The Aviation Consumer

October 1989

Huntington LRI, Revisited


EXCERPTED

A marvelous way to nail down a precision approach.

We've been using a Huntington Lift Reserve Indicator in the company Mooney for some five years now and, ...we wouldn't want to be without it. It has proved itself to be a much more valuable resource in slow-speed flight than the airspeed indicator and the seat of our pants...

...once an LRI is installed and calibrated properly on any airplane, it will work unerringly, unceasingly. There certainly isn't much to break; the system is quite simple.

The major components are an anodized aluminum mast, which is installed on an inspection plate below the wing or nose, and a display gauge, which includes a 2.75-inch-round indicator inside a three-inch-square housing that's bolted into or atop the instrument panel. The mast and gauge are connected with two 1/8-inch nylon tubes...

The main thing is to stay out of the red arc, because that's where the airplane starts mushing (some lift is being produced, but not enough to sustain level flight)....

...we've used the LRI mostly to stay out of trouble while maneuvering in slow, distracting patterns and to help us get the slippery Mooney down without thumping or floating. The drill on final is to keep the LRI needle at the juncture of the white and blue arcs. Then as you approach the runway, trim and adjust power during flare to position it at the ...center of the white arc. The result invariably is a nice soft touchdown and a short roll-out. (The [green] arc, by the way is Fat City. Here the airplane has bags of lift.)

Unlike an airspeed indicator, which borders on nervous breakdown at slow speeds in rough air, the LRI provides a nearly instant readout of lift margin...regardless of how smooth or bumpy the air is. And it matters not how much power you are carrying, where you have the gear and flaps...Keep out of the red arc and you're okay...

One pilot who seems to have a very good intuitive grasp on how the LRI works is Dr. Kenneth Wolf, safety director for the Aerostar Owners Assn., who installed one two years ago and has become quite an advocate. "It's an incredibly valuable instrument," he told us. "I can't understand why anyone would fly an Aerostar without one." He noted two incidents in which the LRI indicated he was losing too much lift. One was during a landing on a perception-tricking snow-covered runway. The other occurred when he had to reduce power on a sick engine after committed to a takeoff. "On circling approaches, especially, I watch that thing like crazy," he added.

Though it isn't STC'd, field approval via form 337 is possible...A field approval involves the determination that the LRI isn't interfering with anything else in the plane, a change of weight and balance data (though the system weighs a mere two pounds) and a requirement for a placard reading "Not to be used as a primary instrument."