|The LIFT MONITOR
consists of a differential air pressure gauge,
under-wing probe and mount assembly, and durable polyurethane
tubing connecting the
two. The system is entirely independent from any other
aircraft system or component.
The gauge compares the air pressure sensed from two ports on the probe which are arranged at a 45° angle from each other. Air pressure sensed at the port on the beveled (leading) edge of the probe drives the gauge toward the green arc. Air pressure sensed by the port near the bottom corner of the probe drives the gauge downwards toward the red arc.
As angle of attack is increased, air pressure at the leading edge port is reduced while air pressure at the bottom port increases, moving the gauge needle toward the red arc.
The probe comes pre-assembled to the mount at the recommended starting angle which has the long axis of the probe parallel with the rear angled edge of the mount. The probe angle is easily adjusted using an Allen wrench. Star washers installed between the inner faces of the probe mount legs and the sides of the probe ensure secure positioning when the bolt is tightened. Placing a mark on the probe along a trailing edge of the mount leg will serve as a pre-flight check that the probe angle has not been moved.
The gauge depicts three colored segments signifying (1) ample lift available for flight (the green arc), (2) lift insufficient to sustain altitude at the current power setting and pitch angle (red arc), and (3) moderate lift in the white area in between where monitoring is advised.
The system is calibrated using a simple in-flight procedure with the objective of adjusting the probe angle such that the gauge needle, when at the junction between red and white arcs, indicates a comfortable but marginal amount of lift available for any flight condition. Stall will occur somewhere within the red arc, to be determined by experimentation.
The amount of lift available at this setting is determined by the pilot/owner at a level he or she is comfortable with. As examples, the probe can be set to reflect the pilot's observed maximum attainable 100 foot-per-minute rate of climb down to just barely being able to sustain altitude at any given power setting. It is recommended that the probe initially be calibrated conservatively (some positive rate of climb when the gauge needle falls to the junction between red and white arcs). Once the pilot gets the feel of the aircraft at a variety of speeds and pitch angles at this gauge position, he or she may adjust the probe so that this gauge position reflects a lesseer or no margin of lift available with increased pitch or decreased airspeed.
The overall objective is to instill in the pilot confidence in the aircraft's performance at critical angles of attack and thus "readjust" his or her "seat of the pants" feel for the airplane. The gauge is not intended to be used as a primary flight instrument or stall warning indicator. Once you get the feel for what it indicates as calibrated in your particular aircraft, a quick glance at the gauge will suffice to monitor your available lift situation, leaving you to concentrate on what's going on outside the airplane. When encountering a crosswind in the traffic pattern, closer attention to the gauge within the white arc is called for with a tailwind on base leg. You will know just how much bank angle and back pressure you can afford to use turning final before deciding to go around. The same attention is called for when maneuvering in slow flight, as in circling a point for a photo opportunity. The system is also very useful monitoring high-performance climb, particularly in short-field, high density altitude situations.
When introducing a new pilot to the airplane, including transition training upon transfer of the airplane to a new owner, the probe can be reset to a more conservative position until comfort at that level is achieved.
We at LIFT MANAGEMENT, LLC hope you will come to "wear" your airplane as never before, and avoid the danger surrounding loss of lift when you're counting on it. A primary objective has been to offer a system which is so affordable that it would be difficult to rationalize being without it. We hope you will agree.