Interesting article in the last-1 US AOPA mag.
The Lancair 360 has a reflex flap option, apparently. Somebody found that 7 degrees UP (minus 7 degrees) delivers a 10% improvement in best-glide.
I don’t know of any certified aircraft which has a reflex flap mode.
Many years ago, one Socata mechanic told me that setting up the ailerons so when they are neutral, they are both up slightly (about 1cm) makes the aircraft go quite a bit faster. This is not surprising, but it would be at the expense of a higher Vs.
Maules have a negative flap setting for cruise
Gliders have negative flaps for glide (speed flaps) and positive flaps for thermalling (lift flaps) and airbraks for landings
AFAIK, only Maules have them in SEP
Pipistrel Virus has a negative flap setting for cruise.
Cttime wrote:
Pipistrel Virus has a negative flap setting for cruise.
Didn’t know until now that the Virus in fact is a certified aircraft. I know of some microlight aircraft which have negative flaps for cruise, the Nando Groppo G70 to give an example. And then there are touring motorgliders like the Stemme S10. But it is totally common in gliders used for competition to put the flaps in negative for cruise.
Thing is, that misuse of negative flap settings can end in a fatal way quite rapidly. Therefore, I assume that this is the reason why you don’t find such flaps in typical GA aircraft. Spin recovery is more difficult. Stall speed is way higher.
The reflex/negative flap setting was introduced on certified aircraft back in 1981 with the long wing Maule M6 . I believe the only prior employment had been on Molt Taylor’s Mini Imp, which is an uncertified ‘home build’ and as ‘Ibra’ mentioned, on sailplanes. Forum members who hail from that era might have a fuller knowledge.
The shorter wing Maule M4 and M5 have conventional 0, 20 and 40 settings.The Maule M6 and majority of M7s have -7, 0, 24, 40, 48, degrees.
B.D Maule used a negative flap setting to counter increase drag from his new long wing design and improve cruise speeds.
In -7 the AOA and drag are reduced with an increase of 5-7 knots. The subsequent ‘nose drop’ also affords a superior forward view, making it easier to spot and navigate to the right of slower Mooneys, TB20s and small Biz jets 
The reduced lift of -7 is also handy when landing in gusty crosswinds.
onfinal wrote:
The reduced lift of -7 is also handy when landing in gusty crosswinds.
I guess you need a hell of a runway to land with negative flaps, a very long one, in M7 terms about 300m 
UdoR wrote:
Thing is, that misuse of negative flap settings can end in a fatal way quite rapidly. Therefore, I assume that this is the reason why you don’t find such flaps in typical GA aircraft. Spin recovery is more difficult. Stall speed is way higher.
I don’t see why a minimum flap setting which is negative would be more dangerous that a zero flap setting?
Many SEP aircraft already have quite high stall speed with zero flaps, e.g. 70 KCAS for the TB20.
UdoR wrote:
Spin recovery is more difficult. Stall speed is way higher
I had the impression more drag is what makes sping recovery harder? it’s the high drag regimes (high power, full flaps, fell assymetric, high angle of attack), all you have to do to exit spins (by definition the most draggy config) is to “clean the aircraft” on: yaw, power, flaps and angle of attack
Positive flaps tend to reduce elevator authority and kill rudder effectivness
On stall speed, yes it will increase with negative flaps
