Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 8:03 am

Hi guys.

On the side of the engine cowling of the Avroliner 146-RJ85 in the photo below you can see a small square placard located below a small round hole (view it large!) that reads ......

EXTINGUISHER
RELIEF
INDICATOR


View Large View Medium
Click here for bigger photo!

Photo © Dion Fuchs



I suspect this feature/hole has something to do with the engine's fire bottles.

My questions are....... What is being indicated?

Is it that the fire extinguisher is fully charged?
Is it that the extinguisher has been used and thus needs servicing?
Is this object a pre flight "walk around" check for the pilots or strickly used by maintenance personnel?

What does this round object/hole do? Does it change colour? Does an object stick out of it when it's indicating?

Finally, do other jet airliner's engine's have these Extinguisher Indicators on the outside of their cowlings?

Thanks,

Chris  Smile

"Just a minute while I re-invent myself"
 
avt007
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 8:20 am

Pretty much every aircraft will have these, though the location varies. Some are on the fuselage, some on the cowling. There are nromally two for each fire bottle. This picute only shows one, but the idea is that when the bottle is discharged, some of the pressure is sent down a second line to the indicator, which is a coloured metal disc. At the end of the line is a springloaded piston wi tha pin on the end of it. The pressure moves the piston, and the pin pushes out the disc, which is just clipped in place. The disc falss out, indicating a discharge. It is a quick thing to glance at and see if the bottle has been blown. Whether the pilots look at it is a matter for the operators SOP. When there are two indicators, the red one means the bottle blew because the internal pressure rose too high, and was vented overboard before the bottle exploded. The yellow one is for an intentional discharge by the crew.
 
Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 8:36 am

Hello Avt007.

Wow, that was a quick reply and very much appreciated.  Big thumbs up

Thank You, sir for the detailed info on what that object is for and how it works. It's pretty neat to me to learn about the smaller less obvious gadgets that can be found on an airliner's body and engines.

Take Care,

Chris  Smile
"Just a minute while I re-invent myself"
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 9:01 am

The yellow one is for an intentional discharge by the crew.

I've never heard of that before. I would have thought the Tech Log entry after an intentional discharge would have been enough.
 
avt007
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 10:05 am

Perhaps "intentional" is a bad word. The yellow disc is only blown out if the bottle is discharged by the squib, through the cockpit switch. More than one bottle has been blown unintentionally.  Smile
Spaceman- you're welcome! I enjoy showing off my knowledge as much as the next guy!  Big thumbs up
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Fri Dec 19, 2003 6:38 pm

What a/c have yellow disc's?

If a squib blew through a faulty c/pit switch a squib test would ident the problem and the bottle LP Lt's in the cockpit would be illuminated in my experience.
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Sat Dec 20, 2003 8:42 pm

On the RJ and, I believe, the 146 because in many ways they're identical, the green disc blows out if there is a thermal discharge of the fire bottle, i.e. its an over-pressure relief system to vent the extinguisher if for some reason it gets too hot (and therefore its internal pressure gets dangerous).

There are two extinguisher bottles per engine, located in the front of the cowling. If the green disc is blown out, the inside of the "bowl" shaped end of the pipe is revealed, which is red. One each side of each pod. On the preflight, a simple task to check each of the eight green discs.

Similarly, the aircraft has an oxygen bottle discharge disc on the lower right side just forward of the baggage hold, with a white disc. If that blows, according to the manual, streamers are deployed, to attract attention. Never seen it, not even a picture, so don't know how long the streamers are or what colour.

Regards - Musang
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Jet Engine "Extinguisher Relief Indicator"?

Sat Dec 20, 2003 11:31 pm

The 727 has the yellow disc just below #3 engine pylon. Works as AVT described.
You're only as good as your last departure.
 
DC-10Tech
Posts: 291
Joined: Fri Jun 15, 2001 6:40 pm

RE: Jet Engine "Extinguisher Relief Indicator"?

Sat Dec 20, 2003 11:47 pm

Real airplanes have a light in the cockpit that tells you the bottle is empty.  Wink/being sarcastic
Forums.AMTCentral.com
 
VC-10
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Joined: Tue Oct 26, 1999 11:34 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Sun Dec 21, 2003 12:17 am

The 727 has the yellow disc

Funny you should say that because I was thinking about it after I posed the question and thought I could remember yellow disc's on 707 # 2 & 3 sailboat fairings. As it has been 22 years since I last worked on one I couldn't remember. So if the 72 has them the 70 must have had them.

Real airplanes have a light in the cockpit that tells you the bottle is empty. - Couldn't agree more  Smile
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Sun Dec 21, 2003 12:29 am

Classic 737 APUs have 2 disks on the right side of the tail area to indicate either a normal discharge (yellow), or a thermal discharge (red). Either way, there is an APU Bottle discharge light in the flightdeck. Missing indicators indicate the above mentioned conditions.
 
avt007
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Sun Dec 21, 2003 7:04 am

Lights are good too, and most planes I`ve worked have them, but don`t think thats foolproof too. Always have a backup! Discs don`t need power, they can`t burn out like lamps, they are basic and fairly foolproof, yet I have seen the odd disc fall out for no reason, except maybe they weren`t installed properly.
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Jet Engine "Extinguisher Relief Indicator"?

Sun Dec 21, 2003 9:44 am

>>>Real airplanes have a light in the cockpit that tells you the bottle is empty.<<<

The 727 has those as well.

You're only as good as your last departure.
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Sun Dec 21, 2003 3:24 pm

The 747 Classic with PW Jt9D-7Q as well, two on each pylon, one for each bottle... and one for the APU bottle on the tail

Jan
Je Suis Charlie et je suis Ahmet aussi
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

RE: Jet Engine "Extinguisher Relief Indicator"?

Mon Dec 22, 2003 12:01 am

Just so it doesn't feel left out - the 146/RJ series have lights for all 9 bottles in the f/deck!

Regards - Musang
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: Jet Engine "Extinguisher Relief Indicator"?

Mon Dec 22, 2003 1:01 am

LOL I just had a practical on this yesterday. I had to inspect the fire supression system on our T-39A. Bottle pressures, lines, and disks. Disks were missing and the bottles were low. Gee go figure...at a school and all.... Big grin

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