Uncommanded Flap Retraction after V1

[FlapsFive]

Ok, I don't know if there are any official procedures to deal with this, but given this hypothetical situation, what would you do?


V1, VR etc. calculated based on a certain flap configuration
After V1 there begins an uncommanded retraction of the flapsClearly you are above V1 so you can't abort the takeoff - I assume you would run up a bit more speed before rotation and begin with a shallower rate of climb whilst trying to rectify the problem?

Merely a hypothetical situation I was pondering a while back!

FF

[Rainboe]

Look, you're 17. Don't waste time on these silly hypothetical situations that are technically impossible. There are too many other things to worry about or need your attention! How many situations of uncommanded flap retraction on take-off occured in the world since the millenium? Zero. Don't concern yourself about it.

Forget hypothetical OK? be concerned with how to get Robber Brown out before he dumps us all in even deeper debt. He has made you £30,000 more indebted than you were a year ago. How can you keep your blood pressure down? Pull lots of wimmin? Those are things that should be occupying your (and our) minds, not silly situations that don't occur.

[FlapsFive]

I am sorry, I hadn't realised being a teenager made me ineligible to ask questions of a technical nature.

I simply happen to be quite interested in many of the technical aspects of aircraft - that is in fact one of the reasons I look forward to becoming a pilot (don't suggest that I become an aircraft engineer, I've looked into that already).

I thought that such a possibility might be unusual if not unheard of, but that doesn't mean to say that I should not be allowed to ask.

I would also be interested in knowing how you appear to have gained the knowledge of my age, seeing as my personal profile options show it as being "hidden".

FF

[Mad (Flt) Scientist]

I would also be interested in knowing how you appear to have gained the knowledge of my age, seeing as my personal profile options show it as being "hidden".

Rainboe doesn't, as some have suggested, have eldritch powers which enable him to know the age of posters.

If you declare your age (http://www.pprune.org/spectators-balcony-spotters-corner/356596-how-many-flying-hours-do-you-have.html#post4625011) in one post, people can always remember it. Or just search your posting history, as I just did. Which is why the only way to keep a secret on the internet is to keep it OFF of the internet!

[Mad (Flt) Scientist]

To address the OP, it is pretty much an impossible scenario, although I'd prefer the term "extremely improbable". It's probably more likely that you'd have some kind of inadvertent flap retraction (due to crew action) than have the system act on its own. But even that is pretty damned unlikely.

Many flaps don't move that quickly, so in fact even with retraction starting at V1 you might still have some portion of flaps left at Vr. In terms of what you would/should do: I'd suggest that the time required to identify the problem would be such that you'd be up and away long before you even considered "uncommanded flaps" as a scenario - which means you'd be climbing out at your "usual" AEO speed, and the only question is whether anything would happen before that point.

My own guess is that not much would happen; your rotation technique will be the same as any other takeoff, so the peak AoA will also be similar, so there's little chance of a stall (unless LE devices move uncommanded - that's a whole new scenario). You will get less lift at the alpha you get, so the takeoff will be more sluggish in terms of initial climb, but unless you're obstacle limited I doubt that should matter much.

You'd be better off doing the what-ifs for the cases which have happened, though - one of those would be far more likely to reoccur, and having thought THAT scenario through may well repay you at some point.

[FlapsFive]

Ah ha!! :ugh: Yeah I'd forgotten I'd posted there!

Thanks very much!

FF

[411A]

1979, AA DC-10, ORD.
Slats in this case, not flaps.
Uncommanded slat retraction on the left wing after number one engine detatched at/just after rotation.

Very bad results.:{

Best option?
Airspeed, and plenty of it, obtained by level acceleration, if need be.

PS:
Keep in mind that if the DC-10 in question had been an L1011, the left wing slats would absolutely have not retracted uncommanded...IE: it is not possible, as the TriStar uses jackscrews for slat operation.

A far superior design, just like the rest of the aeroplane.
Ahhh, Lockheed:E Simply built to a higher standard.

[lomapaseo]

This should be fairly simple to configure in MS Flight Sim and try out some options. I predict that it will fly just fine under your proposed scenario.

[Loose rivets]

How is getting just into the uncomfortable realm enunciated on modern kit?


Way back, one would see the ignighters come on - significantly before the shakers started. Just staying on the cusp of the shake would be my option if I was worried about terrain. This is where you have to consider gradient V climb rate.

Anyway, it's not going to happen...is it?

[Mad (Flt) Scientist]

How is getting just into the uncomfortable realm enunciated on modern kit?

Way back, one would see the ignighters come on - significantly before the shakers started. Just staying on the cusp of the shake would be my option if I was worried about terrain. This is where you have to consider gradient V climb rate.


Let's assume you've noticed the configuration problem. The risk of flying at shaker is that you don't necessarily know whether the same fault that has presumably led to the config change has also done 'something' to the inputs to the SPS - including the shaker settings as a result.

For example: flap position sensor(s) fail such that flap controller(s) think that the flaps are +10 degrees from where they actually are. If 10 was the real TO setting, then suddenly the system 'sees' the flaps at "20". So it'll command them back to a sensed 10 degrees - and so really at zero.

Now the flap controller will happily report "flaps 10" to all other systems, which will be configured as a result. But the flaps are actually, physically, at 0. So you'll have flaps 10 shaker, for example.

If flaps 10 shaker is higher than flaps 0 shaker, there may be a problem.

Of course, I don't know how many components had to fail in a very specific way to make that scenario happen .... quite a few I guess.

