Flap retraction/extension during turn
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Flap retraction/extension during turn
Hello everybody,
I spoke with a lot of coleagues about this issue and oppinions are contradictional. However the precentage of pilots who are against this to be done are eldery guys by my experience so it might be connected to the aerodinamic and operational theories and rules of old days. That is my best guess.
Let ussee your oppinions about this.
Regards
Velez2
I spoke with a lot of coleagues about this issue and oppinions are contradictional. However the precentage of pilots who are against this to be done are eldery guys by my experience so it might be connected to the aerodinamic and operational theories and rules of old days. That is my best guess.
Let ussee your oppinions about this.
Regards
Velez2
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Depends on whether you have flap asymmetry protection or not IMHO. If you do, like most proper (ie big) airplanes, then no biggie. If you don't, and it is convenient to do it when wings level, sure. I wouldn't make a big fuzz about it though. Unless the POH says you can't do it, then I'd say it's a matter of personal choice!
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Well that is my approximately my oppinion also. However recently I read about a accident (military though) with F84G which has been known to have a protection against simetry (torque shaft or other mechanical interconection between flaps) but newertheless it had had asimetry in extension and crashed. Link failed apperantly.
That kinda changed my oppinion in the direction of do not do it.
Thanks for reply
That kinda changed my oppinion in the direction of do not do it.
Thanks for reply
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In ag aircraft, applying flaps while turning and taking them back out as one rolls out of the turn is a common practice. With steep turns at 100' every 30 seconds, all day long, it's little more than added stall margin.
Oh stop it now, C'mon !!!! do you know SNS3Guppy's experiences
did you check your OpsSpecs for that A320 dimensions, and performance specifications, which is very completely different, of course, from that A321 that you're on....
did you check your OpsSpecs for that A320 dimensions, and performance specifications, which is very completely different, of course, from that A321 that you're on....
do you have the OpsSpecs for the A320,...if so do they answer A320 performance question...? or at least have you looked at the TERPS Criteria for the A320...don't you know that all operational information is for a type is listed in the TERPS under Far 25
and just too add SNS3Guppy is, amongst other things, an expert Ag pilot...so perhaps you could learn a little here from folks like him, no?
and just too add SNS3Guppy is, amongst other things, an expert Ag pilot...so perhaps you could learn a little here from folks like him, no?
?
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Bad practice to raise flaps in the turn. Reason is, you have very high lift devices deployed. raising them in the turn is a no no on a heavy or high performance jet. If you do raise them you are reducing this extra lift when you need it most. The loss of lift can be very sudden and could happen at the wrong time, if you hit a bumpy patch for example. The stall speed is being increased, (therefore the safety margin decreased), at the very time you dont want it the Vs increased.
I also have done my time in ag flying may years ago. As far as assisting the turn was concerned never used flaps as a rule. I always flew clean and fast but had the flaps as a backup if I thought I needed them, although not very often in my 10 years at it. That technique gave me the extra margin of speed. Speed is my friend.
The one exception was the DHC2 Beaver, on ag work.. It needed the flaps applied in a turn, every turn! IMHO
Just my 2 cents worth.
I also have done my time in ag flying may years ago. As far as assisting the turn was concerned never used flaps as a rule. I always flew clean and fast but had the flaps as a backup if I thought I needed them, although not very often in my 10 years at it. That technique gave me the extra margin of speed. Speed is my friend.
The one exception was the DHC2 Beaver, on ag work.. It needed the flaps applied in a turn, every turn! IMHO
Just my 2 cents worth.
Last edited by weido_salt; 21st Jun 2010 at 22:08.
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Bad practice to raise flaps in the turn. Reason is, you have very high lift devices deployed. raising them in the turn is a no no on a heavy or high performance jet.
I've been raising and lowering flaps in turns for 12 years in heavy 747s (all varieties), and haven't had one stall or fall out of the sky yet. Performance margins are more than adequate in all normal flight conditions -- maybe that's why the 747 FCOM and Flight Handbook say it's allowed...
