Reducing flaps on short finals
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Reducing flaps on short finals
Hi,
About 9 months ago I was a passenger in a C172 - we were a little high on approach so the pilot, on 20 degrees flap, selected full flaps (30 degrees) on short finals. At about 400 - 500 ft coming in to land the picture of the approach appeared that we would need some more power to take us to the threshold. Instead of adding power the pilot reduced flaps to 20 degrees which flattened the approach and we landed on the keys with no extra input of power.
It was the first time I had seen this technique and wondered if this was acceptable (ie safe) and wondered what might the pitfalls be if this practice is not safe.
Thanks in advance,
Mixturerichlean.
About 9 months ago I was a passenger in a C172 - we were a little high on approach so the pilot, on 20 degrees flap, selected full flaps (30 degrees) on short finals. At about 400 - 500 ft coming in to land the picture of the approach appeared that we would need some more power to take us to the threshold. Instead of adding power the pilot reduced flaps to 20 degrees which flattened the approach and we landed on the keys with no extra input of power.
It was the first time I had seen this technique and wondered if this was acceptable (ie safe) and wondered what might the pitfalls be if this practice is not safe.
Thanks in advance,
Mixturerichlean.
Last edited by mixturerichlean; 25th Apr 2015 at 23:35.
It's a very unusual way to use the flaps.
Did he maintain a constant power setting during the approach, or was the throttle at idle?
Is he also a glider pilot? He seems to be using the flaps as a glider pilot would use airbrakes.
Perhaps he selected flaps 30, and then changed his mind for some reason unconnected with height, (Perhaps because the crosswind was stronger than he thought) and just appeared to be controlling the height with flap?
You could always ask him!
In any case, I see no danger in adjusting the flaps from 30 to 20 at 400'-500'.
MJ
Did he maintain a constant power setting during the approach, or was the throttle at idle?
Is he also a glider pilot? He seems to be using the flaps as a glider pilot would use airbrakes.
Perhaps he selected flaps 30, and then changed his mind for some reason unconnected with height, (Perhaps because the crosswind was stronger than he thought) and just appeared to be controlling the height with flap?
You could always ask him!
In any case, I see no danger in adjusting the flaps from 30 to 20 at 400'-500'.
MJ
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mixturerichlean
I prefer not to do this though I have seen it done. One time a copilot in a turboprop plane did this and I watched with interest. I asked him why he did that?
He said, so he didn't have to touch the throttles.
And I asked him what was so hard about moving the throttles?
He said it was "COOL".
I said it was dumb and not to do it on my plane again.
I think the pilot who did this probably wasn't much of a pilot. But he was COOL. So, do you want to be COOL or a good pilot?
IF you want to be COOL, do what he did.
IF you want to be a good pilot, well, need I say more? wink wink, nod nod.
I prefer not to do this though I have seen it done. One time a copilot in a turboprop plane did this and I watched with interest. I asked him why he did that?
He said, so he didn't have to touch the throttles.
And I asked him what was so hard about moving the throttles?
He said it was "COOL".
I said it was dumb and not to do it on my plane again.
I think the pilot who did this probably wasn't much of a pilot. But he was COOL. So, do you want to be COOL or a good pilot?
IF you want to be COOL, do what he did.
IF you want to be a good pilot, well, need I say more? wink wink, nod nod.
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I prefer the old "power for altitude, pitch for speed" method, pulling in the flaps on short final just does not seem right to me. If it was a low time pilot I would say that if you felt the need to bring the flaps in then you're not on a stabilized approach so just power it in and bring her round again and try a little harder to get it right second time around.
The one thing to be said in favour of this method is that one is better prepared for a loss of engine power.
Myself was taught to land my microlight with no power at all, and slightly too high on final, then sideslip to land on the numbers (if any!) or even before.
Should I find myself too low and/or too slow on short final (iow, short on energy, as rightly pointed out above), reducing flaps would be my natural reaction. None the less one hand will always be on the throttle, during landing.
Myself was taught to land my microlight with no power at all, and slightly too high on final, then sideslip to land on the numbers (if any!) or even before.
Should I find myself too low and/or too slow on short final (iow, short on energy, as rightly pointed out above), reducing flaps would be my natural reaction. None the less one hand will always be on the throttle, during landing.
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It is hard to say something real helpful without knowing a bit more about the pilot and the aircraft. If seen from training perspective and aiming for low-timers it is an absolutely NoGo - if you do so in training session or checkride your best bet is to fail.
Now the but, you can do this on a very friendly aircraft like some 172s, especially the older ones with 40 flaps - IF AND ONLY IF you know exactly your plane. DO NOT, repeat DO NOT do this on unfamiliar or tricky planes. If you are a little low or trimmed on slightly off wrong attitude, you may fall from the skies.
Yes, I have seen this - most of the times from experienced glider pilots and on power idle, but they definitely have a different education and it remains dangerous on certain conditions. Yes, I have done it, but only when absolutely sure of the situation, but never below 600ft.
So, I would conclude - it is a procedure for experienced pilots only in very certain aircraft only and in certain conditions only, and not to be tried by low-timers.
