Project-1: Powertrain for aircraft in runways

PART-1

1.  Weight os aircraft is as shown below:

MANUFACTURER'S EMPTY WEIGHT (MEW)
Also called Manufacturer's Weight Empty (MWE) or Licensed Empty Weight

It is the weight of the aircraft "as built" and includes the weight of the structure, power plant, furnishings, installations, systems and other equipment that are considered an integral part of an aircraft. This excludes any baggage, passengers, or usable fuel.

ZERO FUEL WEIGHT (ZFW)

This is the total weight of the airplane and all its contents (including unusable fuel), but excluding the total weight of the usable fuel on board.

As a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the ZFW remains constant.

Maximum zero fuel weight (MZFW) is the maximum weight allowed before usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents) are loaded.

OPERATING EMPTY WEIGHT (OEW) (Roughly equivalent to basic empty weight on light aircraft)

It is the basic weight of an aircraft including the crew, all fluids necessary for operation such as engine oil, engine coolant, water, unusable fuel and all operator items and equipment required for flight but excluding usable fuel and the payload.

PAYLOAD

It is the carrying capacity of an aircraft. It includes cargo, people, extra fuel. In the case of a commercial airliner, it may refer only to revenue-generating cargo or paying passengers.

MAXIMUM TAKE-OFF WEIGHT (MTOW)

This is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off.

REGULATED TAKE-OFF WEIGHT (RTOW)

Depending on different factors (e.g. flap setting, altitude, air temperature, length of runway), RTOW or maximum permissible takeoff weight varies for each takeoff. It can never be higher than MTOW.

MAXIMUM LANDING WEIGHT (MLW)

This maximum weight at which an aircraft is permitted to land.

The following image depicts takeoff weight components.

MAXIMUM RAMP WEIGHT (MRW) also called maximum taxi weight (MTW)

It is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground.

AIRCRAFT GROSS WEIGHT

It is the total aircraft weight at any moment during the flight or ground operation. This decreases during flight due to fuel and oil consumption.

2) 

True airspeed is simply the speed at which an aircraft is moving relative to the air it is flying in. As such, it’s also the speed at which the air is flowing around the aircraft’s wings.

Ground speed, on the other hand, is the aircraft’s speed relative to the ground. One thing that should be noted here is that it’s its horizontal rather than vertical speed – an aircraft climbing completely vertically would have a ground speed of zero.

In other words, while airspeed is what determines whether there is enough airflow around an aircraft to make it fly, ground speed is what determines how fast an aircraft will get to its destination.

The Three Types of Airspeed

When I talked about airspeed earlier in this article, I was talking about true airspeed. However, pilots commonly use three different types of airspeed: indicated airspeed, calibrated airspeed, and true airspeed.

Indicated airspeed is an airspeed that is calculated directly off an aircraft’s pitot-static system. It’s the calculated off the aircraft’s dynamic pressure – the difference between its total pressure and static pressure.

The dynamic pressure depends not only on the aircraft’s speed, but also on the density of the air it is flying in. As such, the higher the aircraft flies – and the lower the air density as a result – the bigger the difference between indicated and true airspeed is.

Calibrated airspeed is indicated airspeed adjusted for a variety of errors.

Just as an example, one of the things it’s adjusted for is the flap position. The reason for that is that at different flap positions, air flows differently around the pitot-static system and affects the indicated airspeed readings.

True airspeed is, as has been mentioned numerous times in this article, the actual speed at which an aircraft is moving relative to the air it is traveling in. It’s calibrated airspeed adjusted for the the exact conditions (altitude, air temperature, etc.) that the aircraft is flying in.

GROUND SPEED

Ground speed can be determined by the vector sum of the aircraft's true airspeed and the current wind speed and direction; a headwind subtracts from the ground speed, while a tailwind adds to it. Winds at other angles to the heading will have components of either headwind or tailwind as well as a crosswind component.

3. Aircraft moves using there engine power all time on the airport apron and taxiway under there own power to the runway and after landing taxi to the assigned gate. The only time it use external power  to pushback from gate. Large turbofan aircraft requies help to reverse via a push back tractor.

When you arrive at the gate for your flight, more often than not you’ll get a great view of the nose of the aircraft through the terminal window. If you look closely, you’ll be able to see us pilots preparing the aircraft for departure.

However, the obvious problem with parking facing the terminal is that in order to get to the runway, we need to move backward off the stand first. If this was on your drive at home, you’d just pop your car into reverse, back out onto the street and off you go. Unfortunately, aircraft are unable to do this as they don’t have a reverse gear. In order to get round this problem, we use the assistance of a pushback tug.

4. 

Airplanes have engines, and they can use them to move forward along the ground. So they push themselves to the runway.

It true that most of the time, a small vehicle is needed to push the airplane backwards away from the terminal building, because even if a plane can reverse it’s thrust, it’s not always safe to hit the buildings with a jet blast. So the little trucks push the jets back away from the buildings, but after that, the plane can apply a small amount of engine power to roll forward. They push themselves to the runway.

Aircraft need a clearance before entering the runway and will wait for permission while holding short. Once given the go-ahead by ATC, the pilot will add power and use the tiller to line up along the center of the runway.

