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What is Vmc? 23.
calibrated airspeed at which, when the critical engine is inoperative, it is possible to maintain control and straight flight without exceeding an angle of 5 degrees
MAY NOT exceed 1.2Vs1 at max takeoff weight!
What determines Vmc? SMACFUM!!
Standard day at SLP Max power on operating engine Aft center of gravity Critical engine inop (prop windmilling) Flaps t/o, gear up Most unfavorable weight (lightest)
Recognizing Vmc (4) 1. loss of directional control
- stall warning horn
- buffeting before the stall
- decay of control
Recovering from Vmc 1. Reduce power on operating engine
- Pitch down
Things that cause a decrease in Vmc speed... 1. Anything that moves the CG forward (larger arm to rudder makes the rudder more effective)
more tail-down force which creates more drag (reducing Vmc speed)
- Anything that allows less rudder to be used (making it more available to the pilot)
i.e. less power, higher weight (more horizontal lift, less rudder required to oppose yaw)
Things that cause an increase in Vmc speed... 1. AFT CG (rudder less effective)
- Anything causing more rudder to be used (making it less available to the pilot)
i.e. more power, unfeathered prop (produces more drag as more rudder is needed), less weight (less horizontal lift, more rudder needed to oppose yaw)
Effects of density altitude on Vmc speed An increase in density altitude (temp/humidity increase or pressure decrease) means less thrust created by the engines, which means less rudder needed to oppose yaw
less rudder = more available to the pilot
SO Vmc speed decreases with higher density altitude!!
HOWEVER performance severely decreases with a higher density altitude (prop/wings have poor performance in creating thrust & lift)
All-engine service ceiling highest altitude where aircraft can maintain a steady climb of 100fpm at full power
All-engine absolute ceiling altitude where climb is not possible with both engines at full power
Single-engine absolute ceiling altitude where climb is not possible with one engine at full power, and the other propeller feathered
Single-engine service ceiling highest altitude where airplane can maintain a steady climb of 50fpm with one engine full power and the other feathered
Accelerate-stop distance runway required to accelerate to Vr or Vlof, experience an engine failure, and bring the aircraft to a stop
Accelerate-go distance distance required to continue the takeoff with an engine failure and climb to 50 AGL (assuming failure at Vr or Vlof)
Induced flow Caused by the wing mounted engines, which accelerate the air/slipstream over the wing
'Conventional Twins' twin engine airplanes with propeller rotating in the same direction
Torque as the engine/propeller rotate in one direction, they try to rotate the aircraft in another direction.
Newton's third law "for every action there is an equal and opposite reaction"
resulting yaw/roll from engine loss greater if LEFT ENGINE fails on a conventional twin
