Random links #19

Written on 12 February 2020, 04:22pm

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3 reasons to go vegetarian/vegan/flexitarian

Why do the helicopters crash more often?

  • they are used in risky situations: search and rescue operations, military, medical evacuation, etc
  • more vulnerable than planes to bad weather
  • they fly at lower altitudes, so higher risk to hit obstacles and less time to recover in case things go wrong
  • they take off and land more often than the planes (shorter routes)
  • more moving parts, so more possibilities to fail
  • can’t glide
  • a bit more difficult to control than planes


Why the commercial aircraft do not have a parachute?

Well, some of the small planes do. But the commercial aircraft don’t and are unlikely to have in the future because of how physics works:

  • if there would be a single parachute, the shock when it will be engaged will simply destroy the aircraft structure
  • multiple parachutes make things impractical: they would have to be deployed in the same time, would increase the total weight and significantly decrease the payload
  • a parachute system would require a very complex maintenance process (periodic tests, replacements, etc).
  • it would also require a complex safety system to prevent accidental deployment
  • a parachute system for a large airplane (like the Airbus A380 – 850 people or Boeing 747 – 500 people) will have to ditch everything except for the pressurized passenger cabin. Again, not practical, and how do you control where the rest of plane ends when the pilot engages this system?


OK, then why don’t the airlines give parachutes to the passengers?

Simply put, they are unlikely to save lives.

  • first problem: at which stage of the flight do you tell the passengers to use the parachutes? Life vests are simple, everybody knows when to use them. But parachutes?
  • the physics laws prevent the hatch to be opened at high altitudes. So an explosives system would be needed if you want to jump at 35000 feet (10700m)
  • if you still want to jump at that altitude, you would likely enter a thermal shock (negative 60 degrees Celsius) and lose conscience in a few seconds due to the lack of oxygen. Unlikely to land alive.
  • so you will have to blast the door and jump somewhere lower, maybe 15000 feet (4500m). Except – you’re not alone. A few hundreds passengers will try to do the same thing before the plane hits the ground.
  • assuming that the passengers can jump in an orderly manner, and allocating 10 seconds per jump, you would still need around 40 minutes for a 250 passenger plane to be evacuated in mid-air. Only 20 minutes if you open 2 doors.
  • if you manage to jump, you will hope to avoid being sucked into the engines (if you use the front doors) or sliced by the horizontal stabilizers (if you use the back doors). More importantly, you will pray to avoid fatal injuries when the parachute deploys: your plane will probably fly way past the safety jump speed limit
  • BTW, did you ever strap your parachute and actually jump from a plane? And did you ever land by yourself?
  • You see, the chances of coming down alive using a parachute are becoming increasingly small. Not to mention that you might land in the middle of a freezing ocean, with the parachute coming down on you.
  • Also, most of the aircraft accidents happen during takeoff and landing, when the parachutes simply won’t work


Later edit: In the most recent 10 accidents involving commercial airlines there were 444 fatalities (10 of them on the ground). None of them would have been saved by a parachute: 3 accidents happened on take-off, 6 on landing and 1 shot down a few minutes after take-off:

Another case that comes to mind is the famous MH370 (from 2014) – for which the most likely cause is pilot suicide. Again, parachutes would not have helped.

So if you remove the accidents during take-off and landing, the pilot suicides and the terrorist/military actions – there are really not too many cases where a parachute would help when a plane crashes.

Here is one case when none of the factors above was present: the Air France flight 447. But things happened quite fast: in 4 minutes the crew went from normal status to complete panic. There was less than minute between the moment the captain said ‘We’re going to crash’ until the actual crash into the ocean. Hardly enough time to evacuate 228 passengers from a plane nose diving at almost 300 km per hour.

In fact, looking at the history of the most important plane crashes, there is only one case where passenger parachutes would have probably saved some lives: the Japan Airlines Flight 123 – the deadliest single-aircraft accident in aviation history (505 fatalities). After a rapid decompression 12 minutes into the flight, the pilots had 32 minutes to try to recover from the situation. For most of this time (at least 18 minutes), the plane was flying above 20.000 feet (6000m) – not ideal for jumping. The high number of passengers and the mountain area would also have been an issue, but if the crew initiated the mid-air evacuation, then the passengers would have had a good 15 minutes to jump. Most probably, more than 4 would have survived.

Final words: life vests vs parachutes. Yes, the life vests actually saved a few lives. Their usage instructions is relatively simple. Yet, when needed, people still did not use them correctly: life vests actually killed people because they were inflated inside the airplane. Now imagine the complications of going from a life vest to a parachute for the average Joe.

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