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“Several different F-19 kits are available, I am going to comment on the Testors one, as I believe it was the first, and most successful.

However, the one from Monogram, shown below, resembles closely a supposed Northrop F-19 concept, which, who knows, may have had some actual reality as a project.

The whole F-19 saga appears to be littered with guesswork and disinformation, but I have chosen to look at the Testors concept, partly because that is a kit I remember seeing when it first appeared.

Before commenting on the design of the ‘F-19’ and the MiG-37B ferret, I should first say a few words about the F-117. I was in the States when this aircraft first appeared in public, working for the British Embassy in Washington. Through my role, I was at Nellis AFB on April 21, 1990 when the aircraft first appeared in public. One of the reasons I was there was that we had had a pilot flying the aircraft as a RAF exchange posting for a few years prior to its existence being acknowledged.

Here’s a couple of pictures from that day – the full story is in Two Up, a book by myself and my twin brother Ron (recently reprinted in hardback and also available as an e-book).

I put these F-117 pictures in this article to remind readers just how bizarre and unlikely-looking this aircraft was at first sight. Consequently, it is important to have an open mind when looking at the F-19 and the MiG-37B.

So, the F-117 looks pretty unlikely, but what did the F-19 concept designers get right and wrong?

Well, one thing that was clearly in their minds was that attention needed to be paid to the Infra-red signature as well as the radar signature. Consequently, they seem to have made a couple of good guesses regarding the exhaust system. This resembles the F-117 letterbox style exhaust, and also incorporates (I assume) additional cooling by mixing the exhaust with additional air drawn from the intake louvres on the upper surface of the model. The F-117 achieves the same effect through using cool engine bypass air.

The fins on the F-19 model are canted inwards. The configuration is similar to that used in the initial Have Blue demonstrator aircraft which preceded the F-117. This was either a very good guess, or suggests some awareness of Have Blue.

At the other end of the propulsion system, a shielded NASA flush inlet is used. These inlets normally work by using the shaped inlet sides to create vortices which entrain flow into the inlet. I’m not sure the Testors solution would have worked very well as an inlet, but the triangular shield over the inlet is clearly intended to block a direct line of sight to the engine face.

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The F-117 solution may look crude, but is actually an elegant solution to this problem. A grid is placed in front of the intake with a mesh size smaller than the wavelength of the radar systems against which the aircraft is designed. This prevents RF energy from entering the intake and being reflected back towards the illuminating radar.

The F-19 and the F-117 share one design feature in having a largely flat underside. This avoids excrescences and apertures which could reflect radar over a broad range of scattering angles. However, the F-19 designers were clearly not aware of the simple and inelegant solution adopted by Lockheed in the F-117, of using faceting, surface and edge alignment to constrain radar reflections to very narrow spikes to reduce the probability of a track on the aircraft being maintained. As a result, the F-19 under-surface is smooth and uncluttered, but not as flat as that of the F-117. The optical sensor is under the nose, rather than in front of the cockpit as on the F-117, which would perhaps be more difficult to screen.

The F-19, instead of adopting the very highly-swept planform of the F-117, uses a narrow curved-delta design, in some ways reminiscent of a stretched F-4D Skyray, with a break in sweep where the fuselage transitions into the wing, and a curved leading edge and wing tip.

Would this work as a stealth configuration? The disadvantage is that the break in planform would probably cause a local return, and the curved planform would spread returns so that they were likely to be detectable over a broader aspect. Making this sort of shape work would probably require extensive use of tailored electro-magnetic materials to control the nature and aspect of radar returns, but this would not have been available when the model emerged, in 1986, four years before Stealth was unveiled at Nellis AFB.

Would the design work aerodynamically? Well, the F-117 is no paragon of aerodynamic efficiency, and the F-19 wouldn’t be either. Given the planform, I’d expect lift dependent drag to be pretty high, and given the intake design, I’d expect a long take-off run, and great care to be required to stay on the right side of the drag curve on the approach. With questionable intake efficiency, particularly at any significant incidence, and a slender low aspect ratio design, getting into a high sink rate on the approach could be a distinct possibility. But otherwise, noting the need to keep an open mind – why not?

I am puzzled by the curious upward pointing fins on the upper surface behind the cockpit. These appear likely to de-stabilise the aircraft in yaw, which is probably not what it needs.

Overall, inefficient, yes, but arguably little more implausible than the real F-117. Testors missed some of the simple but effective stealth features of the F-117, but did identify some of the other features.”