RFT 169: RTO

In aviation terminology, a rejected takeoff (RTO) or aborted takeoff is the situation in which it is decided to abort the takeoff of an airplane. There can be many reasons for deciding to perform a rejected takeoff, but they are usually due to suspected or actual technical failures, like an engine failure such as a compressor stall occurring during the takeoff run.A rejected takeoff is normally performed only if the aircraft's speed is below the critical engine failure  speed (sometimes called decision speed) known as V₁ , which for larger multi-engine airplanes is calculated before each flight.The Federal Aviation Administration defines V₁ as: "the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V₁ also means the minimum speed in the takeoff, following a failure of the critical engine at V_EF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance." Below the decision speed, the airplane should be able to stop safely before the end of the runway. Above the decision speed, the airplane may overshoot the runway if the takeoff is aborted, and, therefore, a rejected takeoff is normally not performed above this speed, unless there is reason to doubt the airplane's ability to fly. If a serious failure occurs or is suspected above V₁ but the airplane's ability to fly is not in doubt, the takeoff is continued despite the (suspected) failure and the airplane will attempt to land again as soon as possible.Single-engine aircraft will normally reject any takeoff after an engine failure, regardless of speed, as there is no power available to continue the takeoff. Even if the airplane is already airborne, if sufficient runway remains, an attempt to land straight ahead on the runway may be made. This may also apply to some light twin engine airplanes.Before the takeoff roll is started, the autobrake system of the aircraft, if available, is set to the RTO mode. The autobrake system will automatically apply maximum brakes if throttle is reduced to idle or reverse thrust during the takeoff roll.

An RTO is usually seen as one of the hardest tests an airplane has to undergo for its certification trials. The RTO test is performed under the worst possible conditions; i.e. with fully worn out brakes, the plane loaded to maximum takeoff weight and no use of thrust reverst. During an RTO test most of the kinetic energy of the airplane is converted to heat by the brakes, which may cause the fusible plugs of the tires to melt, causing them to deflate. Small brake fires are acceptable as long as they do not spread to the airplane body within five minutes (the maximum likely time for arrival of the airport fire fighters).

Most modern flight manuals specify 80 (Boeing) or 100 (Airbus) knots as the beginning of the "high speed" regime of the takeoff run, and recommend only rejecting the takeoff only in the case of

• Engine fire
• Engine failure
• predictive windshear
• aircraft unsafe to fly

A significant high-speed rejected takeoff accident highlights the importance of performing a high-speed RTO in the case of an uncontained engine failure that resulted in a fuselage fire. In this accident, the crew initially thought that they had experienced a tire failure and elected to RTO at 126 knots (V₁ was 146). The engine fire indication did not occur for 9 more seconds. If they had continued the takeoff, it is likely that all occupants would have perished instead of the 55 of the 131 passengers.

For discussion reference, a B777 at maximum takeoff weigh of 520,000 pounds on a standard day at sea level has a balanced field length of 6950 feet (Reference). On a typical runway length of 12,000 feet, such as runway 18L or 18R at Orlando International Airport, that leaves almost a mile of additional runway available for stopping.

Here is an excellent, comprehensive FAA publication about RTOs.As our way to help you celebrate the New Year, we’re offering the first book in the Hamfist series FREE!You can download the book in the e-book format of your choice at Amazon or Smashwords.