Reducing flaps on short finals

[mixturerichlean]

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.

[Mach Jump]

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:ok:

[skyhighfallguy]

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.

[piperboy84]

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.

[MarcK]

Raising the flaps increases the stall speed, so if he was slow to start...

[Radix]

..........

[Jan Olieslagers]

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.

[ChickenHouse]

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!

[Pace]

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

[Cows getting bigger]

Your COOL guy would have been far more COOL if he had got it right in the first place. :)

[Cusco]

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

[Pace]

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

[9 lives]

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.

[BackPacker]

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.

[Shaggy Sheep Driver]

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.

[Pace]

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

[skyhighfallguy]

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.

[Andy_P]

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.

[Radix]

..........

[FullWings]

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...

[Flyingmac]

Judging by some of the comments, you wouldn't think that 40 degrees was the recommended approach flap setting for a large chunk of the light GA fleet.:*

[N-Jacko]

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 couldn't disagree more strongly. We have primary flying controls for power, lift, drag, pitch, roll and yaw. There is nothing embarrassing about practising for the day when one or more of those controls is t/u or simply not up to the task. Catch a 500 fpm downdraft out of nowhere on short final to an alpine one-way like Corlier? Well, you can smack into the cliff face with old Steppy, or you can add full power, pitch forward and lose some flap while he's still looking for his flight manual.:ugh:

[fireflybob]

Some aircraft have large trim changes if you change flap settings - maybe not such a good idea when you're close to the ground on final approach.

[skyhighfallguy]

I shudder to think that using flaps to control glidepath is really a normal thing

Certainly one can prove you can fly around the pattern with elevator trim and opening and closing the doors of the plane to make turns

BUT YOU DON'T DO THAT normally.

And what would the pilot in question do if he were flying a plane that didn't have flaps! OH NO, he couldn't possibly fly a plane that didn't have flaps.

And what if he had an electrical failure and couldn't change the flaps?

IF you want to experiment, you can do it without passengers on board.

It isn't cute, it isn't right, it isn't good flying.


And using the BA 777 at heathrow as an example is pretty lame. And didn't the captain lose his job? Hmmmm.

[N-Jacko]

Yes, the trim wheel. I trim for level flight with one stage of flap on downwind (or "outbound" on a one-way) and then leave it alone. I don't have enough hands to fiddle with the trim wheel on final, while adding trim reduces the effectiveness of the elevator (by the area of the tab) and interferes with muscle memory for a constant apparent rate of closure approach.

If a Maule is trimmed level downwind with take-off flap, it's pretty well set for a go-around on airfields which offer that luxury.

Your machine may vary, and you may prefer to operate differently, so like all the other drivel on this forum, the above advice is worth what you pay for it.

[IFMU]

My SGS 1-35C had flaps for glidepath control. I have removed flaps on approach for that glider.

Glider, pawnee, 172, arrow - most of the end of the flap travel is drag, not lift. If you go to power up and the power is not there, do you give up? Personally I have played with them all.

You can argue that needing to change flap settings, or power settings, or sideslip is a display of poor planning. It is wonderful when you plan well enough, and that the conditions are predictable enough that you don't have to do anything. Often what separates the pilots from the aircraft drivers is how they react when things don't go as planned.

[9 lives]

Catch a 500 fpm downdraft out of nowhere on short final

Flaps are not a flight control, they are a lift and drag device. For the occasions when you encounter rapidly settling or rising air, you fly the plane through it. You manage pitch and power to maintain an acceptable approach path, or go around.

Your well planned approach should have built in allowance for variations, because your judgement has enabled you to plan well. In the case of a sudden and unforeseen change in the air movement, electric flaps will be much too slow to have any beneficial affect as a "flight control". Manual flaps are rapid enough, but the danger in accidentally going from full flap to zero flap at a slower approach speed far outweighs the benefit in changing approach path.

Happily, I have reviewed the flight manual prior to flying the aircraft, and know that no aircraft I have ever flown includes reducing flap extension during a continued approach as an emergency or normal procedure.

During certification testing, it will have been demonstrated that the most rapid selection from full to zero flap which can be made, can be flown through and recovered, but there will usually be quite a lot of altitude loss.

We aspire to a stabilized approach, which progressively configures the aircraft for landing. Retracting flaps would not conform to this. It "de-configuers" the aircraft, and introduces the risk that the landing gear might be mistakenly retracted. If a pilot I were training did this, we would have a long talk about it, and they would not do it again, if they wanted my signoff.

If you feel the need to reduce flap extension during final approach, you should go around, things are too far gone to continue a normal approach.

adding trim reduces the effectiveness of the elevator (by the area of the tab)

Not in any certified aircraft it doesn't. In some types, adverse elevator trim can be effectively used to increase elevator effectiveness, albeit with a lot of muscle needed.

[skyhighfallguy]

let's get something straight, if you want to play around with secondary flight controls instead of primary flight controls, fine

but do it by yourself without passengers.


And you should always be in trim. Always except perhaps in the last seconds of flare.

Muscle memory is fine, but if you are on final you should be able to let go of the control wheel and the plane remain where you left it in calm air.

I'd like to see those proponents of flaps as glidepath control do it on a normal FAA checkride . IF the examiner was generous he would let you do it again. If not, he would fail you and I would have such a good laugh.

[fujii]

Short FINAL, not short finals.

The OP mentions 400 to 500 feet. In a normal approach, who'd consider this to be short?

[9 lives]

"Final" Indeed! We shall do one final approach to one landing!

The OP mentions 400 to 500 feet. In a normal approach, who'd consider this to be short?

500 feet up on final is not so much "short" as it is in the phase of the final approach where there should be no guesswork or fiddling to be done, other than flying a stabilized, and configured approach to the landing. De-configuring the plane at that point would be rather poor airmanship!

[wiggy]

Minor point of order from a lurker:

And using the BA 777 at heathrow as an example is pretty lame. And didn't the captain lose his job?

To cut to the chase, no.

For reasons various he decided to leave BA a while after the accident..he subsequently returned to the company with no loss of seniority. He is still a captain on the C777 for BA.

Hope that helps/clarifies the matter..back to lurking.

[JEM60]

Yes, PB did rejoin BA, but the last I heard had decided to take voluntary redundancy after a short time. MAY be wrong. Sorry about thread drift. 172 definitely heavy push forward on a go-round on 40 flaps!!. Much re-trimming etc.,

[Cusco]

And using the BA 777 at heathrow as an example is pretty lame.


What tosh: the 777 scenario was virtually identical to the OP:

PB in 777 realised he was sinking too fast with landing drag flaps out and with no power available retracted the flaps.

Reduced drag thereby gave him less sink, just enough to hop over the fence and avoid landing on buildings outside the airport.

The OP's scenario was of the pilot in a situation where on final he needed more power (which in this case was available to him unlike the 777) but chose not to use power and instead retracted the flaps and got in.

Both scenarios highly non-standard, virtually identical and not to be recommended, but both achieved a survivable result.


Cusco

[Flyingmac]

adding trim reduces the effectiveness of the elevator (by the area of the tab)
Not in any certified aircraft it doesn't. In some types, adverse elevator trim can be effectively used to increase elevator effectiveness, albeit with a lot of muscle needed.

