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HAWK21M
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Flashing Red Light At Ends Of Cabin On A320

Fri Jun 29, 2007 9:56 pm

Last night between Mx work on our Freighters.I passed by an IT A320 parked at night & noticed that there was a Red flashing light inside the closed Aircraft at either end of the cabin,noticable from outside through all four Entry doors Window.

I informed IT Mx.But since I've not worked on the A320.Is anyone aware of what that light could be.Was it a smoke alarm light or Blinking light on the rechargable flashlights.

I had to get back to work so could not investigate further.

regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Tristarsteve
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RE: Flashing Red Light At Ends Of Cabin On A320

Fri Jun 29, 2007 10:27 pm

It is the cabin pressure warning.
When the aircraft is parked with residual pressure in the cabin, red lights blink inside the doors, visible through the little window to warn you not to open the door.
It is not unusual that they blink when there is no pressure. The cabin crew tell the captain, and he opens his DV window to check, then you open the door.
 
Markhkg
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RE: Flashing Red Light At Ends Of Cabin On A320

Fri Jun 29, 2007 11:23 pm

The light is installed on all A320/A330/A340/A380 family aircraft floor level exits.
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VHXLR8
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RE: Flashing Red Light At Ends Of Cabin On A320

Sat Jun 30, 2007 3:11 pm

The Cabin Pressure indicator lights flash red when the following 3 things have occurred; the engines are shut down, the door is disarmed, and the cabin differential pressure is above 0.0362.

This is a very important indicator device; given that Airbus aircraft don't have plug type doors, opening of a door when cabin pressure is too high will most probably throw the person from the aircraft (and in the case of one poor F/A - can't remember which airline - to their death).
 
Markhkg
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RE: Flashing Red Light At Ends Of Cabin On A320

Sat Jun 30, 2007 4:26 pm

Quoting VHXLR8 (Reply 3):
This is a very important indicator device;

Yeah, but even if the system had been installed the F/A would STILL have been killed! The A300 AA accident (one of at least two Airbus accidents) actually involved an emergency evacuation -- so the doors were still in the "armed" mode. Even if the red cabin pressure light was installed (again, this feature is not installed on A300 doors) the light would not be flashing in this situation because the door was still armed.

I believe this is a serious oversight on Airbus' behalf...
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VHXLR8
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RE: Flashing Red Light At Ends Of Cabin On A320

Sat Jun 30, 2007 5:20 pm

Quoting MarkHKG (Reply 4):
Yeah, but even if the system had been installed the F/A would STILL have been killed! The A300 AA accident (one of at least two Airbus accidents) actually involved an emergency evacuation -- so the doors were still in the "armed" mode. Even if the red cabin pressure light was installed (again, this feature is not installed on A300 doors) the light would not be flashing in this situation because the door was still armed.

As usual I agree with you 110% mate. Unfortunately a lot of 'safey' features on aircraft are only applicable for normal operations (such as opening a door for normal disembarkation of pax), and don;t allow for emergency situations.
Alas, possibly yet another argument for plug type doors perhaps.
 
MD11Engineer
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RE: Flashing Red Light At Ends Of Cabin On A320

Sat Jun 30, 2007 11:19 pm

Actually Airbus entry doors ARE plug type doors. They are being pressed by cabin pressure against their door stops in the frame.
I assume that the Boeing way of making the door smaller than the opening was blocked by patent issues, so that Airbus had to invent another method of operating the door.

In short:
When the door is closed, door stops on the door are inboard of the door stops on the frame. The cabin pressure pushes the door against the stops (like on a Boeing). To open the door a lever mechanism in the door hinge assembly gets actuated by the door handle, lifting the door by about 2 inches, so that now the door side doorstops are above the stops on the frame, thus allowing the door to rotate (guided by a parallelogram mechanism) out of the opening.
During normal flight operations the pressure of the door against the frame door stops is so high that it is impossible to lift the door off it's stops using the lever mechanism.
If the pressure differential is low though, a strong person can lift the door, causing it to pop open.

