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Author Topic: Northrop/McDonnell Douglas YF-23 and EMD F-23  (Read 513027 times)

Offline F-14D

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #120 on: December 27, 2007, 01:02:16 pm »
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?

You know,  although the YF-23 looked dramatically larger, in reality it was only three feet longer than the YF-22, had the same wingspan and wasn't as tall.  Interestingly, although it could carry more internal fuel, its empty weight and normal operating weigh was actually less. 

Offline sferrin

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #121 on: December 27, 2007, 01:07:55 pm »
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?

You know,  although the YF-23 looked dramatically larger, in reality it was only three feet longer than the YF-22, had the same wingspan and wasn't as tall.  Interestingly, although it could carry more internal fuel, its empty weight and normal operating weigh was actually less. 

I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it.  You could show movies on the YF-22's vertical tails.
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Offline F-14D

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #122 on: December 27, 2007, 01:24:05 pm »
he production version of he Raptor would be just under that

What I find interesting is how the production version of the F-23 would have had half shock cone inlets instead of the 3D oblique shock inlets and how they moved the engines closer together.

 Was this really planned for production F-23s, or were these features of the proposed "F/B-23" of a few years back (visible on the model)?   The cones could also indicate that higher speed was wanted for this latter mission, both the F-22 and F-23 designs top speeds being limited by their fixed inlets.  If for strike reason a higher penetration speed was deemed Worth the complexity, they could be engineered in and the top speed would rise.  This is the reverse of what was done on the F-14D.  There, the aircraft was capable of speeds around M2.5.  However, Navy decided that that extra speed wasn't worth the maintenance expenses.  So, although the D have variable intake ramps they were deactivated, limiting operational Ds to M1.88-2.0. 

  Similarly do we know that production F-23s would have relocated the engines (a major redesign), or was this also something from the F/B-23, a;though in the latter case this may have just been how it appeared given the F/B's expected even larger weapons bay. 

  I, for one would be interested to know. 

Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #123 on: December 27, 2007, 01:46:51 pm »
Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.
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Offline sferrin

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #124 on: December 27, 2007, 01:49:40 pm »
Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.

BMI is better than aluminum when it comes to maintaining strength at elevated temps.
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Offline flateric

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #125 on: December 27, 2007, 01:52:37 pm »
Haven't you read AWST 1991 article on BMI usage in ATF program? It reads like a horror novel...))) There were a heck of other problems with BMI instead.
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stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline Sundog

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #126 on: December 29, 2007, 09:05:14 pm »
Quote
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.!

Yes, you did. There are areas of the flight envelope where a conventional tail works much more efficiently than a canard does. That's why none of the latest U.S. fighters have canards.

Offline sferrin

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #127 on: December 29, 2007, 09:30:23 pm »
Haven't you read AWST 1991 article on BMI usage in ATF program? It reads like a horror novel...))) There were a heck of other problems with BMI instead.

Never said it was trouble free from the beginning.  Just said it's better than aluminum at elevated temps.  And that was 16 years ago.  BMI is fairly common these days.
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Offline LowObservable

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #128 on: December 30, 2007, 09:49:12 am »
<<I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it.>>

Errrrmmmm....

I think that was kinda sorta the whole idea. An air-combat nuclear attack submarine.

Offline sferrin

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #129 on: December 30, 2007, 11:19:36 am »
<<I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it.>>

Errrrmmmm....

I think that was kinda sorta the whole idea. An air-combat nuclear attack submarine.


Someone forgot to tell that to Lockheed.
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Offline consealed

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #130 on: December 30, 2007, 10:16:24 pm »
Quote
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.!
Yes, you did. There are areas of the flight envelope where a conventional tail works much more efficiently than a canard does. That's why none of the latest U.S. fighters have canards.

The lost thing still Is WHY conventional tail will be much more efficient than canards? ???
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Offline F-14D

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #131 on: December 31, 2007, 11:22:19 am »
Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.

Granted high M numbers above what YF-22/23  achieved was something for which AF said it would not give credit, but I'm not sure that airframe materials would really have been a limiting factor up to M23.-2.5.  After all, F-4 did not use what we would consider exotics, and it did M2.6.  My point was that ATFs were limited to M2 and below by their fixed inlets, again AF saying it was not willing to pay for the complexity required to get another M0.5.   I was wondering if cones shown in F/B-23 were there for reasons that might indicate variable inlets (ala Mirage) in that model, indicating a desire for higher top speed. 

