Flaps on takeoff or not?

[mstram]

When taking off in a light single (C172 etc) from "average" conditions,
less than gross weight, (~2500`-3,000 runway), 20C, light winds, what are the advantages / disadvantages of using one notch of flaps vs no flaps?

I understand that the take off roll is shorter with flaps, and that they are specified for short / soft fields, so what *disadvantage* is there to taking off with them in normal conditions ?

What advantage is there for not using flaps ?

The POH specified 0-10deg for normal takeoff, i.e. apparently leaving it up to pilot's discretion.

Mike

[Flyingmac]

High on the list of useless things in aviation, like fuel in the bowser etc, is runway behind you.

[dublinpilot]

Climb profile is generally better without flaps, although it starts later because it takes longer to get off the runway.

[Mark1234]

As others have said - with flaps, shorter ground run, worse climb performance, without, longer ground run, better climb.

Personally I wouldn't/don't bother using them unless you've got a good reason - i.e. length issues, or a rough field - the liftoff speed diffence is small, and in my experience, very few pilots actually lift the a/c until a bit faster anyway - with flaps your climb speed will be slower, and climb will degrade more per knot over best speed. Your glide will also be more brick like in the event of EFATO.
I'd not automatically use them for higher weights, as climb perfomance is more likely to matter there - it comes down to available ground run, or the need to protect the dangly bits from an unecessary hammering.

One instructor I spoke/checked out with taught a flapped takeoff to "get them used to an after takeoff check/actions" (ab-initio), but didn't have any preference for me to do so.

[Pilot DAR]

On all aircraft I fly, I use the greatest permitted flap setting for all operations at all times. I practice zero flap landings occasionally to keep proficient for a failure.

In general, if you are leaving the runway, and returning to it, at the lower safe airspeed, rather than the faster one, there is simply less wear and tear on the landing gear in general (somebody has to pay for that maintenance, tires and brakes, why increase their cost needlessly?).

Though less likely than general wear and tear, if something does go wrong on the runway, and a bang is to be the result, the damage should be a little less, as you were going a little slower with the flaps extended. If a little oops were to have happened, and the slightly reduced speed prevented it entirely, the use of flaps just prevented an accident! Everyone likes that!

In single Cessnas, an additional reason for flap use is that for takeoff in particular, you will have greater pitch authority with 10-15 flap out than none. This allows the pilot to keep the nosewheel light at all times when power is applied. This is particularly worthwhile, in prevention of nose strut damage, and the risks of sucking debris into the prop. If I'm moving, or have the power applied in a single Cessna, and nealry every other type I fly, the controls are being held all the way back, it's just good discipline....

There will be those who like to point out that less flaps are advisable in crosswind conditions. I am very reluctant to agree with this. If the flap setting is going to make the difference for you making it in or out safely in a crosswind, you were already beyond your personal limits!

My advice, always use the greatest flaps permitted/recommended for the operation.

[bfisk]

In single Cessnas, an additional reason for flap use is that for takeoff in particular, you will have greater pitch authority with 10-15 flap out than none.
Firstly, the approved flap range for takeoff in the Cessna singles I've flown (which is not all of them), is 0-10, but perhaps there's a Cessna in which 15 degrees is allowable?

Secondly I've never had any problems with a lack of pitch authority in a Cessna either, and while easing the load on the nosewheel might be a good thing, your recommendation directly contrary at least to C152, C172 and C172RG POHs. They specifically state that all controls should be utilized for taxiing, and that in a headwind the elevator should be kept neutral, while in a tailwind it should be kept down.

There will be those who like to point out that less flaps are advisable in crosswind conditions. I am very reluctant to agree with this..
In the Cessna singles the maximum permissible crosswind will usually be limited by rudder authority. Basic aerodynamic principles state that you will have more rudder authority at higher IAS. Actually, by looking into the POH (again), it specifically says "when landing in a strong crosswind, use the minimum flap setting required for the field length".


I cannot see how anyone would lend themselves to voluntarily become test pilots when the testing is already done, and the results put into writing. POHs are not scribbled down on a fag pack to be used as guidance, they are the definitive authority on how a particular aircraft should be operated, and I would be extremely cautious on giving conflicting information or advice.

