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Your stall speeds, versus flap settings?

Maule MX-7-180 has > 9 ft long flaps, more than twice as long as the ailerons and they are adjustable from -7 (up) to +48 degrees (down).

Hence, perhaps, the largest percentage difference quoted so far? Stall flap up is allegedly 53 KIAS, flap down is 41. Apart from the ASI markings there are no other performance data in the manual. I treat the Maule flap handle as a primary flight control. All told, the machine is a bit of an “acquired taste”… If I make it to Carcassonne, y’all can have a go.

Last Edited by Jacko at 02 Feb 18:48
Glenswinton, SW Scotland, United Kingdom

jollyrog wrote:

My Cub doesn’t have any flaps or a Pilot’s Operating Handbook.

The Auster has split flaps, but no POH.

Placarded stall speed flaps down is 29mph. (True airspeed at 2000 feet is more like 35 mph according to some rough flying-in-a-triangle in the stall buffet while recording GPS ground speed and averaging the result).

Flaps up stall speed is about 4 mph faster.

Last Edited by alioth at 02 Feb 16:40
Andreas IOM

Peter wrote:

Exactly, but for a max perf (shortest landing roll) landing you need full flaps, no?

Well, it depends. If, like in the C172b, the full flaps don’t give you a possible slower stall speed, it might be okay to use just partial flaps and a quick retraction for more braking action. Many STOL taildragger pilots use a similar technique to get weight on the braking wheels: They touch down in a full stall and then lift the tail, reducing AOA and hence the lift. But these are minor deteriorations from the normal procedure. In the majority of aircraft, my guess would be that the full flap approach would result in the shortest landing roll.

Another topic would be landing distance, because here the full flaps would enable a steeper approach due to more drag and subsequent higher controllable (stable) sink rates. So for a steep approach full flaps are needed, unless you fly an oddity where a slip with partial flaps results in a higher sink rate than a full flapped normal approach and the full flap slip would be prohibited. But that’s a quite rare case, I would think.

USFlyer wrote:

Slippery carbon fiber planes need the flaps to slow down

FWIW: Not only carbon fibre planes. Have a try in a 1955 wooden Ka6 or in our DR250 and experience what a slippery aircraft is :-)

It is not tied to the construction material.

Last Edited by mh at 01 Feb 21:53
mh
Aufwind GmbH
EKPB, Germany

You can land almost all aircraft without the flaps, but I guess that wasn’t what you aimed for

Exactly, but for a max perf (shortest landing roll) landing you need full flaps, no?

Full flap is also necessary on any high perf SEP or SET to achieve the 60kt max Vs i.e. to get certified.

Administrator
Shoreham EGKA, United Kingdom

USFlyer wrote:

It’s about drag.

No, it’s not. It is about maximizing C_L that changes stall speed. Drag is important to dissipate energy, either for a steep approach or to slow down. This is, for example, why extending the gear has no impact on the stall speed of the ASH25Mi. There, you can see, that adding drag (=air brakes) actually increases the stall speed, although that is due to the location of the spoilers.

If you look for instance on at the table of the F150M above, you will notice that the most difference in stall speed is between 0 and 20° flaps, and that further extension brings only one mph in slower stall speed. That means, that you just rise the drag coefficient and almost no lift coefficient.

Peter wrote:

Does any plane land with less than full flaps?

You can land almost all aircraft without the flaps, but I guess that wasn’t what you aimed for. Many people opt to land the early 172s and 150s only with 30° instead of 40°flaps, partly because if a tad nose heavy, even with full backpressure on the yoke, you essentially make a three pointer. It becomes easier to flare if you just use around 20-30° flaps and most people feel more comfortable with it. Plus, the C150 may only get reduced sink speeds with 40° flaps and full power, or just a very shallow climb. The go around then can be demanding.

mh
Aufwind GmbH
EKPB, Germany

USFlyer wrote:

Slippery carbon fiber planes need the flaps to slow down…the Cirrus SR22T for example lands with full flaps. And needs its big constant speed prop to help make drag to land.

The SR22 is not really that slippery. Sink rate with engine out is actually pretty poor, around 1:9, about the same as the Piper Saratoga (gear up, though), and a lot worse than a Columbia 400 at 1:12 or so. Not really like a jet

Also it is perfectly landable with no flaps although the nose-high attitude in that configuration is something to get used to… and landing with flaps inop should be part of any training as these things can fail.

Biggin Hill

mh wrote:

I have a video of a (power off) landing online. It is a tad on the fast side on landings, but still does well on 500m airfields. It is nicely controllable.

Thanks for that, great video The landing speed looks OK to me. Nice sliding vent windows too.

When landing at high altitude (let’s say 8000 ft density altitude) I find it useful to use half flaps, not full flaps, in preparation for a potential clean up and go around on short final.

It’s well documented that the stall speed reduction comes with the first increments of flap deflection, and from my own experience the amount of flap that works best for a particular airport and airframe also depends on the propeller installed. If the installed propeller provides a lot of drag, for instance a constant speed propeller installed on an airframe designed around the lesser approach configuration drag of a fixed pitch prop, there’s often no need to approach with substantial power when half flaps would provide the same glide slope with less power.

Peter wrote:

Does any plane land with less than full flaps?

Of course. The FD CTLS normal landing config in calm to small cross wind is 15 degree flaps…full flaps are 30. They are used for short and soft field landings. But then the CTLS is a very light plane, still slippery, but able to use far less runway than a big Cirrus SR22T.

Last Edited by USFlyer at 01 Feb 20:55

the Cirrus SR22T for example lands with full flaps.

Does any plane land with less than full flaps?

Slippery carbon fiber planes need the flaps to slow down

That’s really amazing.

Administrator
Shoreham EGKA, United Kingdom
28 Posts
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