T-39 Radar Testbed

Chuck Firth

Originally published November 1996

As I mentioned earlier, Northrop Grumman's ESSD Chief Test Pilot, Jay Elliott, offered to brief us on his current project, an upgrade to the APG-68 radar used on the F-16. (As it turned out, it was more about the T-39 used in the program, but still very interesting.) Jay is a former Naval Aviator, Patuxent River Navy TPS graduate, and has worked for a small, in-house radar/sensor test group for several years. We were grateful he could spare a few minutes to talk to us.

Jay came to Northrop Grumman as part of that company's acquisition last year of the Westinghouse defense business. This division of Westinghouse has a long history of building high performance military radars and other sensor systems and was considered a marketplace plum for which Northrop Grumman paid a premium. Other programs include the radar for the F-22, B1-B, and 707/767 AWACS to name just a few.

Since this was a spur of the moment program, so was the place. Usually our guests do their presentations in Scobee Auditorium, but because Jay was at Edwards to conduct flight tests, he was able to take us out to the flight line and brief us there. Since he was preparing for a night evaluation mission he was able to start getting his aircraft ready too. We stayed out of the way most of the time.

The APG-68 radar is mounted on the nose of a T-39, the military version of the North American Rockwell Sabreliner. The nose cone is faired into an F-16 radome and the aircraft's right seat has been modified to simulate the relevant F-16 cockpit instruments and controls. The flights Jay is doing are part of a regular program of product improvements and can be very business like. Load, list, reduce, analyze, reload is the routine. This particular radar has been flown 1540 times over the years as part of the company development and support program.

While getting ready, Jay described the other aircraft his group uses. In addition to the T-39 we were in and around, the company flies another T-39, two BAC 1-11's, a PBN Islander, Cessna 206, and Boeing 737. Jay quipped that Northrop Grumman not only bought a great electronics house but got an air force to rival a number of small countries in the bargain.

The T-39 we saw is unlike other Sabreliners or even T-39's I've seen which can be rather well appointed. The cabin is set up as a test engineer's work station and looks a little like the corner where the nerdy guy is left alone with his toys by everyone else. Just what you'd expect; wire, more wire, racks, equipment, and not much space for humans. Test engineers who actually fly don't come along as fat guys too often and I suspect the fit in an aircraft like this is why. That and the gee-dunk diet of Twinkies and Dr. Peppers.

Jay described the T-39 an ideal test platform for most of the work done by his group. Operating costs are about $2,000 per hour versus about $5,000 for an F-16. Other advantages are the ability to stay aloft much longer than an F-16 and an ability to mount recording equipment on the aircraft instead of using telemetry for air-to-ground relay. The T-39 also is very adaptable to the mission requirements and has a particularly useful ability to take along the radar designer when needed. (Designers are always right and their equipment works perfectly so the test engineers are just giving them some air/face time. Right.) Of course, when the test card calls for high g's or speeds in excess of Mach 1, then you go get the electric jet.

Jay comes out to Edwards about twice a year and we invited him to sit in on our meetings whenever he was in town. We appreciated the time he spent with us and thanked him for filling in on short notice.


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Revised -- 12 September 1997