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On smaller aircraft, like some Cirruses for example, they have parachutes attached to the body of the aircraft that can help the plane get to the ground safely in an emergency.

I'm wondering why commercial aircraft (like, say, a Boeing 737 or Airbus A320) don't do this? I figure it might have to do with the speed a jet moves at, or maybe the altitude, but I was hoping to get a more complete answer by posting the question here...

Pondlife
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Jae Carr
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    In short, having this kind of a parachute for a 737 or an A320 is not impossible as a concept, but would be too expensive, too heavy, too impractical, too difficult to implement, and hardly ever used. – usernumber Nov 09 '14 at 04:01
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    @usernumber I wonder though... fire extinguishers are also hardly used and yet they have them. So where exactly is the place where cost, usefulness and safety all converge? And how close to that point would a system like this be? – Jae Carr Nov 09 '14 at 04:26
  • The "break apart" portion of the other question is really a small part of it. Most of the responses discuss general disadvantages of parachutes and apply to the intact case as well. I'd like to see this edited something like "what are the advantages of keeping an aircraft intact under a parachute", if that is what you want to focus on. – fooot May 06 '15 at 20:38
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    I think this is unnecessarily splitting hairs. The intent of the questions is different, and a google searcher looking at both questions, I think, would feel the same. That's mainly my argument here, the questions themselves are different regardless of the information found in the answers of the either question. – Jae Carr May 06 '15 at 21:30
  • Are there other practical means of 'slowing' down an aircraft, other than parachutes? – Firee May 23 '15 at 10:10
  • I think a company that produce aircraft would profit hugely if they could sell more secure planes :) It only takes one accident to make people wary and damage the reputation of a company – Freedo Jun 18 '15 at 04:19
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    @Freedom Er, no. Rather, companies already make astoundingly safe planes; there is virtually no edge to be gained in the airliner market with safety, because safety is already regulated well past the point where there are relevant differences between aircraft. And large airliners are pretty much a duopoly, with aircraft purchasers knowing that aircraft are all incredibly safe as a prerequisite to sale and that accidents at some level are inevitable, so there's not really that reputation thing. – cpast Jun 24 '15 at 04:17
  • @Firee Yes. Pitch up. – reirab Oct 21 '15 at 03:00
  • There's also the safety hazard of an inadvertent deployment of parachutes midflight. – Tyzoid Jul 15 '19 at 15:50
  • I read something, wish I could remember where, that stated large commercial jets design would ultimately have to defer to one of two guiding principles; make them better at not falling out the sky or make them 'crash better'. The former was given prominence as 'a better way to go'. Can't remember the justification. – Moika Turns Dec 10 '19 at 12:03
  • "there is virtually no edge to be gained in the airliner market with safety" - airplanes are not 100% safe. if someone knows their life could be saved if they payed more, that's potentially a huge selling point. also, expensive safety designs will eventually go down in cost. but as i read the answers below i see your point too. (apologies if it's against the rules to critique comments). – john Jun 07 '22 at 04:03

2 Answers2

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The reason for not using full aircraft parachutes can be stitched together by looking at the many related questions. Let me do this for you:

  1. Parachutes will only help when something essential fails at sufficient altitude for parachute deployment. As paul said here, most accidents happen at take-off and landing where a parachute cannot be successfully deployed.
  2. Parachutes big enough to slow down a whole airliner will be very heavy, reducing payload and increasing the number of flights to transport the same number of passengers. The biggest parachutes designed so far were for the solid rocket boosters of the Shuttle, and paul gave their mass a 3 x 990 kg plus 550 kg for the drogue chute. Wikipedia gives the mass of one SRB at 91,000 kg. Scale this for the zero-fuel mass of an A-320 of 62,500 kg, and the mass will be approx. 2,500 kg. That is equivalent to 25 passengers, or 16% of the A-320's capacity. Adding the parachute will translate into 16% more flights, just to compensate for parachute mass. This is most likely underestimating the true impact because I did not add the mass for structural reinforcements.
  3. The opening shock at travel speed would destroy both airplane and chutes. If we want the parachute system to work in as many cases as possible, we need to make deployment possible at up to Mach 0.85, and then the maximum g-load on aircraft and passengers must not exceed 6 g. (See here for Eiband diagrams which give time- and direction-dependent limits for the maximum deceleration a human being can survive). This is possible with staggered deployment of several chutes with increasing size, and by sewing parts of the canopy and the parachute's strings together, so they can rip apart during opening, which slows the unfolding process. But I expect that this will add to the mass of the parachute system. It will certainly add to the mass of the aircraft's structure, which is currently limited to +2.5 / -1.0 g.

