Modern day propeller fighter - hypothetical

"John Bailey" wrote in message
...
On 2 Dec 2003 20:05:13 -0800, (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.

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.

Take one Kuznetsov NK-12MV turboprop giving 14,795 shp as used in
the
Tupolev 95 Bear. With four engines the Bear gave: 575 mph (925 km/h)
Ceiling: 39,370 ft (12000 m) For a single engine fighter, it should
be
able to cruise climbing straight up. An even more mind boggling
configuration would be two NK-12MV's in a twin boom design, a la the
P-38.

The real value of this design would be using the TU-95's transonic
counter-rotating propellers, which probably provide an upper limit
on
speed.


Those sorts of performances I think were achievable with piston
engines.

The Luft46 web site lists a few German pusher prop aircraft that were
projected as replacements for then current Lufwaffe aircraft.
Achieving as much as 584 mph on an ordinary 1750HP Jumo 213 V12 piston
engine seems to have been accepted.

This scimitar prop aircraft is one of the fastest at 584mph.
http://www.luft46.com/dornier/dop252.html

The advantage would be fuel efficiency and the lack of refractory
alloys needed for the engine. The cost of making high octane fuel is
exorbitant compared to make Jet fuel.

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

"Cub Driver" wrote in message
...

The question is are we capable of producing
superior prop aircraft than the great fighters of WWII and what
configuration would it take?

I'm not sure what the engine would be. Is there an off-the-shelf
turbine engine that could be tweaked to the war-emergency power
requirements of a fighter aircraft?

I'm not saying there is none! I haven't the faintest idea of what
the
capabilities of existing turbines might be. But note that the
horsepower of front-line fighters in WWII was more than doubled in
four years, as an example of wartime requirements. Also, lives were
cheaper in those days.

The Germans accepted a man-killer like the Me
163 into front-line service, and the Me 262 would also be
unacceptable
today, with its 10-hour engine life.

The engine entered service with an MTBO of 25 hours which was well
established. (about 16 missions) Manufacturing complaince and service
realities degraded this to 10 hours for a while. Still if I was an
Ju 88 pilot I'd prefer converting to the Jet than the Me 109 given
that my combat skills and the concentraion of allied aircraft.

Mean time between overhall was 25 hours not total engine life and was
a problem of lack of chromium and particularly nickel at one level and
at another level poor manufacturing quality control compliance. (This
made the biggest difference; the use of unskilled factory labour
versus technicians and tradesmen who did not need supervision or
detail instructions)

Injector burners were the most heavily consmed item but could be
easily replaced.

The 6 Combustion chambers were made of simple carbon steel coated in
aluminium and needed to be replaced at 25 hours.

Both the hollow air cooled tinadur and cromadure turbine blades were
removed at 25 hours, x-rayed and if OK replaced for a further 10
hours.

Theoreticaly engine overhaul life reached 60 hours in the latter model
s.

Earlier engines, the Jumo 004B1 had solid blades while the Jumo 004B4
had hollow aircooled blades and was more reliable. The first
experimental blades had lives of 4 hours to over 100 hours due to
manufacturing spread.

What the Jumo 004B lacked was a throttle bypass system to bypass
excess fuel as the compressor spooled up. The control system did rely
on RPM and pressure but this was inadaquete in cases of rapid throttle
movement. The over supply of fuel could raise combustion temperatures
by 200C which had the effect of burning through combustion chambers
and turbines.

The BMW 003A used on the Arado 234C and He 162 volksjaeger despite
lagging 9 months behined and actualy having its control system derived
from the Junkers model was more sophisticated in having a throttle
bypass system.

The annular combustion chamber on the BMW 003A lasted 200 hours, the
turbine could be removed, inspected and replaced in less than 2
hours, the engine did have a throttle limiting system. Unlike the 004
the engine did not need to be stripped down.

