Hello all, as I was doing a service bulletin/letter scrub on my new to me 1998 M7-235C I discovered that one of the easier service letters had not been complied with. SL-61 mandates the replacement of the elastic stop nuts with castellated nuts with cotter pins.

I ordered the hardware from Maule but it appears the bolts are too short to get the nut on far enough to get enough of the hole to appear for the cotter pin. There are three washers in each door hinge and I did try just leaving the one between the two hinge pieces but still no luck.

I’ve worked on cars and boats my whole life so it seems to me like I just need longer bolts. Before I color outside the lines I just thought I’d ask the experts if anyone has done this compliance action and if I am missing something.

Thank you
Tim

If you aren’t already, try “Lâ€￾ washers (these are half the thickness of standard AN washers). If you need to use longer bolts, it’s fine. These planes are hand built, and no two are exactly the same (very much unlike cars). This is why all good shops keep a large selection of AN hardware on hand; most every part install on a light plane is custom to some degree.

I also just went through this. The Service Letter doesn't specify using any washers (that I remember seeing) but my doors all had multiple washers. I ended up getting a few bolts to fit with thin washers and the rest had to be longer.

I like to use a thin (“Lâ€￾) washer between the hinge halves as a thrust bearing of sorts. Prevents wear of the hinge parts themselves.

Thanks ya'll. Hardware on order.

I realize the factory had to do this to cover their rears since no one could prove what happened in the accident but I hate snagging myself on the cotter pins. I do look at things like that from time to time and a properly installed elastic stop nut should not back off just from opening the door. Thinking about backing out that service letter.

This got my curiosity up and I compared the SL to the print. SL calls for AN3-3 bolts and the print for the front doors (1177F) calls for AN3-5. I brought this to David Maule's (He who knows all) attention and he said both were wrong. It should be AN3-4's with 2 L washers, one between the hinges and one under the nut. I'll see what this will take to get this corrected.

Nice sleuthing, Duane!

Always nice when someone cares enough to dig deep into the little details to find the most correct answer.

Too funny, ordered the -5 bolts based on my caliper measurements. Dang, guess I’ll wait and see what Duane finds out before ordering the -4s!

Love this site! Truly love the knowledge and selflessness of all I have received advice from. I wish my peers at the airline I work for showed half the consideration and professionalism.

Too funny, ordered the -5 bolts based on my caliper measurements. Dang, guess I’ll wait and see what Duane finds out before ordering the -4s!

Love this site! Truly love the knowledge and selflessness of all I have received advice from. I wish my peers at the airline I work for showed half the consideration and professionalism.

I’m going to just act like me and my nylock nuts never saw this thread.

Have to admit I’m a fan of the nylocs too. Especially since I frequently take my doors off and put them back on. Replace them whenever they start to feel the slightest bit too easy to turn, and I’ve never had an issue.

gbarrier wrote:...I hate snagging myself on the cotter pins...

Early on I had a passenger cut their arm on the rear door cotter pin when they were getting out of the front seat. Quickly added extra bandages to the first-aid kit and also try to point it out to new passengers while helping them get in.

I also have several washer at each hinge so will go through my hardware stash and see if I can find a -4 and L washers.

The story I heard, pilot flying a Maule had his door start to come off.
I think it was top hinge bolt.
He grabbed the door to prevent it departing to the horizontal stab or elsewhere and lacerated his arm holding it while getting down and landing.
Stuff that nightmares are made of.
Did a worn out nylock nut come off, worn from multiple door off operations.
Did a loose bolt of 100's of hours finally wear through (seen that).
Was a nylock nut or castellated nut on the bolt and did a cotter pin fall out.
Honest responses next:
Does everyone check the door bolt shanks and nuts on a regular basis ???

True story...
A Maule owner asked me to tune him up on wheels as he had been on floats a lot.
I walked to his airplane and some intuition told me to check the tail strut bolts, the is an SB regarding them.
The airplane had two days earlier come out of an annual from a known shop on Lake Hood.
The bolts looked a bit rusty so i checked a nut....it came off the strut with no resistance and the complete shank was missing rusted away. The bolt head was also rusted in position.
I checked the other and its shank was 60% eaten away.
This plane fresh out of annual was one takeoff away from killing he and I.
What else was NOT checked in the annual inspection.
Probably EVERYTHING.
So, check your door bolts in case no one has.

Good stories, both. And scary...

I have my doors off quite often, so I get a regular look at those bolts and nuts.

I had a similar experience with the tail strut bolts. Was doing an annual on a new customer’s M-5. Found those bolts corroded half way through, and a crack from the inner hole to the outer hole, then another from the outer hole to the outer end of the stub. Same on both sides. Guy was pretty unhappy that I told him I couldn’t pass it that way. People have funny priorities sometimes.