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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 https://cimg6.ibsrv.net/gimg/pprune....71838b1b74.png |
Originally Posted by SLFMS
(Post 11500580)
No not 109, perhaps inactive position would have been better choice of words
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]
Originally Posted by [email protected]
(Post 11500100)
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%. "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... |
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. |
If there was no fire bottle then even more reason to secure the engine quickly.
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Originally Posted by [email protected]
(Post 11500849)
If there was no fire bottle then even more reason to secure the engine quickly.
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Originally Posted by TorqueOfTheDevil
(Post 11501018)
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...
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[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. |
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. |
Originally Posted by RVDT
(Post 11500553)
If the engine is still running it is unlikely that you will extinguish the fire. i.e. a leak at the flow divider or nozzle manifold burst.
Hence the logic to try and make it shall we say "idiot" proof. |
Originally Posted by SLFMS
(Post 11500569)
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. |
NTSB Aviation Investigation Final Report - N109BC
In summary, the accident was the result of an inflight fire in the vicinity aft of the helicopter’s No. 1 engine exhaust, near the air conditioner condenser fans, and the origin of the fire was likely the result of the engine overheating. The only plausible explanations the investigation could determine for only the No. 1 engine to overheat were foreign object debris, blockage of the No. 1 engine air inlet, or hot gas or combustible fluid ingestion. Because the wreckage was subjected to a postimpact fire, the source of the overtemperature could not be determined. The National Transportation Safety Board determines the probable cause(s) of this accident to be: An inflight fire outside of the engine firewalls, likely from overheating of the No. 1 engine for undetermined reasons, which resulted in a partial tailboom separation. |
Doesnt feel like we learn a lot from this. The cause of the crash was a fire near the tailboom attachment. Brilliant got that from the YouTube video.
. But why didnt the pilot action the fire drill? Why didn't the engine bay contain the fire? Had the pilot practiced that procedure in the sim? Did the aircraft have the optional (for a T1) protection system? Was the emergency procedure adequate, was the aircraft fitted with a cvr FDR? So many unanswered questions! They seem to have discounted an overspeed after the fuel flow froze which has previously led to several similar events on early EC135. |
Originally Posted by gipsymagpie
(Post 11952944)
... was the aircraft fitted with a cvr FDR?
The accident helicopter was not equipped with, nor was required to be equipped with, a cockpit voice recorder or a flight data recorder. An Appareo Vision 1000 cockpit image recorder was installed onto the accident helicopter in April 2018 in accordance with Airbus service bulletin No. EC135-31-070. However, the Vision 1000 was not found in the wreckage and presumed destroyed in the postcrash fire. |
Originally Posted by BFSGrad
(Post 11952966)
From the Airworthiness Factual Report:
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Originally Posted by gipsymagpie
(Post 11952944)
Why didn't the engine bay contain the fire?
Did the aircraft have the optional (for a T1) protection system? |
Originally Posted by wrench1
(Post 11953187)
It was determined the fire was located outside of the #1 engine bay in the general area of the AC condenser mounting, which was reason no fire light until seconds before tailboom failure.
Yes. An interesting note, the pilot stated he had pushed the FIRE light/button multiple times, yet the switch guard was still safetied in place and the fuel valve was found in the open position. |
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