Engine shutdown/failure - no yaw?

[Delta 0]

I would like to practise asymmetric flight (engine failures). When I shut down an engine, there does not appear to be any yaw.  Can anyone suggest whether my settings generate an automated response, and if so how can I turn this off so I can respond manually?

 

Flight conditions:

- FSX autorudder un-checked (off)

- Cruising at 39,000ft

- Autothrottle set

- Autopilot (RNAV and VNAV) set

- Yaw dampener ON

 

Actions taken:

- Yaw dampener OFF

- Autothrottle disconnect

- Autopilot disconnect

- Engine start lever to cutoff on engine 1

 

Observations:

- Engine 1 thrust 2%, engine 2 thrust 102%

- Aircraft shows slight bank

- Rudder trim shows zero units

 

The aircraft doesn't appear to yaw at all. Are there other settings I need to change so that the aircraft yaws as expected?

 

Thanks lots,

 

Charlie Woods

[Alpha Floor 237]

Where are you looking at to determine if the aircraft is yawing or not?

 

You should look at the skid/slip indicator in the PFD, also known as the "sailboat". Also you should note that you're not really looking for yaw itself (that is, a rotation of the aircraft about its "z" axis), but you should be looking for SKID, what in flight mechanics is called a non-zero "beta" angle (the relative wind is not coming from straight ahead but from the side, basically a crab angle).

 

At first the aircraft will yaw to the side of the failed engine (in your example to the left) but will fly straight ahead, that is, no heading change. You will notice the "boat" on the the "sailboat" drifting to the right underneath the "sail", opposite to the side of the yaw, indicating SKID and asking for RIGHT rudder to correct it.

 

Like this:

 

Then, as a second effect if you don't do anything, the aircraft will start to roll to the left. Once the aircraft rolls over to the left, the "boat" might move back under the "sail" because this effect counteracts the SKID and might make it appear as if there is no yaw.

 

If you input right ailerons to prevent the aircraft from rolling, but NO rudder, you will fly in a straight line at a crab angle, and SKIDDING. You'll see the "boat" off to the right of the "sail".

 

EDIT: If anyone flying the 777 wants to try this out, you'll have to turn the PFCs off and revert to DIRECT law. Just turning the TAC off won't do it because the PFCs will still counteract the skid/slip by putting the rudder in.

[Delta 0]

Hi Jaime,

 

Thanks so much for your help.  I went through the same steps again today looking at the "sail boat" (good name for it) and it behaved as you suggested in your message.  Not sure what happened last time.

 

Thanks again,

 

Charlie

[Alpha Floor 237]

Hi Jaime,

 

Thanks so much for your help.  I went through the same steps again today looking at the "sail boat" (good name for it) and it behaved as you suggested in your message.  Not sure what happened last time.

 

Thanks again,

 

Charlie

 

Glad you resolved the issue!

 

By the way, it's not "officially" called "sailboat". I just like to call it that because it just so closely resembles the picture hanging from The Simpsons' living room

 

 

The correct name is, "sky pointer" for the triangle and "skid and slip indicator" for the rectangle.