I was also wondering about the STOL mods. I would think that would help get up a bit quicker. With the report above about a rather hairy experience, I too wondered if there were any "interesting" conditions. Maybe hot or at 7000ft or something?
Yes. Hot and high hurt all aircraft's performance numbers dramatically.
STOL will get you off the ground in limited runway space, but it will hurt climb performance and distance to clear obstacles after you're off the ground.
In my Robertson STOL equipped Cessna 182, since the flaps are down (you can delay extension but that's really "busy" during a takeoff) you also hurt acceleration performance.
Robertson's "STOL method" calls for holding brakes, rudder trim full right, full power, release brakes, select Flaps 30, and begin lift off at 45 MPH (38.25 knots) indicated, climb at 50 MPH (43 knots) indicated to clear obstacles, then accelerate to 75 MPH (64 knots) indicated and start retracting flaps, continue a normal climb out from there. Keeping in mind that max performance climb (Vy) is 89 MPH (76 knots) at full power, you can see how far behind the power curve a max-performance STOL takeoff is.
Book numbers:
Sea-level, zero wind, 59F, indicated airspeed at 50' of 49 MPH, 2800 lbs:
Ground run 390'
50' Obstacle 735'
7500', zero-wind, 32F, same speed, same weight:
Ground run 680'
50' Obstacle 1415'
To make this apples to apples, we have to use the book correction for temperature, which says:
"Increase distances 10% for each 20F." That's 1% for every 2F. So ...
7500', zero-wind, 59F...
59F-32F = 27F. We'll round up to 28. Add 14%.
680' x 1.14 = 775' Ground run
1415' x 1.14 = 1613' to clear 50' obstacle
And so on and so on.
The Robertson book is purposefully sneaky with temperature and not corrected to standard atmosphere. You have to do a bit of work in Excel to get "normalized" performance charts.
The one I really want to try someday is:
Sea-level, 20 knot headwind, 59F (or colder), 2000 lbs, indicated airspeed at 50' 43 MPH.
Ground run 65'
50' Obstacle 185'
The Robertson STOL tables stop at 2800 lbs. You're "extrapolating with your life" above 2800, which is annoying. They also don't provide numbers above 7500', and since they mix altitude and temperature for you on their charts, they don't give a correction factor for say... Leadville, CO's altitude.
And the numbers above require perfect pilot technique. There's no margin of error in them and Robertson says, "Increase speeds in gusty or severe crosswind conditions by 5 MPH for every 10 knots of gust." They do not publish what that does to the distance numbers, but obviously they go up.
Things I know from having done a few of these now for practice. Normally trained Cessna drivers will freak out at the following: Nose up angle (it's actually very flat and that weirds you out a bit - it tries to come off main gear first and you have to aggressively yank the nose off - otherwise it'll wheelbarrow), stall horn blaring (yes, you're down into your safety margin), lack of ability to accelerate for a few seconds (feels longer than that!), noises coming from the stall fences on top of the wings, disbelief that you're already off the ground, failure to maintain enough back pressure to stay that slow until 50'.
(Frankly I chickened out and accelerated a bit! GRIN!)
It also explains to your butt and eyeballs why the thing floats so bad if you try to land it at Flaps 30 or 40 with normal 182 speed numbers.
Book touchdown speed for STOL landings is 49 MPH indicated. It also specifically calls for doing that with power on. Power off, the descent rate with Flaps 40 makes the timing of the flare too critical and you're done flying *right now* if you yank the yoke back hard to arrest that descent. Power on, you just close the throttle to plop on if you time it right and keep that yoke back to protect the poor nose wheel. It'll drop the second you pull the power off.
Frankly other than hot, high, and heavy, you don't need STOL for that strip.
With our long-range 80 gallon/75 useable fuel tanks we can get to our max-gross of 2950 lbs before we get four adults on board pretty easy and that'd be problematic there. There's a paper STC to go to 3100 lbs for takeoff on the C-182P model, but it's still limited to 2950' for landing. To operate out of a short strip we'd leave the tanks down from the top. Catch-22 there also until you get to later models... bladder tanks like to be kept full when not in use.
Fun stuff, but even Robertson calls the Flaps 30 takeoff an "emergency" procedure to limit their liability if you're ham-fisted about it. Normal takeoff in the Robertson book is listed as Flaps 20. Most Skylane drivers usually use Flaps 10 if they have the runway. It's a more graceful rotation and climb out.
No flaps, a Skylane will chew up some serious runway at max-gross... but the climb out is rock solid. Little hard on the nose gear speed-wise, but nice in gusty or excessive crosswind conditions. Colorado Pilots Association teaches no-flap takeoffs in the mountains on the long paved runways so there's no question you're going flying and have a healthy airspeed margin before your go-stop point calculated prior to takeoff. Techniques for short unimproved strips are more the type of thing you see up at the school in McCall, Idaho.
