Broward County accident...
On the 412 pulling the t handles shuts the fuel valve and energises the fire suppression system.
The procedure requires closing the throttle first, I used to think why? It’s slower, there is more likelihood of selecting the wrong engine and the throttles can be awkward, why not just pull the T handle?
Turns out it relates to the particle separator, it will suck all of your suppressant out of the engine bay. When you shut the throttle it closes the system, the time it takes to continue the SOP after closing the throttle is enough to close the particle separator door.
You could of course pull the T handle (which also closes the particle separator) and wait 10seconds which will achieve the same thing but evidently Bell has decided Pilots who’s aircraft are on fire might not be the best at accurately guessing time and might waste their first fire bottle
The procedure requires closing the throttle first, I used to think why? It’s slower, there is more likelihood of selecting the wrong engine and the throttles can be awkward, why not just pull the T handle?
Turns out it relates to the particle separator, it will suck all of your suppressant out of the engine bay. When you shut the throttle it closes the system, the time it takes to continue the SOP after closing the throttle is enough to close the particle separator door.
You could of course pull the T handle (which also closes the particle separator) and wait 10seconds which will achieve the same thing but evidently Bell has decided Pilots who’s aircraft are on fire might not be the best at accurately guessing time and might waste their first fire bottle
The actual activation of the FIRE EXT sequence does not have any further pilot controlled input.
If you have a FIRE and you push the button (which only closes the firewall fuel valve) and the sequence continues with N1 < 50% and the FIRE warning is present (pre SN 955 pre SB EC135-26-006) the bottle will discharge which is the first action on the list and then you continue on with caging the engine.
Kind of pointless thinking the fire bottle has another shot in it? Most only have single shot and the 2 shot system is another story altogether and rare on the 135 yet stolen from the BK117-C2 and up.
The logic within the system was changed after SN955 and after incorporation of SB EC135-26-006 where the fuel valve closed feed back was incorporated in the sequence but operationally there was no change.
Prior - the system was ARMED as long as the BAT MSTR was ON and FIRE warning present and N1 < 50% would discharge the bottle. Pushing the button still closed the fuel valve.
Post - the addition that the fuel valve was closed was included in the logic.
Reason being that there were a few procedures i.e. a test of the TOT probes with a heat gun up the tail pipe which if you were not careful where you pointed the heat gun - guess what!
"Normally" on maintenance you would not have the FIRE pb pressed.
[QUOTE=DOUBLE BOGEY;11500505]
But the contributor to this thread who has flown the accident aircraft is pretty confident that there was no fire bottle! These aircraft apparently had the warning and push button, but there was no extinguisher. If you don't believe me, take it from him (#39):
"Pretty sure that 135 had no fire bottles installed. I've flown 4 or 5 airframes and all of them had no bottles. Never liked the 135 because of this. They all had the fire PB's but alert/shutoff only."
Based on this, all the talk about fire bottles and operation thereof may be a red herring. Time will tell...
Originally Posted by [email protected]
I don't think anyone has an issue with him returning to the field with what ostensibly looks like an engine failure (albeit an explosive one).
It seems that he didn't shut the engine down - just set it to idle - and then subsequently noticed the fire and banged off the bottle. Although it seems the idle N1 would be too high to allow the bottle to discharge.
Elements of the tail boom/TRDS could have been damaged by the engine trashing itself and it might have failed anyway but why didn't he shut the engine down completely?
If he had put it to idle, checked the indications (he said he did this) and then completed emergency shutdown - we probably wouldn't be discussing this as the fire would hopefully have gone out and he would have made a safe OEI landing
crab, I can put this to bed early. Idle provides around 70% N1. Pressing the Emergency fir burrow on the CwP shuts down the engine by closing the fuel valve. After that, IF the fire warning is active, (the pilot states Yes) then the fire bottle should discharge when N1 drops below 50%.
It seems that he didn't shut the engine down - just set it to idle - and then subsequently noticed the fire and banged off the bottle. Although it seems the idle N1 would be too high to allow the bottle to discharge.
Elements of the tail boom/TRDS could have been damaged by the engine trashing itself and it might have failed anyway but why didn't he shut the engine down completely?
If he had put it to idle, checked the indications (he said he did this) and then completed emergency shutdown - we probably wouldn't be discussing this as the fire would hopefully have gone out and he would have made a safe OEI landing
crab, I can put this to bed early. Idle provides around 70% N1. Pressing the Emergency fir burrow on the CwP shuts down the engine by closing the fuel valve. After that, IF the fire warning is active, (the pilot states Yes) then the fire bottle should discharge when N1 drops below 50%.
"Pretty sure that 135 had no fire bottles installed. I've flown 4 or 5 airframes and all of them had no bottles. Never liked the 135 because of this. They all had the fire PB's but alert/shutoff only."
Based on this, all the talk about fire bottles and operation thereof may be a red herring. Time will tell...
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Based on this, all the talk about fire bottles and operation thereof may be a red herring. Time will tell...
