Critical engine

[King Air]

Hi guys,

Recently, a friend of mine asking me how to determine which is the critical engine on BE-76 and Baron?
Appreciated for any explaination!:)

[Noggin]

You could try reading the Aircraft Manual.

If the engines are counter rotating there will be no critical engine. I believe this applies to all BE76 models.

If the engines both rotate in the same direction, typically clockwise viewed from behind, the critical engine will be the left (Port) engine

[Angle of Attack]

Or technically in a BE-76 the critical engine would be the upwind engine when taking off in a x/wind. Although I'd regard any engine failure in a duchess as "Critical" regardless of which engines!

[The Greaser]

Critical Engine : That engine which if fails will most adversely affect control of the aeroplane.

In the Dutchess and Baron, which both have props rotating in a clockwise sense, the critical engine is the left engine.

Explanation : Primarily due to P-Factor, the thrustline from both props does not go through 'the center' of the engine, but rather is displaced toward the descending blade, particularly at high angles of attack (basic PPL theory). Hence the thrustline of the left engine is closer to the longitudinal axis of the aircraft than the thrustline of the right engine. Hence if the left engine quits then the yawing moment is greater than if the right engine quits.

Torque, and slipstream also play a part in the discussion, but as I said, P factor is the major factor.

[Noggin]

Its actually due to asymmetric blade effect which the Americans call P-factor.

[YouNeverStopLearning]

All this talk about critical engine is a misnomer.

This is because all the V speeds and emergency proceedures for twins are based on a stated case situation which includes the assumption that the engine that has failed is the critical engine. If the other one fails you have something small in hand, BUT DONT TRY TO REMEMBER WHICH IS WHICH, FLY THE AIRCRAFT.

So as long as you fly the way the whole manual INSTRUCTS you to, it doesn't matter which engine has failed. Except from your trousers point of view.

Read the manual.

[IRRenewal]

In the Dutchess and Baron, which both have props rotating in a clockwise sense, the critical engine is the left engine.

Gosh, I always thought the Duchess had counter rotating engines. You learn something new every day :).

[Tinstaafl]

Counter rotating in the BE76 Duchess

Clockwise for both engines in the Baron & Travelair

[The Greaser]

Tinstaafl,

Thanks for clearing that up - I knew the baron had standard props, wasn't quite sure about the dutchess.