Rejected Takeoffs

They Happen, So Plan Ahead

by Crista Videriksen Worthy

Ah, youth! The time when we do stupid things and hopefully live through them so we can enjoy being smart later. Many years ago, for fun, we landed on an extremely remote road. Trouble was, the local “Barney Fife” wouldn’t let us take off again. A few amused farmers gathered around our red Centurion. One woman with a large horse pasture offered, “You’re welcome to take off from my property… I don’t mind.” We measured the distance, noted the fence and telephone line at the end (our 50-foot obstacle), consulted the POH, and determined that we could depart. We tore across the field at full throttle, using the full array of short/soft field techniques. Alas, the grass grew longer and the dirt deeper. The fence and wires loomed ahead and above. About three-quarters of the way down, still on the ground, we pulled the power. Despite horsing back on the yoke, the nosewheel sank into the soft soil and broke. Thankfully, we were unharmed (and so were the prop and engine).

Just as the instrument pilot should always be ready to go missed during an instrument approach, the smart pilot should both plan ahead and be ready to abort before liftoff. Being ready will help you avoid a loss of control on the ground (LOC-G) should you have to stop. Having a plan helps you avoid a takeoff when something goes wrong, in which case you risk an in-flight loss of control (LOC-I). One of the NTSB’s primary topics in accident reduction efforts this year is LOC-I, which continues to be the top cause of GA fatalities. According to NTSB member Earl Weener, Ph.D., about 40% of GA fatal accidents involve LOC-I, especially during approaches to landing, maneuvers, and takeoff/climbout.

There are many reasons to reject a takeoff besides running out of runway. Some possible causes include a door or baggage compartment popping open, a brake dragging, abnormal instrument indications, unusual sounds from the engine or airframe, a strange smell, or an animal, person, or aircraft entering the runway. Outright engine failures are rare. Sudden airspeed fluctuations, or winds that cause the aircraft to swerve, requiring large rudder inputs, might indicate wind shear, another good reason for the prudent pilot to stop. Sometimes you just get a feeling that something isn’t right.

If you decide to abort, act immediately. You must simultaneously bring the power to idle and apply maximum braking, which can be tricky. If you brake too hard and lock the wheels you’ll actually decrease the friction applied and increase your stopping distance. It’s smart to go out and practice an aborted takeoff now and then, with or without an instructor. It might shorten the life of your brake pads, but it’s better than shortening your own life. One way to practice is to apply maximum braking after you land. Be sure to try it in different runway conditions so you get a feel for how much runway you’ll need to stop in the airplane you fly.

Plan each departure carefully. Airlines are required to have enough runway so that if they lose an engine they can either stop safely or fly away. For turbine aircraft, Takeoff Decision Speed (V1) is computed under Part 25 for current aircraft weight as well as runway and atmospheric conditions. Up to V1, a serious problem means you abort; above V1, you continue. Multi-engine aircraft have more leeway in the event an engine is lost. Most single-engine piston aircraft, however, can’t take off after an engine failure, so your decision is made simply by the speed at which you can still abort and stop on the remaining runway. If you’ve already reached rotation speed (Vr), your only decision is to figure out how to keep it on the runway, or avoid approaching obstacles. Use your POH or Owner’s Manual to estimate the runway necessary given the aircraft weight and conditions. You’ll usually find a ground roll component of takeoff for various conditions and surfaces, as well as data for landing ground roll. Add the takeoff and landing roll distances plus a generous personal safety margin for your reaction time to get a fair estimate of runway length required. For the safety margin, many pilots add an additional 50% of the landing roll distance; I use about 300 feet. If you have erratic winds and plan to lift off at a higher speed than what’s used in the POH, be aware that you’ll need significantly more runway.

Here’s another rule of thumb backcountry pilots use: On your takeoff roll, by the time you reach the halfway point of the runway, make sure you have a minimum of 71% (based on one over the square root of two for all of you physics nuts) of the rotation speed (Vr). For example, if you raise the nose at 65 knots indicated, then you would look for at least 46 knots indicated at the midpoint of the runway or immediately abort and apply full braking. Remind yourself of this before you begin your takeoff roll. That way, at the halfway point when you glance at your airspeed indicator, you know exactly what to do—abort or continue—without debate. This is a good practice for staying ahead of the airplane, even before you take to the taxiway. Play the “what-if?” game. Decide ahead of time what you will do depending on the possible emergency, given the current circumstances. Then you won’t have to think when something happens; you’ll just react instantly.

Naturally, a short runway changes the equation. You’ll still have to determine at which point it is possible to abort and stop before the end of the runway. The problem is, it may be well below the speed at which you break ground. Again, an emergency above Vr forces you to decide between continuing your takeoff or accepting that you will run off the end of the runway. The key point is that it may actually be better to run off the end than to try and coax a defective aircraft into the air. Remember, the force of an impact is related to the square of speed. Hitting trees on the ground at the end of the runway at 15 or even 25 knots is preferable to hitting trees in the air or otherwise crashing at 80 knots.

In our case, we paid a mechanic to field-repair the nosegear and secure a ferry permit. He then departed from the road in our airplane and flew it to his shop, where we picked it up—chastened, but uninjured, and a hopefully a little wiser for the experience.