28
$\begingroup$

Depending on the airframe, there are a number of techniques to reduce the Take Off Distance required. For example, deploying flaps.

What advantage is there to NOT using short field take offs, even when runway length is sufficient? Surely it's always advantageous to require the minimal amount of runway, thereby adding a larger margin for error?

Improve this question
$\endgroup$
2
  • 1
    $\begingroup$ In my opinion –and that's why this is a comment and not an answer– if you have a long and smooth runway, it's better to take off in a sedate way, using little or no flaps... Short-field techniques should be reserved for short/rough runways. $\endgroup$
    – xxavier
    Feb 9, 2018 at 18:12
  • $\begingroup$ Best rate of climb vs best angle of climb $\endgroup$
    – Steve Kuo
    Jul 19, 2018 at 3:31

7 Answers 7

Reset to default
40
$\begingroup$

Short-field take-off techniques often achieve a shorter ground run by hurting climb performance. While having more runway is great for safety, planning to use less of the runway is not a huge benefit: you always plan to have enough runway left if you need to abort during the take-off roll. It's much better to have more height quickly in the climb-out: it gives you more margin against obstacles after the runway's protected area, and it gives you more height to land in case of an engine failure after take-off (EFATO).

The numbers for a normal take-off optimise for a good rate of climb, which has the greatest benefit to safety. A short-field take-off gives you an extra option when the runway length is too short for that - at the cost of some margin if there's a problem in the climb-out.

Improve this answer
$\endgroup$
1
  • $\begingroup$ Technically, climbing at Vx (best angle) is better for obstacle clearance than a normal Vy (best rate) climb, though, right? Vy does gain altitude faster per unit time, but doesn't gain altitude as quickly per unit horizontal distance (because the speed over ground is slower.) $\endgroup$
    – reirab
    Feb 12, 2018 at 16:26
18
$\begingroup$

First off as the pilot in command, you are free to do this if you feel it is the safe way to operate the aircraft in a given situation even if runway does not dictate it.

According to the FAA's handbook the short field take off requires a high degree of control of the aircraft,

The pilot should be aware that, in some airplanes, a deviation of 5 knots from the recommended speed may result in a significant reduction in climb performance; therefore, the pilot must maintain precise control of the airspeed to ensure the maneuver is executed safely and successfully.

While an experienced pilot may be ok with this student pilots and newly minted ticket holders may feel less comfortable and thus choose to only fly from runways where this is not required, although it should be noted this is part of the ACS and thus part of getting at least a PPL here in the US. Due to the degree of precision the maneuver may be used less than a standard takeoff.

There is an interesting article here worth reading on the topic.

Improve this answer
$\endgroup$
12
$\begingroup$

As Dave and others have already mentioned, short-field takeoffs result in taking off with significantly less airspeed than usual. Your goal in a short-field takeoff is essentially to fly the plane just slightly above the point where it is not flyable. As a result of this, the margin for error in a short-field takeoff is considerably smaller than in a normal takeoff. In addition to the relatively poor climb-out performance mentioned in Dan's answer, you're intentionally trying to fly just beyond stall speed. Relatively small wind gusts can put you back on the ground in a hurry, as could momentarily pitching up too much.

All-in-all the short-field takeoff is just a relatively more dangerous way to take off if you have sufficient runway for a normal takeoff.

  • You'll have less control authority and, so, less ability to correct the plane's attitude in gusty conditions.
  • You'll have less airspeed and be more susceptible to stalling at low altitude (whether due to gusty winds, accidental excess pitch, or a combination of the two.)
  • You'll also be less able to climb clear of obstacles at the end of the runway.
  • The flaps will also be providing additional drag, so you'll use up more horizontal distance in order to get up to speed for the climb-out.

Your only real gain for all of these trade-offs is that the wheels will have a shorter roll across the ground, so it's just not worth it unless you really don't have the runway to spare.

