Modern day propeller fighter - hypothetical

George Ruch wrote in message . ..
(Nev) wrote:

Some of the latest developments in propeller aircraft has fascinated
me. It also brought up an interesting hypothetical question; mostly
when reading about modern day warbird replicas.

With relatively easily available technology off the shelf (no rail
guns or laser cannon please). Lets say a reasonable development budget
of oh say $300 million. The question is are we capable of producing
superior prop aircraft than the great fighters of WWII and what
configuration would it take?

[snip]

If we were to design a new prop, gun armed aircrafy would it
essentially look pretty similar to a carbon fibre, turbo-prop P-51
Mustang or would it be some bizzare split wing, dual rear engined
travesty?

Uh, it WAS a modernized Mustang- the Piper Pa-48 Enforcer of the '80s:

http://www.aerofiles.com/piper-pa48.jpg

.... and rejected too...

Rob

(Nev) wrote in message m...
Some of the latest developments in propeller aircraft has fascinated
me. It also brought up an interesting hypothetical question; mostly
when reading about modern day warbird replicas.

With relatively easily available technology off the shelf (no rail
guns or laser cannon please). Lets say a reasonable development budget
of oh say $300 million. The question is are we capable of producing
superior prop aircraft than the great fighters of WWII and what
configuration would it take?

To keep the discussion relatively focused we'll put in a couple of
rules:

1. Mission: Air superiority/dominance during WWII. Land based. It
should be able to clear the skies of any and all opposition at all
ranges and altitudes.

2. Must be a propeller aircraft.

3. Only armanent allowed are guns/cannons. No guided missiles. I guess
dumb firing rockets will be ok since they were used during WWII.


With the above two exceptions all of modern technology is allowed to
be used for example composite materials, radars, titanium armour,
fly-by-wire (will dynamic instability benefit the agility of a prop
plane?) advanced aerodynamic configurations (rear mounted engines). To
make matters really intesting helicopters are fine. Just as long as
the driving force isn't a jet.

If we were to design a new prop, gun armed aircrafy would it
essentially look pretty similar to a carbon fibre, turbo-prop P-51
Mustang or would it be some bizzare split wing, dual rear engined
travesty?

About 15 yrs ago BAe messed around with a project called SABA ('small
agile battlefield aicraft') one of the designs touted was a v.
lightweight pusher UDF propellor craft with about a 2 ton warload.
Looked pretty cool. I think it was mainly an anti-tank craft designed
to fill the void between attack helicopters and full-blown ground
attack aircraft.

David

On Thu, 04 Dec 2003 02:07:05 +1100, wrote:

John Keeney wrote:

snip

I'ld guess you'd end up with an all weather plane between a P-38
and P-61 in size. Likely twin turbo prop to free up the center
line for radar and the gun.

A couple of alternatives for the centerline gun

- Through the prop hub as per WWII engine mounted guns (wasn't the original
idea for a 20mm Birket/hispano like this from WWI?).

- Rear engine as per some studies for CAS in the 80s, BA?

Or both as per Dornier 335, hmmm 2 x Bear engines (15,000hp each) might be a
bit much.

I imagine it might be a bit large too :-)

"Thomas Schoene" wrote in message
link.net...
George Ruch wrote:

I remember what may be the same picture, a DC-9 fitted with a
high-bypass turbofan, and multiple scimitar-shaped fan blades
extending from the first-stage fan. Damned if I can find it now,
though. Nothing like it so far on the NASA Dryden site. Any other
ideas?

They called in an unducted fan or ultra-high bypass turbofan.

Pictures:

http://www.b-domke.de/AviationImages/Rarebird/0809.html

http://www.nurflugel.com/Nurflugel/NASM/Img0052.jpg

Russian prop benders were on site for the program. The engine saves about
23% of fuel compared to regular high bypass engines, of the time. (pre
tripple spool compressor)

On Thu, 04 Dec 2003 16:37:38 GMT, Scott Ferrin
wrote:


Or both as per Dornier 335, hmmm 2 x Bear engines (15,000hp each) might be a
bit much.

I imagine it might be a bit large too :-)

Make for interesting an interesting piece of flying boom refuelling also.


greg

--
In the beginning. Back in nineteen fifty-five
Man didn’t know about a rock ’n’ roll show
And all that jive.

I recall seeing GE tested scimitar shaped pusher prop engines, I think
it was on a 727.

I seem to recall it being on the right engine of a DC-9. I wonder what became
of that idea.


"Unducted fans" or "propfans" were, I believe, tested on both a 727
and an MD-80. See for instance

http://www.jsc.nasa.gov/er/seh/profan.html (contemporary article from
midway through the program)


http://www.aerospaceweb.org/question...on/q0067.shtml (survey
article; pix)


http://www.aviation-history.com/garb...g/udf-2_f.html


The goals were, I think, a combination of fuel efficiency and some
internal simplifications.


