Ask The Pilot

[jb747]

One channel though, was interesting. 4 ex US military and now commercial pilots on the "Mover and Gonky" channel just covered it. They seemed to think that declaring an emergency was OK. One of them thought that anything more would be extraneous comms.

Wags is a game developer for Digital Combat Simulator. I don't think he's a commercial pilot. Mover and Gonky do a bit of youtube flying the F16 and 18 in that game.

It doesn't take much to say Mayday. Once will do for a start. What they're talking about might work in the USA, though the aircraft doesn't seem to have been processed by ATC as an emergency aircraft. Perhaps they were waiting for the magic word(s) which never came. But, as soon as you start flying in areas for which English is not the native language, going off the ICAO script is a sure way to confuse things, and that will lead to much more discussion.

Thoughts, JB, given that you've actually experienced such an incident but at cruise altitude.

I think the passengers near the door were in great danger, especially in the first few seconds. They were extremely lucky that it wasn't higher, and that the seat was unoccupied. I don't think the aircraft was in any danger of coming apart, as the failure was contained entirely within a door frame. Whether there was secondary risk of the door hitting something on the tail as it went past, we might find out in the report (in a year or two).

And that coughpit door opening is just so wrong.

 

[flyer89]

And that coughpit door opening is just so wrong.

So it was designed to do this? But they didn’t tell anyone about that minor detail and are now going to update the manuals?

They have replaced blow outs with the door swinging open violently?

Stick a fork in me…..

 

[JohnM]

And that coughpit door opening is just so wrong.

Juan Browne had some comment on that towards the end of today's post:

 

[Quickstatus]

Can someone confirm that communication between crew does not occur via the Headsets in a Boeing flightdeck?

And that coughpit door opening is just so wrong.

How does differential pressure equalise between flightdeck and cabin if the post 9/11 coughpit door is not suppose to open?

 

[AviatorInsight]

So it was designed to do this? But they didn’t tell anyone about that minor detail and are now going to update the manuals?

They have replaced blow outs with the door swinging open violently?

Stick a fork in me…..

The pressure panels will open. And by open I mean just fall out from the inside. They are still attached by straps. In the event of a door jam you can unlock the release pins and then the whole panel will come off and you can then get out from the flight deck into the cabin.

Straight from the MAX manual:

The door incorporates two pressure sensors that unlock the decompression panels in the event pressurization is lost. The decompression panels have manual release pins. Pulling the pins frees the panels allowing egress in the event the door is jammed.

So if it’s actually true that the whole door blows open, (which I fail to see how seeing that as long as there is power the door just does not unlock itself) in a rapid decompression then that is definitely concerning.

 

[AviatorInsight]

Can someone confirm that communication between crew does not occur via the Headsets in a Boeing flightdeck?

All comms occur via the headsets or the speakers and hand held mic if you’ve taken your headset off. There is no phone like the 777.

 

[Quickstatus]

All comms occur via the headsets

Thanks. I can flick that off into the fake news bin

 

[flyer89]

The pressure panels will open. And by open I mean just fall out from the inside. They are still attached by straps. In the event of a door jam you can unlock the release pins and then the whole panel will come off and you can then get out from the flight deck into the cabin.

So it’s just standard blow out panels like usual then? The reporting on this (from the NTSB) is very confusing. They specifically stated that the door was ‘designed’ to open during a loss of pressure.

 

[AviatorInsight]

So it’s just standard blow out panels like usual then? The reporting on this (from the NTSB) is very confusing. They specifically stated that the door was ‘designed’ to open during a loss of pressure.

Yes that’s my understanding of it and why I was so confused when I read that too. Of course I can’t find anything that would lead me to believe the door would just fly open.

Unless electrical power was lost, the door will remain locked. So I’ll be waiting and watching to see what gets “put in the manuals”.

 

[RooFlyer]

In the Juan Browne discussion, posted by JohnM, Browne mentions that the circuit breakers for the coughpit voice recorder weren't pulled at the end of the 20 minute flight, so the recordings were later over-written and the CVR data for the flight lost.