However,
If the flap setting is going to make the difference for you making it in or out safely in a crosswind, you were already beyond your personal limits!
That was very well put and I fully agree!

[Pilot DAR]

Indeed, the flight manuals for the Cessnas mentioned, refer to a specific use of controls while taxied in "strong" winds, and that would prevail over the preservation of the nose strut and propeller. Cessnas which spend that much time taxiing in strong winds, will just have higher maintenance, and risk of minor damage because of that properly executed use of the controls. That's taxiing, not "takeoff" or "landing", when the power comes up, it just became a takeoff, and things change.

The flight manuals do "recommend", or state "preferable" flaps setings, some being less than "full" for certain operations. "recommendations" or stated "preferences" from the aircraft manualfacturer are obviously wise to follow, though do not constitute an "approval" or the opposite of a prohibition. The strongest wording I have ever found in a Cessna flight manual with respect to large flap settings reads: "Flap deflections of 30 and 40 are not recommended at an time for takeoff" (1968 C 150). That's pretty clear, but it is not a prohibition of those settings, and certinly not of 20.

Some Cessnas I have flown do specify as much as 20 flap for takeoff (180, 182, 185, 206, 208) the 208 states that 20 is preferred. I concede that the 172RG recommends zero flap for takeoff.

I've never had problems with pitch authority taxiing Cessnas with zero flaps. I have nearly always had improved pitch authority taxiing with 10 to 15 flap, and that has certainly prevented damage while operating nosewheel Cessnas on rough ground.

Pilots are always advised to operate the aircraft in accordance with the stated terms of the flight manual. Pilots should never operate an aircraft so as to contravene "prohibited", "avoid", "use extreme caution when..." and similar such unmistakable wording. The use of the greatest permitted flap setting during any operation does not contradict any of these.

Squealing an aircraft on with reduced flap, and thus higher speed, so as to maintain that last amount of available rudder authority, is something I have never, and hope to never do. If that amount of rudder is needed to control a cross wind landing, I'll go elsewhere. My personal limit is that if I cannot accomplish a crosswind landing in a Cessna with good control at full flaps, I will go elsewhere. No problems yet.

Yes, Pilots should interpret and follow the wording of the flight manual in the way they feel most safe and comfortable. As a person who writes flight manual supplements for modified aircraft, I can truly say, that I appreciate pilots reading, and taking to heart, the words I have written for their benefit.

[englishal]

One thing about flap setting though...I recently flew an AA5 and as it was the first time, I read the POH looking for S/F technique....There was no mention of flap. So I went without flap and the ground roll seemed pretty long...actually long enough that it didn't leave too many options in case of engine failure.

I had another go and this time used a stage of flap. The aeroplane was airborne far far quicker and climb was not unduly hindered - in fact by the same point in the departure we were a lot higher than the first time..

So, the question is WHY was there no mention of a stage of flap for S/F? The aeroplane could handle a much shorter strip with flap, so it seems daft not to use them??

[Big Pistons Forever]

In the 1976 C150M POH and the 1978 C 152 POH I have, the "takeoff" paragraph in the "Normal Procedures" section has the following statement. "Flap deflections greater than 10 degrees are not approved for takeoff". I am pretty sure at least the later model C 172's (N and P) have the same statement, but I do not have a POH handy.

Therefore on this basis you cannot use more than 10 deg of flaps under any circumstances. As for short field takeoffs in Cessna's I tell my students to follow the POH which clearly states " On a short field takeoff 10 deg wing flaps should be used " The whole debate about flaps for short field with no obstacles vs no flaps for short fields with obstacles, advantages of shorter ground run etc etc is entirely pointless IMO. Cessna gives you only one configuration (flaps at 10 deg) for the short field takeoff, all the performance charts are based on it and it is IMO silly not to follow it. The bottom line though; is if use of flap or not, is going to make a difference than you should not be making the takeoff in the first place. Remember all the POH figures were derived from a new perfectly rigged airplane flown by a Cessna test pilot The chance that your average PPL in a 35 yr old 10,000 hr airframe will be able to duplicate them is zero. I tell all my students to increase the book distances by 50 % when deciding if field lengh is sufficent.

For regular takeoffs I teach no flap on all the simple aircraft purely on the KISS principle. Small amounts of flap simply do not seem to make much difference so why bother ?

