Camohe From Australia, joined Oct 2006, 48 posts, RR: 0 Posted (6 years 5 months 1 week 5 days 13 hours ago) and read 2672 times:
Hi, I've recently joined the forum and am really enjoying it. As simply a curious pax I've got 2 questions I'd like to ask about incidents I've had on QF 744's that I've always wondered about...
1. 1998 LHR-BKK. Was fast asleep when all cabin lights came on and recorded announcement "The aircraft has suffered a loss of cabin pressure...put on your oxygen masks etc". The masks didn't drop and captain came on to assure everyone it was a false alarm. The FA told me it was due to a pax using supplementary oxygen and someone disconnecting the mask despite being told not to. I can tell you it sure caused a commotion in the cabin. I remember a panicked woman in front of me trying to use her finger nails to prise open the panel to get at her mask.
Is it true that disconnecting someone's supplementary oxygen can cause this?
2. 2000 SIN-FRA in seat 1A. Was the only pax in first 2 rows. Fast asleep (again) when woken by 2 loud bangs followed by a vibration through the floor for about 5 sec. Got up and saw all other pax still asleep so opened closet that backs onto nose cone and could hear a (much fainter) rythmic banging. I found a FA and told him. He came and had a listen then went upstairs and told the captain. After a while he came back (noise now gone) and said "The captain says thanks very much. Thought they could hear something upstairs but weren't sure. It was a faulty radar and he's shut it down."
Just wondering what may have happened and how many radars there are on a 744? Thanks.
Curmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22 Reply 1, posted (6 years 5 months 1 week 5 days 13 hours ago) and read 2666 times:
1. No. There was a run of bad sensors that triggered these nuisance warnings.
2. Two, used on alternate days typically. The radar antenna sweeps constantly, so a mechanical failure of a support bearing would have sounded as you described.
PhilSquares From , joined Dec 1969, posts, RR: Reply 4, posted (6 years 5 months 1 week 5 days 12 hours ago) and read 2652 times:
1) As mentioned, it was just a faulty sensor in the cabin pressure system that triggered the automatic announcement.
2) I don't know of any airlines that use the two different radar systems on different days, but generally it's one system east bound, the other west bound, or it's tied to even/odd flight numbers, for example XX 1 would use it in Sys L and XX 2 would use it in Sys R. There are two independent radar systems except for the actual antenna and associated motor and mounting system.
AJ From Australia, joined Nov 1999, 2376 posts, RR: 27 Reply 6, posted (6 years 5 months 1 week 3 days 20 hours ago) and read 2367 times:
Sorry to contradict you guys but we did have a spate of problems with the therapeutic oxygen system on our 747-400s. If a passenger was using the system and simply unplugged from the receptacle in the PSU the back pressure would cause a triggering of the passenger oxygen system ancillary functions, namely the FSB/No Smoking signs, cabin lights and oxygen announcement.
No flightdeck indication would be recieved, except the fact that the announcement is so loud that you could feel it through the flightdeck floor! Jamming the announcement with the PA was the only way to shut it up until the circuit breaker could be pulled!
The initial fix was not to use the therapeutic oxygen system, but to administer bottle oxygen when it was required. Mr. Boeing and Qantas ETOMS later came up with a solution whereby if a passenger used therapeutic oxygen an additional mask would be plugged in at the CSM's station. When the passenger no longer required oxygen the flightdeck switch would be turned off and the mask left at the CSM's station to bleed any residual pressure.
It was certainly not a pleasant thing during the night over Afganistan!
Zkpilot From New Zealand, joined Mar 2006, 4739 posts, RR: 10 Reply 8, posted (6 years 5 months 1 week 1 day 7 hours ago) and read 2122 times:
Quoting Camohe (Thread starter): Is it true that disconnecting someone's supplementary oxygen can cause this?
yes it can. The system is supposed to be bleed for several minutes (with a bleed valve non- ER 747s) ER 747s don't have this problem.
Quoting AJ (Reply 6): Sorry to contradict you guys but we did have a spate of problems with the therapeutic oxygen system on our 747-400s. If a passenger was using the system and simply unplugged from the receptacle in the PSU the back pressure would cause a triggering of the passenger oxygen system ancillary functions, namely the FSB/No Smoking signs, cabin lights and oxygen announcement.
No flightdeck indication would be recieved, except the fact that the announcement is so loud that you could feel it through the flightdeck floor! Jamming the announcement with the PA was the only way to shut it up until the circuit breaker could be pulled!
The initial fix was not to use the therapeutic oxygen system, but to administer bottle oxygen when it was required. Mr. Boeing and Qantas ETOMS later came up with a solution whereby if a passenger used therapeutic oxygen an additional mask would be plugged in at the CSM's station. When the passenger no longer required oxygen the flightdeck switch would be turned off and the mask left at the CSM's station to bleed any residual pressure.
correct. Passengers are told to not disconnect the tube from the system and the FA's will do it. The capt is informed when the sup O2 system is no longer needed.
Quoting Camohe (Thread starter): Just wondering what may have happened and how many radars there are on a 744? Thanks.
The actuator on the radar (thing that aims it) was probably faulty and thus making that noise... kinda like a broken electric window acutator.
TristarSteve From Sweden, joined Nov 2005, 3693 posts, RR: 34 Reply 9, posted (6 years 5 months 1 week 1 day 7 hours ago) and read 2120 times:
Quoting Airfoilsguy (Reply 7): Quoting PhilSquares (Reply 4):
but generally it's one system east bound, the other west bound
Just curious, but why is that?? Is there a potability with opposing aircrafts systems interfering with each other?
No. Most systems that have two systems, but only use one at a time automatically change over each flight, or each engine start. But the radar doesn't. It is selected by the crew. So they use a different system on each flight just to make sure that it is working. Another I can think of is engine igntion wher you select A for one flight and B for the next.
PhilSquares From , joined Dec 1969, posts, RR: Reply 11, posted (6 years 5 months 1 week 1 day 5 hours ago) and read 2097 times:
Quoting AJ (Reply 6): Sorry to contradict you guys but we did have a spate of problems with the therapeutic oxygen system on our 747-400s. If a passenger was using the system and simply unplugged from the receptacle in the PSU the back pressure would cause a triggering of the passenger oxygen system ancillary functions, namely the FSB/No Smoking signs, cabin lights and oxygen announcement.
Quoting PhilSquares (Reply 4): 1) As mentioned, it was just a faulty sensor in the cabin pressure system that triggered the automatic announcement.
Quoting Airfoilsguy (Reply 7): Just curious, but why is that?? Is there a potability with opposing aircrafts systems interfering with each other?
That way both systems are exercised...
Quoting AJ (Reply 10): We swap pressurisation controller, ignition selector, weather radar and transponder on alternate sectors.
I don't know how you can do that with the pressurization controller, but the other systems I will agree with. The pressurization is in auto unless you run it in manual as part of your SOP.
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