My First Annual- What Can I Do To Help??

[Ned Gravel]

6 hours ago, Greg Ellis said:

This thread reminds me of why my A&P/IA charges what he does and why I pay it without question.  There is so much that goes into an annual being done properly.

+1.  And he knows who he is.

[0TreeLemur]

Regarding our investigation on why the right main landing gear door hangs about 1/2" open when the gear are raised, we dug into this deeply today and I have more to report.   No gear rigging done today.   None of the push rods seem bent.  

We performed the preloads and they were within spec.  Down and locked seems ok.   No unusual motion noted in the gear mechanism when in the down position.

After checking the preloads, we removed the wheels from the main gear to do the brakes, and my A&P had me raise the gear so he could examine them in detail.   That was different. 

By comparing the left and right main gear mechanisms, one key difference was observed.   Pushing up or pulling down on the right main gear leg caused flexure in the push rod as shown in the photo, but not in the left main.   It seems that the retraction truss hinge  denoted with the red arrow in the upper-left is worn, which is allowing the force on the main to produce some slight lessening of the stress in that push rod when it is in the up position.   Did not seem to happen in the down position, I suppose because of the preload stress disconnecting loads on the gear from the push rod.

That explains why the gear door is not touching the underside of the wing despite being adjusted fully "closed".   The wear in the retraction truss pivot point is allowing the right main to "sag" a bit when fully raised.    Anybody dealt with this one?   It seems like I need to order one of those parts (where hand is pointing)- retraction truss hinge or pivot??

Figure 1.   Right main landing gear in up position with tire off.

[Andy95W]

Fred, this isn't uncommon.  You'll most likely need some new bushings and hardware.  Your A&P will be able to figure out exactly which ones.

LASAR is probably the best place to get the parts.  There is a guy there, Dan, who's been doing it for a LONG time.  He probably knows the part numbers by heart.  LASAR makes their own PMA'ed bushings that are harder than the originals.  Also, just in case any of your trusses or fixtures are worn, they have PMA'ed oversized bushings.  

Also, if you have enough forward/aft slop in the links, a thin AN960 L washer of the appropriate size can help as a shim, where needed.

[Andy95W]

If you end up having to remove the actual landing gear truss itself, you don't really need the spring tool shown in the maintenance manual.  A neat trick is to load up the spring with cheap washers that are 1" wide or so.  That will hold the spring in the extended position so you can get it unhooked from the gear.  Quarters (25 cent pieces) work also but you'll probably need $7-8 dollars worth.

[Shadrach]

13 hours ago, Fred_2O said:

Regarding our investigation on why the right main landing gear door hangs about 1/2" open when the gear are raised, we dug into this deeply today and I have more to report.   No gear rigging done today.   None of the push rods seem bent.  

We performed the preloads and they were within spec.  Down and locked seems ok.   No unusual motion noted in the gear mechanism when in the down position.

After checking the preloads, we removed the wheels from the main gear to do the brakes, and my A&P had me raise the gear so he could examine them in detail.   That was different. 

By comparing the left and right main gear mechanisms, one key difference was observed.   Pushing up or pulling down on the right main gear leg caused flexure in the push rod as shown in the photo, but not in the left main.   It seems that the retraction truss hinge  denoted with the red arrow in the upper-left is worn, which is allowing the force on the main to produce some slight lessening of the stress in that push rod when it is in the up position.   Did not seem to happen in the down position, I suppose because of the preload stress disconnecting loads on the gear from the push rod.

That explains why the gear door is not touching the underside of the wing despite being adjusted fully "closed".   The wear in the retraction truss pivot point is allowing the right main to "sag" a bit when fully raised.    Anybody dealt with this one?   It seems like I need to order one of those parts (where hand is pointing)- retraction truss hinge or pivot??

Figure 1.   Right main landing gear in up position with tire off.

I'll also add that that is an area that is sometimes neglected when it comes to grease.  I flew in a C model once that had a definite "clunk" in the gear going over bumps.  The bush was dry. Fully lubricating it corrected the issue.  Also, the stuck heim joints on the gear doors can prevent the gear from fully seating against the wing.

[Hank]

Every annual I grease the gear (8 fittings per main leg, 11 on the nose). Once the IA has done his thing and it's time to put back together, I start at the nose and spray Tri Flow on everything that moves and doesn't take grease. Then put the belly on to catch the drips. Repeat for the wings, but I spray behind each panel.just before screwing it back on. Same for tail, one panel at a time.

[0TreeLemur]

21 hours ago, Andy95W said:

If you end up having to remove the actual landing gear truss itself, you don't really need the spring tool shown in the maintenance manual.  A neat trick is to load up the spring with cheap washers that are 1" wide or so.  That will hold the spring in the extended position so you can get it unhooked from the gear.  Quarters (25 cent pieces) work also but you'll probably need $7-8 dollars worth.

