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Dynon autopilot shear screw

seagull

Well Known Member
I lost altitude control in the autopilot because of a broken servo shear screw. I called Dynon and they offered to send one to me. It was my understanding it was a free service from posts I had read here, and they had had problems before and made the pin more robust.

I just received a charge for $8.50 for 1 shear screw.

Rethinking my opinion about the company.
 
You may be under that impression...

From Dynon:

" – contact Dynon Avionics Technical Support (contact information at the
beginning of this manual) for a replacement shear screw."

But there is no mention anywhere in the installation manual or revisions of this being a "free replacement".

Bummer about the broken part, and:

"A broken shear screw indicates an abnormal condition in the installation and/or
operation of the autopilot and servo, much as a blown fuse or a tripped circuit
breaker indicates a problem in the electrical system. Shear screws should be
replaced with proper parts only after any problems are corrected."

Fly safe
 
I lost altitude control in the autopilot because of a broken servo shear screw. I called Dynon and they offered to send one to me. It was my understanding it was a free service from posts I had read here, and they had had problems before and made the pin more robust.

I just received a charge for $8.50 for 1 shear screw.

Rethinking my opinion about the company.

Have you verified what the charge was for the part or shipping? Dynon uses UPS and that sounds about UPS normal rate for the smallest of packages.
 
I got a call back from Jeff. He clarified the charge. The $8.50 charge is their minimum postage charge. The replacement screw is free. I asked for a second screw since both of mine are prior to the 2017 upgrade and the roll is probably going to break soon. Jeff said he would try to put a second one in the package if it hadn’t shipped yet.

My faith in Dynon has been restored.
 
The screw’s (2) came today, thank you Dynon. Other than removing 69 screws to access the servo a rather simple repair.
 
Some questions about the shear screw itself

Surely I cannot be the only one wondering: what are the specs on the Dynon servo shear screw?

Why can't it be obtained from another source (i.e. locally)?

And for extra points: why can't Dynon ship it in a small padded envelope for less than $8.50?
 
Why can't it be obtained from another source (i.e. locally)?

I'm sure it could, but don't expect Dynon support for that. They have traceability and material certs on the parts they send out, some random pin from ACE doesn't. Given the importance of this component, I don't know if I'd source it from just anywhere. Seems like a fairly cheap item to get an OEM replacement for.
 
Surely I cannot be the only one wondering: what are the specs on the Dynon servo shear screw?

Why can't it be obtained from another source (i.e. locally)?

It is not an off-the-shelf screw that you could buy from any hardware supplier. It is a small cap screw that is custom modified so that it will sheer at a specific force value.
 
Surely I cannot be the only one wondering: what are the specs on the Dynon servo shear screw?

Why can't it be obtained from another source (i.e. locally)?

And for extra points: why can't Dynon ship it in a small padded envelope for less than $8.50?

The screw appears to be brass and has a specific diameter just beneath the head. This diameter looks to be slightly bigger compared to the one I removed (upgrade?). The screw shears at this diameter and the shear is important in case there was a servo run away or jam. The servo directly controls the stick, not a good place for things to freeze.

Concerning the shipping, it was shipped in a USPS flat rate box. Inside the box was 99% air 1% screw kit. There is definitely more cost effective ways to ship. The only benefit to Dynon to ship it cheaper would be customer satisfaction. Maybe the thought process is don't complain you are getting a free screw.:eek:

I haven't had my coffee yet.
 
50581719147_31cd3384f9_c.jpg


This pic is the old style broken shear screw and the new replacement.
The old one, pre 2017 has a machined diameter below the head of .070, the new one is .100.



50581719567_63ca79e732_c.jpg


The packaging, shear screw, allen wrench, cotter key, loctite and instructions.
A very complete repair kit.
 
Going to order 2 in the morning to add to my spare parts supply. Will gladly pay for them AND the shipping.
 
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