Negative Flap Settings

[RobH]

I played around with flap settings yesterday on a cross country flight in our MT7-235.

With Autopilot on (I know I know real pilots don't use autopilots or fly tri-gears.... 8^)) and not changing power settings, changing between negative flap and 0 flap settings made pretty much no difference in either indicated airspeed or ground speed per GPS (real pilots probably don't use GPS either... 8^) -- I admit to liking electronic gadgets.)

Of course I had to change the trim to get level flight after changing flap settings, or at leasts to get the autopilot to stop blinking at me.

It was only me in the airplane and about half the main tanks full.

There was less difference (no difference really) than I expected. The only noticeable difference was really a change in pitch attitude. I like the attitude with the negative flaps better, but frankly that is how I've always flown it on long flights and therefore I think I'm just used to it.

I thought there might be a few knots difference or some other differences. Did I expect too much? Others have different experiences? Does it depend on W&B at any given time?

Thanks.

Rob

[Lowflybye]

Depends on the W&B and where you are in the CG envelope...

[Lowflybye]

The reason it depends on the W&B and CG was well explained by a64pilot in an old thread. I have copied it below on his behalf.

The Maule airfoil is a high lift airfoil. The long winged Maules have too much lift for efficient high power cruise, you have to stick the nose down so far to equalize lift and weight in cruise that you get a lot of drag from the nose being so far down. Reflexing the flaps allows for a more level flight attitude and the decrease in drag from the level attitude is more than the increase in drag from reflexed flaps, usually
Reflexing flaps "spoil" lift of course
High altitudes mean less air density and lower horsepower, eventually you lose enough horsepower and lift so that the reflexed flaps become a hinderence, the nose down attitude with 0 flaps isn't there because of lower indicated airspeed. For me that's about 11,000 ft. which is also the top of my "sweet" spot and interestingly enough is the altitude that gives me my highest true airspeed with the lowest fuel consumption. It's around where I would cruise if the winds were always 0 and the trip length made sense to climb.
My best fuel consumption comes at high altitude and 0 flaps.

[UtahMaule]

I'm not at all scientific about it, but it seems like it doesn't help at all when I'm real heavy. But, when I am some what light I seem to gain 5-10 mph.

[andy]

I've noticed about 2 mph ground speed improvement for the same altitude/power combination with the negative flap setting around 2500 MSL. This was at typical weight - around 1900 lbs.

[N5ue]

I consistantly see about 3 knots difference in my ground speed when I fly the MXT-7 180A with the flaps reflexed. I also notice the airplane is not as stable as when I fly with the flaps 0. The next time you fly, look at the angle of attack during level flight with the flaps in both positions, you will be able to see the difference.

SB

[BatMaule]

I usually cruise with the flaps in the negative position on my M6. Best I can tell, I get about 2-3mph under most conditions. It isn't a whole lot but it is FREE!

Paul

[a64pilot]

It'a a gross weight / density altitude / engine horsepower / power setting / tire size, etc. thing.
In other words, it's not always going to be faster with the flaps reflexed, sometimes it's better to have 0 flaps. Only way to know, is to try.

[Mountain Doctor]

I use the -7 degreee position, but if it adds any speed or not I've not noticed.

[Vince Massimini]

The -7 degree setting does little at low altitude, but it is a definite 2-3 knot improvement at 9-12,000 ft in cruise (M7-235C). Worth doing for a longer fligth, but I don't bother with it for a short flight.

Try taking your bird up to 10,000 ft and setting a full throttle cruise with leaning. Let everything stabilize and then do the -7 trick. You will gain a few knots unless you are very light on fuel/passengers.

Best,

Vince Massimini