@Andy95W, let met get this straight- you insert washers into the coils on the spring so it can't collapse when you unload it?   Must not have that many coils?   How do you hold them in place before you unload the spring?   Tape?  Clever though!  Thanks.

[carusoam]

Classic advice for stretching a tightly wound spring... filling it full of quarters will extend it evenly along its length... friction keeps the coins in place... the thickness of the coin defines how much the spring will be elongated...

And when it extends after being connected at both ends...  you get the casino sound of coins falling out of a machine...  

PP thoughts only, not a mechanic...

Best regards,

-a-

[0TreeLemur]

Today, minor adjustment to right main gear door.  Raised gear with a/c on jacks and the gear door touches underside of wing on the wing-tip end and is about 1/8" shy of touching the wing on the belly end.

Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?

 

[carusoam]

See the accompanying thread...  Part deux, by @Marauder...

There May be some shared experience...

Best regards,

-a-

 

[Marauder]

Today, minor adjustment to right main gear door.  Raised gear with a/c on jacks and the gear door touches underside of wing on the wing-tip end and is about 1/8" shy of touching the wing on the belly end.
Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?
 

Run Fred Run!


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[Atalla]

I didn't see any mention of EZ-Grip for stripped screws.  Good stuff: https://www.amazon.com/Aircraft-Screw-fastener-Removal-Friction-Drops/dp/B00BFEJY5W/ref=sr_1_3?s=industrial&ie=UTF8&qid=1543761765&sr=1-3&keywords=ez+grip

[Guest]

20 hours ago, Fred_2O said:

Today, minor adjustment to right main gear door.  Raised gear with a/c on jacks and the gear door touches underside of wing on the wing-tip end and is about 1/8" shy of touching the wing on the belly end.

Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?

 

Based on issues that others have had, I would not open the system other than fill the reservoir and pump fluid down and out the bleeder screws at the caliper.  Pump until all of the oil congealed fluid is removed.

Clarence

Edited December 3, 2018 by M20Doc

[0TreeLemur]

21 hours ago, M20Doc said:

Based on issues that others have had, I would not open the system other than fill the reservoir and pump fluid down and out the bleeder screws at the caliper.  Pump until all of the oil congealed fluid is removed.

Clarence

Hi Clarence,

I'm pretty sure that this is what my A&P plans to do.  I haven't looked yet, but I assume there is a bleed on the flap actuator cylinder?

We will get back on this Wednesday.

Thanks for your advice,

Fred

[0TreeLemur]

23 hours ago, Atalla said:

I didn't see any mention of EZ-Grip for stripped screws.  Good stuff: https://www.amazon.com/Aircraft-Screw-fastener-Removal-Friction-Drops/dp/B00BFEJY5W/ref=sr_1_3?s=industrial&ie=UTF8&qid=1543761765&sr=1-3&keywords=ez+grip

We've been using these.  https://toolguyd.com/stanley-screwdrivers-diamond-coated-tips/

They increase grip and reduce the likelihood of head damage.

[Bill G]

On 12/1/2018 at 9:33 PM, Fred_2O said:

Today, minor adjustment to right main gear door.  Raised gear with a/c on jacks and the gear door touches underside of wing on the wing-tip end and is about 1/8" shy of touching the wing on the belly end.

Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?

 

Fred - My mechanic found the same hanging gear door problem on my first annual a couple of months ago, but didn't believe it was cause for alarm and didn't fix it.  I'm wondering how this affects my cruise speed... or if this could result in some other problem.   Any ideas?

Bill 

[Marauder]

On 12/1/2018 at 10:33 PM, Fred_2O said:

Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?

 

Fred - I am not sure about your philosophy about proactive maintenance. I have always accepted any suggestions from the shops at the annual about being proactive on maintenance. That said, until this past annual, no one said anything about the brake system other than periodically a "time to change the pads" comment. Nothing about brake lines, parking brake, etc. was ever said until this past annual. I decided to hold off since I already had a hefty annual bill and the brakes were not showing any signs of issues. Sure enough, I get a pedal softening and I decided to tackle the brake lines (which turned out to be original) and the parking brake that was leaking and the rubber hose swollen quite a bit.

In the process of doing this, I noticed that many of the O rings used in the parking brake and master cylinders have a useful service life stamped on them. I wonder how many times those dates are adhered to?

[0TreeLemur]

2 hours ago, Marauder said:

Fred - I am not sure about your philosophy about proactive maintenance. I have always accepted any suggestions from the shops at the annual about being proactive on maintenance. That said, until this past annual, no one said anything about the brake system other than periodically a "time to change the pads" comment. Nothing about brake lines, parking brake, etc. was ever said until this past annual. I decided to hold off since I already had a hefty annual bill and the brakes were not showing any signs of issues. Sure enough, I get a pedal softening and I decided to tackle the brake lines (which turned out to be original) and the parking brake that was leaking and the rubber hose swollen quite a bit.

In the process of doing this, I noticed that many of the O rings used in the parking brake and master cylinders have a useful service life stamped on them. I wonder how many times those dates are adhered to?

