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Propfans

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posted on Sep, 6 2006 @ 10:56 AM
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Does anybody know why are they not used more often? So far I know the only one plane that should use them is the newest Antonov and it could be cancelled soon. I've read about them and it seems really nice and working concept. For those who don't know what it is it is a hybrid between turboprop and turbofan - they can reach speed similar to turbofans, but they have 30-35% lower fuel consumption and are much more effective at low altitude and speed.




posted on Sep, 6 2006 @ 11:09 AM
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Noise and fashion.

Thats pretty much it unfortunately, there are no technical reasons for not using them whatsoever.


Although with rising fuel prices, eventually airlines will have no choice but to consider manufacturer proposals using propfans.



posted on Sep, 14 2006 @ 06:44 AM
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Mainly fasion! most people think the propeller isn't cool. Personally, I would love to see propfans on aircraft. Even though I like some modern designs, I've always liked the way the propeller looks, especally the modern ones.

Tim



posted on Sep, 15 2006 @ 02:40 AM
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Military:
In terms of stealth you might as well stick a barn door on the plane.

Comercial:
Creates a noisier cabin environment.



posted on Sep, 15 2006 @ 03:50 AM
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Originally posted by ghost
Mainly fasion! most people think the propeller isn't cool. Personally, I would love to see propfans on aircraft. Even though I like some modern designs, I've always liked the way the propeller looks, especally the modern ones.

Tim

Fashion will not dictate which engines go on a plane. Many planes are still prop powered, even 70 seat ones


I think the main reason is maintenance costs, and if a prop flys off, it will be uncontained and cut the fuselage up pretty bad.

Also the Antonov flies 200km/h slower than most jets


[edit on 15-9-2006 by PisTonZOR]



posted on Sep, 15 2006 @ 03:56 AM
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There was slightly more than "fasion" involved.

The UDF (UnDucted Fan) GE developed was designed for tail-mounted engine applications. GE didn't know how to mount the prop fans at the front of the engine, and rear-mounted fans were incompatible with underwing mountings.

Commercial airliners were switching to underwing pylons for their engines, Boeing in particular lacked any aircraft that could carry the UDF GE-36. Implementing propfans would mean not just new engines, but an entirely new airframe, which was viewed as too great a risk.

The other problem is that turbofans have improved greatly since we last player around with propfans. GE-36 registered a 30% improvement, but that was over the F404 it was based on - a fighter engine I doubt was designed with fuel efficiency as first priority.

I'd be curious to see propfan performance compared to a modern "ultra-high bypass" engine like GEnx or Trent. UDF and UHB both gain efficieny based on a "bigger fan" relative to the engine's power. I suspect the difference in performance between the types would be much less than the 30% if we compared modern designs.

Add in the noise factor and risk of investing in a new design, and I'm not surprised this idea hasn't yet resurfaced even with increased fuel costs.



posted on Sep, 15 2006 @ 04:11 AM
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Sorry guys, the decision was mainly fashion (along with noise).


The An-70 has a cruise sfc of less than half that of the B767!

A propfan can also reach the high subsonic speeds of airliners.


I know for a fact a strong reason for the current regional jets all being... well jets is the 'modern look' of a ducted engine. Bull Gunston's 'The Jet Engine' covers it quite well.



posted on Sep, 15 2006 @ 05:50 AM
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Originally posted by gfad
Military:
In terms of stealth you might as well stick a barn door on the plane.


True! However, noone was suggesting a propfan powered B-2. It would more likely be used for transports and suppot aircraft. If you put it on something like a C-5 Galaxicy, it would boost the range and fule efficency quite a bit. Stealthy engines don't matter on a C-5, the thing already looks like a flying warehouse on radar!



Comercial:
Creates a noisier cabin environment.


Have you every heard of sound insulation?

Tim



posted on Sep, 15 2006 @ 09:30 AM
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Originally posted by kilcoo316
Sorry guys, the decision was mainly fashion (along with noise).


The An-70 has a cruise sfc of less than half that of the B767!

A propfan can also reach the high subsonic speeds of airliners.


I know for a fact a strong reason for the current regional jets all being... well jets is the 'modern look' of a ducted engine. Bull Gunston's 'The Jet Engine' covers it quite well.

It was not because of fashion! If you think that, please tell me why the Bombardier Q400 is used much more than CRJs on some routes?

The issue, was yes, noise, and maintainence. Also the 767 is old tech, compare it to GEnx. If you were Boeing, would you decide against having 30% less fuel burn against you're compeditor because of fashion?


Also tell us you're source for the SFC. Renember, MD80 engines are old tech, 767 engines are better, and genx have a SFC of 15% less than that. That would make the SFC of propfan comparable to the GEnx.