Yes it does.

[Zonkor]

A related topic is dumping flaps on touchdown, which is a quite widespread practice for short-field landings (or in microlight flying to prevent the damn thing from bouncing off again).

I've seen a very experienced pilot do it in one combined move during roundout. We came in quite steeply with full flaps and speed just above Vs0 on short final, then just above the ground he did an aggressive flare and raised flaps quickly. Elevator balanced out loss of lift nicely, making it a pleasant arrival (and the shortest landing I've ever witnessed in a spam can).

[Genghis the Engineer]

Step Turn wrote


What tosh: the 777 scenario was virtually identical to the OP:

PB in 777 realised he was sinking too fast with landing drag flaps out and with no power available retracted the flaps.

Reduced drag thereby gave him less sink, just enough to hop over the fence and avoid landing on buildings outside the airport.

The OP's scenario was of the pilot in a situation where on final he needed more power (which in this case was available to him unlike the 777) but chose not to use power and instead retracted the flaps and got in.

Both scenarios highly non-standard, virtually identical and not to be recommended, but both achieved a survivable result.


Cusco

IIRC, the AAIB report on the 777 prang at LHR concluded that partially raising the flaps had no significant effect upon the outcomes.

G

[Cusco]

@GTE who wrote
IIRC, the AAIB report on the 777 prang at LHR concluded that partially raising the flaps had no significant effect upon the outcomes.

G

That's not what the report says:

Direct quote from the AAIB (below) shows that without the flap reduction the 777 would have crashed through the ILS antenna:

As it was, the flap reduction moved point of ground contact 50m towards the runway threshold, missing the ILS:threshold

quote from AAIB Report:

Actions of the Commander

The Commander, on realising that he was unable to obtain any additional thrust from the engines, attempted to reduce drag of the aircraft by reducing the flap setting. However, the aircraft was now so close to the ground that there was little time for the beneficial effects of this action to take effect.

The action in reducing the flap setting was prompt and resulted in a reduction of the aerodynamic drag, with minimal effect on the aircraft stall speed: it moved the point of initial ground contact about 50m towards the runway threshold. Had the flaps remained at FLAP 30, the touchdown would have been just before the ILS antenna, but still within the airfield boundary. The effects of contact with the ILS antenna are unknown but such contact would probably have led to more substantial structural damage to the aircraft.

OK the pilot in his book thought he would have hit houses but his actions IMHO (and those of the AAIB) despite the lateness of the flap reduction, obtained some benefit .

I took a particular interest in this accident as at the time one of our aeroplane group members was a BA777 Captain, knew PB and I discussed it with him extensively.

Cusco

[skyhighfallguy]

cusco

TOSH ON YOU.

the 777 thing was an emergency

the 172 change of flaps, when power was easily changeable and available was not an emergency.

Can YOU see the TOSHING difference?


how many times do BA777's practice changing flaps below 500' or 1000' with a full load of passengers. I certainly hope the answer is 0.

[Cusco]

Oh dear:

The simple(and only) point that I am making is that, in the absence of power whether voluntary or involuntary, the dumping of flap in the OP's mate's case and Capt Burkill in the 777 had the same effect: prolonging the glide just enough - in the OPs case to land and in the 777's case to miss ploughing through the ILS gantry.

No more, no less.

I'm not commenting on the wisdom of either.

Oh and GTE's memory of the AAIB report was slightly adrift.

Chill chaps, this is PPRuNe after all.;)

Cusco

[wiggy]

if you're going to keep bringing the 777 and "landing/drag flap" into this.

Flaps 30, 25 and Flap 20 are all valid landing flap settings on the 777, though F20 is reserved for some non-normal situations (usually but not exclusively if performance is an issue, e.g single engine landing). PB thought out of the box and swopped one valid landing flap setting for another one, albeit at very low level.....

[abgd]

0-40 are all valid landing settings on a 172, aren't they?

[Jetblu]

Many years ago flying an Arrow III : on finals, about 200 -300ft I pulled 3rd stage of flap. Suddenly, the spring mechanism went twang, the bar went to the floor and I lost all flap. All overcome with a touch of power and slight pitch up.

I've often played about with flap during different phases. A common short field take off technique was to pull 2 stages of flap at 50 knots and bounce her off.
Again, not in the POH but it works.

[Above The Clouds]

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.


I wonder if the OP or anyone else has considered that maybe this pilot was just practising a glide approach after simulating an engine failure downwind, that would make the above procedure a perfectly normal technique to obtain the correct touchdown point on your runway, or an off airport landing in a field, personally I practice glide approaches regularly for this reason.

[Pace]

The problem with messing around with flaps is selecting the wrong flap setting. Some are electric others are manually operated and the approach should be stabilised.
We use 1.3 times the stall in a given configuration so your stall speed will be different with zero flap to full flap and that needs to be considered.

Also to be considered is more aircraft specific, the type of flap and what settings are drag and what settings are more lift so it really comes down to knowing your aircraft.

If i had an engine failure took full flap and realised I had got it wrong and was going to come down short of my desired spot then sure get rid of that drag no matter whether its from flaps gear speed brakes etc.

I too used that technique of on a short take off leaving the aircraft clean and applying takeoff flap approaching VR. The real danger is missing the flap or taking the wrong degree of flap while your distracted bouncing along a field and really distraction is the key word as your full attention should be on the takeoff not looking down at flap settings

Pace

[Sillert,V.I.]

As others have said, you could one day find yourself in an emergency where this remains the last available option to extend the glide.

I'd say the technique of using flaps for energy management in a power-off approach is both safest & most useful in types with manual flaps where there is no significant pitch change with flap retraction; the tomahawk & hershey-bar cherokees are obvious examples. If your flaps are electrically-driven, in a real emergency, you'd likely want the master switch off before you reached the point where manipulating the flaps in this way would be helpful.

If you have the right type of aircraft, I think it's a technique worth practicing; the last thing you want to be doing in any emergency is trying something out for the first time :eek: -though, again as others have said, not with passengers:=.

It's also one way of achieving a precision spot landing from a glide approach. It's a long, long time ago now, but I remember using the technique (in a PA38) during this part of my initial PPL skills test - and since I passed, it must have been acceptable to my examiner.

But I'm struggling to think of a valid reason to retract the flaps during a normal powered approach - the throttle is your primary energy management
control.

[Crash one]

My aircraft has such manually operated flaps, it also has a separate trim tab operated by the flaps. Last Saturday was windy, and with a 25knot crosswind I elected to land at some 30deg to the runway heading with just 200metres to touch down and roll out between the edge of the grass and an avgas store. Closed the throttle at 200ft, flap lever in one hand stick in the other, I was able to touchdown within a foot or so of where I wanted it, stopped in 130metres.
Taxiing in it slowly described a very gentle ground loop through 180 deg, keeping the tail down I managed to keep it going all the way round. First for me, completely un commanded out of control but very gentle. I love that aircraft, it lets me get away with murder.
Electric flaps are a different thing altogether.

[fireflybob]

Perhaps we should also mention that it has been known for pilots to select gear rather than flaps in more complex aircraft.....

