Project-1: Powertrain for aircraft in runways
1. Total weight of various types of aircrafts.
The aircraft gross weight 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 fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in flight refueling.
The weight of the Aircraft is determined as,
Each component has some weight Wi = mi*g
mi - component mass
g - gravitational acceleration
Weights acting on Aircraft,
Wf - fuel
We - Engine
Ww - Wings
Wb - Body
Wp - Payload
Wv - Vertical tail
Wh - Horz. tail
Types of aircraft Weight,
1)Manufactures empty weight:
-It includes the weight of the aircraft of the entire flight with its intergal working parts,but excludes baggage ,passenger and fuels.
2)zero fuel weight:
-It includes total weight of aeroplanes including unuseable fuels but excludes total weight of useable fuel at board.
3)Payload:
-It is load carrying capacity of an aircraft which includes passenger ,cargo and fuels,But if it is in the case of cargo flight it determines a total load of logistics weight of the container which it needs to transport.
4)Maximum take-off weight:
-This is the maximum weight at which the aircraft would be made to takeoff.
5)Regulated take-off weight:
-Depending on different factors (flap setting, altitude, length of runway), RTOW varies for each takes off,but can never be high for MTOW.
6)Maximum landing weight:
-It is the maximum weight at which an aircraft is permitted to land.
7)Maximum Ramp weight:
-It is the maximum weight used for manuevering (towing) aircraft on the ground.
2. Difference between Ground Speed and Air Speed.
Ground speed:
It is the airplane's speed relative to the earth's surface. One thing that should be noted here is that it’s horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero. They are the calculated by summing up the airspeed and windspeed.
Air speed:
It is the airplane's speed relative to the air it is flying in. Air speed is what determines whether there is enough airflow around an aircraft to make it fly. They are independent of ground speed.
Here wind speed is the vector difference between ground and air speed. The wind speed is zero and it is equal to the ground speed. If the measured air speed is greater than the observed ground speed the wind speed becomes positive.
1. The aircraft operates on both ground as well as in the air so we need to observe how these speeds are related.
2. The ground speed and air speed are usually depend on the wind speed. If the wind speed changes these speeds may change.
3. If we consider there is no wind speed then the air sped is equal to the ground speed .
4. If the wind is flowing in the same direction of the flight then (air speed < ground speed ) so air speed = ground speed -wind speed.
5. If the wind is flowing in the opposite to direction of the flight then (air speed > ground speed ) so air speed = ground speed+wind speed.
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
when airplanes start using reverse thrust it will consume lot of fuels as well as causes lot of noise and also hazardous for the people working. Generally most of the airplanes can move in reverse manner by making use of Reverse thrust technology.But in most of the practical it is not possible.
The reason behind not recommending the engine power to move on gound,
1. Engine Noise (Making loud noise).
Thrust reversal involves great forces, and produces an incredible amount of noise. To keep noise pollution to a minimum, we try to avoid roaring jet engines as much as possible. An engine running at full thrust would also blow away any loose parts or people on the platform. Some might consider this a safety risk.
2. Cleanliness is next to lower maintenance cost.
Reversing engine thrust leads to an increase in CO2 production. In addition, thrust reversal can only be used above a certain speed, because otherwise all kinds of dirt will get sucked into the engines. This dirt then causes increased wear and tear of both the engine and the aircraft. All in all, plenty of reasons not to have airplanes taxiing in reverse.
3. Tug back move (tow),
We use a pushback tractor. This special vehicle uses a tow bar, which is attached to the nose wheel of the aircraft. Modern pushback tractors are able to lift the aircraft’s nose wheel, making connecting and disconnecting the tow bar much less time-consuming. Once the tow bar is connected, the tractor is able to push the plane back.
Hence, Due to the above reason Engine power is not recommended to move on gound.
4. How an aircraft is pushed to runway when its ready to take off.
The airplane may be pushed or pulled by landing gear or wing struts since they're known to be strong enough to drag the airplane through the air. To allow for turns, a person may either pick up or push down on the tail to raise either the nose wheel or tail wheel off the ground, then rotate the airplane by hand.
Usually, the engines are run at full power during takeoff. Following the taxi motion, the aircraft stops at the starting line of the runway. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems.
5. A). Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
Take off is the phase of the flight in which an aeroplane leaves ground and becomes airbone.For lighter aircraft full power is given durong take off where as on the other hand large cargo carriers aircraft make use of less power during take off inorder to inrease the life span of engine,reduce maintenance cost ,reduce engine heat and also for a smooth take off flight.
