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
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!