Last week my 70 year-old A&P laughed when I pulled out the Mooney 100h/annual checklist.   He said "If we do all that stuff it will take a month and cost $5 to $10 thousand".   His philosophy is "Lets make sure she's airworthy, the AD's are met, improve what we can, and note the repairs that need to be done in the next year".   That is his philosophy.  He used to work for a Mooney service center.

He rebuilt the brake cylinders by replacing the one o-ring, which had mostly turned from round to square, because he noticed a bit of brake fluid leaking out.  That is when he noticed that the hydraulic/brake fluid was much more viscous than when new.  

His "to-do" list of repairs needed in the next year includes replacing 3 rod ends on the rudder push rod- these are three that are actually in the tail, not the empannage, and replace the bushing and bolt on the right main retraction truss pivot. 

Next annual I plan to replace all the brake/hydraulic hoses, which appear to be very old, if not original equipment.

[0TreeLemur]

3 hours ago, Bill G said:

Fred - My mechanic found the same hanging gear door problem on my first annual a couple of months ago, but didn't believe it was cause for alarm and didn't fix it.  I'm wondering how this affects my cruise speed... or if this could result in some other problem.   Any ideas?

Bill 

Hi Bill,

It is probably not a big deal, but I'm not 100% positive.  I have noticed this annual that when the gear are up in my '67 C, the tire is not exactly flush with the belly.   Rather. the brake disk and aft portion of the tire hang out into the slipstream, which probably pushes the gear up into the wheel well and helps to close the gear door gap in flight.  That's one theory.  If true, then the gap is not an issue.  My A&P wanted to close that gap by adjusting the gear door.  It only took two turns of the front turnbuckle to mostly eliminate the 1/2" gap.  If true, then this also suggest very little effect on cruising speed.   My cruising true air speed at mid-altitudes (5 - 8kft)  24square is about 143 kt, which by all indications I've seen is ballpark.   YMMV.   IANA&P.

Good luck,

Fred

[Bill G]

On 12/1/2018 at 9:33 PM, Fred_2O said:

Today, minor adjustment to right main gear door.  Raised gear with a/c on jacks and the gear door touches underside of wing on the wing-tip end and is about 1/8" shy of touching the wing on the belly end.

Next task is to try and completely flush and replace the hydraulic fluid, which has transmogrified into a substance with the consistency of honey.  Maybe it is time to overhaul the parking brake while we're at it?

 

Fred - My mechanic found the same hanging gear door problem on my first annual a couple of months ago, but didn't believe it was cause for alarm and didn't fix it.  I'm wondering how this affects my cruise speed... or if this could result in some other problem.   Any ideas?

Bill 

[Bill G]

Thanks Fred -  My cruise is about the same, but would like to squeeze out a little more. Seems to me that the gear door hanging down a 1/4 inch would be a lot of drag. Maybe not, but I printed out your pictures and comments and will be taking to my next annual.  Thanks!  Bill   

[Hank]

For cruise speed, check these:  air leaks through the doghouse (cracks, gaps, missing screws); the carb heat flapper and hose.

I rebuilt both of these, and now my C cruises at 147 KTAS from 7500-9500 msl.  

[0TreeLemur]

3 hours ago, Hank said:

For cruise speed, check these:  air leaks through the doghouse (cracks, gaps, missing screws); the carb heat flapper and hose.

I rebuilt both of these, and now my C cruises at 147 KTAS from 7500-9500 msl.  

That's cool.  What other speed mods do you have Hank?   I suppose you have the cowl intake mod that eliminates the drag-inducing 'open mouth to nowhere' below the prop.  What else?  201 windshield?   We re-assembled the doghouse very carefully sealing up any gaps and holes last year.   Also the carb heat box and hose are in good shape.  My Mooney looks like it should cruise at 160, but 143 is all I get

[Hank]

5 minutes ago, Fred_2O said:

That's cool.  What other speed mods do you have Hank?   I suppose you have the cowl intake mod that eliminates the drag-inducing 'open mouth to nowhere' below the prop.  What else?  201 windshield?   We re-assembled the doghouse very carefully sealing up any gaps and holes last year.   Also the carb heat box and hose are in good shape.  My Mooney looks like it should cruise at 160, but 143 is all I get

I do have the guppy mouth closure and 201 windshield, but that's it. I also have a 3-blade Hartzell prop, which "everyone" says cost 3-5 knots in cruise, so I figure they cancel each other out. After redoing the carb heat box after it failed to Full Open and replacing the holed muffler, my indicated speeds increased by 10 mph.    

[0TreeLemur]

41 minutes ago, Hank said:

I do have the guppy mouth closure and 201 windshield, but that's it. I also have a 3-blade Hartzell prop, which "everyone" says cost 3-5 knots in cruise, so I figure they cancel each other out. After redoing the carb heat box after it failed to Full Open and replacing the holed muffler, my indicated speeds increased by 10 mph.    

One of these day's we'll have to have a race around Alabama.