As for landing I think in general the amount of flap is somewhat of a red herring. The real issue is the ability to accurately fly an ideal final approach flight path while maintaining the correct airspeed. Untill the pilot is able to consistantly do this the amount of flap used will not have a substantial effect on the sucess of the landing, especially for short fields.

[RTN11]

I operate from an 800m grass strip, and often PA-28s and C172s land with either 2 stages, or no flap and takeoff with no flap selected. They then end up using almost all the 800m, leaving very little reserve in the event of problems.

I always take off with 2 stages and land with 3 (PA-28), and have never had problems with the reduced climb performance, even at MTOW. I never tend to use more than 5-600m for either takeoff or landing. I do not think this would be possible flapless.

[Big Pistons Forever]

I operate from an 800m grass strip, and often PA-28s and C172s land with either 2 stages, or no flap and takeoff with no flap selected. They then end up using almost all the 800m, leaving very little reserve in the event of problems.

I always take off with 2 stages and land with 3 (PA-28), and have never had problems with the reduced climb performance, even at MTOW. I never tend to use more than 5-600m for either takeoff or landing. I do not think this would be possible flapless.

I would suggest that if the pilots are using the whole strip for landing than the problem is not the amount of flap selected but the fact that they are almost certainly landing with excessive airspeed.

With respect to takeoff, both Cessna and Piper say to use 10 deg (Cessna)
or first notch (Piper) for short field takeoffs (which IMO is appropriate for a 800m grass strip). If pilots are taking off with no flaps, or more than the recommended amount, then they are not following the procedures specified in the POH, which IMO is always a poor practice.

[englishal]

or first notch (Piper)
Actually, most PA28's I've flown say to use 2 stages of flap for SF (25 deg).

[Big Pistons Forever]

Englishal

I believe you are correct, however I did not have any Piper PA 28 POH's handy to check when I wrote the above post. Just goes to show how important it is to read and follow the POH, for the specific make and model you are flying rather than using a one size fits all procedure, or going from memory...like I just did :ouch:

[Yankee]

englishal asked WHY was there no mention of a stage of flap for S/F? for the AA5 The aeroplane could handle a much shorter strip with flap, so it seems daft not to use them??

For the answer to that may I steer you towards what the Grumman Owners Club’s Safety Director once had to say on this RE: Why "no flaps" for takeoff? (http://grumman.net/archive/2006/msg00960.html)
Basically what I believe he is saying is if you use the correct S/F procedure for the Grumman and rotate to the optimum AOA , which in a Grumman is unnaturally high, zero flaps will give you the shortest take off roll.

The flaps on Take Off debate within the Grumman Community is long running and if you want to spend a couple of evenings going though all 775 matches on the subject go to the Grumman Gang archives site Grumman-Gang Mail Archive (http://www.grumman.net/archive) and enter a search for “flaps on take off”

[BackPacker]

Another reason to use flaps as per the POH is that aircraft with a low keel (R2160, Cirrus, Diamond, amongst others) have a big chance of a tailstrike when you land or take-off without flaps, due to the higher pitch angles needed for the same speed and lift.

[IO540]

I always use flaps as per the handbook (TB20).

For a takeoff, it makes very little difference but as Pilot DAR says, the lower lift-off speed reduces landing gear wear and any nose gear shimmy.

For a landing it is a lot better to fly at the lowest possible speed, for simple reasons of rolling distance, although on a 3000m runway that doesn't matter very much either :)

[Chuck Ellsworth]

What is a " stage " of flap you people speak of?

Is it something like " finals " ? :confused:

[Pilot DAR]

Hmmm

"Flap deflections greater than 10 degrees are not approved for takeoff".

So, no authority has gone to the effort, or undertaken to assume the potential liability, of "approving" such technique. That does not mean that it cannot be safely done. Is it "approved" land on a gravel runway? Few flight manuals mention, or "approve" it, but it's done all the time, and you'd probably think nothing of doing it yourself.

The interpretaton given to me (when I asked Transport Canada some time ago) is that a technique, action, etc. which is "not approved" is just that; not approved. No one has stepped up to put that through the approval process for any number of reasons. One may be that there is no demand or customer desire to approve it in the first place.

