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Author Topic: Northrop/McDonnell Douglas YF-23 and EMD F-23  (Read 464130 times)

Offline Trident

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #105 on: December 17, 2007, 05:41:18 am »
For instance the B-2 has some sort of laser on the back end.  My guess it's a IIR "dazzler" but could be something more mundane like a laser communication link.

Laser comms would be impractically short-ranged for a strategic stealth bomber that spends most of its mission alone tough? My guess would be an early DIRCM as well.

Offline PaulMM (Overscan)

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #106 on: December 17, 2007, 03:19:43 pm »
http://www.ophir.com/contrail%20detection.htm
Quote
Pilot Alert System:  designed, manufactured, tested, certified and maintained by Ophir.

Condensation trails (contrails) form when aircraft engine exhaust rapidly cools to form ice crystals.  Contrail formation is dependent upon the atmospheric temperature and humidity, aircraft engine type and thrust setting, and aircraft fluid dynamics.  Ophir uses Random Modulated Continuous Wave (RMCW) laser radar for the early detection of aircraft contrails .

The Pilot Alert System (PAS) is a light detection and ranging (lidar) system designed for detection of contrail formations behind the B-2 Bomber; it discriminates clouds from contrails.

 The PAS uses a Random Modulated Continuous Wave (RMCW) transmission which allows for processing of returned signals below the ambient light levels. RMCW lidars have low peak power emission compared with pulsed lidars. The RMCW technique is based on the continuous emission of “randomly” modulated low-power laser light. The random modulation follows an m-code (a bit sequence arranged in a non-repeating pattern).

Could this be it?
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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #107 on: December 17, 2007, 03:28:01 pm »
One of these square stuffies...
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stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline TinWing

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #108 on: December 17, 2007, 03:56:00 pm »
Back to the OT:Super Hornet performance. It was known since it's development the Super Hornet would not have the capability of the Eurofighter. In fact, the most capable version of the SH studied was the canard/arrow wing variant which itself only possessed 90% of the performance of the Eurofighter.

You fail to mention that the Eurofighter has even less fuel capacity than the first generation Hornet.

The Super Hornet's primary reason for being is increased fuel capacity over the first generation Hornet, pure and simple.

I would question the value of "supersonic maneuverability" outside of a very narrow defensive context, something that seems largely worthless in modern expeditionary warfare where aerial threats are for the most part absent.

As I've said before, all things being equal, a conventional tail aircraft has better high AOA control than a canard aircraft in certain parts of the envelope. The main reason for going with canards is you can make a smaller airframe for a given mission then a conventionally tailed aircraft, which means lower weight and, therefore, lower cost.

Hypothetically, you could also get more fuel into a canard delta as compared to a conventional tailed design.  In practice, the opposite seems to be true.


Offline F-14D

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #109 on: December 17, 2007, 10:10:30 pm »
Back to the OT:Super Hornet performance. It was known since it's development the Super Hornet would not have the capability of the Eurofighter. In fact, the most capable version of the SH studied was the canard/arrow wing variant which itself only possessed 90% of the performance of the Eurofighter.

You fail to mention that the Eurofighter has even less fuel capacity than the first generation Hornet.

The Super Hornet's primary reason for being is increased fuel capacity over the first generation Hornet, pure and simple.

I would question the value of "supersonic maneuverability" outside of a very narrow defensive context, something that seems largely worthless in modern expeditionary warfare where aerial threats are for the most part absent.




The function for the increased internal fuel in the Super Hornet is to supply the fuel needed by its F414s, which have a higher fuel burn that the F404s in the F/A-18A-C.  The Super Hornet's increase in range was initially attributed to its lower drag and fuel use in the "non cruise" portions of a mission and its larger external fuel tanks.  Some of that drag reduction has been lost in actual service.  It turns out that the pylons on the production Super Bug have to be angled out, possibly for safety reasons when launching powered ordnance off the inner pylons, and do not align with the airflow.  This increases drag, especially when they're loaded.  As far as the larger tanks, the F/A-18C/D could have used them as well.  According to some sources, the Super Hornet may only exceed the Hornet's unrefueled radius of action just in the ground attack mission and then only by 64nm.  As an aside, the longer legged Super Hornet still does not have the range that was supposed to be delivered by the original F/A-18A. 

