There are small light aircraft that are fitted with giant parachutes meant to save the aircraft from a would-be crash.
From an aerodynamic and engineering standpoint, would it be possible to have big airliners such as the 737 MAX or A330 fitted with commensurately large parachutes to save them in an Ethiopian/Lion Air or AF447 type of scenario as well?
Edit: One problem that comes to mind is that the airliners would first have to slow down a lot before deploying the chute, otherwise the force might just yank the chute away.
Even if it could be got to work there are weight and space penalties to such things - it would be better to improve systems reliability and stop such things happening in the first place.
Sure, if you just redesign the planes and reduce the space for passengers. Possibly a lot. Remember, you are not only slowing down a fall, you need to dissipate all horizontal speed as well.
So would you prefer to fly on the plane that has a tiny risk of crashing, or the one that costs several times as much, has the same low risk of crashing, and probably won’t save you when it does since most crashes happen close to take off and landing when you’re too low for a parachute to slow you down in time?
Parachutes are not “get out of death free” cards. They have their own problems, costs, drawbacks, and failure modes - so much so that the UK banned their use in small planes.
Commercial airlines move too fast and have too much mass/momentum for any current parachute technology to be feasible in the manner you propose.
I think this is the issue. Parachutes only work in a relatively narrow set of conditions. If a pilot has enough control of the plane to get it into those conditions, he probably has enough control to land it.
Here’s a related column by Cecil Adams from 2013: Why don’t commercial jets have parachutes?
Not one parachute, ejector seats like fighter pilots have available. 
Yes, but that’s an entirely different parachute - for people, not airplanes.
Why would an airliner cost “several times as much” (i.e. $700 million for a Boeing 777 instead of the usual $200-300 million) for a redesign like this? The parachute would be stowed and folded in a very compact manner.
Hence, the use of the word “related”. And given the discussion in that column of the amount of space necessary for individual parachutes for each person on board, can you imagine the amount of space necessary for a parachute large enough for the entire plane?
For a point of reference: the Space Shuttle’s solid rocket boosters were recoverable; after they were jettisoned from the main tank, and re-entered the lower atmosphere, each one deployed a system of parachutes (first a drogue chute, then three main chutes) to slow their descent, to splashdown in the Atlantic Ocean.
The SRB main chute system are apparently the biggest chutes ever made and deployed. Each of those chutes weighs 2180 pounds (and I don’t think that that weight includes the drogue chute, or the rest of the deployment system). The design load for each of those chutes is listed on Wikipedia as 195,000 pounds (remember that each SRB has three of them).
By comparison, the base 777 (the 777-200) has a maximum take-off weight of 545,000 pounds. So, just on back-of-the-envelope calculations, you’d be looking at needing a system something like the parachute system like on an SRB to effectively recover a jet the size of a 777. I’m no aeronautical engineer, but it strikes me that such a system is unlikely to be able to be “stowed and folded in a very compact manner,” as the OP envisions.
Sources:
The tickets would cost more since you’d have room for fewer passengers. If you’re already certain how much space the parachute and necessary reinforcement of the plane will take, why do you need to ask the board?
I did some horribly quick and dirty math on this, but I think it might help to illustrate the problem.
Let’s say the airliner weighs in at 60,000 kg (a conservative figure, I think)
Let’s also say the conditions are somehow optimal and the chute can just be deployed without lots of additional heavy equipment.
Plugging that weight into the parachute size calculator here (which is for rockets, but whatever), and setting a desired impact speed of 3 metres per second, the prescribed parachute size is 426 metres in diameter.
Just how compact do you think you can fold a circle of fabric that’s nearly half a kilometer across?
Yeah, that’s about the maximum take-off weight of a Boeing 737-300 (which is on the small end of the non-“regional” commercial jets in use). A Boeing 737 Max has a MTOW of over 80,000 kg. A 777 is over 300,000 kg.
It’s feasible but totally impractical. The chute would have to be huge and very heavy. To deal with the potential problems will make it an even bigger and heavier system displacing a large percentage of the payload. And there are not many large aircraft that have crashed that could have been saved with such a system.
One of the biggest problems to overcome is including a shock absorption system to keep the aircraft from breaking loose from the deployed chute and to keep it from swinging back and forth in the air. You don’t want to be approaching the ground when the plane is on the upswing.
I’ll also add that, for a parachute system to make a difference in what would otherwise be a fatal crash, it’d need to be:
Here’s a list on Wikipedia of every crash which resulted in 50 or more fatalities. If you sort it by date, and look at the details of the crashes, what you see is that, over the past decade or so, the conditions I list above are only present in about one or two crashes per year, worldwide.
Yes, we’ve had two such crashes in the last few months. I cannot even begin to imagine the terror experienced by a passenger on such a flight. But, as several of us have noted, while “put parachutes on the planes” sounds like an easy fix, it’s extremely likely that doing so would be substantially more complex, heavier, and more expensive than you realize.
Leaving the logistics of the giant parachute aside, another problem is that in the 737 Max crashes, it looks like the computer was actively pointing the plane downward so it could pick up speed to avoid a stall. I have no idea of everything involved, but it seems to me if you have a parachute trying to slow the plane down and a navigation system trying to speed it up, bad things will happen.
And just what happens if there’s a failure in the parachute system that causes it to deploy while the plane isn’t crashing? Or rather, wasn’t crashing.
Setting aside the fact that it would take a huge amount of canopy area to provide sufficient buoyancy to decelerate an airliner to an impact speed that wouldn’t kill the occupants, it would require a complete redesign of airliners to even accommodate such a system. Parachute entry and descent systems on space capsules use clusters of large ringsail parachutes which are deployed by mortar-fired drogues and have multiple reefing stages to limit the canopy deployment to control dynamic forces during inflation. These are large, heavy, complex systems with timed ordnance cutters that require particular expertise and a specialized hydraulic press to pack. That these are surprisingly reliable is a tribute to the massive amount of development testing and quality control, and these are for nominal, single use deployments.
Unlike light aircraft and space capsules, airliners are a large distributed structure which is not designed for point loads to be applied except at the landing gear. The only point on an airliner that can bear the full weight of the fuselage is the wingbox, which goes below the fuselage on every modern commercial airliner. Even if you could somehow contrive to attach some kind of yoke to the wingbox and through the fuselage, the dynamic loads of a parachute system deploying and inflating would tear the fuel-laden wings off and cause such large bending moment on the fuselage that it would break apart fore and aft. The only way for a system on an airliner to be remotely feasible would be to have multiple parachutes or rogallo-type wings deploy from the top of the fuselage along some kind of reinforced spine while the wings and their massive fuel tanks are separated, which would add considerable weight and complexity for an extremely marginal benefit even if the system worked as conceived. And at the high dynamic pressures at which airliners operate (30 kft+ around a Mach number of 0.85) they dynamic loading would be intense, requiring some kind of really complex load mediation system.
Unlike single engine light aircraft, the vast majority of failure modes on flying airliners would either be unrecoverable even with some kind of aerodynamic decelerator system, or the aircraft can be deadsticked down by a competent pilot as Chesley Sullenberger did on US Airways Flight 1549. This is a solution to a problem that barely exists in the real world.
Stranger