| I know that the gear is liable to shear off.... as it undoubtedly did when Air France "hit the ditch" (with one passenger reporting that the wing and engine "hit the ground" there is a consideration that the gear collapsed before the plane went off the end...as it possibly could if it had been hit by a downburst at or around the moment of initial touch down). However, the forces involved in severe braking are also unquestionably quite high and the goal is to bring it to a stop as safely as possible: there aren't that many airports near major urban regions with unlimited run-off room!
Look at it as a design problem: as one of my old engineering professors would have said "let us begin by defining the real problem". The problem is....for whatever other events that may have already occurred, we now need to bring a "runaway" aircraft which cannot get back into the air to a stop as safely as possible and with a minimum of damage to surrounding structures or persons. The only answer is to put something in it's path that will (as gently but firmly as possible) slow it down and bring it to a halt in an upright position. The military use catch nets....impractical for civil aviation and probably of limited use given the size and weights of these large planes. A gravel trap is one answer (possibly of limited use with heavy snow-cover and/or freezing temperatures); a "thicket" of trees is another (don't let them get too big though or you'll have a replay of that civil aviation film of them using telephone poles to slice the wings and allow the fuel tanks to burst open!) I think on balance that I'd rather rely on the gravel traps!
Ok, we can also refine the original problem definition to include "aircraft with from one to 300 passengers and weighing from 1,000 lb up to 100,000 lb and travelling at speeds of from 20 to 200 mph"! Quite a challenge, no? Accepting the limitations of the strength of the landing gear, I've seen those gravel traps "haul down" everything from F1 racers (at 1,400 lb?) to 80,000 lb semis! They do work. And I'd sure as heck rather end up in a belly slide than smokin' through an industrial park or residential area... or, (as in this case), possibly down a multi-lane highway at rush hour! |