The Rockwell B-1 Lancer is a supersonic-capable variable-sweep wing large bomber operated by the US Air Force. One of its "key features" is terrain-following radar and a fast, heavily-loaded low-altitude mission profile.

Wikipedia has a beautiful high-resolution picture of the inside of its cockpit (scaled down for SO): B1-B cockpit

Most of these controls are either items I am familiar with or are fairly self explanatory. I have a few questions about the terrain following radar, however, the controls for which are visible in the picture (and the US military is usually very good at blocking things out if they should not be visible in the picture):

Terrain following and avoidance radar

This panel shows "TER FLW", which I presume means "Terrain following" and "TER AVD" ("Terrain avoidance"), both in reference to the radar. Clockwise, from left to right I infer that the switches are on/off, mode selector, priority "terrain following or map", rain rejection, terrain avoidance, "clear plane" [?] so many ft above the terrain, range (in nautical miles?), rain rejection, test button, mode selector, and "Ride", which has options of "SMH".

What do all of these mean? Is my inference correct? In particular:

  • Does Ride S / M / H, mean "Smooth / medium / hard", or how rapidly the plane should adjust its trajectory and thus closely follow the ground? [Hard implying the greatest degree of change]?

  • What do the letters A to K actually do on the mode selector dial?

  • Have I correctly identified everything above?

A bonus question would be "Why are there a pair of green feet" just to the left of this panel?


2 Answers 2


S/M/H = Soft, Medium, Hard. I had an F-111E pilot describe the TFR on H(ard) as being in a Jeep at 500mph.

The A-K modes would seem to be these:

The B-1B has a single Westinghouse APQ-164 radar with a single antenna. It was developed from the APG-66 used in the F-16. It has a fixed phased array which is mounted at an angle to reflect enemy radar emissions downward. The radar can operate in any of eleven modes:

  • Real-beam ground mapping mode
  • High-resolution ground mapping mode
  • Velocity update mode
  • Ground Map Beacon mode
  • Terrain Following mode
  • Terrain Avoidance mode
  • Precision Position Update mode
  • High-Altitude Calibration mode
  • Rendezvous Beacon mode
  • Rendezvous mode
  • Weather detection mode


  • 1
    $\begingroup$ Looks like you nailed it – and that site is a (very!) interesting story of its development. Do you know what the green feet are? Re Hard ride: "Naturally, the system was deliberately designed to err on the side of caution, but it would sometimes happen that an error signal would be sent that would cause the aircraft to suddenly zoom upwards at 2.4g for 10 seconds for no reason. On some missions, this would happen as often as once every three minutes." -- yikes! $\endgroup$
    – Landak
    Dec 2, 2022 at 13:54

The A-K is the setting for altitude above the terrain for terrain following mode. Terrain avoidance on the right side shows altitude, but they are letter coded for terrain following because probably is or was classified. But when you would set one of the letter positions, the corresponding TF altitude would show on the TF display screen in front of the pilot. I know what the lowest one is, but won't say it here.


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