[Pull what]

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.


Landed on the keys! Rather says it all doesn't it, does this pilot wear spurs as well by any chance?


Flaps on C172 are Fowler, Slotted Fowler Flaps actually, or to be absolutely correct single slotted Fowler flaps

What your describing is a non standard event and not best practice, as is landing on the keys but for some pilots non standard events are part of their normal flying and you can read much more about them in AAIB bulletins or here on Pprune.

The most important thing on the latter stage of the approach is to fully stabilise the approach in that the speed should be on target, the aircraft should be on the correct glide path, on the centreline and correctly configured with landing flap(and trimmed). The stabilisation height should be a target but most GA pilots have never even heard of stabilisation height so its hardly surprising they dont make an attempt to stabilise the aircraft by the target height. We/I use 200 feet on our training aircraft and that also coincides with the obstructed runway solo go around decision height.

Lifting flap at 400-500 feet is not much different to selecting flaps full in terms of stabilisation, both are de stabilising but thats not really the point, the point is whatever you have done to destabilise the aircraft on the approach should have it affects negated by the stabilisation height.

As has already been mentioned should an abnormal or emergency event occur on final the decision to lift flap may be the best decision on the day and shouldn't be overshadowed by folklore. This however wasn't an abnormal or emergency event and neither was it best practice in my opinion but Ive seen some very fine pilots roll an aircraft at 400 feet on finals but as I said earlier he eventually found his way into an AAIB bulletin and the local crematorium(from stall/spin at altitude in a twin I might add, not final!)

You also asked by the way, " is it safe"? I've yet to find anyone who can define what safe is. I teach instructor candidates to be very careful and sparing in their use of the word safe as ‘safe’ cannot be measured. Many instructors say for instance, “I want to see the student fly a safe approach”. What they really mean is they want to feel safe but feeling safe isnt a measurable value. The parameters of the stabilisation height however are and they are measurable both by the student and the instructor.

[fujii]

Slotted Fowler Flaps actually, or to be absolutely correct single slotted Fowler flaps.

To be absolutely correct, "What your describing..." Should be "What you're describing"

[Sillert,V.I.]

The stabilisation height should be a target but most GA pilots have never even heard of stabilisation height so its hardly surprising they dont make an attempt to stabilise the aircraft by the target height. We/I use 200 feet on our training aircraft and that also coincides with the obstructed runway solo go around decision height.

My own view is that stabilisation height isn't relevant to operating a fixed gear SEP and there are many situations in which you simply can't be stable by 200ft. Landing on a short grass strip with obstructions on the centreline on short final is just one obvious example. The weather will frequently make a mockery of any attempt at stability (my local airport as I type this: EGHH 051350Z 22023G35KT 9999 BKN025 15/08 Q1000); on days like today I'd likely have the flaps up immediately after touchdown to keep a clear differentiation between air and ground ops.

I've frequently made a runway change below 200ft; it certainly used to be common practice at Wycombe for operational reasons (getting out of the way of Lord King's personal transport was one such occasion) and (in perfect weather) I've even made a very low level change from 24 to 27 at EHAM :eek:. (It's been awhile, but as I recall it went something like: "G-xx short final 24" "G-xx cleared land RWY 24" "Cleared land 24 be advised going international on departure G-xx" "Can you make 27" "Affirm" "G-xx cleared land RWY27 no need to acknowledge" :)).

It's important to distinguish being stable with being in control. Light aircraft are generally very manoeuvrable and imposing stable approach criteria is just denying the pilot the advantages of this manoeuvrability. OTOH, if you are in any doubt at all about being in control on short final, then I'd agree a GA is called for, and I can see the merit of imposing a commit height for this.

I'd agree teaching a stabilised approach with a commit height makes sense if the student's short term aspirations are the RHS of a B738; but IMO it would be better if those folks were never let anywhere near an SEP and we made the most of their brief time in training by concentrating on matters relevant to airliner operation. Unlike some here, I've no issue about low time pilots in the RHS of an airliner if properly trained, but that training needs to be relevant to the job they're actually being asked to do.

[Above The Clouds]

Pull What
The most important thing on the latter stage of the approach is to fully stabilise the approach in that the speed should be on target, the aircraft should be on the correct glide path, on the centreline and correctly configured with landing flap


Oh my, another school teaching Airbus, Boeing approaches in a Cessna 150, I suppose everything will be fine so long as they are on the glide path at 10 miles fully configured, what ever happened to doing a visual approach visually.

[abgd]

On my home runway there's a big patch of sink that means that anybody on a stabilised approach at 200 feet is setting themselves up to land short.

I aim to fly every approach high and use sideslip to correct it. Partly because it's fun, and partly because it seems like a safer thing to do than to power in from miles out, with the risk of landing short if you have an engine failure.

Perhaps this is the real reason reducing flaps is a bad idea: there are better ways of controlling your glide angle. It's all very well using a mechanism that enables you to steepen your approach whenever you feel high, but at least if you aim to go in with a degree of slip you can reduce your glide angle without having to cope with all the trim changes and changes in stall speed that result from playing with the flaps.

[Sillert,V.I.]

I'd agree that slipping is perhaps more useful for those with some experience, though it also depends somewhat on aircraft type.

For example, I learned to fly on the PA-38, which has no signficant pitch change with flap movement; the stall speed difference between clean & dirty is 2kt & it has manually controlled flaps. My instructor was perfectly happy to let me practice glide approaches solo using the flaps as makeshift airbrakes. I was lucky enough to nail one just right for my final handling test.

The PA-38 slips well, too - but it bites hard if stalled with crossed controls & the instructors didn't encourage PPL students to slip it solo.

You'll never forget your first spin in a tommie.

[skyhighfallguy]

sillert vi

yes, tomahawk spins are a wakeup call. good idea to secure everything in back before you spin.

So many people write about engine failure, and certainly it can happen. So can spar failure.

but it is best to control a plane with primary flight controls. changing flaps seems like such a waste.

I've taught many people to fly and would not spend more than a few minutes of briefing on non standard ways to fly the plane. things like in an emergency like a stuck throttle, try using the mixture to control power, or if the ailerons fail, a little rudder and not too sharp a turn.

But flight path control with flaps belongs with things like ground signals to search aircraft. Worth talking about, but I would not make a student demonstrate the signal for injured person.

Wondering if the same flap jugglers even know the agreed upon signal from surface to air for injured person?

[Sillert,V.I.]

Wondering if the same flap jugglers even know the agreed upon signal from surface to air for injured person?

Isn't this the one where you lie flat on your back with your hands straight up above your head?

The one that really threw me was the first time I was asked to fly a circuit with the ASI covered up.

Sometimes I wonder if the training's more dangerous than the emergency.

But I stand firm on using flaps as airbrakes after engine failure. When the donk quits, you're flying a glider - and glider pilots routinely land using airbrakes for flight path control.

[9 lives]

But I stand firm on using flaps as airbrakes after engine failure.

I prefer to keep drag to a minimum following an engine failure. I will extend flaps for a landing as appropriate, and to increase drag appropriately on final approach. In the case of a forced approach, this would be very late in final, and not to be fiddled with after that. I'll be too focused on making a safe landing.

