Asymmetric flight- In balance or not?

[dances-with-clouds]

When asymmetric, 5 deg towards live and 1/2 ball on slip indicator.... Is this in balance? I always thought it wasn't but someone told me it is.... What's the reason?

Any feedback would be great!

Have thought about it a little more.

All rudder technique: There is a slip towards the dead engine meaning that the aircraft is out of balance even though the slip indicator is centred (lift and weight are vertically aligned).

All bank technique: There is side slip towards to the live engine meaning that aircraft is still not in balance and this is also shown on the turn and slip indicator (lift and weight not vertically aligned).

Using a combinationof the two means that the \'side slip towards the dead\' (all rudder) and \'side slip towards the live\' (all bank) tend to oppose one another. Consequently, the longitudinal axis of the aircraft is aligned with the direction of flight, so the aircraft must be in balance. The 1/2 ball slip is mearly an indication because lift and weight aren\'t vertically aligned.

How\'s that sound?

[Cloud Cutter]

Sounds pretty good to me, as you said - the longitudinal axis is aligned with the direction of flight - in balance. As you also said this IS a midpoint between the two extreme out of balance cases.

It would appear that you have answered your own question:ok:

[Milt]

Balance

All depends on YOUR or your derived definition of balance.

To most of us any aircraft in steady flight is balanced as all the forces acting produce steady straight progress through the air.

An asymmetric aircraft will have a steady sideslip and with wings level the "so called" balance indicator will be centre which is a false reading.

The determination of the sideslip angle for particular conditions is measured in flight test by a wind vane remote from the aircraft on a long pole out in front.

A string in the airflow in front of the cockpit will give a rough measure of the angle.

GPS accuracy now offers another simple means of measuring the sideslip angle.

[dances-with-clouds]

Thanks cloud and milt. It was one of those burning questions that I needed answered.

[Icarus2001]

To most of us any aircraft in steady flight is balanced as all the forces acting produce steady straight progress through the air.

Yes but you have dodged the question of what is "straight". It means that the tailplane (vertical stab) is following the same path as the nose through the air.

How do you use GPS to determine sideslip? Is there a wind correction?

[farqueue]

> When asymmetric, 5 deg towards live and 1/2 ball on slip indicator.... Is this in balance? I always thought it wasn't but someone told me it is.... What's the reason?

With one engine out, your thrust line is displaced toward the running engine. Combine that with your drag, still on the center line and you have a turning torque. You counter it with a boot full of rudder and drag. Drag and single engine are not nice to have together, so by banking we can
reduce the boot size and get some of the HP back to staying up.

The 5 and 1/2 are model/configuration dependant and will change, but are in the right ballpark.

[Cap 56]

Any time the vector sum of the forces and moments around CG is steady at zero you have a straight flight.

This does not imply the slipball is centered.

[Woodend1]

farqueue,

doesn't the total drag line also become displaced and move towards the dead engine due to the windmilling prop and loss of induced lift? This is where the assymetric turning moment arises from.

[Willie Nelson]

Keep in mind that while you have a half ball you not balanced in the same way that you are when flying a normal balanced turn as required by your instructor.

In all normal flying manoeuvres on a charter from A to B, assuming you are keeping the ball in the centre you should never have the sensation of being pulled left or right in your chair either straight and level or as you turn unless you are crossing up the controls for a landing. This is not the case with the ideal engine out performance. The dead engine is raised and the ball is half down to assist in maximising aerodynamic performance but not necessarily to make you comfortable. However, while you may or may night sense this leaning if you where to hang a pendulum from the roof you would see it. This is the same as the ball leaning out and where you to push it further out with rudder and hold it there you will notice that "bum out of balance" sensation.

So while this engine out set up IS aerodynamically ideal you need to be a little more careful when using the term balanced.


Willie

[amos2]

Don't get too technical here...It's all been worked out for you by the experts...and it works!

As dances says in his first sentence, if it feels in balance, then it is.

Just do it and don't complicate your life!! :rolleyes:

Keep it simple.

[john_tullamarine]

We should keep in mind that the 5 degree thing is associated with Vmca determination rather than routine OEI operation.

Generally, the target OEI bank will be in the 2-3 degrees range to minimise sideslip.

Common practice is to accept the slight climb degradation and fly wings level for simplicity and, in some cases, to avoid gyro systems problems at sustained small angles of bank.

[MAXX]

Dances with clouds,

Mate a very simplistic way of looking at it is also that remembering the kind of performance(or lack of) most light multiengine a/c have under an assymetric departure.
Any instructor with his salt would have demonstrated what happens if you dont use,3-5 and 1/2 ball out.(and lets face it we all observed the poor performance of poor technique during our early training in multi).In this situation as you are no doubt aware most light multi's not only wont climb,most will probabbly have a slight descent.(an obvious indication that the a/c is out of balance and not performing aerodynamically to its best).

[farqueue]

Woodend1, thrust line *MAY* be displaced. Asymetric does not always mean dead and windmilling, it could be low power, or zero thrust settings.

Thrust/drag, sides of a coin to a degree for this.

But, if it was dead and windmilling, yes there would be a big pile of drag out there as well adding even more turning moment to the misery.

[Woodend1]

let us pray for strength in them legs

[Oktas8]

I asked around about this issue some time ago, and the conclusions I came to, were as follows:

a) "In balance" means ball in the middle - the zero-bank case of asymmetric flight, with some slip present towards the dead engine.

** OR **

b) "In balance" means zero slip - the 2-3° angle of bank case, with the ball displaced towards the dead engine.

** OR **

c) "In balance" means all forces and moments about the c.g. cancel out.

Most experienced pilots I spoke to thought that b) sounded about right, being the accepted sense of "the most efficient way to operate an aircraft". I could find no textbook reference to this issue, so I too go with b).

BTW, option c) applies to an aircraft in a sideslipping steady descent with crossed controls - so that's not the best of the bunch!

cheers,
O8

[dances-with-clouds]

Willie

Have done a bit more research and must point out the important point that the slip indicator is really an inclinomitor comparing wing inclination to the load direction (in general terms). So 1/2 a ball doesn't necessarly mean out of balance.

[alf5071h]

See some of the papers here: asymmetric flight and asymmetric flight at low airspeed (http://uk.geocities.com/[email protected]/alf5071h.htm)
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