USIC 2013 Operations - LPP processing

From: John Kagan <john_kagan_at_hotmail.com>
Date: Tue, 22 Jan 2013 14:53:35 -0000

There is discussion regarding LPP processing.

The rules say: "21.2.2. The overall length, including the propeller, shall not exceed 20 inches (50.8 centimeters). The length is to be measured by placing the prop blade leading edges against a vertical plane. The rearmost part of the model must not extend beyond a line parallel to the vertical plane and 20 inches from it. "

We did use this method previously. Unfortunately, as with all things rules, "it's not that simple". We taped down a box to provide the vertical surface, and marked a parallel line 20" away. The model was layed down on the table and the prop pushed up against the box, rearmost portion checked against the 20" line. The problem with this method, though, is that any changes in left thrust can render a model illegal. Plus, my prop blades flare and are quite flexible. If the model is layed down under its own weight the blades flare forward considerably. Since the blade flare is dynamic, which state do we need to measure?

I propose the following: a vertical surface, as above; a platform 13" above the table (another box, perhaps) with a gap between its horizontal surface and the vertical surface for the prop to fit it, and a 20" line on the raised platform. This way the prop is not loaded, and it can be rotated into a vertical (or other) position that allows the tailing edge of the stab (or whatever part of the model is most rearward) to be positioned parallel with the 20" line.

This fits the rules (which have an ambiguous aspect that is not readily apparent), more closely than measuring from the front of the prop spar to a single point at the rear of the model.
Received on Tue Jan 22 2013 - 06:53:37 CET