Cast magnesium part, specification identification

[PhilLee]

I have a Twin Otter Nose Wheel is cast magnesium, yet I don't have any further info on it regarding the manufacturing spec. MIL-HNDBK-5 lists seven different specs for cast magnesium as follows,

AM100A
AZ91C
AZ91E
AZ92A
EZ33A
QE22A
ZE41A

Does anybody have any suggestions for identifying the type of casting I have here? I’m not getting any support from the OEM…

Thanks,
Phil

 

[CoryPad]

Does the part have an operating temperature above ~ 100 deg C? If not, then likely you have an AZ alloy. AZ91C and AZ92A are used rarely/never, so likely the alloy is AZ91E, if the alloy is not produced using high pressure die casting. If it is HPDC, then the alloy would be AZ91D.

If the temperature is above ~ 100 deg C, then likely you have one of the last three alloys - ZE41 would be the most common as the other two are used less frequently.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[PhilLee]

No it is not used above 100C, not sure if it is HPDC...

 

[aviat]

You said that you checked with the OEM, I assume that you refering to Bamdardier in Mirabel. But they didn't make the part so they may not have the information you need.

If you look beside the part number in the DHC-6 parts book there will be a vendor number and at the front of manual it will list the manufacter. On the outside of the rim there is a casting number stamped on it, and the vendor would know what it means. Your rim is probally a Goodyear and they have a component overhaul manual that gives what is repairable.

As a side note if you are working off-strip, especiallly on skies, you should consider changing to Al. wheels because mag. wheels a very prone to cracking when used under these circumstances.

If you require further information, just ask, because I can give you companies that have more information.

Cheers

 

[PhilLee]

I have been through Bombardier, and then to Goodwrich in Troy, Ohio.

We do have the Goodwrich component OH manual which has a repair. We are looking for the material spec to develop and approve an alternate repair scheme. The OH manual only pecifies 'Cast Magnesium', nothing further.

Goodwrich just replied a few minutes ago stating that they won't consider an alternate repair scheme other than that which is stated in the OH manual.

Looks like we won't get anything further from them...

What type of further info do you have?

Thanks,

 

[aviat]

The reason Goodrich won't give you the material spec. is to prevent the manufacture of bogus parts because they are liable for the product. The same reason applies to alternate repairs. If something were to go wrong with an alternately repaired rim, you and the person who certified the aircraft, as well as Goodrich could all be sued. What I trying to say is they are covering their butts!

From an operational standpoint the material is a “no need to know” item, and from a regulatory standpoint Goodrich’s OH manual takes precedence and must be used. If the repair you are considering is not in the OH manual the cheapest venue is to scrap the wheel. If you still want to use an alternate repair you would have to get it approved with your regulatory agency (ie FAA) and it would likely end up at Goodrich anyway.

As far as determining types of metal your dealing with, you can always reverse engineer it by taking a sample to a metal lab, and for a few hundred $ they will tell you what material it is.

Cheers