250 or point 65

no no, I completely understand the definition of torque but this is not what we're talking about when we talk about torque as a turning tendancy. We're talking Newtons 3rd.

172, prop spins to the right...causes the aircraft to roll to the left. every action.

This is the Torque we're talking about with the prop on the operative side. Conventional turning props cause a roll to the left. The left engine is the one running, this is a good thing. If it's the right, thats a bad thing. This is the Torque effect we talk about when determining critical engine.

Torque, Pfactor, spiraling slipstream, accelerated slipstream

http://74.6.146.127/search/cache?ei=...p=1& .intl=us

Pretty good explanation (except that I'd argue that losing 50% of thrust leads to 50% loss in performance, not 80%)

ZnCrO4

Losing 50% of thrust will cause you to lose 80% perfromance is correct, simple power required vs power availible. Of course this is when you are takling about climb performance.

250 or point 65

Just something to smoke on here....it all depends on what you are comparing it to.

Gimme some numbers to quantify that you lose about 80% of performance when you are single engine. I don't have my seminole manual with me, but anyone mind looking up what kind of climb performance we'll get on a standard day and a hot day? two and single engine?

ZnCrO4

The baron will do 1650 fpm at sealevel isa at 5500 pounds with two engines
with one engine out this is reduced to 395 er so.

1650-395= 1255 fpm loss or 76percent loss of perfromance may not be 80 but a far cry from 50

250 or point 65

1) At some point that Baron will be able to maintain a negative climb single engine, right? How are you going to calculate that?

2) If performance isnt always positive, why do we compare the numbers to zero, shouldnt we be comparing them to performance with zero engines?

What does that Baron do with both engines out at best glide?

ZnCrO4

1) Whether the numbers are positive or negative they will work in the following example.

2) You have no performance with no engines, the power required curve will give you that info

I gave you the dumb down version but here is the real answer.

Any airplane has a power required curve and a best climb speed along that curve. Lets say that at what ever best climb speed is the power required translates to 180 horsepower for level flight in say a piper seneca. We can produce 220 horse power per engine meaning we have 440 HP total. We only need 180 HP to maintain the best climb speed while level. Now this means we have an extra 260 HP. What causes an airplane to climb? Excess power, in this case 260 HP extra. Now we lose an engine the power required to maintain the same speed does not change although the power available does. We still need the same 180 HP to maintain level flight and now only have 220 available meaning an excess of 40 HP.

260-40= 220 or a loss of 84% performance

It doesn’t matter whether the numbers are positive or negative you will still lose near 80% power due to an engine failure in a twin ….

250 or point 65

So are you equating performance to how much extra horsepower we have? I COMPLETELY understand your argument and that is the way I have always taught it (mostly because thats what the FAA wants to hear).

But what do you think of this?

I am talking climb performance. A seminole climbs at about 1800 ft/min 2 engines, 200 ft/min single engine, and -1700ft/min with no engines. Just because we have no engines does not mean we fall out of the sky. These numbers, when you compare 2, 1, and 0 engines, we lose about 50% of our climb performance.

DISCLAIMER: I am by no means an engineer or physics major. Don't go to your CFI and tell him that he's wrong because of some gospel you read on APC. This is just another way to look at it that I am putting up for discussion. This is not my own thought, its an idea brought up by a colleague that IS an engineer.

jungle

I think Tony was on to something with the wench theory. If you imagine yourself at the CG of a bar and a wench at some distance down the bar, she may look better further out. In this case she represents the tail, or rudder. As you move closer the situation may worsen increasing your VMCG until disaster strikes. The size of the wench really has nothing to do with it, it is more of a distance or eyesight thing. How much power you have consumed is also an important factor. As Archimedes once said: "Give me a wench long and graceful enough and I shall move the world."

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TonyC

You're fulcrum of it.






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The truth only hurts if it should.

Cubdriver

IMHO, Nickel chrome plated wenches are worth doing more calculations on. Just add a time factor into the VMCG moment arm and you will be amazed. I have seen some excellent torque values from nothing more than good moment arm.

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