The POH for my TR182 is totally unambiguous – it says “flaps 0 – 20 °”. Unambiguous but not very precise. It does specify 20° for short field.
When I bought it one of the instructors I knew said “flaps are free, tires cost money”. So I always use 10° for take off, which gets me off the ground a few knots earlier.
DA42 with CD-135 engines POH specifies 0° flaps for takeoff while for DA42 with CD-155 engines it specifies first notch (APP) for short field takeoff and 0° for normal takeoff. AFAIR it’s the same for NG, -IV and DA62.
TB20 mandates first notch of flaps for all takeoffs.
TB20 mandates first notch of flaps for all takeoffs.
Statements loke that are just not right. This is not mandated. Anything strictly mandated will be in the Limitations. Here, and in many other cases, it isn‘t. It‘s merely in the Procedures/Performance section, which is not a mandate, but just a suggestion by the manufacturer.
It it were a mandate, it wouldn‘t be legal to takeoff with flaps inop, for example, which would be OTT for a TB20.
The answer to both questions seems to be aircraft/runway/ pilot dependent
When I started to fly in a Robin 315 I was encouraged to pull the throttle back to full idle approaching the threshold on final.
In the Jodel D113 there were no flaps and I was encouraged to glide in from the end of downwind/beginning of base leg.
When I flew the Jodel 120 Paris-Nice with its airbrakes I was encouraged to keep power on until the roundout and then judge whether or not I needed the airbrakes for the particular runway length.
When I moved to flying heavier metal machines like the PA28 and the PA44 it was a matter of keeping some power on and reducing gradually during the round out.
Transiting to ULMs many need power to be kept on through the round out due to lack of inertia.
As I wrote before with the Robin it was "what are/were called in the book, take off flaps for take off. IIRC they are still called take off flaps in a DA40D .
For the light twins (I haven’t tried the Technam) it has always been taught as no flaps take off. Although having said that an examiner will want to know why you have decided on that configuration. And although the book also recommends, on many light twins, a one stage flap for take offs on a short field you need to do your own calculations and make your own decision whether you are going to take that advice and if you don’t will need to justify it to an examiner. On twins of course as well as taking into account the runway available and needed you need to figure what would be best in an EFATO. In other circumstances there could be condition of runway potholed, high grass, muddy, pebbly which will all play a roll in whether its a good idea to use flaps or not.
All the above depends on the pilot and most of us have been trained on let’s call them “standard training aircraft” and we will have been trained in a generic way we do such and such at a particular time. For instance on a Robin 315 I was taught one stage flaps and carburretor heat on, level at a stable indicated airspeed of IIRC 110 km per hour (other bigger engined Robins were 130kph.). The second stage of flaps were added on final. You touched nothing else until you’d landed. As touch and goes are only considered a training manouver in order to get more circuits completed in the hour often the instructor would push carb heat to cold and flaps to take off before saying go. Although as one gained more experience one was expected to do it for yourself.
As I gained more experience and with different aircraft I learnt to adapt what I did and when to the aircraft and the circumstances and that’s where I am today, ie still learning.
I think flaps are always at pilot discretion, I hate when people make them mandatory
The other thing, I saw people putting 2 stage of flaps in PA28 which is the correct performance takeoff setting but holding it to “rotate at 65kts” rather than just letting it “liftoff”
DA42 with CD-135 engines POH specifies 0° flaps for takeoff while for DA42 with CD-155 engines it specifies first notch (APP) for short field takeoff and 0° for normal takeoff
I guess it has to do with max available power?
johnh wrote:
When I bought it one of the instructors I knew said “flaps are free, tires cost money”.
I like that one and would argue that by introducing drag flaps reduce the rate of climb and thus cost fuel and engine wear.
Statements loke that are just not right. This is not mandated. Anything strictly mandated will be in the Limitations. Here, and in many other cases, it isn‘t. It‘s merely in the Procedures/Performance section, which is not a mandate, but just a suggestion by the manufacturer.
It it were a mandate, it wouldn‘t be legal to takeoff with flaps inop, for example, which would be OTT for a TB20.
I would agree with the practicality of it, and similarly landing with no flaps is fine (lots of Americans, with long runways do it, which is also an easy way to land gear-up because it disables the gear warning 
) but an often-held legal position, drummed repeatedly on the US Socata group, is that the aircraft is certified with functioning flaps and thus departing with INOP flaps is illegal.
Departing or landing flapless, but with flaps functional, is 100% legal. Just as well, since this is widely done in training.
On the OP question, I don’t know the answer I think on most GA types it makes little difference. On the TB20 it does make some difference but probably only a few tens of metres on the takeoff roll. Still, if departing from a marginal runway, that could be 5-10% of the runway length.
Most aircraft have different setting for “normal” fields and short/soft fields. The old Pa-18 I fly has no flaps I guess the reason is that as “generic” flaps go, they increase lift a lot if a small amount is used while the drag is only marginally increased. Full flaps increases lift more, but drag is increased relatively much more. Then there are engine power, weight, stall speed and other thing that will determine what is optimal.
In a training setting, taking off with “one notch” is never wrong. You learn to deal with flaps also on take off. This may not be necessary on long runways, but if you have never done it, you are not likely to do it on short field either. It’s easier to “define” a short field as long enough than to start for the first time using flaps at take off.
I think the Alphatrainer is cool. Normal procedure is one notch. On soft/short fields it is two notches, meaning full flaps on take off. Landing is always with full flaps. Yesterday I tried landing with zero flaps, just to try it. The POH warn against it because a tail strike is likely. But I had to try it If I had flared all the way to stall, the tail would for sure strike long before that happened, so I didn’t do that, I just let it descend with a slight nose up. The flaps on the Alpatrainer is anything but effective as far as increased drag goes, but it does lower he nose considerably.
Which is another reason. Preventing tail strike.
At risk of stating the obvious, flaps differ. Fowler flaps will increase lift and improve low speed handling. Split flaps and plain flaps tend to cause more drag in return for their lift. Useful on landing, but less so on take-off.
I think the Alphatrainer is cool. Normal procedure is one notch. On soft/short fields it is two notches, meaning full flaps on take off. Landing is always with full flaps.
Maybe zero flaps is negative setting to be used in cruise only? I also recall max RoC was obtained with one notch of falps, can you confirm?
