Ever since the invention of Flight Data Recorders (FDR) and Cockpit Voice Recorders (CVR), they played a crucial role in helping investigators determine the cause of accidents. Since they are so crucial, both are designed to withstand tremendous G forces and high temperature (to protect against fires). However, the nature of some crashes are impossible to withstand, or the crash site made the discovery of FDRs and CVRs virtually impossible (for example see South African Airways Flight 295, United Airlines Flight 389, BOAC Flight 911, etc., there's actually a lot of them, see list of crashes where FDR is never recovered). There are also cases where the aircraft disappeared, or no or only partial wreckage were ever found, not including FDR or CVR (these cases usually happens over oceans, or occasionally over jungles/forests, places where locating the wreckage would be an almost impossible task; see Dominicana de Aviación Flight 603 and the famous Malaysia Airlines Flight 370). Thus, my question is, why didn't they design a FDR and CVR that ejects itself from the aircraft using ejection seat mechanisms prior to an imminent crash? Since data recorders are so important to investigations, they should be guaranteed to be found and not damaged. Although most of the time recorders survived the crash and were found, there's always the possibility of an unsurvivable crash or undiscoverable crash site. Consequently, ensuring the safety of recorders are extremely important. Are there any practical reasons for why such a device wasn't designed and used? I appreciate any help. Thanks in advance!
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3$\begingroup$ For civilian aircraft they are under development, see skybrary.aero/articles/… $\endgroup$– busdriverCommented Aug 1 at 6:30
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3$\begingroup$ In the late 70s when I was working on DHC-5 Buffalos, some of them had an option for an ejectable ELT. It sat on top of the fuselage and could be remotely released. It was a bright orange rounded square shaped lifting body glider that would descend in a circle when released. $\endgroup$– John KCommented Aug 1 at 14:01
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2$\begingroup$ United 389 was a CFIT crash; it's not clear to me what sensor data you could use to trigger the auto-ejection in a case like that. $\endgroup$– Michael SeifertCommented Aug 1 at 21:07
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2$\begingroup$ How do you tell the difference between an impending crash and an impending landing? $\endgroup$– MarkCommented Aug 1 at 22:38
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2$\begingroup$ Surely it's easier to find an FDR if it is still part of the main wreckage, in the known location within what's left of the aircraft, rather than a small item somewhere a couple of miles away in impenetrable jungle? Look at the case of that bloke that went missing in Tenerife - a much larger item to find, and it took about two weeks to find him, and that was with loads of people looking. $\endgroup$– MikeBCommented Aug 2 at 10:10
3 Answers
Yes. Self-ejecting flight recorders can be found on some new airliners, called Automatic deployable flight recorders.
They are currently available for the A320, A330, and a factory option on the A350. Reports say the A350 involved in the runway collision was equipped with one, though I could not find reports on whether it deployed and where it was found.
An alternate solution has been proposed to be a system which can uplink large amounts of data to a satellite network immediately before a crash. Ultimately, this may be the more reliable data recovery solution, but we aren't there yet in terms of satellite networks.
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6$\begingroup$ I'm pretty sure Starlink could do it today, but there are still a couple of problems: 1) Obiovusly, Starlink can only legally operate where they have a license, when they overfly a country they don't have a license for, they need to turn the radios off – that is the case currently in Greenland, India, Kazakhstan, most of Africa, China, and the "usual suspects" (Iran, Afghanistan, Russia, Belarus, Cuba), among others. 2) Vendor lock-in: there is no competitor. 3) SpaceX's rapid iterative development does not play nice with traditional certification processes. $\endgroup$ Commented Aug 1 at 10:38
Civil aviation
This wasn't used since recently but after two tragedies, AF447 in 2009 and MH370 in 2014, it was clear the current equipment wasn't totally adequate, for the former it was difficult and costly to determine the crash site and recover the recorders using ELT or ULB signals, for the latter accident it wasn't possible.
ICAO recommended to extend the mandatory recording time and the homing beacon battery lifetime, and to use ejectable recorders for flights beyond radar coverage. More in: ICAO Global Aeronautical Distress & Safety System (GADSS) and Annex 6 Part I.
As of today:
The homing beacon lifetime has been extended from 30 days to 90 days.
EASA and FAA have made 25 hours recording time mandatory for aircraft with a mass 27,000 kg and more.
Ejectable recorders are not yet mandatory (actually FAA deems them not necessary) but are used on a few Airbus aircraft.
The goals are:
To ease investigation by providing a longer recording time to allow investigate cases like MH370. If the CVR had been recovered, two hours of recording would not have been enough.
To ease detection and recovery of the aircraft and its recorders, to prevent long search times with costly means as for AF447. Currently recorders are associated with an ultrasound beacon to find them under water, but the beacon stops transmitting when the battery is exhausted. Search and rescue (SAR) teams have then to rely on sophisticated rovers mapping the ocean floor rather than on simple acoustic or radio direction finding devices and sonars.
As regards for the possible loss of data, the past accidents have shown recorders can be successfully recovered and read with a high rate. Adding a recorder can help increase this rate.
The ejectable recorder is aimed to equip aircraft used on long range flights, with over-water portions out of radar sight. Aircraft for short range flights are easier to localize as they are always under radar surveillance, both secondary radars relying on the transponder and independent primary radars used by military to detect non-cooperative intruders close to or in their sovereign airspace.
