Popee From Pakistan, joined Feb 2001, 151 posts, RR: 0 Posted (10 years 11 months 1 week 4 days 7 hours ago) and read 2306 times:
On B 4747, instead of measuring the fire bottle pressure, a pr. s/w installed in the line to direct bottle content to engine illuminates the BOTTLE DISCHARGE light in the cockpit.
Is this not a discrepancy ? Discrepancy in a way that in case if any bottle(s) dicharges due to over temperature after walk around check by F/E, no light will lit in the cockpit ? (As discs are used to monitor O/T discharge )
VC-10 From United Kingdom, joined Oct 1999, 3677 posts, RR: 36 Reply 1, posted (10 years 11 months 1 week 4 days 7 hours ago) and read 2295 times:
The Pressure Sw is on the bottle.
The line Press Sw is only in the Cargo Fire Ext Sys to the Fwd Hold. This is because the lines to the Fwd Hold are of a small diameter so if the bottle is discharged the lines will "choke" with agent which will increase the time before a decrease in pressure is felt in the bottle to bring on the Disch light.
The aft hold doesn't have the problem because of the longer pipe run.
VC-10 From United Kingdom, joined Oct 1999, 3677 posts, RR: 36 Reply 3, posted (10 years 11 months 1 week 4 days 3 hours ago) and read 2266 times:
What you say is only applicable to the JT9 installation, all the other engine configuations have press switches on the engine firebottles.
On the JT9 system for an o/press dicharge to occur you require an o/press in the bottle of at least 2400psi at 300Degs F. I would very much doubt that is going to happen in the 30 mins before flight when the FE does his walkround.
B747skipper From , joined Dec 1969, posts, RR: Reply 4, posted (10 years 11 months 1 week 4 days 2 hours ago) and read 2239 times:
Popee - this applies to the JT9 powered airplanes...
Discharge light will be ON only for INTENTIONAL (MANUAL) discharge of the fire bottle for the engine and APU... a thermal discharge would not illuminate the discharge light, but would blow the red disc of the related bottles...
But an exception is for the lower cargo fire protection is as follows... again, manual discharge will illuminate the related discharge light... HOWEVER in case of a THERMAL discharge of bottle number 1... OR... number 2... will ALSO illuminate the.... NUMBER 1 discharge light (even if bottle number 2 had the thermal discharge)... this is a famous oral question for FEs, and probably for ground engineers as well...
I remember in the 707 and the 727, the discharge light was on for a bottle low pressure, after a manual, or thermal discharge... so they changed all that with the 747... dont ask me about the other Boeing planes...
If you care to know about the 747 with CF6 like VC-10 says it may be different, I will see what my books say about these airplanes... I have no info about the RR powered airplanes...
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 38 Reply 5, posted (10 years 11 months 1 week 3 days 18 hours ago) and read 2223 times:
Is this not a discrepancy ? Discrepancy in a way that in case if any bottle(s) dicharges due to over temperature after walk around check by F/E, no light will lit in the cockpit ? (As discs are used to monitor O/T discharge
I never realized this but I think you're correct. Kind of strange that a pressure switch isn't installed directly on the bottle.
A couple of years ago while waiting to pushback a DC10, a momentary brownish haze by the tail caught my attention. Moments later the crew called on the headset informing me of a #2 fire bottle low pressure light.
The bottle thermal discharged due to a bleed leak overheating the bottle.
Popee From Pakistan, joined Feb 2001, 151 posts, RR: 0 Reply 8, posted (10 years 11 months 1 week 2 days 6 hours ago) and read 2153 times:
The 747 has been around for in excess of 30 years now. If the disaster was going to happen, it would have happened by now.
Does it imply that no new accidents can happen in aviation ? All accidents happening now r known to us as they r all repeated one ? An accident not happened till now shows no such accident can take place now ?
VC-10, the answers to all these questions is a big NO. Its not a right judgement that as such past 30 years were safe so its future will also be safe although an anamolly is there.
What would u say, if God forbid, it happens this week ???
Popee From Pakistan, joined Feb 2001, 151 posts, RR: 0 Reply 10, posted (10 years 11 months 1 week 1 day 3 hours ago) and read 2125 times:
VC-10, yes. The case u r talking about is that the crew gets the information about while in the c/p. What i am saying is they r unware that bottles r discharged after the turn around check by F/E, a situation c/p crew is totally unaware of and getting all ok in the c/p.
BTW the fire warning system will still give any fire wx although test may be u/s.Amazing isn't it...