AC-SYS
AC-SYSTEMS, Manfriani: AC-Structure, the Landing Gear, Propulsion System (Propellers, Piston Engines, Turbine Engines),....
AC-SYSTEMS, Manfriani: AC-Structure, the Landing Gear, Propulsion System (Propellers, Piston Engines, Turbine Engines),....
In a tension test, what does the constant E mean?
E is the normal modulus of elasticity or Young's modulus.
In an AC wing, the cross sectional area of the web carry all the
The web carries most of the
The torsion loading on a trapezoidal wing section with no sweepback is maximum at
The local aerodynamic heating at stagnation point is
The hottes part of an AC flying at supersonic speed is
At low speeds the load factor is limited by
At high speed, the limit is set by
- What are the load factor limits for the Pilatus-21 turboprop trainer?
- For the Lockheed Martin F-22 Raptor jet fighter?
- +8/-4
- +9.5/-3.5
- How is the load factor increment when encountering vertical gust defined?
- What does this equation tell us?
- \(delta n=delta L/(m*g)=Kg*(rho*U*V*CLalpha)/(2*m*g/S)\)
- The AC sensitivity to gust is a function of wing loading (2 m g/S), lift curve slope (cL alpha-->depends on wing aspect ration), flight altitude and airspeed.
How do AC actually react to vertical gust?
They accelerate upwards, so the net gust velocity is reduced.
How do Airworthiness specifications define the gust velocities to determine load factors due to turbulence?
They define the standard gust velocities (in equivalent airspeed).
The AC weight influences loads on the AC structure. What kind of loads are these?
- Fuselage bending
- Wing bending
- Shear loads
- Tailplane loads
How do airworthiness regulations limit the minimum MLW for the PC-12?
95% of the MTOW--> the AC must be able to land immediately in case of engine failure and cannot dump fuel in emergency.
For multi engine AC equipped with a fuel jettison system, a lower MLW can be specified.
- What is the MZFW critical for?
- What is the MRW critical for?
- The MZFW is critical for wing bending and shear at the limit load factor-> fuel weight alleviates these loads
- The MRW is critical for rolling, towing, braking loads on ground
- What weight does the MZFW limit?
- What does it mean to keep the MZFW balanced with the MTOW?
- The payload weight that can be carried. The MZFW should be as high as possible, while staying in balance with the MTOW.
- This means that the wing bending and shear at the limit load factor should be approximately the same at MTOW (with full tanks) and at MZFW.
What defines the zoning system in the ATA-100 specification?
The zoning system is specified to simplify the location of parts in modern large transport AC.
How many hierarchies of AC zones are defined?
3: Major zones, Intermediate zones, Minor zones
- What do odd numbers in the AC zoning system indicate?
- What do even numbers indicate?
- Odd numbers mark the zones of the left side
- Even numbers zones on the right side of the AC, as seen by the pilot.
What can the skin of the AC's fuselage be made of?
Fabric, plywood (Sperrholz), thin metal sheet or synthetic materials.
Layout of a tricycle undercarriage:
How much should the pitch angle Θ be at which the tail touches the ground?
10-15°
How much should the roll angle be for large transport AC and for light AC?
- at least 8° for large transport AC
- 15° for light AC
Which two limit angles define the required length of the main landing gear legs?
Ground pitch and roll angles
What loads should be on the nosewheel of the AC?
8-15% of the AC weight
For a general aviation or commuter AC, what maximum value of lift can be assumed for design and testing?
2/3 of the AC weight
On which value does the vertical speed at touchdown depend?
On the efficiency of the shock absorber.
What is the safety margin of a stroke?
2.5cm
What is a typical value for the internal gas pressure p0 of AC oleo shock absorbers under static load?
1800psi (12.5 MPa)
What is shimmy and why can it occur?
Shimmy is high speed vibration of the nose wheel and can occur because of the wheel imbalance, tire wear or free play in the wheel suspension mechanism. A hydraulic damper (shimmy damper) must be fitted.
What is the typical lifetime of a wheel?
300-400 landings
Propeller efficiency:
A short take off AC with a low cruise speed will certainly benefit from a...
...large propeller providing high efficiency and high thrusts at low speeds.
For a fast AC,....
....a smaller propeller diameter will be more suitable.
Which peak efficiencies reach modern variable pitch propellers?
0.85-0.9
What describes feathering?
In the event of an engine failure, propeller pitch must be set to a value that reduces drag to a minimum. (90°)
Fuel Systems:
Fuel tanks:
How much weighs the fuel mass in an AC (except for small general aviation AC)?
25-50% of the MTOM
Fuel pumps:
What are transfer pumps?
Transfer pumps move fuel between tanks to maintain mass balance and to supply fuel to the collector ranks from where fuel is drawn to feed the engines.
What are booster pumps?
Also called engine feed pumps. They are used to boost (antreiben) the fuel pressure in the engine feed lines.
Another reason is to prevent cavitation (vapour bubbles) at high levels.
Valves:
What is the function of shut-off valves?
Shutting off fuel when required, preventing fuel transfer from one rank to another.
What are the functions of refuel and defuel valves?
Filling the tanks to allow flow from the refueling gallery to the fuel tanks, or from the tanks to the refueling gallery during defueling (emptying the tanks for maintenance)
Cross-feed valves?
Shifting fuel from one side of the AC to the other side.
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Flashcards
Layout of a tricycle undercarriage:
How much should the pitch angle Θ be at which the tail touches the ground?
10-15°
How much should the roll angle be for large transport AC and for light AC?
- at least 8° for large transport AC
- 15° for light AC
Which two limit angles define the required length of the main landing gear legs?
Ground pitch and roll angles
What loads should be on the nosewheel of the AC?
