In a true soft field the nose wheel will dig in and eventually stop the aircraft or cause a nose wheel collapse. Conversely with flaps in take off lift dependant drag is not a major factor until around 30 KIAS at which point the elevator/stabilator is easing forward to neutral – the aircraft only needs around a few degrees of pitch with take off flaps as zero lift alpha is in fact negative. The aircraft should then lift off, now in ground effect, where zero lift alpha is even more negative. Further pitch to below level, with a Hershey bar wing and flaps 25 you are in fact around positive 3 degrees alpha in slightly nose low ground effect attitude accelerating.
A soft field take off in a nose wheel in soft field conditions (Cessna 182 with an air glas fork and 8.00 nose wheel possible exception) without full back yoke to get rolling is a contradiction in terms.
Yes shortest takeoff ground roll is done neutral or negative AoA, flaps up on hard tarmac, anything else increases the ground roll
On soft it gets complicated but you will have a long ground roll no brainer,
- If you put forward elevator clean flaps, the aircraft does not generate lift, with all weight it sinks in the soft and get stuck and dragged in ground friction, so long ground roll
- If you put back elevator dirty flaps, the aircraft has less ground friction but get dragged at higher angle of attack with aerodynamic drag from flaps, so long ground roll
If it is short & soft with high rejection risk one can fiddle with full flaps, ideally full drag flaps with wheels in the ground between 1/4-1/2 runway and above 1/2 lift of speed, then if you decide to takeoff raise them in ground effect otherwise reject and keep them dirty to stop, but unless they are mechanical you will stay behind it but you are cutting few items short there…
If aircraft can’t takeoff and float safely on drag flaps with stick forward (not necessarily climb), sell it and buy a new one with a better engine and slow speed handling, you don’t want a go-around with wheels on ground with that one 
If you fly tailwheel there is no nose wheel to protect in soft field, just sayin
I believe that the SR-20 uses 15-6.00-6 size main wheel tires, which are a smaller diameter than a regular 6.00-6, and usually inflated to a higher pressure. These smaller wheels are noticeably less good/more draggy on grass or soft ground. The 182RG I fly has them – at 68PSI, and I allow for that when considering where I’ll land it. 15-6.00-6 tires on heavier planes are really intended for hard surfaced runways, they’re kind of the opposite of tundra tires. An SR-20 wing is designed for speed, rather than lift at low speed, so the beneficial soft field technique is probably even less effective than on other types.
Ibra wrote:
If it is short & soft with high rejection risk one can fiddle with full flaps, ideally full drag flaps with wheels in the ground between 1/4-1/2 runway and above 1/2 lift of speed, then if you decide to takeoff raise them in ground effect otherwise reject and keep them dirty to stop,
Is fiddling with flap settings during the takeoff roll, or greater than “takeoff” flap settings for takeoff described anywhere in the flight manual, or training material for the SR-20, or any other certified type?
Ibra wrote:
Yes shortest takeoff ground roll is done neutral or negative AoA, flaps up on hard tarmac, anything else increases the ground roll
I don’t agree about the flaps. Why do transport category aircraft always use flaps for takeoff unless it was for reduction of the ground roll?
On tarmac, shortest ground roll to reach a given Vr must always be with a clean aircraft.
The problem is that it is judged unsafe to be engaging some level of flap around Vr when you need to be looking outside. Also assymetric flap deployment at that point would be really dangerous.
So the POH states that takeoff flap is to be applied before departure (and visual inspection is possible then, in GA).
Flaps & trim are as required by the pilot most of the time in gliders and un-certified types
For certified types, yes I agree one should stick to POH technique (except when his flaps are U/S) but as disclaimer the POH technique only guaranteed to work with published runway POH length requirement then plus blanket 40% safety factor, one will be dead stupid picking the former but not the latter, either pick all of it or none !
Airborne_Again wrote:
I don’t agree about the flaps.
Neither do I.
Each certified type will specify the optimum flap setting for takeoff. In the case of one type I fly, flaps are either up, or down. They are to be selected down for all takeoffs and landings. On my taildragger amphibian, negative AoA certainly will not produce the shortest takeoff ground roll!
This is one of those situations where reading the flight manual, (thus following the approved manufacturer’s recommended technique), is far superior to taking seriously speculation and generalization posted by anonymous people on the internet.
Ibra wrote:
you should stick to POH technique (except when flaps are U/S)
If the flaps are U/S, would you be taking off!?!
Really, really… just fly the plane the way the flight manual says!
If you have to yes, why not? I did takeoff & land with electric flaps U/S and stuck in 1/2 position and flew 800nm at slow speed buring load of fuel, just pragmatic flying TBH
Peter wrote:
On tarmac, shortest ground roll to reach a given Vr must always be with a clean aircraft.
Certainly, but the Vr depends on flap setting.
