Leading edge cuff
Encyclopedia
Leading edge cuffs are a fixed aerodynamic
device employed on fixed-wing aircraft
to modify the airfoil
used. They may be either factory-installed or, more commonly, an after-market modification.
In most cases a leading edge cuff will "droop" the leading edge of the airfoil. This has the effect of causing the airflow to attach better to the upper surface of the wing at higher angles of attack, thus lowering stall
speed. This allows lower approach speeds and shorter landing distances. They may also, depending on cuff location, improve aileron
control at low speed. A further benefit is that a cuff may produce a more gradual and gentler stall onset, particularly where the original airfoil had a sharp leading edge shape.
Where a factory modifies an existing design by the addition of a leading edge cuff it is often due to an identified problem or deficiency in the original airfoil used. One example of this is the American Aviation AA-1 Yankee
, which was modified with the addition of a leading edge cuff to become the AA-1A Trainer. This was a result of flying schools operating the Yankee demanding a lower approach speed and gentler stall characteristics from the manufacturer.
Several after-market suppliers of STOL kits make use of leading edge cuffs, in some cases in conjunction with such other aerodynamic devices as wing fence
s and drooping ailerons.
Leading edge cuffs can exert an aerodynamic penalty for the lower stall speed obtained. The amount of the penalty depends on the airfoil design they are installed on and the amount of "droop" that they incorporate. The installation of a leading edge cuff often results in some loss of cruise airspeed. In the case of the modification of the AA-1 Yankee to the AA-1A Trainer the loss of cruise speed amounted to 8 knots or 7%. Better design techniques developed in the 1980s largely mitigated this penalty and leading edge cuffs are used on current high performance light aircraft like the Cirrus SR20
and Lancair Columbia.
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
device employed on fixed-wing aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
to modify the airfoil
Airfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
used. They may be either factory-installed or, more commonly, an after-market modification.
In most cases a leading edge cuff will "droop" the leading edge of the airfoil. This has the effect of causing the airflow to attach better to the upper surface of the wing at higher angles of attack, thus lowering stall
Stall (flight)
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded...
speed. This allows lower approach speeds and shorter landing distances. They may also, depending on cuff location, improve aileron
Aileron
Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...
control at low speed. A further benefit is that a cuff may produce a more gradual and gentler stall onset, particularly where the original airfoil had a sharp leading edge shape.
Where a factory modifies an existing design by the addition of a leading edge cuff it is often due to an identified problem or deficiency in the original airfoil used. One example of this is the American Aviation AA-1 Yankee
Grumman American AA-1
The Grumman American AA-1 series is a family of light, 2-seat aircraft. The family includes the original American Aviation AA-1 Yankee Clipper and AA-1A Trainer, the Grumman American AA-1B Trainer and TR-2 and the Gulfstream American AA-1C Lynx and T-Cat.-Development history:The Yankee was...
, which was modified with the addition of a leading edge cuff to become the AA-1A Trainer. This was a result of flying schools operating the Yankee demanding a lower approach speed and gentler stall characteristics from the manufacturer.
Several after-market suppliers of STOL kits make use of leading edge cuffs, in some cases in conjunction with such other aerodynamic devices as wing fence
Wing fence
Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Not to be confused with wingtip fences, wing fences are flat plates fixed to the upper surfaces parallel to the airflow. They are often seen on swept-wing aircraft...
s and drooping ailerons.
Leading edge cuffs can exert an aerodynamic penalty for the lower stall speed obtained. The amount of the penalty depends on the airfoil design they are installed on and the amount of "droop" that they incorporate. The installation of a leading edge cuff often results in some loss of cruise airspeed. In the case of the modification of the AA-1 Yankee to the AA-1A Trainer the loss of cruise speed amounted to 8 knots or 7%. Better design techniques developed in the 1980s largely mitigated this penalty and leading edge cuffs are used on current high performance light aircraft like the Cirrus SR20
Cirrus SR20
The Cirrus Design SR20 is a piston engine composite monoplane that seats four. The SR20 is noted for being the first production general aviation aircraft equipped with a parachute designed to lower the aircraft safely to the ground after loss of control or structural failure.-Design and...
and Lancair Columbia.