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Wow -- It was cool to see they had parachutes on the plane itself. Is this common on smaller planes these days? I've always wondered if/why airliners couldn't d

Wow -- It was cool to see they had parachutes on the plane itself. Is this common on smaller planes these days? I've always wondered if/why airliners couldn't do something like this.

Already__Taken 12y ago
It's a question of scale. I think these systems are banned in the UK as they're explosive devices and the risk of them going off on the ground was deemed more dangerous than their benefit. /noresearch
watersb 12y ago
Standard equipment on a Cirrus SR-22. Ballistic Recovery Systems, a company from Minnesota.
evanm 12y ago
Outside of most Cirrus aircraft, they're not standard. They work pretty well on light and ultralight (single engine) aircraft. Think of the extraordinary size and weight a chute or series of chutes would be for a short haul 737-sized aircraft. The cost of lugging those around across a fleet would be absolutely prohibitive. There's also little reason for this type of safety mechanism for such passenger jets. Commercial twin or quad engine planes are extraordinarily safe, and offer many more redundancies than a tiny single engine plane.
- mikeash 12y ago
  I believe you also suffer from square-cube effects. Take a light airplane with a parachute, and scale up all the linear dimensions by a factor of two. You now have something with four times the drag (drag is proportional to cross section) but eight times the weight (weight is proportional to volume). That means your terminal velocity increases by 40% (proportional to the square root of mass/area). In short, if you take a system designed for a SR-22 and just scale it up for a 737, the jet would descend much faster under the canopy, probably to a degree that it would no longer be safe. The parachute would have to be proportionally much larger still. And as you say, they wouldn't add much safety because there isn't much more to be had. I can only think of two large jet crashes offhand that would have potentially benefitted (the DC-10 that crashed in Sioux City, and that Japanese 747 where the tail fell off) and that's from a period of decades.
- malandrew 12y ago
  Ideally you'd only need chutes big enough for the cabin and that it would detach and parachute down. Would probably still be prohibitively expensive, but a fun thought exercise.
  - bdonlan 12y ago
    Then you have the remainder of the plane falling, uncontrolled, and potentially towards populated areas. Without a parachute at least the pilot will (hopefully) be trying to aim for an empty patch, and with a parachute at least the rest of the plane is falling rather slowly.
    - desdiv 12y ago
      The pilot can aim for an empty patch, then activate the parachute so that the cabin lands softly and the rest of the plane falls on an empty field. Having the chute system installed doesn't remove any options from the pilot.
      - bdonlan 12y ago
        First, removing the cabin will cause a large shift in the plane's center of gravity; without adjustment of the flight controls, it is likely to stall, dive, tilt to the side, enter a spin, or some combination of the above, and is unlikely to hit anywhere near where it was aimed. More importantly, though, the parachute is also meant to provide an escape mechanism for unrecoverable spins and stalls, not just engine failures or fuel exhaustion. In a spin or stall 'aiming for an empty patch' is, essentially, not possible, as the control surfaces of the plane are not usable due to reduced airflow. Additionally, in IMC (Instrument Meterological Conditions), it's not possible to see a safe landing spot. This is an ideal use case for a parachute, but if the plane breaks away as you say, the remainder of the plane will land in an unpredictable location. There's also the increased complexity involved with ensuring all flight control and avionics connectors between the cabin and body of the plane break away reliably and quickly when the parachute is deployed, and never break away otherwise. In short, adding a breakaway cabin might make the pilot safer (but might not, given the additional complexity for breakaway avionics and flight controls), but it puts more risk on the public at large when deployed, so it's understandable why such a system was never developed (with the possible notable exception of military ejection seats).
- acveilleux 12y ago
  More importantly, the force of the parachute(s) braking the plane would put a lot of stress on the plane structure and it's likely to break apart since it's not designed with sagging or hogging in mind (to borrow from naval architecture where those forces are explicitly modelled due to wave action.)
base698 12y ago
They actually don't help much, and arguably make things worse, because pilots that have them do things they would otherwise shy away from, like fly over mountains in marginal weather. Cirrus has only had one or maybe a couple more legitimate saves. Most airplane accidents happen on takeoff/landing or inadvertent terrain collision in bad weather. Neither of which a parachute would help. Source: Pilot, skydiver aviation nerd. Philip Greenspun is a pretty accomplished pilot and has some good writings on it: http://philip.greenspun.com/flying/cirrus-sr20 http://philip.greenspun.com/flying/cirrus-sr20 If his coining the 10th rule of programming wasn't enough for me to want to meet him add in the aviation stuff and he's definitely on my top list of people I'd want to meet.
- Involute 12y ago
  You really don't know what you're talking about. There is no evidence that the parachute entices pilots to take greater risks (if I'm wrong, by all means cite some), any more than car seat belts entice drivers to take more risks. Furthermore, "As of 25 January 2015 there have been 51 saves with 104 survivors in aircraft equipped with the Cirrus Airframe Parachute System (CAPS)." (https://www.cirruspilots.org/copa/safety_programs/w/safety_pages/723.cirrus-caps-history.aspx https://www.cirruspilots.org/copa/safety_programs/w/safety_p...) Source: Pilot, skydiver, Cirrus owner.
  - evgen 12y ago
    While I am certain there will be no evidence that parachutes have any impact on pilot behavior based on the small sample size, I am also certain that there is nothing magic about pilots and that they suffer from the same effects of psychological risk compensation as everyone else does. If parachutes make taking risks less fatal then more risks will be taken. It is as simple as that.

