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Author Topic: General Dynamics ATF  (Read 19997 times)

Offline flateric

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Re: General Dynamics ATF
« Reply #15 on: October 15, 2012, 12:35:27 pm »
The General Dynamics Design

The General Dynamics design for the dem/val phase evolved from a variety of inputs. During the previous program phase, the company had focused on three separate families of aircraft: conventional, all-wing, and semi-tailless (denoted in the configuration studies by C, W, and T, respectively). The conventional family derived from the Model 21 designs of the previous studies. The all-wing family strove to carry Sneaky Pete's minimum observables into the supersonic regime. The semi-tailless family, which had a single vertical tail, fell in between these two extremes. After a series of internal design competitions and trades, the company went with the semi-tailless approach.

The wing planform and airfoil design were chosen to minimize weight while providing the maximum turn capability and supersonic cruise. The single vertical tail, however, presented problems in achieving a totally stealthy design. General Dynamics ran many wind tunnel tests to find a location and shape for twin canted vertical tails on the T configuration. The vortex flow off the forebody and delta wing produced unstable pitching moments when it interacted with twin tails. Without horizontal tails, the aircraft did not have enough pitch authority to counteract these moments. A single vertical tail and no horizontal tails was finally identified as the best overall approach to the design despite the degradation of radar cross section in the side sector. The proposal configuration was designated T-330.

General Dynamics took a unique approach to the sensor requirements, using two radar arrays and one infrared search and track sensor. (Boeing and Lockheed had each used three arrays and two IRST sensors.) One IRST sensor was placed in the nose of the aircraft and the two radar arrays were located aft of the cockpit. The radar beam from each array could be steered sixty degrees from the face of the array, allowing each radar to cover the area from straight ahead to 120 degrees aft. The arrays were located just above the engine inlets.

General Dynamics configuration achieved a high state of detailed design. The company had built a full-scale mockup and was finalizing a half-size pole model for testing the design's radar cross section. Preliminary structural designs were developed, along with locations for manufacturing breaks to allow the aircraft to be divided among potential partners. General Dynamics had done well in the concept exploration phase of the program, placing very high in the field of seven. Among General Dynamics strengths were its extensive experience in fighter design and manufacturing gained in the F-16 program. The company also had experience with rapid prototyping: the YF-16 was an unsurpassed program in this respect.

F-22 Design Evolution
Reprinted article from Code One Magazine, April 1998, Vol.13 No.2
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline Hamzalippischh

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Re: General Dynamics ATF
« Reply #16 on: October 16, 2012, 04:17:48 am »
Okay, thanks for your tip Nil and keep it up  ;)
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Offline Nils_D

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Re: General Dynamics ATF
« Reply #17 on: October 28, 2012, 03:27:22 pm »
Bays and stuff.

Offline Nils_D

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Re: General Dynamics ATF
« Reply #18 on: November 18, 2012, 02:37:07 pm »
More pics. I'm considering deleting the sidebays since they are kind of too tight a fit. However that leaves only 4 AMRAAM as armament. It'd be nice to see some drawings or photos of the actual mockup that GD built.

Offline Nils_D

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Re: General Dynamics ATF
« Reply #19 on: November 19, 2012, 02:01:13 pm »
Well, comments would sure be welcome.

Offline flateric

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Re: General Dynamics ATF
« Reply #20 on: November 19, 2012, 02:05:31 pm »
very nice!


Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter, by David C. Aronstein, Michael J. Hirschberg, & Albert C. Piccirillo, AIAA 1998 - confirms that GD ATF had weapon bays positioned just like on YF-22
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline Nils_D

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Re: General Dynamics ATF
« Reply #21 on: November 19, 2012, 02:20:39 pm »
Alright! The AIM-9s are a really tight fit in the sidebays atm though so perhaps the landing gear needs to be moved back? The position of it looks about right, though, CG-wise and using YF-22 as a guide.

