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Author Topic: Northrop/McDonnell Douglas YF-23 and EMD F-23  (Read 477773 times)

Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #135 on: January 01, 2008, 10:27:00 am »
Hmmm, maybe I do lost something very important. The AIAA Paper 84-2401 file you posted via quote is only a part of complete version so that display an amphibolous explain, could you send me a whole file?  8)
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Offline PaulMM (Overscan)

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #136 on: January 01, 2008, 10:50:04 am »
No requests for articles or books, please.

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Offline lantinian

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #137 on: January 01, 2008, 02:53:36 pm »
Quote
My point was that ATFs were limited to M2 and below by their fixed inlets,

It is my understanding of flight that an object does not necessary need variable inlets to travel supersonically. Most asteroids that enter the earths atmosphere do not have even aerodynamic shape, yet they travel trough it quite fast indeed. ;)

To end the joke with a reasonable and usefull comment I would say.

Variable geometry inlets allow a much more efficient flight at supersonic speeds to justify the extra complexity.
The ATFs however have a lot of excess trust available and can go over Mach 2 without problem. (reports say F-22 reaches Mach 2.4)

However, due to raised drag and raised temperatures ( stealth coatings have low temp limits) the YF-23 and now F-22 were not thought out to be flown at speeds above Mach 2 operationally (at least not for more than minute or two). The inlet designs were therefore designed to be most efficient at cruising speeds of Mach 1.5+

Further, some recent design innovations in this area, like the devertless inlet on the F-35 do allow even simpler design to perform well up to Mach 2.

Finally, the drawings available for the production F-23A (earlier in the tread) do suggest a similar divertless design with a fixed cone shape inside the inlet. Clearly the engineers have figured out that a inlet design that had an order of magnitude lower RCS but a little higher drag is of more value now if you can still reach Mach 1.5 at about 80% throttle setting.

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lantinian
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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #138 on: January 09, 2008, 08:41:22 am »
Some extra shots with details of YF-23 weapon bay [doors] with provisions for AIM-9 launcher and, of course, Paul Metz.
« Last Edit: January 09, 2008, 08:44:58 am by flateric »
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Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #139 on: January 09, 2008, 09:14:54 pm »
Good post Flateric!
Although only one bomb bay can be dimly seen, your post proved this pic.
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Offline Sundog

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #140 on: January 10, 2008, 10:02:26 pm »
Quote
My point was that ATFs were limited to M2 and below by their fixed inlets

If they were using 2-Dimensional shock structures and mechanics like 1960's era fighters, that would be true. However, the ATF designs used three dimensional shock structures which offer greater pressure recovery and they also used other technologies, such as porous materials and possibly fluidic controls to manage their shock structures which offer the ability to control the inlet flow without mechanical controls, thereby maintaining their L.O. properties over the speed range. It's been reported that the second YF-23 prototype with the GE variable bypass engines had a top speed of M=2.8+. I can't confirm that, it's only what was reported.

Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #141 on: January 11, 2008, 12:27:00 am »
Heard of M=2.3 for PAV-2, but figure seems to be not so exspressive to make it classified for 18 years...
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Offline lantinian

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #142 on: January 11, 2008, 02:40:58 am »

Quote
ATF inlet designs had the ability to control the inlet flow without mechanical controls
Thanks Sundog! Its good to learn something everyday. I allways though the inlet designs were a compromise betwen LO and Speed. Apparently not!

Quote
It's been reported that the second YF-23 prototype with the GE variable bypass engines had a top speed of M=2.8+.

It now makes sense in terms of available trust (1.5+ times more than F-15) and aerodynamics (Extensive area ruling, higher sweep angles and advanced inlets). However, I still doubt the max supercruise to have been more than Mach 2.1. At higher speed the supersonic cone will overlap the wing tips and that coupled with the aerodynamic heating will likely compromise the integrity of the LO coatings. Not to mention that the IR signature at front will rise enough to challenge the rear one, substantially increasing the range of hostile IR sensors.

Still, in terms of sustained speed it seams the production F-23A could have been just as much faster than YF-22 as YF-22 was over F-15. WOW!
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Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #143 on: January 11, 2008, 06:57:12 am »
 :o Over M2.8.......
Sundog must be a fans of US jet. ;D I love you!
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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #144 on: January 11, 2008, 10:10:22 am »
Bismaleimide (BMI) and carbon fibres (Hercules AS-4 fiber, mostly, in the case of YF-23) possess excellent mechanical properties in the 150 C to 232 C range.
Large sections of YF-23 airframe was made of carbon/BMI composites
If travelling at M=2.8-3.2 range SR-71 has lowest T at the center top/bottom of fuselage (the coldest area) of 250 degrees C, not talking of leading edges and chines with Ts in 315-340 C range...Canopy glass has about 300 C *after* landing! Northrop has a *great* problems at M=1.4-1.6 with engine cowls heating - and not aerodynamic, but from the engines core!
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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #145 on: January 15, 2008, 06:16:57 pm »
Where did you get the number as only 0.29 for F-22A or YF-22?
The correct calculation of fuel fraction is internal fuel capability/weight empty.
so even the internal fuel of F-22 down to 10 ton, the empty weight up to 17 ton. the fuel fraction also will be reach 0.59!! You put the wrong number not is on basic digit but on tens digit!

Fuel fraction is determined by whatever weight the aircraft happens to be divided by the weight of the amount of fuel in it. Any empty aircraft would have a fuel fraction of 0 unless it needs to have a certain amount of fuel onboard at all times for some kind of structural or maintenance reason.

