multiengine instrument: dead engine questions

[SPilot]

"wings level, ball centered"

The ball in the inclonometer shouldn't be centered when you have an assymmetrical thrust situation. You should try to fly the airplane with minimal side slip. With assymmetrical thrust, wings level and ball centered, the airplane will be slipping due to the operating engine pulling the airplane slightly sideways. Therefore you should compensate by putting the ball slightly (approx. 1/2 the ball width) into the operating engine (more rudder pressure). And also as widely known, bank 3-5 degrees into the operating engine to use the horizontal component of lift to counteract the rotational effect resulting from the assymmetrical thrust.

If you've ever done drag demos, you'll appreciate a noticable difference in performance when flying the airplane "wings level, ball centered" versus "sideslip eliminated, bank slightly into operating engine". Vmc changes also, because you're utilizing more sources of counter-forces to maintain directional control - not just the rudder.

The ultimate proof and expedient method of understanding this, is by attaching the yaw string to the windshield and try for yourself.

 

[UndauntedFlyer]

The ball in the inclonometer shouldn't be centered when you have an assymmetrical thrust situation. You should try to fly the airplane with minimal side slip. With assymmetrical thrust, wings level and ball centered, the airplane will be slipping due to the operating engine pulling the airplane slightly sideways. Therefore you should compensate by putting the ball slightly (approx. 1/2 the ball width) into the operating engine (more rudder pressure). And also as widely known, bank 3-5 degrees into the operating engine to use the horizontal component of lift to counteract the rotational effect resulting from the assymmetrical thrust.

If you've ever done drag demos, you'll appreciate a noticable difference in performance when flying the airplane "wings level, ball centered" versus "sideslip eliminated, bank slightly into operating engine". Vmc changes also, because you're utilizing more sources of counter-forces to maintain directional control - not just the rudder.

The ultimate proof and expedient method of understanding this, is by attaching the yaw string to the windshield and try for yourself.

Spilot: With all due respect, what you have written here is really not correct. First, when an engine fails it is most important to increase to full power, level the wings, center the ball and hold heading. The ball needs to be centered in order to be sure of just which engine has failed using the dead foot dead engine method. Allowing the ball to be displaced during this procedure can result in a misidentification of which engine has failed. Second, once the inoperative engine is determined and secured then the "zero side slip" technique may be used if you think that will enhance performance. Personally my experience is that the "zero side slip" technique doesn't do much of anything for performance but it does give your leg a rest. And finally, you have indicated that by attaching a yaw string to the windshield that this will show how important it is to use "zero side slip." This statement makes me wonder if you have ever really done this yourself or just looked at drawings in manuals. I have personally done this yaw string test many times and it really shows no difference in deflection with an engine out (feathered) and the ball centered or with the ball displaced half a ball width.

Placebo effect is a very powerful influence.

 

[nosehair]

When you're visual, it's natural to just react to the yaw, and I have no problem keeping my heading pegged.

Heading! Heading! Heading! The Heading Indicator is the instrument that replaces your visual of the nose. Heading is the most important instrument to control. Heading, altitude, & airspeed; those are the only 3 we have to control, and we should usually prioritize them in that order. If the Heading stays constant, the wings stay level. If the wings stay level, the altitude is more likely to stay level. In a constant power-constant pitch situation, the airspeed remains constant, so that reduces your scan to 2 instruments: Heading and Altitude.

The only point I'm making is that you should pay more attention to Heading.
The whole point of the Instrument Reference-Visual Reference method of learning to fly is that you should be attuned to automatically going to Heading Indicator when you lose visual reference to straight flight.

When you initially lose an engine, the heading change won't lie.
Sometimes, in turbulent air (natural or pilot imposed), the ball is bouncing around so that it can be confusing. Wait until you have stabilized Heading before you consult the ball.

 

[gkrangers]

In my limited experience, the yaw string does do a good job of displaying zero side slip.

 

[MauleSkinner]

In my limited experience, the yaw string does do a good job of displaying zero side slip.

...but unfortunately Undaunted's experience seems to override the rest of ours

Fly safe!

David

 

[clumpinglitter]

...but unfortunately Undaunted's experience seems to override the rest of ours

David

My instructor and I taped a yaw string to the Duchess the other day, but after we took off, it just hung down instead of going up over the windshield. I think the end of the string caught on something. Pissed me off.

-C.

 

[UndauntedFlyer]

In my limited experience, the yaw string does do a good job of displaying zero side slip.

I believe you will find that the yaw string does show yaw just as it is supposed to do. If you are flying with an engine inoperative and windmilling plus using bank and no rudder correction the yaw string will show lots of side-slip yaw. But if the failed engine is feathered (or set to zero thrust) and you're holding heading with the ball in the center or whether it's off one-half ball width while still holding heading, the displacement of the yaw string is almost nothing from one situation to the other and neither situation has the yaw string more aligned with the longitudinal axis than the other as can be seen.

 

[SPilot]

UndauntedFlyer, thanks for your reply.

I rest my case.

But I have tried it, and noticed better performance with 5 degree bank and offset ball, compared to wings level and ball centered.

