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Old 23rd Feb 2014, 20:22
  #545 (permalink)  
Chris Scott
Join Date: Jan 2008
Location: Blighty (Nth. Downs)
Age: 73
Posts: 2,076
Hello OG,

Yes: more or less. At a pitch attitude of +13.5 deg on T/O (main L/G oleos compressed), most of the length of the tapering part of the rear fuselage scrapes along the runway, and the RA antennae are just forward of it. If my tentative theory is correct, the RA readings in the cockpit at the same time would be a small negative value - perhaps -5 ft. I seem to recall receiving small negative RA readings momentarily on normal take-offs and landings.

So it's possible that the latter RA readings from the DFDR are a few feet lower than the lowest part of the a/c.

BTW, the pilot's eye level at the above pitch attitude (+13.5 deg) is about 27 ft above the lowest point of the a/c.

FWIW, the cockpit cut-off (visual) angle is 20 deg, i.e., the nose prevents the pilots seeing objects straight ahead which are lower than 20 deg relative to the longitudinal axis of the a/c.

So at t -11 - a couple of seconds after level-off, and at a pitch attitude of +12 - any object straight ahead which was more than 8 deg "below the horizon" would not have been visible. The recorded RA was +38 ft. Using the logic of my argument above, the pilot's eye height would have been about 25 ft above the main L/G, which itself would have been about 42 ft high. That makes the pilot's eye height about 65 - 70 ft above the ground.
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