ShopTalk – November 2020

In this month's ShopTalk, we will update the reader on the early (pre-1975) cabin door handle problems and a repair that is available from Mooney, so you will not be locked in your plane.

If one owns or flies a pre-1975 Mooney for any length of time, they learn to carry vice-grips in the cabin with them. This tool is a must to avoid the following embarrassment: You land at your destination and park, shutting down the engine and master switch, pleased with your expertise during the flight, and getting to the FBO restroom before you burst your bladder. You gather what you need, scoot to the right seat to open the cabin door only to have the door handle turn effortlessly; the door remains latched. The roll-pin connecting the handle to the opening mechanism has sheared.

Now you are yelling through the storm window trying to get someone’s attention so they can open the cabin door from the outside and let you out. Imagine if you landed safely but with smoke in the cabin and can’t get out. Here we are talking about life or death, all because of a 30-cent roll-pin.

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Fortunately, Mooney recognized this problem in 1975 and changed the way their door handle is attached to the opening mechanism. Mooney owners that have the roll-pin type door handle can upgrade to the latest style door handle by having your favorite A&P mechanic install the Mooney SI (Service Instruction) M20-39 kit. This kit with instructions will require some minor TIG welding to be done, but other than that the kit is pretty straightforward. This kit is not cheap at over 500 bucks but could save your life one day (or keep you from peeing your pants).

Figure 1A, from the Mooney M20J parts manual, shows the roll-pin type door handle (item 31) that should be replaced. Figure 1B, item 21 is the newer style, lever-type door handle.The Mooney SI M20-39 kit includes a four-page manual with the instructions necessary to perform the upgrade. Figure 2 excerpts page 3 of the manual showing the parts detail and page 4 shows the proper offset angles.. Following the directions in the manual, index the block for proper angle and TIG weld it in place. Reference FAA Advisory Circular 43.13-1B - Chapter 4 Metal Structure, Welding and Brazing. Figure 3 shows the bellcrank with the new attach block in place.

You will next need to grind down any high spots from the TIG weld so the modified crank can fit through the escutcheon – cover plate (item 17, Figure 1B). This cover is what holds the door crank in the proper position for operation. It's always a good idea to put a little grease on the shaft of the modified crank when reassembling the cover plate onto the door over the modified crank.

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Looking at the other photos in this article one can see the finished part coming together. Carefully study the M20-39 manual. You want the offset angle correct before the welding. Don't forget the placard that shows the door handle locked position. This is a required item to be installed on your door (Figure 4).

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As our Mooney fleet ages, one will find that the roll-pin that holds the old-style door handle on will be loose and sloppy as to its fit in the handle and crank. This is the first clue you will need to upgrade your door handle crank system to the latest style. A logbook entry in the airframe log by an FAA airframe certified mechanic is all that is needed to return the aircraft to service.

If you have questions about this or any other ShopTalk article, please e-mail me (see below) or call me at my aircraft repair shop, 307-789-6866. All ShopTalk articles can be read here at www.knr‑inc.com. Until next time, enjoy flying your Mooney.