I agree with 'Intruder', providing you have the speed and are accelerating what's the problem? Modern glass cockpits even show min speed per flap setting. I have been taking flaps up (and down) during turns all my life and cannot see any justification for concern. Just fly the aeroplane, or airplane as you lot call it.
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The issue of flap operation during a turn specifically relates to flap retraction which usually means an immediate turn after take-off is the worst case of a climb, low speed and low level.
The problem is that flap retraction starts well below the speed for full manoeuvre protection. For example a 737 taking off with Flap 5, entering a turn at 400' would normally start to move to flap 1 at V2+15 (say 170kts) and accelerating, which means that full manoeuvre isn't available until another 20-30kts. With extension the minimum clean speed would 210kts.
Hence, the 737 FCTM recommends for an immediate turn after takeoff, to select just climb thrust and not to accelerate and retract until the turn is completed.
The problem is that flap retraction starts well below the speed for full manoeuvre protection. For example a 737 taking off with Flap 5, entering a turn at 400' would normally start to move to flap 1 at V2+15 (say 170kts) and accelerating, which means that full manoeuvre isn't available until another 20-30kts. With extension the minimum clean speed would 210kts.
Hence, the 737 FCTM recommends for an immediate turn after takeoff, to select just climb thrust and not to accelerate and retract until the turn is completed.
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How flaps are used, or how an airplane is configured, really depends on which aircraft, what operation, and what maneuvering is being done, as well as how much flap is to be used.
In the B747, we have minimum flap retraction speeds on takeoff, for example, and limit ourselves to a 15 degree bank angle until 10 knots over those speeds. If given a turn during the clean-up portion of a departure, I will accelerate to 10 knots over the bug speed for a given flap setting, before bringing up the flaps, in order to use the full bank angle in the turn. With flaps retracted, I'm limited to a 15 degree bank until I accelerate a little more, and then I can use the full bank.
We don't do a lot of wild maneuvering in the 747, obviously. In the case of the ag airplane previously mentioned, indeed many modern ag aircraft, flap use is a regular thing. Many ag operators will use flap in a turn and take it back out as one rolls out of the turn, especially when "heavy." The flap switch on a number of ag airplanes is on the throttle, so the flaps can be thumbed in or out while maneuvering. The flaps increase stall margin and reduce turn radius by allowing one to pull a little more through the turn. Larger turn radius and higher speeds equate to more time spent turning and less doing work, and one usually tries to minimize time spent in the turns, and maximize time spent applying chemical in the field.
Likewise, I've done a lot of low level work in the mountains doing firefighting, and flap application is very important, there. One large four-engine airplane I flew doing fire work required 1/2 flaps on the drop, and this made a 50 knot difference in the stall speed...very important in mountain gusty conditions.
Retracting flaps in a turn is not unsafe, but should be done sensibly. The notion that one should never retract flaps in a turn is nonsensical; a turn has no bearing on flap retraction. The speed and energy one has at the time, and one's relationship to angle of attack and minimum speeds, of course, is very relevant. If one is too slow to retract flaps in the turn, then one is too slow; either speed up or wait. If one has adequate energy, margin, and speed, then by all means, put them up or down in the turn.
Flap assymetry is flap assymetry, whether in the turn or not.
The airplane doesn't know if it's in a turn. The airplane doesn't know it's altitude. The airplane knows nothing...flaps retracted in a turn, flaps retracted at 5' of altitude...the airplane doesn't know or care where or when. The airplane can't think...and is perfectly happy two seconds from impact if you fly it into the side of a cliff. The determining factor, then, is you. Raising the flaps is perfectly safe in a turn, if you do it properly. Raising the flaps at 5' above the ground is perfectly safe, if done properly.
