a small difference between VR calculations based on stall speed or minimum control speed.
As well as rotation speed there are other safety considerations as shown in the following Figure.
V1- Abort decision speed. Below this speed the take-off can be safely aborted. After this there will not be sufficient runway
length to allow the aircraft to decelerate to a stop.
V2 – Safe climb speed. V2 must be no less than 1.2 * Vstall. Below this speed aircraft cannot attain sufficient climb rate.
Transport Aircraft :
VR must not be less than V1
VR must be greater than 1.05 * VMC
VR must be set so that aircraft achieves V2 before reaching a height of 35ft above the runway surface.
Aircraft must climb at a minimum gradient to avoid obstacles at the end of the runway. With engine failure on multi-engined
aircraft, this speed should still be achievable.
Thrust:
The thrust of gas turbine or turbofan engines will be relatively constant during take-off. A good assumption is to use the
manufacturer's values for maximum static thrust for take-off calculations.
T=Pshaft×ηVT=Pshaft×ηV
`t is critical to correctly estimate the propeller efficiency for the particular aircraft velocity along the runway. At V=0 the
efficiency is 0 so the above equation makes no sense. At V=VR the efficiency will be in the range 50% to 80% depending on
`the type of propeller system used and the thrust value at this point will be easy to obtain. In practice, the thrust obtained
throughout the take-off roll is roughly constant so this end point value is a good approximation from V=0 to VR
Drag:
The resistance to motion due to the air viscosity will give a drag of
D=12⋅Cd⋅ρ⋅A⋅V2D=12⋅Cd⋅ρ⋅A⋅V2
where CD can be considered constant,
Although Drag Coefficient is constant, Drag will increase in proportion to the square of velocity.
Rolling Resistance:
The friction between aircraft and runway will be proportional to the normal force exerted by the aircraft on the runway.
F=μ(W−L)F=μ(W-L)
The normal force will be the difference between Weight of aircraft and Lift, the friction coefficient will be typically of a magnitude of 0.02 for a standard tarmac runway.
The rate of change of velocity can be predicted at any point on the take-off roll by substituting results for T, D and F into thE
initial equation for dV/dt. The subsequent velocity at any point can be found by integrating this resulting equation and the
distance traveled found by then integrating the velocity.
Typically acceleration will be dominated by the drag component as thrust, weight and friction are relatively constant during
this period. This leads to the result shown where acceleration is inversely proportional to velocity squared.
Due to the quadratic nature of acceleration change, an average value, (dVdt)avg=a(dVdt)avg=a can be used for the
take-off run. This average acceleration can be found at the point where,
V=VR√2V=VR2
This average acceleration can be used to simplify calculations and the take-off run can be calculated as an equivalent constant
acceleration over the complete period of time (tR) taken to get from 0 to VR. For a constant acceleration take-off calculation.
VR=a.tVR=a.t and distance travelled S =1/2at^2
Rearranging leads to a relatively simple calculation to predict distance to rotation point.
s1=12V2Ras1=12VR/2a
The negative acceleration or deceleration value will be based on friction coefficient for maximum braking and the value of reverse thrust (if available).
Braking force:
Stopping an aircraft landing at 180-200 mph requires a lot of braking force. To do this, the aircraft has brake unit on each of
the wheels on the maingear assembly. On landing, pilots should use aerodynamic braking by applying extra back-pressure on
the stick or yoke. Extreme caution should be used whenapplying brakes at any signicant speed, and only when the end of
the runway is quickly approaching. Never step on the brakes to make a runway exit. Applyingthe brakes at too high a speed
could burn the tires, wear out the brakes, or result in a ground loop or swerve.
Aircraft Disc Brake:
In the landing gear it is used to brake the wheels while touching the ground. These brakes are operated hydraulically. In most
modernaircraft they are activated by the top section of the rudder pedals ("toe brakes"). In some older aircraft the bottom
section is used instead ("heel brakes"). Leversare used in a few aircraft. Most aircraft are capable of differential braking.
In addition to the brakes, there are two other systems which help slow the aircraft down on landing. The spoilers and the
reverse thrust.
Spoilers
Have you noticed the large panels on the top of the wings raise up on touch down? These are the called the spoilers as they
literally spoil the airflow over the wing. This dumps any remaining lift the wings are generating, allowing the wheels to take all
the weight and achieve maximum efficiency from the brakes.
Reverse thrust
The final part of the braking process comes from reverse thrust. Just after we have touched down, we pull two levers on top of
the thrust levers to engage the reverse thrust, a sort of “reverse gear” for jet engines.
There are two stages of reverse thrust — idle reverse and max reverse. Idle reverse is used on most landings and max
reverse is used when the landing performance requires it, normally when the aircraft is landing at hot or high elevation airfields.
