The Naked Scientists

The Naked Scientists Forum

Author Topic: Why couldn't they find the site of the crash?  (Read 8013 times)

lyner

  • Guest
Why couldn't they find the site of the crash?
« on: 05/06/2009 13:42:59 »
For a very few hundred UKpounds, any yachtsman can buy an EPIRB (Emergency Position Indicating Radio Beacon) which can automatically transmit a signal which tells the World where you are, in an emergency.
With the massive weight of safety equipment which aircraft carry, you'd think that they could also carry a pod, with one of these beacons in it. This pod could be jettisoned automatically just before a crash and, even if there were no survivors, would give everyone a clue where to find the wreckage and, probably more importantly, the black box recorders.
Are they ever carried and, if not, why not?


 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Why couldn't they find the site of the crash?
« Reply #1 on: 05/06/2009 14:56:33 »
This pod could be jettisoned automatically just before a crash
how much 'just before'?
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #2 on: 05/06/2009 16:17:29 »
They would probably need a braking parachute (hitting the ocean/sea at several hundred mph is like hitting a solid), and will mean a little extra non-profitable weight, but otherwise it sounds like a good idea.
 

lyner

  • Guest
Why couldn't they find the site of the crash?
« Reply #3 on: 05/06/2009 16:31:54 »
This pod could be jettisoned automatically just before a crash
how much 'just before'?
Reserve Parachutes for skydiving use an automatic opening device which goes off at about 70m when you're falling too fast.  Something like that would do the job.
It wouldn't be the end of the World if it happened to go off and you managed to get back up into the air, in any case.

The added weight would not be profitable but, then again, nor is any of the other safety kit.

As an alternative, why can't every Airliner transmit its coordinates on a regular basis when it is off radar. It would cost a fraction of a penny for each transmission and it could help Air Traffic Control, too.
« Last Edit: 05/06/2009 16:35:30 by sophiecentaur »
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #4 on: 05/06/2009 16:42:53 »
I agree, the added weight would probably only be equivalent to a single passenger i.e. negligible on a large airliner.  Good idea re broadcasting your position on a regular and frequent basis too.
 

lyner

  • Guest
Why couldn't they find the site of the crash?
« Reply #5 on: 05/06/2009 19:20:29 »
A single passenger's duty free, more like.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8667
  • Thanked: 42 times
    • View Profile
Why couldn't they find the site of the crash?
« Reply #6 on: 06/06/2009 15:54:52 »
In the event of a crash there are survivors or there are none.
If ther are then they can signal for help. If not then it doesn't matter if it takes a whle to find the crash site.
 

Offline Don_1

  • Neilep Level Member
  • ******
  • Posts: 6890
  • Thanked: 7 times
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Why couldn't they find the site of the crash?
« Reply #7 on: 06/06/2009 16:13:37 »
Would it not be a good idea to fit the 'black box recorder' with a beacon which would activate in the case of emergency. If the plane then crashes it could be located, if the plane makes a safe landing or the emergency is overcome, the signal can be switched off.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Why couldn't they find the site of the crash?
« Reply #8 on: 06/06/2009 19:49:31 »
Would it not be a good idea to fit the 'black box recorder' with a beacon which would activate in the case of emergency. If the plane then crashes it could be located, if the plane makes a safe landing or the emergency is overcome, the signal can be switched off.
This doesn't seem a bad idea.
 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Why couldn't they find the site of the crash?
« Reply #9 on: 06/06/2009 22:56:22 »
As far as I know, passenger aircraft do carry an EPIRB. It is called an Emergency Locator Beacon (ELT) on aircraft but is essentially the same and communicates GPS position to the same satellite systems as does an EPIRB. Deployment without damage in the event of an emergency is not as straightforward as with boats, and its effectiveness can depend on the nature of any crash.
 

lyner

  • Guest
Why couldn't they find the site of the crash?
« Reply #10 on: 06/06/2009 23:10:21 »
In the event of a crash there are survivors or there are none.
If ther are then they can signal for help. If not then it doesn't matter if it takes a whle to find the crash site.
Not so sure that a few passengers bobbing about in freebee lifejackets are in any position to signal anything.
 

Offline nicephotog

  • Sr. Member
  • ****
  • Posts: 387
  • Thanked: 7 times
  • H h H h H h H h H h
    • View Profile
    • Freeware Downloads
Why couldn't they find the site of the crash?
« Reply #11 on: 07/06/2009 09:47:46 »
Quote
Deployment without damage in the event of an emergency is not as straightforward as with boats, and its effectiveness can depend on the nature of any crash.

Two things the press has said:
1. We finally as they after days don't actually know what occurred.
2. Sorry (so also the Brasilian Military and Coast gaurd)

But here's a point, they said that in the space of five minutes the pilots were having a problem with the aircraft shutting down damaged electrical systems.
That lasy point does not mean that the aircraft had to actually leave the air directly down within 100km.
If the engines did not shut down and the fuel continued and the trajectory of descent was slow there is a possibility the aircraft could be up anything to 300km beyond or around(radius) the emergency transmission point when it sent messages saying it had faulty electricalsperhaps more realistically 150 250km dependant its continued speed e.g. 300 - 400kmh.
5 - 6 Km / minute
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8667
  • Thanked: 42 times
    • View Profile
Why couldn't they find the site of the crash?
« Reply #12 on: 07/06/2009 15:14:29 »
In the event of a crash there are survivors or there are none.
If ther are then they can signal for help. If not then it doesn't matter if it takes a whle to find the crash site.
Not so sure that a few passengers bobbing about in freebee lifejackets are in any position to signal anything.
I am, the life jackets are sometimes fitted with torches not to mention being fluorescent orange(like "black" boxes). At the least, they can wave which they don't do if they are not survivors.