I'm not exactly sure why they aren't much in use. Hypotheses I've
read include greater risk to the passenger cabin from uncontained
failures (I wonder if it is coincidence that both the testbeds were
the sort of jets with aft-mounted engines); undesirable "propeller"
image; noise; and parallel improvements in high-bypass turbofans of
the usual ducted design.

Cheers,
--Joe

About 15 yrs ago BAe messed around with a project called SABA ('small
agile battlefield aicraft') one of the designs touted was a v.
lightweight pusher UDF propellor craft with about a 2 ton warload.
Looked pretty cool. I think it was mainly an anti-tank craft designed
to fill the void between attack helicopters and full-blown ground
attack aircraft.

David

Sounds a lot like the Rutan ARES.


Ron
Pilot/Wildland Firefighter

"Ad absurdum per aspera" wrote in message
om...
I recall seeing GE tested scimitar shaped pusher prop engines, I
think
it was on a 727.

I seem to recall it being on the right engine of a DC-9. I wonder
what became
of that idea.


"Unducted fans" or "propfans" were, I believe, tested on both a 727
and an MD-80. See for instance

http://www.jsc.nasa.gov/er/seh/profan.html (contemporary article
from
midway through the program)



Thanks for these links. They all seem to think that a Mach 0.85 for a
scimitar blade contra-rotating coaxial "prop-fan" is possible and
indeed fuel efficient. Given that there was in a German 1940s study
suggesting 584 mph with twin piston engines I think its fairly
believable. I find the idea of a Mach 0.85 diesel or spark ignition
engine fascinating.

There is also the Soviet An 70
http://www.geocities.com/CapeCanaver...5/antonov1.htm I would be
interesting to read what the Russian desginers thought that they
gained with this designe of a straight jet or prop. I know that a
C-17 got bogged at a Sarajevo airport on a bit of wet grass and that
this lack of grunt is due to the use of jets instead of props.

Either way the Russians are ready to go apparently!

Another fascinating possibility is the use of SOFC (Solid Oxide Fuel
Cells). Many people beleive these will match piston engines in cars
in terms was weight. If turbo supercharged they should have an
amazing efficiency of 85%. They opperate at 800C at which point the
metal oxide membranse can conduct oxygen ions (instead of hysrgen
ions) and thus burn hydrocarbon fuels. The high temperature (still
only 1/3rd that of a pertrol engine) means that no catalyst is needed.
They are running in the lab at 60% efficient unburdened but becuase
they exhaust at 800-1000C they can be trubo-supercharged and excess
shaft power extracted.

These SOFCs should achieve the same power to weigh ratio of petrol
engines and thus be able to propell aircraft. Potentialy their engine
and cell life will be so high that they compete with gas trubines.
They would require only modes cooling and would require light
propellors since no piston torgue vibarations would be present.



I'm not exactly sure why they aren't much in use. Hypotheses I've
read include greater risk to the passenger cabin from uncontained
failures (I wonder if it is coincidence that both the testbeds were
the sort of jets with aft-mounted engines); undesirable "propeller"
image; noise; and parallel improvements in high-bypass turbofans of
the usual ducted design.

Cheers,
--Joe

I think there were some noise issues (not major), blade safety I
think could be handled (the scimitar shaped much add unusual
stresses), then there is the issue of gear boxes. These are high
maintain items. (The only geared turbo fan in sevice is that unit
(Allison) on the BAE avro regional/ BAE146 series jet I think)

It will be interesting to see if Pratt+Whitney's PW8000 geared
turbofan for airbus changes the anti-gearbox mindset.










http://www.aerospaceweb.org/question...on/q0067.shtml (survey
article; pix)


http://www.aviation-history.com/garb...g/udf-2_f.html


The goals were, I think, a combination of fuel efficiency and some
internal simplifications.

On Wed, 03 Dec 2003 23:11:57 -0700, George Ruch
wrote:

I remember what may be the same picture, a DC-9 fitted with a high-bypass
turbofan, and multiple scimitar-shaped fan blades extending from the
first-stage fan. Damned if I can find it now, though. Nothing like it so
far on the NASA Dryden site. Any other ideas?

We put ours on the spine of the Jetstar and drove it with bleed air.

That DC-9 you recall probably belonged to GE, which has a test
facility in Mojave.

Mary

--
Mary Shafer Retired aerospace research engineer

Chad Irby wrote:

In article ,
George Ruch wrote:

(B2431) wrote:

From: "The Enlightenment"

snip

I recall seeing GE tested scimitar shaped pusher prop engines

[snip]

I remember what may be the same picture, a DC-9 fitted with a high-bypass
turbofan, and multiple scimitar-shaped fan blades extending from the
first-stage fan. Damned if I can find it now, though. Nothing like it so
far on the NASA Dryden site. Any other ideas?

The one thing I can remember about the program was that the suckers were
too loud to fly over most cities in the US.

Probably so. Something like flying next to a TU-95 (migraine headache
number 43, or so I've heard).

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