JT is, as usual, correct and also displaying his measured and conversational response.
TAke off, and landing, performance is determined in accordance with the rules laid out in the FAR
(a) For normal, utility, and acrobatic category airplanes, the takeoff distance must be determined in accordance with paragraph (b) of this section, using speeds determined in accordance with §23.51 (a) and (b).
(b) For normal, utility, and acrobatic category airplanes, the distance required to takeoff and climb to a height of 50 feet above the takeoff surface must be determined for each weight, altitude, and temperature within the operational limits established for takeoff with --
(1) Takeoff power on each engine;
(2) Wing flaps in the takeoff position(s); and
(3) Landing gear extended.
(c) For commuter category airplanes, takeoff performance, as required by §§23.55 through 23.59, must be determined with the operating engine(s) within approved operating limitations.
[Doc. No. 27807, 61 FR 5185, Feb. 9, 1996
This is not the latest amendment but adequate for reference.
Once the speeds determined in 23.51 have been determined they are applied to the procedure defined in AC23-8C. Note, the reference speeds used are minimums and the manufacturer may choose to vary them up, and lengthen distances, but not reduce them to in order to Shorten Take Off or Landing.
As the FAR and the AC has been reviewed and amended to higher standards over the years even more prudent procedures and tolerances have been introduced which means the exact same aircraft designed many years ago would have longer distances in the POH if it is done to latest standards. Nowhere is a procedure that reduces to prescriptive methodology mentioned.
TOL distances are THE distances and the POH is required, these days at least, to specify the method that the pilot must use it achieve the chart performance numbers. Vr, or rotation speed, the speed at whihich the pilot may apply the control input intended to raise the nose wheel clear of the pavement, is determined and included in the procedure specified in the POH.
So, STOL does not apply to civil aircraft, although techniques intended to minimise ground roll, if applied may provide improved numbers.
The AC states that technique used for the charts is NOT to be one that requires exceptional skill and/excessive forces, but that that can be emulated by a normal or average pilot. This includes references in the procedures to not require doing two actions simultaneously, and deliberately introducing small delays between actions during the testing process.
Fly the procedure in the POH, get the numbers and power settings perfect and book numbers are readily attainable, be well practices and react quickly, raise flaps immediately after touch down, and you may even achieve shorter distances, but without reducing the speeds, and energies, physics will basically rrule this equation.
Testing, and the book numbers require the vehicle to be over max weight, and slightly forward of max fwd CoG for all tests as an additional factor so that the numbers are conservative in any case. Manufacturers, not in this country, have been known to run engines in specially and ensure that although the engine has time on it, it is measured to optimum wear specifications and making best power. Brand new engines are the most sluggish until they have loosened up, and do not typically provide best performance. Heritage US manufacturers often gamed the system, which is why the rules are much tighter now.
Vr, Vtoss, Vy, Vx, and Vref are all factored for weight in modern certifications, but not for CoG, so performance can be slightly improved with an aft loading, which is not accounted for in the charts.
HD