‘Things really got exciting when we flew in clouds or at night over the terrain with TFR,’ Paul Ghiron, former USAF F-111 Aardvark pilot
In 1962, General Dynamics secured a Department of Defense contract to build a supersonic aircraft as part of the TFX program. This aircraft, later known as the F-111, was the first of its kind to be designed with features that enabled it to perform multiple roles effectively.
The F-111 was the first mass-produced aircraft to feature variable-sweep wings, which could be adjusted during flight. This innovative wing design provided excellent aerodynamic performance. With the wings fully extended, the F-111 required only 2,000 feet for takeoff and landing. When the wings were swept back, the aircraft was able to achieve supersonic speeds at both high and low altitudes. At higher altitudes, it could fly at more than twice the speed of sound. Meanwhile, at lower altitudes, the F-111 could fly fast and close to the ground by using its terrain-following radar (TFR) system.
What was it like to fly the F-111 at low level with its TFR?
‘During the daytime, flying the Vark at low level was absolutely the BEST way to see the world! We used the Terrain Following Radar (TFR) some, but mostly hand flew during daytime,’ Jim Rotramel, former USAF F-111 Weapons Systems Officer (WSO), recalls on Quora.
‘At night, it was ‘interesting’. We engaged the TFR system, and it pushed us over into a 10-degree dive until we were 5,000 feet above the ground, when the dive angle increased to 12 degrees before beginning to level off 1,000 ft above the set clearance plane (how high you wanted to fly above the ground, usually 1,000 ft). After leveling off at 1,000 ft, you could ‘step down’ to as low as 200 ft. The plane was capable of flying Mach 1.2 at 200 ft. However, for the most part, at night we flew at 1,000 ft, both as a safety margin and to not scare people and livestock on the ground.
‘Since we usually flew away from populated areas, this usually meant descending into a black hole. The pilot had a radar E-scope display that showed the terrain as it would look from the side with a projection of what the TFR would do to avoid the terrain, while the WSO had a display of the terrain ahead, as if looking down on it. We would talk back and forth to ensure the airplane wasn’t trying to kill us as we navigated to the target.’
Rotramel concludes,
‘One time, we were flying through a valley in Scotland, and the pilot peeked outside and was a bit unnerved to see the stars disappearing behind the big black shadows of the mountains on either side of us. I think pilots were less comfortable with letting ‘George’ fly the jet than the WSOs, who were used to not being the one ‘in control’.’
Paul Ghiron, former USAF F-111 pilot, echoes Rotramel;
‘Always very smooth and almost always reliable right on set clearance (Altitude setting above ground). The plane was definitely in its element down low, and mostly the crew is focused on making sure the flight controls were giving the right inputs based on the TFR and attack radar displays. This was easy to interpret since the TFR would give different aural indications in our headsets based on commanding a climb or descent. So if the radar shadows were diverging, then we were listening to make sure the aircraft was commanding a climb, and conversely, if the shadows were converging, indicating we were over the terrain, we were ok.
‘The beam width on the TFR radars was very narrow, meaning flying down a canyon the wingtip clearance could be as small as 50 feet, which definitely made for some real excitement while the airplane is flying hands off.
‘But things really got exciting when we flew in clouds or at night over the terrain with TFR. Frequently, we were flying so close to the mountains that you could suddenly see flashes of our lights off the mountains as we flew in and out of clouds at night.
‘We were concentrating 100% on making sure the system wasn’t going to kill us, it is certainly not an exaggeration.’
Ghiron concludes;
‘Flying this low is not for the faint of heart, but we did it day in and day out practicing to make sure we could fly under the enemy’s radar view.
‘It is no wonder that our potential adversaries were very worried about our capabilities.’
Photo by U.S. Air Force
