amichiel@rodan.acs.syr.edu (Allen J Michielsen) (04/08/90)
In article <1990Apr6.024844.16083@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <278@flight.UUCP> george@flight.UUCP (George Rachor ) writes: >>Are you talking about blown tires or gear deployment failure > >No gear-up landings -- so far, when asked to come down, the gear has >always come down... On a side note, correct me if my memory has fogged considerably... Isn't the gear down system a spring loaded explosive system ? I kinda remember understanding that the gear was locked in place by explosive bolts, which are blown & the gear drops. Gravity & springs then drop the gear. If that's correct the gear could only stay up if the explosive bolts don't fire. al
henry@utzoo.uucp (Henry Spencer) (04/08/90)
In article <2836@rodan.acs.syr.edu> amichiel@rodan.acs.syr.edu (Allen J Michielsen) writes: >Isn't the gear down system a spring loaded explosive system ? >I kinda remember understanding that the gear was locked in place by >explosive bolts, which are blown & the gear drops. Gravity & springs >then drop the gear. If that's correct the gear could only stay up if >the explosive bolts don't fire. I don't remember the deployment mechanism, but it is true that the gear can't be retracted in flight. (That's one reason why the computers are not trusted to lower the gear -- that function is manual only.) -- Apollo @ 8yrs: one small step.| Henry Spencer at U of Toronto Zoology Space station @ 8yrs: .| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) (04/09/90)
On reading the posting on landing gear deployment I ask "what if the gear does not come down ?" Can the crew survive a belly landing, can the vehicle survive such a landing... - ------------------------------------------------------------------------------ Timothy B. Reynolds VAX Systems Manager My opinions are my own, not uncle Howards... ------------------------------------------------------------------------------
shafer@skipper.dfrf.nasa.gov (Mary Shafer (OFV)) (04/09/90)
In article <450@gazette.bcm.tmc.edu> skywalker@dino.qci.bioch.bcm.tmc.edu (Timothy B. Reynolds) writes:
On reading the posting on landing gear deployment I ask "what if the
gear does not come down ?" Can the crew survive a belly landing,
can the vehicle survive such a landing...
It's highly probable that the crew will survive and that the vehicle
will survive with only minor damage. Airliners land gear-up fairly
often, are repaired, and fly again quite nicely, for example, and the
Shuttle is much sturdier than an airliner. They'll have to replace a
_lot_ of tiles, though.
The possibility of a gear-up landing of the Shuttle has been
considered; air bags (for raising it and manually extending the gear
for towing) are in place here.
Incidentally, having _no_ gear deploy is safer than having _some_ gear
deploy. You're much less likely to roll it, for example.
I've always thought that a landing accident is somewhat likely, BTW,
but I think it likely that the vehicle won't be destroyed, just
damaged. The crew is very likely to survive, probably uninjured.
--
Mary Shafer shafer@skipper.dfrf.nasa.gov ames!skipper.dfrf.nasa.gov!shafer
NASA Ames Dryden Flight Research Facility, Edwards, CA
Of course I don't speak for NASApetej@phred.UUCP (Pete Jarvis) (04/10/90)
In article <2836@rodan.acs.syr.edu> amichiel@rodan.acs.syr.edu (Allen J Michielsen) writes: > > On a side note, correct me if my memory has fogged considerably... >Isn't the gear down system a spring loaded explosive system ? >I kinda remember understanding that the gear was locked in place by >explosive bolts, which are blown & the gear drops. Gravity & springs >then drop the gear. If that's correct the gear could only stay up if >the explosive bolts don't fire. The explosive charges that are available to "blow" the gear down are only activated if the gear is not down and locked within 2 seconds. The Pilot has a 2-switch sequence to get the gear down. The first switch arms the pyro-techics, the 2nd switch lowers the gear. The gear then has 2 second to go down and lock. If not, they are "blown" down automatically. Peter Jarvis........