On the other hand, the certification basis for the aircraft, or the manufacturer, may choose to prohibit certain actions. That is pretty clear. Without special dispensation, doing that prohibited thing is a contravention of the air regulations, and no doubt is to exist. Spinning comes to mind as an excellent example of that. Spinning in a aircraft which is "spinning prohibited", without the appropriate special authority is in contradiction of the regs. Will the plane do it? Sure. It is a design requirement for all CAR 3/FAR 23 aircraft. Should it be casually attempted, certainly not, so "prohibited" describes it. The aircraft can be safely spun, but the certification basis requires either a very comprehensive demonstration of spin compliance, or more simply a prohibition, to save the manufacturer all that trouble, when no one wants that capability anyway. Let me assure you that the aircraft has been repeatedly spun, and repeatedly taken off, or at least "gone around" with full flaps. Doesn't make it a good idea, but if it cannot be safely done, the aircraft does not get approved. There is no customer demand for "approved" technique for large flap setting takeoffs, and similarly no need for performance data. I can assure readers though, that the sudden and momentary application of full flaps during a water takeoff in a Cessna 180/185, is a reasonably common event, in challenging conditions.

Therefore, I respectfully do not agree that:

Therefore on this basis you cannot use more than 10 deg of flaps under any circumstances

I do agree that it is not a technique which should be a part of initial training, or casually attempted by in experienced pilots. Along the lines of aerobatics etc, which are also discussed here. But to say that there are no circumstances when it can be done, is a bit extreme.

So to support my point, the video, which I made, to reassure those who worry about such things:

Aircraft :: C150 40 Flap Takeoff video by PilotDAR - Photobucket (http://s381.photobucket.com/albums/oo252/PilotDAR/Aircraft/?action=view&current=C15040FlapTakeoff.flv)

In defense of all of those people who own and rent out aircraft, it would be very discourteous to do this in an aircraft you do not own, as the owner would be intitled to be offended. I own the subject aircraft.

The only actual "prohibition" of full flap takeoffs of which I have been told, is the DHC-2 Beaver, where, I am told, 60 degree flap settings are prohibited for all flight operations. This aircraft type is not my area of expertise, so I'm subject to correction on this point.

Sure, follow the flight manual, and you're doing the most right thing. Interpret it in the way you think is most safe, and you'll be great. Recognize though, that there are sometimes other techniques too, which often yield the results desired under certain circumstances. If I were training someone to use my Cessna 150, I would be training them to use 10 to 15 flap for taxi and takeoff, and full flap for landing at all times - simply because for 23 years, it has worked to produce exactly the performance I need from the aircraft. I find it works well on the other Cessnas I fly too, so I treat them with the same care I do my own!

[Katamarino]

I've never had problems with pitch authority taxiing Cessnas with zero flaps. I have nearly always had improved pitch authority taxiing with 10 to 15 flap, and that has certainly prevented damage while operating nosewheel Cessnas on rough ground.

How does your flap setting affect the taxiing pitch authority, which I presume is only really a function of the elevator deflection and the speed?

[Big Pistons Forever]

Pilot DAR

I do not want to get into a pissing match here but I think you are splitting hairs with respect to the difference between "not authorized" and "prohibited".
Low time inexperienced pilots (which I believe are the majority reading this forum) IMO should not do procedures which are "not authorized" or on which no data or recommendations are provided for in the POH.

As a Designated Airwothiness Representative I would suggest you are in a unique position to make an informed desicion on where it could be desirable to depart from POH recommended procedures and do not represent 99.9 % of the average PPL population.

As a Canadian class 1 instructor I personally do not tell my students to always make full flap landings in light Cessna's. It is unnecesary to achieve reasonable landing distances and C 150/152/172/182 are easier to land with less flap as it easier to flare to the proper nose high attitude with less flap. As for takeoffs I also feel that no flap for normal takeoffs (which is the POH direction for the C 150, for example) and flap as directed in the POH for short field takeoffs represents practical advice for the majority of PPL's.

[Pilot DAR]

How does your flap setting affect the taxiing pitch authority, which I presume is only really a function of the elevator deflection and the speed?