How mechanically could they be over-written? Do they just keep rolling even when the coughpit is unoccupied? Assuming the aircraft was shut down say 60 minutes after landing, how would the CVRs keep recording to over-write the old data? I assume the NTSB would want the aircraft 'sterile' after an incident, so you'd think that there wouldn't be anyone in the coughpit afterwards.

 

[AviatorInsight]

In the Juan Browne discussion, posted by JohnM, Browne mentions that the circuit breakers for the coughpit voice recorder weren't pulled at the end of the 20 minute flight, so the recordings were later over-written and the CVR data for the flight lost.

How mechanically could they be over-written? Do they just keep rolling even when the coughpit is unoccupied? Assuming the aircraft was shut down say 60 minutes after landing, how would the CVRs keep recording to over-write the old data? I assume the NTSB would want the aircraft 'sterile' after an incident, so you'd think that there wouldn't be anyone in the coughpit afterwards.

The CVR in the MAX can record for 25hrs vs just 2 for the NG. There is a recorder independent power supply that provides power to the CVR for 10mins after the aircraft is shut down.

Not sure why they would pull the breaker for it. The recording for the CVR will usually start again during the preliminary pre flight procedure when the FO will switch it on to record pre flight briefings etc.

 

[jb747]

Yes that’s my understanding of it and why I was so confused when I read that too. Of course I can’t find anything that would lead me to believe the door would just fly open.

Unless electrical power was lost, the door will remain locked. So I’ll be waiting and watching to see what gets “put in the manuals”.

Manual update...."in the event of a depressurisation, the aircraft will randomly disassemble itself, as a way of finding areas in which bolts were not installed during assembly". No pilot action, Boeing considers this normal.

In the Juan Browne discussion, posted by JohnM, Browne mentions that the circuit breakers for the coughpit voice recorder weren't pulled at the end of the 20 minute flight, so the recordings were later over-written and the CVR data for the flight lost.

How mechanically could they be over-written? Do they just keep rolling even when the coughpit is unoccupied? Assuming the aircraft was shut down say 60 minutes after landing, how would the CVRs keep recording to over-write the old data? I assume the NTSB would want the aircraft 'sterile' after an incident, so you'd think that there wouldn't be anyone in the coughpit afterwards.

Actually I made this mistake. Having landed in Manila, it took until after the passengers were all off before it occurred to me to think about the CVR. It needs a circuit breaker to be pulled, not something we normally do, to shut it down completely. The aircraft remained powered until well after it landed. I'm not sure when it was shut down, but probably not until it had been towed away from the terminal. In the 747, the CVR operates at any time the #3 AC bus has power, and as we'd started the APU, it continued to have electricity, and so was running. It has no on/off switch. I pulled the breaker, and apparently the start time of the recording was after the big bang. More recent recorders have much longer run periods, so this no longer matters.

Part of the thinking with CVRs, and a reason that two hours was acceptable (for long after it was possible to have more) was that the recording would end at the crash, and so two hours would be more than enough to cover any event. They just didn't seem to be considering the cases where the event has a happier ending.

Sound like Alaskan chose the 'vintage' option if they only had two hours. Goes with the self opening security door, I guess.

 

[serfty]

Sound like Alaskan chose the 'vintage' option if they only had two hours. Goes with the self opening security door, I guess.

Apparently there is US Pilot Union resistance to having more than two hours.

https://viewfromthewing.com/exposed...ilot-unions-resistance-to-key-safety-reforms/

Regulations.gov

www.regulations.gov

For Example:

If CVR's have 25 hours of residual memory, it will give the airlines incentive to download the CVR's after a day of flying and use it to spy on their pilots. The airlines will undoubtedly use CVR's in a punitive manner and fire a pilot for something they said, even if no incident or accident occurred. The airlines cannot be trusted to not utilize the CVR system in a manner outside of the scope of the CVR's intended function. The 2-hour CVR rule is appropriate as it stands to determine the cause of an aviation accident. Determining the cause of an incident in which no injury or accident takes place is beyond the scope of the purpose for mandating CVR's as they are originally intended.

