Asymetric Flight Flashcards
Critical Engine
The engine that if it fails the other engines produces the most yaw
Clockwise rotating twin AC - Critical Engine
In clockwise rotating propellers the left engine failing would give the greatest yaw due to right engine having a greater moment arm from the cg
Asymmetric blade effect
What effects yawing moments for asymmetric flight
Density
Thrust setting
How far engines are from CG
Propeller drag (windmilling)
Outboard engines are always
The critical engine
Secondary effect of yaw in asymmetric flight if not stopped will be
Roll in the same direction as more lift on wing with live propeller (slipstream effect also)
What causes the unbalanced force after applying rudder in asymmetric flight
Drift is caused by the corrective rudder force which causes a diversion from flight path due to sideway force being generated
Wings level method
Or
Wings down method
Required
Wings Level Method
Using additional rudder to sideslip in opposite direction to the failed engine to create a side ware component of thrust
Wings Level Method - Advantages and disadvantages
+ Comfortable and more suitable for IMC (turn/slip coordinator are seated naturally)
- Not suitable for light twins as unable to generate enough force to overcome
- extra drag leading to more fuel needed
- higher AOA on fin risk of stalling
Banking Method
Creating a side ware component of lift to balance the weight by banking towards the live engine
Banking Method Advantages and Disadvantages
+Less drag therefore better performance
+ Better rudder authority less chance of thin stall
- Not used on large CAT AC
- increased risk of disorientation
- attitude indicator may re erect itself to a false datum
What is the limit of bank when using the banking method
5 degrees to prevent additional lift requirements to overcome the bank angle
Why is the left engine the critical engine on a clockwise prop
Due to the asymmetric blade effect which inclines the thrust line further to the right therefore yawing the ac left
Reinforced by the slipstream effect
Rolling left due to torque reaction
Where is it worst to have a crosswind from when you have an engine failure
Crosswind from dead engine will give you a weathercock effect yawing you into the wind further
Counter rotating propellers advantage
Do not suffer from slipstream or asymmetric blade effect
Although critical engine will still be the into wind engine
What do you need to consider on a go around with one engine
A much larger yawing moment when pitching up (gyroscopic effect) and asymmetric blade effect) + slipstream effect
Minimum control speed CS23
Vmc is the the minimum speed at which full deflection of the rudder can oppose the yaw
Factors which increase VMC
Crosswind from failed engine side
Lower altitude/cold temp (density/thrust)
Go around (idling to go around)
Higher AOA reducing margin of control
CS25 minimum control speeds
Vmca
Vmcg
Vmcl
Vmca + what happens to vmca when you bank
Minimum control speed at cruise altitude
Refer to directional control
Banking 2-5 degrees reduces rudder input therefore more contlability decrease VMCA
Vmcg
Minimum control speed on the ground
Must not deviate more than 30ft from centreline
Vmcl
Minimum speed to control yaw + minimum roll rate requirements
(Need to be able to manoeuvre ac to runway in roll)
20 degree roll within 5 seconds
Vmca vs Vmcg
Vmcg is greater as a smaller arm to rudder when on the ground (wheel assembly)
Vmcg will always be faster
Vmca must never exceed
1.13V
How is Vmca measured
Worst situations on T/O
Max thrust on operating engine
Most unfavourable CG position
Ac trimmed for TO
Max TO weight
Most critical takeoff config (without gear)
How is Vmcl Measured
Worst config on landing
Flaps etc
Wing level method will show a what to the turn indicator and slip indicator
Both will be neutral as wings are level and rudder input balances the yaw
If engine failures the secondary effect is to roll towards the dead engine further roll is increase by
The loss of lift behind the dead engine
Vmcl is determined under the following config
Landing Flaps and trimmed for all engines operating + gear down
Asymmetric blade effect descending
Up going blade on a clockwise propeller will produce thrust from the left side
Mass vs asymmetric flight
Greater the weight the greater the induced side slip and greater rudder effectiveness