When the donk quits, you're flying a glider - and glider pilots routinely land using airbrakes for flight path control.

No, if an engine fails, you're flying a power plane without power, nearly none are equipped with airbrakes. A glider is a different type of aircraft, equipped differently, and to be flown differently.

Airbrakes are airbrakes, and flaps are flaps. Airbrakes are not designed to produce lift when they are applied. Airbrakes are intended to be modulated during a normal approach to create drag as desired without a lift change, flaps are very certainly not - they create both lift and drag in varying amounts per extension.

It is very poor practice to attempt to modulate lift with flaps. I agree that with a manual flap plane it is possible, but on final approach, silly, and, if not rather unsafe, at least needlessly distracting. For electric flaps, hopeless - they just don't move quickly enough.

If you feel that you need to reduce the flap extension on final, you should be abandoning that approach - you got it wrong.

The most important thing on the latter stage of the approach is to fully stabilise the approach in that the speed should be on target, the aircraft should be on the correct glide path, on the centreline and correctly configured with landing flap(and trimmed). The stabilisation height should be a target but most GA pilots have never even heard of stabilisation height so its hardly surprising they dont make an attempt to stabilise the aircraft by the target height. We/I use 200 feet on our training aircraft and that also coincides with the obstructed runway solo go around decision height.


This is much more simple than that. Stabilized, in the context of a GA aircraft approach has no numbers which make it right or wrong. It is simply, at every point in the approach, are you continuing what you are doing to make a smooth transition from flight to rolling down the runway. If you are continuing to descend, maintain a speed with reductions as needed, and configure the aircraft for landing, you have a stable approach. It could be steep or shallow, turning or straight - but it is not doing then undoing - it's continuing to do. You planned a "good" approach to demonstrate good airmanship, you're going to continue to do that, not start to undo it partway along! If you need to undo it, undo it properly and go around.

If you are flying a manual flap Cessna, with 40 extended, and you think to retract to 20, and miss, and get to zero, you'd better get full power in right away, 'cause you're dropping. That is anything but a stabilized approach.

There is no power plane flight manual which is going to include the modulation of flaps for "control" of the aircraft. Why would pilots think that this is a good idea - are they test pilots?

Lifting flap at 400-500 feet is not much different to selecting flaps full in terms of stabilisation, both are de stabilising but thats not really the point, the point is whatever you have done to destabilise the aircraft on the approach should have it affects negated by the stabilisation height.

I disagree. leaving the flap as is, or extending more as required, will continue the stable trend toward slowing and increasing lift as will be desirable as you enter the flare. Raising flaps reduces lift and drag, and not necessarily in proportion. As lift and drag, compared to "normal" flight, are desirable at the flare, reducing them during approach is destabilizing.

[skyhighfallguy]

good for you sillert



and if you use flaps to increase drag if your engine has really quit, well, do what you have to do to stay safe.

IT IS THE IDEA of using flaps instead of changing power settings that is not a good one.

[Pace]

Obviously it's bad practise to use flaps to popping them up and down like a drag control! Maybe it's having such a long history flying light twins where drag can be an enemy that I will only add drag when needed!
But here we are looking at an engine failure in a light single! Again drag should be only added when you need it and full flap when assured of a landing!
But pilots get it wrong sadly and lateral thinking in that situation should mean a pilot considers that extra drag and gets rid of it better that than to continue a speed glide profile into trees short of your landing spot!
I would not recommend the use of flaps in that manner in normal circumstances but would encourage pilots to be aware of that drag in emergencies

Pace

[ANOpax]

Slotted Fowler Flaps actually, or to be absolutely correct single slotted Fowler flaps.

To be absolutely correct, "What your describing..." Should be "What you're describing"

I was once told that grammar is the difference between knowing your **** and knowing you're ****... :}

[oggers]

Obviously when reducing flap the aircraft will sink before the glide path flattens out so there is the potential to exacerbate an undershoot. But let's have a sense of proportion here, reducing flap from 30 to 20 above 400' in a C172 is safe, and it worked out nicely.

[Radix]

..........

[9 lives]

But let's have a sense of proportion here, reducing flap from 30 to 20 above 400' in a C172 is safe, and it worked out nicely.

"Safe" is in proportion too. It is less safe to retract flaps on final, than it is to leave them as set. Though I agree that change in those conditions should not create an unsafe situation, it is taking the plane towards an unsafe condition, where leaving the flaps along would not. It is poor form to get used to doing things on final approach which destabilize the approach, or tend to undo a landing configuration.

The fact that it might have worked out nicely is not justification for doing it. There are a lot of things which can be done in planes, and will work out nicely if done under certain conditions, which still should not be done.

Piloting is very well established now. Aside from new systems, there is not much new about piloting planes. If there is, there will be a procedure and training for doing it. I have never heard of a procedure for retracting flaps during a continued approach to landing. I have heard of maintained a stabilized approach.

[oggers]

Step Turn:

The fact that it might have worked out nicely is not justification for doing it.

The justification for doing it was that having got down to the desired glidepath he wanted to retract a notch of flap rather than carry the extra drag he no longer needed.

There are a lot of things which can be done in planes, and will work out nicely if done under certain conditions, which still should not be done.

Yeah but I, amongst others, do not agree with you that reducing flap from 30 to 20 at 450' in a cessna is one of them per se.

Though I agree that change in those conditions should not create an unsafe situation, it is taking the plane towards an unsafe condition

The condition he was taking the plane towards was 450', flaps 20, on the desired glidepath.

It is poor form to get used to doing things on final approach which destabilize the approach, or tend to undo a landing configuration.

It is entirely feasible that the pilot in question possesses the modest amount of grey matter required to understand that what worked at 450' in a C172 might not be so clever at 100', or perhaps approaching the middle marker in a 777.

[9 lives]

Okay, opening my mind...

Can anyone present any authoritative training document, standard, or aircraft normal procedure, which describes retracting flaps for a continued approach in a powered GA plane?

Test pilots and flight standards people develop and approve operating techniques for aircraft. Is anyone aware this has been done for this technique?

Is it trained anywhere in formal flight training?

Are there stated limitations or guidance as to when to do it and when not?

[darkroomsource]

It's like standing on the top rung of a step ladder.
You can do it, and as long as you're careful, you'll be OK.
But there have been a few people who've not done so well by it, so the manufacturer puts a warning on that says "don't do this".

If the manufacturer puts a warning on it that says "don't do this", and you chose to do it, then you're the one responsible if something goes wrong.

It seems to me that most small plane manuals I've read say "don't retract flaps on final".

Interestingly though, when just a couple feet above the ground, I was taught to "dump" the flaps in order to lose lift and land much shorter in certain cases (tailwheel, very short field landing). But I was being trained for "bush" flying, and I wouldn't recommend it on planes with "normal" landing gear (by that I mean used to normal stresses).

[Sillert,V.I.]

Is it trained anywhere in formal flight training?



I was taught this during basic PPL training (in a PA-38) as a way of achieving a specific touchdown point from a glide approach.

