Ask the Captain: How is takeoff speed determined?
Question: When a plane is speeding down the runway, what determines when liftoff occurs. Is this the pilot's decision?
--submitted by reader Jeff, New York City
Answer: The speed at which the airplane lifts off is determined by the weight, temperature, altitude of the runway and the slat/flap setting. Before beginning the takeoff roll, the crew has calculated the speed at which there is no longer an option to stop on the runway (known as V1), the speed at which the nose is raised (known as Vr) and the speed to climb if an engine fails (known as V2). The airplane becomes airborne (lifts off) shortly after the rotation speed and the nose is raised.
Q: I am always very nervous when the plane is taking off, as I fear a loss of engine power at this critical moment. In fact, a friend of mine, who is an airline pilot, tells me that most pilots have that secret fear also. What can be done in the event of a loss of power upon takeoff? - Al, New York City
A: I, respectfully, strongly disagree with your friend who says that pilots have a secret fear of engine failures. None of the professional pilots I know have ever expressed such a concern to me. Pilots regularly train for engine failures so that it becomes just another abnormal situation to handle. All transport airplanes are certified to either be able to stop on the runway after an engine failure or continue the takeoff safely. Before every takeoff, pilots perform performance calculations to determine the proper speeds and flight path in the event of an engine failure.
During training sessions, pilots practice and demonstrate competency handling the failure of an engine at the most critical time of the takeoff. Today's turbine engines are incredibly reliable, making the chance of an engine failure very unlikely, but if it occurs the pilots are well-trained and able to handle it successfully.
John Cox is a retired airline captain with U.S. Airways and runs his own aviation safety consulting company, Safety Operating Systems.