The discussion does raise questions that if it is found to be true the aircraft did not have fire bottle(s) then their absence would have a direct impact upon what happened and beg questions as to why the decision not to have them occurred and how that absence was handled during training over the many years the aircraft has been in operation.
Hopefully the Investigators shall sort all of that out during their investigation.
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If there was no fire bottle then even more reason to secure the engine quickly.
Originally Posted by [email protected]
If there was no fire bottle then even more reason to secure the engine quickly.
He did! He pushed the button installed specifically for that purpose. Now it might have been slightly quicker to use the Eng Main switch to secure it, but he would have had to hit the button to cancel the fire bell (correct me if I'm wrong T1 operators? I'm only famliar with the T3H), and he was somewhat busy at the time...
[QUOTE=RVDT;11500710]Curious to see that procedure in the RFM - can you post a copy - wondering why you would be turning the fuel valve back on - which is all that FIRE push button does.
The actual activation of the FIRE EXT sequence does not have any further pilot controlled input.
If you have a FIRE and you push the button (which only closes the firewall fuel valve) and the sequence continues with N1 < 50% and the FIRE warning is present (pre SN 955 pre SB EC135-26-006) the bottle will discharge which is the first action on the list and then you continue on with caging the engine.
Kind of pointless thinking the fire bottle has another shot in it? Most only have single shot and the 2 shot system is another story altogether and rare on the 135 yet stolen from the BK117-C2 and up.
RVDT sorry do not have copy of RFM handy but process is the same for the twins I have flown. To be clear they have all had duel fire bottles/duel activation(and detection) systems so we are probably straying from the thread, however all require resetting of the suppression system after successfully firing one bottle so the other side can be used correctly if there is a fire there. As you alluded to earlier use of the other side suppression will result in OEI -1.
You must have misread my comment as I did not say anything regarding turning the fuel valve back on. edited note perhaps in my earlier comment I was not clear it was generic and not specific to the 135.
The actual activation of the FIRE EXT sequence does not have any further pilot controlled input.
If you have a FIRE and you push the button (which only closes the firewall fuel valve) and the sequence continues with N1 < 50% and the FIRE warning is present (pre SN 955 pre SB EC135-26-006) the bottle will discharge which is the first action on the list and then you continue on with caging the engine.
Kind of pointless thinking the fire bottle has another shot in it? Most only have single shot and the 2 shot system is another story altogether and rare on the 135 yet stolen from the BK117-C2 and up.
RVDT sorry do not have copy of RFM handy but process is the same for the twins I have flown. To be clear they have all had duel fire bottles/duel activation(and detection) systems so we are probably straying from the thread, however all require resetting of the suppression system after successfully firing one bottle so the other side can be used correctly if there is a fire there. As you alluded to earlier use of the other side suppression will result in OEI -1.
You must have misread my comment as I did not say anything regarding turning the fuel valve back on. edited note perhaps in my earlier comment I was not clear it was generic and not specific to the 135.
He did! He pushed the button installed specifically for that purpose.
If you have an explosive failure in a twin and a huge area to make an OEI landing (airport) then select to idle, check you have the correct engine and select off, straight away.
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Actually I think it's all to do with where the fire bottle discharges into. It doesn't discharge into the engine but rather into the engine compartment. The engine compartment is ventilated by means of air being sucked out the back by the eductor exhaust. If you popped a fire bottle into the engine bay with the engine running at any appreciable speed, the gaseous halon would get immediately sucked out the back by the exhaust flow. Waiting until the engine is not making any appreciable power means the Halon lingers and has a chance to extinguish the fire. What's going on inside the engine is not pertinent as the Halon isn't inside the engine but as you say the delay also means the fuel is less likely to be flowing.
It can be unexpected reasons. On the 412 pulling the t handles shuts the fuel valve and energises the fire suppression system.
The procedure requires closing the throttle first, I used to think why? It’s slower, there is more likelihood of selecting the wrong engine and the throttles can be awkward, why not just pull the T handle?
Turns out it relates to the particle separator, it will suck all of your suppressant out of the engine bay. When you shut the throttle it closes the system, the time it takes to continue the SOP after closing the throttle is enough to close the particle separator door.
You could of course pull the T handle (which also closes the particle separator) and wait 10seconds which will achieve the same thing but evidently Bell has decided Pilots who’s aircraft are on fire might not be the best at accurately guessing time and might waste their first fire bottle.
The procedure requires closing the throttle first, I used to think why? It’s slower, there is more likelihood of selecting the wrong engine and the throttles can be awkward, why not just pull the T handle?
Turns out it relates to the particle separator, it will suck all of your suppressant out of the engine bay. When you shut the throttle it closes the system, the time it takes to continue the SOP after closing the throttle is enough to close the particle separator door.
You could of course pull the T handle (which also closes the particle separator) and wait 10seconds which will achieve the same thing but evidently Bell has decided Pilots who’s aircraft are on fire might not be the best at accurately guessing time and might waste their first fire bottle.