[Flyingmac]

I've just read the first post. It says the guy was short final at 4/500ft.
I'd need full flap and some slip to get it down from that. Or a stonking headwind. Spoof?:)

[9 lives]

I was taught this during basic PPL training (in a PA-38) as a way of achieving a specific touchdown point from a glide approach.

Hmm, I wonder if that is a part of the approved training syllabus - I've never heard of it. Certainly the Piper Flight Manual would make no mention of it - so yes, it would be top rung of the ladder type stuff. So, yes, the pilot would become responsible for the burst tire, or hard landing if it did not go well.

That said, on a PA-38, you'd be more safe, 'cause changing flap selection is kind of like holding your hand out the window on those! ;)

If I were type training a pilot, retracting the flaps as described would be a fail, the same as if I were type training him on a ladder, standing on the top rung would be a fail. Perhaps others would be more liberal....

[Kommandogerat]

Been lurking for a while and actually have some thing useful to contribute in this case
Have done the this (reduce flaps) few times now where i'm being taught...
And it has been VERY helpful in terms of practicing how to adjust the glide path in different conditions - where i'm learning it seems like the one constant is that the conditions are substantially different EVERY bloody time:bored:

The weekend before last, the Wx was fairly rough 10-15kt S-SE blowing, we were doing some circuits in the Sportstar - Downwind at 1000ft AGL and the instructor pulled the engine - OK no worries i think we complete the circuit normally if we play our cards right.
Established best glide, tightened up the circuit abit and turned final looking fairly good but got the flaps on abit too early considering the fairly strong headwind, at about 350ft suggested bleading the flaps off which i did SLOWLY and we cleared the trees over the fence and managed a slightly faster flapless landing without having to add power.

Weekend just gone the Wx was absolutely :mad: terrible, rip roaring 20-25kt SE blowing, w/sock fully extended - Been looking to get in some solo time but the conditions haven't really been favorable, but the instructor said it would be "Good Practice" for me in any case (haha)!!
On the ground before even starting the A/C, the airspeed indicator needle was being pushed off the stop by the wind gusts:uhoh: and i was thinking this will be fun.

In the circuit doing about 110kt D/wind we were motoring along very quickly indeed but turning final, it felt as if someone had suddenly attached a boat anchor to the tail as we were doing about 60kt IAS but the GPS was showing only barely 20kt ground speed.
If a normal approach profile is like descending down a comfortable flight of stairs, this approach was like going down a ladder forwards whilst staring down at the ground almost vertically. With only idle power on we got 2 stage of flaps (30deg), on then 3 stages (40deg) and we were coming down at about 1000fpm and Looking OK but as we got abit lower the wind intensity was reducing and the instructor suggested going back to the 2nd stage flaps and carrying abit more speed to the runway to ensure we were less vulnerable to changes in the wind, which was now coming from about 20deg to the left (X-wind) to make life even more interesting.
Despite the changes going on i did manage to hold the IAS reasonably constant the whole way down, even if the angle was crazy and so the approach felt stable which earned me a compliment from the instructor.

Fortunately the Adelaide weather forecast is looking good for this weekend so maybe i'll be able able to build some more solo time, but with those experiences under my belt perhaps i'll be slightly better prepared for what might come my way...

[Pace]

K

I don't know who your instructor is but to preach the use of reduction of flaps to control drag under normal operations is a very risk potential practice.

Flaps create lift and drag and there are times when drag is your enemy as well as times when you need it.

Aircraft specific on many types full flap creates more drag than lift and IMO should only be used when assured of a landing and in many cases not used at all.
Only on the very shortest runways/landing strips would I ever take full flap in a Seneca Five.

so to even contemplate removing flap or juggling them up and down like a speed brake is a risky method to use as there is always room for error especially at points of high workload.

To be in a position of having to eliminate that drag means you have got it wrong and its that which needs to be addressed not the use of flaps for drag control in that manner.

There are extreme occasions when removing that drag could save your life and you should be aware of that drag and that option but again its indicative of getting it wrong and should only be used in extreme situations usually engine out. But again why would you take full flap engine out until you are assured of landing from maybe 100 feet agl and when the profile is right to do so?

Pace

[tecman]

Pace, in general I agree with you. That said, in practicing a forced landing, particularly one made under highly variable conditions, I have no problem with an instructor demonstrating what's possible if one's initial asessment of the conditions is imperfect. And it goes without saying that I'd do whatever it took to make a safe landing in a real forced landing case, regardless of offending any purist sensibilities. As I pointed out in another thread, early Cessna manuals (for example) had nothing at all to say about forced landings, so relying solely on a POH reference for all circumstances leads to absurd inflexibility.

I do find K's description of LSA circuit ops odd, though. My own Sunday puddle-jumper these days is effectively an LSA and, in my location, winds are often strong and variable. With these little aircraft it's true that you don't want too much flap over the fence: the stall speeds with full flap are so low you welcome a tiny bit of extra speed to help controllability and reduced flaps to minimize buffeting. (This, mark you, from someone who makes a point of full or near-full flap landings in most GA SEPs except under extreme conditions).

Having said that, the principle is no different to other aircraft: since you know the strong winds will almost guarantee you'll have to cope with quite a bit of wind-shear (speed, direction or both), leave the flaps at a modest setting until you know how things are going to work out. Many LSAs are quite slippery and do require good speed control from late downwind onwards. In my case, I know I'll get a workable descent profile if I'm established on early base at 60kt with 15deg flap. The profile will be up and down a bit but controllable with attitude and power. If it's a bad day on Rottnest Is (for example), I'm more than happy to cross the fence at about 55 kt and land with the initial flap setting.

One aspect which is worth noting is that the flaps in the Sportstar and my P2002JF are relatively modest in effect, compared with the classic barn-door Cessna flaps. I would certainly be making that point to an LSA sudent: as in many other areas, knowledge of type-specific behaviour is essential.

[Pace]

Tecman

I am not at all against Pilots being made aware of any variable sources of drag and in extreme situations i.e. a forced landing being of the mindset to quickly eliminate that drag if needs be.

I am questioning why pilots would take that final application of mostly drag until they really need to and are assured that they will reach their selected landing point?

Too many times under normal circumstances we see pilots dragging in with full flap from way out when full flap IMO should only be taken when assured of a landing and the correct profile for that landing.

Addendum engine out you are limited in still air to the potential energy in the airframe and the various sources of drag more important in that situation that the drag is only added when required as part of your energy management otherwise you are using more of that potential energy to combat needless or ill advised drag

Pace

[darkroomsource]

Yes.
I think we're missing the point here.
If you are in a landing configuration and decide that you need to reduce flaps, then you have done something wrong, and should not be where you are.
The best plan is probably to go-around and get it right, rather than attempt to fix something that's gone wrong.

Flaps do 2 things:
1) enable the plane to fly slower
2) increase drag drastically

the first should be used during certain phases of flight (takeoff in some aeroplanes, approach and landing in most)

the second should only be used when you're "there" on final, as in short-short-final

there are exceptions, of course, but that's what you should be trained for, and what should be "normal" on most light aeroplanes

[tecman]

I think we're in violent agreement about what's usual. The question was raised of when flap modulation on final might be a justifiable or documented operation. Well, one such operation involves the demonstration of what's possible in unusual circumstances. And, as a previous poster noted, we don't actually know if there was an element of that in the operation described by the OP. (Maybe he should pick up the phone and ask, then put us all out of our misery!).

