From: email@example.com (Terrell D. Drinkard) Organization: New Large Airplane, Boeing Commercial Airplane Group Date: 22 Oct 93 01:05:03 PDT References: 1 2 Followups: 1
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In article <firstname.lastname@example.org>, Stefano Pagiola <spagiola@leland.Stanford.EDU> wrote: >I'm not sure about thrust-reversing, but I remember Piedmont lost a >737 at Charlotte some time ago when some combination of aquaplaning >and floating in ground effect meant spoilers could not be deployed >because releasing them requires the mainwheels to be firmly on the >ground and to have begun turning. Just as it makes sense (most of >the time) to prevent spoiler deployment in flight, it probably would >make sense to have similar safeguards to prevent thrust reverser >deployment in flight. Can anyone confirm whether/how its actually >done? [Quoting from the Airplane Systems Familiarization book - an in-house Boeing publication] Thrust reversers require the following to deploy: 1) 28VDC power available 2) Engine fire switch in the normal position 3) Airplane on ground (squat switches activated) 4) Thrust lever in idle position 5) Reverse thrust in the reverse idle detent position Autospoilers require the following to deploy: 1) Hydraulic pressure to the truck tilt indicators 2) Both thrust levers at idle 3) Both truck tilt sensors detect a no-tilt condition (a/p on ground) 4) Speedbrake lever in the armed position [End of quotes] I can't imagine anyone using tire spin-up as an activation criterion for autospoiler or thrust reverser operation. Too much attention is paid to the icy runway scenario (which is one reason that thrust reversers are included even on the 737 where there is some concern about their cost/benefit ratio). Safety is of primary importance to Boeing, and I'm quite sure, to Airbus as well. No one benefits from an unsafe airplane. My suggestion is to wait for more information before coming to any conclusions about the contributing causes of the accident. Pilot error seems to be the primary cause given the weather. This bears some similarity to the Mokpo accident of a couple of months ago where the pilots attempted three times to land in really bad weather. Questions for Robert Dorsett: Could the pilots high levels of experience and presumed competence have contributed to a false sense of security which led to an error in judgement? If so, how can this be avoided in the future? Did the 'cocoon' effect of the A320 cockpit contribute to the possible overconfidence? Another idle thought: The descriptions of the weather at Warsaw seem to match the profile for microburst activity. Did the pilots and controllers not recognize this, or did I miss something? -- Terry email@example.com "Anyone who thinks they can hold the company responsible for what I say has more lawyers than sense."