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Old 05-07-2011, 05:20 AM   #4906
davsato
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noise stealthy helicopter, possibly. but radar stealthy? with a giant rotating fan on the top, no. to mask b1b,b2,f117 from radar reflecting you have to bury rotating assys, ie engines, behind lots of stuff. its why the b1 cant do mach2 anymore, the engines are strangled with 's'shaped intakes
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Old 05-07-2011, 12:52 PM   #4907
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its why the b1 cant do mach2 anymore, the engines are strangled with 's'shaped intakes
Actually the no Mach numbers restriction on stealth aircraft comes from the problem of what exceeding the speed of sound does to the radar paint itself. The pressure wave creates a spike that cannot be masked, thus stealth aircraft do not exceed Mach 1 almost by definition (and please, let's not get into a theoretical discussion of why no one has ever actually seen a Aurora ).

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Old 05-07-2011, 02:29 PM   #4908
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agree, but the B1B doesnt have any of that stuff. it can actually do mach1.25ish but thats at altitude, not what the plane is about any more. and i saw an aurora just the other day, in the model shop revell do a kit so there.

back to the helos! future rotary wings, any ideas or are they stuck in a rut like brass cartridges?
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Old 05-07-2011, 03:33 PM   #4909
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agree, but the B1B doesnt have any of that stuff. it can actually do mach1.25ish but thats at altitude, not what the plane is about any more. and i saw an aurora just the other day, in the model shop revell do a kit so there.


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back to the helos! future rotary wings, any ideas or are they stuck in a rut like brass cartridges?
A lot of it gets back to basic helicopter aerodynamics - especially as it relates to the rotor system and rotor blades in general. There are (currently) practical limits as to how fast you can spin the rotor system before the more than just the blade tips to supersonic. The whole dynamic of transonic flight really messes with the control and lifting surfaces. Getting part of the system supersonic and part subsonic makes for some really interesting math and pressure studies. Speed in helicopters is really limited by transonic/supersonic flight dynamics.

Again, function dictates form when it comes to helicopters, possibly more so than with fixed wing aircraft. You can reduce the radar signature only so much with an angled body as opposed to a rounded one (think AH-64 or RAH-64 vs original AH-1 or UH-1). Attack helicopters are easier to make stealthy than troop carrying or cargo helicopters due to their mission requirements.

I've been away from the design and futures environment for a few years now, so I really don't know what's on the drawing boards. But, I do have a friend who does work in that environment and he give no indication of anything revolutionary, only evolutionary.


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Old 05-07-2011, 06:31 PM   #4910
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The X2 by Sikorsky is pushing the top speed number up significantly.
It uses counter rotating coaxial blades to circumvent the retreating blade stall issue. They have a pusher prop on the tail, so the main rotor can supply lift, and the pusher supplies the forward thrust.

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Old 05-07-2011, 09:55 PM   #4911
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The X2 by Sikorsky is pushing the top speed number up significantly.
It uses counter rotating coaxial blades to circumvent the retreating blade stall issue. They have a pusher prop on the tail, so the main rotor can supply lift, and the pusher supplies the forward thrust.
Although it did not have the counter rotating coax blades the original Chyenne also had the pusher prop.



When fist flown publicly on 12 December 1967 (first test flight was 22 September that same year) the Chyenne (AH-56) was already pushing 200MPH.

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Old 05-07-2011, 10:25 PM   #4912
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Old 05-08-2011, 12:02 AM   #4913
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Originally Posted by jdgretz View Post
(and please, let's not get into a theoretical discussion of why no one has ever actually seen a Aurora ).

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I saw one once NW of Palmdale. A missle leaving smoke rings. Wierdest thing I ever saw in the air!
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Old 05-08-2011, 12:26 AM   #4914
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I saw one once NW of Palmdale. A missle leaving smoke rings. Wierdest thing I ever saw in the air!

Sounds more like a pulse jet.
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Old 05-08-2011, 09:15 AM   #4915
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While I think it's really cool.

I have no idea what anyone would use it for.

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Old 05-08-2011, 10:10 AM   #4916
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While I think it's really cool.

I have no idea what anyone would use it for.

Certainly not executive transport. They would have to wait till shutdown to exit the aircraft.
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Old 05-08-2011, 11:34 AM   #4917
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The X2 by Sikorsky is pushing the top speed number up significantly.
It uses counter rotating coaxial blades to circumvent the retreating blade stall issue. They have a pusher prop on the tail, so the main rotor can supply lift, and the pusher supplies the forward thrust.

thats cool, ive never seen that before. contra rotators would also be smaller diameter for the same lift, which means tip speed reduces
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Old 05-08-2011, 11:54 AM   #4918
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Certainly not executive transport. They would have to wait till shutdown to exit the aircraft.
Or even military, way too easy to have anyone or anything get caught in this turbo props.
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Old 05-08-2011, 12:26 PM   #4919
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Or even military, way too easy to have anyone or anything get caught in this turbo props.
I think he means, executives believe they are too important to wait for the OK from the pilot to leave the aircraft.
Soldiers will follow orders.
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Old 05-08-2011, 12:31 PM   #4920
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Or even military, way too easy to have anyone or anything get caught in this turbo props.
Do those props need to be running to land?
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