B737 Crashes on landing in South Korea

[Snitch]

FCR & CVR power technical explanation

[kudu177]

So a transport ministry probe into Korea's B737-800 fleet has found that 56 out of 101 aircraft are not equipped with aux battery backup power for the FDR/CVR.

Story below (right click to translate ....)

http://www.koreastocknews.com/news/arti ... xno=107141

[Brand Wessels]

As far as I remember it is not a regulatory requirement anywhere for aircraft built before 2010?

[Paul#25]

I had a look in the manuals for the B737-800 aircraft that we maintain for different customers. In all the manuals it shows that the cockpit voice recorder power is from the AC transfer bus 2 with 115v AC only.
This below is an extract from the maintenance manual.
The voice recorder unit gets 115v ac from the voice recorder circuit breaker. The voice recorder unit supplies 18v dc to the audio amplifier in the cockpit voice recorder panel. The voice recorder gets 115v ac from either the time delay relay or the voice recorder switch. When the voice recorder switch is put to ON, the switch applies power to the voice recorder. A latching relay holds the switch in the ON position. This keeps the voice recorder power on for pre-flight checks. When an engine starts, the latching relay opens. This returns the voice recorder switch to AUTO. At the same time, the time delay relay energizes. The time delay relay keeps 115v ac to the voice recorder. When the engines are shut down, the time delay relay keeps the voice recorder on for an additional 5 minutes. This gives time for post-flight checks.
Taking this power supply on the B737-800 into account, if both engines are lost in flight, and the APU isn't started to supply power, the cockpit voice recorder won't be powered.

[Wingnutter]

I had a look in the manuals for the B737-800 aircraft that we maintain for different customers. In all the manuals it shows that the cockpit voice recorder power is from the AC transfer bus 2 with 115v AC only.
This below is an extract from the maintenance manual.
The voice recorder unit gets 115v ac from the voice recorder circuit breaker. The voice recorder unit supplies 18v dc to the audio amplifier in the cockpit voice recorder panel. The voice recorder gets 115v ac from either the time delay relay or the voice recorder switch. When the voice recorder switch is put to ON, the switch applies power to the voice recorder. A latching relay holds the switch in the ON position. This keeps the voice recorder power on for pre-flight checks. When an engine starts, the latching relay opens. This returns the voice recorder switch to AUTO. At the same time, the time delay relay energizes. The time delay relay keeps 115v ac to the voice recorder. When the engines are shut down, the time delay relay keeps the voice recorder on for an additional 5 minutes. This gives time for post-flight checks.
Taking this power supply on the B737-800 into account, if both engines are lost in flight, and the APU isn't started to supply power, the cockpit voice recorder won't be powered.

Unbelievable that they designed a system that stops recording in the event of total power loss / electrical failure - why not power the CVR at least from the standby electrical system. My iPhone records high quality video / audio for the best part of a day on a 3500 mah battery - maybe they should just put one of those in the cockpit in a mous case!

[Wingnutter]

Supposedly feathers found in both engines according to Reuters:

https://www.reuters.com/world/asia-paci ... H_VhmZGtXg

[Paul#25]

I had a look in the manuals for the B737-800 aircraft that we maintain for different customers. In all the manuals it shows that the cockpit voice recorder power is from the AC transfer bus 2 with 115v AC only.
This below is an extract from the maintenance manual.
The voice recorder unit gets 115v ac from the voice recorder circuit breaker. The voice recorder unit supplies 18v dc to the audio amplifier in the cockpit voice recorder panel. The voice recorder gets 115v ac from either the time delay relay or the voice recorder switch. When the voice recorder switch is put to ON, the switch applies power to the voice recorder. A latching relay holds the switch in the ON position. This keeps the voice recorder power on for pre-flight checks. When an engine starts, the latching relay opens. This returns the voice recorder switch to AUTO. At the same time, the time delay relay energizes. The time delay relay keeps 115v ac to the voice recorder. When the engines are shut down, the time delay relay keeps the voice recorder on for an additional 5 minutes. This gives time for post-flight checks.
Taking this power supply on the B737-800 into account, if both engines are lost in flight, and the APU isn't started to supply power, the cockpit voice recorder won't be powered.

Unbelievable that they designed a system that stops recording in the event of total power loss / electrical failure - why not power the CVR at least from the standby electrical system. My iPhone records high quality video / audio for the best part of a day on a 3500 mah battery - maybe they should just put one of those in the cockpit in a mous case!

