Grumman Pre-ATF & ATF Studies

Some useful info gleaned from ADA081055 (AFFDL TR-79-3104) "Investigation of MSLPC and Crew Escape System Integration." Sept 1979.The baseline aircraft design studied was a derivative of Grumman/AFFDL Config Development of Advanced Fighters (CDAF) program. According to Grumman docs the CDAF was running parallel from mid 1977 with the earlier ATS and STAC programs. The drawing of the a/c on page 155 of the above doc (page 174 of the PDF) gives a designation of ASL-495F-007A for the baseline fighter design and ASL-495F-007LPC for the modified Low-Profile Cockpit configuration. This was based on the CDAF design of the ASL-495F-007. The larger, baseline Mach 2.0 Penetrator (page 156 of the doc/page 175 of the PDF) variant appears to be designated the ASL-495F-006. In APPENDIX E - FIGHTER APPLICATION DATA (page 201 of doc/page 220 of PDF) some additional data is burried in the CISE computer program input listing. Design mission profile is included in the listings.

Here's some additional a/c details from the listing that are not in the drawing:

Grumman ASL-495F-007A - Mach 1.6 Fighter/Attack aircraft (as of Feb 1979)
[indicates Grumman ASL-495F-007 - CDAF Mach 1.6 Fighter/Attack aircraft - data as of Nov 1978, all else is same as -007A]

Length: 56 ft (assuming fuselage, not overall)
Wing Area: 368 [365]
Wing Aspect ratio: 3.0
Wing T/C (root): 0.045
Wing leading edge sweep: 57 deg
Wing taper: 0.15
Vertical tail Area: 71 [70]
Vertical tail Aspect ratio: 1.03
Vertical tail T/C average: 0.036
Vertical tail 1/4 chord sweep: 52.8 deg
Vertical tail taper: 0.168
Canard Area: 57 [56]
Canard Aspect ratio: 2.68
Canard T/C average: 0.036
Canard 1/4 chord sweep: 46.7 deg
Canard taper: 0.160

Max Mach speed: 1.90
SL max Mach speed: 1.20
Ultimate Load Factor: 9.8g
Takeoff distance (ground run): 925 ft
Takeoff wing loading: 65.6 lb/ft2 [65.7 lb/ft2]
Takeoff T/W: 1.027 [1.028]
Landing stall speed: 117 knot [118 knot]
Landing distance (ground run): 1065 ft
Total thrust SLS (max A/B): 24791 lb [24625 lb]

Empty weight: 15589 lb [15492 lb]
Stores: 1000 lb
Takeoff weight: 24128 lb [23944 lb]
Combat weight: 22805 lb [22630 lb]

Propulsion: 2 x CDAF study-YJ18 (?) turbofan with A/B

I didnt include the Mach 2.0 Penetrator data - I didnt want to burden forum thread members with info they might already have.

Cheers.
 
NASA Contractor Report 3763 A Wing Concept for Supersonic Maneuvering W H Mason
 

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This "reduced RCS" design was targeting an "order of magnitude" reduction in RCS. Seems to be the low altitude counterpoint to the GASP design.

The fourth category examines weapon systems designed with RCS signatures significantly lower than traditionally-treated aircraft of conventional architecture. While the previous two categories stressed the capability to deliver a wide variety of current/near-term munitions, the low RCS concepts have relaxed weapons flexibility to achieve maximum observables reduction. Individual designs were developed for low and high penetration alternatives in response to differences in vehicle shaping and inlet/airframe integration.

[...]

At high altitude, supersonic capability (both cruise and maneuver) is still required by both "dedicated" and "treated" concepts. Although DECM power requirements are less with an order-of-magnitude reduction in RCS, a DECM suite is still necessary for survivability against surface-to-air threats. Therefore, the benefits associated with RCS control reach a point of diminishing returns in the high altitude case: the RCS-treated concept, with architectural freedom to more efficiently address other mission/survivability considerations, is a slightly more effective solution.

At low altitude, the effectiveness levels for treated and dedicated RCS concepts are again comparable, but with the above effectiveness trend reversed.This occurs because the dedicated RCS concept can achieve competitive survivability levels without a supersonic dash, and it therefore is designed purely as a subsonic (low cost) vehicle. To complement this vehicle's low RCS architecture, the avionic systems also have been fashioned to minimize their RCS contribution (described in the next section).
Furthermore, to achieve the desired RCS level, weapon flexibility was de-emphasized in favor of an architecture geared to WASP only, with internal carriage to minimize the signature impact of the weapons. Thus, the baseline RCS-treated concept is larger not only to provide supersonic dash capability but also to address carriage of the current/near-term weapon inventory. In the net, for low altitude penetrators, a tradeoff exists between effectively killing targets with a low RCS WASP-dedicated concept and the weapon flexibility inherent in a more traditional low altitude concept.

[...]