I have however not tried to compare performance just with or without offset ball, using 5 degrees of bank in both cases.
And also with the string on the windshield, I've not attempted to look for any difference between ball centered and ball offset, but I have noticed significant difference on the string between banking and wings level.
On the Seneca I flew, the string was sort of "sticky" because of moisture combined with dirt and bugs on the windshield, so it was difficult to see small differences (it took a large change in yaw to convince the string to rip loose and move).

In any case, the minor difference in performance is not all that interesting during practical flying. I'm probably not able to fly the airplane with such extreme precision during an emergency anyway.

 

[UndauntedFlyer]

I have not tried to compare performance just with or without offset ball.

That is the whole point of the yaw string test and your instructor didn't do it?

Of course the 5 degrees of bank would only be along with the ball at half-scale deflection. And that would be compared with the ball centered and the wings almost level level or the airplane would be turning. And in this test you will see that there is no measurable change in the yaw string. The point being that zero side slip is not all that it is supposed to be in terms of greatly reduced drag. In reality all that it will do is give your leg a rest. The performance enhancements are minimum if they can be seen at all.

Personally, I file all reports of greatly enhanced performance as a result of "zero side slip" configuration under the title of placebo effect.

 

[gkrangers]

I believe you will find that the yaw string does show yaw just as it is supposed to do. If you are flying with an engine inoperative and windmilling plus using bank and no rudder correction the yaw string will show lots of side-slip yaw. But if the failed engine is feathered (or set to zero thrust) and you're holding heading with the ball in the center or whether it's off one-half ball width while still holding heading, the displacement of the yaw string is almost nothing from one situation to the other and neither situation has the yaw string more aligned with the longitudinal axis than the other as can be seen.

I can't be positive as its been over a month since I've done this now, but I do know at times there would be a considerable difference between ball centered and setting up for zero side slip, in our Duchess.

Could depend a lot on the airplane and the way the string is attached perhaps.

I know you have far more experience than I, just stating what I've observed.

I'm not talking performance differences, just centering the string along the longitudinal axis of the aircraft.

 

[nosehair]

Keep in mind that a small, insignificant performance improvement in a small training airplane may convert to a larger, more impressionable performance improvement in a larger engine airplane.

 

[minitour]

Keep in mind that a small, insignificant performance improvement in a small training airplane may convert to a larger, more impressionable performance improvement in a larger engine airplane.

...and sometimes a small, insignificant (100fpm) performance improvement in a small training airplane may be the difference between a controlled crash and staying airborne.

-mini

 

[gkrangers]

...and sometimes a small, insignificant (100fpm) performance improvement in a small training airplane may be the difference between a controlled crash and staying airborne.

-mini

I would call 100fpm significant. Anyone know, lets say on average or at standard atmosphere how much improvement zero side slip gives in a Duchess, Seminole, or anything really ?

 

[A Squared]

Personally, I file all reports of greatly enhanced performance as a result of "zero side slip" configuration under the title of placebo effect.

Ummm yeah, it's just "placebo effect" RIghty, last time we discussed this, the guy who was a Navy Test pilot, the one who had actually done extensive test profiles on this, with a highly instrumented aircraft, and his systematic, carefully measured flights under controlled conditions showed a significant increase in climb (not sprctacular, but significant) yeah that was probably "placebo effect"

OK, undaunted, I'm going to get personal here for a moment.

Look. You bring a lot of good things to this forum, a great deal of experience, an enthusiasm for General Aviation, the perspective of an actual examiner, and you've sparked some interesting discussions. That's all good. But for some reason, you have a bug up your a$$ because you think the zero sideslip concept is a myth. That's fine as far as it goes. I, like you, believe that dogma should be challenged, and I'll be the last to claim that everything in an FAA text is true. However there comes a time to admit that you are in fact wrong. The time for you to admit that you are wrong was when a trained, navy test pilot showed you from his flight test records in GA twin with test instrumentation that the zero sideslip concept actually *DID* yield performance improvements. Yet, unbelievably, you insist that there is no value to "zero sideslip" that it's all "placebo effect" .

I gotta ask, what is wrong with you? why do you keep tilting at this windmill when you've been shown to be wrong? Do you think that your casual dicking around in a duchess with a string tied to the windshield is more accurate than a trained test pilot flying specially instrumented aircraft through a carefully planned test sequence? Or are you just so convinced of your omniscience and omnipotence, that nothing anyone says or does (even trained test pilots) will make any difference to you?

Sorry for getting personal. Like I said, I do think you contribute some positive things to this forum, but your "just say no to zero sideslip" campaign is not a positive contribution.


FOr those of you scratching your heads wondering what the deal is here, take a look at this thread.

http://forums.flightinfo.com/showthread.php?t=74012

Take a look at Skiddriver's posts. He's the test pilot. Notice how Undaunted goes from saying that performance increases from zero sideslip is a myth at the begining of the thread to conceding that the performance improvements exist. Now, for some reason he's back to insisting that they are due to "placebo effect" I don't get it. All I can say is that I would point out to Undaunted Flyer that this foolishness undermines his credibility on other subjects.

 

[Metro752]

i woulda failed my multi checkride if Al was my DE. i was flying around half the checkride in a zero side slip condition