Flaperons behaviour at flaps 25/30

[rob345 3]

Hi,

 

I have a question concerning a "surprising" discovery:

With flaps 25 or 30 selected the flaperons retract to their neutral position at or above ~145kts.

I find this somehow weird because flaps 20 maneuvering speed is usually above 145kts. Thus, you have to reduce speed further to 145kts or below before selecting flaps 25.

 

Is this the correct behaviour of the flaperon? Maybe a kind of load relief?

 

I have searched the web, tutorial and FCOM but haven't found an answer so far...

 

 

Thanks for clarification

 

Robert

[rob345 3]

I have just noticed that even the official release video (on the PMDG website) shows this kind of flaperon behaviour.

 

During landing at KPHX you see that on short final the flaperons are retracted and drop down only seconds before touchdown (probably because speed reduces below the suspicious threshold of ~145kts)?!

[Roman 47]

Do you mean this behaviour? Btw. this is a 777-200ER

 

http://www.youtube.com/watch?feature=player_detailpage&v=tWKR4tEAeCA#t=490

[scandinavian13 5,192]

 

 

Is this the correct behaviour of the flaperon? Maybe a kind of load relief?

 

The flaperon - note the name, which is a portmanteau of flap and aileron - is there to both provide lift and roll the aircraft.  Part of landing is coming in with just enough lift so that you keep flying, but not so much that the plane wants to keep flying by the time you're supposed to touch down.

 

As part of the flaperon's purpose is to augment lift, do you see where I'm going here, and why it might be doing what you're seeing?

[DMullert 216]

Wow! This is indeed interesting folks. I fly very frequently on 777s. Mainly on American Airlines from DFW to SAO, DFW to LHR, and DFW to ARG. I have always observed the 777 wing behavior during all aspects of flight and I have to say.......I've never seen this flaperon behavior before. In every single occasion the 777 flaperon goes down with every notch down of the flaps and it flaps allright, but it does it all while being down at a pretty good angle. United (the airlines showcased in the video) flies 777s with PW engines and the ex-COA's fly with GEs. AA flies strictly RR, except the new 300s which feature GE engines. Would the engines maybe have something to do with this?

 

Strange! Dennis

[scandinavian13 5,192]

Would the engines maybe have something to do with this?

 

You noted that the flaperon normally deflects with the flaps when you've observed them, which is true.  Remember that there's also a trained pilot up front in these cases.  Now, based on my above post, do you see where this is going?  :wink:

[rob345 3]

Thanks for your answer Kyle. But I am not yet completely happy with it... ;-)

 

Generally, I know what a flaperon is and what it is designed for.

What was new to me is that its deflection on the T7 seems to depends not only on the current flap setting but also on other parameters (speed, thrust or whatever).

 

Part of landing is coming in with just enough lift so that you keep flying, but not so much that the plane wants to keep flying by the time you're supposed to touch down.

 

Actually, the landing in the release video (http://www.youtube.com/watch?v=qOm1oBD6eQ0) shows the contrary: Coming in with no flaperon (neutral) and just before touchdown instant deflection (full down).

 

So, I want to come back to my inital observation in the PMDG 777 that the flaperon retracts above ~145kts with flaps 25 or 30.

As a video says more than words, I made (a lousy) one to demonstrate what I mean:

 

http://www.youtube.com/watch?v=GaApo8ARgjo

 

As Vapp is around 143kts in this example, the flaperon would continuously retract/extract during final approach.

So, is this behaviour intendend?

 

Thanks again

 

Robert

[scandinavian13 5,192]

 

 

So, is this behaviour intendend?

 

Yes...if you look a little closer and read between the lines of what I wrote you'll start to see why I've said it.

 

Watch real videos of the plane and it behaves normally.  These pilots are trained to be on point.

Watch videos of simmers at the controls and in some cases it does not behave like you'd expect.  These pilots do not have the same training and control that the real pilots do.

 

Instead of continuing to be mysterious:

The plane is trying to salvage the pilot's poor technique.

 

Extra airspeed means extra lift.  Extra lift means the aircraft will not want to settle as easily.  Extra lift can be killed by reducing the level of the flaperon.

[Boeing or not going 578]

Thanks for your answer Kyle. But I am not yet completely happy with it... ;-)

 

Generally, I know what a flaperon is and what it is designed for.

What was new to me is that its deflection on the T7 seems to depends not only on the current flap setting but also on other parameters (speed, thrust or whatever).

 

 

Actually, the landing in the release video (http://www.youtube.com/watch?v=qOm1oBD6eQ0) shows the contrary: Coming in with no flaperon (neutral) and just before touchdown instant deflection (full down).

 

So, I want to come back to my inital observation in the PMDG 777 that the flaperon retracts above ~145kts with flaps 25 or 30.

As a video says more than words, I made (a lousy) one to demonstrate what I mean:

 

http://www.youtube.com/watch?v=GaApo8ARgjo

 

As Vapp is around 143kts in this example, the flaperon would continuously retract/extract during final approach.

So, is this behaviour intendend?

 

Thanks again

 

Robert

 

What sea textures are you using? they look great!

[rob345 3]

What sea textures are you using? they look great!

 

These are REX Essential textures with the theme "Wonderous" selected + shader 3 mod.

 

More pictures of these settings can be found on the homepage of my freeware FSX weather program FSXWX: http://www.plane-pics.de/fsxwx/

[ebksb123 4]

According to Boeing the pilot is supposed to add at least 5 knots to Vref on approach, depending on wind etc. So why does the flaperon go up at Vref+5?

[rob345 3]

These pilots are trained to be on point.

Watch videos of simmers at the controls and in some cases it does not behave like you'd expect.  These pilots do not have the same training and control that the real pilots do.

 

Instead of continuing to be mysterious:

The plane is trying to salvage the pilot's poor technique.

 

I don't see any "poor technique" or "not being on point" by being stable on approach at Vref+5? ... but the flaperons continuously go up and down nonetheless.

And btw: It also happens during autoland. So, does the autopilot control the airplane "poor", too...? ;-)

 

 

So why does the flaperon go up at Vref+5?

 

Thanks for understand my initial question correctly! That's exactly the point I don't understand.

[Haleo 3]

Have seen the same and wondered about it. When i select flaps 30, flaperons go back in its neutral position. Thats definitly not a pilot thing. It happens all the time. Never seen it on a real 777 before. The flaperons should stay in a flaplike down Position.

[blocks_off 5]

Just to add to this, if you look at the flaperon when the spoilers deploy on landing, the flaperon will go 'level'. Why? Adding to the above explanation; the flaperon goes level to reduce the lift and therefore add to the effectiveness of the spoiler deployment upon landing.

[BIGSKY 316]

Looks like he had an left aileron crosswind correction,observe the outboard aileron.