Airbus A320 Family Non-Normal Notes [pdf] | Hacker News Reader

Airbus A320 Family Non-Normal Notes [pdf]

hursts.org.uk

62 pointsTomte40 comments

2.13. Computer reset

"Abnormal computer behaviour can often be stopped by interrupting the power supply of the affected computer."

I didn't expect a more eloquently phrased "have you tried turning it off and on again" in this manual.

Had that happen before a flight once. They said there was some weird behavior and they'd powercycle the entire plane for a few seconds. Everything went dark for a bit and apparently it was fine afterwards.

I think it was an Embraer E-170.

I’ve experienced that while on the ground (also an Embraer I think). Was your experience in the air? I think I’d hold my breath if that happened while mid flight.

While I understand that it's part of the procedure and flying is generally very safe, I'd be holding my breath, armrest, and fellow passengers with a vise grip if they power cycled my plane mid-flight.

The commenter said “before” the flight, so I think it was on the ground.

Heh, it's like rebooting the tablet in my Tesla 3 by holding both scroll wheels for 10 seconds. It's both creepy and reassuring that the car operates just fine even when you can't see your speed, hear your turn signals clicking, and so on. The separation between body control modules and "user-facing" controls gives me more confidence in the face of potential bugs.

I love IT Crowd's first scene introducing Moss & Roy. Roy saying "Have you tried turning it off and on again?", then Moss saying "Have you tried forcing an unexpected reboot?".

See also: the 787, which for a while would lose all controls for a brief period if left turned on for 22 days.

https://www.seattletimes.com/business/boeing-aerospace/faa-o...

Regarding a bomb on board: “In the cabin, procedures are laid down for assessing the risks of moving the device and for moving the device to the LRBL at door 2R.”

LRBL is “least risk bomb location” and is apparently required by the FAA: https://www.faa.gov/documentLibrary/media/Advisory_Circular/...

This is fascinating, thank you for the link. Makes perfect sense when you think about it, identifying the least vulnerable location on an aircraft but not something I would have ever considered was part of the formal specifications.

Interesting. Outside of bombs, the most crash survivable area to sit is a middle seat in the rear third of the cabin.

Since you want the bomb behind the engines to avoid ingesting debris, you would likely have to put the bomb in this previously "more survivable" area.

I did not know about the rear third being more survivable. Do you have a source? Not doubting, just curious why.

Sure. https://time.com/3934663/safest-seat-airplane/

2R (from the document) actually seems to be the right front door.

2R would be the right overwing door on the A320. Interesting, I wouldn't have guessed that was the best place.

2R is the right rear door; the overwing emergency exits aren't considered doors (presumably because they aren't doors).

I found this part about unreliable airspeed indicators interesting: "Thus flight envelope protections based on airspeed data from unreliable ADRs may activate. This may lead to pitch inputs from the flight computers that cannot be overridden with the sidesticks. In this case, immediately switch off any two ADRs"

Aside from actually having plenty of redundancy to avoid this scenario (this can only happen if two out of three sensors fail), this is basically the Airbus equivalent of MCAS. I wonder how well documented (and trained) this scenario is (and suspect that pilots are a lot more aware of it).

Heres what happens when that happens:

https://en.wikipedia.org/wiki/Qantas_Flight_72

Television special about that flight:

https://www.youtube.com/watch?v=0cS1SMptlnQ

> this is basically the Airbus equivalent of MCAS

I believe the Airbus flight envelope protection uses the same surfaces normally controlled by the sidesticks, ignoring the pilot inputs (which is possible because they're fly-by-wire), while Boeing's MCAS uses the pitch trim (since it cannot ignore the pilot inputs due to them being mechanically linked with cables).

> I wonder how well documented (and trained) this scenario is (and suspect that pilots are a lot more aware of it).

Here's a case of unreliable airspeed in which the three ADRs were turned off by the pilots: https://www.atsb.gov.au/publications/investigation_reports/2... ("In accordance with published procedures, the flight crew turned off the three air data reference systems (ADRs)"), so it does seem to be documented/trained.

And the 777, which is FBW, has the same control protection as the Airbus jets. It's that the 737 is a completely obsolete design and duct-taping 2015 tech onto it was impossible.

Air France 447 was another example.

https://www.vanityfair.com/news/business/2014/10/air-france-...

I thought the unreliable airspeed indicators section was particularly interesting because it can be read as a list of everything that the Air France Flight 447 crew did wrong...

> I wonder how well documented (and trained) this scenario is (and suspect that pilots are a lot more aware of it).

One Airbus plane was lost because of that. I believe it was icing caused by maintenance staff cleaning the exterior and getting water on the various static ports, which then iced over.

I think 5 people died.

Actual homepage (with some minimal explanation of what it is about):

https://hursts.org.uk/

and where there is a "plain" html version:

https://hursts.org.uk/airbus-nonnormal/html/index.html

Only vaguely related to the original article but I've often wondered what causes the loud screeching noise as an Airbus 320 shuts down. I did a bit of reading around it and came to the conclusion it is actually the PTU (basically a hydraulic motor directly coupled to a hydraulic pump which allows coupling the hydraulic power between the two systems without risking bringing down both in the event of a failure) trying to keep the pressure in one system up as the engine driven pump stops.

Anyone happen to know if I'm correct?

Yes it’s the PTU. If the noise is in the parking with engines stopped it maybe the yellow electric pump, used to open and close the cargo doors.

I'd recommend asking on aviation.stackexchange.com

You are correct. Here's[0] a great video on the subject if you're interested.

[0] https://m.youtube.com/watch?v=SCplhq1xoYE

"Removed section with reference to “if engines are running” from Section 9.1, “Dual engine failure” since this is clearly nonsense. Sorry."

I've heard about this procedure, makes me chuckle every time (in case of volcanic ash encounter).

"Damage to the windshield may necessitate an autoland or landing with a sliding window open."

The BA flight 9 crew had only a tiny, semi-opaque, portion of the windscreen to peer through after flying through volcanic ash. Landed safely. https://en.wikipedia.org/wiki/British_Airways_Flight_9

Flight crew did all the right things and saved the aircraft and passengers. Brilliant improvisation saved the day and the tale made better with post-incident interviews: 'Moody described it [glide slope calculation] as "a bit like negotiating one's way up a badger's arse."'

The announcement from BA9 is still a work of art:

> Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.

Yeah, same for me. I wonder if the sliding window is on the side, so the pilot has to actually stick his head out to see where they are going?....

The view out the side window is pretty good for straight ahead! It is more on the corner than the side of the flight deck, so it can be used to see straight ahead if needed. Here is the view out of this side window: https://www.youtube.com/watch?v=vyRVyNO-nYo

And using the sliding window: https://youtu.be/6T9OWQBh0jk (A330, but pretty much the same cockpit)

At the end of the "Volcanic Ash Encounter" section:

> Damage to the windshield may necessitate an autoland or landing with a sliding window open.

Landing while sticking your head out the window is sure going to be interesting...

I love page 117

"You’re going to need a longish runway. Worst case is if you only have blue, since you have, at best, accumulator braking and you’re coming in fast due to lack of flaps. Yellow is better since you have alternate braking, and its mainly about the lack of slats. If you have green, its not really all that bad."

Context for posting this?

In addition, what source is this from?

Context is aviation software has been in the news lately so yNews is geeking out.

Reply on news.ycombinator.com