Return Spring for M20B Flap Handle

[Joe Hood]

My spring is a little worn. Wondering where I might find a replacement.

[47U]

  On 3/31/2025 at 7:11 PM, Joe Hood said:

Wondering where I might find a replacement.

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Part number 750022.  It looks a lot like the flap return spring on the hydraulic flap models, but that’s pn 750012.

Zero hits on LASAR website.

Zero hits on controller.com.

Not sure how many B models are still around.  Only 239 examples were built?

For best results, I’d call your favorite MSC and see if the factory has any, or can source one.

Barring that, you’re calling all the salvage yards.  Or, find one that’s close on McMaster or the local hardware store and ask your A&P what options are available to make this into a legal part using vintage airplane rules.  What’s the downside if it breaks?  The flaps suddenly retract?  That wouldn’t be good.  A spring with an aviation Mil-Spec would be ideal as it would have some level of certification to a standard.

Then again, your spring might surprise you and have a lot of life left in it.

Replace it with a bungee cord as an owner produced part?  Or, you could thread a bungee cord through the spring and fasten it on both ends, then if the spring does break, the bungee backup would keep the flaps in the notched position.

I’ll stop now.  I don’t think I was very helpful.

Good luck…

[Fly Boomer]

  On 3/31/2025 at 11:44 PM, 47U said:

I’ll stop now.  I don’t think I was very helpful.

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Au contraire, I thought you provided a great response to the OP.

[Joe Hood]

Wow, more than I could ever ask for, thanks!

[MikeOH]

I certainly don't hold myself out as a spring expert, but other than being a little dirty I don't see anything wrong/worn with that spring.  Remove, clean, reinstall.

[N201MKTurbo]

Look here to match it up.

https://www.leespring.com/extension-springs

 

[kerry]

It's the same spring as a wood wing A model if you are looking for a salvage one.

[Utah20Gflyer]

When you say your spring is worn are you taking about the spring not pulling the handle back because it has lost its springyness?  Or are you referring to the cosmetics?  
 

If it’s the springyness it could be the spring is worn out or the whole assembly needs to taken apart, cleaned up, lubed and reassembled.  IE too much resistance in the assembly for the spring to work properly.  
 

If the issue is cosmetic then I would say clean it up and put it back in.  You can’t even see that spring under normal conditions.   I’m  not even sure if I have one or not.  
 

 

[Joe Hood]

If it held in first position, without wind over the flaps, I’d be fine.

[MikeOH]

  On 4/2/2025 at 1:53 AM, Joe Hood said:

If it held in first position, without wind over the flaps, I’d be fine.

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Hmm, it's been awhile since I've flown a 'B' model, but if the flap is drooping when parked, I'm not sure it's the fault of the spring you are showing; I think that one is just to hold the flap handle in its detent.  There may well be a retract spring somewhere in the system.  Take a look at the IPC.

[Joe Hood]

With power or flight, it’ll stay in that detent. 

[MikeOH]

  On 4/2/2025 at 3:20 AM, Joe Hood said:

With power or flight, it’ll stay in that detent. 

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Yeah, that sounds like the spring is weak.  Do you feel much resistance when you pull out on the handle?

[Joe Hood]

There is some resistance and if I place it just so, it'll stay in the detent; but a bumpy taxiway or runway will knock it out.

[47U]

  On 4/3/2025 at 6:15 PM, Joe Hood said:

There is some resistance and if I place it just so, it'll stay in the detent; but a bumpy taxiway or runway will knock it out.

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Interesting.  How long have you had this airplane?  Are you sure it’s the original spring?  It almost looks like the spring is too long.  Can you shim the hole in the flap handle to gain a little more tension?  Is the spring fastened correctly on the forward end?

@Sabremech  does this look correct to you?  

[hammdo]

My B had quite a bit of tension and it took some effort to raise and lower the flap handle. No way it would come loose without me doing it.

N74562 RIP…

-Don

[Sabremech]

  On 4/4/2025 at 3:53 AM, 47U said:

Interesting.  How long have you had this airplane?  Are you sure it’s the original spring?  It almost looks like the spring is too long.  Can you shim the hole in the flap handle to gain a little more tension?  Is the spring fastened correctly on the forward end?

@Sabremech  does this look correct to you?  

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I’ll stop out and get a picture of mine today for comparison.