It has been a three-year project with AECI, involving myself, Bill Manhein, and Kamran Rouhani, but the FAA-PMA approved reinforced 19/23/23-24/24R/76 Nylon yoke shaft bearings-bushings, and the stainless-steel Sierra main gear down-lock springs, are both finally available!Both of these parts carry an FAA-PMA approval, so they can be installed as alternatives to the Beech parts, with only a logbook entry. No STC paperwork, no FAA Form 337 needed.
YOKE BEARING-BUSHING
The yoke shaft bearing-bushing has a reinforced gust lock pin hole, and a solid (not hollow) body, so it should last indefinitely in normal service (no crashes allowed!). The FAA also issued the paperwork with the 1962-1963 Model 23, Serials M0001-M0554, included on the PMA document. That means that you can use this new heavy-duty bushing to replace the old original round bushing, on these early planes, just by drilling the holes for the two mounting screws.
The yoke bushing is P/N 169-524050; here is the AEC ordering link:
http://www.aec-inc.com/products/cart.pl?IT=169-524050AEC
The Beech price is now $757; the AEC price for the reinforced bearing is $150!
SIERRA MAIN LANDING GEAR DOWN-LOCK SPRINGS
Sierra main gear down-lock (over-center) springs have been a sore subject for years. The Beech originals are Cadmium-plated spring-steel parts. In short, they rust. Many are very badly rusted; this creates a large exposure to sudden failure, due to ‘notch-stress’ induced cracking. Virtually all of the springs have been cleaned and repainted (or just painted over the rust), multiple times. Most owners have no idea how bad their springs really are. The old springs really detract from the gear appearance on a newly-painted plane, as the rust begins to bleed through the new paint.
Availability of new springs has been very ‘spotty’, with large price increases on every new batch offered by Beech. Also keep in mind that the gear pump stops when the last gear leg goes over-center. If the spring breaks, the side brace may fold up if a sudden side load is applied. While the pump will come back on if a brace unfolds, it is unlikely to prevent the gear from collapsing.
These springs have been a concern of mine, on my own plane, for at least ten years. This is despite the fact that my springs are far better than most, due to repetitive cleaning and painting. During that time period most of the available replacements have been used-salvage springs. Most of those have been no better than those already on an owner’s plane. And the price of salvage springs has risen steadily as Beech escalated the price on new ones. I have been trying to help make new springs available before we start experiencing aging-aircraft induced main gear collapses. The cost of this preventive measure is almost insignificant, compared to the high probability of a totaled-salvaged plane if it falls on one wing.
These new AECI springs are a passivated and re-plated aviation grade of stainless steel spring stock. In fact, we only located one USA factory capable of making the needed special form of ‘open-wound’ spring. Barring any eventual loss of tension due to time in service, these springs should have an almost unlimited life span. Not to mention looking ‘too cool’ on a nice plane.
The springs are P/N 169-380043; here is the AEC ordering link:
http://www.aec-inc.com/products/cart.pl?IT=169-380043AEC
The Beech price is now $275 EACH; the AEC price for the ‘lifetime’ stainless steel replacements is only $200 PER PAIR! These do need to be replaced in pairs, to assure balanced operation loading.
Also please note that the lower spring attachment hardware should be replaced at the same time, as the lower eye-bolt is usually as rusted as the old spring itself. I believe that AEC may be assembling some convenience hardware kits for the lower attachment replacement. If they decide against that, I may do so instead. If you need the parts right away, they are not too terribly difficult to find. You need:
2ea AN44-11A eye-bolts
2ea MS20364-516 low height (shear-type) elastic locknuts
2ea AN960-516L thin flat-washers
The Shop Manual contains instructions for disconnecting this heavy-tension spring. Personally, I have found that the easiest way is to remove the top stack tube nut, and allow the lower fork to travel forward (as the stack tube clears the upper housing hole). As a result, this is a great time to replace the Sierra main gear donuts, if not already done. If the donuts are still serviceable, and a clearance gap can be seen on the tube (above the housing), you can probably get away with just changing the eye-bolt and spring, then get the stack tube back into place (weight back on the gear, top washer and nut reinstalled, nut re-tightened to a stack height of about 6.3″). But you’ll need to work fast! If your donuts are pretty new, you’ll have to remove, heat, re-compress, and freeze them, to get the stack tube back into place. If you choose to do the spring replacement in the manner outlined in the Shop Manual, be very careful. These are BIG springs, for an airplane application!