S1/S2 minium takeoff speed?

[couleeone]

Question of the day:

What is the minimum indicated indicated airspeed will the S1/S2 takeoff and climb at?

Throw your nickle in here and give me your thoughts...I know my answer but what's yours?

[reileyr]

pilot and full fuel 60 deg F with 30 deg flaps, less than20 indicated airspeed but the controls are extremely mushy and I think dangerous if the plane is flown out of ground effect.

[JohnM]

George,

What a fun question.

With a light S1/S2 with anything but the wood prop and 15 deg of flaps, I expect to fly when I see 20-25. It will "climb" in 30-40mph range. But until you see 40 or there abouts, there is not enough Delta P to result in a confident climb.

Of course, it's an entirely different equation with the CarbonCub because of the massive amounts of Delta P available.

John

[Pilawt]

Honestly I've never noticed. I'm usually looking outside to observe whether the direction the spinner is pointed more-or-less resembles the direction of forward progress ...

[RanRan]

It's interesting if you watch Paul Klaus doing his thing. (Klaus is my other hero, besides George). In the span of 3 seconds, he goes from full-tilt forward - hammered nose-down with full flaps - to jerking back to pitch the nose up while going to 0 flaps. 3 seconds. 3.5 max. Air-born.

Ground speed doesn't mean jack. It's about the Angle-of-Attack and getting there quickly.

[Clay Hammond]

It is about airspeed... and AOA. That full tilt you see in the video is a best case combination of the two. Tail up/reduced drag for the max acceleration in shortest distance, flap pop and back stick for the AOA/lift at slowest speed possible.

But all that was asked was about minimum take-off speed. For that simply begin your takeoff at three point and leave it there, note airspeed when aircraft breaks ground. Do it in all four configurations multiple times and determine average for each config. See which one is slowest.

They climb out best at around 45-50 if you're by yourself.

[RanRan]

Tail up/reduced drag ...

It took energy to get the tail up. The energy is still there kinetically, and stored there. If you think in terms of a fulcrum, Klaus reuses that kinetic energy to pivot the nose up and load the wings as he quickly makes the tail drop. He seems to pop off the ground by reusing that energy. I don't think drag comes much into play at that low speed.

[Clay Hammond]

Go out and try it. It does. Even more so on these lightweight little birds we're flying. My layman's brain says that from a three point position your thrust from the propeller is not being pointed in the same direction you are wishing to travel. Maybe its not so much any drag, but rather the lack of a full 100% of the available thrust being vectored in the same direction as the airframe. Raising the tail alleviates that and allows aircraft to accelerate to flying speed faster.

Try it. Its not so much the transition back to "up" elevator that gives you a strong reaction as it is the quick application of the flaps that sort of "pop" the aircraft off the ground. Then you retract them just as quickly to configure the aircraft for best climb.

There is a nice close up at the beginning of this video that illustrates what I'm talking about. The flaps come out first, then the stick is pulled back for the rotation.

[couleeone]

As always nice job Clay!

Here is 7AK in a 55' takeoff at the 2010 NWSC STOL contest. ..tailup..pull fullflaps and stick back simultanous then letting flaps off so slowly in ground effect

http://www.youtube.com/watch?v=V0glFRijVVc

RanRan thanks for you kind thoughts but I won't live long enough to get good enough to be anywhere near the same class as Paul Klaus!!! But thanks just the same!

[RanRan]

Enjoying the discussion and loved the video, Clay. OK, go watch Klaus' launch video on the kit-plane page.

After popping the tail up (actually beyond level) - he forces the plane back down to a 3-point! All three wheels are back down on the ground and lift off nearly simultaneously with, what appears to be, very little speed. So it remains my theory that that extra use of kinetic energy helped pop him off the runway a full second or two faster - all else being equal.

I just watched George's video - see the difference? George stayed in the 3-point through-out - i.e., he kept the tail pushed down.