You know, Bosco, there is a saying: ‘Rules are for the obeisance of fools and the guidance of wise men’
I’d say that goes – up to a point – also for POHs. However, as NCYankee states, at least in FAA-land the ‘limitations’ part is binding.
WRT the flap up or down discussion – I have made my POV clear in the other thread that I can’t see a reason to introduce another point of failure in a critical stage of flight. Have to say, in a very general manner I use flaps ‘as required’, whatever that is for the task at hand. I only have a few hours in a T-tail Turbo Arrow, but this is indeed a completely different beast from any other PA28 variant I have ever flown. Don’t think you can extrapolate from this type to others, even if Mr. Piper saw fit to call all of them PA28.
I think that there is a lot of flying outside the POH. However, the pilot has to have a good thorough think about what they are trying to accomplish and approach it in small conservative steps.
I have done a fair bit of mountain lake flying in a 85 hp Champ on floats which is always under powered. Then you add the in varied wind and water conditions! You are always ‘coaxing’ it into the air. Given that it was manufactured in 1946, there is barely any information in the manual. You are basically on your own. This means that if you want to know how it is going to perform in a given situation you have to do some work ahead of time, using cautious test flying and a notepad to record the results.
After you start logging the density altitude, water condition, wind condition, and take-off weight you can make you own take off charts… There was many a time when I wanted to visit a certain (short) lake, but am not sure it is going to work with the anticipated load. What to do? Find a longer lake at the same or higher altitude and go lightly loaded with a number of empty 20L water bottles. After a few runs, you will see if it is going to work. If not then you can dump the water and go home. Best to find this out before you make a one way trip!
Of course, there is a lot of technique to float flying and this is written in books, taught at courses, and learned by experience. But is not in the POH! For example, under certain circumstances that particular plane did not have enough power to overcome the drag of the floats during the take off run. Thus, the normal technique was to roll in aileron at the correct time to lift a float, reduce the drag, and accelerate to flying speed. This was a very illuminating lesson because the result is binary:
1) If you put the aileron in at, say 38mph, there would not be enough lift to remove the one float from the water. There would be too much additional drag from the aileron, and you could not accelerate further. Thus, no take off was possible.
2) If you put the aileron in at, say 42mph, then the float would lift clear of the water, drag from the float would be reduced, the aircraft would accelerate to, say 52mph, and take off.
3) If you did not put the aileron in and kept the controls neutral, you would stagnate at, say 46mph, and would not be able to take off.
Shock and awe, you could also drop flaps in at the correct speed (if you have them)! Not to poke at others on the forum, but ‘best not loose control’ :-)
Other techniques include the left veering take off with a minimum of right rudder (to minimize drag)… aligned at the correct angle to be into the wind at the anticipated take off position.
Or how do you answer the question… How sharp is too sharp of a curving or circling take off? Very, very, carefully!
These things are all a bit moot in a normal training aircraft on a paved runway (take off happens pretty quick regardless), but the physics are the same.
Of course, there are some pretty strong arguments for not messing with the ‘hard’ rules of the POH. The one that comes to mind is TWA 841. In that case the pilots were messing with the flap positions by pulling a CB to stop the flaps while they were operating. They believed that they had found an ‘optimum’ position where the aircraft was faster in cruise. After the accident, testing showed that this was not true…
So, it seems that we have been carried away a bit with that “you have to fly according to the POH because it’s the POH”, at least as far as procedures are concerned.
No, I think you’ve raised an important point. The EASA Basic Regulation says in Annex IV (Essential Requirements for OPS):
1.b. A flight must be performed in such a way that the operating procedures specified in the Flight Manual or, where required the Operations Manual, for the preparation and execution of the flight are followed.
Presumably that is undesirable for GA and we would like to change that.
Can you offer specific and documented examples of procedures in the Aircraft Flight Manual that are bad/wrong/dangerous please?
The most important one is the implied prohibition to fly the aircraft in any way not fully documented in the manual
Other, less safety relevant items:
The argument that I would make is that manuals (POHs and maintenance manuals alike) for large aircraft are written with the expectation to be complied with in detail, with lots of scrutiny, checks, negotiations etc.. They are also updated continuously. In addition, approved operations and maintenance manuals make it possible to adjust these if there is anything unsuitable.
POHs and maintenance materials etc. for light GA are written primarily with the FAA Part 91 regime in mind, where these mechanisms do not exist, so giving the kind of 30 year old typewritten pamphlet on yellowing paper the same “force of law” as A320 manufacturer’s SOPs is inappropriate.
Cobalt wrote:
The interpretation that a max demo crosswind component is a limit because there is nothing explicit in the POH for anything higher.
Where do you read this? All POHs that I’ve ever seen have some wording to the effect of ‘this is not considered a limitation’, it’s simply the max crosswind the test pilot(s) could find during certification.
Did not prevent regulators (Sweden often quoted) to beg to differ and make it a mandatory item.
Also, not all POHs are explicit in that this is not a limitation. I just had a look at the POHs that I have lying around.Piper PA23R-301T (Turbo Saratoga), DA42 (classic and NG), DA40 all don’t say it is not a limitation. Should not matter as it is in the name, but still.
C303T, SR22, and Columbia400 make it clear it is NOT a limitation.
POHs would be written differently if they were expected to be followed do the letter.
Cobalt wrote:
Did not prevent regulators (Sweden often quoted) to beg to differ and make it a mandatory item.
Yes, Swedish regulations are explicit in that a max. demonstrated crosswind figure in the POH is a limitation. I guess we will get rid of that rule when part-NCO comes into force.
I guess we will get rid of that rule when part-NCO comes into force.
But then you have to set up your own rule instead, just like commercial operators do already now. And I have yet to see a company operating manual that extends the limitations/recommendations of the manufacturer instead of further restricting them. So from my experience in commercial operations I expect manufacturer recommendations to become limitations with part NCC.
But then you have to set up your own rule instead, just like commercial operators do already now.
Why do you imply that everbody must have a rule on everything? 
boscomantico wrote:
Why do you imply that everbody must have a rule on everything?
Not everybody. But everybody who wants to operate under EASA part NCC from next year on. An operating manual (= set of rules) and a quality system are required.