Policies exist in various aircraft, either given by the manufacturer or by the operator, regarding aircraft configuration, flap retraction, etc, and these generally dictate how the airplane will be operated. This doesn't mean that raising the flaps in a turn is unsafe; it does mean that an operator who improperly raises them in a turn, perhaps while too slow or at too steep a bank angle for a given angle of attack and airspeed, may be doing something unsafe.
Now...there's a difference in the way a B747 is configured with flaps, and an Air Tractor AT-802 is configured with flaps, as well as a difference in the airfoils, flap retraction times and methods, complexities, flap type, etc. With the initial applications of flap in the 747, for example, not only are the trailing edge flaps configured, and not only do they extend aft and down to increase the wing area, but two types of leading edge devices are deployed to increase wing camber and change the angle of attack. The 747 is a swept wing airplane with a very large wing and a very heavy weight capability. It's mission is different, and it's maneuvering tends to be a lot more benign than say, a Thrush S2R or Dromader M18T. Never the less, the same basic principles apply.
If one is too slow, then raising flaps may be a bad idea. Sometimes raising flaps can be used to good effect. On many occasions over the years in light airplanes, I've raised flaps as I touch down, or just before touchdown, in a light airplane on a rough surface. It's always a standard practice in ag airplanes, for me, too. Retracting flaps helps positively set the airplane down and keep it down. Standard for me in the 802 or Dromader, for example, is to put the airplane on the mains, pin the mains with some forward stick, then retract the flaps while holding the tail off, lower the tail to the surface, and pull reverse. Others whom I know tend to go right to reverse with the tail in the air. I don't do that. But retracting flaps ensures that an airplane which was just barely flying with full flaps, is no longer going anywhere, and it sticks to the ground...no more lift. It also allows the tail to come down more quickly, which allows braking and or reverse to be more effective, and safer. Retraction of flaps is a useful short-field technique on soft and rough fields...and in the real world of short-field work, short fields are often rough fields...where props toss rocks into flaps, and where power plants and props can suck up rocks, sand, and gravel, and be damaged.
Likewise, in a light airplane such as the 802 (light being a relative term; at 16,000 lbs, it's a heavy single-engine light airplane, but it's also performance-limited at that weight, which means it's also got a reduced maneuvering margin), I commonly retract flaps just after takeoff...often while still in ground effect, though sometimes I'll carry flaps during the climb-out, too (a little flap seems to help). Very often in the M18 Dromader, I'll have takeoff flaps retracted by the time I reach the end of the runway, and will initiate my turn on course from ground effect, at a low level, while doing the flap retraction. Again, it's a matter of being sensible. One knows, even as a student pilot in a Cessna 150, that simply retracting flaps and doing nothing might lead to a descent back to the ground, a stall, a wider turn, etc...all depending on what one's doing at the time. This is no different in a Cessna 150 than it is in a Boeing 747...despite the obvious disparity in complexity and operation. Operate sensibly, and you can most certainly apply and retract flaps in a turn.
Something that hasn't been addressed is maneuvering while applying flaps. Loading the structure and the airplane can have an effect on the wing and flaps, and any time flaps are applied, a load is applied to all the attach points as well as the wing itself. Rolling into a turn or out of a turn with aileron applied and other turn devices (ala 747) can place a different load on the wing and it's associated components than if one applies the flaps in level flight. This is largely inconsequential, however, if one operates the airplane inside the known and published flight envelope, respecting the speeds, weights, bank angles, etc, that apply to a given airplane.
In the B747, we have minimum flap retraction speeds on takeoff, for example, and limit ourselves to a 15 degree bank angle until 10 knots over those speeds. If given a turn during the clean-up portion of a departure, I will accelerate to 10 knots over the bug speed for a given flap setting, before bringing up the flaps, in order to use the full bank angle in the turn. With flaps retracted, I'm limited to a 15 degree bank until I accelerate a little more, and then I can use the full bank.