As a comparison, the Airbus A320's cockpit voice recorder is supplied with 115v AC power from the AC Shed Essential Bus and 28v DC from the DC Shed Essential Bus. Both of these electrical busses are powered from the Constant Speed Motor Generator which is driven by hydraulics from the RAT (Ram Air Turbine) that is automatically deployed when all power from the engine generators is lost in flight.

[hans39]

Saw on Chinese Global TV streaming news headlines that a report from Seoul stated that traces of bird remains and feathers had been found on both engines.

[Thermalator]

Supposedly feathers found in both engines according to Reuters:

https://www.reuters.com/world/asia-paci ... H_VhmZGtXg

Fake/misinformation news, the article says opposite of the headline !!

[Volo]

For Boeing to have produced a system that cannot record the data and crew voice right up until the end of an accident sequence speaks of a fundamental flaw in their design philosophy as evidenced by other omissions like MCAS .

[Brand Wessels]

For Boeing to have produced a system that cannot record the data and crew voice right up until the end of an accident sequence speaks of a fundamental flaw in their design philosophy as evidenced by other omissions like MCAS .

Actually, I would say the opposite. It is the correct engineering decision. The aircraft are build for airlines. Airlines want lowest cost and maximum payload.

Equipment like CVR and FDR are added for the regulators (no direct benefit to the airlines), and they eat into payload and price, so they are a grudge sale at best. Especially for equipment which is typically never actually used in the entire life of an airframe.

So engineers will produce the most economical design that meets the regulator's requirements. Any additional weight/complexity/cost is just plain bad design.

And when you get right down to it, if you have already lost both main AC busses, then everything relevant to investigating the failure is likely already recorded. After that point the plane is just a glider, and you are only recording crew actions up to the landing - information which is irrelevant to the airframe manufacturer.

[Patrick AL]

For Boeing to have produced a system that cannot record the data and crew voice right up until the end of an accident sequence speaks of a fundamental flaw in their design philosophy as evidenced by other omissions like MCAS .

Actually, I would say the opposite. It is the correct engineering decision. The aircraft are build for airlines. Airlines want lowest cost and maximum payload.

Equipment like CVR and FDR are added for the regulators (no direct benefit to the airlines), and they eat into payload and price, so they are a grudge sale at best. Especially for equipment which is typically never actually used in the entire life of an airframe.

So engineers will produce the most economical design that meets the regulator's requirements. Any additional weight/complexity/cost is just plain bad design.

And when you get right down to it, if you have already lost both main AC busses, then everything relevant to investigating the failure is likely already recorded. After that point the plane is just a glider, and you are only recording crew actions up to the landing - information which is irrelevant to the airframe manufacturer.

-at no point does human/animal crew/passenger safety come into your consideration....?

[Hexapilot]

I am still baffled that the reverse thruster was deployed on, at least what I can see, the RH engine.
What powers that and no power to the CVR/FDR?

[StressMerchant]

-at no point does human/animal crew/passenger safety come into your consideration....?

As noted:
1) CVR and FDR do not in any way affect the safety of the flight. They only assist with accident investigations (which can potentially affect safety of future flights).

2) All important causal factors are likely to be logged by the time the second AC bus shuts down. If you know what triggered the bus shut-downs, then you know the likely cause. There is unlikely to be any information to record after that point which is relevant to airframe safety.

[Aquila]

For Boeing to have produced a system that cannot record the data and crew voice right up until the end of an accident sequence speaks of a fundamental flaw in their design philosophy as evidenced by other omissions like MCAS .

Actually, I would say the opposite. It is the correct engineering decision. The aircraft are build for airlines. Airlines want lowest cost and maximum payload.

Equipment like CVR and FDR are added for the regulators (no direct benefit to the airlines), and they eat into payload and price, so they are a grudge sale at best. Especially for equipment which is typically never actually used in the entire life of an airframe.

So engineers will produce the most economical design that meets the regulator's requirements. Any additional weight/complexity/cost is just plain bad design.

And when you get right down to it, if you have already lost both main AC busses, then everything relevant to investigating the failure is likely already recorded. After that point the plane is just a glider, and you are only recording crew actions up to the landing - information which is irrelevant to the airframe manufacturer.

Yet Airbus decided differently?