This forward directed airflow helps slow the aircraft down but is most efficient at high speeds. If using max reverse, we drop
this down to idle reverse at 60 knots (70 mph) and then back to normal thrust as we vacate the runway at around 20 knots (25 mph).
Design and construction of the Aircraft tyre:
When it comes to safety, tyres are one of the most important components of aircraft. They help to absorb the shock of landing
and provide cushioning. It also provides the necessary traction for braking and stopping of an aircraft.
An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing, and parking. The number of
wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.
A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22
wheels. Aircraft tyres work under extreme conditions, carrying up to 340 tons and accelerating at over 250 km/hour at takeoff, in addition to enduring varied environmental stress when in flight and taxiing.
Carcass plies are used to form the tire. They are sometimes called casing plies. An aircraft tyre is constructed for the purpose it serves.
- They support the weight of an aircraft while it is on the ground.
- It also provides the necessary traction for braking and stopping of an aeroplane.
- Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.
Unlike an automobile or truck tyre, it does not have to carry a load for a long period of continuous operation. However, an aircraft tyre absorbs the high impact loads of landing, and also it’s operating at high speeds for a short time when
From the rotation point, the end of the runway can be defined by the requirement to clear a 35ft obstacle at the end. During
`rotation it can be assumed that any residual excess thrust is absorbed in overcoming the lift induced drag as the aircraft
begins to climb. Acceleration reduces and a constant flight speed during this climb phase can be assumed. The distance along
the ground from rotation point to obstacle clearance point with thus be`
s2=35tanθs2=35tanθ ft,
Take-off (Balanced) Field Length:
`he required length of runway will be the sum of the distance required to get to rotation speed and the extra length required
to clear a 50ft obstacle or the extra length required to allow for rapid braking if the pilot decides to abort take-off at the decision speed V1`
This length will typically be considerably longer than the distance required to achieve rotation (flying) speed. A rough
approximation is that runway total length is around 2 x s1
Distance to V1 can be calculated in a manner similar to that shown for VR. The calculation of braking distance will require
knowledge of the maximum braking friction coefficient that can be generated by the aircraft. This information should be
available from manufacturer's data. Braking distance calculations should also be done without any assumption of reverse
thrust from engines as during a take-off abort, engine power may not be available.
Landing:
The landing run can be calculated in a similar fashion to the take off distance. The aim is again to minimise the distance.
The touch down velocity should be approximately the stall speed of the aircraft in landing configuration. This will be achieved
by a pitch manoeuvre during the flare portion of the approach which which increase drag an decelerate the aircraft to
minimum flying speed.
The deceleration on the landing roll from VTD to V0 will be accomplished by braking and reverse thrust. This can be solved by
the average acceleration approach that was used to estimate the take-off roll.
dVdt=−T−D−Fm dV/dt=-T-D-Fm
The negative acceleration or deceleration value will be based on friction coefficient for maximum braking and the value of
reverse thrust (if available).
if
Design and construction of the Aircraft tyre:
When it comes to safety, tyres are one of the most important components of aircraft. They help to absorb the shock of landing
and provide cushioning. It also provides the necessary traction for braking and stopping of an aircraft.
An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing, and parking. The number of
wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.
A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22
wheels. Aircraft tyres work under extreme conditions, carrying up to 340 tons and accelerating at over 250 km/hour at
takeoff, in addition to enduring varied environmental stress when in flight and taxiing.
Carcass plies are used to form the tire. They are sometimes called casing plies. An aircraft tyre is constructed for the purpose it serves.
- They support the weight of an aircraft while it is on the ground.
- It also provides the necessary traction for braking and stopping of an aeroplane.
- Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.
Unlike an automobile or truck tyre, it does not have to carry a load for a long period of continuous operation. However, an
aircraft tyre absorbs the high impact loads of landing, and also it’s operating at high speeds for a short time when required.
Retreading – Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus
one or both sidewalls. Repairs are included in the tyre retreading process.
Load Rating – Load rating is the maximum permissible load at a specified inflation pressure.
Ply Rating – Ply Rating is used to identify the maximum recommended load rating and inflation pressure for a specified tyre. It is an index of tyre strength.
Speed Rating – The speed rating is the maximum takeoff speed to which the tyre has been tested.
Skid Depth – Skid depth is the distance between the tread surface and the deepest groove as measured in the mould.
Aircraft tyres must have an approved speed and load rating and have sufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.
Aircraft tyres may be Tube-type or Tubeless
Tubeless tyres are more advantageous over tube-type. There is no longer the use of tube-type tyre in recent aviation. Nowadays all airliners are using tubeless tyres. Tubeless that are meant to be used without a tube has the word TUBELESS on the sidewall of the tyre.
Aircraft tyres may be Radial or Bias
Almost all airliners are using Radial tyre. Bias is an older design, and it’s mainly used for road vehicles. Radial tyres have the
word RADIAL on the sidewall. Radial tires are more expensive than bias-ply tyres. Radial tires are in demand because of their
lower life cycle cost and long term value.
