I was wondering about this for a while...

 

Can you extend or retract flaps when you are in a turn? And can you lower or raise the landing gear at that time? Maybe the aircraft becomes unstable when doing this?

 

Cheers

Absolutely. Are you having a problem?

Generally speaking you can, but you need to watch out for flap asymmetry. If one side extends more than the other, and it's the high wing in the turn, depending on rudder authority et al you could run into a situation where the aircraft will keep rolling to an uncontrollable state. Less of a problem on something this size than the single engine trainers people learn in where I was always taught to try and be straight and level before flaps or gear.

No, not at all. Just my general interest.

 

 

Can you extend or retract flaps when you are in a turn?

 

Can?  Yes.

I've had a couple flight instructors say the practice is frowned upon, though.

 

The way it was explained to me is that, if you're entering a turn, you're expecting the aircraft to roll.  If you lower the flaps and one side gets jammed, that asymmetric flap condition may go unnoticed a lot longer than it would've if you'd extended flaps when wings level.

 

I'd say that risk is rather slim, so I'd say avoid if possible, but don't delay the addition of flaps if necessary while in a turn.

 

 

 

And can you lower or raise the landing gear at that time?

 

Sure.

 

 

 

Maybe the aircraft becomes unstable when doing this?

 

Why would it?

(Just trying to get you to think, here)

Thanks Kyle, that is clear. You discribed the 'unstable' part (cannot think of a better english word) in your first anwser. Air is flowing differently when extending the flaps. If you are in a turn, those changing flows might be problematic. But I'm not sure... sorry, I studied geography, not physics.

 

 

You discribed the 'unstable' part (cannot think of a better english word) in your first anwser. Air is flowing differently when extending the flaps. If you are in a turn, those changing flows might be problematic.

 

This would only occur to a significant amount if there were a mechanical problem with the aircraft though (flap jam, or similar).  In a turn or in wings level flight this would be equally problematic.  The only issue that I was alluding to earlier was that, in a turn, this asymmetric lift would not be as obvious (at least initially).

This would only occur to a significant amount if there were a mechanical problem with the aircraft though (flap jam, or similar).  In a turn or in wings level flight this would be equally problematic.  The only issue that I was alluding to earlier was that, in a turn, this asymmetric lift would not be as obvious (at least initially).

 

Depending on the size of the aircraft and your rudder authority and bank-angle in the turn. If you're doing 30-40deg of bank and get a lower-wing jammed flap and the high flap keeps going it's gonna get real interesting real quick. Again, generally not something you end up doing in a jetliner (short base to final turns in light twins/singles) but still not unheard of causing accidents.

For what it's worth, RW CRJ pilots try to activate the flaps during turns to minimize passenger discomfort from the pitch change necessary to maintain altitude when the flaps are activated. I haven't dived into the 777 systems deeply yet (and don't have hem handy at the moment), but modern systems tend to have monitoring and lockout if asymmetry develops that would stop the movement of the flaps.

P-38 pilots had 8-deg of fowler flap available to tighten up their turns and get inside the ME-109.