CIA/Air America 'Quiet One' Helicopter

[Dynoman]

Started in 1968, the Quiet One, an OH-6A Loach was modified to conduct a classified mission in December of 1972, to deploy a group of trained Laotian commandos into North Vietnam to tap into communication lines connecting NVA commanders. All operations were to be conducted at night. Pictures courtesy of Air & Space.

 

[Dynoman]

A couple of additional pictures.

 

[Dynoman]

DTIC's document from Hughes on the Quiet Helicopter program 1972

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD753646&Location=U2&doc=GetTRDoc.pdf

 

[Dynoman]

ARPA, who developed the technology, initially had a representative helicopter from the Army, USAF, and Navy inventories during Phase I testing. These were a Bell Huey, a USAF HH-43B Huskie, and a Navy SH-3A. Bell couldn't deliver the Huey in time, so they substituted the OH-6A for it. The aircraft were taken to a remote testing site where acoustic engineers could measure the noise levels of the three helicopters. The OH-6A had the lowest noise signature.

DTIC document that includes a literature review with descriptions of the test results from the Phase I helicopters.
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA014640&Location=U2&doc=GetTRDoc.pdf

 

[martinbayer]

Somewhat surprising that the Huey with its characteristic thumping sound was even originally considered for that application.

Martin

 

[Stargazer]

Equally surprising is the fact that the the S-61 was evaluated but the Hiller FH-1100 or the Brantly B-2 were not considered.

 

[blackstar]

Agreed on both the Huey and S-61 choices. The Huey of course is loud (with the 2 bladed rotor). But why consider an S-61 with its two engines? My only guess is that their test objectives were not necessarily to come up with the quietest helicopter, but to determine just how much they could reduce the noise of existing helicopters. Developing a really quiet helicopter may have been a secondary goal, and the only one that got carried forward.

 

[Dynoman]

I agree with Blackstar. From reading the report it looks as if ARPA had sponsored the noise reduction program to improve the tactical capability of US military helicopters in general. Hence, the use of representative helicopters from each branch of service. Once they were tested they found that the OH-6A was significantly quieter over the other candidate helicopters. A Phase II funding effort continued to develop technologies to reduce its noise signature. I think the CIA stepped in later when considering a helicopter to use for the mission, which required visual stealth (flying at night) and aural stealth due to its operations near the enemy. Range and payload capacity would also become an issue as it had to transport a commando, a tap and relay system, additional fuel tankage, and its pilots deep into enemy territory.

 

[Stargazer]

Though it is probably a coincidence, it is interesting to note that the first mass production NOTAR (No TAil Rotor) helicopter, the MD900 Explorer, with significantly reduced noise, was a direct descendant of the Hughes Model 369 Cayuse ("Loach").

 

[Dynoman]

Stargazer, thats an interesting observation. I was reading an article on James R. Chiles, who wrote 'The God Machine from Boomerangs to Black Hawks," that broke the story on the Quiet One. He says that the CIA had an interest in quiet helicopters earlier than the Quiet One, and that their role would have been to ingress/egress CIA agents in the field. He says that the Quiet One came at the close of the war and there weren't any other missions planned for the two helicopters.

With technologies such as NOTAR and Quiet One out there, one can only wonder whats hovering around.

 

[blackstar]

With technologies such as NOTAR and Quiet One out there, one can only wonder whats hovering around.

I suspect that there's not anything else, for a simple reason--unlike for stealth and low observables, there is a commercial requirement for quieting helicopters. As a result, commercial companies have invested money and time into developing this technology. In fact, here's proof:

http://www.bluehawaiian.com/about/articles/new_era/

That's an article about the EC-130-B4 Ecostar, which is used for tourism. The tour operators wanted a quieter helicopter so that they would not get noise complaints. It mentions how they approached industry for quieter helicopters and were initially told that industry thought their helos were quiet enough. My point being that we really would expect any quieting technology developed by the military to make its way into the commercial world relatively quickly.

(Ironically, I'm a little sensitive to this issue today. This morning, starting around 6:40 am, a news helicopter was hovering only a few hundred feet above where I live, filming traffic. They stayed there for at least fifteen minutes. Woke me up. On my day off. Not happy. I filed a complaint with the FAA. Not a quiet helicopter...)

 

[quellish]

With technologies such as NOTAR and Quiet One out there, one can only wonder whats hovering around.

I suspect that there's not anything else, for a simple reason--unlike for stealth and low observables, there is a commercial requirement for quieting helicopters. As a result, commercial companies have invested money and time into developing this technology. In fact, here's proof:

http://www.bluehawaiian.com/about/articles/new_era/

That's an article about the EC-130-B4 Ecostar, which is used for tourism. The tour operators wanted a quieter helicopter so that they would not get noise complaints. It mentions how they approached industry for quieter helicopters and were initially told that industry thought their helos were quiet enough. My point being that we really would expect any quieting technology developed by the military to make its way into the commercial world relatively quickly.

