Legal to Fly a J-Model without Wheel Covers?

[N201MKTurbo]

For a friend with a C180, he had Alaska Bush Wheels. I just listed the weight, arm and moment at the bottom of the W&B for the regular wheels and for the big wheels.

[MB65E]

5 hours ago, MooneyAcolyte said:

I'm in the process of making replacement covers from carbon fibre as owner-produced parts as per FAA (see FAR 21.9 (a)(5)) and EASA (CS-STAN for standard changes according to 21.A.307(b)4). I'll report here on my prototypes and whether or not I get them approved by my A&P/IA (due end of February '25). Perhaps we can make a co-op effort to get enough wheel covers for everyone. I know Lasar is selling them for 1,4 k$ each here: https://lasar.com/doors/inner-main-gear-door-550060-001?rq=gear door

Be a little more careful, An OPP requires same material choice. I would suggest a “repaired part” with the carbon fiber being used. Since it is a minor repair by definition, no 337 required. 
-Matt

[MooneyAcolyte]

Be a little more careful, An OPP requires same material choice. I would suggest a “repaired part” with the carbon fiber being used. Since it is a minor repair by definition, no 337 required. 
-Matt

I’ll try the EASA avenue first. Here in Europe, we have the freedom of “standard change” that allows us to make minor changes to certificated, non-complex (Part-M) aircraft.
Any chance you can point me to the applicable FAR on material equivalency, as I seem to be unable to find it?


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[Oscar Avalle]

I was about to ask the same can these inner doors be added to a M20C?

[PT20J]

19 minutes ago, Oscar Avalle said:

I was about to ask the same can these inner doors be added to a M20C?

I don't know what would be required but Don Maxwell told me he put them on some J-bar airplane (maybe an F, don't remember) and the air loads were so great it was really hard to raise the gear.

[EricJ]

45 minutes ago, Oscar Avalle said:

I was about to ask the same can these inner doors be added to a M20C?

One of my hangar neighbors that has an M20A said there was a local with an M20C that put the lower doors on.   They did the engineering to resize the helper springs due to the increases aero load and had new springs wound.   Apparently that worked well.   I've no idea where that airplane is now, though, as I don't think it's around here any more.

Might make it exciting to take the doors back off again, too. 

In any case, like anything it can be done, but it isn't as straightforward as just attaching them to the gear.

[PT20J]

56 minutes ago, EricJ said:

One of my hangar neighbors that has an M20A said there was a local with an M20C that put the lower doors on.   They did the engineering to resize the helper springs due to the increases aero load and had new springs wound.   Apparently that worked well.   I've no idea where that airplane is now, though, as I don't think it's around here any more.

Might make it exciting to take the doors back off again, too. 

In any case, like anything it can be done, but it isn't as straightforward as just attaching them to the gear.

But, it sounds like he did it correctly. Not sure it's worth the work for 5 kts, but what the heck.

[EricJ]

16 hours ago, PT20J said:

But, it sounds like he did it correctly. Not sure it's worth the work for 5 kts, but what the heck.

I'm not sure it's worth 5 kts.   

[Ibra]

23 hours ago, MooneyAcolyte said:

Any chance you can point me to the applicable FAR on material equivalency, as I seem to be unable to find it?

There is no equivalent for EASA CS-STAN ("standard change") in US rules, however, the FAA has two routes for "minor change" and "major change", these are done with logbook signature and 337 forms (with an IA) 

You can argue that FAA "minor change" route is equivalent to EASA "standard change" route (CS-STAN), however, these things gets highly mixed up and there is no one-to-one (in EASA, you can use some ASTM UL fuels with CS-STAN as long as they are approved for engine, all you need is logbook signature while in FAA rules this require an airframe STC)

For major changes, if you see them in a given N registration, you can request all 337s in CD-ROM from FAA for that registration (these should include all 337s major mods that are done via field approvals as well as STCs, even those associated with serial numbers) 

In EASA land, you can look at similar "well trodden" paths...

https://www.easa.europa.eu/download/stc/MajCh-Digital-Certificate-Publication-Report.pdf

 

 

 

Edited December 22, 2024 by Ibra

[Ibra]

On the topic, how does one go about getting these approved? something looks fishy !

Edited December 22, 2024 by Ibra

[MooneyAcolyte]

I have started making the moulds.

[N201MKTurbo]

40 minutes ago, MooneyAcolyte said:

I have started making the moulds.