[galaxy flyer]

Just to add a note of reality. My brother, on the cat ready to launch off the USS Constellation on a dark Indian Ocean night, once got a warning light--WINGS IN TRANSIT! Holding his salute, the signal to fire the catapult, in the raised position, he had the RIO transmit-SUSPEND THE LAUNCH! Thus halting all deck activity, locking the cats. The Catapult Officer stood in front of the F-14 while the crew disconnected them from the cat. Sure enough, they went uncommanded to full sweep back.

So extremely unlikely, like most things aviation-not impossible.

GF

[Intruder]

This should be fairly simple to configure in MS Flight Sim and try out some options. I predict that it will fly just fine under your proposed scenario.
What is the fidelity of MSFS? Does it contain all the aerodynamic laws for all configurations? I would guess that it does not...

[Loose rivets]

Mmm...makes me feel that the quicker we get humans out of the equation the better. Back to the Iron Duck. AKA BAC 1-11, things were so simple. Firstly, the huge hydraulic flap motor was just a control 'follower'. The tiniest increment on the lever = a proportional flap movement.


Just an aside, but I showed my boss how one could slither the barn-door setting in and wash off the speed without putting the engines up to 'noise' setting. The thing was, that in those days, he just tried it while we were on a flight. He did it perfectly.

About duff information being sent to all corners of the aircraft. Again, when we were taught in the real airplane, flying with the shaker going was quite normal. (We trained to the push.) I flatter myself and indeed my colleagues, that in those days, if a false indication did occur, we would have just known by feel. A wonderful old training captain used to have us doing turns etc., all at the mush angle. You never forget that stuff.

[Mad (Flt) Scientist]

About duff information being sent to all corners of the aircraft. Again, when we were taught in the real airplane, flying with the shaker going was quite normal. (We trained to the push.) I flatter myself and indeed my colleagues, that in those days, if a false indication did occur, we would have just known by feel. A wonderful old training captain used to have us doing turns etc., all at the mush angle. You never forget that stuff.

Problem there is that for things like an aerodynamic configuration problem, depending on the airframe, there may well be no 'feel' to recognize. An aircraft which only has artificial stall warning, say, will give you no warning that you're approaching stall in the 'wrong' config. Though I'll confess you may notice something like the pitch attitude being 'wrong'.

[bubbers44]

That is what a normal pilot would do, just rotate to normal attitude and let it take off when it feels like it. Also flaps don't move on their own so put them where they belong. If you forget them like Madrid either way works.

[Reimers]

Also flaps don't move on their own so put them where they belong.

If this only was as simple as that!

An A320 had been dispatched with one ADIRS unit inoperative. During a subsequent take-off, the pilots noticed a sluggishness in getting airborne and the fact that the red part of the speed tape was encroaching on the V2 bug. After accelerating away from the low speed, they were shocked to realise that in fact, the flaps had retracted and only the slats remained where they were supposed to be!
Later it was found out that with one ADIRU inop, the flap load relief function has only one signal left to calculate when to retract the flaps, and after receiving a spurious "too high" airspeed, it commenced to retract the flaps!

Don't ever say never!

Also, this answers the supposedly young aviation enthusiasts question: When they realise what is happening, piloting the aircraft becomes paramount, and that is what the pilots did!

[NigelOnDraft]

Ok, I don't know if there are any official procedures to deal with this, but given this hypothetical situation, what would you do?

V1, VR etc. calculated based on a certain flap configuration
After V1 there begins an uncommanded retraction of the flaps Probably die :{

NoD

[Flight Detent]

For my money...

IF the F/O noticed the problem....immediately reach up over your head and select ALT FLAPS to ARM and then select DOWN..only takes a second...

That should both keep the LE devices extended, and stop any further retraction of the TE flaps...

Then when I get a second to spare...I could then select DOWN again to get enough TE flap to keep it flyin'.

But I seriously doubt that most FOs would notice...but then again, if we had a Flight Engineer aboard....he would be the man to do my bidding!

..with the 320, who knows where anything is at any particular moment...including the airplane itself!

that'll get 'um snarling....

Cheers...FD...:eek:

[IFixPlanes]

...
IF the F/O noticed the problem....immediately reach up over your head and select ALT FLAPS to ARM and then select DOWN..only takes a second...
...Hmmm... :confused:
In a Airbus you find the "ALT FLAPS" switch beside the "Wing lost" light. :ugh:
In a Boeing the flap load relief function did not retract the flaps below 25 (B737NG), 30 (737CL) or 20 (B744)
So what aircraft do you talking about?

[empacher48]

I'm currently doing an ATR type rating so just dealt with a flaps unlock after V1 in the sim today. (yes I know its not a full on retraction of the flaps) The procedure is to add 10kts to the Vr and V2 speeds.

Now if they unlocked and completely retracted I think you might end up rolling the thing up in a ball as you ran off the end of the runway. FWIW the flap zero Approach speed can be as high as 180 knots, with maximum tyre speed of 165 knots, so a simple add on of 10 knots to Vr and V2 probably won't give you flying speed..

Might ask the instructor tomorrow and try it in the sim.

[captjns]

While improbable, later Beoings have protection from uncommanded flap movements.

From the Boeing 737-700 (Vol. 2)

Trailing Edge Uncommanded Motion

Uncommanded motion is detected when no FLAP lever or flap load relief command is present and the TE flaps:

• move away from the commanded position
• continue to move after reaching a commanded position, or
• move in a direction opposite to that commanded.

The FSEU shuts down the TE drive unit by closing the TE flap bypass valve. TheTE flap shutdown cannot be reset by the flight crew and they must use the alternate flap system to control TE flaps. The shutdown is indicated by the flap position indicator disagreeing with the FLAP lever position. There is no flap needle split.