[Kommandogerat]

Fair comments mostly...

I don't know who your instructor is but to preach the use of reduction of flaps to control drag under normal operations is a very risk potential practiceThe situations i described definitely weren't the norm and no-ones been preaching/teaching that as the standard circuit.
Pretty much every other circuit has involved which is using power and attitude to adjust the glide path in the time honored way.

To be in a position of having to eliminate that drag means you have got it wrong and its that which needs to be addressed not the use of flaps for drag control in that manner.Yeah, point taken - next time i'm doing a glide approach i'll hopefully judge the wind abit better and not jump the gun with the flaps.

It's the same deal with a slip on final approach, we practiced that the other week too, when we needed to lose some height, of course i know it's not a stabilized approach if you have to pull those kind of tricks.

BUT on the other hand if the engine really were to fail, the experience of having practiced these things previously, means that i'd hopefully have half a chance of pulling it off when required

The Sportstar LSA has split flaps and i'm aware that they are quite different to your average GA A/C:
1 notch is 15 deg, gives lift and abit more drag lowers the stall speed
2 notch is 30 deg, gives abit more lift again but with alot more drag.
3 notch is 40 deg, not much more lift but heaps more drag.

60kt is the "normal" approach speed with 2 stages of flap on final.

It has to said also, that there is fairly big change to the trim with and without flaps, so applying and removing SLOWLY is important to avoid ending up in at an undesired attitude.

The other side of the coin was in February this year when it was 38deg C at 9AM in the morning after a couple of heatwave days.
We did quite a few full flap landings that day as the thermal energy coming off the ground was doing it's best to stop us from coming down, at various points the VSI was showing we were getting +200-400FPM on base-final:8!!

Keeps life interesting through...

[Pace]

K

Let me ask you a question? Why would you need to pull the last 3rd notch of flap at all or at minimum till your 50 to 100 feet and assured of landing ?

The only time I can think of is if you are high, need the drag to fly a steep profile onto the runway landing spot.

Pace

[9 lives]

Well, one such operation involves the demonstration of what's possible in unusual circumstances.

And not picking on Tecman, but there are a lot of unusual circumstances which one could dream up, and then a very non standard action to tinker with to try to make it better. Ultimately, you'll come back around to simply applying yourself to fly a good approach and landing. That good approach will include thinking far enough ahead of the plane that you're not extending so much flap so far back that it could create a problem for you down final later.

I have seen pilots with "great new ideas" about how to fly over the decades. Other than incorporating new technology (which flaps are not), I have found that the tried and true methods work best.

There is a veiled suggesting that there is a possible need to modulate flaps down final in some cases. I disagree. Using my own experience as a measure, I have landed more than 75 type of planes more than 30,000 times in 40 years, and I have never thought to reduce the flap setting on a continued approach. Further to that, fewer than 1% of those landings would have been conducted with a flap extension of less than full as I "crossed the fence". From that experience, I just cannot figure out why someone would want to start inventing needless procedures to compensate for poor technique they applied earlier in the approach - just fly the approach right in the first place!

[oggers]

Step

Okay, opening my mind...

Can anyone present any authoritative training document, standard, or aircraft normal procedure, which describes retracting flaps for a continued approach in a powered GA plane?

Test pilots and flight standards people develop and approve operating techniques for aircraft. Is anyone aware this has been done for this technique?

Is it trained anywhere in formal flight training?

Are there stated limitations or guidance as to when to do it and when not?

But you are not opening your mind, you are closing it off to any answer that has not already been provided by authority. So let's turn the question around and ask where is it forbidden for flaps to be raised from 30 to 20 above 400' in a C172? Nowhere. And yet there are plenty of references to not reducing flap on 'final'. So where do you draw the line? As long as you are legal and flying within the limits of the aircraft you decide for yourself; that is why it is called a licence and why you have the discretion to do things that some other pilots would consider unwise:

As the carb heat begins to have an effect, consider flying at a reduced power setting (and leaning more if need be), as less volume of air going through the carb at the lower power setting needs less total heat to warm it and melt ice.

...being a case in point.

[Sillert,V.I.]

I don't know who your instructor is but to preach the use of reduction of flaps to control drag under normal operations is a very risk potential practice.

I don't think anyone is suggesting this is an appropriate technique for normal operations. The two applications where it might be useful are the obvious one of a forced landing without power, and in achieving a better score in a spot landing competition (no points for landing short :E).

Pace, my two principal instructors were two of the most experienced chaps you could hope to learn from. They had at least 50,000 hrs between them; one had previously flown spitfires in combat. To say I was in awe of their abilities, both as pilots and as instructors, is a gross understatement.

They may not have taught everything strictly 'by the book', but I remain forever grateful for the tiny part of their combined skill and experience which I somehow managed to assimilate.

I'd suggest they had an excellent handle on the PA-38's capabilities and limitations, whether documented or otherwise; from personal experience I can say the technique works for that type. I can't believe I'd have been taught this at such an early stage if it were inherently unsafe on that aircraft. The only real danger I can see is if there were a problem with the flap operating mechanism; asymmetric flap deployment at such a low level would certainly be an additional difficulty you wouldn't want.

Another interesting memory from the past is they limited me to using one stage of flap for the hour before being sent solo (with clear instructions to deploy full flap for the big event); apparently they'd worked out that the performance two-up on half flap was similar to the performance solo with full flap, so that my first solo approach would be as similar as possible to what I'd just flown.

They certainly pushed the boundaries and I'm sure they broke a few rules, but I believe my training was the better for it.

The statistics for off-airport landings have never made for comforting reading; achieving proficiency in any skill which increases your options should you find yourself in such a situation will, IMO, only improve safety.

I'd also say it's something you need to practice, given the right a/c and situation; just having something demonstrated won't give you either the skill or the confidence to do it for yourself, especially when under pressure.

[Pace]

Step turn

I appreciate your experience and types flown and would agree with your 99% full flap to land with something like the Citation which I fly but would reverse that on something like the Seneca where it was a rare occasion to take full flap!

In the case of the Citation and jet engines drag is added to bring speeds back to VREF on what is quite a slippery airframe while holding a fairly constant thrust setting.

so there has to be an element of type specific but the principal of a stabilised approach hold across the spectrum

Pace

[tecman]

ST, you seemed to have no problem with some intelligent mixture and carb heat tinkering for the purpose of demonstration! I put a careful demonstration of the effect of flap on a glide approach in the same category. As far as I can see, there is no serious advocacy in any other context.

My stats for percentage full-flap landings in GA aircraft would be similar to yours.
The statistic changes slightly for very light aircraft in strong wind conditions.

[9 lives]

Ah, but the difference is that tinkering with mixture to optimize the effect of carb heat has been demonstrated to produce quantifiable and desirable intended results toward an objective. And, any undesired affect can be instantly reversed. Not so with flap extension in some aircraft.

