Jump to content

Notice: Effective July 1, 2024, Vertical Forums will be officially shut down. As a result, all forum activity will be permanently removed. We understand that this news may come as a disappointment, but we would like to thank everyone for being a part of our community for so many years.

If you are interested in taking over this Forum, please contact us prior to July 1.

Help Needed With Alpha Eagle Eog Questions...

Recommended Posts

Is there anyone out there that can help with the following technical questions on the EOG? After canvassing several pilots/engineers, and searching in vain online, I'm still drawing blanks:


Side Connector/Jack Plug choices:


U172/U-TP 120/U






IMPEDANCE: (at plug)

9.5 OHM

150 OHM

300 OHM

600 OHM


If anyone can help with a layperson description of the differences, and point me to the best answers I'd appreciate it... It's for civilian operations - typical fleet operated in Canada...




tin lizzie

Link to comment
Share on other sites

Perhaps this is not what you want as I do not know the correct plug but - I bought my

Eagle from Interactive Safety Products and they knew which plug was the correct one for civilian operations. Perhaps they can help you??


My best advice though is this - get another brand!! Tthe visor is badly ( I mean horribly) designed and the helmut seems larger than the French one which most pilots seem to be purchasing now, and all I talk to who wear them like them a lot. Many Eagle wearers wish they had bought a different brand and one guy I know got his Eagle visor fixed but still was not happy and got the French one.


Good luck.



Link to comment
Share on other sites

You have two major issues, assuming you already bought the headset. Is it low impedence or high impedence?


Low impedence 9-12 ohms is the system usually used in the B205.212,S76, S61 if they have the original audio systems. The plug is usually the U172U/U- NATO plug, a fat single plug with 4 rings.


High impedence is 600 ohms for the headsets out but will measure 300 ohms on the plug as both elements are in parallel. The microphone is 150 ohms and requires a mic voltage from the radio or audio system to enable its operation.

Plugs can be anything listed above if the audio system has been replaced and the installer put in the NATO plugs or the Twin Otter Plugs (U75 - short plug and 2 little pins). I have seen and also installed every combination depending on the installers desire.

Best bet is to find your avionics dude or dudette and find out what you have in your specific helicopter. I would guess a high impedence (AKA Carbon Mic) system. If your plug is different and you have purchased a high impedence headset, get them to build you a little gender-changing patch cable - save lots of fiddling.

But beware if you plug a low impedence Hdst into a high impedence audio system at worst you could fry the elements but it definately will not work.


Only use for the large stereo plug is for the ground handling ICS on a large a/c such as a B737

Link to comment
Share on other sites

Freefall & Bugman,


Thank you for your input. I did get some preliminary information from Interactive Safety Products, from whom I plan on purchasing the helmet, but the impedance/plug recommendation came from a sales person with no accompanying explanation of the different choices.


Re helmet selection, I agree the Gallet feels light in the hand, but I tried on my boss's and didn't like the feel of it on my head. There is one fellow here with an old Gentex and he seems to really dislike it, complaining that it is hot and heavy so I didn't even consider it as an option. I was able to try on the Alpha in a selection of sizes and found one that seems to fit really well and was comfortable (for the 2 minutes I had it on!). I guess I won't really know if I made a good choice until I get the opportunity to fly it.




I have not yet purchased the helmet - the two questions I asked were from the "Easy Order Guide (EOG) and I didn't want to choose an option without a reasonable understanding of the ramifications. Based on your information, and that of another local operator I visited today, I think I will opt for the lower impedance - originally I had thought 300 ohms, but maybe 150 is a better way to go? You will note the impedance choice I am being asked to make is for the plug end.


The machines I would likely be flying (fingers crossed!) in the near (ie foreseeable) future would be JetRanger, LongRanger and A-Star. Unfortunately the avionics package in each machine is different so I am aiming for the helmet options likeliest to be widely compatible. Eventually I hope to get my hands on the mediums you describe, but I am sure it will be a ways down the road as I am at the beginning of my journey.


Can you explain this: "If your plug is different and you have purchased a high impedance headset, get them to build you a little gender-changing patch cable - save lots of fiddling.




As an aside, someone pointed out the following article (extracted from TPE 185E 4/2006) and I noted that all the pilots at that company had manufactured a 6" intermediate "pig-tail" cord for installation between the helmet and a/c receptacle. After reading the article, searching the topic online and checking the jack installations in our aircraft, I decided I'll be getting one too.


Many thanks,


tin lizzie

Link to comment
Share on other sites

[Can you explain this: "If your plug is different and you have purchased a high impedance headset, get them to build you a little gender-changing patch cable - save lots of fiddling.





I have a David Clark headset that I used for years when I was doing lots of avionics test flights in a variety of aircraft. The end of the cord had a NATO plug on it even though the headset was a high impedence type. If the aircraft was equipped with different jacks, I had an assortment of patch cords I could use to allow connection into any of the common jacks used with in the industry. For instance, if I went in our (Dome Petroleum) BO105 I could use the patch cord with two seperate plugs that would also work in our Aztec or GII or whatever, in the Twin Otter I would use the U75 adapter. If I went in a B206 with the NATO jacks I would plug in directly.

However if I went into our S76 or S61 I had to use a different headset as they were low impedence systems. I did not make an adapter to go between the two different audio system types. I read the attached TSB report with interest as it cetainly makes sense. However I was surprised that they were using the "Twin Otter" (U75) plugs with bulkhead-mounted jacks as they are a pain to deal with and nearly every one I have seen in on a dangle cord.


I have attached a couple pictures of our BO 105 as we were buzzing around the GWN a "few" years ago. You can see where we installed the jacks as we had done a total retrofit of the helicopter when we purchased it new--joys of working for an oil company ;)



Link to comment
Share on other sites

U/172/U/93 combo, I believe is normal.


Gary, that cliff in the first picture is really vertical... lol


A hair more maneuvreable than our 355's...



As you can see we had done a "few" mods to make it an offshore "IFR" machine including a RDR 1400 Radar, C12 compass, etc etc. If EFIS and Laser gyros had been around in 1983 we would have installed them. The joys of an oil company budget

I was never inverted in it but that does not mean the a/c was never inverted :lol: or so the rumour goes.........


Link to comment
Share on other sites



Spoke with Jurg Fleischmann during the Red Bull event, he's the camerapilot, and one of the european "aerobatics" pilots for the Red Bull BO-105.


He said no problems at all, just be gentle and not pull to hard. Said they initiate the loop at 500' AGL, pull over the back, and are recovered at 200' AGL. Does not even put 2 G's on the thing.


(I'll demonstrate this next week on our R-44.... (Not))


Only thing to watch out for is those low level turns, as proven multiple times on Youtoobe, with that BO eatin' the dust, killing the pilot (who apparently knew better...)




Link to comment
Share on other sites

The only difference is that our Bow Cow was so nose heavy we had to put a metal-deck floor in the back to get the CofG within limits. Only the second helicopter I worked on that needed extra weight. I seem to recall that the early B47s required a weight be installed when operated single pilot. I think the weight lived somewhere near the engine and was moved forward. To long ago to be sure

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...