90 minutes?

[Guest Moonraker]

I wonder what the reasoning may be behind the "after 90 minutes - push discharge bottle 2" instruction in case of a cargo fire ???(e.g. SYSTEMS, on page: FIRE.30.3)One would assume, if the fire is still burning after 90 minutes, the plane will certainly already have crashed after such a long time.On the other hand: if the fire had been extinguished after discharging bottle 1 already - why discharge bottle 2 90 minutes later?Wouldn

[tcas_climb 45]

It ensures the fire is suppressed and stays suppressed. Kinda like when you're burning garbage for example, you can drown it with water yet deep down under the pile a small flame is slowly burning.Why not use both? Well if you use both you will only get 90 minutes of fire suppression whereas if you one after the other, the first bottle empties in 90 minutes and then you have an additional (someone correct me on this) i think 60 minutes giving a total of 150 minutes suppression.

[Guest Moonraker]

Why not use both? Well if you use both you will only get 90 minutes of fire suppression whereas if you one after the other, the first bottle empties in 90 minutes and then you have an additional (someone correct me on this) i think 60 minutes giving a total of 150 minutes suppression.

Ah, now I understand! I did not know that the first bottle takes 90 minutes to empty! Now everything makes sense. I thought such a bottle would empty in a few minutes!Richard

[downscc 1,327]

Yeah, 90 seconds is a long time if there is fire. The bottles empty quickly, the wait is for cargo fire reignition possibility. See also FIRE 10.10 in the SYS manual.

[Guest Moonraker]

Yeah, 90 seconds is a long time if there is fire. The bottles empty quickly, the wait is for cargo fire reignition possibility. See also FIRE 10.10 in the SYS manual.

Yes, but we are speaking of 90 MINUTES!!!The SYS MANUAL speaks of "approximately 90 minutes AFTER the agent 1 bottle has been discharged"!I

[Guest Moonraker]

Yes, but we are speaking of 90 MINUTES!!!The SYS MANUAL speaks of "approximately 90 minutes AFTER the agent 1 bottle has been discharged"!I

[mfrantz 45]

Nobody here who knows the correct answer? Does bottle one have enough Halon for 90 minutes of fire-fighting OR does the bottle empty within a few minutes and then, AFTER WAITING FOR 90 MINUTES, bottle 2 should be discharged (which would lead to the question: why wait 90 minutes? On the other hand it

[Guest cfgarrod]

Assume you're talking about the lower cargo compartment fire protection system on a pax MD11?I last flew the aircraft in 2002 so maybe things have changed, but it was like this:If smoke or heat is detected the MCS automatically shuts off heating and ventilation.There are 2 bottles one large, the second smaller. They are located in the centre section and can be directed to the affected compartment by selection on the overhead panel. Using the emergency checklist the flashing (FWD or AFT) cargo fire agent p/b is pressed. The 'LOW' light will illuminate. Discharge time is 28 seconds. The compartment is now isolated and filled with agent. After 90 minutes this is replenished by discharging agent 2.After a cargo fire warning the aircraft should in all cases be landed at the nearest emergency aerodrome.After landing keep the cargo doors closed...Chris G

[Guest Moonraker]

The first bottle discharges is a few seconds (when the LOW light illuminates the bottle is empty). As I understand the second bottle discharge after 90 minutes is a precaution measure, in case the fire revives.

O.K. Many thanks for the answer!

[Guest Moonraker]

Assume you're talking about the lower cargo compartment fire protection system on a pax MD11?I last flew the aircraft in 2002 so maybe things have changed, but it was like this:If smoke or heat is detected the MCS automatically shuts off heating and ventilation.There are 2 bottles one large, the second smaller. They are located in the centre section and can be directed to the affected compartment by selection on the overhead panel. Using the emergency checklist the flashing (FWD or AFT) cargo fire agent p/b is pressed. The 'LOW' light will illuminate. Discharge time is 28 seconds. The compartment is now isolated and filled with agent. After 90 minutes this is replenished by discharging agent 2.After a cargo fire warning the aircraft should in all cases be landed at the nearest emergency aerodrome.After landing keep the cargo doors closed...Chris G

Now I begin to understand, many thanks for the answer. As I suspected the discharge time is very short. If I understand you correctly, the compartment is then filled with such a big amount of agent, that it is only neccessary to discharge another bottle after 90 minutes.And yes, obviously a very important rule, to land at the nearest aerodrome in all cases: Swissair 111 didn