Bristows MGB fire warning

[NorthSeaTiger]

Heard today that a bristow puma had an mgb fire warning on take off ? and had to return to base after 5 mins ?

[Teefor Gage]

Why would it take anybody that long to decided to RTB when the fire warning happened on take-off.
NST - Where did you get the info from - sounds rather distorted to me?!

[Limpopo]

The aircraft had one of the two warning lights come on intermittently after 5 minutes airborne. It was nothing serious and was a fault in the warning system. To be of a serious nature BOTH MGB Fire warnings have to illuminate.

Seems to me Eurocopter provide a crap warning system which requires no immediate actions unless there are two warning lights on (plus probably lots of smoke and fire just to confirm them!).

[TipCap]

Unlikely to be a Bristow AS332L as they are not fitted with MGB Fire warnings

[Helitemp]

I think CAA many years ago had the MGB fire warning on all 332L removed for A/C on the British register.:bored:

[Chopper Jog]

The L2 is the same... we don't have the MGB fire system fitted (removed) due to the weaknesses in the design of the system.

I wonder if the EC225 will have a better system?

[Aser]

MGB fire warning light? that's new to me, what is suposed to be on fire? the oil in the MGB? :confused:

[NorthSeaTiger]

So what was the warning then ? Engine fire perhaps ?

[Fareastdriver]

MGB fire warning is a standard manufacturers fit. You have to tell them that you don't want it. The ones I fly have always had them and they haven't caused any problems. The test is similar to the EFW system but there aren't any big red lights, just the caption. I haven't had them come on over ten years and I wouldn't like to either without any mirrors to see what was going on. :eek: :{ I cannot think of a situation where the MGB fire warning would come on without massive indications from other gearbox or hydraulic warnings that would have led to its landing or ditching beforehand. Two possiblities are a rotor brake fire or a severe engine fire and breakup that has fractured the engine firewall. Despite a comment about their unreliability EH still fit them so they can't be that bad. Maybe the CAA jumped the gun. We have baggage bay fire warnings so why not have one in every enclosed volatile area.

[212man]

Did the MHS AS332L2 that ditched recently have it fitted?

[Super 61]

I believe it was disconnected also, as it was an ex N Sea machine.

[Fareastdriver]

Just a thought. If the Bristow aircraft they were flying was fitted with the MGB fire warnings they would have spent five minutes looking for a non-existant page in the EOPs.

[DECUFAULT]

The MHS L2 aircraft did not have the MGB fire warning fitted, the Bristow 225's have the system fitted as it was part of the certification. I would be looking in the mirrors to see if there was any smoke...! :eek:

[NorthSeaTiger]

So was it an EC225 involved and not a Super Puma ?

[HeliComparator]

Such is the fickleness of National Airworthiness Authorities that in the days when UK CAA had anything to do with aircraft certification, the Super Puma family was forbidden to have MGB fire warning systems fitted. But now with the switch to EASA, now we are forbidden to remove the system:ugh:

But there is a bit of history - when the fire detectors "detect" they open their contacts, creating a resistance in the circuit. Originally the fire detectors (which are just bimetallic switches such as you might find operating the thermostat of your electric fan heater) were open to the environment, and prone to contamination by oil, fumes, soot etc such that spurious warnings were routine. There were probably at least 1000 false warnings for every real one. The CAA decided that, since there was no fire protection (extinguishers) in the transmission area, and the only course of action is to land/ditch, one day there would be a ditching in bad weather and people would drown due to a spurious warning. So they made N Sea operators remove them.

After many years, the manufacturer decided to sheath the detectors in a thin metal envelope, and this resulted in a massive reduction in false warnings - perhaps down to 100 false warnings for every real one (no, probably not that good) and its these same detectors that are still fitted today.

Of course "only the Brits" have a problem with these detectors - well actually others do as well but if you are operating onshore you just land in a field, kick the detector and carry on, no big deal. Even though Norway followed suit by removing them, EASA were hoodwinked into accepting the detectors as part justification for meeting some elements of JAR29 and before we knew it, the crappy old system was mandatory on the 225. Yes there are 2 circuits and yes its pretty unlikely both systems will activate spuriously at the same time, but nevertheless it takes a brave (and foolish) pilot not to rtb following an activation of one of the circuits. I suppose if we can build up a big enough library of sprurious activations we can go to EASA with a case, but that will take many years.

Regarding the unfortunate MHS accident, the problem as I understand it was a dodgy hydraulic system, not the absence of fire detectors. I am sure there are scenarios where the detectors might have helped (though no use if you are over unlandable terrain (primary jungle etc) or IMC over high ground). There are other scenarios where the unreliability of the detectors could cause loss of life for no good reason. I have operated the 332L without the detectors for many years, now I fly with them and I don't feel strongly either way (apart from hoping I never see both systems activated at once!)

HC

[Vertical T/O]

"MGB fire warning light? that's new to me, what is suposed to be on fire? the oil in the MGB? :confused:" Aser


It is suppose to detect a hydraulics fire. The sensors are positioned near hydraulic components and in the oil cooler. It is in the MGB compartment so that is why it is labelled 'MGB FIRE'. There are two sensors at each point and both need to be activated before the crew have to do anything.

[JimL]

ASER,

If you wish to have an understanding of how critical a fire in the gearbox bay can be, read the report of this accident:

http://www.aaib.dft.gov.uk/publications/formal_reports/2_2004_g_bbhm.cfm

Jim

[Aser]

Thanks Vertical and JimL :ok: