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Granted, commercial planes are much heavier than the jets that land on aircraft carriers. That still doesn't mean they couldn't be stopped in an emergency by a series of tailhook cables. The idea would be to have the cables in channels running across the far end of runways. Sensors closer to the landing
spot would quickly calculate whether a plane was going to be able to stop before it ran off the end of the runway, If it couldn't then the cables would pop up and snag new hooks built into the underside of commercial planes. The presence of these cables would also extend the point of no return (where pilots can safely abort a takeoff) because a new safety feature in the planes would also let the pilots raise the cables themselves in an emergency, increasing the amount of time they had to make their decision.
If the cables were installed on shorter runways it would also increase the number of places that large planes could make emergency landings.
[bristolz,
Aug 22 2005]
Landing an F16 at Tucson International Airport using a hook and cable
http://www.f-16.net...ws_article1375.html
Worked, but not that great. [ldischler, Aug 20 2005]
ALPA statements about various overruns.
http://www.alpa.org...uleId=1458&Tabid=73
When is anybody going to pay attention to this issue? [bpilot, Aug 20 2005]
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I just had a mental image of one of these being used on a runway that goes over a highway, and suddenly they realize that the plane was not directly centered, so it jerks the plane and it turns, heading right off the runway bridge and onto unsuspecting traffic. Was it worth it? hhhhmmmm. just a thought. ;) |
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I'm thinking the cables would stop the plane regardless of what angle the hook grabbed them from. The plane might be jerked left or right, but it would still be stopped before it left the runway. If the cables weren't strong enough to make that happen then there would be no point in having them there in the first place. (It might take a series of cables to do the trick in order to account for those that snapped under the plane's momentum.) |
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I have to bun this as I can't raise any reasonable objections. |
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well argued, you get a bun from me too. :) |
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Assuming the structure of passenger aircraft could survive this, it might be more useful for an aborted takeoff, when you always have a short runway. See the F16 link. For use, the pilot would drop the hook. The cable is always there, a couple of inches above the tarmac. No problem, because the wheels just run over them. And besides, the cable would be beyond where most would leave the runway. |
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All excellent points. However, the costs
of modifying the entire civil fleet would
be absolutely prohibitive. After all, you
don't want to just yank the tail off. How
about if you apply all these ideas to a
net-type arresting system which would
catch the runaway craft front the front?
Such nets have been successfully used
in military applications. This should be
combined with an arrestive overrun
surface (called EMAS, see link). There
are a very few runways
with this type of overrun, which is
engineered to collapse under the weight
of the plane in a predictable way. |
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By the way, the Int'l Federation of
Airline Pilots' Associations recently
issued a statement about the accident
in Toronto, pointing out that the ravine
is closer to the runway end than ICAO
standards specify. This was also noted
in 1978 after a DC9 ended up in the
same ravine, killing two. Air France (and
the passengers) were unbelievably lucky
this time. There are a lot of runways in
regular use that don't meet the real
estate requirements; this idea could
have a large impact on safety. |
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My understanding is that commercial aircraft have three braking systems - air brakes, thrust reversal, and mechanical brakes on the wheels. My suspicion is that when landing, braking force is governed in order to stop the aircraft in a timely manner without causing undue discomfort to the passengers and undue consumption of brake pads. |
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In an emergency of the runway length kind, I wonder how quickly an aircraft could be pulled up if the brakes were used to the maximum effect. OK, I'll look it up myself (sigh). |
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"Sensors would quickly calculate" |
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Different airplanes need different amounts of runway strip to stop, depending on their weight. How would the sensor figure out what's coming at it? |
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"closer to the landing spot" Inside the aircraft? |
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I think you'd have to reinforce
the belly of the aircraft to stop the tail
being ripped off without even significantly
slowing the plane down. I remember
reading about the US Navy borrowing
some
USAF planes some years back and having
bolt an awful lot of metal to the belly
before they added the tail-hook. |
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The forces involved could be reduced if the deceleration length was longer. |
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True. Maybe we need some bungee cord. |
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Wouldn't it hook the wheels first? tripping the plane? |
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(ok, read all the annos, seems you think you could run over the cables. I wonder if you might at least get flat tires. I'm not convinced it's OK. But convincing me is not necessary, if this thing works, it works.) |
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Rayford - I don't know for sure, but I'd be surprised if planes aren't already sending out some kind of beacon to air traffic control towers to let them know what's coming their way. The same beacon could be picked up by the sensors to calculate how much runway is required. |
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Another note - the cables can be built to snap under a certain load so a series of them could be use to slow down and then stop the plane. Lots of little jolts instead of one big one. |
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Nice illustration, [bris]. I laughed. |
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I can see it now, the cable ripping right through the vertical stabilizer. |
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Yeah, might work. it's still going to need to differentiate things, like empty vs. loaded down with jet fuel, obese Americans and our luggage, for example. |
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Good idea. I wonder if part of the reason ideas like this are not in use is because airlines are trying to put up all possible appearance and reassurance of complete safety. Once you start adding cables and nets to the system, some people might start thinking "Is this safe? Should I really be flying". Intelligent people may not think that way, but public behavior and mob behavior often skip right past logic. |
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Rayford - A lot of weighing stations for trucks are now set up so the trucks can be weighed while they keep moving right on over the scale. It might be possible to add something similar to the runways, although there would have to be more than one scale strip crossing the runway because we couldn't be sure exactly where the plane would touch down. (I suppose we could have just one 20-30 feet away from the cables but that wouldn't leave us much response time.) |
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A lot of people are forgeting that planes are designed to go UP. If I understood you correctly, The plane could go up and the hook could fall off, because some privite planes take off quickly. If a plane needs to come in for an emergency, the hook will grab, the planes bounce on the wheels, and the plane goes up, losing the hook. Good idea, needs more thought. |
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Why not just have a ski-jump-esque ramp
at the end of the runway? If the plane
overshoots, it finds itself rolling up a
progressively steeper slope until it comes
to a halt and gently rolls back down
toward the terminal building. |
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Plus, if the plane is really intent on
overshooting, the ski-jump would help to
get it airborne again. |
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I once saw a crop-duster pilot land in the saddle between two small hills - nice smooth downslope on approach (not very steep at all), then nice roll-out up the other side to a stop (somewhat steeper than the first side). Worked like a charm, very short landing. There was (some) flat land around, so I guess the hill landing was a matter of choice by the pilot. |
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This system would give the pilot a lot of false confidence, and he might come down to fast too often. |
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