Korean airplane crash 2

[LittleInch]

All but two presumed dead after Jeju Air plane crash in South Korea – video

The Boeing 737-800 skid along the runway before hitting what appears to be a concrete barrier and bursting into flames at Muan airport in South Korea.

www.theguardian.com

Looks like a near text book landing wheels up until they hit a rather oddly placed concrete wall.

Only two survivors.

 

[Alistair_Heaton]

One radio is normally on the essential power buses and emergency sub bus which are powered under battery backup.

If the cvr and FDR are unpowered I would normally say the radio won't be either.

 

[TugboatEng]

The radio won't be unpowered or will be unpowered?

 

[Alistair_Heaton]

You would need the 737-800 aircraft system documentation to find out.

 

[IRstuff]

Go-Pros are very tiny and easy to lose; additionally, they are not necessarily fully waterproof and unlikely to be fireproof.

The paperwork that everyone harps about is the documentation and certification that such recording devices can survive ANY air crash within the specified requirements for these devices. I have spent a tiny amount time working on FDRs and they have to be fully waterproof, survive fuel explosions and liquid fuel exposure, survive hitting hard surfaces at aircraft speeds, etc. They need to have a rather long service life, which means continuous operations for hundreds of hours, with crazy high reliability. Commercial products just don't have the pedigree for these requirements.

 

[Alistair_Heaton]

Do you know what the requirements are for the power to them is?

 

[Cool_Controls]

The units the L3 make, need 40watts at 28VDC. https://www.l3harris.com/all-capabi...orne-data-recording-acquisition-system-madras

 

[waross]

Go-Pros are very tiny and easy to lose; additionally, they are not necessarily fully waterproof and unlikely to be fireproof.

The integrated circuits, rather than the complete commercial units, may be encapsulated or potted and used inside the Black Box housing.
I shake my head when I hear of the short recording time of aviation recorders, measured in minutes.
Garmin Dash Cams will record Hi-Definition video for several days on a chip smaller than a dime.
I suggest that the circuits in a device that small will have so little inertia as to be almost immune to shock.
Please correct me if I am wrong.

They need to have a rather long service life, which means continuous operations for hundreds of hours, with crazy high reliability.

That's a good description of modern electronic devices.

 

[Alistair_Heaton]

The one fitted to my type have an internal backup battery so it records from the general area mics if still connected even after the aircraft batteries buses become unavailable.

The Jetstreams didn't have this capability. But it was on the 28V DC battery bus.

One of the proper aeronautics engineers might know. There was major change in the certification standards when all this sort of stuff was changed from basically radial piston engine design methods.

It was before I was a teenager in the early 1980's I think.

 

[IRstuff]

That's a good description of modern electronic devices.

Actually, not; modern electronic devices, such as GoPros have decent reliability because they are not constantly exposed to extreme temperature conditions that are required for aircraft, which is on the order of at least -55C to +125C. You can get lucky with commercial electronics, since they have decent reliability. You could pot a GoPro, but it's likely going to fail sooner, rather than later, because the heat will be trapped in the potting material.

Having a GoPro in the cockpit won't necessarily be particularly good in most crashes, as demonstrated in this particular crash, where the two survivors were both in the tail section, which is where most FDRs tend to be located.

The trend now is moving toward automatically deployable FDRs, which could be ejected from the plane in case of water landings, specifically, but also in case of the Jeju Air crash. This now requires the FDR to be located near or on the outer surface of the plane, subjecting the FDR to at-altitude temperatures as well as direct solar heating on the outer casing.

Having a GoPro as a cheap, redundancy measure might be doable, but given the mechanics of this crash, it would still have to harden against both crash shock and fire.

FYI, the MTBF for any single failure mode of one spec that I've seen for ADFRs is on the order of 100,000 flight hours

 

[waross]

Having a GoPro in the cockpit

Just the main chip and memory, and in the Black Box, not the cockpit.

 

[Alistair_Heaton]

There has been talk.of cameras the whole time I have been in the industry.

There is huge push back to not have them by crew due to issues with management and privacy.

 

[LittleInch]

I've been having a bit of a search and it looks like when this aircraft was made you didn't need to have a separate power supply for the CVR and FDR. They hung off the 120V AC bus which could be supplied by either engine, but if not then it wasn't supplied by the battery.

This will still leave a LOT unanswered or unclear as to what actually happened unfortunately. The massive impact and fire will wipe out much of the information you might otherwise get from the debris.

 

[Alistair_Heaton]

It was certified in 1994 and if it had been a new type it would have required it.

I think it was 1978 that came in for new certification.

They managed to get it through 3 weeks before a new set of standards came in.

After the MAX investigation it has been said that there is alot of electrical systems been incorrectly given a waiver for NG certification.

 

[DirteJoe]

GoPros, or any other similar camera system would not handle heavy impacts well. GoPros in particular are known to have data corruption associated with heavy impacts. Pretty common to lose entire recordings that are not recoverable.

So losing the last 4 minuted of data lines up with the loss of ADS-B and the bird strike. Would birds in the engine kill all electrical power instantly? We heard at least one engine running, which unless the generator was the only thing knocked out, they should have had some electrical.

Something still just doesn't seem right. Even if they did shut the incorrect engine down, wouldn't it still produce some electrical power for a little bit of time?

 

[IRstuff]

Just the main chip and memory, and in the Black Box, not the cockpit.

One does not willy-nilly "Just the main chip and memory" into a black box, since all the interfaces have to be modified, etc., etc., and then the entire thing has to be re-qualified. But, if it's "Just the main chip and memory" then it does not need to be a GoPro, and it's still an issue of qualification, testing, etc.

Regardless of what memory it is, or is not, there's a lot of infrastructure involved in the recording, which a GoPro would not have in existence; the memory needs to be an infinite loop, so there's the matter of when and how old data is overwritten, how it's erased, coding to ensure that bad bits don't affect the recorded data, etc., etc.

If the plane is relatively new, it would already have the equivalent circuitry exemplified by a GoPro. The issue with the JeJu blackbox was not a storage problem but a power problem. Having a battery in addition to that of the ELC entails a complete round of qualification testing, reliability analysis, etc.

 

[TugboatEng]

If there is automatic load shedding, non-essential breakers may be tripped immediately upon engine shutdown.

 

[Alistair_Heaton]

Just remember this is a different beast than what you might expect. It's 7th iteration of a 1960's design with a Mish mash of certification regulations depending if a system has been changed or not.

I would be extremely surprised if there is anything automatic in it's electric systems.

The philosophy of the 737 is that the pilots are in control of everything. It's the pilots choice what to shed and how much.

 

[Alistair_Heaton]

As usual about the 737 I am incorrect.

It does have a thing called an ELCU which load sheds and prioritises certain loads during engine starts etc.

It apparently has connections to the primary services such as hydraulic demand, gear and flaps etc.

As the technician I spoke to about it said... Don't even try to understand how it all interlinks on the 737. This thing is easy (A220) it even gives us the page number to look at in the manual.

 

[hacksaw]

Perhaps a survey of current Airport Landing fields in America is advisable...we had a close call in Detroit in 1990, sliding down the runway, heading towards a 30 ft (10 m) barrier. You can bet the pilot had the reverse thrust at full tilt, we made it just in time, coming to a stop

 

[Alistair_Heaton]

see if this works.