Of course the most important fuel fraction figure is the aircraft in a typical combat mission configuration ready for engine start up and takeoff. One then takes this weight and divides it by the amount of fuel in the aircraft for this configuration. A subsequent fuel fraction of 0.3 typically means a good range for a conventional subsonic cruising aircraft. Because of the higher fuel burn demands of the ATF’s supercruise mission a higher fuel fraction was needed to provide a reasonable mission radius.

Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #146 on: January 15, 2008, 11:46:14 pm »
Well, if my understanding is right
Even though the fuel fruction should be internal fue/ empty weight + internal fuel
then Su27 = 9.3/(9.3+17) = 0.35
F22 = 10/(10+14.5) = 0.41
conclusion is that ff of Raptor is still higher than Flanker
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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #147 on: February 08, 2008, 07:21:12 am »
YF-23 manufacturing and 'Iron Bird' pics from West Coast Images 'YF-23 Black Widow II Declassified'
For Details and Ordering http://www.wci-productions.com/2.html
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Offline Sundog

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #148 on: February 08, 2008, 06:53:22 pm »
Quote
If travelling at M=2.8-3.2 range SR-71 has lowest T at the center top/bottom of fuselage (the coldest area) of 250 degrees C, not talking of leading edges and chines with Ts in 315-340 C range...Canopy glass has about 300 C *after* landing! Northrop has a *great* problems at M=1.4-1.6 with engine cowls heating - and not aerodynamic, but from the engines core!

1) How much of the heat/energy was transferred to the fuel? You do realize that the YF-23 most likely, like the F-22, circulated it's fuel under the skin to absorb the heat from high temperature flight.

2) Just because an aircraft "can" supercruise at a very high speed, I never stated the amount of time it could operate at that speed. For instance, the ATF design specs said it needed to supercruise for one hour. I don't remember if that was M=1.5 or slightly higher (the specs, not the actual capability). The aircraft don't heat up immediately. It takes time to get there.

3) As for the heating of the engine cowls, that tells me they had insufficient cooling around the engines. That really isn't surprising in a prototype. That still doesn't mean it's top end speed was immediately limited.

Quote
Sundog must be a fans of US jet.

Actually I'm a fan of all aircraft. Fortunately for me, I still remember many of my lessons from my compressible aerodynamics courses.

Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #149 on: April 23, 2008, 12:10:28 pm »
Quote
YF-23 would undergo subtle changes if it wins competition.
Source: Defense Daily
Publication Date: 14-JAN-91

The Northrop/McDonnell Douglas YF-23 Advanced Tactical Fighter (ATF) full-scale development production
aircraft would undergo some subtle changes in configuration from the prototype design if the Air Force chooses
it for its air-superiority fighter, YF-23 Program Manager Thomas Rooney said last week.

YF-23 engineers, after reviewing test flight information, decided to make changes in the airframe to improve
the flying quality and low-observable signature of the aircraft, Rooney said.

Among the most obvious changes, the two distinct boxy humps, where its two engines are housed, will be
smoother.
With the advent of a down-select the aircraft will be tailored to fit one engine type rather than two.
General Electric and Pratt & Whitney are locked in competition for the ATF engine contract, while the
Lockheed/Boeing/General Dynamics team is competing with the Northrop team for the airframe contract.
Rooney said the aircraft inlet cell will also be changed slightly to reduce the aircraft's radar cross-section. "The
change has been tested on a full-scale model," Rooney said.

In addition, the trailing edge of the aircraft's stabilizers will be changed slightly, altering their intersection with
the aft deck of the fighter, Rooney said.

The prototype aircraft utilized a greater percentage of titanium metal in its wing structure because the
prototype manufacturers had "problems with the scheduling and did not want to risk doing the substructure of
the wing with composites because they had more experience with the use of titanium structures," Rooney
said. Approximately 50 percent of the YF-23 production model structures will be composites. The aircraft will
be in the 55,000 pound weight class, according to Rooney.

Northrop Unconcerned About Missile Firings
Rooney said his team was not concerned with the Lockheed team's decision to fire Sidewinder and AMRAAM
missiles, which he says were not a requirement of dem/val. "We make a list of what we feel is important and
we didn't share our list with Lockheed ... and they didn't share their list with us," he said. "We didn't think that
launching a very mature missile at seven-tenths Mach in level flight had any meaning whatsoever. (We) were
concerned about ... the environment in that weapons bay at very high speeds."
Test Pilot Paul Metz said that to a less experienced pilot, the opening of the bay doors on the YF-23 would
have gone unnoticed in the cockpit, but he noticed acoustic levels were a little higher than anticipated. Metz
said small adjustments to the spoiler corrected the problem.

Regarding news that Lockheed had displayed its YF-22's ability to attack from a 60 degree angle, Rooney said,
again, that Northrop decided that a 25 degree angle of attack was all that was needed in dem/val.
Metz said the YF-23 could come through any angle of attack "even backwards." He said the aircraft can regain
control out of zero airspeed but it would have to fall to pick up the speed again. "No matter where it's at or
oriented it will come out and start flying," Metz said. This airplane, as designed, has the best high angle of
attack and spin characteristics of any airplane ever built by McDonnell Douglas or Northrop." Metz said the
YF-23 topped T-38s, F-5s, F-15s and F-18s, which are considered premier high angle of attack airplanes today.
« Last Edit: April 23, 2008, 12:12:56 pm by flateric »
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works