Ron Mattson:
I have a 1971 Sierra (MC-22). While it is not a big thing, it is annoying that the door retainer (link or brace) will not hold the door open. I wondered if it was always this way, or whether through wear the stop has worn down. For instance, a Barron has a positive locking retainer, which must be unlatched before you can close the door. Has anyone else had this problem or have a solution? My regular passenger has taken to putting the POH in the door jamb; I would like to stop that without starting WWIII.
Editor:
Most of the 19/23/24 airframes use door brace link PN 169-380032-1 (RH) and 169-380032-2 (LH), to hold the doors open. These have been superseded by the -7 and -8 parts, respectively. The Duchess (76) uses a -21 (RH) and -22 (LH) for the main doors, and the -2 or -8 for the baggage door (as do the 19/23/24 with the left side baggage door). Most of these links are identical except for length and handing.
They don’t appear to go over-center, but they actually do go very slightly over-center, against a stop tab that is on one side of the link. You nudge them out of the over-center position in order to let them fold in half so the door can close. They are frequently damaged by people who try to close the door without properly unlocking them. They also develop wear at the mount holes and pivots, and it doesn’t take much wear for the over-center function to stop working properly.
Here is a little-known fact. These links are designed to have a bushing in the mount holes, PN 169-420010-85. Almost none of them do. The bushings are very small; they typically drop out the first time the screw is removed, are not noticed, and are never replaced. Of course, RAPID’s $14 price is no help at all. It is possible that the latest link part revisions have eliminated the bushing, but I doubt it. One purpose of the bushing is to enable the mount screw to be tightened down against the bushing. The other is to provide a larger wear surface. This lets the screw stay tight while the link pivots around the bushing, rather than the screw. If your links are sloppy around the screws, and you can’t keep the screws tight, my bet is that your bushings are missing.
If you can live with a minor hardware revision on the door links, and especially if the holes are all worn out in your links (with missing bushings), here is a suggestion (previously published, and already on BAC). Use a large countersink cutter to make a neat, smooth bevel on the outside surface of the link hole (the side the screw enters, with the ridge around it). The bevel doesn’t need to go through. You just need enough to let a stainless steel flush trim washer fit in the hole so that it bottoms out on the anchor nut. Then use a mating flat-head structural stainless-steel screw, with a dab of Loctite on the threads. This combination, if installed so that all the parts clear when folded, will solve the problem. The screw stays tight, and the pivot point becomes the washer against the link hole, where a dab of lube can be applied. You can replace the washer if wear occurs, but it is unlikely to be needed. This fix has the added advantage of allowing you to make the pivot point a bit snug, so that the door doesn’t flop around so readily. The stock bushings are much too loose after only a few hundred hours of usage; sometimes even when everything is brand new.
Be very happy that you do not have the door latch mechanism (and hinge) that is used in the Bonanza and Baron!