 

[jb747]

If the FAA seriously wanted more, then it would be easy enough to enact rulings making it illegal for companies to download the data. I certainly can’t see any reason why they would need any access at all.

 

[Quickstatus]

Why would 25hrs of CVR be necessary?

 

[jb747]

Yes that’s my understanding of it and why I was so confused when I read that too. Of course I can’t find anything that would lead me to believe the door would just fly open.

Unless electrical power was lost, the door will remain locked. So I’ll be waiting and watching to see what gets “put in the manuals”.

Been doing a bit of revision on this stuff (who thought I'd be reading a Boeing manual 15 years after I last flew one).

The 744 manual states "The door latch system incorporates a pressure rate-sensor that unlocks the door in the event of flight deck depressurisation." Of course, unlocking should not be the same thing as opening. It also means that the door won't unlock in the case of a slow depressurisation, which is exactly the time you might want it to unlock (Helios).

The A380 was quite a bit more complex, having a couple of layers of defence. The first is a depressurisation panel that opens with quite a small differential. The second is a rate switch which also unlocks the door, but which activates at what would seem to be a pretty extreme pressure rate of change. There is also a system to stop the door from slamming open if you do manage to hit the unlock point.

And it harks back to QF30, which we know depressurised in 13 seconds. That means the cabin went from about 11 psi to roughly 4.5 psi in 13 seconds, a rate of change of .5 psi/sec. Converting that back to a feet per minute rate of climb, and you end up over 100,000 fpm. Now that's spectacular number in itself, but the switch that Airbus use to unlock the door requires a rate that is 20 (!) times greater. That's such a huge number that I read it a number of times to make sure I didn't have it wrong. I cannot see that any situation that would leave the aircraft in one piece could ever hit that sort of number.

 

[jb747]

Why would 25hrs of CVR be necessary?

Sunrise?

As these are solid state, I suspect that the hardware difference to have anything from 1 hour to 100 hours, is minimal. So perhaps it's a number chosen to minimise pushback over privacy and company behaviour concerns. I can see cases where the accident investigators could have had value from being able to look further back, even to previous flights.

 

[Quickstatus]

unlocking should not be the same thing as opening

But without also opening how then would the pressure differential equalise?

Sunrise

You mean the Project?.

How would pilots chatting on previous flights inform a crash investigation?

 

[jb747]

But without also opening how then would the pressure differential equalise?

coughpits are not air tight. Any pressure would leak out to the cabin around doors, through vents, and and the myriad panel gaps. But, as AV has added, the 737 Max has panels that release to allow the air to escape, so basically any differential would not exist for long. A depressurisation takes time. With the exception of the Aloha 737, none of these are explosive decompressions. They are all defined as rapid. Explosive means the pressure loss is effectively instantaneous, and that simply won’t happen in an airliner without leaving you with a debris cloud. They are something the military has to consider, as that’s what the loss of a canopy at altitude gives you. And that is why aircraft that could suffer from an explosive decompression are only pressurised to about half of their actual altitude (and why wearing masks in fighters is not optional, even for Tom Cruise).

And I’ll say it again, QF30s door did not open. It may have unlocked, though I don’t recall that as an EICAS message. I might still have the list somewhere, so I’ll have a look.

You mean the Project?

I’m sure there’s an airline CEO somewhere for whom 300 people in a 737 for 24 hours is a wet dream.

How would pilots chatting on previous flights inform a crash investigation?

Issues may have come up earlier in a flight, or a previous one, and the way they were handled could have some relevance. It’s not about chatting, but sadly that’s the issue, and it’s why tapes should not be released to the public, nor should they be accessible to the company. Some countries won’t allow the tapes to be misused, whilst for others the police (who should have nothing to do with accidents), and media, would be salivating.

 

[flyer89]

I’m sure there’s an airline CEO somewhere for whom 300 people in a 737 for 24 hours is a wet dream.

I think that individual should be tried at The Hague for cruel and unusual punishment.