By looking at point 2 above alone, it becomes clear that the addition of parachutes will most likely drive up air travel casualties. If we need 16% more flights to make the cruise part less dangerous, and still most accidents happen during take-off and landing (which are now 16% more numerous), we gain little. Crashes now involve fewer passengers, but their number goes up. Tickets will become 20% more expensive at least (more if the parachute system costs something, which is very likely), and we all know how the majority of passengers votes when faced with a choice of dearer, somewhat safer flights and 20% cheaper flights at almost the same accident risk.

Peter Kämpf
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    Did the SRBs even touch down at a vertical speed that would be reasonably survivable for passengers in an aircraft cabin? And what would the plane's attitude be during descent? Dangling from attachment points at the rear, with everybody inside dangling from their seatbelts? – hmakholm left over Monica Nov 09 '14 at 16:11
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    @HenningMakholm: Good point, but I left it out because I have no information on the sink speed of the SRBs on their parachutes. Since they were designed to land in water, I would expect that the sink speed is too high to be safe for an airliner. The attitude should be similar to flight, maybe with a 20° nose down angle. Throw in a roll angle so one wing touches the ground first and helps to brake the impact of the fuselage. – Peter Kämpf Nov 09 '14 at 16:17
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    I'd like to add a 4th point: Once parachutes are deployed, you lose most if not all ability to control where the plane goes. The plane will be subject to the prevailing wind condition. – Jason May 08 '15 at 04:46
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    @Jason: Correct, but the same is true when the aircraft comes down uncontrollably, but without a chute. Deploying the chute will greatly reduce the impact energy, regardless where it comes down, so this is not a clear disadvantage in my eyes. – Peter Kämpf May 08 '15 at 08:25
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    @PeterKämpf: Your point is valid. My bias comes from flying in Southern California where you are always pretty close to mountainous terrain. Many SR pilots have said deploying the parachute is not an option for them for fearing drifting into terrain. – Jason May 08 '15 at 16:37
  • I am sure, future aircrafts would be designed from scratch to have this kind of facility inbuilt.. – Firee May 23 '15 at 10:13
  • There is also the matter of when a parachute system should be deployed. The captain would have to be in control of the trigger, and would have to decide that deployment is the best option in a given situation. Seems unlikely to me that it would ever happen. Either the aircraft would be flyable and could be landed successfully, even without engine power, or successful deployment would be impossible for some reason - whatever makes the aircraft unflyable would likely make the parachute system either unusable or its deployment destructive to the rest of the aircraft. – Anthony X Jan 23 '16 at 18:09
  • I suspect the 16% more flights would simply be addressed by operating larger aircraft, at least on the routes served by A320s. Your point is none-the-less valid on routes already served by the likes of the A380. – Phil Apr 23 '18 at 10:27
  • So an empty A320 is lighter than an empty Space Shuttle SRB? I never knew that! – Vikki Jun 04 '18 at 02:10
  • @Jason: Still better than crashing into said terrain. – Vikki Jun 04 '18 at 02:11
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    @Sean, that's precisely the reason many pilots don't like the parachute system. Once the parachute is deployed, you may crash into unfavorable terrain without any say. (Context: this sentiment is common among pilots in Southern California where the terrain is more of an issue). At the end of the day, it's a personal choice and preference. No right or wrong. – Jason Jun 11 '18 at 23:15
  • Ironically, passengers don't have to choose between cost and safety. The safest airlines statistically speaking are the budget ones! – Cloud Jun 12 '18 at 15:36
  • One final point would be that, on a multi engine aircraft, you really don’t need the parachute - you can always land on one engine. – Romeo_4808N Jun 12 '18 at 19:57
  • Another factor is trans-oceanic flights; even if the passengers survive the landing and escape from the aircraft, they are unlikely to survive until they are rescued. – Paul Johnson Sep 02 '19 at 12:10