Offline F-14D

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #132 on: December 31, 2007, 12:23:30 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.


I wonder it it's simply a cost issue or whether it is a different design philosophy as well as something as simple as current "fashion" in the US engineering world.   It might well be true that at extreme AoA the conventional tail has an advantage (although with the modern use of using the wing trailing edge as large maneuvering surfaces instead of just a flap a canard wing could have a large "up force" at the rear), but with missiles like ASRAAM IRIS-T, AIM-9X out there, especially combined with Helmet Mounted Sights (which F-22 lacks, BTW), extreme AoA may not be as important as it was 20-25 years ago.   It's worthy of note that Typhoon is more maneuverable overall than any US fighter, with the possible exception of the F-22, and Rafale and Gripen (especially the former) may be able to make the same claim.  Of course, Typhoon is not a close coupled canard as the others are.  I'm attaching a view of Typhoon; look where the canard is relative to the pilot. 

Canards give away certain parts of the envelope to conventional planforms, but they also have some advantages as well.  On takeoff, on the approach or at low altitudes, for example, the conventional tail works against the wing.  To raise the nose or hold a positive AoA, a conventional tail exerts a downward force, negating some of the lift of the wing, requiring more thrust or a bigger wing or more required speed.  With a canard, both surfaces are exerting an upward force, increasing lift at lower speeds.  This can result in shorter ground runs and safer approaches and departures, which may be a big driving factor for the Europeans, who apparently aren't convinced that there will always be a 9,000 foot runway available.   One thing that's also a factor is the incredibly high thrust/weight ratio of modern fighters.  Rules that apply to virtually all other aircraft types get "bent" for fighters because of their ability to power out or through situations that would "trap" any other aircraft. 

On the other hand, it's harder to "stealth" a canard, because normally the canard is not in line with the main wing and so there are two surfaces for radar to see.   

On the NATF, the Navy may have been willing to accept less extreme AoA, given that they were expecting AIM-152 and some form of dogfighting missile to be arming it in return for slower, flatter approaches which the canard (like a vg wing) could provide. 

Offline sferrin

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #133 on: December 31, 2007, 12:28:37 pm »
My point was that ATFs were limited to M2 and below by their fixed inlets, 

The F-22 is not limited to Mach 2.  A fixed intake is not necessarily a limiter (the XF8U-3 also had a fixed intake and it EASILY exceeded Mach 2 as well).
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Offline Woody

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Re: Northrop/McDonnell Douglas YF-23 and EMD F-23
« Reply #134 on: January 01, 2008, 04:02:52 am »
??? 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)

You must have missed the bun fight on this one but this submission from Lantinian is enlightening:-

Quote
AIAA Paper 84-2401
Forward
Past investigationsl-5 have differed on the best choice between tail and canard for future tactical aircraft employing fined, low aspect ratio wings. A previous Grumman USAF study1 of an advanced strike fighter emphasizing supersonic persistence showed the superior trim drag characteristics of a canard. Northrop argued that a tail design has lower subsonic maneuver trim drag and greater stability c.g. location flexibility and is therefore the preferred configuration for an air combat fighter. A General Dynamics study3 indicated that a canard quipped F~16d design had potential high AOA stability and control problems when balanced at negative static margins; as a must the tail arrangement had a better subsonic trimmed polar and a Similar supersonic trimmed polar. An incompressible lifting system analysis found a tail to be the better choice. The message seems to be clear: the selection of a canard YE a tail is both configuration and mission dependent.

Conclusion
Equivalent canard and tail control surfaces are compared on an advanced, carrier-based fighter/attack aircraft featuring variable wing sweep and vectorable, two-dimensional nozzles. Evaluations of stability and control characteristics, trimmed drag due to lift, minimum takeoff rotation speeds, and carrier approach speeds are presented. The results show that the canard configuration has substantially less supersonic trim drag and a lower carrier approach speed, which can yield appreciable takeoff weight savings, but the tail configuration exhibits better stability and control characteristics with less development risk.

There must be some advantage of conventional tails over foreplanes in terms of drag (sub and supersonic) why else would they do it?, but I've yet to fully understand why. If you want to see the full thread the link's below.

http://www.secretprojects.co.uk/forum/index.php/topic,1624.0.html

Cheers, Woody