Need LH Main Gear Door

[Charles Schefer]

I am in the middle of a big project doing a complete restoration of the landing gear on my 1968 PA-30 "B" model. 90 hrs ago the 1,000 hr AD was done (77-13-21) but I am re-doing that again along with the side-brace stud (AD 79-01-01 R1). 90hrs ago I had a new Dukes transmission and motor put in, new Webco Teflon push-pull condiuts, and 100% all new gear wiring kits and switches from Matt Kurke at Comanche Gear (who also supplied the Dukes Transmission).

So what am I doing now? I (and my A&P/IA) have dis-assembled every component of the gear down to individual bits and pieces. The gear wells are completely empty and are being stripped / cleaned and refinished in Dupont Imron Epoxy paint that is chemically resistant. All the aluminum gear parts are now with a paint shop for the full strip-etch-alodine-prime-paint process. All the steel parts are going to another facility for cad stripping and cadmium plating (every nut, bolt, washer, spacer... everything).

Anyway as part of this process I discovered my main gear doors are not in the best shape. I bought a brand-new surplus RH Main Gear door from Matt Kurke but I am having difficulty finding a new LH Main Gear door. The one I have is not bad and can be patched in manner that will be aesthetically OK but I wondered if anyone had a LH Main Gear door in new or close to new condition that they would like to sell. If so please let me know.

Thanks,

- Charles

[N3322G]

Charles, google the part number - they are the same as for singles. I had a pair of 250's from eBay stripped and painted and put on the Twin this annual - be prepared for some adjustment. Be sure to keep your hinges - that can help.

[Charles Schefer]

[Charles Schefer]

Pat thank you!!! Brilliant idea. I just found and bought a LH Gear Door on eBay that looks to be in very good condition. I am going to see if they will ship it straight over to the paint shop for me.

Thanks,

- Charles

[N3322G]

Glad to help.

[Charles Schefer]

My excitement over the new door was short lived . I learned from Phillip at Webco that there is in fact a difference in doors between the single-fork and double-fork main landing gear. My 68 PA-30 is of course a single-fork MLG but this door on eBay was from a double-fork PA-24.

Here is a picture of the PA-24 gear door I was going to buy...

PA-24 Gear Do

See where I have added those two red arrows to the picture? Apparently on a double-fork door (as pictured here) the distance between the two arrow-heads is 4". However on the single-fork door the distance is 5". The problem is that if I take that double-fork door and put it on my single-fork plane the door will bolt up but it won't close completely due to interference where the door gets thicker.

The eBay seller was kind enough to refund my purchase and not ship me a door I can't use. Too bad it was a nice looking door. I am back to looking for a new LH door or will just repair the one I have.

- Charles

[Charles Schefer]

By the way Pat - you are right... the part numbers for singles and twins are the same:

LH: 22984-00
RH: 22984-01

AND... there is no mention in the IPC of different types for single or double fork. I asked Phillip about that and he said yes that's what the book says but they discovered there is an actual difference when they started producing the doors aftermarket (which unfortunately they cannot currently do but that's a different topic). As I mentioned in my last post - I had the seller measure the one he has and I measured mine and sure enough just what Phillip says they are different.

I am no Comanche expert but I've been told that the singles all had double forks until the 260 which came with a single-fork and therefore a 260 door would work for a single-fork PA-30/39 but a 180 or 250 would not... it would fit but not completely close according to Webco... Unless I suppose it was somehow modified?

- Charles

[N3322G]

Interesting - guess I got lucky.

[Charles Schefer]

[SLIMDREDGER]

At my recent annual with 1000 hr gear inspection due, we switched the single fork gear from our 1967 PA30 parts plane to my 1964 PA30 with dual fork gear. All seems to work properly....but you guys are making me nervous .....I'll have to get my rule out and be sure I have the proper clearance.

Al Powers N88AP

[N3322G]

Al,

Look real closely where the lower door has the swivel point - that is where Clifton found cracks very tiny, very thin cracks. Matt Kurke said it was as much to fix as it would be to replace so I replaced.