Offline Sundog

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Re: General Dynamics ATF
« Reply #22 on: November 19, 2012, 04:37:55 pm »
Partly it might be the way you have it packaged. You have the sidewinders aligned with the aircraft center line, which will increase the size of the bay. If you angle them nose out, so you have the same clearance to the outer mold line with the front sidewinder fins as you do the rear, it will make more room for where the inlets sweep in toward the center of the fuselage. Also, make sure that you have them mounted in an X configuration where the two tips of a side of the X (Representing the fin sidewinder fin configuration) are aligned with the slope of the outer fuselage wall where the bay doors are. This should minimize the size of you bay and maximize internal volume. Edit: Looking at the pics you may have done this already but it's difficult to tell from the images posted.

Also, angling them nose out would make the launcher more simple, since, based on how the F-22 launches its Sidewinders, they're angled out at launch. Which I assume is to make sure there is a minimum chance of the aircrafts near field aero causing them to fly into the aircraft.

Also, it looks like you have side bays too far forward. Look at a good bottom view of the F-22 and you'll see the side bays are further back along the aircraft. I would propose you convert the main landing gear into the style the production F-22 uses. This would allow you to move the side bays further back, since the MLG bay won't extend so far forward anymore.

It's looking really good so far.
« Last Edit: November 19, 2012, 04:42:21 pm by Sundog »

Offline chuck4

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Re: General Dynamics ATF
« Reply #23 on: November 19, 2012, 04:41:07 pm »
Any chance the central bay is narrow and deep, and holds a stack of more missiles than 4?   

Offline Sundog

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Re: General Dynamics ATF
« Reply #24 on: November 19, 2012, 04:44:11 pm »
Any chance the central bay is narrow and deep, and holds a stack of more missiles than 4?

No. That would add too much frontal area and take up too much internal volume. The original F-22 held four as well. The only reason they can have six now is due to staggered mounting in the main weapons bay and the redesign of the missiles.

Offline Nils_D

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Re: General Dynamics ATF
« Reply #25 on: November 20, 2012, 02:21:20 pm »

Also, it looks like you have side bays too far forward. Look at a good bottom view of the F-22 and you'll see the side bays are further back along the aircraft. I would propose you convert the main landing gear into the style the production F-22 uses. This would allow you to move the side bays further back, since the MLG bay won't extend so far forward anymore.

I've been thinking about this. The YF-22 and F-22 have more space due to being somewhat longer than the GD design. I'm not sure about changing the gear as teh wing is too thin to house the wheel and I think the YF-22 type gear is more plausible, being much like an F-16 gear mounted on a wider body.

Online SpudmanWP

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Re: General Dynamics ATF
« Reply #26 on: November 20, 2012, 02:37:24 pm »
Something looks off with that GD ATF bay.  At the time the GD ATF was being designed only the AIM-120A/B existed and not the clipped-fin AIM-120C as shown in the picture.

Just like in the F-22, if you can hold 4 AIM-120A/B then you should be able to hold 6 AIM-120C.
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Offline Nils_D

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Re: General Dynamics ATF
« Reply #27 on: November 21, 2012, 03:48:51 am »
Those are AIM-120As, I'm afraid. Like I said the plane is smaller than the F-22 judging by the canopy which would otherwise be disproportionally big. Also the main source of reference has been the YF-22 which IIRC was only capable of carrying 4 missiles in the center bay due to 4 AIM-120A being the requirement.

Offline Nils_D

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Re: General Dynamics ATF
« Reply #28 on: November 21, 2012, 01:04:15 pm »
If the gear is flipped 180 dgs to retract backwards instead of forwards, the gear bays can be moved backwards and that would give more than ample space for the AIM-9 bays. Make sense?

Offline flateric

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Re: General Dynamics ATF
« Reply #29 on: November 21, 2012, 01:34:57 pm »
a variant, but historically, aircraft designers prefer landing gears to be retracted forth (as it's easier to them to extract and lock by own weight in airstream in case of hydraulics failure)
but in case of limited space why knows...
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works