|Quoting copter808 (Reply 2):|
I should think that a ballistic recovery system for the entire aircraft would be far simpler and save everyone, including the pilots.
Just to put a few numbers on things... It's not impossible as a concept, and chutes in the approximate ballpark of the required size have been used with reasonable success. But the weight and expense would be quite high, and low altitude deployment is probably impossible, since chutes of the required size would need to be deployed in stages.
Back of the envelope calculate is that for a 75t airliner (about a 737-700ER), you'd need a chute of over 125m diameter (assuming a single canopy) to get the landing impacts down to the humans-are-likely-to-survive-without-incapacitating-injuries range - about 8m/s (and 8m/s - 1600f/m - will definitely be a memorable impact). A real chute of that capacity would be a fair bit larger since the above assumes a perfectly dome shaped and solid chute, which is quite unrealistic for anything of that size.
The Shuttle SRBs are a useful point of comparison. The empty SRBs weigh about 91t, the main chutes (there are three), are 41m in diameter, and weigh about 990kg each (note that these are the largest chutes ever deployed, although they are working for some larger ones for use on Mars). The SRB's recovery system is designed for a 23m/s touchdown, which buys them about a factor of eight reduction in required area compared to a 8m/s touchdown requirement). Basically using a cluster of SRB chutes, you'd need about 20 of them.
However the SRB also requires a drogue chute (16m, over 500kg) to stabilize and slow the SRB to the point where you can deploy the mains. There's also a pilot chute which deploys the drogue, and the drogue actually deploys in three stages, fully reefed at first, then unreefed in two stages (the final unreef happens 12s after the drogue deploys). Then the (reefed) mains are pulled out by the drogue, and again there's a two stage unreef process (17s to the final unreef).
The SRB's speeds are not really higher than an airliner’s during the parachute deployment, the SRBs are subsonic the whole time there are parachutes involved, so the aerodynamic forces are going to be in the same ballpark.
So for our hypothetical 737, we're talking about a system weighing on the order of 25-30t (basically the entire non-fuel useful load), that takes well over 30 seconds to deploy (which would rather limit its effectiveness at low altitudes), and is half a dozen times bigger than any similar system ever built. Without even getting into the rather more severe design requirements for something rated for human use (the SRBs are unmanned, of course, and NASA has had several incidents where SRBs were damaged because of partial failures of the recovery system - most recently the Ares-I-X test).