Tinkering with the flaps is evidence of a poorly executed approach, in why was that much flap extended so far back on final - it's just evidence of poor airmanship to find yourself in that situation. If you are flying a Twin Comanche, or Navajo, you'll probably get your knuckles wrapped by the check pilot if you start reducing flap extension on final approach, and certainly in any RG airplane you are increasing the risk of a gear up. ('Cause if you get the gear up, rather than some flap, the plane will feel somewhat similar).

On a checkride I once flew in a C310, I retracted the flaps on touchdown. The check pilot told me that he was going to fail my ride for doing that (inducing risk of gear up). I pointed out where it was a Flight Manual procedure for doing that in the 310. He grimaced and could not fail the check ride, but he still took points off.

For checkrides I fly, I would not sign off the pilot if they did, or thought they needed to retract flaps during a continued approach - more training.... = more $. On that same checkride, if the pilot demonstrated the understanding of the systems to know that leaning with carb heat might improve their situation, I would comment their systems knowledge, and broad thinking.

In a C 172, I cannot suggest that retracting the flaps on final is immanently life threatening, but it's an unnecessary and bad habit, which will have to be unlearned in "bigger" flying environments - so why start?

[tecman]

ST, as I noted in the other thread, if a novice stops the engine during tinkering the results may not be so good. On your reasoning, why take the risk?

So far as changing the flap setting, you seem bent on ignoring the forced landing practice demonstration aspect in favour of an invented strawman standard practice which, as far as I can tell, no one is advocating.

[darkroomsource]

Different planes are different.
And although some might think that not reducing flaps on final is an old wives tail, I know that in some planes the effects of doing so are drastically different than in other planes.

A couple examples, in a Maule, reducing the flaps will "drop" you onto the ground from as much as 10 feet up. Which can be nasty on the gear if you are that high. In a C 172, from 40 degrees to 30 degrees, there's not much but drag difference, so you tend to climb, but from 30 to 20 there's quite a bit of lift that's lost, and you don't climb, you descend. Which is why in a go-around you push throttles/mixture/heat first, and don't raise flaps until you have a positive rate of climb.

So, if you want to descend - either by losing lift, or by stalling - then put in flaps, slow to 1.2x the stall speed for that configuration and then reduce the flaps. Try that in your aeroplane, and see how much (if any) leeway you have. If you happen to be 1.1x stall speed for a configuration when you reduce the flaps, you may find that you need quite a bit of elevation to recover. This would be a good experiment for whatever you're flying.

Although, if you're going to do that experiment, be sure you have plenty of altitude before trying it.

[Kommandogerat]

Let me ask you a question? Why would you need to pull the last 3rd notch of flap at all or at minimum till your 50 to 100 feet and assured of landing ?

The only time I can think of is if you are high, need the drag to fly a steep profile onto the runway landing spot.Yeah look, i can only agree with what your getting at, the need to pull on full flap earlier than you suggest if at all, means you are basically abit too high at that point and need to dissipate that extra energy over the same ground track to the runway.

The session of circuits i mentioned in Feb where it was BLOODY HOT was a good case in point.
(Under the bubble canopy in the Sporty is like being locked in a car in full sun :eek:)
I was flying the roughly the same circuit track across the ground as i'd done previously but we just weren't coming down, so at least initially we needed full flap. After a couple of circuits we could make those adjustments extend downwind which allowed a greater distance traveled to lose the same height.
But the hot weather and thermals still caught us out, one approach that stands out i decided not to go to full flap but consequently we arrived at the threshold a shade too fast and so i got some extra practice holding off as we floated an extra 100m down the runway - still landed with plenty to spare but the difference was obvious.

The more experienced operator than myself could possibly anticipate those conditions adjust to the situation accordingly and get it spot on first shot.

Henceachieving proficiency in any skill which increases your options should you find yourself in such a situation will, IMO, only improve safety.At this stage i'm happy to say my experience is very limited, but in contending with those adverse situations in a controlled way i'm earning the confidence and skills to deliver under pressure when the need arises.

In that sense it's not my best flying that i'm trying to improve, but my worst:)

[Above The Clouds]

Step Turn
In a C 172, I cannot suggest that retracting the flaps on final is immanently life threatening, but it's an unnecessary and bad habit, which will have to be unlearned in "bigger" flying environments - so why start?


Maybe for this reason that I posted earlier in the thread.


I wonder if the OP or anyone else has considered that maybe this pilot was just practising a glide approach after simulating an engine failure downwind, that would make the above procedure a perfectly normal technique to obtain the correct touchdown point on your runway, or an off airport landing in a field


I have always been an advocate of, if you change something and it does not work out or something fails then change back to the original setting.

[oggers]

Ah, but the difference is that tinkering with mixture to optimize the effect of carb heat has been demonstrated to produce quantifiable and desirable intended results toward an objective. And, any undesired affect can be instantly reversed. Not so with flap extension in some aircraft.

Nice try Step but it's not the tinkering with mixture that's the problem but the your advocacy of reducing the power after experiencing carb icing. If you are so keen on doing things by the book only, please feel free to tell us which manual you got that "trick" from?

And your point of "quantifiable and desirable intended results toward an objective" is cobblers. The OP observed that the reduction in flap had the desired result. It is truly absurd to wave that observation away with rhetoric, whilst simultaneously clinging to the belief that reducing engine power is a good antidote for carb icing!

[Jetblu]

It's called make it up as you go along. Step is an instructor who can cite every POH chapter and verse and his word is 'final' innit Step?;)

[9 lives]

I say how I fly, I fly as I say. I'll read what people post, and consider it. I'm not persuaded about retracting flaps on final, so I still won't. I've never need to, why start now?

I'm not an instructor, I'm not checking you out, my advice is free here, so you're getting your money's worth. Fly as safely as you can figure out how, and fly as you would have someone else fly your loved ones in their plane....

I do.

[Sillert,V.I.]

I've never need to, why start now?


You could say the same about any form of emergency training.

You hope you'll never need to do it in anger, but it's reassuring to know you have an additional skill if the worst happens. It's as much about confidence as ability.

There's a trade off between the additional risk of training, and the potential benefit of this training in an emergency situation.

Many aircraft have been lost in training accidents, and I think the balance is shifting. I suspect a PPL course today would be more oriented toward safety than when I learned to fly in the '80's.

[Pace]

This is going round and round in circles :E Think energy management airframe and engine.

Going downhill ;) We are tapping into the potential energy in the airframe as well as from the engine meaning the aircraft will accelerate! steepen that approach and it will accelerate even further.

I always like to think of two throttles the engine one and the elevator so we are managing energy.

We also have various chunks of drag we can tap into airframe, flaps. gear, speed brakes props (esp VP) so we are also tapping into that lot.

Flaps give us lift as well as drag enabling us to land at slower speed.

Going down hill where we are using the potential energy in the airframe means that normally we will use drag to help us slow to a VREF speed by adding chunks of drag on our way down.

going down hill why would we want to remove drag unless we are wanting to go uphill again?

If we loose the engine we now have only one source of energy on a still day from the airframe!
We no longer have an energy source from the engine so trying to fly as far as possible while using as little energy from the airframe means we need to be as clean as possible.

Add drag and we have to use the airframe throttle i.e. the control column by pitching down to get enough energy to combat that drag. Pitching down gives us the energy but looses altitude.