As far as supersonic maneuverability goes, its value is that if you are traveling at a higher speed, you can compensate for your larger radius of turn by having good maneuverability at those higher speeds.  For example, in WWII the P-51's turn radius was smaller than that of the Me-262.  However, the 262 had good maneuverability at its speed, so what it could do was use its superior speed to fly around its larger radius turn faster than the -51 could fly around its tighter turn, which allowed the 262 to stay on the -51's tail at the completion of the maneuver.  Same principle would apply to a supercruising vehicle, vs a transonic aircraft, plus it would be useful when encountering an aircraft capable of matching your speed performance.  Speed is life!
« Last Edit: December 19, 2007, 05:52:47 pm by F-14D »

Offline LowObservable

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #110 on: December 19, 2007, 01:06:33 pm »
Fuel fraction (usually considered in terms of fuel/mass with full internal fuel and no weapons) is a big factor in range, of course. But there's also engine cycle, and the degree to which you need to use afterburning. The F-22 has near-pure-jet engines (bad) but does not need A/B except to accelerate or for extreme maneuver (good).
Since the Super Hornet is basically a scale-up of the Hornet, with about the same internal fuel fraction and slightly lower-bypass engines, the main reason that the range is better is indeed its external tanks. Both the Classic and the Super can carry 480 USG tanks under the wings, but the Classic can only carry a 330 USG tank centerline and the Navy never wanted to mix tanks.
Finally, general design and configuration makes a difference in drag with big external loads. Supposedly, for example, the Typhoon is reasonably efficient and flies well with a large load, which gives it a better range than (say) an F-16.

Offline Sundog

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #111 on: December 19, 2007, 07:47:57 pm »
However, part of the reason for the F-22s low bypass ratio engine is also due to it being optimized for supersonic cruise, versus the higher bypass turbofans which aren't. I think the biggest problem was they, LM,  either thought advanced technology would limit their weight growth into production or they simply underestimated how much weight the Raptor would gain going into production. Or was it a case, as so often happens, where the USAF ended up making L-M put more into the package as it transitioned from a development aircraft to a production aircraft?

Offline Berekhat

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #112 on: December 19, 2007, 11:29:13 pm »
Unclassified USAF documents give it 20,650 pounds internal and up to 15,865 pounds external.

Rosdivan, one of the best pdf files I've seen in the last years) Thanks a lot!

Yes, absolutely fascinating. Thank you as well.

However, can anyone tell me why, on page 41, it seems to indicate that WOOL is a major component of the F-117?  I hope it's being used as a blanket :) term for all the fibres listed below? This seems a good explanation, but they also go to the extent of suggesting the section refers to "Fibres, Natural and synthetic"

Have we found the real secret of stealth? :P
« Last Edit: December 20, 2007, 12:19:11 am by Berekhat »

Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #113 on: December 26, 2007, 01:12:59 am »
Just to talk a bit more about what a F-23A might have meant one of the most significant failings of the F-22A is its failure to meet the requirement for fuel for effective supercruising as established by the Advanced Tactical Fighter (ATF) program. ATF required a fuel fraction of 0.39 or at least 0.35 to have enough fuel to power the engines (F119 or F120s) for enough super cruising. F-22A only has a fuel fraction of 0.29 significantly reducing the range it can supercruise. This makes its supercruise capability just a lower engine IR signature way of dashing at supersonic speeds or reduces radius from the planned 800 NM to the actual 410 NM. Considering the YF-23 is a bigger plane than the YF-22 and has significant area ruling is it feasible that an F-23A could have had the higher fuel fraction and less supersonic drag required to meet the original ATF supercruise requirement?

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!

