Ball Centered for coordinated turn right!?!

[Shadrach]

2 hours ago, PT20J said:

Light piston twins generally do not have much performance on a single engine. Flying with zero sideslip versus ball centered can often be the difference between a small ROC and a descent. Jets have a lot of excess thrust and, in the case of tail-mounted engines, not much yaw on a single engine.

Skip

I do not have a MEL rating and my only twin experience is decades behind me in a C421, but I am trying to simplify this concept for my own understanding.  Would it be accurate to say that when a propeller driven twin being propelled by a single engine is in coordinated level flight, its yaw axis is displaced from the aircraft's trajectory (heading vs track)?  And therefore the primary reference instrument (TC) is no longer accurately depicting coordinated flight?  And furthermore that a control input that would center the ball will result in a side slip and increased drag?

[EricJ]

22 minutes ago, Shadrach said:

I do not have a MEL rating and my only twin experience is decades behind me in a C421, but I am trying to simplify this concept for my own understanding.  Would it be accurate to say that a propeller driven twin being propelled by a single engine is in coordinated level flight, its yaw axis is displaced from the aircraft's trajectory (heading vs track)?  And therefore the primary reference instrument (TC) is no longer accurately depicting coordinated flight?  And furthermore that a control input that would center the ball will result in a side slip and increased drag?

Pretty much.    Essentially the system is highly asymmetric with one engine providing thrust and the other just making drag, so any hope of symmetric operation (i.e., flying straight with the ball centered and no slip) is not going to happen.    You can fly the airplane with the wings level and the ball centered, but the drag will be higher than if you raise the dead engine a bit and fly with the ball not centered.   The performance will generally be sucking, and you'll be looking for a place to go to not die, so getting rid of that drag is very useful.

In that condition, flying in a straight line with the dead engine raised, the ball will be at the bottom of the inclinometer relative to the ground, so, one could say it is "pointing straight down", even though it is not in the center of the inclinometer.  That seems to me like an odd way of describing it, though.   

[jaylw314]

Never flown multis, but from the "Pilot Flying Handbook" :

This results in the ball being uncentered (to the right in this case) despite the both rudder and aileron in the same direction (right), with no slip and no heading change.

I'm sure helicopter pilots will chime in and point out that in straight coordinated flight, the ball is also uncentered for similar reasons due to the tail rotor.

Edited November 4, 2022 by jaylw314

[PT20J]

2 minutes ago, jaylw314 said:

Never flown multis, but from the "Pilot Flying Handbook" :

I assume this would result in the ball being uncentered (to the right in this case) despite the both rudder and aileron in the same direction, with no slip and no heading change.

That is exactly what is depicted in the upper right inset of the right drawing. The little bar under the bank angle pointer is the slip/skid indicator on a G1000 and it is depicted as being a "half ball" to the right.

A good exercise is to tape a piece of yarn to the windshield which creates a very sensitive slip/skid indicator and note the bank angle and rudder deflection that results in a constant heading with zero sideslip.

The exact same effect happens in  helicopters where the antitorque (tail) rotor provides a side force that must be countered by a tilt of the rotor disk.

Skip

[jaylw314]

1 minute ago, PT20J said:

That is exactly what is depicted in the upper right inset of the right drawing. The little bar under the bank angle pointer is the slip/skid indicator on a G1000 and it is depicted as being a "half ball" to the right.

A good exercise is to tape a piece of yarn to the windshield which creates a very sensitive slip/skid indicator and note the bank angle and rudder deflection that results in a constant heading with zero sideslip.

The exact same effect happens in  helicopters where the antitorque (tail) rotor provides a side force that must be countered by a tilt of the rotor disk.

Skip

LOL, I've never used anything other than a steam gauge turn coordinator, so I didn't register what that was showing until you pointed it out 

[PT20J]

13 minutes ago, jaylw314 said:

LOL, I've never used anything other than a steam gauge turn coordinator, so I didn't register what that was showing until you pointed it out 

I always hated that little thing. I was glad that Garmin put a depiction of a traditional ball under the attitude indicator the G3X.

[Pinecone]

2 hours ago, PT20J said:

I always hated that little thing. I was glad that Garmin put a depiction of a traditional ball under the attitude indicator the G3X.

And the G5.

I agree that that little thing is worthless on the G1000 and the Aspen PFD 1000

[EricJ]

3 hours ago, PT20J said:

I always hated that little thing. I was glad that Garmin put a depiction of a traditional ball under the attitude indicator the G3X.

Actual ball inclinometers are dirt cheap and require no maintenance and no power to run!   The big mystery to me is why every panel doesn't have one, regardless of the glass quantity.

[carusoam]

20-30 bucks for inclinometers…

I found the price, while looking for the word…

and they can be used to level your 4X4 or a camper or a boat…

Like a compass, they are liquid filled… and require no electrons…

 

-a-