|Quoting ALTF4 (Reply 3):|
Now, since a Cessna 172 with no load leaps off the ground pretty quickly, I don't think it's far-fetched to think a decent pilot (I'm low-time, so I don't count myself as experienced; this was the first abnormal situation I experienced) could make that sort of a mistake. An A320, however, takes a little longer to get off the ground. Any idea would the take-off not have been rejected in this case? Not saying the pilots did something wrong - just wondering what could have caused that.
A couple of factors that make it different in an airliner.
- A Cessna 172 has 1 pitot tube feeding one airspeed indicator through a single pitot/static system. If any of that fails, no more airspeed indication. A large airliner has 2 or more pitot tubes that feed independent pitot/static systems and independent instruments. The crew thus has at least two airspeed indicators, plus IRS and worst case groundspeed from GPS. Plenty of information to use if you do take off with one clogged tube.
- I haven't flown an Airliner except in a sim, but even there I noticed how "feeling" airspeed was really not possible like in a Cessna 172. I'll let the airliner pilots weigh in but my theory is that airliners are way harder to fly by feel.
- When the airspeed comes alive in a Cessna, you're not far from rotation. At the same speed in an airliner, you still have a ways to go. Braking from 55 knots in a Cessna can be a wobbly experience without much braking action. Braking from 55 knots in an airliner is a non-event.
On a related note, even independent instruments won't help if the crew ignores discrepancy. I watched a "Mayday/Air Crash Investigation" episode about an issue with instrumentation discrepancy yesterday. This was Korean Air Cargo 8590. The Captain's artificial horizon was not showing bank, so he kept putting in more roll to turn left. The comparator saw that there was a discrepancy and blared a warning at the crew. The F/O, whose instrument was working, said and did nothing. The F/E yelled "bank!" at the Captain but it was too late. After less than a minute the plane crashed into the ground with ninety degrees of bank. http://www.youtube.com/watch?v=YFH6jlKdr0w
[Edited 2013-03-31 20:21:52]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo