Headset plug problem, advice?

[Pilot DAR]

Hi Rotorheads,

I have a David Clark headset helmet. It works fine in the SW300's I flew, and an AStar I recently flew for a few hours. I does not work in the Hughes 500's or Bell 206 I have flown (and of course, in all three cases, I've been running on the helipad before I figured this out!

Is there any advice on differing wiring configurations, in which it would work in some helicopters and not others? I would like to fix it, as I have 500 flying coming up again.

Even the avionics shop seemed Mystified. Your thoughts and ideas would be appreciated.

Thanks, Pilot DAR

[Unhinged]

"It does not work" leaves a lot of lattitude. We'll need a bit more info ...

Which model is it ? In particular is it noise cancelling ?, and does it have a press-to-talk switch on the headset ?

What exactly doesn't work - Microphone, speakers, or both ? Can you hear anything ? Did you try transmitting, and, if so, can anyone hear you transmit ?

[spinwing]

Mmmmmm ...


A bit more information would be helpful ....

Also a "search" would have no doubt revealed that this problem has been attacked on this forum before.

My guess here is that your microphone impedance is incorrect for the avioncs install on the "fault" aircraft .....

What type of mic do you have installed on you headset .... if you have the "dynamic mic" (without the amplifier) install you might try an "amplified dynamic mic" in its place ... this may cure the "fault".

If your headset is a standard commercial use set the actual h'phones will no doubt be 700 ohm impedance units ... if set up for military a/c they will be 8 ohm units ... but ... I doubt the wireing of your headset is the problem ...unless your "avionics specialist" had been at work on it.

I'm a bit worried that your "avionic specialist" could not diagnose this fault for you .... you might want to consider a change there!

Cheers :E


BTW ... wire diagrams for Dave Clark headsets are available off the Dave Clark website ....look em up!

[WylieCoyote]

First off why does everything American have to be bigger?:)

Seriously though, I have a set of DC's H10 13H and have only every had problems twice with them not working and it turned out to be the fit on the aircraft and so there was no solution, other than re-wiring the aircraft!

[Senior Pilot]

This thread (http://www.pprune.org/rotorheads/303546-uk-us-nato-headset-plug.html) may also help :ok:

[Agaricus bisporus]

Earth loops sometimes cause compatability problems, either mic and tel earths being commoned or seperate, and if not the same in helo and headset, or adaptor lead, you can get problems.

Buy a Peltor!

[Pilot DAR]

Thanks so far,

My appology, "doesn't work" means that I expected it to work, because the helicopter socket accepted the plug on my headset, but I could not hear or be heard in the certain helicopters mentioned, where in the others mentioned, it worked perfectly in both regards. All of the helicopters are Canadian operated, and the only non-US manufactured one was the AStar, in which the headset worked! The headset is not noise cancelling, and does have the "US NATO" plug shown, not the stylish "UK Gold" (which must obvioulsy be depicted smaller out of courtesy, or it's attactivenes would completley overwhelm the US one, if compared in the same size image!).

I considered the mic impedance, and it is an older mic, but I do not think that would affect the "phones" function of the headset. The use my headset did not interfere with the aircraft system, as the other pilot could talk to himself over the intercom in each case, and only realised that my headset did not work, when I told him.

One pilot with whom I flew mentioned a ground (earth) difference, but I asked around, and nobody knew. In all cases other than the AStar, the headsets found in, or intended for use in the helicopter were David Clarks, so I just expected mine to work equally well. I will check out the referenced links.

I appreciate your thoughts...

Pilot DAR

[Gomer Pylot]

I suspect the aircraft you're having problems with use military-style avionics, which have a different impedance than standard civilian avionics, both for the mike and for the speakers. The speakers should work a little, but you'll have to turn the volume full up just to barely hear anything. I've used standard military headsets in civilian aircraft, with a mike amplifier and with a civilian mike, and I had to turn all the volumes full up, both on the radios and the mixer box, just to hear. The impedance mismatch is too great to be easily overcome. DC does sell a dual impedance headset, which lets you change between the systems by just flipping a switch on the headset.

[theavionicsbloke]

Pilot DAR
"could not hear or be heard in the certain helicopters mentioned"

Your DC H10-13H headsets have a U174 connector fitted. This is sometimes referred to as the US Nato connector (The one with Silver coloured terminals shown in 'Vital Action's very well presented pictures).

The SW300 uses a U174 socket, so that’s why they work there.

The Hughes 500 & Bell 206 along with dozens of other Airframe Types and installations use the UK NATO connector (The one with the Gold coloured shown in 'Vital Action's pictures). Although they look VERY similar and the U174 connector will fit into the UK NATO socket, the Tels ground terminals do not correctly align and they will not work correctly together. Sometimes you can jiggle the connector around and by luck you get some functionality. You will notice that when you attempt to use this combination that they will not lock together properly.

Solution: Purchase an adapter 'UK NATO' inline Socket to U174 (US NATO) Plug as again shown in Vital Actions picture.

These can be purchased on a next day delivery from Most good UK pilot shops. Headset Services, Adams aviation, Harry Medelssohn all normally carry them as standard off the shelf stock. Prices vary between about £15 to £30. If you really want to get flash Dave Clark also do an adapter.

And for info guys, civi avionics systems are standardised at 600 Ohms impedance. Most headsets provide a standard 600 Ohm speakers as standard unlike you domestic ones you may use on your stereo or computer at home of which is 8 Ohm.

[Pilot DAR]

Thanks Avionics bloke, for that very succinct advice. I will seek out the required adaptor (shame, I was at the pilot's shop two days ago, looking at a display of such things I did not think I needed!). In light of your very helpful information, is there any sure way to identify which connector type is in which helicopter type, without going to the parts catalog? I would not have expected to find UK connectors in a US helicopter, or, apparently, a US connector in an AStar! Would I expect to find a placard, or information in a flight manual?

Cheers, Pilot DAR

[theavionicsbloke]

You will not find anything in the FMS or placards simply because there is no certification requirement to do so.

As a Guide

General the UK NATO would be referred to as a NATO connector. Airframes that were or have been used by Military or aerial work tend to have the NATO connector fitted for obvious reasons. Eg the Hughes 500 or BO105 was originally designed for Military use. These of course are US manufactured but deployed world wide.

The US NATO as referred to is generally used in US manufacture helicopters airframes originally intended for civilian use eg R22.
Sometimes you may also find that the US NATO’s may have been replaced with a standard NATO socket where it’s been adapted for Police Role work eg MD902.

You can tell by just looking at the face of the socket but unfortunately that comes with experience. Also, you should feel a positive click as you fit the plug into the socket. NATO into a U174 (US NATO) will just not feel right. With practice and experience you will learn to identify this within seconds.

Helmets would normally be ordered with a standard NATO because professional working aircraft with crew requiring helmets eg Pipe Line, Police Military etc would normally have NATO sockets fitted. These guys would normally only be flying one airframe type so no problem.

If you fly numerous types then you MUST carry adapters in your flight bag to avoid any embarrassment.

Adapters are available at the DC website if you have difficulty in finding one locally.

[Pilot DAR]

After reviewing all of the very helpful advice here, and then contacting David Clark, I understand the problem. In all cases the connectors have been compatible (all U-174 type). Apparently some helicopter's systems are mic and phone polarity sensative, while others are not. David Clark also says that the impedance is not the problem, as the helmet's operating elements are equivilent to a DC H10-36 headset, which I'm told is still a current product, and will work in any civil helicopter.

The helmet I have was only made for a few years ending in 1985, and is so little known that it is not listed in any of their parts history, and the service rep had never heard of it. Only the David Clark tag sewn into it convinced him that it was not another company's product. It would appear that it was wired differently, and needs to be changed to be compatible and up to date. Funny that it worked in brand new Sw300's but not the much older H500 and B206! DC confirmed that the wiring diagrams offered in their parts pages of the website are the same plug pattern for all headsets which use the U-174 plug. Any different arrangements are now historical.

I was very impressed at the resorces which the David Clark staff devoted to solving my dilemma. The service was prompt and very thorough. I certainly recommend David Clark for good after sales service, even 26 years later!

Thanks to those who offered help to my inquiry, it made the difference!

Pilot DAR

[Gomer Pylot]

DC's customer service is, IME, the best in the business.