Aerodynamics Flashcards
How do Counter rotating props help combat left turning tendencies?
The p-factor and torque from counter-rotating propellers cancel each other out which results in less rudder needed to oppose these tendencies.
What two things does the airplane do when an engine fails?
An aircraft with a failed engine will yaw and roll towards the dead engine due to asymmetric lift, thrust, and drag.
Why does the airplane yaw when an engine fails?
Asymmetric thrust will cause a yawing moment around the C.G. towards the dead engine.
Why does the airplane roll when the engine fails?
Accelerated slipstream (or induced flow) is extra lift created by air accelerated from an operating engine forced over the wing. There is a lack of this induced flow over the wing with the failed engine. This results in a rolling moment around the C.G. toward the inoperative engine.
How do you counteract the roll and yaw?
To counteract the roll and yaw, you must apply rudder towards the operating engine
What happens if you only use rudder to counteract the roll and yaw?
Just using rudder to maintain direction will put the aircraft into a sideslip, which introduces the fuselage to the relative wind creating a large amount of drag. We need to minimize this drag as much as possible while still maintaining heading. The solution is to improve performance by using a zero sideslip condition.
How do you maintain zero side slip in addition to using rudder?
When the aircraft is banked 2°- 5° toward the operating engine, the dihedral of the wing will create a horizontal component of lift. This will minimize the rudder deflection required to align the longitudinal axis of the airplane to the relative wind. With this bank, the appropriate amount of rudder deflection will be indicated on the inclinometer by the ball being halfway deflected toward the operating engine
Service Ceiling
This is the maximum density altitude where the best rate of climb airspeed (Vx) will
produce a 100 fpm climb with both engines at max continuous power.
Absolute Ceiling
This is the maximum density altitude that the airplane is capable of attaining or
maintaining at max gross weight in the clean configuration and max continuous power. As altitude
increases, Vx increases, while Vy decreases. Where these two speeds converge is absolute ceiling.
Single Engine Service Ceiling
- This is the maximum density altitude at which the aircraft can
maintain a 50 fpm climb with one engine operating at full power and one engine with a feathered
propeller. This is critically important, especially when flying over mountainous terrain. If the aircraft is
above the single engine service ceiling when an engine fails, it will slowly drift down to its single engine
service ceiling. This should be determined during flight planning using the single engine service ceiling
chart from the POH.
Single Engine Service Ceiling Example: Aircraft cruising altitude: 12,000’
MEA: 9,500’
Single engine service ceiling: 6,000’
Failure at 12,000’
If the aircraft has an engine failure at 12,000’, it will drift down to 6,000’. If you are IMC this could be
very bad. Always plan for an engine to fail! Choose a different route with a lower MEA.
Vyse
This is best rate of climb single engine. Vyse is identified by the blue radial on the airspeed
indicator. Always pitch for blue line when an engine fails. It will give you the best single engine
performance, although it may not be a climb. In the BE-76 Duchess, Vyse is 85 KIAS.
Vxse
This is best angle of climb single engine. If you have obstacles to clear with an engine failed, use
Vxse. Once the obstacles are cleared, pitch for Vyse. In the BE-76 Duchess, Vxse is also 85 KIAS
Vsse
This is the minimum speed at which an intentional engine cut can be performed. It gives a safety
margin from Vmc for safe engine cuts while training. MEI candidates need to know this. It is 71 KIAS in
the Duchess.