(Ironically, I'm a little sensitive to this issue today. This morning, starting around 6:40 am, a news helicopter was hovering only a few hundred feet above where I live, filming traffic. They stayed there for at least fifteen minutes. Woke me up. On my day off. Not happy. I filed a complaint with the FAA. Not a quiet helicopter...)

I actually spend a good deal of time within a few miles of these very helicopters. From most aspects they're not actually quieter in real world use than the A-Stars they replaced, in fact you can usually hear them coming farther off! They're very nice, but I wouldn't characterize them as quieter.

In the early 90s McD DID try to sell a commercial kit based on the Quiet One technologies, AWST ran at least one story on it. I do not think anyone bought into the project though.

 

[frank]

While I love Hueys, we used to have a half-dozen or more USAR Hueys at my airport, how anyone could expect to sneak up on anyone in one (or a Cobra, even) is beyond me. As for the SH-3, I doubt the engine noise drowns out the rotor noise but its 5 blade rotor is quieter than the Huey. I've only had a few SH-3 / CH-3 helos at my airport during my time here, but at least they don't have the Huey's "whop-whop".

Agreed on both the Huey and S-61 choices. The Huey of course is loud (with the 2 bladed rotor). But why consider an S-61 with its two engines? My only guess is that their test objectives were not necessarily to come up with the quietest helicopter, but to determine just how much they could reduce the noise of existing helicopters. Developing a really quiet helicopter may have been a secondary goal, and the only one that got carried forward.

 

[blackstar]

More anecdotal yadda yadda from me. I live in a location that gets a lot of helicopter traffic because they navigate along the I-495 route.

The Alouette I complained about was not particularly loud, but in hover mode before 7 am it was quite annoying. (The CBS affiliate informed me that they were covering a traffic accident, which I guess is supposed to make it okay for disturbing a residential neighborhood.) Other than the occasional Robinson news chopper, I get USCG Dauphins (defending the Capital) and also Hueys, H-60 variants, presidential VH-3s, and sometimes CH-47s and CH-53s. Also German made (Eurocopter?) medevac choppers. The Dauphin has a distinct whine that is loud but fades fast (they must circuit the Beltway in the morning and evening). From the forward aspect, the CH-53s are LOUD, but the noise drops really fast once they go by. The older Hueys are of course the loudest and most easily identifiable. I think they also tend to be loudest even after they pass. The VH-3s are not all that loud. Now that I think about it, the VH-3s are also the helicopters I see that are most likely to not follow the north-south route that almost all the military helos fly, so they probably have less restrictive flight rules.

Man, I hated that Alouette...

 

[quellish]

I would have to dig around for the sources on this, but during approximately the same period as the Quiet One, CIA was operating a quieted Huey with a shortened 4 blade main rotor. From what I understand the quieting had significant performance impact, so it may not have been suitable for the Quiet One mission.

 

[Stargazer]

blackstar, I'm surprised that Alouettes (Alouette III, I suppose) are still flying in the U.S... I would have thought they'd been gone for a long time!

 

[blackstar]

And you're right. It was not an Alouette. I got myself confused. This is what it was. (I blame my confusion on lack of sleep caused by the danged helicopter!)

 

[Stargazer]

Ah, okay! This is an AS.350 Ecureuil, or perhaps it is called Squirrel in the U.S.? Anyway, that's what it is, a French helicopter nonetheless, on that point you were right at least... Guess it's now become a Eurocopter type, but don't know the designation thereof.

 

[blackstar]

They use Ecureuil in the US too. Only when I looked it up on Google did I realize that it meant "squirrel."

 

[frank]

I hear it mostly called "Astar" here in the USA.

Ah, okay! This is an AS.350 Ecureuil, or perhaps it is called Squirrel in the U.S.? Anyway, that's what it is, a French helicopter nonetheless, on that point you were right at least... Guess it's now become a Eurocopter type, but don't know the designation thereof.

 

[quellish]

What is this I dont even...

AD-753 646
OH-6A PHASE II QUIET HELICOPTER PROGRAM
Hughes Tool Company, 9/1972
USAAMRDL TECHNICAL REPORT 72-29
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0753646

"The purpose of the Phase U1 Quiet Helicopter program was to further reduce the noise signature of the OH-6A helicopter over that achieved
during the previous program. This was accomplished by incorporating extensive modifications and by operating the aircraft at 67 percent N2 at a gross weight of approximately 1600 pounds. The following new and/ or modified components were incorporated:"

Five-bladed main rotor system Four-bladed tail rotor assembly Engine exhaust muffler system Acoustic blanketing
Engine compartment doors
Modified
T63-A-5A engine Main rotor transmission Tail rotor gearbox Engine air inlet and plenum chamber Lower vertical stabilizer

"Only limited noise-level measurements of the fully configured test vehicle were obtained by Hughes Tool Company - Aircraft Division; however, the
data recorded by NASA' corroborated an overall sound pressure level (OASPL) reduction of 17 to Z0 decibels in hover and 14 to 16 decibels during flyover as compared to the standard OH-6A. The aural detection range of the standard OH-6A was reduced by a factor of more than 6 in the quietest flight mode of the Quiet Helicopter."