An RCS-dedicated concept is illustrated in Figure 18. It is a high wing design, with a flush engine air inlet limiting the configuration to subsonic speeds (consistent with the observations in the previous section). The vehicle is also designed specifically for carriage of WASP weapons in a "flat pack" installation atop the fuselage, a rather "natural" integration, given the fuselage shaping for RCS control. This weapons integration approach helps make the design a small and cost-effective (but operationally limited) weapon system concept.

The avionic systems integration complements the low RCS theme for this design. The SAR, placed behind a fenestrated radome, includes low probability of intercept (LPI) features such as a low peak power transmitter with the radiation spread temporally, spectrally, and spatially. The antennas for the DECM and communication/navigation/ identification systems are generally flush mounted and placed in treated cavities or, where appropriate, use designs such as spirals which inherently offer low RCS.
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Future Strike Fighter Options... Concepts and Technologies
Paul C. Bavitz
Advanced Air Force Programs
Grumman Aerospace Corp.
1981

Artwork from Bill Sweetman Aircraft 2000 - The Future of Aerospace Technology
 

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Interesting how people in the public seemed to be convinced rounded shapes were the way to achieve stealth and then when we see the real things they're all sharp edges, pretty much the opposite.
 
Engineers were trying to avoid large RCS spikes in favour of spreading the energy in all directions. This works to a degree, but only for an order of magnitude reduction - there's always some returns from all angles. That's why a 0.1 - 0.5 sq m RCS crops up a lot in early reduced RCS designs, its about as good as you can get without planform alignment.

The key breakthrough in stealth was the idea that concentrating the energy in a few very specific directions actually gave 2 or 3 orders of magnitude reduction from other angles, and if instead of 50 or 100 spikes, there are only 4, or 8, its very unlikely one is pointing back at the source antenna.
 
I sent my copy of the Bavitz paper to a magazine publisher in the early 80s and never got it back. Oh well, says I, I'll toddle down to the UC Berkeley engineering library and copy it. Opened the relevant volume of proceedings. Paper had been neatly excised.

Fun times.
 
Paul,

I picked up this paper tonight. Now I finally know the source of the High/Dive concept and the other drawings from this paper found further up thread. Another great reference for my research.

Ken
 
...
 

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Studying the LOCI (LCLL) detail drawing from DEW answered some questions I had always wondered about that design.

1) Note the paintings show it with some kind of 2D nozzle, which maybe there was a version that had that, but the drawing has a standard axisymmetric C-D nozzle with clam shell thrust reversers, similar to what you would see on a Tornado.

2) In the painting of it from front view you can see a "plus sign" inlet vane. The drawing shows the inlet is bifurcated into four quadrants and twisted down the duct ninety degrees. Even though they don't spell it out, that's a fan blocker.
 
Sundog said:
1) Note the paintings show it with some kind of 2D nozzle, which maybe there was a version that had that, but the drawing has a standard axisymmetric C-D nozzle with clam shell thrust reversers, similar to what you would see on a Tornado.
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I think the painting profile view is fairly representative of the drawing, the plan view maybe just comes across that way (note the drawing plan-view shows hatching/shading on one 'nozzle' and not the other)
Sundog said:
2) In the painting of it from front view you can see a "plus sign" inlet vane. The drawing shows the inlet is bifurcated into four quadrants and twisted down the duct ninety degrees. Even though they don't spell it out, that's a fan blocker.
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Which front view painting do you refer to?
 
I'll have to dig it up, the front view painting, it's in one of my papers, but it's only black and white. You can also see it in the attached three view drawing. I can assure you the nozzles shown in your drawing are axisymmetric, because if they were 2D they wouldn't have the curved clam shell TR and side pod actuator. Also, they're shown circular in the cross section views.

During this time period, Grumman was studying all manor of 2D nozzles and axisymmetric nozzles on their designs, which can be seen on many wind tunnel reports on their CDAF design.
 

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Sundog said:
2) In the painting of it from front view you can see a "plus sign" inlet vane. The drawing shows the inlet is bifurcated into four quadrants and twisted down the duct ninety degrees. Even though they don't spell it out, that's a fan blocker.
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Nice, well spotted. Looking closer at the plan view it’s labelled as a twisted bifurcated inlet above the starboard inlet and I think you can see the twist in the port inlet?
 
By chance, is anyone here who knows how I can get these documents which addresses to CDAF:
P.C. Bavitz, et.al., "Configuration Development of Advanced Fighters," AFWAL- TR-80-3142, November 1980,
  • Vol. 1 - Executive Summary
  • Vol. 2 - Concept Derivation
  • Vol. 3 - Concept Definition and Validation
  • Vol. 4 - Wind Tunnel Test Program
 
Ohhhhhh, is it available for trade????
 
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archipeppe said:
It is my opinion or did it is suspiciously looking alike the various F-19/Aurora designs of late 80's and mid 90's?
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It would make sense. It's an actual design, so it has plausibility, but not a real stealth design, so it would work as an intelligence decoy. Best case, it might cause the Soviets to waste time and resources working on something similar. Worst case, more confusion as to what the US is actually doing with stealth.
 
The GASP design was published in Aviation Week, and it looked like the popular idea of a stealth design, so it informed various people's Stealth speculation.
 

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