Multi Engine OEI with Autopilot

[hish747]

Hi All,
I'm embarking on adding a multi-engine land to my commercial SEL and one thing I haven't yet seen is the effect on autopilot on engine out handling and procedures. What happens if you are in cruise with the autopilot engaged and maintaining heading and altitude and you lose one engine? Does the autopilot attempt to compensate for the asymmetrical thrust? Does it make it easier or harder to deal with OEI? Does it take longer to recognize that an engine has failed or is losing power?

 

[MauleSkinner]

Generally the autopilot will input roll to compensate for the yaw. Obviously that’s not a correct input, but it’s pretty obvious (at least in my opinion) what’s happening.

 

[Fearless Tower]

There is a video somewhere of a guy demonstrating it in a Baron. Put it on Autopilot and then shut down an engine.

It was a non-event. The A/P compensated for the asymmetrical thrust without any problem.

This was obviously done in cruise and not during a takeoff.

 

[Doc Holliday]

Hi All,
I'm embarking on adding a multi-engine land to my commercial SEL and one thing I haven't yet seen is the effect on autopilot on engine out handling and procedures. What happens if you are in cruise with the autopilot engaged and maintaining heading and altitude and you lose one engine? Does the autopilot attempt to compensate for the asymmetrical thrust? Does it make it easier or harder to deal with OEI? Does it take longer to recognize that an engine has failed or is losing power?

What airplane? What autopilot?

 

[Radar Contact]

Hi All,
I'm embarking on adding a multi-engine land to my commercial SEL and one thing I haven't yet seen is the effect on autopilot on engine out handling and procedures. What happens if you are in cruise with the autopilot engaged and maintaining heading and altitude and you lose one engine? Does the autopilot attempt to compensate for the asymmetrical thrust? Does it make it easier or harder to deal with OEI? Does it take longer to recognize that an engine has failed or is losing power?

I’ve been meaning to do this and film it. Not that it helps you right now but I’ll do that and get it up after I pick the plane up from getting painted.

I think it very much depends on the plane and autopilot combination. Not all autopilots are created equally.

 

[Clip4]

Most APs are two axis, no yaw correction.

 

[Tantalum]

Great question

 

[mondtster]

There is a video somewhere of a guy demonstrating it in a Baron. Put it on Autopilot and then shut down an engine.

It was a non-event. The A/P compensated for the asymmetrical thrust without any problem.

This was obviously done in cruise and not during a takeoff.

I've done it in a B55 with an old CIII autopilot just to see what it would do. In that airplane it worked fine and could be a good way to reduce workload in some situations. I wouldn't want to try it for the first time in a real engine out situation though, this is something I'd try in controlled conditions for the first time and something I'd do in any twin I intended to fly much as long as there isn't a limitation saying you can't.

 

[hish747]

I've done it in a B55 with an old CIII autopilot just to see what it would do. In that airplane it worked fine and could be a good way to reduce workload in some situations. I wouldn't want to try it for the first time in a real engine out situation though, this is something I'd try in controlled conditions for the first time and something I'd do in any twin I intended to fly much as long as there isn't a limitation saying you can't.

Interesting. I was under the impression that the Baron was one of the more challenging airplanes due to the high power and relatively small vertical stabilizer. Sounds like it wasn't a problem for the autopilot to correct.

 

[MauleSkinner]

Interesting. I was under the impression that the Baron was one of the more challenging airplanes due to the high power and relatively small vertical stabilizer. Sounds like it wasn't a problem for the autopilot to correct.

The problem with the baron is that it’s loss of control mode below Vmc will stall the vertical stabilizer rather than just run out of authority. As long as you avoid that corner, it’s not an exceptionally challenging airplane.

 

[frfly172]

On my travelair it was a non event.

 

[Topper]

Had to shut down the left engine in a 421 at 160. 800 autopilot handled it well. Eventually had to descend to keep up airspeed.

 

[Brad Z]

Generally the autopilot will input roll to compensate for the yaw. Obviously that’s not a correct input, but it’s pretty obvious (at least in my opinion) what’s happening.

Correcting for an engine out require both roll and yaw. Most light GA autopilots don't control the yaw axis, and the pilot can input rudder and the autopilot can hold in the roll.