We don't do a lot of wild maneuvering in the 747, obviously. In the case of the ag airplane previously mentioned, indeed many modern ag aircraft, flap use is a regular thing. Many ag operators will use flap in a turn and take it back out as one rolls out of the turn, especially when "heavy." The flap switch on a number of ag airplanes is on the throttle, so the flaps can be thumbed in or out while maneuvering. The flaps increase stall margin and reduce turn radius by allowing one to pull a little more through the turn. Larger turn radius and higher speeds equate to more time spent turning and less doing work, and one usually tries to minimize time spent in the turns, and maximize time spent applying chemical in the field.
Likewise, I've done a lot of low level work in the mountains doing firefighting, and flap application is very important, there. One large four-engine airplane I flew doing fire work required 1/2 flaps on the drop, and this made a 50 knot difference in the stall speed...very important in mountain gusty conditions.
Retracting flaps in a turn is not unsafe, but should be done sensibly. The notion that one should never retract flaps in a turn is nonsensical; a turn has no bearing on flap retraction. The speed and energy one has at the time, and one's relationship to angle of attack and minimum speeds, of course, is very relevant. If one is too slow to retract flaps in the turn, then one is too slow; either speed up or wait. If one has adequate energy, margin, and speed, then by all means, put them up or down in the turn.
Flap assymetry is flap assymetry, whether in the turn or not.
The airplane doesn't know if it's in a turn. The airplane doesn't know it's altitude. The airplane knows nothing...flaps retracted in a turn, flaps retracted at 5' of altitude...the airplane doesn't know or care where or when. The airplane can't think...and is perfectly happy two seconds from impact if you fly it into the side of a cliff. The determining factor, then, is you. Raising the flaps is perfectly safe in a turn, if you do it properly. Raising the flaps at 5' above the ground is perfectly safe, if done properly.
Policies exist in various aircraft, either given by the manufacturer or by the operator, regarding aircraft configuration, flap retraction, etc, and these generally dictate how the airplane will be operated. This doesn't mean that raising the flaps in a turn is unsafe; it does mean that an operator who improperly raises them in a turn, perhaps while too slow or at too steep a bank angle for a given angle of attack and airspeed, may be doing something unsafe.
Now...there's a difference in the way a B747 is configured with flaps, and an Air Tractor AT-802 is configured with flaps, as well as a difference in the airfoils, flap retraction times and methods, complexities, flap type, etc. With the initial applications of flap in the 747, for example, not only are the trailing edge flaps configured, and not only do they extend aft and down to increase the wing area, but two types of leading edge devices are deployed to increase wing camber and change the angle of attack. The 747 is a swept wing airplane with a very large wing and a very heavy weight capability. It's mission is different, and it's maneuvering tends to be a lot more benign than say, a Thrush S2R or Dromader M18T. Never the less, the same basic principles apply.
If one is too slow, then raising flaps may be a bad idea. Sometimes raising flaps can be used to good effect. On many occasions over the years in light airplanes, I've raised flaps as I touch down, or just before touchdown, in a light airplane on a rough surface. It's always a standard practice in ag airplanes, for me, too. Retracting flaps helps positively set the airplane down and keep it down. Standard for me in the 802 or Dromader, for example, is to put the airplane on the mains, pin the mains with some forward stick, then retract the flaps while holding the tail off, lower the tail to the surface, and pull reverse. Others whom I know tend to go right to reverse with the tail in the air. I don't do that. But retracting flaps ensures that an airplane which was just barely flying with full flaps, is no longer going anywhere, and it sticks to the ground...no more lift. It also allows the tail to come down more quickly, which allows braking and or reverse to be more effective, and safer. Retraction of flaps is a useful short-field technique on soft and rough fields...and in the real world of short-field work, short fields are often rough fields...where props toss rocks into flaps, and where power plants and props can suck up rocks, sand, and gravel, and be damaged.
