Making an A-11, WWII Flying Helmet operational

[Saville]

Hello everyone. For the longest time, I've wanted to turn a WWII USAAF A-11 flying helmet into an operational, useful helmet using modern electronics but maintaining the look of the old helmet as much as possible. I've finally gotten around to starting that project. I've had an A-11 in decent shape for quite some time. All I had to do was to find the parts and figure out how to make it work. This thread will report on the project as it goes along.

Just a note:

If you are of the opinion that objects such as WWII flying helmets should not be permanently modified in any way, I completely understand your point of view. However this topic will not be to your liking. So I give fair warning. The modification isn't much but it's there. I'd like to keep the topic to the conversion project and not an argument over whether or not it's ok to modify a WWII USAAF helmet.

Now you can buy AN-H-15's (USAAF Summer weight cloth helmets) that have been modified with modern electronics and ANR. Cost is over $600 which is more than I want to spend.

What you need for this project is:

2 civilian 300 ohm receivers
one civilian electret microphone
mike boom
modern, civilian 2-plug wire loom
WWII-era mike boom mount.

and of course the helmet. This will work for AN-H-15's as well as A-11's.

I also bought a Mike Muff as I find that helps with noise.


Here's a photo of the stuff that I bought:



I got most of it from Oregon Aero. Here are the SKU numbers:


Civilian Helmet Speakers (2) #98332

MicMuff® Microphone Cover #90015
SKU 90015

7" Wire Frame w/Electret Mic & Cord (Black or Gray) #98303-7
SKU 98303-7

3/4″ thick SoftSeal/HushKit® Combo #28034
SKU 28034

The boom mount ("U" shaped object in the center of the photograph above) I got from some online source which I cannot remember.
But one such source is Bells Aviation.

Ok. So to begin with, the receivers that came with the helmet fit into circular slots in the oval-shaped rubber earcups on the helmet - the red arrow is pointing to the slot:




The protruding lip on the WWII receivers fit into that slot (red arrow in picture below)




However if your receivers are in the earcups, I've found that the safest way to remove them is to first take the step outlined below regarding removing the interior padding from the helmet. Then unscrew the top half of the receivers and remove it. Then remove the bottom half from the INSIDE of the helmet. The opening on the inside of the helmet is larger than the opening on the outside of the helmet. And it's easier to remove the small flat circular disk that is the bottom portion of the receiver.

Now it turns out that the modern civilian receivers fit quite handily right into that slot. In fact in the picture above, you see the modern receiver sitting to the left of the WWII version. The diameters are almost identical.

But if you put the modern receiver into the slot you see an immediate problem:



The rubber edge covers the holes into which the wires must go. Now one option you have is to cut away the rubber. And in fact there's a form of these rubber earcups - used in headsets - where that was actually done. See here:



Those ramps at the bottom edge of the hole would reveal the holes in the receiver for the wires. If you were careful you could make such ramps and the wires would have a path. This was not done on these sorts of helmets, but as I say it's not unheard of.

I elected to NOT do this for several reasons:

1) In the thread entitled:

Old RAF type leather helmet - adapting to ICOM type handheld?



Ron W correctly points out that these helmets were not made with an emphasis on noise reduction. I bet a lot of the sound you want to hear will run right out the back of the receiver.

2) I'd like some noise protection for my hearing.

3) The original helmet has the bakelite housing of the receivers sticking out the sides. I'd like to retain that look if I could.


So this is why you see, in the parts list above, the "Soft Seal Hush Kit". I got the 3/4" thick kit and the size of the earcups in the kit are slightly thicker and slightly bigger in diameter than the suede padding that originally came with the helmet See comparison in the next two photos:





So the first step is to carefully remove the suede padding from the two earmuffs on the inside of the helmet. They are held on with a very good rubber cement. If you take it slowly and carefully, you can remove the padding without damaging it or the rubber earcups at all.

Given that the Hush Kit earcups are bigger, the sides of the helmet might stick out a little more when you put it on. Some of that will be reduced when you tighten the chin strap. Also I'd imagine the suede padding was thicker originally.

Ok in the next post, I'll show how to fit the receivers into the Hush kit; how to mount the hush kit to the inside of the helmet with Velcro, and how to introduce the wiring into the helmet the Hush kit and into the receivers.