Addition of Flaps in a Turn...

[EatSleepFly]

Someone told me today he read that if you extend flaps in a turn, an asymmetrical flap extenstion could result. I've never ever heard this before, and aerodynamically, it doesn't really make any sense (to me anyways). Sure, there's some difference in airflow over the outside wing (further distance to travel in same amount of time as inside wing) as opposed to the inside wing, but thats pretty slight. I highly doubt the flaps are far enough apart (on a light airplane anyways) to have much different amounts of airflow. Surely it can't be enough to cause assymetrical flap extension, can it? Anyone else ever heard this before? My best guess would be he was reading something about larger, faster aircraft. I suppose it would be a little more of a factor in those because of the increased distance between the flaps. Anyone?

[rausda27]

I extend flaps all the time in a turn, downwind to base and base to final...never had any problems and I cannot imagine any reason why asymmetrical extension might occur.

[EatSleepFly]

So do I. He hasn't even soloed yet, and couldn't remember where he read it. I was just curious if anyone else has ever been told that, or if he just has something confused.

[CapnJim]

Perhaps his CFI told him that to scare him in to not forgetting to put in flaps on base? Just a theory-- I've heard CFIs say all kinds of crap.

[MDPilot]

I think what was meant was that, in straight and level flight, asymmetric flap deployment is easily recognized since aileron input would be required to stay level. In a turn, recognition of asymmetric flaps may be delayed since you are probably using the ailerons to steepen or shallow the turn, and may not feel the asymmetric flaps until a much larger differential occurs (and if the asymmetry is rolling you into the turn, you may not be able to regain control in time.) This results in some instructors advice to never deploy flaps while turning.

[EatSleepFly]

I'm his CFI (and have been since he started)!!!!

Ah, thanks MDPilot, that makes sense.

[CapnJim]

WHOOOPS!!!!!
<removes foot and keyboard from mouth>

[sbav8r]

I was taught the same thing. The reason was as MDPilot said. If a assymetrical extension was to occur, for any reason not related to being in a turn, you would rather be straight and level rather than in a turn that could role you over. Besides, it makes for a nice square pattern and technique for new students. I throw in flaps in the turn all the time now, but back then it was probably for the best.

[say_speed]

I think the only reason is that if you extend flaps in a turn, AND there is an asymmetrical flaps extension (only the surface on the outside wing lowers), you could easily overbank the aircraft; and at low speed and low altitude, not a good thing...

[flying_ME]

[ QUOTE ]
... My best guess would be he was reading something about larger, faster aircraft. I suppose it would be a little more of a factor in those because of the increased distance between the flaps. Anyone?

[/ QUOTE ]

Well I can't add anything too technical here (still saving $ for private), but 3-4 wks ago I was in a sitting behind the wing in a 737 on approach to PHL in the clouds. What struck me was that during some of the turns, they would add flaps. I thought this would be kind of destabilizing, but there was no noticable change in bank or pitch (at least to my calibrated stomach).

My questions: if you add flaps in a turn is very noticable (requiring a lot of correction)? In commercial aircraft, when flying an approach thru the clouds with lots of turns, do you have to let the autopilot do the flying or is it pilot's choice? If you are hand-flying, would you want to add flaps mid-turn?

[say_speed]

My questions: if you add flaps in a turn is very noticable (requiring a lot of correction)? In commercial aircraft, when flying an approach thru the clouds with lots of turns, do you have to let the autopilot do the flying or is it pilot's choice? If you are hand-flying, would you want to add flaps mid-turn?

[/ QUOTE ]

When flying commercial airlines, it is up to the pilot to manually do the approach, or let the autopilot deal with it. In IMC, in a busy airspace, you might be better off watching what the A/P is doing... If you are handflying, the other pilot is very busy, distracting the cockpit crew from normal situational awareness. Handflying is allways a good pratice, in VMC, keep the IMC handflying for when you don't have a choice... The A/P is a much better pilot than I am, and when shooting an approach down to mins, the pax are much happier if I keep my hands off the yoke!
As far as adding flaps in a turn, off course you can do that, just know what the pitch reaction of your airplane will be when you lower the flaps; and if you keep a std rate of turn, or 30 degrees bank, you will not see any differences from a straight flight.