Chines are also called deflectors. Chine tyre used on the nose wheel of aircraft, specially fuselage-mounted jet engines. It diverts runway water away from the engine inlets.
Chines are circumferential protrusions that are moulded into the sidewall of nose tyres that deflect water sideways to help
reduce excess water ingestion into the engines. Tyres may have chines on one or both sides, depending on the number of
nose tyres on the aircraft .
PART B :
Q.6
Study 6: With necessary assumptions, calculate the force and power required to push / pull an aircraft by a
towing vehicle.
To push or pull an aircraft by a towing vehicle, 3 type of forces will act on that vehicle. Those are -(i) Rolling resistance force
(ii) Aerodynamic dragforce and (iii)Hill climbing force.
(i) Rolling resistance force(Frr) :
Rolling resistance is the force resisting the motion when a body rolls on a surface. It is the friction force that is needed to
beovercome to move a vehicle. The kinetic energy of the wheels is partially converted into heat. The rolling resistance is
proportional to the normalforce perpendicular to the rolling wheel and is approximated by the rolling resistance coefficient urr.
Therefore, Equation that can be used for the rollingresistance force of the entire system is-
Frr = urr * m * g where, urr= Rolling resistance co-efficient (It depends on the tire material, tire structure, tire temperature,
road roughness, road material etc.) m= Total mass of the vehicle (vehicle mass + payload) in kg g = gravitational constant ,
that is 9.8 m/s^2.
Here in this case for towing vehicle for aircraft urr= 0.013.
(ii) Aerodynamic drag force(Fad) :
Aerodynamic drag force is the force which is required to keep a vehicle moving. There are two component of this force , one
isshape drag (due to the shape of the vehicle) and another is skin friction (due to friction between air and skin of the vehicle).
When the vehicle moves the velocityof air near boundary is higher than the air surrounding. Both the tug and the aircraft will
experience some aerodynamic drag. For completeness, the aerodynamicdrag force caused by the aircraft and towing vehicle
can be given by Equation below-
Fad = (1/2) * ρ * V^2 * A * (Cd_t + Cd_a)
where, ρ = Air density, that is normally 1.25 kg/m^3
A = Frontal area of the vehicle in m^2
Cd_t = Air drag co-efficient of towing vehicle (It depends on frontal area,shape, protrusions, ducts, air passage etc.)
Cd_a = Air drag co-efficient of aircraft (Itdepends on frontal area, shape, protrusions, ducts, air passage etc.)
v =Velocity of the vehicle in m/s
With regard to the drag equation, the term A simply refers to some reference area. For airplanes, this is generally the
planform area of the wing The designersdesign an aircraft in such a way that the reference area is optimal. So, for calculation
this has been neglected.
In this case air drag co-efficient for towing vehicle(Cd_t)= 0.5 and for aircraft or payload(Cd_a)= 0.045.
(iii) Hill climbing force(Fhc) :
Hill climbing force is the force needed to move the vehicle in up gradient. To Hill Climbing force the expression of the equation isgiven below-
Fhc = m * g * sinφ
where, m = Total mass of the vehicle(vehicle mass + payload) in kg
g = Gravitational constant that is 9.8 m/s^2
φ = up gradient angle or inclination angle in radian
In this case up gradient angle(φ) = 0, as there is no inclination.
Push/Pull Power Calculation of Towing Vehicle-
Hill climb force is zero in this case.
Q.7
Study 7: Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill
aircraft towing application. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make
all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of powertrain diagram .
Table for the necessary assumed parameters-
| Assumption For Powertrain Design | |
| Aircraft Mass (kg) | 575,000 kg |
| Towing Vehicle mass (kg) | 50,000 kg |
| Rolling Resistance Co-efficient | 0.013 |
| Air Density | 1.225 kg/m3 |
| Towing Vehicle Drag Co-efficient | 0.5 |
| Aircraft Drag Co-efficient | 0.09 |
| Frontal area | 20 m2 |
| Inclination angle | 0 rad |
| Tyre Pressure | 203 PSI/14 bar |
| Towing Velocity(V) | 10 km/h = 2.778 m/s |
| Towing Time(t) | 2 min |
| Radius of the towing vehicle wheel |
0.38 m |
Therefore from the excel power calculator we have got the necessary Traction force(F) quantity that is =
| 79770.70804 N |
Required Power =
| 221.7625684 kW |
Required Torque = F x r.
T = 79770.7 x 0.38 = 30,312.87 N-m
Energy, E = P x t.
E = 221.76 x 2 x 60/3600 = 7.4 kWh
For this application an Induction motor or a BLDC can be used with a proper gear system.
The Above 250 kW output motor is best suited to our requirements in the aircraft's .