Likewise, in a light airplane such as the 802 (light being a relative term; at 16,000 lbs, it's a heavy single-engine light airplane, but it's also performance-limited at that weight, which means it's also got a reduced maneuvering margin), I commonly retract flaps just after takeoff...often while still in ground effect, though sometimes I'll carry flaps during the climb-out, too (a little flap seems to help). Very often in the M18 Dromader, I'll have takeoff flaps retracted by the time I reach the end of the runway, and will initiate my turn on course from ground effect, at a low level, while doing the flap retraction. Again, it's a matter of being sensible. One knows, even as a student pilot in a Cessna 150, that simply retracting flaps and doing nothing might lead to a descent back to the ground, a stall, a wider turn, etc...all depending on what one's doing at the time. This is no different in a Cessna 150 than it is in a Boeing 747...despite the obvious disparity in complexity and operation. Operate sensibly, and you can most certainly apply and retract flaps in a turn.
Something that hasn't been addressed is maneuvering while applying flaps. Loading the structure and the airplane can have an effect on the wing and flaps, and any time flaps are applied, a load is applied to all the attach points as well as the wing itself. Rolling into a turn or out of a turn with aileron applied and other turn devices (ala 747) can place a different load on the wing and it's associated components than if one applies the flaps in level flight. This is largely inconsequential, however, if one operates the airplane inside the known and published flight envelope, respecting the speeds, weights, bank angles, etc, that apply to a given airplane.
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SNS3Guppy
A good and informative post indeed.
As far as ag aircraft go, the guys that did apply flap in turns, had flap motors burning out at a a high rate, on S2R operations, IIRC. That was the last thing I needed on a remote operation, downtime for a burnt out flap motor. I flew the S2R, both Iron and turbine but never felt the need to use flap in a turn however. Can't comment on the Air tractor as I never operated it. There weren't a lot of them around when I last strapped an ag aircraft to my backside.
Maybe I should have amended my original post on this thread, to "high performance, high wing loaded aircraft". That would have not made it necessary for us to bring in the B747 so eagerly. I too flew the B747 classic and it was the easiest and most "forgiving" of the heavy aircraft I have operated.
In answer to the original post on this thread I say this. Think long and hard before raising flaps/high lift devises whilest in the turn. Dont let raising flaps in a turn become a reflex action. I still won't raise the flaps in a turn when I am PIC, or let it be done.
A good and informative post indeed.
As far as ag aircraft go, the guys that did apply flap in turns, had flap motors burning out at a a high rate, on S2R operations, IIRC. That was the last thing I needed on a remote operation, downtime for a burnt out flap motor. I flew the S2R, both Iron and turbine but never felt the need to use flap in a turn however. Can't comment on the Air tractor as I never operated it. There weren't a lot of them around when I last strapped an ag aircraft to my backside.
Maybe I should have amended my original post on this thread, to "high performance, high wing loaded aircraft". That would have not made it necessary for us to bring in the B747 so eagerly. I too flew the B747 classic and it was the easiest and most "forgiving" of the heavy aircraft I have operated.
In answer to the original post on this thread I say this. Think long and hard before raising flaps/high lift devises whilest in the turn. Dont let raising flaps in a turn become a reflex action. I still won't raise the flaps in a turn when I am PIC, or let it be done.
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The issue of flap operation during a turn specifically relates to flap retraction which usually means an immediate turn after take-off is the worst case of a climb, low speed and low level.
Further, flap retraction after takeoff is done on a briefed schedule DURING ACCELERATION. If the pilot adheres to the flap retraction schedule, adequate stall and gust margin is available to 40+ deg of bank, even though the normal turn is at 25 deg bank and max allowed is 30 deg. There is nothing unsafe about retracting flaps in a turn, as long as the design parameters are met.
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I rarely post on here but 'Bumpy' your constant trolling of these forums is getting too much. Either your a Flight simmer or a child that has aspirations to be a airline pilot. Either way please stop posting rubbish on every thread! 