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MX-1622/AIC-10 Flight Helmet / Headset Adapter


Wayward Son
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Wayward Son

I picked up this flight helmet "Go With" from a local military surplus dealer. It is a NOS communications adapter described as: 

 

THE MX-1622/AIC MICROPHONE ADAPTER IS USED WITH VARIOUS KOREAN WAR VINTAGE MILITARY AIRCRAFT RADIO HEADSETS AND FLIGHT HELMETS.

 

- IT HAS A TWO CORDS ONE  WITH A U-93/U PLUG AND THE OTHER WITH A U-61/U JACK WHICH ACCEPTS A PJ-292 MICROPHONE PLUG AND A PL-354 OR EQUAL SHORT BAILOUT PLUG AS FOUND OF THE HS-33 AND H-46/UR HEADSETS   AND SOME FLIGHT HELMETS THAT HAVE CARBON BOOM MICROPHONES WITH TWO PIN PJ-292 OR EQUAL MICROPHONE PLUGS.

- THIS ADAPTER ALLOWS  OLDER  OLDER  600 OHM MILITARY HEADSETS WITH CARBON  MICROPHONES TO BE USED WITH NEWER LO IMPEDANCE RADIO SETS. 

- THIS ADAPTER WAS USED WITH THE OLDER P-2  AND P-3 HELMETS WITH CARBON MICROPHONES

 

The adapter was manufactured by the US Air Force at their San Antonio Air Materials Area (SAAMA) in Texas.

 

I have no idea if my depiction is of correct use, but I thought "What the heck......"

20210418_135539_2.jpg

20210418_135757_2.jpeg

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Vark_07

That's a nice and uncommon find indeed ! Never seen / read about it before.

However, out of curiosity, I've managed to find the reason of its existence after searching the web.

 

Quote

Around 1953-54 the USAF decided to improve the communications by changing to a new lower impedance standard.

The new standard for aircraft "intercom" was designated AN/AIC-10 (and later AIC-18) and the first matching helmet headsets in widespread use was the H-75 series with the characteristic "top hat" mounts. This upgrade was the direct cause for changing the helmet designation from P-3 to P-4.

 

The new headsets installed from P-4 helmets and retrofit in earlier helmets was only 9,5 ohms with a 5 ohms microphone, and suddenly the earlier "low" impedance headsets like the HS-38/HS-38A had become "high impedance" (with their 600 ohms). The standard introduced in 1953 is is still the USAF standard today.

(C) Best-of-flightgear.dk

 

This small 2-pin / 1 large-pin dual U-61/U connector on the first pic is the relevant female counterpart to the U-75/U plug sported by the headset present in P-1, P-1A, P-1B and P-3 USAF helmets before the 1953 change.

 

So, this somewhat "barbaric" description with multiple headsets / plugs nomenclatures you've quoted basically states this adapter allowed the use of USAF helmets fitted with older-standard headsets in planes sporting the newer low-impedance audio system (hence the presence of the U-93/U plug that was introduced with the P-4 series and Army APH-5A - which is known to be the early version of the U-174/U jack plug encountered later on USAF's HGU-2A/P, -26/P and -55/P paired with MBU-5/P, -12/P and -20/P masks' comm cords, until the present day).

These basic but insightful diagrams will hopefully help you out with the plugs' nomenclature 😉.

 

It's also interesting to note that almost 70 years after the USAF abandoned it, this dual-plug / connector U-61U/75U combination remained used in the USN / USMC until the present day with APH-6, PRK-37-based helmet series, and HGU-68P/85P paired with MS-22001, MBU-14P/17P and MBU-23P/24P masks' comm cords !


1426968903_U-75Uplug.jpg.50ba20c66f15f9a394f02e17eea96443.jpg
U-75/U plugs found on MS-22001 mask's comm cords paired with my APH-6 helmets.

 

Side note : As a matter of fact, this 1953 impedance change was not the first attempt, for I've read that at the beginning of WW2, the standard was in the 4000-ohm range, until the 1943 change in both USAAF / USN which saw it lowered to 2000 ohms.

 

 

In the end, this mysterious find of yours appears to be actually pretty iconic of this short -yet important- transition period of the mid 50's in the USAF. Nice & uncommon score !
-Gauthier

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