Mike’s Helmet Page

Mission

Background

My Pitts S1S is about the loudest piston vehicle going. 4:1 exhaust right below my feet, fabric sides, pumped up motor. I was lying in bed one night listening to my ears ring with tinnitis and decided that if I wanted any hearing at all by the time I was old, I need to do something about it now. I’d purchased and returned a Pilot 17-79 ANR headset because what it gained in active cancellation, it more than gave up in passive cancellation. I’d also been playing with the idea of a helmet for a couple years. The problems with the standard HGU55 fighter-pilot’s helmet are that it is expensive, didn’t fit under my canopy, was heavy-ish, and typically had poor noise attenuation (particularly with the stock ear cups). Some owners have had luck with the Oregon Aero helmet upgrade, earplugs, and a high volume level. It works but is hardly a perfect solution (in my opinion). By the way I tried reaching Oregon, but noone ever responded to my inquiry. Chalk up a black-ball for them.

My solution:

The in-the ear headsets come both in expanding foam and custom molded varieties. Inside the thing is a hearing-aid sized transducer that has a short plastic tube that goes up the ear canal to carry the audio. Although some places will tell you the custom molded version has better noise attenuation, other vendors (and people who’ve tried them) say otherwise. I chose the foam versions, which seem comparable in NRR to foam earplugs (25-30db). The only drawback is that it takes more time to saddle up (waiting for the foam to expand) and eventually they need replacing. The Precision Labs guy threw in some extras for free. I picked up some Howard Leight 33NRR foamies and they work great. Melt the hole with a soldering iron, and hold the transducer in there with a dab of Silicon.

Photos showing the finished helmet with snazzy racing stripes, and a show of the first generation of avionics wiring before going to a USB connector setup. Note the 1/8" socket and foam earplugs.

Connectivity

The foam earplug/headset products all come with standard 1/8" (3.5mm) mono audio plugs. As long as the soldering, strain relief, and plating have decent integrity, it should be as robust as standard aviation plugs. The socket for the headset is a Radio Shack solder terminal socket with a screw on shell. I started with a plated Radio Shack female solder jack with screw-on shell, but that failed quickly. I'm currently using the female end of a cannibalized headset extension cord. Works great. I mounted it next to the microphone mount on the helmet with a nylon cable clamp. Initially I just soldered that into a cannibalized headset cord. It worked fine until everything went dead on the race course at PRS in June 2002. Turns out these were the brass plugs with small screws that attach ring mounts to the plug body. They had simply come unscrewed. Lock-tite would have fixed that, but I also wanted to solve the problem of having an in-line quick-disconnect that would not leave me dangling in a bailout. Furthermore, an inline connector would allow me to put the helmet on before getting in the plane.

Thus began the search for a good 4-conductor connector for the purpose. Aviation does provide for us a U-174 4-conductor connector (used typically in helicopter installations). These are available in different forms from different places: extension cords, conversion cords, solder plugs and sockets. I was just about ready to plunk $70 on the necessary connectors when another idea came through to look at standard commercial connectors. The obvious condidates to me were USB and IEEE-1394 (firewire) which are compact, low cost, well shielded, seem to be suitable in terms of retention force, and would allow me to completely get rid of the bulky legacy connectors. I got an A-to-A USB extension and cut off the female end for installation into the helmet. I bought a $5 panel mount female connector at Fry's for the other end. An A-A (male-male) cord now connects the helmet to the panel socket. It works out great since I can put on the helmet before saddling up, and plug in the wire once I'm strapped in. So far in 8 years of flying, no issues.

The helmet was an easy solution. Lightweight carbon/kevlar helmets that are suitable are made for skydiving and hang-gliding. Neither are DOT safety levels, but neither is the HGU55. I ended up with an all-carbon helmet from Bonehead Composites because a) they accommodated my big head b) I had the chance to visit them in Peris CA and they are good people, and C) they were selling out their old model Mindwarp helmet for $60. Skydiving helmets usually support the mounting of an audible altimeter next to your ear. They have several models today they didn't have back then that look suitable for this application. I added Kevlar layup to reinforce the forehead-crown area and patched the audible hole. I bolted on the Flightcom boom electret mic and a 3.5mm (1/8") Radio Shack mono audio connector for the headset and it was good to go.

Summary Evaluation

The whole setup is the same weight as my conventional headset and probably actually gives me a little more space between me and the canopy. I’m confident that noise attenuation has reached the diminishing returns point where more noise enters my ear through bone vibration that through the ear canal. All that for $110? That’s two big thumbs up!

Vendors of in-the-ear headsets:

Vendors of form-fitting helmets:

Vendors of traditional helmets:

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