True story 
I had read somewhere in a book (I believe it was “fate is the hunter”) that on takeoff, the pilot used to hold the breaks, put full throttle, wait for the airflow to build up and then release to breaks and start the take off roll.
In the UK, 700m runway C152, instructor A:
Once I tried the same once with my instructor early on during my PPL. The instructor asked what was I doing. I simply told him I read it somewhere that this way you use less runway. He replied that it doesn’t make any difference and there is no need to do it at all.
In Malta, 1500m runway C172, instructor B:
During a checkout flight before I could rent the aircraft, I lined up on the runway, applied full power and started rolling. The instructor cut out the power and told me to hold on the breaks, after which he applied full power, let the airflow build up and then told me to release the breaks. “You will use less runway this way” he said.
Does it really make any difference or not? What do you think who was right A or B?
The idea is less that “the airflow builds up” but that the engine develops full power before you go.
I once tested it for a magazine article, and the difference was really marginal. On a 1500 m runwayin a 152 it’s outright stupid, on a 700 m runway ina C-152 it’s unneccessary.
If I want to leave the ground as early as possible I do a rolling take-of from the holding point.
The answer is “it depends”. On a soft grass runway holding the brakes with full power will achieve nothing other than digging the nosewheel deeper in the grass, so you’d be better off with a rolling departure from the taxiway.
I have never seen figures for piston singles, but the AFM of a Citation Bravo that I have here on my iPad gives a difference of 500ft of ground roll between a static takeoff and a rolling takeoff. All the performance figures are based on the static takeoff. So whenever you need book performance for takeoff distance and net climb path you are required to perform a static takeoff. Which is fun for the crew but scary and unpleasant for the passengers and tends to mess-up their smartly arranged luxury catering.
I agree with others that it will hardly matter in a SEP, because you can go from idle to full power almost instantaneously.
However, I can imagine how this practice filtered into the SEP world. Jet engines cannot spool from idle to full power instantaneously. They need a few seconds to spool up. Furthermore, if on a twin jet one of the engines spools up to full power but the other develops a fault and does not produce full power, the pilots will be unable to prevent the aircraft from veering off to the side of the runway. In jet airliners it is therefore common practice to spool both engines up to about 50%, wait for them to settle and then go to 100% power. You can actually feel this when they’re taking off. This process takes a few seconds and in that time the aircraft will travel a significant distance – maybe 100 meters or so. So on a marginal runway, it makes sense to do this while holding the brakes. Only in a non-marginal situation would you do this while rolling.
I can well imagine that flight schools that train students for the airlines have put this in their SOP: On a marginal runway you hold the brakes until the aircraft is confirmed to develop 100% power, while on a non-marginal runway you do a rolling take-off. It ingrains the thinking about selecting the proper take-off technique very early on in their careers.
Having said that, there are also aircraft where holding the brakes with full power is expressly prohibited. Not sure, but I think the Spitfire is one such aircraft. At full power, the torque/p-factor/whatnot of the prop is such that you cannot counter it unless you have at least a certain amount of airspeed over the rudder. So you have to take off with a certain limited power setting, until you achieve a certain airspeed (but are still on the ground), and only then can you go to full throttle.
(BTW Am I the only one who read the thread title and though “Well, no, the amount of weight you lose during a (bathroom) break will hardly matter to the take-off performance, but it will make a hell of a difference in comfort, especially on a long flight”?)
Yes, because Jet Engines need a much longer time to develop takeoff-thrust. In a 152/172 that’s a very short time only. In a typical spam can the difference is really marginal. Maybe you can squeezeout some meters though … but i prefer a rolling take-off then, or a short field take off for that matter …
BackPacker wrote:
Furthermore, if on a twin jet one of the engines spools up to full power but the other develops a fault and does not produce full power, the pilots will be unable to prevent the aircraft from veering off to the side of the runway.
No aircraft would get certified and no pilot would pass his checkride if maintaining directional control upon uneven engine spool-up (or failure of an engine at any time – from commencement of takeoff roll to stopping after landing!) would be a problem.
It is just a function of time to full power and how much power is generated getting to full power. A jet has a lot of power and takes time to get to takeoff thrust so covers a lot of distance relatively speaking before takeoff thrust is generated. A C152, takes no time to get to almost no power so it is irrelevant.
But it must be true for all types that a static takeoff uses less runway.
JasonC wrote:
But it must be true for all types that a static takeoff uses less runway.
As discovered by Mr. Newton 200 years before the first powered aeroplane took to the air 
It depends on what you are flying. In a tail wheel you want to get the tail up as fast as possible. This is taken to the extreme here:
