To Go - or Not to Go? Rejected Takeoffs

Mobility Forum, Sep/Oct 2004 by Meintel, Julie

There is an old adage about planning and thinking ahead that goes something like this - "When you fail to plan, you plan to fail." Rarely is this truer than in the world of aviation, where failing to plan can result in multi-million dollar losses and the incalculable cost of lost lives. The aviation world can be very liberal and forgiving, but within minutes it can turn harsh and demanding, leaving little to no room for error. Systems on board many types of aircraft are redundant, making numerous ways to solve in-flight problems - if one system doesn't take care of the issue, another one can. Most problems that can occur at altitude do not necessarily constitute a grave emergency, so there is time to work together as a crew to solve problems.

The most high-risk phases of flight occur at takeoff and landing, when conditions can change quickly and when pilots are often the most task-saturated. Failing to plan for an emergency during these critical times is dangerous and often deadly.

An article published in AOPA (Aircraft Owners and Pilots Association) magazine by Bruce Landsberg gives several examples of accidents that resulted in the loss of life because of poor planning and poor decision-making during a critical phase of flight. Some go/no-go accidents occur because of mechanical problems that arise during the course of the attempted take-off, but the majority of accidents and incidents are a result of inadequate preflight inspections.

Also to blame in many accidents is the mind-set of the crew. "We've taken off in this airplane hundreds of times and nothing has ever gone wrong before." "We're very experienced, and we know what we're doing." "Let's just get off the ground and get going. Nothing's going to go wrong." Any of this sound just a little bit familiar?

Just because you've never had a particular problem before is no guarantee that it won't happen this time. You've done your preflight work, you're ready to get up there, and the aircraft cooperates beautifully - until it doesn't. And then what do you do?

Go/no-go decision-making needs to be part of every preflight briefing, and all crew positions need to be aware of what would constitute a condition that warrants an abort. If the loadmaster calls for abort, the pilots need to react in a split second to pull the power back and get on the brakes. There's no time for discussion until the aircraft has either stopped or taken flight.

So why would you reject a takeoff? A good place to start is figuring out when to abort your takeoff, if in fact you need to. There seems to be some lingering confusion about the difference between decision speed and Vl. According to Don Simpson of the FAA, "Vl is not decision speed. It is actually the maximum speed at which the first action must be taken to stop the airplane within the accelerate-stop distance." The first action is usually pulling back the throttles, and this must occur at Vl.

In 1998, new rules were set in place in Amendment 92 to FAR Part 25 regarding rejected take-offs, and according to a panel of experienced pilots, even the new rules leave room for doubt and perhaps potential for disaster. The new rules add two seconds of rolling on the runway to the minimum stopping distance for a rejected take-off. Furthermore, the stopping distances must now be calculated using worn brakes and wet runway conditions. In other words, the stopping distance is to be planned for in a worst case-scenario. Even so, many pilots seem to feel that the new rules don't go far enough to provide an acceptable margin of safety. The chairman of ALPA's (Airline Pilots Association) Airworthiness, Performance, Evaluation, and Certification Committee, Captain Ron Rogers, says "The usual course is to say let's take it slow and easy. That usually works - except for abort emergencies, where you've pumped a lot of energy into the brakes."

Boeing actually published an in-depth coverage of rejected take-off scenarios. The message this report conveys seems to be that the wisest course of action is to continue the take-off once you have reached 100 knots, unless there is a serious and catastrophic emergency or loss of thrust. So what constitutes a serious and catastrophic emergency? Many pilots agree that there are four good reasons to abort after 100 knots:

1) any engine failure,

2) any engine fire,

3) any thrust reverser light, and

4) smoke in the cockpit.

What's the big deal about 100 knots? Why is that considered a kind of "cut-off"?

First, and probably most important, the vast majority of accident and incident statistics support the decision to "go" after that speed - many accidents happen when pilots try to reject the take-off after 100 knots. And most aviation experts agree that 100 knots makes sense for both light and heavy aircraft. A lighter aircraft will accelerate faster, but it will also stop faster, so it takes up significantly less runway. In a lighter aircraft, 100 knots is closer to Vl than it is in a heavier jet, but the fact that it needs less runway to stop gives the pilot a little extra breathing room when considering whether to abort.