[E_Dawg]

You'll find out just what the plane does when you extend flaps, and you'll be anticipating it before ya know it . It's not the change of configuration that's the problem... it's the remote possibility of having one flap come down and the other stay up that could be a handful...

[stultus]

[ QUOTE ]
Someone told me today he read that if you extend flaps in a turn, an asymmetrical flap extenstion could result.

[/ QUOTE ]

My instructor has always taught me (well not really taught, more like conditioned with hand slapping) not to extend flaps in a turn.

In the Jeppesen "Manuevers Manual" that my instructor had me use, it specifically states in the section on landing (or patterns) that flaps should not be extended in a turn, not because that could cause asymmetrical extention, but because there might be something mechanically wrong and asymmetrical extention could occur and you don't want that to happen in a turn.

I went up with an instructor from Flight Safety and I noticed he did extend flaps while turning base. I asked him about it and he said that it's and old wive's tale that you shouldn't, there's no reason not to.

Since I've heard from two sources that it is potentially unsafe and there isn't really any benefit to extending them in a turn, I won't.

[EatSleepFly]

[ QUOTE ]
I asked him about it and he said that it's and old wive's tale that you shouldn't, there's no reason not to.


[/ QUOTE ]

Thats my theory on it. I just wanted to make sure I wasn't blowing off something that could potentially be unsafe.

[Josh]

I learned from the Jepp books too.

And the way they say it makes sense.

When you are already going slower, nearing stall speeds (especially while banking and slower speeds) why push it. One flap stays up, you are in a 20degree bank, at 70-80kts in a 172. There is a lot going on during landing, and missing that little additional roll created because one flap didn't extend, or just not all the way, is a good way to create a stall/spin nice and low where it'll be very hard to recover.

Commercially, larger planes, shallower turns, sure it may not change much if there is a slight problem. But coming in slow in a nice light little SE plane is just asking for it I think.

What is the reason for wanting to extend flaps in a turn? Why not before or after the turn? Remember, one flap down, and the other not, will act somewhat like ailerons. Not exactly, since the other side with not be up creating a loss of lift, but you get the idea.

That's my 3.452 cents.

Josh

[GregCollins2]

It is NOT an old wives tale. We had a C-172 with an asymetric flap extension here at TRI. It occured in straight and level flight and did not result in an accident. the cables from the flap motor to one of the flaps jammed in a pulley. Yes it's rare but it can happen. I don't believe Flight Safety teaches pilots that it's an old wives tale.

[Mr_Creepy]

Extending flaps in a turn has no more chance of causing an asymmetrical flap than in level flight. That's not the danger.

The danger is, suppose you happen to get an asymmetrical flap while in a turn, and it's the high wing?

You could get flipped over on your back in a hurry! The roll rate is slow enough to handle in level flight, but may not be if you are already in a roll rate aggravated situation, like a turn from base to final.

Most of my instructor captains insisted on no flap extensions in turns. They made a federal case about it most of the time, too!

[seagull]

In the airline world we don't worry about flaps in the turn or not, just as we don't worry about "turning into the dead engine" with an engine out on one side. Never heard of any carrier teaching not to add flaps in a turn, and that certainly did not come up as a factor when I was on the Commercial Aviation Safety (CAST) Team Loss of Control study group, or on the Joint Implementation Measurement Data Analysis Team (JIMDAT) sub working group, also connected with CAST. If adding flaps in a turn was a player in any accidents or incidents or events, I guarantee I would have heard of it during the 2 years I spent on these committees.

[Mr_Creepy]

I don't know what Airline world you are in.

Every carrier I flew with preached against adding flaps in turns.

They are in chronological order:

American Eagle
CCAir
Mesa
Air Midwest
Mesa Again
Midway

[DanTheMan]

[ QUOTE ]
I don't know what Airline world you are in.