 

[flanker]

Don't think the article itself was posted here before:

http://sobchak.wordpress.com/tag/hughes-500p/#

 

[antigravite]

Hi.
Here's a jewel. The CIA recently declassified, just a few days ago (September 10, 2014) its related "Studies in Intelligence" article, available from:

The Quiet Helicopter (S) A technical Triumpf
http://cryptome.org/2014/09/cia-quiet-helo.pdf

This first hand account is worth reading as it also explains the program legacy, including the advent of FLIR, etc.
This is a very good paper from a key player (name still edited). Happy reading!!!

A.

 

[500 Fan]

A jewel indeed, AG. Thanks for posting.


500 Fan.

 

[fightingirish]

New article:
War is Boring - The CIA Built a Special Helicopter to Sneak Into North Vietnam

Older article:
airspacemag.com- Air America's Black Helicopter - The secret aircraft that helped the CIA tap phones in North Vietnam

 

[Dynoman]

Fightingirish, one of the four Hughes 500 helicopters that were mentioned in the article (War is Boring) that the CIA purchased as a cover story for the Quiet One program (although two are listed in the fleet of Air America) is shown below.

 

[Dynoman]

Five bladed rotor system of the Hughes 500P Quiet One.

 

[Dynoman]

Here are members of the Taiwanese air force inspecting one of the Quiet One's. The original mission crew was supposed to be Taiwanese pilots, however the crew selected performed poorly, resulting in the crash of one of the two Quiet One airframes. The difficulties in crew training and the infighting amoung the Taiwanese crew lead the CIA to send the pilots home and direct the US pilots training them to fly the mission.

 

[Dynoman]

Video of Quiet One starting at 1:21:
https://www.youtube.com/watch?v=g0NBhbrKvCI

 

[Dynoman]

AW&ST magazine article on Quiet One:

 

[Dynoman]

Sorry...Previously posted content. Quiet One modified with FLIR (not used in Vietnam wiretap).

 

[Mr London 24/7]

The Aircraft of Air America, 5th edition of 24 August 2015 , by Dr. Joe F. Leeker

The following database is the result of many years of research, especially done at the Air America Archives at McDermott Library, University of Texas at Dallas. All information contained in the sections entitled "Types of missions flown", "Statistics", and "Service history" as well as the photos are exclusively based on archival material, mostly preserved at the Air America Archives. Additional information came from the USAF Aircraft Assignment Records preserved at the USAF Historical Research Agency at Maxwell AFB, the records of the Director General of Civil Aviation of the Republic of China at Taipei, and other archives. The section entitled "fate" is mostly based on material published in various booklets and magazines whose information may be based on observation. This section is not considered to be complete. The references given in the section "Service history" indicate the exact location of the document within the Air America Archives, e.g. UTD/CIA/B51F12 meaning: UTD, McDermott Library, Air America Archives / CIA Corporate Records / Box 51, Folder 12. Abbreviations like ACA-22 or AVH-6 indicate the no. of the microfilm reel preserved at the AFHRA. Other abbreviations used may be looked up in the file "Abbreviations".

https://www.utdallas.edu/library/specialcollections/hac/cataam/Leeker/aircraft/500.pdf

https://www.utdallas.edu/library/specialcollections/hac/cataam/Leeker/aircraft/index.html

 

[ZacYates]

I would dearly love to see a Quiet One-style Huey. Have any images ever surfaced of the proposal or any mock-ups?

 

[hesham]

From Air Force 1998/4.

 

[yahya]

Is it known which nav and com systems apart of the FLIR were used in the 500P?

 

[Dynoman]

Quiet One had an Aerojet Electro Systems AN/AAQ-5 FLIR, which provided low altitude navigation at night, connected to a liquid nitrogen tank for cooling. Hughes engineers modified the FLIR using a Raytheon sensor. Pod mounted Inertial Navigation System (Singer-Kearfoot) and a LORAN C in a separate pod that provided area navigation. I do not know who made the displays.

 

[yahya]

Thank you very much indeed for the answer. I have two further questions.

1 - Do you happen to know the nomenclature of the INS and LORAN C used in the Quiet One, and how LORAN performed in the SEA mountainous environment?

2 - And did the Quiet One retain the com/nav equipment of the OH-6A like the ARC-51BX UHF, ARC-111 VHF, ARC-54 FM and ARN-83 ADF unless more contemporary solid state sets were used like the ARC-116 UHF, ARC-115A VHF, ARC-114 FM, and ARN-89 ADF?