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The standard rotation rate for most transport category aircraft is typically set at 3 degrees per second. When an aircraft reaches this rotation speed during takeoff, the pilot is expected to smoothly pull back on the controls to establish a specific pitch attitude. This pitch attitude can vary depending on the aircraft model but is typically around 12 to 15 degrees for most jet aircraft. It’s important to achieve liftoff within 4 to 5 seconds after reaching the rotation speed to ensure that the certified takeoff performance parameters are met.
If the rotation rate is slower than the standard 3 degrees per second, the aircraft will cover more ground without becoming airborne. This results in an increased takeoff distance, which can be problematic.
The takeoff distance required for an aircraft is defined as the distance from the point at which the brakes are released to the moment the aircraft reaches a height of 35 feet with one engine inoperative. This 35-foot mark represents the minimum clearance over obstacles, and a slower rotation rate prolongs the time and distance needed to reach this point. As a consequence, the margin for obstacle clearance is reduced.
For aircraft certified under CS-25 regulations, two takeoff distances are calculated. One considers takeoff with all engines operating, adjusted by a factor of 1.15 to account for safety margins. The other calculation is based on taking off with one engine inoperative, without the additional factor. In most cases, especially for twin-engine aircraft, the latter calculation is the limiting factor because the loss of an engine significantly affects the climb performance. This underscores the importance of proper rotation technique, especially in the event of an engine failure.
In the case of a four-engine aircraft, the loss of a single engine doesn’t have as significant an impact on performance, and the takeoff is typically limited by the former calculation. Consequently, quad-engine aircraft require precise control from pilots to achieve the advertised performance during routine operations.
Author – Nischal Paudel
Pilot
