NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Pilot avoids collision with Venus
From: Gary LaPook
Date: 2012 Apr 18, 18:04 -0700
From: Gary LaPook
Date: 2012 Apr 18, 18:04 -0700
It's really hard to judge distances to a light in the sky at night. For evading another plane a pull up is much better than a push over for two reasons. You can produce a much greater lifting force and this force then changes the flight path of your airplane (A=F/M) so you can make a much bigger change in your course or altitude in a short time and have a better chance of avoiding the collision than with a push over. The other reason that "pulling" G is better than "pushing" and creating negative G is that the stronger positive G pushes the passengers down in their seats where they are not likely to be injured. When you push you cause the plane to accelerate downward away from the passengers' butts which causes the ceiling to come down and smack the pax. I had a case where a DC-10 was climbing out from LAX and going through 22,000 feet at 360 knots when the autopilot glitched (there was an invisible bridge across the strain gauge in the control wheel sensor) and caused the nose to pitch up slightly. The pilot noticed the uncommanded pitch-up and forcefully pushed the nose down causing the flight attendants and their heavy food service carts to be launched up to the ceiling and then the pilot pulled back causing everything to smash down on to the floor and the seated passengers. Then the pilot did it again and the plane went through three cycles of this with diminishing amplitude. Lots of people ended up in the hospital. We represented Allied Signal Inc, the makers of the autopilot. I deposed the pilot and he testified that he had to take such forceful action to avoid the plane stalling due to the nose being so high as to cause the airspeed to drop off to stall speed. He testified that he pushed the nose down to the horizon. I asked him how he determined that the nose was on the horizon and he said visually, by looking over the nose, he said he did not refer to the flight director (the attitude indicator or artificial horizon). The proper recovery procedure was to smoothly lower the nose to the level position, but he should have used the flight director to determine when the nose was aligned with the horizon, not the visible horizon beause, from 22,000 feet, the visible horizon is actually 2.4° below horizontal. I asked him why he pushed so abruptly and he said the plane had already slowed so much that it was about to stall. The flight data recorder told a different story, the speed dropped only to 320 knots and the stall speed was only 165 knots, not even close. The pilot simply overreacted. He was a former navy fighter jock and forgot that he had a plane full of people behind him, that he didn't just have an F-14 strapped to his butt. gl --- On Wed, 4/18/12, Geoffrey Kolbe <geoffreykolbe@compuserve.com> wrote:
|