8-15% of the AC weight
For a general aviation or commuter AC, what maximum value of lift can be assumed for design and testing?
2/3 of the AC weight
On which value does the vertical speed at touchdown depend?
On the efficiency of the shock absorber.
What is the safety margin of a stroke?
2.5cm
What is a typical value for the internal gas pressure p0 of AC oleo shock absorbers under static load?
1800psi (12.5 MPa)
What is shimmy and why can it occur?
Shimmy is high speed vibration of the nose wheel and can occur because of the wheel imbalance, tire wear or free play in the wheel suspension mechanism. A hydraulic damper (shimmy damper) must be fitted.
What is the typical lifetime of a wheel?
300-400 landings
Propeller efficiency:
A short take off AC with a low cruise speed will certainly benefit from a...
...large propeller providing high efficiency and high thrusts at low speeds.
For a fast AC,....
....a smaller propeller diameter will be more suitable.
Which peak efficiencies reach modern variable pitch propellers?
0.85-0.9
What describes feathering?
In the event of an engine failure, propeller pitch must be set to a value that reduces drag to a minimum. (90°)
Fuel Systems:
Fuel tanks:
How much weighs the fuel mass in an AC (except for small general aviation AC)?
25-50% of the MTOM
Fuel pumps:
What are transfer pumps?
Transfer pumps move fuel between tanks to maintain mass balance and to supply fuel to the collector ranks from where fuel is drawn to feed the engines.
What are booster pumps?
Also called engine feed pumps. They are used to boost (antreiben) the fuel pressure in the engine feed lines.
Another reason is to prevent cavitation (vapour bubbles) at high levels.
Valves:
What is the function of shut-off valves?
Shutting off fuel when required, preventing fuel transfer from one rank to another.
What are the functions of refuel and defuel valves?
Filling the tanks to allow flow from the refueling gallery to the fuel tanks, or from the tanks to the refueling gallery during defueling (emptying the tanks for maintenance)
Cross-feed valves?
Shifting fuel from one side of the AC to the other side.
Non-return valves or check valves?
To preserve the fluid logic of the system, preventing fuel from flowing in the reverse sense.
Hydraulic systems:
In which four stages can hydraulic systems be subdivided?
- Generation (pumps pressurize a fluid)
- Control (valves control energy or pressure delivery)
- Transfer (pipes distribute energy to all necessary areas of the vehicle)
- Utilization (conversion onto mechanical energy)
What are accumulators?
Pressurised fluid storage units for short emergency operation of branches or single components of the hydraulic system;
damping of pressure fluctuations (ripple accumulators)
AC Systems Groups:
I which three groups can an AC be subdivided?
- Airframe
- Engines
- Systems
What is the purpose of the airframe? How is it also called?
The airframe is a complex and integrated set of structural components that supports the mass of systems and passengers and carries loads and stresses. This is also known as the “platform”.
What is the purpose of the vehicle systems (general or utility systems)?
It enables the aircraft to fly safely and provide an adequate environment for the crew and passengers.
What is the purpose of the avionic systems?
The avionic systems provide information, control and communication functions that enable the aircraft to fulfil its operational role.
In which parts can the system "aircraft" be subdivided?
- Core
- Essential
- Auxiliary functions
What is the total AC function composed of?
- Flight control system (FBW)
- Engine control system (FADEC)
- Hydraulic system (motive power for the actuators that move the control computers)
- Electrical system (electrically driven hydraulic pumps)
- Attitude system (Pitch, yaw, roll angles, rates and accelerations)
- Air data system (airspeed, altitude, air temp.,rate of climb or descent information)
Which systems of an AC have strong physical integrations?
Strong physical integration:
- Structure (airframe) + Vehicle systems
Which systems of an AC have information based intergration?
Information based integration:
- Vehicle systems + avionic systems + mission systems
Information based integration: On which network is the information integration mainly based?
Much of the integration is based on data bus networks.
How many heat exchangers exist in an AC? (Physical interaction between systems)
8
Explain all eight heat exchanger systems.
1. air extracted from the engine fan casing is used to cool bleed air tapped off the intermediate or high pressure compressor (depending upon engine type);
2. air is used to cool engine oil in a primary oil cooler heat exchanger;
3. fuel is used to cool engine oil in a secondary oil cooler heat exchanger;
4. the electrical integrated drive generator (IDG) oil is cooled by air;
5. the hydraulic return line fluid is cooled by fuel before being returned to the reservoir;
6. aircraft fuel is cooled by an air/fuel heat exchanger;
7. ram air is used in primary heat exchangers, the air conditioning pack, to cool entry bleed air prior to entering the secondary heat exchangers;
8. secondary heat exchangers further cool the air down to temperatures suitable for mixing with warm air prior to delivery to the cabin.
What is the definition of a system?
System: A combination of parts, components, facilities, procedures, personnel, skills... that are connected in an organized way to perform one or more functions.
What is the definition of function?
Function: The lowest level of a specific action of a system, equipment, and flight crew performance on the airplane.
What is the definition of failure?
Failure: The inability of a system, subsystem or component to perform a function as intended: functional failure.
What is the defintion of failure condition?
Failure condition: A condition resulting from one or more failures that affects the aircraft and its occupants, depending on the relevant operational and environmental conditions.
What are essential functions?
The functions whose loss would reduce the capability of the aircraft or its crew to cope with adverse operating and environmental conditions are commonly indicated as essential functions (for instance, a loss of cabin pressurization or a loss of the anti-icing system).
What is the definition of a critical function?
If the loss of a function could cause the loss of the aircraft or fatal injuries to the occupants, it is called a critical function (for example, a complete loss of engine power).
