A Krueger flap is a leading-edge device formed from a panel on the wing's lower surface. A hinge fitting inside the leading edge carries the panel around and forward so its former lower surface becomes part of the deployed leading-edge contour.
Krueger Flap Mechanism Interactive Calculator
Compare entered clean and deployed maximum lift coefficients and speeds alongside a conceptual panel-rotation drawing. The motion does not predict the aerodynamic values.
Equation Used
- Clean and deployed values use comparable definitions supplied by the user.
- The visual represents a simple Krueger panel with an internal/goose-neck hinge rather than a specific variable-camber four-bar installation.
- No aerodynamic, structural, actuator-force, synchronization or aircraft-performance model.
Deployment angle drives only the illustrated panel rotation; no relation to CLmax, speed, actuator load or aircraft performance is calculated.
Leading-edge panel deployment
In the simple form, a hinge located inside the wing leading edge connects to the lower-surface panel through a goose-neck fitting. Actuation rotates the panel forward and down from its flush stowed position toward a deployed leading-edge position.
A leading-edge high-lift device
Krueger devices deploy panels from the wing underside. Simple and folding forms use different supports from variable-camber systems; the latter need additional linkage to change panel shape. This page does not represent a particular aircraft installation.
Compare entered states
ΔCLmax=CLd−CLc. Relative change is 100ΔCLmax/CLc. Speed difference is Vc−Vd. The angle output repeats the entered deployment angle.
All clean and deployed quantities must come from comparable definitions. There is no equation linking the entered speeds to the lift coefficients, and no calculation of stall speed, lift force or actuator load.
Example comparison
Entering CLc=1.4 and CLd=2.4 gives ΔCLmax=1.0 and a relative increase of about 71.4%. Entering 170 kt and 140 kt gives a 30 kt difference. These independent inputs do not establish the performance of an aircraft.
The angle input controls the maximum rotation of the drawn panel. Its displayed cycle repeats every eight seconds. The aerodynamic inputs do not change that motion.
Support geometry and model limits
NASA CR-4746 distinguishes simple Krueger hinge fittings from variable-camber four-bar arrangements. The cutaway shows a rigid panel and curved hinge fitting turning together about a fixed internal bearing. The fitting connects the bearing to the panel, and an illustrative rotary drive acts at the hinge.
There is no folding bullnose, panel-flexing linkage, collision check, force analysis or aerodynamic calculation. The rotary drive identifies the actuation point; its size and torque are not calculated.
Frequently asked questions
Is this a particular aircraft’s flap mechanism?
No. The drawing is conceptual and does not reproduce a complete aircraft installation.
Does deployment angle calculate maximum lift coefficient?
No. The two lift coefficients are independent inputs.
Does the speed difference predict a stall-speed reduction?
No. It is only the difference between two entered speeds.
Does the internal hinge fitting move correctly in the drawing?
Yes. The curved fitting rotates with the panel about the fixed internal hinge. Their relative position stays constant throughout deployment; dimensions and attachments are illustrative.
Technical reference
NASA CR-4746, High-Lift Systems on Commercial Subsonic Airliners, describes leading-edge devices and distinguishes simple, folding and variable-camber Krueger mechanisms.
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