A flap is a high-lift device whose job is to lower the stalling speed of a wing at a given weight, yet it is also a drag device. Even the largest commercial airliners can still fly and land safely when the system fails, but in large airplanes such no-flap landings are sometimes only employed in case of an emergency. The crew must sustain a heightened pitch attitude throughout the approach, keeping the aircraft aloft longer before touchdown, and crews in simulator training have been known to fly the entire no-flap approach at 210 knots or higher. Because the plane will eventually get enough airspeed to fly normally without flaps, it is possible to fly without flaps. The Boeing 787, the A380 and others that have touched down without flaps, slats, spoilers or thrust reversers.
Can a plane fly with no flaps?
Yes, a plane can fly without flaps. Clean wings still produce lift, and in cruise flight most transports keep flaps and slats retracted for low drag. During take-off the same aircraft can climb even if its flaps are left up, but it must accelerate to a higher indicated speed, so the runway required lengthens and climb gradient falls. Rough-field or short-field operations are impossible, yet once airborne the level-flight envelope is legal for jets so long as obstacle-clearance margins and certification speeds are respected.
Problems appear only when airspeed is low, because high-lift devices like Fowler flaps change the camber and increase wing area, thereby reducing stall speed. Slats on the leading edge act as another high-lift device, since slats increase lift and are positioned on the leading edge. Remove both devices and the margin between approach speed and stall speed collapses. The Gimli Glider descended power-off and could not extend its slats, illustrating how extra kinetic energy along a longer glide track is necessary for landing. The Commonwealth under-carriage reached the ground alive, but modern airlines forbid deliberate flapless take-off.
Can a plane take off without flaps?
The airplane can lift off at a lower speed when flaps are extended, yet it remains possible to depart with flaps retracted. In that case the commercial aircraft needs faster takeoff speeds to generate the required lift. Several fleets, among them Airbus A300 and Boeing 767, are approved for such take-offs, and such take-offs being done regularly on long runways where the extra ground roll is acceptable. Fokker 70 and Fokker 100 take off even on short runway by relying on high thrust and precise rotation technique, demonstrating that, while flaps set downward at a moderate setting ease the rotation, they are not strictly obligatory for safe lift-off.
Can a plane land without flaps?
A plane can land without flaps but the price is a higher approach speed, and higher approach speed increases landing distance. Pilots calculate a no-flap reference speed that is fifty percent above the normal figure, then add the mandatory margins. The result is a long, fast roll that needs a longer runway.
The Gimli Glider could not extend its flaps, yet the crew brought the 767 to a safe stop on the decommissioned runway. Their success shows that skill, long pavement, and generous speed margins are required when the high-lift devices stay stowed.
What happens if a plane lands without flaps?
If the flaps are not extended, the speed required increases. Flaps are used to add both lift and drag so that, approaching the runway, the airplane can decelerate steeply and still remain above the minimum speed at which it stalls. If the flaps refuse to extend, this excess lift is lost, so the pilot has to fly faster and at a steeper pitch in order to keep the wing working. Because less drag is created, losing altitude becomes harder and the resulting descent angle is shallower. Checklists indicate the exact amount of additional runway needed, and that figure rises to as much as 50 percent of the normal landing roll. Higher approach speed, coupled with longer ground roll, therefore precludes the use of a short runway.
During landing the pilot must flare excessively because without flaps this will cause the tail to strike the runway. Instead the aircraft is held at a higher nose-altitude while touching down faster and farther along the surface. Higher airspeed results in a longer landing roll. Pilots must adjust their techniques to compensate for higher approach speeds, longer landing distances and a shallow descent angle so that the landing remains safe even when the high-lift devices have failed.
Are there aircraft with no flaps?
Yes, some light airplanes fly with no flaps at all. The Piper J-3 Cub and the Piper Vagabond are two popular examples whose wings carry plain, un-slotted trailing edges. Designers accepted higher landing speeds and longer ground rolls in exchange for mechanical simplicity and lower weight, and the resulting aircraft still serve trainers and leisure pilots well.
Yet these machines are exceptions. Most general aviation aircraft are equipped with flaps. From Cessna 172s to Beech Bonanzas, the familiar 40-degree or 30-degree setting is deemed normal equipment, giving pilots the slower approach and steeper glide path that short runways demand.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