  • So these are all valid points, I just struggle with the 700+ people that died last year with the 737 Max planes without control and a parachute would have saved all their lives. You can design for xyz contingency as you should all the time and airline manufactures do. The problem is there is always a problem and going back to basics would have saved lives. Will there be a plan crash in 2020? Absolutely. Would have it been survivable with a space age material lighter than the ones posted in this answer, probably yes. – Kevin Parker Jan 28 '20 at 23:55
  • @KevinParker So you expect an aircraft manufacturer who leaves critical input to a flakey and non-redundant sensor to fit a humongous parachute to their planes? It would had been much cheaper and had cost much less additional mass to fit an adequate horizontal stabilizer. But that costs money … oh, by the way, those parachutes also don't exactly come for free. You cannot fix a rotten culture with technology. – Peter Kämpf Jan 29 '20 at 17:12
  • Yes, because I hear that all the time Peter. Flight 102, flight 610, flight 58 yes yes would have been fixed had there been one more sensor, one more line of software code or one more safety feature that the airline didn't order. It's getting old and people are dead year after year. Sometime this year an engine will explode in a way it shouldn't have because of some unforeseen problem like a loose screw, weak glue, welding problem, metal fatigue blah blah and everyone on the plan would have prayed to whatever got they weren't so cheap and delusional about their safety there was a parachute. – Kevin Parker Jan 29 '20 at 18:23
  • @KevinParker: Now suppose that parachute has been added. On deployment, it is torn to pieces because the manufacturer was too cheap to use decent materials. Will you now ask for a second, redundant parachute or shouldn't we really address the core of the problem? – Peter Kämpf Jan 29 '20 at 18:42
  • Peter - No one said anything about a second parachute just you. Just like they have backup hydraulics or electrical power, redundant systems help make flying safer. – Kevin Parker Feb 03 '20 at 01:49
  • All very interesting. I would have made the arguments around a) horizontal velocity, which would somehow be reduced to 0 prior to touch-down, b) balancing the aircraft so that it doesn't crash people face down into the ground and c) Parachute landings are not really soft and smooth, the tin can would still smash into the ground and today is certainly not built to do that and keep passengers safe. Planes that can reliably do a) and b) after a successful lift off are hardly in a situation where they need a parachute to land. More so if they can do c) as well. – user1129682 Jun 10 '21 at 17:44
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Any time the question is "why don't we have...", the answer is almost certainly in the trade-off between weight, maintenance cost, fuel cost, & utility. If it weighs a lot, needs maintenance, burns fuel, and will only be useful once a decade, then it just is not productive.

Putting a complex parachute system on a plane will be heavy, meaning fewer passengers, or less fuel or cargo on board. All that extra weight has to be flown around, requiring fuel. They would need regular maintenance checks, which is another cost. And a parachute would only be useful very, very infrequently (on most planes, it would never be used).

So it is just impossible to justify adding new equipment for a once-in-a-lifetime scenario, which can be better managed with good maintenance, good training, and good planning.

This same line of reasoning goes for "why don't more airplanes have rocket thrusters", "why don't planes have anti-missile systems", "why don't planes have airbags", and many other random items.

Community
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abelenky
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  • Your remark is basically inherent to the question. I'm aware there is a trade off, I want to know what form it takes. Mostly I'm curious about why it might weigh so much, or if it might pose particular structural and aerodynamic issues. What causes this solution to be impractical in particular, basically. Dismisses it as "simply a trade off" kind of misses the deeper purpose of the question. – Jae Carr May 22 '15 at 16:37
  • As others have already pointed out, such measures are counter-productive. They would kill more pax than they would save by putting a greater number of aircraft through flight phases where accidents are more likely. – Martin James Jul 09 '15 at 13:36