The Mooney part is made from two pieces of aluminum sheet metal riveted together. Are you going to make a mould for each piece and then bond them together, or are you planning on making one thick piece of fiberglass? That will be quite a bit heavier if you do that.

[MooneyAcolyte]

13 minutes ago, N201MKTurbo said:

The Mooney part is made from two pieces of aluminum sheet metal riveted together. Are you going to make a mould for each piece and then bond them together, or are you planning on making one thick piece of fiberglass? That will be quite a bit heavier if you do that.

Making two a side is exactly the plan. I plan 4 carbon fibre layers for each "side" to get the thickness right. Then, I trim the inside and bond it  - for a total of 8 layers - at exactly the same surfaces as where the original part is riveted. I still have to decide on the vacuum bagging approach (low or high vacuum). In my experience, 70 - 80% of the work is in making the moulds. Since I have to make 4 (inside, outside times left and right), that mike take a while. I have experimented with a prototype (car fuel port lid) that was very similar and that worked splendidly.

 

 I'll keep you posted. 

Edited January 6 by MooneyAcolyte
correction

[MooneyAcolyte]

First gel coat went on the starboard cover to make the mould surface.

Edited January 8 by MooneyAcolyte
spelling

[MooneyAcolyte]

The two moulds for the starboard side are done, but need cleaning and finishing. Next up: moulds for the port side.

 

 

[Slick Nick]

Hot damn those are gonna be sweet!

[MooneyAcolyte]

Hot damn those are gonna be sweet!

Thanks, I‘m doing my best. Will keep everyone posted.


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[MooneyAcolyte]

The first part (top) came out of the mould (bottom) - not good enough. Have to move to resin infusion. 

[Slick Nick]

What’s wrong with it? Looks pretty decent. 

[MooneyAcolyte]

What’s wrong with it? Looks pretty decent. 

Thanks. There are some “dry spots” where the resin didn’t make it. That’s either a consequence of the low temperature in my workshop (-5degC), or of the wet lay-up with hoover vacuum process I used. I presume the latter, so next I’ll try resin infusion under full vacuum.
Now that you mentioned it, I might try salvaging the part by flattening down the dry spots and adding resin post-factum. It’s not a structural part after all.


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[Slick Nick]

I like your idea. I'd salvage them! Consider them a "prototype" anyways, the first ones are never perfect!

[EricJ]

11 hours ago, MooneyAcolyte said:

Now that you mentioned it, I might try salvaging the part by flattening down the dry spots and adding resin post-factum. It’s not a structural part after all.

If nothing else they'll be good dimensional parts to check fitment, etc.

I was also going to suggest that once you get where you want to go with these, a perhaps more desirable part would be the one-piece doors that eliminate the need for the trailing fairing.   Since the fairings are also maintenance items, that would provide not only a little more aerodynamic solution plus a reduction in parts count and maintenance.   I'd buy a set a of those.

 

[Yetti]

On 12/21/2024 at 11:46 AM, PT20J said:

When I flew Beavers part 135 we often removed seats to convert from carrying passengers to carrying cargo (usually fish boxes, this being in Alaska). We carried W&B forms for each configuration so it was easy to calculate W&B which we were required to do before each flight.

I don't have a separate W&B sheet for the Mooney for when I fold down the back seats, because I'm only removing cushions. But the rear cushions for my airplane weigh 22.4 lbs., so it is important to include them in any W&B calculations if you are anywhere near limits.

 

But it begs the question if the rear passengers recline their seats should you move them to the baggage compartment station.

[MooneyAcolyte]

If nothing else they'll be good dimensional parts to check fitment, etc.
I was also going to suggest that once you get where you want to go with these, a perhaps more desirable part would be the one-piece doors that eliminate the need for the trailing fairing.   Since the fairings are also maintenance items, that would provide not only a little more aerodynamic solution plus a reduction in parts count and maintenance.   I'd buy a set a of those.
 

Good point. Version 1.0 (two glued parts) will certainly as close as possible to the original, except for the material. For a one-piece some design work and stiffness calculations will be needed. I agree that it might be easier to produce and maintain.


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[MooneyAcolyte]

The resin infusion method is MUCH Better. I get a part (inner shell port) that is "good enough". I'm about 80% there quality-wise, so I will continue to try to improve. Four mistakes were made: 1.) A small leak in the vacuum bag went undetected, the peel ply had wrinkles, the first carbon layer was inconsistently glued down on the mould, loose fibres were left below the first layer. 

Next up: outer shell port - with lessons learned.

 

 

Edited February 15 by MooneyAcolyte