Wow -- It was cool to see they had parachutes on the plane itself. Is this common on smaller planes these days? I've always wondered if/why airliners couldn't do something like this.

Already__Taken 12y ago

It's a question of scale. I think these systems are banned in the UK as they're explosive devices and the risk of them going off on the ground was deemed more dangerous than their benefit. /noresearch

watersb 12y ago

Standard equipment on a Cirrus SR-22. Ballistic Recovery Systems, a company from Minnesota.

evanm 12y ago

Outside of most Cirrus aircraft, they're not standard. They work pretty well on light and ultralight (single engine) aircraft. Think of the extraordinary size and weight a chute or series of chutes would be for a short haul 737-sized aircraft. The cost of lugging those around across a fleet would be absolutely prohibitive. There's also little reason for this type of safety mechanism for such passenger jets. Commercial twin or quad engine planes are extraordinarily safe, and offer many more redundancies than a tiny single engine plane.

mikeash 12y ago
I believe you also suffer from square-cube effects. Take a light airplane with a parachute, and scale up all the linear dimensions by a factor of two. You now have something with four times the drag (drag is proportional to cross section) but eight times the weight (weight is proportional to volume). That means your terminal velocity increases by 40% (proportional to the square root of mass/area). In short, if you take a system designed for a SR-22 and just scale it up for a 737, the jet would descend much faster under the canopy, probably to a degree that it would no longer be safe. The parachute would have to be proportionally much larger still. And as you say, they wouldn't add much safety because there isn't much more to be had. I can only think of two large jet crashes offhand that would have potentially benefitted (the DC-10 that crashed in Sioux City, and that Japanese 747 where the tail fell off) and that's from a period of decades.
malandrew 12y ago
Ideally you'd only need chutes big enough for the cabin and that it would detach and parachute down. Would probably still be prohibitively expensive, but a fun thought exercise.
- bdonlan 12y ago
  Then you have the remainder of the plane falling, uncontrolled, and potentially towards populated areas. Without a parachute at least the pilot will (hopefully) be trying to aim for an empty patch, and with a parachute at least the rest of the plane is falling rather slowly.
  - desdiv 12y ago
    The pilot can aim for an empty patch, then activate the parachute so that the cabin lands softly and the rest of the plane falls on an empty field. Having the chute system installed doesn't remove any options from the pilot.
    - bdonlan 12y ago
      First, removing the cabin will cause a large shift in the plane's center of gravity; without adjustment of the flight controls, it is likely to stall, dive, tilt to the side, enter a spin, or some combination of the above, and is unlikely to hit anywhere near where it was aimed. More importantly, though, the parachute is also meant to provide an escape mechanism for unrecoverable spins and stalls, not just engine failures or fuel exhaustion. In a spin or stall 'aiming for an empty patch' is, essentially, not possible, as the control surfaces of the plane are not usable due to reduced airflow. Additionally, in IMC (Instrument Meterological Conditions), it's not possible to see a safe landing spot. This is an ideal use case for a parachute, but if the plane breaks away as you say, the remainder of the plane will land in an unpredictable location. There's also the increased complexity involved with ensuring all flight control and avionics connectors between the cabin and body of the plane break away reliably and quickly when the parachute is deployed, and never break away otherwise. In short, adding a breakaway cabin might make the pilot safer (but might not, given the additional complexity for breakaway avionics and flight controls), but it puts more risk on the public at large when deployed, so it's understandable why such a system was never developed (with the possible notable exception of military ejection seats).
acveilleux 12y ago
More importantly, the force of the parachute(s) braking the plane would put a lot of stress on the plane structure and it's likely to break apart since it's not designed with sagging or hogging in mind (to borrow from naval architecture where those forces are explicitly modelled due to wave action.)

base698 12y ago

They actually don't help much, and arguably make things worse, because pilots that have them do things they would otherwise shy away from, like fly over mountains in marginal weather. Cirrus has only had one or maybe a couple more legitimate saves. Most airplane accidents happen on takeoff/landing or inadvertent terrain collision in bad weather. Neither of which a parachute would help. Source: Pilot, skydiver aviation nerd. Philip Greenspun is a pretty accomplished pilot and has some good writings on it: http://philip.greenspun.com/flying/cirrus-sr20 http://philip.greenspun.com/flying/cirrus-sr20 If his coining the 10th rule of programming wasn't enough for me to want to meet him add in the aviation stuff and he's definitely on my top list of people I'd want to meet.

Involute 12y ago
You really don't know what you're talking about. There is no evidence that the parachute entices pilots to take greater risks (if I'm wrong, by all means cite some), any more than car seat belts entice drivers to take more risks. Furthermore, "As of 25 January 2015 there have been 51 saves with 104 survivors in aircraft equipped with the Cirrus Airframe Parachute System (CAPS)." (https://www.cirruspilots.org/copa/safety_programs/w/safety_pages/723.cirrus-caps-history.aspx https://www.cirruspilots.org/copa/safety_programs/w/safety_p...) Source: Pilot, skydiver, Cirrus owner.
- evgen 12y ago
  While I am certain there will be no evidence that parachutes have any impact on pilot behavior based on the small sample size, I am also certain that there is nothing magic about pilots and that they suffer from the same effects of psychological risk compensation as everyone else does. If parachutes make taking risks less fatal then more risks will be taken. It is as simple as that.