[/ QUOTE ]

Fed-ex?

[seagull]

Perhaps you should take a look at my profile before asking such questions? Not listed there, I was also an LCA and IP at a large regional (UA Express carrier), so I have that experience as well. If you are not familiar, CAST was what became of the White House Commission on Aviation Safety and Security. The members of that committee consist of ALPA, ATA, FAA, the manufacturers, NASA, ICAO, DOD, DOT and several other alphabet organizations. Each one offering people who are considered (in the words of CAST, and I personally hate the term), "experts" in the field. I was drafted to be group chairman for the Loss of Control JSIT Training committee (a job I spent the rest of the year trying to get myself out of!).

After that, at the JIMDAT we were tasked with looking at all accident types and, with statistical and empirical analysis, deciding which projects met the criteria for going forward. If we had somehow missed the issue when we did the JSAT/JSIT, we would have caught it in JIMDAT.

Suffice to say, with the FAA Transport Directorate, the manufactures and airlines all sending their flight test engineers, aero dynamicists, chief test pilots and a host of others, if there had been an issue of adding flaps in turns, we WOULD have addressed it.

Quite simply, it is not an issue affecting transport aviation.

[Mr_Creepy]

I disagree. For reasons stated above there is an increased chance of danger if an asymmetrical flap situation occured in a turn.

While the initials are impressive, I'm just talking about "fisics"

Also, every one of those airlines had a policy of no flaps in turns, especially in the turboprop aircraft.

And no, I don't read profiles! Who has time? I can barely read all the posts on here.

[ananoman]

I work at FSI and I teach the addition of flaps in turns. I really don't see any reason why a pilot should avoid doing this. If you are that worried about something bad happening, quit flying.

All of our aircraft here have mechanical flaps that you have to extend by pulling a lever between the seats. I usually go flaps 10 on downwind and add flaps 25 on the downwind to base turn and then go to flaps 40 on the base to final turn. If you have electric flaps and are turning it might be wise to avoid going from no flaps to full flaps in a turn, but I see no reason why you would do this anyway. Flaps are usually added in increments, so any rolling moment should be easily countered if an asymmetrical deployment occurs.

I have not run across any accidents dealing with the addition of flaps in turns. The only accidents I have read about all dealt with the removal of flaps and slats in turns. There have been several accidents where aircraft retracted flaps and slats too early after takeoff. If you are too low and slow this can be fatal, especially in a turn (higher load factor). Most of these occurred during the early transition to jets, when pilots were not familiar with the tricky handling characteristics of swept wings.

[seagull]

Well, the operators often know less of their aircraft than do the manufacturers, so I would lean with the flight test and certification community, overall.

Having said that, there is merit to saying that a low time pilot might have problems sensing an assymetric condition due to lack of familiarity with the handling qualities of the aircraft. Perhaps the regionals you flew for had that problem due to hiring so many low time/inexperienced pilots?

[Mr_Creepy]

LOL what regional commuter was NOT hiring low time pilots between 1996 and 2000?

I started at Eagle in Jan 1995 with 2300 hrs and I was about the norm.

When I started at Mesa in July 1996 with 3500 hrs I was something of a freak. The next highest time person in my class had around 2200. We had quite a few who barely had 1500 with wet ink on their ATPs. (Mesa required ATPs back then, except for San Juan grads.)

Right after that some San Juan classes started with a bunch of 300 hr pilots.

But still, your remark is very provincial. I don't think there is a real difference in flying skills beyond a certain number of hours. After 1500 hrs or so (changes from person to person of course) the skills developed are more judgement than actual stick and rudder.

For example, my judgement says don't extend flaps in turns. If it's questionable why do it? Any one who does extend flaps in turns after being warned against it is demonstrating either poor judgement, or a severe testosterone problem.

If you are an experienced pilot who knows how to plan a stabilized approach, than except under unusual circumstances there should be no need to extend flaps in a turn.

So in summary, if there is any question, why do it? To show off? Remember that many early air disasters were prefaced with "Watch this!"