My personal feeling, never to be done when pax aboard. If you kill yourself, fine it's yours, but do not, never ever, expose passengers to unnecessary threat!
Now the but, you can do this on a very friendly aircraft like some 172s, especially the older ones with 40 flaps - IF AND ONLY IF you know exactly your plane. DO NOT, repeat DO NOT do this on unfamiliar or tricky planes. If you are a little low or trimmed on slightly off wrong attitude, you may fall from the skies.
Yes, I have seen this - most of the times from experienced glider pilots and on power idle, but they definitely have a different education and it remains dangerous on certain conditions. Yes, I have done it, but only when absolutely sure of the situation, but never below 600ft.
So, I would conclude - it is a procedure for experienced pilots only in very certain aircraft only and in certain conditions only, and not to be tried by low-timers.
My personal feeling, never to be done when pax aboard. If you kill yourself, fine it's yours, but do not, never ever, expose passengers to unnecessary threat!
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Larger aircraft have speed brakes which we usually pop if given a speed reduction by ATC or other situations where speed needs to be reduced or contained or a steep rate of descent is required.
they are noisy for PAX so instinct is to only use them if needs must.
some small aircraft have speed brakes some as a conversion some as standard. I think one of the moonies is fitted with speed brakes.
Most of the lift on flaps comes in the lower extension levels fully extended they are mostly drag so I can see the temptation to use that drag portion as speed brakes but its not really good practice
Pace
they are noisy for PAX so instinct is to only use them if needs must.
some small aircraft have speed brakes some as a conversion some as standard. I think one of the moonies is fitted with speed brakes.
Most of the lift on flaps comes in the lower extension levels fully extended they are mostly drag so I can see the temptation to use that drag portion as speed brakes but its not really good practice
Pace
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Raising the flaps on short final worked for the captain of the BA 777 whose engines flamed out due to fuel line blockage with ice at Heathrow a few years ago.
He didn't have the luxury option of adding more power and the manoeuvre got him over the perimeter fence onto the airport rather than crashing on houses.
So the trick must have some merit........
http://news.bbc.co.uk/1/hi/uk/8505163.stm
Cusco
He didn't have the luxury option of adding more power and the manoeuvre got him over the perimeter fence onto the airport rather than crashing on houses.
So the trick must have some merit........
http://news.bbc.co.uk/1/hi/uk/8505163.stm
Cusco
Last edited by Cusco; 26th Apr 2015 at 09:48.
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Cusco
Its a form of drag and we are talking about energy management so I can see occasions when removing the drag part of the flap stages could be useful.
In an engine failure full flap should be taken when assured of landing but pilots do get it wrong and I could see that removing that drag could extend the glide range
I know in my Seneca Five days I rarely used full flap for landing unless the runway /strip was very short especially in a twin you want as little drag configured to land as possible in the event of an engine failure or even a go around.
Pace
Its a form of drag and we are talking about energy management so I can see occasions when removing the drag part of the flap stages could be useful.
In an engine failure full flap should be taken when assured of landing but pilots do get it wrong and I could see that removing that drag could extend the glide range
I know in my Seneca Five days I rarely used full flap for landing unless the runway /strip was very short especially in a twin you want as little drag configured to land as possible in the event of an engine failure or even a go around.
Pace
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I would retract some flap on final approach, if I had just applied power for a go around. Otherwise, I would not.
I would be embarrassed to have placed myself in a phase of flight in a GA plane where raising flap for a continued landing could have any plausible benefit.
I've never flown a 777, so have no qualified comment on flaps use on that aircraft.
I would be embarrassed to have placed myself in a phase of flight in a GA plane where raising flap for a continued landing could have any plausible benefit.
I've never flown a 777, so have no qualified comment on flaps use on that aircraft.
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I agree with what's been said. It's not something for an inexperienced pilot, and it's a little unusual within a GA environment.
But if you know the aircraft, if you're above Vs and if you're prepared to handle the inevitable pitch change, then you can indeed use the last stages of flaps as a form of energy (drag) control.
At the very least you're showing some courtesy to noise-sensitive neighbors. And it's good practice for an engine failure scenario.
I have myself retracted flaps on final, but for a different reason. I was on a straight-in approach in a fairly strong headwind (35 knots or so). I was fully configured for landing, with full flaps, maybe a mile away, and the runway did not get any bigger anymore. So I added some power, removed the last stage of flap, and added the flaps again when I was just before the threshold.
To me, flaps are just one of the flight controls. You need to know what they're doing, and how you can use them in different scenarios, within their operational limits. Just applying them by rote as you learned on the PPL course is good and will keep you safe, but there are other ways of doing things that are equally safe and maybe more effective.
But if you know the aircraft, if you're above Vs and if you're prepared to handle the inevitable pitch change, then you can indeed use the last stages of flaps as a form of energy (drag) control.
At the very least you're showing some courtesy to noise-sensitive neighbors. And it's good practice for an engine failure scenario.