For emergency operation with the slide armed, there exists a smal nitrogen bottle in the hinge assembly. On opening the door with the slide armed, a striker punctures a diaphragm in the bottle valve assembly and allows high pressure nitrogen to pass into the door damper cylinder (also sited in the hinge assembly, it normally dampens the door movement, e.g. in a strong wind). This forces the door open quite violently and F/A's are supposed to be told to let go of the door handle when the door starts to open in emergency operations.

Jan
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Markhkg
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RE: Flashing Red Light At Ends Of Cabin On A320

Sun Jul 01, 2007 12:54 am

Quoting MD11Engineer (Reply 6):
I assume that the Boeing way of making the door smaller than the opening was blocked by patent issues

I think Airbus wanted to design a better door and they did, in a sense. (Easier to open if the power assist fails than a B747!) It shouldn't be a patent issue since McDonnell Douglas (DC-8, DC-9, MD-80) and Lockheed also used plug type designs. If anything, Boeing copied Airbus' door design with the B-777 series door, which are also push and swing out! I always find it reassuring that all doors on board aircraft today cannot be opened in-flight...there are too many stories of pax (albeit not mentally competent at the time) trying to open the doors in flight and everyone else fearing for their lives.

My understanding is that Boeing doors have a vent gate/flap/hole that opens when the door handle is rotated. This vents out any residual pressure. (If the pressure differential is too high however, the door will not open as it is a plug type design, as noted above.) Airbus doors, on the other hand, do not have this vent feature.

[Edited 2007-06-30 17:57:53]

[Edited 2007-06-30 17:58:41]
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MD11Engineer
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RE: Flashing Red Light At Ends Of Cabin On A320

Sun Jul 01, 2007 2:00 am

Quoting MarkHKG (Reply 7):
My understanding is that Boeing doors have a vent gate/flap/hole that opens when the door handle is rotated. This vents out any residual pressure. (If the pressure differential is too high however, the door will not open as it is a plug type design, as noted above.) Airbus doors, on the other hand, do not have this vent feature.

The traditional Boeing doors (707 until 757) don't have vents. The upper and lower flap are moving inwards (but this is only possible if there is no pressure differential) to reduce the height of the door. The door then moves inwards, rotates on a axis around the hinges at about 1/4 of the door width, making the door narrower than the opening, so that it can be rotated outwards.

The 767 door is first unlocked by a small lever, which also disarms the slide. Then another, bigger, lever pushes the door inwards, away from the stops, into the rails. A spring counterweight mechanism helps when pushing the dor upwards into the ceiling.

Jan
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skoker
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RE: Flashing Red Light At Ends Of Cabin On A320

Mon Jul 02, 2007 7:56 am

Quoting VHXLR8 (Reply 3):

This is a very important indicator device; given that Airbus aircraft don't have plug type doors, opening of a door when cabin pressure is too high will most probably throw the person from the aircraft (and in the case of one poor F/A - can't remember which airline - to their death).

I believe that was AA in MIA:

www.ntsb.gov/recs/letters/2002/A02_20_23.pdf

Quote:

Background

On November 20, 2000, about 1222 eastern standard time, a flight attendant/purser was
killed during an emergency evacuation of American Airlines flight 1291, an Airbus
Industrie A300B4-605R (A300), N14056, at Miami International Airport (MIA), Miami, Florida.
The airplane was pressurized until the flight attendant/purser opened the left front (1L)
emergency exit door; he was then forcibly ejected from the airplane. There were 133 persons on
board. During the emergency evacuation, in addition to the 1 flight attendant/purser who was
killed, 3 passengers sustained serious injuries; 18 passengers and 1 flight service director1
sustained minor injuries; and the 2 pilots, 6 flight attendants, 1 off-duty flight attendant, 1 flight
service director, and the remaining 100 passengers reported no injuries. The airplane sustained
minor damage.2
 
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HAWK21M
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RE: Flashing Red Light At Ends Of Cabin On A320

Mon Jul 02, 2007 10:47 pm

Quoting Tristarsteve (Reply 1):
When the aircraft is parked with residual pressure in the cabin, red lights blink inside the doors, visible through the little window to warn you not to open the door

I wonder what was the reason in the IT A320.
regds
MEL
I may not win often, but I damn well never lose!!! ;)

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