Sometimes, the choice to abort is complicated by other possibilities — the unpleasant things that will likely happen if you stay on the ground but not on the runway.
If running off the end of the runway will launch you at slow speed over a cliff, or into a fuel farm, a busy street or a crowded schoolyard, you may consider taking drastic action. NOTE: This is the sort of thing you need to decide before you begin your takeoff roll, because you might not have time to evaluate the decision when actually aborting a takeoff.
Strategy: Some pilots of retractable gear airplanes contemplate pulling up the gear to stop short in extreme circumstances. Others in all types might consider “ground-looping” the airplane by stomping hard on one rudder pedal, pivoting the airplane around before running into the hazard (tailwheel airplanes do this best). In zero wind most airplanes will ground loop easier to the left with the aid of the propeller’s torque; with a wind, turning into the wind will result in a more dramatic ground loop. If you take either of these actions, though, do so knowing you may be assuming the risk of injury to yourself and your passengers in order to save others, and you’re very likely to damage the airplane in the process. It’s a trade-off circumstances may make it easy to accept — if you think about it ahead of time.
“ACCELERATE-STOP” — BY THE BOOK
Avoiding a runway overrun in a takeoff abort, however, is the best action. How do the Federal Air Regulations (FARs) address planning to avoid overruns?
Part 91 (private, noncommercial) flights have no specific runway length requirements. FAR 91.103 does insist we “become familiar with all available information” regarding “runway lengths at airports of intended use” and “the takeoff…distance” contained in an approved Flight Manual for the airplane. If no Flight Manual is published for that aircraft type, we need to know “other reliable information appropriate to the aircraft, relating to aircraft performance under expected values of airport elevation and runway slope, aircraft gross weight, and wind and temperature.” If we can compute that our airplane as loaded will take 2500 feet to reach rotation speed given the runway and weather, then we can “legally” take off from a 2501-foot runway. …But is that safe?
In the best of worlds you’d be able to attempt a takeoff all the way up to rotation speed, detect a problem, and then abort, bringing the airplane to a stop before the end of the runway. In fact, most multiengine airplanes have what’s called an “Accelerate/Stop” chart in the Performance section of the POH to help pilots quantify this. “Accelerate/Stop” is the computed distance, considering aircraft weight, density altitude and wind, that it would take to begin a takeoff roll, reach rotation speed, immediately begin an abort, and come to a stop. Most multiengine pilots consider it prudent to operate only from airports meeting the accelerate/stop distance for their airplane, considering the increased statistical likelihood of having trouble during takeoff (all else is equal, and twice the engines means twice the likelihood one may balk on any given day). Can I legally, and even safely, fly a Baron out of an airport that doesn’t meet Accelerate/Stop criteria? Sure … but I’ll know beforehand that an abort begun anywhere near rotation speed will cause me to go off the end of the runway, and I need to have a plan for what I’ll do already in mind before advancing the throttles for takeoff.
What if you fly an airplane that doesn’t have an Accelerate/Stop chart? You can approximate one if you realize that your rotation speed is usually very close to your touchdown speed in the same airplane at the same weight. If that’s the case, all you need to do to figure an Accelerate/Stop distance for your airplane is to compute the takeoff distance and the landing distance under those conditions, and add the two.
…AND THE MARGIN FOR ERROR
Whether computed directly from an Accelerate/Stop chart or approximated using Takeoff and Landing Distance computations, the resulting runway requirement does not assume any margin. It’s standard practice to multiply those distances by at least 1.5, to allow for pilot reaction time and to provide a cushion for less-than-perfect braking surfaces or pilot technique.
WHAT NOT TO DO
Don’t begin a takeoff unless you’ve consciously evaluated the risks involved — and thought through a plan to deal with a failure to meet your takeoff targets (speeds and distances). Once you’ve begun rolling, avoid distractions — a door opens, a window pops out, a passenger speaks up, or you realize you’ve forgotten something. The only thing between you and tragedy is your ability to maintain control of the airplane. Abort if it’s called for; but be aware that in some instances it may be safe to take off, fly the pattern and land before trying to close that door or go back to the FBO for your briefcase.
THE BOTTOM LINE: You won’t be ready to safely abort a takeoff unless you plan what you’d do now. Chances are you’ll actually call off a takeoff “on the roll” so very rarely that you’ll never gain experience from the actual event — you need to train for it, and more importantly, you need to think it through. Sit in the cockpit and work through the process of maintaining control, reducing power and braking. Imagine scenarios where it appears you’ll run out of runway. Go through the motions of shutting off fuel and electricity as you prepare for impact. Consider the “targets” of speeds and distances that you need to hit to make a successful takeoff, and be ready to call the whole thing off if you miss those targets. Whatever you do, never delegate your responsibility to act as pilot-in-command.