Without claiming an understanding of the aerodynamics at play, the +-15 flap setting on single Cessnas seems to produce a downwash over the tail, which increases it's effectivness a bit. This slight additional pitch control, with some power, is often enough to get the nose wheel off with very little airspeed, and hold it off. I agree this is a capability with little common benefit, but in situations where there is the potential for nosewheel (sudden shimmy) or propeller damage, it can make the difference.

I strongly feel that new pilots should not be exploring techinquies which are presented as prohibited or could be interpreted as not approved or to be avoided. These pilots, however, should be at least familiar with some uncommon, but conforming operations, where these can be safely and consistantly demonstrated, particularly when they ask. It is up to the instructor first hand, and the flying community in general, to mentor new pilots with experienced based wisdom. Some of this wisdom should include optimizing the performance of the aircraft in certain situations, and pointing out to the new pilot that techinques which fall within the scope of approved etc in a flight manual, should also fall within their skill set.

Every takeoff and landing which I do, which has no other factors determining which techinque would be most appropriate, will be either short or soft technique. "Regular" takeoffs and landings seem to me to require the least precision. To me, it is simply a lost opportunity, to takeoff or land, without practicing a technique appropriate for the aircraft and conditions.

I see aircraft taxiing around with control positions indicating that the pilot is apparently unaware that they are controlling an aircraft which is moving throught the air. The fact that it is on the ground is probably what is creating this relaxed attitude, but it is still moving through the air! Why not practice flying it before you have to leave the ground, and imediately when you return? The plane is flying, why is the pilot not? Pilot lands plane, three wheels contact the ground, and pilot promply lets go, and gives up flying. Does the pilot not realize how much braking effort can be saved by holding the crontrols back through the roll out?

I see aircraft hurtling down the runway with no takeoff flap set, and no nose up control held. That aircraft will be going 10 or so? MPH faster when it leaves the ground. Additional maintenance cost ( risk of shimmy and all those other undesirable landing gear things), yet that pilot will whine about the cost of flying. If all the pilots were paying dierectly for the specific wear and tear they cause to the aircraft they fly, they'd care more. Some instructors fall within this accusation - but no slight intended to anyone in particular.

As has been mentioned earlier, the flight manual for the aircraft, is based on the manuafacturer's testing with a new condtion aircraft. It was not an aircraft which was "experienced" and maybe a little loose, thus needing a more gentle touch. When a system on the aircraft (flaps, for example) is available, to reduce wear and tear on the landing gear, it should be safely and compliantly used, not ignored. New pilots should know this.

[RTN11]

PilotDAR

Just out of interest, what rate of climb did you get after that 40 flap takeoff?

[Intercepted]

I see aircraft hurtling down the runway with no takeoff flap set, and no nose up control held. That aircraft will be going 10 or so? MPH faster when it leaves the ground. Additional maintenance cost ( risk of shimmy and all those other undesirable landing gear things), yet that pilot will whine about the cost of flying.

Thats why I have started to use two stages of flaps rather than one at White Waltham.
Two stages and I'm able to avoid that bumb in the middle of the runway when I'm at high speed.

[Pilot DAR]

Just out of interest, what rate of climb did you get after that 40 flap takeoff?

Though the objective was not the demonstration of a particular rate of climb, my qualitative answer would be about two thirds of what I would normally expect to see, in terms of altitude over the far end of the runway. More to the point, the climb was always positive and steady (no settling afterward).

[Big Pistons Forever]

Re full flap takeoff and the C150.

When I did my PPL near Montreal we were practicing PFL's in the C150 one very hot muggy summer day with myself, my 180 lb instructor, and nearly full tanks. The last when went pretty well and at 300 ft AGL with 40 deg flaps out I was told to go around. Full power and flaps up......only the flaps did not move. At full power the aircraft would just maintain level flight and would not climb. We flew the 10 miles back at 300 ft and landed. This was 33 yrs ago but it is still a rather vivid memory and after that I am carefull with large flap settings and low powered Cessna's.....

