Lift Reserve Indicator

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Description

The Lift Reserve Indicator has been called variously an angle of attack meter, a lift management system and an airspeed director. The Lift Reserve Indicator integrates both airspeed and angle of attack in a single readout reliably and continuously displaying an aircraft's margin over stall despite the wide range of variables to which an aircraft is subject. For reasons that are embedded in the romance and history of aviation and in the freedom that flying evokes in all of us, exemplified by the expression "right stuff", we find that many pilots argue, and argue with conviction, that airspeed, stall warner, training and instinct are sufficient to meet all conditions from rotation to touchdown. We respond, and NTSB accident statistics support, that miscalculation and loss of control are unfortunately significant contributory factors in many, many aviation accidents. We are all familiar with the term "pilot error". The LRI provides information that could help to eliminate inadvertent stall/spin, density altitude miscalculations, and unrecognized excursions into windshear conditions. The LRI also provides exact control necessary for all STOL conditions. Far more than a 'stall warner', the Lift Reserve Indicator provides constant reference to a base line datum, zero lift reserve , which is established during calibration. The result is safety and control, critical during slow speed flight and during maneuvers at any speed where lift approaches zero. The LRI eliminates guesswork and calculations and is reliable under all conditions of weight, center of gravity, flap position, density altitude, turbulence and angle of bank. The LRI consists of a rectangular, aerodynamically shaped airstream probe and a display gauge. The probe is mounted so that it is positioned in relatively undisturbed air and is effective on all types of General Aviation aircraft including singles, twins, float planes, pushers, ragwings and homebuilts. There are two air pressure ports, each on separate faces of the probe, which are piped to the instrument display. The differential pressure between the two ports yields lift reserve readouts. The LRI display consists of a single arc divided into three sectors. The first is Red; the second is White; the third is Green. The Red sector of the arc indicates that the airplane is no longer generating sufficient lift to sustain level flight. At the top of the Red sector, just below where it meets the White sector, the airplane is sinking. Sink is imperceptible. Deeper into the Red sector the airplane approaches full stall. During takeoff when the LRI needle clears the Red sector and enters the White sector, the airplane has sufficient lift for takeoff. The White sector of the display is the slow speed region of the aircraft. It is the region just above zero lift reserve . During takeoff and climbout this sector of the display indicates

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