The nose wheel will be centered by the pilot to allow a smooth transition. Once given the go-ahead for takeoff, the pilot flying will confirm their control of the aircraft, and start to steadily increase power to the take-off setting. The pilot will maintain runway centerline with the tiller, and as the aircraft accelerates the tiller will become increasingly more sensitive. As the tiller becomes less reliable to maintain directional control the pilot will switch to the rudder pedals. Since nose wheel steering is connected to the rudder pedals, which are also used to control yaw, the aircraft can be steadily maintained on the centerline during takeoff with positive controls from the pilot.

Once the aircraft rotates and is airborne, the pilot will continue to use the rudder pedals to control the yaw and have a smooth transition into the air.

When landing pilots maintain directional control on the runway using the rudder pedals until the aircraft’s speed begins to decrease.

5. 

TAKE-OFF POWER:

 The phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as lift-off. For aircraft that take off horizontally, this usually involves starting with a transition from moving along the ground on a runway.

Take-off performance can be predicted using a simple measure of the acceleration of the aircraft along the runway based on force equilibrium.

The forces involved will be,

T – Thrust of propulsion system pushing aircraft along the runway.

D- Aerodynamic drag of vehicle resisting the aircraft motion.

F- Rolling resistance friction due to the contact of wheels or skids on the ground.

THRUST:

It is the force that moves an aircraft through the air. Also it is a mechanical force generated by the engines of the airplane. The engine does work on the gas and as the gas is accelerated to the rear, the engine is accelerated in the opposite direction. The acceleration of the engine mass produces a force on the aircraft.

 

 

TYRE DESIGN:

An aircraft tire is designed to withstand extremely heavy loads for short duration.The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. Tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning and for braking effect.

 

Tire includes fusible plugs, designated to melt at a certain temperature.The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment.

ROLLING RESISTANCE:

The force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects. Two forms of this is hysterisis losses and permanent deformation of the object or the surface. Slippage between the wheel and the surface also results in energy dissipation. Although some reserchers have included this in rolling resistance, some suggest that this dissipation term should be treated separately from rolling resistance because it is due to the applied torque to the wheel and the resultant slip between the wheel and ground which is slip loss.

TYRE PRESSURE:

They usually have high pressures upto 200psi for airliners, and even higher for business jets. The main landing gear on the concorde was typicslly inflated to 232 psi , whils its tail bumper gear tires were as high as 294 psi.

They are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure. Dry nitrogen expands at the same rate as other dry atmospheric gases but compressed air may contain moisture, which increases the expansion rate with temperature.

LANDING BRAKE FORCE:

The brake units are powered by the hydraulics systems. An electrical signal is sent from the flight desk to hydraulic actuators near the main landing gear. Here, hydraulic fluid at 3000 pounds per square inch is used to force the brake unit against the wheel thus slowing it down.  

6.(A) Let us assume Antonov An-225 Mirya

Mass of aircraft M1 = 285,000kg

Mass of Towing vehicle M2 = 60,000kg

Coeffiecient of rolling resistance for dry concrete road, µrr = 0.03

Frontal area of aircraft, A = 355m^2

Drag coefficient of an aircraft, Cd = 0.6

Drag coefficient of a towing vehicle, Cd = 0.15

Density of air =1.225kg/m^3

G = 9.81

Speed of an aircraft V =20 * (5/18) = 5.556 m/sec

ROLLING RESISTANCE FORCE:

For aircraft:

Frr  = µrr * m * g

Frr = 0.03* 285000 * 9.81

     = 83,875.5 N

For Towing Vehicle:

Frr  = µrr * m * g

      = 0.03*60,000 * 9.81

       = 17,658N

We need to add the rolling resistance of both towing vehicle and aircraft.

Frr = Frr (aircraft) + Frr (vehicle)

Frr = 83,875.5 + 1765.8

Frr = 101,533 N

Aerodynamic Drag force:

Fad = (0.5) * ρ * V^2 *(Cd (aircraft) + Cd (vehicle))

        = (0.5) * 1.225 * 335 * (5.556)^2 *(0.6 + 0.15)

         = 4750.47 N

Total force of the towing vehicle,

F = Fad + Frr (vehicle) + Frr (aircraft)

F = 4750.47 + 17658 + 83875.5

  = 106283.97 N

Power Required

P = F * V

  = 106283.97 * 5.556

  = 590.513 KW

The force and power of the towing vehicle carrying the aircraft are 106.283 KN and 590.513 KW respectively.

6)B) The rolling resistance model is:

The drag coefficient force model is:

Model to calculate force and power from the above forces is:

 

7) A)

Based on previous question, Force required to push/pull the aircraft = 106.283 KN

Power required is = 590.513 KW

Let us assume the radius of the tyre as  = 25 inches = 0.653m

Gear ratio = 8

Transmission efficiency (et) = 87%

Motor efficiency (em) = 95%

Then,

Torque required for the wheel (Tw) = Total force * Radius in meters

                                                                 = 106.283 * 0.653

                                                                  = 69.403KNm

Motor torque = wheel torque / (Gear ratio * et)

                         = 69.403 /(8 * 0.87)

                         = 9.9716 KNm

The required motor torque = 9.9716 / 0.95

                                                = 10.49642

The total power required by the motor considering all efficiencies = 590.513 /(0.87 * 0.95)                                      

                                                                                                                        =714.474KW

Let us assume the towing operation is done for 15 minutes  (0.25 hrs)

                                                             Total energy consumed = 714.474 * 0.25 = 178.6185 Kwh

Duty cycle (d ) = (Required power)/ (Rated power) = 714.474 / 950 = 0.752 = 75.2%

B)