Critical engine

[unreal]

Okay, I have a bit of a situation. A friend of mine is going through his MEI training at the moment, and I was trying to help him study. My question: "Name the four things that make an engine critical." He named three: p-factor, torque, accelerated slipstream, but I contend that he's missing one more: spiraling slipstream.

I know I've seen the reference to "spiraling slipstream" as a factor that makes an engine critical, but like a big idiot, I can't find that reference. Any help, or am I just insane?

 

[KeroseneSnorter]

Kersheners (sp?) books have it in there.

I thought it was in the Faa's test prep as well, at least it was way back when. I know I had to spit it out to the DE when I took the Multi and MEI rides.

 

[User998]

You are correct. According to Paul Craig's "Multiengine Flying" (arguably the bible for initial multi students), on pages 21-24, it lists and details the four items which make an engine critical.

Below are the notes directly from my MEI Lesson Plans folder:

-Four Things That Make An Engine Critical

P-Factor
·Descending blade produces more thrust that the ascending blade.
·Descending blade on right side will have longer thrust arm, then the descending arm on the left engine.
·The yaw produces by the loss of the left engine will be greater that yaw produced by the loss of the right engine, making the left engine more critical.

Spiraling Slipstream
·Left engine’s slipstream hits horizontal stabilizer, counteracting the yaw caused by the loss of the right engine.
·Right engine’s slipstream too far out to hit stabilizer, and is unable to counteract the yaw caused by a left engine failure.

Accelerated Slipstream
·P-Factor causes longer arm to the centerline of thrust of the right engine, that then left. The centerline of lift is also farther out on the wing, resulting in a greater rolling tendency with the loss of the left engine.
·Rudder is more effective with the left engine running. (Slipstream)

Torque
·For every action, there is an equal and opposite reaction.
·Since props turn clockwise, the aircraft tries to roll counter-clockwise.
·If you lost the right engine, the aircraft will yaw right but roll to the left, thereby canceling each other.
·If we lose the left engine, the aircraft will yaw left and roll left , into the dead engine.

 

[gkrangers]

Well think about it...the loss of the spiraling slipstream from the critical engine will hurt control...

PATS.

CMEL ride this Saturday....

 

[unreal]

Cool, thanks. His school doesn't teach it that way, so my word alone isn't going to sway him (and really, it shouldn't). I'll check out that book, thanks.

 

[FL420]

Spiraling Slipstream
·Left engine’s slipstream hits horizontal stabilizer, counteracting the yaw caused by the loss of the right engine.
·Right engine’s slipstream too far out to hit stabilizer, and is unable to counteract the yaw caused by a left engine failure.

Horizontal or vertical stabilizer?

Accelerated Slipstream
·P-Factor causes longer arm to the centerline of thrust of the right engine, that then left. The centerline of lift is also farther out on the wing, resulting in a greater rolling tendency with the loss of the left engine.
·Rudder is more effective with the left engine running. (Slipstream)

What is this centerline of lift?

 

[MauleSkinner]

I always thought the one that quit was the critical one...it definitely has more negative impact on performance than the one that's still running

Fly safe!

David

 

[Holding Short]

Horizontal or vertical stabilizer?

Well... if you sit there long enough without doing something about that failure, it will be vertical.

HS

 

[kevdog]

I always thought the one that quit was the critical one...it definitely has more negative impact on performance than the one that's still running

Fly safe!

David

I always thought the one still turning was critical, since if it fails, you are SOL.

 

[UndauntedFlyer]

Personally, I think that except for P-factor and maybe torque reaction to a degree, the rest is a bunch of crap and of very little significance.

The only thing an applicant should be responsible for on an FAA test on this subject is what is in the POH or the Airplane Flying Handbook (AFH). Paul Craig is not listed as a reference source for any task in the PTS for anything.

If the examiner wants that info too, he is overstepping the line of fairness.