The Jumo 004C and Jumo 004D both entered production (for use in
prototypes) and had increased thrust of 1050 and 1100kg due to detail
refinements. In the case of the 004D this included duel zone
combustion to overcome the atomisation problems that cuased flameouts
at high altitude and idling. (These engines all entered production
but not service. A Jumo 004C apparently propelled an Me 262 to
584mph.)

Part of the problem the engineers faced was the fuel. Although
designed for running on the diesel based J2 fuel for reasons of
economy and safety this added a 2 stage startup initialy on a lighter
fuel as well as necesitating fuel systems that could cope.

Some Me 262 missions were flown with crude oil in the tanks. The
crude oil was refined only by centrifuge, then heated and pumped into
the tanks.





all the best -- Dan Ford
email:

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

(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?

Bizarre, hardly. Have you taken a look at the Beech Starship?

http://www.bobscherer.com/Pages/Starship.htm and
http://www.brunton.net/starship.html

Seems like that would be a reasonable starting point for such a fighter.
Advanced composite construction, modern avionics and flight controls, and
sexy as hell.

/------------------------------------------------------------\
| George Ruch |
| "Is there life in Clovis after Clovis Man?" |
\------------------------------------------------------------/

From: "The Enlightenment"

snip

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.

Dan, U. S. Air Force, retired

In article ,
"The Enlightenment" writes:
Those sorts of performances I think were achievable with piston
engines.

The Luft46 web site lists a few German pusher prop aircraft that were
projected as replacements for then current Lufwaffe aircraft.
Achieving as much as 584 mph on an ordinary 1750HP Jumo 213 V12 piston
engine seems to have been accepted.

Quite frankly, that's bat****.
cue the every 3 months lecture on the Speed/Power relationship for
the thrust of propeller driven airplanes.
To cut to the chase - a constnt power output engine, like a recip, or
the propeller side of a turboprop, produces less thrust the faster you
go. Assuming 85% propeller efficiency across the board, your 1750 HP
Jumo is producing 2790# of thrust at 200 mph, 1490# of thrust at 375
mph, and at 584 mph, 955# of thrust. (It's actually a lot worse than
that - the efficiency of the prop goes way down beyond about 450-500
mph at Sea Level.

This scimitar prop aircraft is one of the fastest at 584mph.
http://www.luft46.com/dornier/dop252.html

Even assuming that there are _no_ transonic effects on the airframe
(Which there will be), and two engines, the Equivalent Profile Area of
the drawing below is 3.55 sq ft. (That's Drag Coefficient * Reference
Area).
A P-51 works out to a profile area of about 4.66 ft.
This Dornier cattywampus is more that twice the size of a P-51.
The claims are rediculouss on the face of it. The SS Scientific Branch
might believe such horse****, but real life physics wins every time.


(And the Scientific Branch certainly _did_ believe such horse****.
They sent a specialist in Infrared Photography to Spitzbergen to
photograph the British Home Fleet at Scapa Floe through the Hole into
the Hollow Earth.)

The advantage would be fuel efficiency and the lack of refractory
alloys needed for the engine. The cost of making high octane fuel is
exorbitant compared to make Jet fuel.

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

And it wasn't operating at 85% efficency at that Mach Number, either.
The thrust numbers I posted above are best case.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster

(B2431) wrote:

From: "The Enlightenment"

snip

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.

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?

/------------------------------------------------------------\
| George Ruch |
| "Is there life in Clovis after Clovis Man?" |
\------------------------------------------------------------/

In article ,
George Ruch wrote:

(B2431) wrote:

From: "The Enlightenment"

snip

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.

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.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

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

--
Tom Schoene Replace "invalid" with "net" to e-mail
"If brave men and women never died, there would be nothing
special about bravery." -- Andy Rooney (attributed)

"Peter Stickney" wrote in message
...
In article ,
"The Enlightenment" writes:
Those sorts of performances I think were achievable with piston
engines.

The Luft46 web site lists a few German pusher prop aircraft that
were
projected as replacements for then current Lufwaffe aircraft.
Achieving as much as 584 mph on an ordinary 1750HP Jumo 213 V12
piston
engine seems to have been accepted.