Incidentally, if you have a "black box" that doesn't float it ends up under water and so is not well placed to signal its location.
If it floats then it gets blown away from the crash site by the wind.
Which option do people here generally prefer?
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #13 on: 07/06/2009 20:49:46 »
Would it not be a good idea to fit the 'black box recorder' with a beacon which would activate in the case of emergency. If the plane then crashes it could be located, if the plane makes a safe landing or the emergency is overcome, the signal can be switched off.

Both the Cockpit Voice Recorder and the Flight Data Recorder are fitted with beacons but they'll only work for a limited time because they're battery powered.

There are two aspects to the recorders; the collection of data during the flight and the preservation of the data after an incident.  The recorders are not so strongly built that they'll survive a crash in working order, but they are designed to make a good job of preserving the collected data once the unit is damaged.  One of the bits that might be damaged, of course, is the beacon and its battery.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8667
  • Thanked: 42 times
    • View Profile
Why couldn't they find the site of the crash?
« Reply #14 on: 07/06/2009 21:35:05 »
The beacons won't work under water anyway.
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #15 on: 07/06/2009 21:57:37 »
Their locator beacons are designed to operate for 30 days, at depths up to 6000m.

I don't know the specific type of transducer used for the underwater beacon, or its range, but I would guess that it's some type of sound device.
 

lyner

  • Guest
Why couldn't they find the site of the crash?
« Reply #16 on: 08/06/2009 15:26:52 »
A little torch is very hard to see amongst waves. A lifeboat may find it useful as a means of locating you when nearby but a high flying aircraft would need pitch black conditions to spot a little 'twinkle'.

A floating beacon would be quite capable of transmitting the position of its first impact with the sea plus its present position. You needn't have to make a choice of which it does. Dead reckoning would allow the sunken plane to be found a lot quicker if you knew where it hit the sea.
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #17 on: 08/06/2009 19:11:01 »
The beacons aren't just intended to allow the aircraft to be found - they're specifically designed to locate the recorders; in many ways these are more important than the wreckage of the aircraft as they're the only way of knowing what happened before the crash.

Like I said, I don't know the details of the beacons incorporated in to the recorders, but if they are intended to detach from the recorders it would make them pretty useless.  In any case, the specs say that they should operate at depths up 6000m, which implies the beacons do not float.
 

Offline Karsten

  • Hero Member
  • *****
  • Posts: 701
    • View Profile
    • Fortunately still only a game
Why couldn't they find the site of the crash?
« Reply #18 on: 09/06/2009 01:37:23 »
Why not have a back-up device that contains the same info as the black boxes and is specifically designed to be "activated" (whatever that means) when submerged in saltwater? Something that rests dormant but will dissolve and allow it to float to the surface and send a signal so it can be found. I am not sure how this would work with the high underwater pressures or extreme impact forces, but it seems "unprepared" to have a situation where the black boxes cannot be found because the airplane got lost far out in the ocean. Is it not that airplanes these days spend quite some time out there? It probably makes LITTLE (modified June 12, 2009) sense from an economic point of view though. After all accidents during the cruise portion are rare.
« Last Edit: 12/06/2009 20:56:47 by Karsten »
 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Why couldn't they find the site of the crash?
« Reply #19 on: 09/06/2009 14:43:15 »
The ocean depth was reportedly about 2 miles. This is well below conventional submarine depths but can be reached by specialised "submersibles" that can carry a small crew (2 or 3) down to 6000m (about 3.7 miles). The pressures are enormous and these vehicles are a mix of great sophistication and brute strength (5cm thick walls).

The key issue regarding the black box is ensuring it gets released freely from the wreckage. If attached to a ton of metal it is going to sink. But I agree with Karston that it would seem reasonable to ensure that the box itself  could be made to deploy some floatation system in the event of detachment from the aircraft. It would not have to detract from its innate strength to survive an impact or take up a huge amount of space when in the aircraft.

Intrestingly I found this on the web...

"Most general aviation aircraft in the U.S. are required to carry an ELT, depending upon the type or location of operation, while scheduled flights by scheduled air carriers are not. However, in commercial aircraft, a cockpit voice recorder or flight data recorder must contain an Underwater locator beacon."

Also...

"When triggered by water immersion the ULB emits an ultrasonic pulse of 37.5 kHz at an interval of once per second. This signal can be heard and located by a variety of receivers. The beacon will operate for 30 days to a depth of 20000 feet (6 km)."

I assume from this that the Black Box is also designed to survive such depths, so as they have sent submersibles to the site, there may still be some chance of finding the black box.
 

Offline LeeE

  • Neilep Level Member
  • ******
  • Posts: 3382
    • View Profile
    • Spatial
Why couldn't they find the site of the crash?
« Reply #20 on: 09/06/2009 20:36:46 »
Ta for the ULB signal details graham.d.  I'm a bit surprised that the frequency is so high but I guess it puts it well out of the range of 'natural' noises that might occur in the sea/oceans.
 

The Naked Scientists Forum

Why couldn't they find the site of the crash?
« Reply #20 on: 09/06/2009 20:36:46 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums