Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/378679
36 Vol.3 No.9 / September 2014 HOMEBUILDERS' HOW-TO THE OTHER DAY I received a phone call from a friend with a dinged propeller on his Cessna 182. This article details the pro- cess in repairing such a propeller. Repairs of this type on certifi cated aircraft require the supervision of a mechanic with at least a powerplant rating. However, on experimental ama- teur-built (E-AB) planes, anyone can do the work and log it. The propeller in question had been overhauled not too long ago, and its leading edge was protected with Prop Guard polyurethane tape. Prop Guard went out of production a few years ago but has been brought back by another company. It has an STC; but the FAA has declared that it is a minor alteration since it is not much dif er- ent than a couple of coats of paint. For the industrious, you can buy the components of Prop Guard from 3M and create your own "kit." The tape is used primarily as an anti-erosion coating. Sand and even rain can chew up the leading edge of your prop at a surprisingly rapid rate. The tape is sacrifi cial, eroding in place of the paint or metal. This erosion occurs most at the tip of a blade, so I have found myself replacing the last 4 to 5 inches on my prop on a regular basis. For this reason, I now splice on a 4- to 5-inch piece on the tip end of the prop for easy replacement. Although anti-erosion tape will mitigate the ef ects of a stone hit, it will not eliminate damage to the prop. Such had hap- pened on my friend's C-182. The damage was in the tip section, and it looked like a 3/16-inch bolt had slammed sideways into the leading edge of the prop. The tape was massively torn and required replacement as well. See Figure 1. Before beginning a propeller repair, consult the propeller manufacturer's maintenance manual for your propeller for ac- ceptable repairs. Also check the type certifi cate data sheet for allowable dimensions, particularly if any shortening of the di- ameter is involved. If you cannot fi nd manufacturer's data, then consult Advisory Circular (AC) 43.13-1B, Chapter 8, Section 4, which provides acceptable data for metal propeller repair. Fig- ure 8-24 is perhaps the most useful, particularly for the repair I needed to do, with Repair Example B a near perfect match. See Figure 2. The other critical factor you need to look at is the allowable repair depth limits per Figure 8-27 of the AC. As you go nearer the tip of the prop, you can remove more material. In this case the damage was about 2 inches from the Metal Propeller Repair BY RICHARD KOEHLER, E A A 161427 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Photography by Dick Koehler