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New airplane?

This is a discussion on New airplane? within the Air Force & Aviation forum, part of the Global Defense & Military category; I just joined this forum to ask a question of anyone that may have an idea where I should look ...


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Old June 6th, 2013   #1
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Question New airplane?

I just joined this forum to ask a question of anyone that may have an idea where I should look next for more information.

First a bit about me. I am a private pilot. I was US Army in Vietnam, and am a retired computer engineer. Also, I did work as a civilian on the A6 weapons system simulator back years ago, so I do know a little about aviation, and more specifically Navy Aviation. I do not claim to know a lot, and my experience is old (like me).

Ok, now the question: Any idea what would use a ducted fan for a prop? (that is what it sounded like to me) Very high speed, ducted fan sound kind of like the old sound suppressed ducted fans we used to use in the old very large computer systems for cooling.

I did not see the aircraft. By the sound, It was flying low and (guess) about 300+ knots, west to east.

I would assume Navy or Air Force, we have a NAS about 150 miles west and an Air Force base about the same distance east of us, and because of proximity to the Canadian border (I assume) we have regular EA6B and F15 flights in our area.

But this was strange. Definite a suppressed ducted fan type sound, I doubt they could ever make a fan jet that quiet, even though a fan jet is just a very large, multi-stage. ducted fan.

Any idea's what I heard?
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Old June 6th, 2013   #2
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Originally Posted by hermannr View Post
I just joined this forum to ask a question of anyone that may have an idea where I should look next for more information.

First a bit about me. I am a private pilot. I was US Army in Vietnam, and am a retired computer engineer. Also, I did work as a civilian on the A6 weapons system simulator back years ago, so I do know a little about aviation, and more specifically Navy Aviation. I do not claim to know a lot, and my experience is old (like me).

Ok, now the question: Any idea what would use a ducted fan for a prop? (that is what it sounded like to me) Very high speed, ducted fan sound kind of like the old sound suppressed ducted fans we used to use in the old very large computer systems for cooling.

I did not see the aircraft. By the sound, It was flying low and (guess) about 300+ knots, west to east.

I would assume Navy or Air Force, we have a NAS about 150 miles west and an Air Force base about the same distance east of us, and because of proximity to the Canadian border (I assume) we have regular EA6B and F15 flights in our area.

But this was strange. Definite a suppressed ducted fan type sound, I doubt they could ever make a fan jet that quiet, even though a fan jet is just a very large, multi-stage. ducted fan.

Any idea's what I heard?
Could it have been a V-22 Osprey.
Big blades whacking through the air?
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Old June 6th, 2013   #3
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I
Ok, now the question: Any idea what would use a ducted fan for a prop? (that is what it sounded like to me) Very high speed, ducted fan sound kind of like the old sound suppressed ducted fans we used to use in the old very large computer systems for cooling.

I did not see the aircraft. By the sound, It was flying low and (guess) about 300+ knots, west to east.
May not be an Osprey, as there are some other interesting developments in the US that I am aware of but not really following closely.

The Piasecki X-49A Speedhawk? The X-49A is a Sikorsky YSH-60F modified with wing and vectored-thrust ducted propeller for propulsion and control (which IMHO is a dead end developmental road). See: Piasecki X-49A Speedhawk flight tests - YouTube

Or could it be, the Sikorsky X2 (on which they may use to build the Sikorsky S-97 RAIDER)? But that does not have a ducted fan. See: Sikorsky - X2 Technology™ Demonstrator Final Flight Test 23 : 253 Knots (469 Km/h)- YouTube

Here's a link to the latest news: AVX joins Bell, Sikorsky/Boeing for Army's JMR-TD development. The concept art shows a coaxial-rotor compound machine, with ducted propellers at the side that is different from the S-97 concept art - not sure how far the JMR-TD is along on the design process.
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Old June 7th, 2013   #4
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There aren’t many planes that use ducted fans for propulsion. There is the British Edgley Optica and the Mississippi State University XV-11 Marvel but neither of these planes could make 300 knots. They’d be pressed to make 100!

There is however the German RFB Fantrainer which can get over 200 knots. There are still a few of these flying in Europe but I’m not sure about the USA.

http://www.secretprojects.co.uk/forum/index.php is the internet home for rare, unbuilt and secret aircraft.

But there has been and perhaps still is quite a bit of effort into super hush kits for turbofans. The Lockheed CL-1253 was a 1970 proposal for the USN's Silent Tactical Attack and Reconnaissance System (STARS) with podded turbofans. Designed to fly silent a few thousand feet over the Ho Chi Minh trail while dispensing nastiness onto the ground.

STARS: Lockheed CL-1253 : Subsonic VAMX derivative / STAR

As a tail stump left behind in Pakistan a few years ago has shown silent aircraft are not completely out of vogue.
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Old June 7th, 2013   #5
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Could it have been a V-22 Osprey.
Big blades whacking through the air?
Big blades do not turn that fast. Too keep the tips going supersonic this fan had to be small... blade length of no more than 20" to 24"... from the sound the blades were really spinning fast.

If the AD 150 was a single fan aircraft I could see it looking like.... also AD 150 (sorry they won't let me post the link, it's on a Wiki but it's top speed is 300knots+

If this was in the working model era I would have thought that would be what I heard.

Bit more explanation: What I heard would have been single fan. My speed guesstimate is based on the unblocked (except for trees) distance I heard it in, V transit time. Transit time is a guess, absolutely no more than 15 seconds. Just long enough to hear something "different", and put all my attention to it to try identify it, before a ridge blocked the sound.

Very high speed fan, my guess is that was passing about 1000' below and a mile south of my cabin. (I live on a mountain). Most definitely a single sound source, or a PERFECTLY synchronized dual sound source. (single engine driving two identical fans?)

To try to show why I say a single sound source, think what you hear in the case of a Kiowa verse the sound of a Chinook. Only problem with it being a known prop aircraft, VTOL, or a helicopter, is the transit time, Way too fast for anything I know of that is prop/fan driven short of a WWII fighter or equivalent. A 421 Cessna isn't even that fast (and we have one of those that does fly around here.)

Last edited by hermannr; June 7th, 2013 at 08:07 PM.
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