Quite frankly, that's bat****.
cue the every 3 months lecture on the Speed/Power relationship for
the thrust of propeller driven airplanes.
To cut to the chase - a constnt power output engine, like a recip,
or
the propeller side of a turboprop, produces less thrust the faster
you
go. Assuming 85% propeller efficiency across the board, your 1750
HP
Jumo is producing 2790# of thrust at 200 mph, 1490# of thrust at 375
mph, and at 584 mph, 955# of thrust. (It's actually a lot worse than
that - the efficiency of the prop goes way down beyond about 450-500
mph at Sea Level.

You make one oversight though it is perhaps mine:

1 There are actualy 2 Jumo 213Js on this aircraft driving coaxial
contra-roting props so this automatically doubles the thrust.
2 I believe the Jumo specification is incorrect. Takeoff power is
1750 but with MW50 water methanol injection to allow overboost it is
someting like 2250hp. Likewise at high altitudes a Nitrous Oxide "Ha
Ha" system can bring power up to about 2150 hp because of the extra
oxgen in the NO and its anti-knock properties. Both systems were
fitted to the TA152

(for some reason I can get onto google but certainly the TA152H Jumo
213 could produce 2250hp I don't know if it was a J though)

Thus without boost an equivalent thrust of 900kg - 2000lbs is
available and that would presumably be maintained to quite a high
altitude where the atmoshere is at least half of sea level density and
probably less. With boost more like 2500lbs.

Incidently Anthony Kays book lists the following thrusts of the Jumo
004B1 jet as used in a Me262.

900kg sea level static
730kg seal level 559 mph (a test chamber result I suspect, German
test chambers were excellent and so good they were used by the allies)
320kg at 10000m




This scimitar prop aircraft is one of the fastest at 584mph.
http://www.luft46.com/dornier/dop252.html

Even assuming that there are _no_ transonic effects on the airframe

It DOES have swept wings and 584mph is not at the high end of
transonic. The AVA at Goetingen (German Equavalent to NACA) did a lot
of supersonic research in the mid 30s.

(Which there will be), and two engines, the Equivalent Profile Area
of
the drawing below is 3.55 sq ft. (That's Drag Coefficient *
Reference
Area).
A P-51 works out to a profile area of about 4.66 ft.
This Dornier cattywampus is more that twice the size of a P-51.
The claims are rediculouss on the face of it. The SS Scientific
Branch
might believe such horse****, but real life physics wins every time.

A pusher aircraft has less drag becuase there is no high velocity
airflow over the airframe that is turbulent to boot. This on its own
suggests higher speed.


(And the Scientific Branch certainly _did_ believe such horse****.
They sent a specialist in Infrared Photography to Spitzbergen to
photograph the British Home Fleet at Scapa Floe through the Hole
into
the Hollow Earth.)

Sounds like the one where a Jewish doctor cut of Hitlers testicals
that was circulated in the war.


The advantage would be fuel efficiency and the lack of refractory
alloys needed for the engine. The cost of making high octane fuel
is
exorbitant compared to make Jet fuel.

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

And it wasn't operating at 85% efficency at that Mach Number,
either.
The thrust numbers I posted above are best case.

85% for a scimitar shapped contra-rotating prop is good but I think
achievable.


--
Pete Stickney
A strong conviction that something must be done is the parent of
many
bad measures. -- Daniel Webster

In article ,
Nev wrote:

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?

Do you think the Embraer ALX and Pilatus PC-21 look like a
Piper PA48 Enforcer (only with nose gear and yes - I know
it's not really a Mustang)? If something like 4 x 20 mm is
enough, it seems that configuration works well. If you
want something like a Oerlikon KCA, GAU-8 or even Oerlikon
35/1000 a pusher prop might be indicated.
--
Urban Fredriksson http://www.canit.se/%7Egriffon/
A king and an elephant were sitting in a bathtub. The king said, "pass
the soap" and the elephant said, "No soap, radio!"