As a young Instructor/charter pilot I once used 40 deg of flap in a C 172 to get it to lift off from a very muddy field. The aircraft would not accelerate above 45 kts so a sudden application of 40 deg flap caused the aircraft to balloon up enough to break free and then some carefull stick jockeying kept it in the air as I slowly accelerated to a sensible speed. When I returned the CFI/Chief Pilot asked why the aircraft was covered in mud. When I explained he said "Good Flying, Now WTF were you doing going into the field in that first place"

That being said the use of large amounts of flap on takeoff is common with float plane takeoffs. The C180/185 manual flap systemis is particualy usefull as you can finesse that little bit extra bit of flap between the 20 and 30 deg notches to help the aircraft break free of the water when it is heavily loaded and/or the wind is calm

[daladaladriver]

There's a couple different schools of thought to flaps on takeoff when flying soft/short field. If the 206 I was going to fly had 5 pax and bags in the back... the tail sits maybe 7 inches off the ground... so no need to pull all the way back on that control wheel to keep the nose light and protected on the rough runway. Normally I would have flap 10 set before the roll.... flaps 20 would come in handy when you had a impala or goat or whatever jump out on the runway last second... no time left to stop but enough speed to get into ground effect...drop the 20 and up you. Never would I start the takeoff roll with 20... that's just too much unnecessary drag on the roll... better to drop to 20 last second if you are about to balloon up to safety. Some pilot will opt to start the takeoff roll with 0 flap to get up to speed asap then drop to 10 or 20 for an early up well...

In the caravan, flaps 20 is standard for takeoff... dropping to 30 (full flap) last second helps to get up early too... just don't try and escape ground effect too soon! Starting a roll with full flaps 30 is approved if you have the APE stall kit... comes in handy if the nose wheel's going to take a beating on the runway since full flap will get that nose up into a wheelie right away with the control wheel full back. Then just wheelie it out until the plane is ready to get airborne. Just need to make sure your nose wheel is barely off the ground... otherwise the flaps are introducing way too much drag and killing your effort to make a short takeoff roll.

Of course a flap motor failure / asymmetric flaps could always happen so be ready for the consequences. Playing with flaps on takeoff in the bush certainly has its merits. However, using flaps 30 for takeoff is not a good idea in a short caravan... in an engine failure you'll lose the effectiveness of your elevator, and depending on CofG, unable to pitch down for a stall recovery. Also it's not approved.

I am curious though, how do you float guys typically use your flaps for takeoff? Looking for some insight from the float world!

[Piper.Classique]

What is a " stage " of flap you people speak of?

Is it something like " finals " ?

I think that would be a notch with mechanical flaps......
Like the DR400 which has first notch 15 degrees second 60 degrees
As in pull the handle a bit and let go that's takeoff. Pull more and let go that's landing flap.
Or just forget it as they don't actually have much effect anyway. (on a wooden Robin, anyway......) flying off 720 metres of mud, still......got really wet again washing it off yesterday. I suspect the runway will soon all be just in front of the hangar, next to the taps.
Folk do seem to get all het up here, don't they?

[Desert185]

Good, experienced, real-world info from BPF on the use of flaps not outlined in the POH.

For the OP, I always use F10 for takeoff when flying the 172 with old 145 horse or newer 150 HP engine. Generally speaking, max lift/min drag combo with flaps occurs when flaps are set to the same angle as an aileron in max down deflection, which is pretty close to F10. This results in less runway used and prolongs tire life to a degree (and is much more comfortable with a rental aircraft that has an out of balance tire(s) with the attendant vibration after liftoff). Raise the nose a bit at the recommended speed and let it fly off when its ready. You can then milk the flaps up slowly after liftoff to improve climb performance when you have good speed. If heavy and with a turn required right after takeoff, F10 will also provide a bit more stall margin while in a bank. It will also feel better if the CG is close to the aft portion of the envelope when you have make that slow turn.

Wish my son's 170B with O-300 had a F10 position. We use the F20 notch at sea level and milk them up after liftoff. At higher DA's on a hot day, that (F20 initially) doesn't necessarily work. One has to adapt...but then, that's flying.

The 185 specifies Flaps 0-20 for takeoff. I use F20 and raise them to F10 right after liftoff for an increased climb rate, then up when clear of any obstacles. The 300 HP allows the drag of more flaps and the tail comes up a bit quicker (by itself), which reduces drag and takeoff distance. A buddy uses F10 on his 185, but I think his wing washout is set differently than mine...but that's another topic. He also doesn't have WingX STOL, which might be part of the reason, although I used F20 before installing the kit.

Hope this background info helps with your decision.