Warbird Information Exchange

I'm looking at setting up a MBU-12 for GA use, and I'm wondering how to connect the O2 hose on the mask to a general aviation portable O2 system.

Also, how do you connect the mask's mike to the helmet? I have a boom mike on top of my O2 clips (as suggested by Brad Pilgrim a long time ago), and I can disconnect that mike and I guess that I could plug the wire into the mask.

Any ideas?

The mic is inside the O2 mask. There is a comcord that runs along the oxygen hose on your MBU-12. The bottom part connects to the radio, at the top is a plug to connect to your helmet speakers.
You will need an adapter for the comms to go to general aviation impedance and/or plugs. Probably an adaptor for the oxygen hose as well.

Does the mask have the CX-4707 chord installed? If so, it should have a U-174 single plug on the end (same as what's used in helicopters). From this, you simply need to get an adapter like the Sigtronics SIG-900051 to be able to plug it into your airplane's system.

My mask will just have the little cord to be plugged in my HGU, I already have a quick disconnect cable that goes out of it.

I'm more concerned about the O2 hook up than the comms actually.

Post a pic of the helmet/mask and the oxy generator fitting

Here's the O2 bottle. It's a standard Aerox unit for GA airplanes. Diameter of that fitting is 0.9".


Untitled by comiquaze, on Flickr

Mask is a standard MBU-12 with the standard connector at the end.

Don't take this as gospel, but here's my two cents:

on the mask end: a CRU-60/p or equivalent

On the bottle: an oxygen regulator and the hoses/fitting to connect it to the bottle on the one hand, and the CRU/60 on the other

The bottle has a standard thread, so the key is getting the right regulator and connector on the output end. I'm looking through the GENTEX and Gibson-Barnes catalogs, and everything refers to panel mount connections with the CRU-60/p and CRU-94/p, so there may or may not be a straight-to-bottle attachment available.

Okay, I think I found what you need.

There is a portable oxygen regulator, Type A-21, that I find several references for. This is what the USAF and USN use for portable oxygen bottles and appears to have the CRU-60/p connector on it.

Thanks, that's very useful!

I'll keep you guys posted!

Do you happen to have a picture of that A-21 regulator?

Ok, found one off Ebay...

http://www.ebay.ca/itm/Scott-A-21-Milit ... _775wt_689

Ok,

I've checked a few things and I would need a CRU-79 regulator and then some fittings and a hose to plug into my tank.

What do you think?

If you get a CRU-79/A, you need to make sure you get the whole rig from the chest pack with the elbow fitting and additional hose or else you won't be able to make it far from your mask. Also, the problem you may run into is that without the full rig, the mask is not exactly "quick disconnect" as the fitting to the mask hose is not designed to be removed, instead left with the mask and helmet at all times.

With the CRU-60/p and A-21, you can get a long hose from the mask to the CRU-60/A and then the A-21 simply attaches directly to the bottle, allowing you to easily remove the bottle for filling and servicing without having to take the mask with you or needing a tool to disconnect the mask from the bottle.

Thanks for the input.

Problem is finding a suitable A-21 regulator. The one on Ebay was a real veteran from some unamed conflict.

Do you have any leads?