henry@utzoo.uucp (Henry Spencer) (04/11/90)
In article <SHAFER.90Apr9095556@skipper.dfrf.nasa.gov> shafer@skipper.dfrf.nasa.gov (Mary Shafer (OFV)) writes: > ... Can the crew survive a belly landing, > can the vehicle survive such a landing... > >It's highly probable that the crew will survive and that the vehicle >will survive with only minor damage. Airliners land gear-up fairly >often, are repaired, and fly again quite nicely, for example, and the >Shuttle is much sturdier than an airliner... Sure about that, Mary? My impression was the other way around: the orbiter is relatively fragile. Certainly a ditching in water is considered completely unsurvivable, with serious structural failure likely (unless the assessments have been revised radically since the Rogers report); that's why the crew now has a bailout system. I can't find a definitive statement about a belly landing, although (astronaut) Paul Weitz told the Rogers commission: "My feeling is... strong that the Orbiter will not survive a ditching, and that includes land, water, or any unprepared surface..." >I've always thought that a landing accident is somewhat likely, BTW, >but I think it likely that the vehicle won't be destroyed, just >damaged. The crew is very likely to survive, probably uninjured. As I recall, both NRC and OTA (in studies on future shuttle operations) hinted that a hard landing was the single most likely reason to write off an orbiter, and that the crew would quite possibly survive. -- With features like this, | Henry Spencer at U of Toronto Zoology who needs bugs? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
shafer@skipper.dfrf.nasa.gov (Mary Shafer (OFV)) (04/11/90)
In article <1990Apr11.041856.21663@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <SHAFER.90Apr9095556@skipper.dfrf.nasa.gov> shafer@skipper.dfrf.nasa.gov (Mary Shafer (OFV)) writes: >>> ... Can the crew survive a belly landing, >>> can the vehicle survive such a landing... >>It's highly probable that the crew will survive and that the vehicle >>will survive with only minor damage. Airliners land gear-up fairly >>often, are repaired, and fly again quite nicely, for example, and the >>Shuttle is much sturdier than an airliner... >Sure about that, Mary? My impression was the other way around: the >orbiter is relatively fragile. Certainly a ditching in water is >considered completely unsurvivable, with serious structural failure >likely (unless the assessments have been revised radically since the >Rogers report); that's why the crew now has a bailout system. I can't >find a definitive statement about a belly landing, although (astronaut) >Paul Weitz told the Rogers commission: > "My feeling is... strong that the Orbiter will not survive > a ditching, and that includes land, water, or any unprepared > surface..." I based my remarks on conversations with the folks who were working on the gear and braking systems (the infamous nosewheel steering!) and that's what they think. However, notice the difference in scenario--Paul refers here to _ditching_, on an unprepared surface. We were talking about a gear-up landing, on a prepared surface (i.e. the runway or lakebed). I am quite willing to say that the Shuttle will not survive a ditching, no matter where the gear is. >>I've always thought that a landing accident is somewhat likely, BTW, >>but I think it likely that the vehicle won't be destroyed, just >>damaged. The crew is very likely to survive, probably uninjured. >As I recall, both NRC and OTA (in studies on future shuttle operations) >hinted that a hard landing was the single most likely reason to write >off an orbiter, and that the crew would quite possibly survive. Part of the question here rests on writing off vs. repairing and the other part rests on what a hard landing is. Airliners are repaired fairly cheaply, compared to the replacement cost, and both the cost and technique are well-known. As for the Shuttle, who knows? I think that there'd be a strong inclination to repair, not write off. Now what's a hard landing? Too high a sink rate, so that you bottom out the gear, or driving the gear through the wings, or scraping the belly off on the runway, or rolling the vehicle up into a ball of crumpled metal? To me the first three are damage, the last is destruction. So even a hard landing is a question of degree. But yes, the Shuttle is vulnerable to landing accidents. -- Mary Shafer shafer@skipper.dfrf.nasa.gov ames!skipper.dfrf.nasa.gov!shafer NASA Ames Dryden Flight Research Facility, Edwards, CA Of course I don't speak for NASA