I have myself retracted flaps on final, but for a different reason. I was on a straight-in approach in a fairly strong headwind (35 knots or so). I was fully configured for landing, with full flaps, maybe a mile away, and the runway did not get any bigger anymore. So I added some power, removed the last stage of flap, and added the flaps again when I was just before the threshold.
To me, flaps are just one of the flight controls. You need to know what they're doing, and how you can use them in different scenarios, within their operational limits. Just applying them by rote as you learned on the PPL course is good and will keep you safe, but there are other ways of doing things that are equally safe and maybe more effective.
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Flaps on C172 are Fowler, and increase wing area as well as lift and drag. A go-around from a flaps 40 approach demands flaps be reduced to 20, as that last 20 - 40 is nearly all drag, the last 10 a LOT of drag. It also demands a very strong forward push on the yoke to maintain attitude until the drag-flap (40 back to 20) is retracted and the aeroplane re-trimmed. I imagine this is why Cessna limited full flap to 30 on later models - a retrograde step IMO. Just about the best feature (it an't got many!) of the 172 was that 40 degrees of Fowler flap.
Reducing from 30 to 20 will remove mostly drag, not reduce much lift, and not reduce the wing area so is a safe thing to do on final just as long as you are sure the retraction stops at flaps 20 and not beyond!
However it is poor technique and indicates poor approach planning. You shouldn't commit to flaps 30, still less flaps 40, until the point in the approach where such a setting is appropriate.
I only remember once retracting flap on final. It was in a PA38 at Alderney. I knew the threshold was near a cliff edge, and with the fairly strong wind there would be a very strong downdraft on final where the wind flowed over the cliff edge and down. But the 'clutching hand' that pulled the aeroplane seawards was far stronger than I had anticipated. The simple flaps on the Piper were retracted to first stage as full power was applied and we made the runway. I doubt we would have with full flap left extended.
Reducing from 30 to 20 will remove mostly drag, not reduce much lift, and not reduce the wing area so is a safe thing to do on final just as long as you are sure the retraction stops at flaps 20 and not beyond!
However it is poor technique and indicates poor approach planning. You shouldn't commit to flaps 30, still less flaps 40, until the point in the approach where such a setting is appropriate.
I only remember once retracting flap on final. It was in a PA38 at Alderney. I knew the threshold was near a cliff edge, and with the fairly strong wind there would be a very strong downdraft on final where the wind flowed over the cliff edge and down. But the 'clutching hand' that pulled the aeroplane seawards was far stronger than I had anticipated. The simple flaps on the Piper were retracted to first stage as full power was applied and we made the runway. I doubt we would have with full flap left extended.
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SSD
I agree with what you are saying it is a bad piece of planning and why would you want 40 degrees unless landing on the shortest runway with a steep descent?
In which case take the last stage when all is looking good for a landing and not before.
Nevertheless its a big chunk of drag like an air brake and should be regarded as such pop the air break section away when you do not want that drag.
again its energy management which is not fully taught and knowing your aeroplane
Pace
I agree with what you are saying it is a bad piece of planning and why would you want 40 degrees unless landing on the shortest runway with a steep descent?
In which case take the last stage when all is looking good for a landing and not before.
Nevertheless its a big chunk of drag like an air brake and should be regarded as such pop the air break section away when you do not want that drag.
again its energy management which is not fully taught and knowing your aeroplane
Pace
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It is true that the flaps are a flight control, but they are considered a secondary flight control and not the primary controls of elevator, aileron and rudder.
Perhaps your flap boy was trying to show off. But you concentrate on the fundamentals and it will pay off.
Perhaps your flap boy was trying to show off. But you concentrate on the fundamentals and it will pay off.
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As a low hour pilot, I prefer to be well set up on late final. Maintaining correct speed for me is not a huge challenge, but requires a little effort. Are we not taught to do this for a reason? The change attitude, airspeed is significant when changing flap settings. Adding a little more throttle can fix the issue and seem less fraught with danger to me than reducing flap.
Call me simple, but I prefer the low risk approach to flying.
Call me simple, but I prefer the low risk approach to flying.
It’s obviously something you can do but I wouldn’t recommend it as normal practice. In some types it could bite quite badly at low level, especially if you were a bit on the slow side.
It’s a useful technique if you’re undershooting with no increase in power available and still have some air underneath you. Bear in mind that the initial effect will be for the undershoot to worsen before it gets better.
The pilot in the OP seems to have decided on a land flap setting, then changed it on the way down for reasons not much connected with airmanship. Although it probably didn’t matter in this instance, it’s a sloppy way of doing things and if it became a habit, could cause problems on limiting runways. Stable approaches aren’t just a good idea for airliners...
It’s a useful technique if you’re undershooting with no increase in power available and still have some air underneath you. Bear in mind that the initial effect will be for the undershoot to worsen before it gets better.
The pilot in the OP seems to have decided on a land flap setting, then changed it on the way down for reasons not much connected with airmanship. Although it probably didn’t matter in this instance, it’s a sloppy way of doing things and if it became a habit, could cause problems on limiting runways. Stable approaches aren’t just a good idea for airliners...
