Safe Flight 164 Lift Detector, For AoA/Stall Warning System

The foundation of Safe Flight's stall warning systems is the lift detector. This was the first and still the industry-standard for stall warning in light aircraft. The system consists of a small tab or vane which senses the change of the stagnation point on the wing and an alerting device used for stall warning. The principal of operation is described below: As the aircraft's wing moves through the air, it divides the approaching air mass into two airflows. The center of this flow division is a narrow region of low-pressure known as the stagnation point, and its position on the wing bears a definite and repeatable relationship to Angle of Attack. The stagnation point moves on the wing undersurface as Angle of Attack changes. Decreasing Angle of Attack moves the stagnation point forward; increasing Angle of Attack moves it aft, to a maximum aft position at which stall occurs and the wing loses lift. Safe Flight's lift detector is designed to detect the location of the stagnation point on the wing and relay this information to the pilot to aid him in awareness that he is nearing a stall. The lift detector, when properly installed and adjusted on the wing, senses the location of the stagnation point by means of a flat, spring-loaded vane which protrudes into the airflow on the wing undersurface. Airflow from the stagnation point moves the vane against the internal spring force and displaces the vane relative to the stagnation point position. The location is carefully chosen on the wing so that air which flows aft from the stagnation point position at the approach Angle of Attack deflects the vane aft a specified amount.