[edit on 15-9-2006 by PisTonZOR]

[edit on 15-9-2006 by PisTonZOR]



posted on Sep, 15 2006 @ 12:56 PM
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It doesn't matter if it was old tech, propfans are always more effective than comparable turbofans. Of course if you continue to develop them. The same is true about the regular propellers, but those cannot reach high speed and altitude. Really, I think the only problem is with noise, but at least for cargo aircraft it should be not a problem.



posted on Sep, 15 2006 @ 03:02 PM
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Originally posted by PisTonZOR
It was not because of fashion! If you think that, please tell me why the Bombardier Q400 is used much more than CRJs on some routes?

The issue, was yes, noise, and maintainence. Also the 767 is old tech, compare it to GEnx. If you were Boeing, would you decide against having 30% less fuel burn against you're compeditor because of fashion?


Also tell us you're source for the SFC. Renember, MD80 engines are old tech, 767 engines are better, and genx have a SFC of 15% less than that. That would make the SFC of propfan comparable to the GEnx.



Because that is what the airlines already have, thats what the pilots are trained on. I'm working with Bombarier right now, and I can tell you it is one of the key issues (alongside noise).



Firm orders for the CRJ family of regional jets - the most successful regional aircraft program in history - as of August 31, 2004 stood at 1,380 aircraft. Conditional orders and options could increase the program by a further 1,140 Bombardier CRJ Series aircraft.


A strong order intake in the last 18 months has resulted in an increase in the Q400 production rate. There is also keen interest in the 50-passenger Bombardier Q300 turboprop as demonstrated by Qantas Airways' order of seven Q300 in the last 10 months and a number of solid prospects for the future. As of August 31, 2004, the Bombardier Q400 firm order book stood at 114 aircraft, of which 85 had been delivered to 11 operators around the world.


press.arrivenet.com...

The increase in Q400 orders is a result of hiking fuel prices.


And YES, they did sacrifice, and continue to sacrifice massive fuel savings in the name of fashion (and noise). I told you the source for the sfc did I not? Bill Gunston's 'The Jet Engine'.

I have to make a small correction, the comparison was to the B 757. Anyway, the D-27 propfan is predicted to have a cruise sfc 0.286.



Anyway, the future seems to lie in ducted propellors, kind of a halfway house between UHBPR turbofans and propfans. They should allow a 20% or so reduction in sfc while still keeping noise levels down.



posted on Sep, 15 2006 @ 03:46 PM
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I believe there are more prop-driven planes than turbofan driven planes and this is why, because General Aviation expands to smaller aircraft too.

When you go to train to become a pilot, the very first plane you start on, will be a prop-driven aircraft, I know when I got to the airport all I see are propelor aircraft.

As a matter of fact, getting to a turbojet/turbofan aircraft is quite difficult because the flight characteristics are different than propellor driven, and as everyone starts on prop aircraft, well they have alot more ratings to get before they even think about jet powered aircraft. Prop aircraft are more efficient at lower alititudes than jet aircraft, which is the main reason why there are so many and still so popular as they are.

Believe it or not folks, C-5's, C-17's, F-15s, F-16's, F-22's aren't the only planes in the world, there are alot of prop driven aircraft out there, you just need to take a few trips down to the nearest airport, and I don't mean those big hubs.

Shattered OUT...



posted on Sep, 15 2006 @ 04:01 PM
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Personally, I used to love flying an Island Air Dash-8 interisland when I lived in Hawaii. They're smooth, and the noise lulls you into a nice nap during the flight.
Of course the lack of struts/shocks on the main landing gear makes for a bit of a rough landing, but hey, you can't have it all.
They started getting Q400s in March of this year.



posted on Sep, 15 2006 @ 10:35 PM
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Ok, thanks.

But still, it's not fashion that stopped propfans. I hope Boeing resurects the 717 and chucks propfans on the end. I got the information from my dads friend who used to work for GE


[edit on 15-9-2006 by PisTonZOR]



posted on Sep, 15 2006 @ 10:36 PM
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Don't count on it. The 717 didn't do well as a jet, so I don't see it doing very well as a prop.



posted on Sep, 16 2006 @ 02:03 AM
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Originally posted by Zaphod58
Don't count on it. The 717 didn't do well as a jet, so I don't see it doing very well as a prop.

People who had the 717 loved it, however the 737NG was around, Boeing marketed it more than the 717. The Embraer jets were also around which helped kill it.



posted on Sep, 16 2006 @ 06:06 AM
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I don't know if anyone remembers but the 717 (as the MD-90) was originally designed to be a propfan aircraft but was converted to jets because the noise issue was proving too difficult to overcome and there were no takers, at the same time Boeing was offering a propfan rival called the 7J7 and in appearance this was very similar to the Tu-334, but with propfans instead of jets, obviously.



posted on Sep, 16 2006 @ 09:20 AM
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The 717 just fit a market that too many other planes fit at the same time. It's not really long ranged enough for the longer haul carriers, and not really a great fit for the really short haul carriers. It's a great plane and I loved flying on it, but it didn't fit the carriers well.



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