Automatic Deployable Flight recorders (ADFR) separating from the aircraft in case of crash are used on Airbus (A350) and a few other Airbus models since 2019. They are located in the vertical stabilizer. The mandatory recorder (in this case one combining voice and data) is still present in the forward section of the aircraft. This fixed recorder is able to record data until the the sensors or the cables are destructed.
ADFR principle, from SKYbrary:
- Sensors detect the start of a crash.
- Deployable unit releases from the aircraft. If the aircraft is in the air, aircraft movement assists the separation of the device. If the aircraft is underwater, the unit surfaces due to being lighter than water.
- Deployable unit lands safely away from the crash site. If it lands on water, it can float indefinitely.
- The ELT transmits the location and ID of the aircraft emergency beacon via satellite to SAR authorities.
The big improvement is the recorder is equipped with a buoyant radio beacon (ELT). The radio beacon can transmit its position to SAR satellites (Cospas-Sarsat); even if it drifts away from an ocean crash site, the first transmission will indicate the GNSS aircraft location.
Deployable recorders are a partial solution along with other surveillance projects like Space-Based ADS-B deployed by Aireon. Space-Based ADS-B allows ADS-B Out location messages ("extended squitters") sent by aircraft to be received from everywhere, including when flying over oceans. The place an aircraft crashed can be determined by Space-Based ADS-B if the aircraft is using this reporting mode.
There are also projects to stream recorder data via satellite and also to access them remotely. For instance EU is funding projects:
Progress on research into both the real-time tracking of aircraft and the possibility of accessing flight-recorder information without the flight recorder being physically present should be encouraged to improve the tools available to investigators for determining the causes of accidents and to enhance capabilities for preventing recurrent incidents.
An idea is to detect when this streaming must be triggered, rather than continuously streaming with a large throughput. Simulations conducted by the French BEA have shown this is feasible using existing satcoms.
Military aviation
Military aircraft have been fitted with ejectable recorders since a long time.
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2$\begingroup$ One change they should make is The pilot should not have the ability to wipe recordings. If they move to a SOLID state recorder then can also record nearly unlimited voice and frankly if the pilots or maintenance is doing something wrong they should not have the ability to cover that up. I have worked in environments where 100% of the time. You have zero expectation of privacy while on the job site. Aircraft cockpit environments should be held to similar standards with the CVR on all the time and record a month minimum. You can still have conversations, just know they are recorded. $\endgroup$ Commented Aug 1 at 13:01
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4$\begingroup$ @RowanHawkins: All modern recorders, voice or data or combined are digital and use memories. Whether pilots should accept new rules for the CVR is not exactly the topic (but I agree). Anyway, all these considerations will be outdated soon as the future of recorders is to use up-streaming to tracking satellites. Airbus has already solutions improving ACARS. $\endgroup$– minsCommented Aug 1 at 13:07
No, Mainly because the devices need to record up to the end of the flight. It hasn't been until the last decade or so where our infrastructure could even manage the data flow that could allow external recording of that data to be streamed out of the aircraft, and in several of your examples happened where that infrastructure was not even available.
The other logical problem would be because the FDR and CVR are located in a specific area of the craft, it limits the area you would need to search for it greatly increasing the likely hood that it WILL be located. If you started popping it off it could be anywhere. Looking at "needs survive some force," build to the protection of the craft in question, I would much rather be in a crashing plane than having a crashing plane land on me.
Then there is the water scenario, the pinger only runs for a day or two if you are looking for a shoe box in the bottom mud of the ocean, it gets back to the locatability of the devices, if the pinger gets me to the aircraft, I can take longer than 2 days to recover it because I know where in the craft the device is located.
If it is just the boxes, it is very dark at the bottom of the ocean, an aircraft is pretty big, but not in ocean sized scales. Have someone else hide your wallet in a pitch black room with other stuff in it. Your search tool is a penlight with a weak battery you can only use from the floor above. Sadly this search is probably easier than the search for the Malaysian flight. That is because items need a few months under deep water to be really visible to sonar.
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3$\begingroup$ Actually, they can be very feasible. The recorder would deploy when certain G-force threshold is exceeded so staying with the airframe until crash. As for ditching, a deployable recorder is floating. The idea is that they would not sink with the hull but would eject and float at the time of water impact. $\endgroup$ Commented Aug 1 at 7:30
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5$\begingroup$ According to user71659's answer, Airbus already offers these for some aircraft. The "need to record up to the end of the flight" is handled by the deployable FDR (ADFR) being a backup unit, so the "old-style" FDR (or rather, the mixed CVDR) stays with the plane until the bitter end - although I'd imagine that the most valuable data is the one recorded before the "significant structural deformation or impact with water", not after. $\endgroup$– rob74Commented Aug 1 at 10:13
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1$\begingroup$ All of the other answers above were created after mine. I was't aware of the Airbus Option, but I know Boeing doesn't have that capability. Like I say in my answer it hasn't been until recently that data bandwidth availability such as Starlink has been available. Ejectable FDR/CVR isn't something that can be retrofit into the thousands of planes already in the air ..easily. $\endgroup$ Commented Aug 1 at 12:47