M8.3 Flashcards
(25 cards)
What will happen if two aircraft have the same lift-to-drag ration, but weight differently, begin gliding from the same altitude?
Both aircraft will cover the same distance, but the heavier aircraft will be flying at faster airspeed to maintain the same LD ratio. (Water ballast in gliders) Therefore it will arrive first.
What forces need to be equal to maintain straight and level flight?
Thrust/drag, weight/lift, as well as the moment of the aircraft.
What is the aerodynamic centre?
The point at which the coefficient of lift is constant, even during changes in pitch attitude.
Where is the aerodynamic centre commonly located?
25% of the chord from the leading edge.
What are the 9 primary factors that are affected by aircraft performance?
- Take off/landing distance
- Rate of climb
- Ceiling
- Payload
- Range
- Speed
- Manoeuvrability
- Stability
- Fuel Economy
What is load factor measured in and representative of?
Load factor is measure in ‘g’ and is representative of the load on the aircraft structure.
What are limit load factors?
Limit load factors are the highest load factors that an aircraft can experience without structural damage.
What is the usual aircraft design rule for ultimate structural limits to be?
Ultimate structural limit is usually 150% of the structural limit.
How are aircraft structural limits selected?
Aircraft structural limits are selected to ensure that g-loading induced flex will not damage the airframe or shorten its design life.
When might the selected structural limits be different from the standard expected?
If there are concerns about airframe lifetime.
What do aeroelastic limits define?
The maximum operating speeds, also know as “redline airspeed”.
What are lift augmentation systems?
They are devices installed on the wing of an aircraft to produce an increase in the lift at a given airspeed.
What are the 3 key lift augmentation devices?
- Flaps
- Slats
- Boundary layer control
What are the 4 different types of trailing edge flaps?
- Plain flap
- Split flap
- Slotted flap
- Fowler flap
What is a plain flap?
Basic flap design that is hinged to the wings trailing edge and pivots down when extended. This changes the wings curvature, increasing flow separation, creating a larger wake and drag. Allows pilots to fly a steeper angle on approach.
What is a split flap?
Fixed upper park is an extension of the top trailing edge of the wing while the lower part pivots down from its hinges. Similar drag producing characteristics to the plain flap but provides higher levels of lift.
What is a slotted flap?
Designed with a gap between the wing and the flap, allowing high pressure air beneath the wings to flow, reducing separation levels while increasing lift. Reduces drag while increasing lift.
What is a fowler flap?
Most common type of flap on modern aircraft. Installed in sections on the upper wing surface and extend on tracks before dropping to increase both chord and camber. Can also feature slots between flaps. Allows multiple stages of extension.
What are Kruger flaps?
Kruger Flaps are high lift tools fitted to the leading edge . They deploy downwards and forwards, increasing a wings camber. They are often found on swept wing airliners
What are leading-edge cuffs?
Leading-edge cuffs are fixed aerodynamic devices that extend the leading edge downward and forwards, causing the airflow to attach better to the upper surface of the wing at higher angles of attack, thus lowering the aircraft’s stall speed. The fixed nature of these extracts a penalty in max cruise speed.
What are slats?
Slats prevent flow separation by supplying more energy to the boundary layer. It’s is a small auxiliary aerofoil that extends forwards, increasing camber and forming a slot. The boundary layer is re-energised by the increased camber and accelerated air from the slot.
What are vortex generators?
Vortex Generators take the form of metal projections form the wing surface. The aim of these are to pull high energy air from the free-stream to overcome the ‘adverse pressure gradient’ on the trailing part of the wing, which delays the boundary layers separation.
What are slots?
Slots are similar to slats, however they are fixed in aircraft that require a lower stall speed and good low speed handling. They are span-wise gaps in the wing that allow air to flow from the lower to upper surface. Insignificant impact, impart from more drag, at low speeds.
What are winglets?
Winglets are small upturned structures on the end of an aircraft’s wings. The use of these leads to the splitting of wingtip vortices, which reappear in a smaller form, with lower rotational speed and less kinetic energy(less induced drag) at the winglet tip. There is also a small forward lift component due to the relative airflow over the winglet.