Force and power required to pull or push an aircraft by a towing vehicle:
-The solution is given as below:
-The different forces involved while a plane bring moved by tow are the following:
1)Rolling resistance of friction force on aircraft (Fr1)
2)Drag froce on aircraft(Fd1)
3)Rolling resistance force on the thug (Fr2)
4)Drag force on thug(Fd2)
The forces involved during take off are the following:
T - Thrust froce pushes the aircraft in forward dierection on the runway.
D - Drag force resist the forward motion of the aircraft.
F - Rolling resistance force when wheel comes in contact with the gorund during landing and take off.
During take off on the runway the imbalance froce will cause an acceleration along the runway and it is given by the formula:
dv / dt = T - D - F/m
Tyre design of an aircraft:
An aircraft tyre are deisgned to withstand extreme heavy loads by absording shocks during and there by providing cushioning effect. The number of tires required for an aircraft depends on the total weight of aircraft as the weight needs to be distributed evenly. Aircraft tyre are designed to facillitate stability in high crosswind condition,to chanalize the water away for preventing skidding and helps to give a good braking effect.
Rolling Resistance:
Rolling resistance or rolling drag is the force resisting the motion when the body rolls on a surface and it is mainly caused by non elasticity that is not all the energy needed for the deformation of wheel is recovered when the pressure is removed.
The rolling resistance equation can be defined by the folowing equation:
Rolling Resistance - Fr - CW/r
C - Co-efficient of rolling friction
W - Weight of the body
r - radius
Tyre Pressure:
Aircraft tyres are designed to withstand heavy loads and shocks durong landing and take off and also needs to distribute weight evenly. As per research and testing it is found that aircraft tyres are able to sustain pressure upto 800 psi.Generally to note the tyre pressure of an aircraft a special type of sensors are used.
There are 2 primary parameters which is hazardous to the aircraft tires:
1. Deflation
Here the tire deflates in a controlled ma-nner with minimum dierect consequence to other system.
2. Explosive breakup
In this case the tire deflates or bursts in an uncontrolled manner with a probablity of causing damage to other secondary system,which further can cause a major crash landing incidents.
Brake forces:
Braking an aircraft is a challenging job for most of the pilots especially during landing in a rainy and cross wind environment. Inorder to encounter this kinds of problem pilots usually make use of spoilers and reverse thust method inorder to have a safe landing so that the energy required to apply brakes on tires can be reduced and henceforth they do not skid. Now there is method which determines the brake force for aircrafts and they are as follows:
k = 1/2 mv^2
where m= mass of aircraft
v=velocity of aircraft.
6. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
A). MATLAB Calculation,
based on the previous ans,
Force required to push/ pull the aircraft = 84.96 N
Power = 472 Kw
Let us assume radius of tyre = 25 inches = 0.653 meter
Gear Ratio = 8
Transmission efficiency (et) = 87%
Motor efficiency (em) = 95%
Rated Power= 950 kw
sol,
Torque of wheel = force * radius in meter
Tw = 84.96*0.653
Tw = 55.478 Nm (Wheel Torque)
Motor Torque = Tw / (Gear Ratio * Transmission efficiency (et))
Tm = 55.478/6.8
Tm = 8.15 Nm (Motor Torque)
Total power required by the motor considering all efficiencies,
= Total Power (Kw) / Total Efficiency
= 472/(0.87*0.95)
= 472/0.8265
Total Power = 571.08 kW
Let us assume the towing operation is done for 20 mins, (0.33 hours)
Total Energy Consumed Power = 571.08 * 0.33
Power = 188.4564 Kwh
Duty Cycle (d) = Required Power / Rated Power
Duty Cycle (d) = 571.08 / 950
Duty Cycle (d) = 60.1
Duty cycle range to control the aircraft speed from 0 to 60.1
Table of assumed parameters,
| S.NO | PARAMETERS | VALUES |
| 1 | Mass of aircraft | 183500 |
| 2 | mass of towing | 30000 |
| 3 | Coefficient of rolling resistance (aircraft) | 0.005 |
| 4 | Coefficient of rolling resistance (vehicle) | 0.002 |
| 5 | Drag Coefficient (aircraft) | 0.12 |
| 6 | Drag Coefficient (towing) | 0.6 |
| 7 | Frontal area (aircraft) | 320 |
| 8 | Frontal area (towing) | 42 |
| 9 | Towing speed | |
| 10 | Air Density | 1.25 |
| 11 | Gravity | 9.81 |
| 12 | Time of Towing | 20 |
| 13 | Tyre radius | 0.653 |
| 14 | Gear ratio | 8 |
| 15 | Transmission efficiency | 0.87 |
| 16 | Motor efficiency | 0.95 |