.......
As I've said before, all things being equal, a conventional tail aircraft has better high AOA control than a canard aircraft in certain parts of the envelope. The main reason for going with canards is you can make a smaller airframe for a given mission then a conventionally tailed aircraft, which means lower weight and, therefore, lower cost.
......

My dear friend:
you'd better know what was you said equal factually is dissimilar.
foreplan could be smaller than horizontal stabilizer so the structual weight will be reduced.
foreplan will give a smaller balanced drag than conventional horizontal stabilizer, no matter where the barycenter you put.
the area of delta wing adapt to the foreplan will be bigger than conventional layout so give more lift the maneuver needed.
« Last Edit: December 26, 2007, 01:34:27 am by rousseau »
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Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #114 on: December 26, 2007, 01:36:19 am »
Here is what I modified YF-23 drawing, it will be more acceptable.
 :D
« Last Edit: December 26, 2007, 01:40:28 am by rousseau »
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Offline robunos

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #115 on: December 26, 2007, 01:17:50 pm »
]

Yes, absolutely fascinating. Thank you as well.

However, can anyone tell me why, on page 41, it seems to indicate that WOOL is a major component of the F-117?  I hope it's being used as a blanket :) term for all the fibres listed below? This seems a good explanation, but they also go to the extent of suggesting the section refers to "Fibres, Natural and synthetic"

Have we found the real secret of stealth? :P
[/quote]

am i right in thinking that the RAM covering on the F-117 is a kind of fabric? i seem to remember seeing some news footage of the F-117 brought down in kosovo, that showed pieces of fabric hanging loose from the wreckage of the wings. also, wasn't this stuff also supposed to be impregnated with all the nasty chemicals that caused the labour problems at lockheed?

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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #116 on: December 26, 2007, 01:43:58 pm »
I remember pretty good coverage of RAM materials range in Jay Miller's Aerofax Extra F-117 book, and yes, fibres and wool were there in the list.
« Last Edit: December 26, 2007, 01:48:20 pm by flateric »
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Offline pometablava

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #117 on: December 26, 2007, 02:40:00 pm »
Merino is high quality spanish wool :)

Offline Sundog

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #118 on: December 26, 2007, 06:46:10 pm »
Quote
My dear friend:
you'd better know what was you said equal factually is dissimilar.
foreplan could be smaller than horizontal stabilizer so the structual weight will be reduced.
foreplan will give a smaller balanced drag than conventional horizontal stabilizer, no matter where the barycenter you put.
the area of delta wing adapt to the foreplan will be bigger than conventional layout so give more lift the maneuver needed.

As I've stated before, canard aircraft tend to be lower cost, because they tend to have lower weight, for the mission, precisely because you don't need the tail structure that a conventional aircraft requires.

However, most modern fighters are unstable. As such, the canard is usually sized to push the nose down at high alpha. That means the canard is working against the wing. Whereas with the conventional tail it provides lift to keep the nose down in the same regime. As such, it turns out there are areas of the envelope where the canard can't trim the aircraft as effectively because the conventional tail offers advantages in sizing in this part of the regime. This is one of the reasons why Lockheed's F-35 went from a canard design to a conventional tail. There are other areas of the envelope where the conventional tail is better as well.

However, for many nations, cost is the number one driver, which was one of the primary design drivers for all of the new European Fighters having been built as canards instead of conventional tail configurations.

Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #119 on: December 26, 2007, 08:46:00 pm »
…….
However, most modern fighters are unstable. As such, the canard is usually sized to push the nose down at high alpha. That means the canard is working against the wing. Whereas with the conventional tail it provides lift to keep the nose down in the same regime. As such, it turns out there are areas of the envelope where the canard can't trim the aircraft as effectively because the conventional tail offers advantages in sizing in this part of the regime. This is one of the reasons why Lockheed's F-35 went from a canard design to a conventional tail. There are other areas of the envelope where the conventional tail is better as well.
.......

 ??? Did I lose someithing in the conventional tail offered? What's the advantage compare with the foreplan? You keep nose down, I keep nose down either.!  :P ::) 8)
The key to any great story not is who or what, when or where, but why