Improve this answer
$\endgroup$
3
  • 3
    $\begingroup$ re: clearing obstacles: so the overall higher drag from being in the air with flaps is worse than from rolling down the runway for longer, and lifting off closer to whatever obstacle? I guess that makes sense, because you're getting the lift for nearly free when it's coming from contact force of your tires (with your wings nearly horizontal), vs. from pushing on air at a higher angle of attack. So even though you get into the air sooner, you still have less height at the far end of the runway. $\endgroup$
    – Peter Cordes
    Feb 10, 2018 at 8:56
  • 1
    $\begingroup$ @PeterCordes Correct. When rolling across the ground with 0-10 degrees of flaps, your engine power is going mainly toward forward acceleration of the aircraft (granted, the tire contact with pavement does add some drag, but not as much as actually flying, let alone with full flaps at low airspeed.) When doing a short-field takeoff, the extra flaps are creating extra drag, which some of your thrust must counter and, once you get airborne, you're using a lot of your thrust to counter drag in order to be able to fly. $\endgroup$
    – reirab
    Feb 10, 2018 at 22:30
  • $\begingroup$ @PeterCordes That's an interesting point, about the lift from the tires! $\endgroup$
    – yo'
    Feb 12, 2018 at 10:37
10
$\begingroup$

Short field takeoffs are more complicated than simple takeoffs. That is why they are taught later, once you are familiar with normal takeoffs.

Depending upon the plane, there are several steps you need to take for a short field takeoff: add flaps, line up before the piano, press brakes, full power, check engine gauges, release brakes, etc.

This is simply more complicated than full throttle/check engine gauges. There are a thousand things that you need to keep in mind while flying. It is best to keep simple things simple. Of course you can always do short field takeoffs if it pleases you. Most runways you will takeoff from will be long enough from a GA perspective. In case the runway is short, you should of course use the short field technique. :)

Improve this answer
$\endgroup$
2
  • $\begingroup$ There’s an argument to be had for standardising towards a common procedure though. Arguably, it is more likely the short field takeoff will be carried out below required standards when it matters most if the procedure is rarely used. Of course, as stated in another answer, the potential decrease in climbout performance should be balanced against that. $\endgroup$
    – Cpt Reynolds
    Feb 9, 2018 at 23:03
  • 6
    $\begingroup$ @Cpt Reynolds: Common procedure would be good if all runways (and other surfaces one might wish to take off from) were identical. But brakes & full power are not a good thing to do on a grass or dirt strip. $\endgroup$
    – jamesqf
    Feb 10, 2018 at 3:41
6
$\begingroup$

I used to fly a 4-seater Rallye Minerva, and, if I recall correctly, the recommended short field take off involved putting on full flaps (30°) just before liftoff speed (the flaps were operated by a handbrake sort of affair) and then basically flying level until an appropriate speed was attained.

While no takeoff was relaxing, this procedure was a little unnerving (it took quite a bit of effort to latch the flaps in, and there wasn't always a second chance), and certainly not one I would use on a regular basis. A crosswind added to the tension as the liftoff speed was fairly slow (something like 42KT).

This was a lot more work than I would want to do when operating from a busy airport, and generally reserved for shorter 'fields' (100m, yep, you read that right).

Improve this answer
$\endgroup$
0
$\begingroup$

Furthermore, you want to minimize the time of full power to the engine to reduce the chance of its failing. You also want to keep fuel burn down so there's more reserve at the end - or less to be loaded to start, allowing more payload.

A "normal" takeoff improves all the above along with airspeed margins, visibility over the cowling, cooling airflow to the engine and more. All of which are benefits it offers compared to a short (or soft) field takeoff.

Improve this answer
$\endgroup$
0
$\begingroup$

I would say it all depends on the aircraft and its POH and also the runway itself (soft or hard). For instance, in the Cessna 150/152 (and I believe 172), the short field takeoff (with obstacles) requires no flaps, so there wouldn't be any penalty for the climb rate and would always be advantageous unless on a soft field. If there is no obstacle, 10 degrees of flaps would get you off the ground quicker and give you if I recall correctly a 10% penalty on the climb rate, which could be a good trade. But some aircraft requires more flaps, or the penalty on the climb rate is higher than others.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.