The past ICS Treas who bought a twin had a failure in this area a year or so ago and we were close and now Charles - I figure Twin prop wash is harder on gear doors than singles would be.

[Charles Schefer]

Pat I think you are right about the twin prop wash on the doors. I have cracks right where the links connect to the swivel point. I have a brand new RH door thanks to Matt Kurke but I'm still on the hunt for a LH door.

To illustrate what Pat is referring to (Pat correct me if I missed your point) attached is a pic of the inside of a gear door showing a crack at this point. This is not my door but one I saw for sale and the seller confirmed it's cracked at this point...

Cracks from swivel point where link rod connects to inside of door.

Inside of Door.png (179.99 KiB) Viewed 1558 times

My RH door was badly cracked and I didn't even know because it was hidden under a large area washer that was there. That door also had quite a few patches and I'm lucky Matt had a brand new one (surplus Piper stock) which had the 5" measurement I needed. My existing LH door is also cracked there but not badly and the shop who has all my gear parts can patch it so that it's strong and aesthetically good but I'd rather try and find a used "like new" unpatched / uncracked door first if I can.

The paint shop I am using for the aluminum bits (Royal Aircraft at HGR) seems to have done quite a number of Comanches. Their DM seems to have fairly good knowledge of typical Comanche issues and familiarity with the doors, where they tend to crack, etc... He commented that the best way to prevent cracks is to ensure the gear and doors are properly rigged. He said out of rig gear is the most common reason they crack. That made sense to me.

Charles

[N3322G]

Charles,

That is exactly the area - thanks for the great photo and documentation. Our gear and gear doors have always been closely adjusted due to the drag avoidance for air races ... perhaps the mal-adjustments caused cracks but I'm more favorable to the Twin prop wash. Just don't see the patches on single main gear doors we had and see on other twins.

[Charles Schefer]

Pat, my thought is that in an "ideal world" one could adjust the door so it is flush and not putting excess load on the retraction swivel point. Of course I know that's not always reality. I do think you are right about prop wash but here's a thought... the doors when down are angled inward at the front and outward at the back (slightly) so if anything, airflow going straight back should be trying to push the doors in, yet all the doors that I've seen cracked look like the stress has been from the rod pulling on the door (not the airflow pushing the door onto the rod). So, I would still think that the cracks are more due to rig.

I have searched fairly extensively and all the LH doors I've found are in worse shape than my existing door. My existing door has a small crack at he swivel and a small patch at the hinge. I am going to have the paint shop (which also does metal fabrication) repair the door and straighten it so it is strong and looks good. I may have the brand new RH door done the same so that a) it matches the LH and b) it's already reinforced at the common crack points. They are also cutting new wheel well liners for me.

On a related note, I finished removing all the old paint from my gear wells last night and then thoroughly washed them out with Dawn and Water (per paint shop). Tomorrow night we alodine and this Sunday we prime and paint the wells. All the steel parts of the gear (lower drag links, brackets, rods, nuts, bolts, spacers, washers, side brace studs, gear door brackets, push-pull conduit supports, etc...) are in Newport News VA being cad plated and visible brackets (e.g. gear door brackets) will then be powder-coated white on top of the cad (steel only). The aluminum parts (upper drag links, trunnion housings, trunnion mounts, side brace stud housing, etc...) are at the paint shop in Hagerstown, MD being stripped, primed and painted. I figure if we get all the parts back next week it will take is a few weeks to reassemble the gear and re-rig it all. This has been a bigger project than I imagined and has already taken over a month with many late nights but I've learned a lot about the gear. Basically I am doing what Matt Kurke did to his 400 gear and what George Ahlsten did on his PA-30 gear (may thanks to both of them for all the advice and support as well as Cliff Wilewski at Herritage who has taken many calls and answered many emails). I've enjoyed it but it's also caused some restless nights. I'll be happy when it's all done. It's funny, I started off just planning to "clean it up a bit" but as we started taking stuff apart and cataloging it all we just kept going till there was nothing left to remove.... sort of an "accidental restoration".

- Charles

[N3322G]

Even properly adjusted gear doors will get prop wash during pre-flight run-ups, departures and approaches and landings.