Engine out we should only add drag when we are assured of a landing and sure of the glide path that drag has given.

Get that glide path wrong and the only way to extend the glide to reach a landing spot is to remove the drag or pick another landing spot on our descent profile.

But that is extreme! Normally going downhill add drag in a stabilised approach don't remove it ? Sorry if this is simplistic its not directed at our more advanced posters here :E

In the Citation if I want a steep descent rate or need to control speed pop the speed brakes (another form of useable drag) If my thrust levers are at idle or I need some thrust for engine anti ice . Levelling I will pop them away again think energy management
I suppose the ultimate drag is in the cirrus which gently lowers the aircraft to the ground under the caps

Pace

[9 lives]

Quote:
Originally Posted by Step Turn http://www.pprune.org/images/buttons/viewpost.gif (http://www.pprune.org/private-flying/560508-reducing-flaps-short-finals-5.html#post8977193)
I've never need to, why start now?

You could say the same about any form of emergency training.

:confused: Nothing in 39 years of flying had told me that retracting flaps for a continued landing is a formal emergency procedure, why would I train for it?

I regularly practice formalized emergency procedures, as each pilot should...

I do not extend flaps before I need them, and their extension is appropriate to the continued approach to landing, so it's never been a problem to have to consider retracting them!

I have had an asymmetric flaps failure in a Cessna 180 floatplane, while on the step, in a remote lake, and that was eye opening. I'm heartily glad I was not retracting them down final approach when it happened!

[Sillert,V.I.]

:confused: Nothing in 39 years of flying had told me that retracting flaps for a continued landing is a formal emergency procedure, why would I train for it?

Because it might one day save your life.

Not just if you've misjudged a glide approach. It's possible to lose all engine power after configuring for landing. Certainly unusual, but it has happened.

Think BA38.

[Pace]

Sillert

It is important to think out of the box about energy management and there will be occasions when having got it wrong you need to eliminate drag.I would get rid of gear first even though it meant putting gear down again if in a retractable.
Twin pilots tend to be more drag aware for obvious reasons

But this isn't the point the OP is a student who thinks he can use the last stage of flap as some sort of air brake ? WRONG

Thinking out of the box comes with experience which students do not have and to teach such use of flaps when the instructor would be better teaching how not to be in such a situation is more important

having to retract flap means you have added it too soon so why not concentrate on flying a stabilised approach and energy management and teach students when to add full flap instead of them dragging in with full flap from five miles out! Also teach the glide profile with each stage of flap

Get the fundamentals right especially with students and start to teach them energy management.
when I read the rubbish posted about pitch for speed or power :ugh: I really wonder what students are being taught. Its energy management which is poorly taught and then there would be no need to retract flaps to correct an error?

Step turn is correct overall and I am sure thinks energy management

[9 lives]

Because it might one day save your life.

Please direct me to any written training material provided by a competent authority as to the standards for training for reducing flap setting during a continued approach to landing. Upon seeing how this is formally trained, and to what standard, I will surely consider it.....

[Above The Clouds]

Step Turn

So what you are saying is you never get anything wrong or never mis judge anything, and if you are performing an emergency landing due to engine failure that once you have committed to a field and lowered flaps then realised the approach is not working out correctly you would just continue regardless even if by raising some flap that extended the glide to land safely just because it is not written in a manual.

This sounds as blinkered as the Swissair Flight 111 where the crew refused to deviate from completing the SOP for fuel dumping but where happy to burn up in flight and crash.

[darkroomsource]

Quote:
Originally Posted by Step Turn View Post
Nothing in 39 years of flying had told me that retracting flaps for a continued landing is a formal emergency procedure, why would I train for it?
Because it might one day save your life.

Not just if you've misjudged a glide approach. It's possible to lose all engine power after configuring for landing. Certainly unusual, but it has happened.

Think BA38.

I'm sorry, I don't get the point of this one at all.
If I lose my engine after configured for landing, then I will, well, um, land.

I shouldn't have to change anything in the configuration of the aeroplane to accomplish the landing.

If I'm landing in such a way that I require an engine to land, then I'm descending on too low of a glide slope.

Once I've committed to landing, the only thing I should need the engine for is a go-around.

[9 lives]

So what you are saying is you never get anything wrong or never mis judge an anything,

I once thought I was wrong, but I was mistaken.

if you are performing an emergency landing due to engine failure that once you have committed to a field and lowered flaps then realised the approach is not working out correctly you would just continue regardless even if by raising some flap that extended the glide to land safely just because it is not written in a manual

I have only force landed four times. I've never hurt a plane doing it. My training and practice is to not extend flaps to "drag" (beyond 20 in a Cessna) until landing at the intended place (or at least a suitable place) is very confident. I have slipping as an established, trained and described procedure, to modulate my glidepath, power on or off, as I need, if I got ti wrong enough, that continuing is appropriate, I can go around if I was "mistaken". I use drag flap when that drag is appropriate to the approach, and not before.

I recall that Genghis kindly provided an authoritative reference earlier in this thread, that the modulation of the flaps in the BA 777 LHR crash was not determined to be beneficial, but I do not have first hand knowledge of this event, nor flying 777's. But, I don't accept that event as persuasive that modulation of flaps is a good idea for normal operation.

This thread has an air of suggesting that pilots should be innovative. I can't argue innovative thinking, but I feel that pilots should be innovative within the conventional training, and aircraft operating norms. You can always cite rare extreme situations which demonstrate out of the box thinking, and isn't that nice, but those situations are a long way from a public forum directed toward GA pilots of average skill and experience. I think of the Sioux City Iowa DC-10, we're just not doing that stuff in 172's.

If a pilot does something innovative, which saves lives and property, pat them on the back for a job well done. But be very careful of adding that new technique to the norm, for everyone to include in their day to day flying - that's a huge stretch. We still have the occasional convenience store owner who stands up to a robber and succeeds. But we will always have the authorities say afterwords that the safer thing to do is to hand over the money, and not take risks. If the engine quits, it's safer to follow established techniques to maintain a stabilized - non distracted glide, to a suitable site. The final approach stage of a gliding forced landing in a 172 is NOT the time and place for a GA pilot to start innovating - focus on the task.

So you won't see me on here promoting an unestablished technique which can take the user toward real risk. Modulating the flaps of a 172 500 feet up on approach is not risky, I agree with that - it's just sloppy and needless technique. But modulating the flaps in the same way at 50 feet up will be very dangerous.

In light of the constant complaints about the cost of certified aircraft, do people seriously want the effort expended to test and approve this procedure, and define in pages of data, reports, and flight manual procedures when it may be applied, how, and when it is not safe to do? It's much more cost effective to not endorse it at all - because good flying technique will never call upon it - and keep things more simple.

A C152 aerobat has removable doors. Would you just take them off on a nice day for that breezy feeling while flying? Or would you seek out a two door off approval (which does not exist) to allow that aircraft to be flown with both doors off? Fly the plane in the established configuration.... Or, pay the flight test costs to gather the data to define how the new procedure/configuration might be safely flown. I have approved my 150 to fly with either door off - I innovated, and I paid the approval cost for that.