Your Experience: Engine fire

[the coyote]

Had an engine fire in flight? Was wondering what indications you got, how you confirmed it, if you smelt it in the cabin, what caused it, what you did etc etc. With the benefit of hindsight, would you do anything differently if it happened to you again?

[SASless]

Never had one.....know no one that has.....know one guy who claims to know a guy that had one....following a catastrophic engine failure with a PT-6 in a Bell 212.

My belief is the fear of engine fires is way overblown.....or am I all wet?

[Nick Lappos]

I have had one, with no indications except the light, caused by a lose fuel line. The vaporized fuel was sucked out the exhaust (natural ejector action routinely cools the engine compartment) and ignited by the exhaust.

They are rare, due to the way the good fittings on lines stay tight and lock easily.

In a FAR/JAR Part 29 bird (airline transport), the fire zone rules are awesome. The zone must allow a 2000 F fire for 15 minutes without compromising the safety of the aircraft, basically making the fire zone similar to the flame pit of an oil burner furnace (we use an oil burner to make the 2000 F in the tests.) That is why the zone on a 76 is all shielded with steel and Ti plates and liners, and the deck is structurally isolated from the deck below.

Part 23 birds (normal catagory) do not have this requirement, and so are much more sussceptable to fire damage.

[[email protected]]

A senior QHI had one at Middle Wallop in a Lynx a few years ago, caused by a tiny hole at the 90 degree bend of a rigid fuel line on top of the starboard engine. He was on an instructional sortie with a basic student on finals to a field at night on goggles! The No2 fire warning illuminated and the student looked up to see a glow coming from behind his head - as the QHI landed very expeditiously, the No 1 fire warning came on as well! The fireball was sucked up and out by the eductor action, crossed over the firewall and set off the firewire on the good engine. Double engine fire indications in the dark in the middle of nowhere - no thanks!
Fortunately they landed safely and shut down very quickly - an engineering inspection showed that the aluminium trans decking had started to melt, trashing the elctrical bay underneath and severely threatening the integrity of the tail rotor driveshaft.
The hole in the fuel line had apparently been caused by a knackered generator bearing settting up a sympathetic vibration in the fuel line which wasn't of a very good design anyway.

[handyandyuk]

I had an engine bay fire during my first lesson in an R22. A runaway clutch overstretched the drivebelts snapping one which then broke an oil line. The resulting oil spraying over the engine burst into flames. Bit disconcerting.
My instructor had full control the whole time, we were returning due to the clutch problem. The only indication of fire was the reflection from the concrete as we came to a hover, then the reduced airflow allowed flames to become visible around the exterior of the cockpit.
We landed somewhat rapidly and as my instructor shut down I put the fire out with the onboard extinguisher, prior to the AFS arriving and making the world all white and foamy.
The R22 in question was repaired and I've flown it many times since.

[EESDL]

Only had the one and was fortunate enough to be in a Wessex so you could look down on it........hang on!!!
Dodgy FCU apparently.

[Nick Lappos]

Crab posted, "an engineering inspection showed that the aluminium trans decking had started to melt, trashing the elctrical bay underneath and severely threatening the integrity of the tail rotor driveshaft."

That aircraft met the typical military standards for engine compartment fire. This type of structural damage would take a very long time in a civil airline transport machine, like the S-76, 61, the Super Puma or the S-92. Military requirements are also more lax about isolation of the fire zone, where all sources of flammable fluids must be positively controlled by a shut-off valve (located outside of the fire zone), even engine oil tanks. This keeps the amount of fluid in check, and reduces the time for the fire to burn itself out.

[MBJ]

Interesting Thread..I agree with SASless that the incidence of engine fires seems vanishingly small - probably because the designers are so conscious of the general depression it brings on if you have one!

I think there is a real concern with the integrity of warning systems for engine fires. Spurious warnings abound in certain types if you leave them out in the rain...BUT I've always been taught to regard any such warning as real and do something about it quick. Confirmation of a possible fire can be hard to achieve without landing which isn't much good if you are 100 miles out to sea.

Are offshore operators allowed to divert to rigs in the event? I wouldn't have thought so.

When I was a baby pilot I heard a tale of a pilot of a Wessex 1 (which had a history of spurious warnings) calling Culdrose, "Spurious Fire warning, returning to base" pause 2, 3.. and then the aircraft blew up.

[Nick Lappos]

I, too, agree with Sasless about the probability of engine fire, but the vast consequences make it important to keep the tight design requirements, I think.

[Lu Zuckerman]

I just finished performing an FMECA on a fire detection system and the manufacturers stated rate of failure (false indication) is.06 10 6 flight hours.

:cool:

[Tail Bloater]

I had 'nearly a fire'. It was in a Bell 47 (Sioux) at Middle Wallop during training sortie that I was informed by another airbourne Sioux pilot that there was smoke emitting from my craft. I had no instrument indications and neither i or my student could see any signs of the problem during our rapid descent to the ground. Once on the ground we made a quick inspection of the engine area, armed with the fire extinguisher and found that an oil pipe was leaking oil onto the exhaust. The engine closed down and exhaust cooled and no fire, but lots of smoke. Simple types are poorly equiped with warning systems.

The comment about water in the fire warning system of the AS355. This was a regular problem that was almost predictable and the fire warning would activate after the machine had been out in the rain for some time. Whatever I thought I always accepted that there was a fire and carried out the drills that are given in the flight manual when in flight and on the ground a quick look normally resolved the problem and a few minutes of warm engine air normally dryed out the sensor/wiring. But never had a real fire.

[tecpilot]

I had an engine fire during startup on a AS 350 B due to a broken fuel injection line. The helicopter, an old workhorse with much more than 10000 hours. Engine was hot, only a 3-5 minutes stop on ground during intensive sling ops. Me in cockpit, never had an indication, no lights, no noise. I goes through the startup procedures normally, but suddenly the ground crew became nervous and jumped and waved me to cut the engine. At first they saw a really (their remembrance) big, big white steam cloud of vaporous fuel and i was wondering why the engine is so tired and rounds up slowly. I closed the fuel valve and i believe some seconds later or in the same moment (i never saw it) the cloud ingnited on the hot engine. Grund crew extinguished the fire immediately within seconds and without problems. Surprisingly there was nearly no damage due to the quick reaction of the ground personel. Since that story i become nervous, feeling unhappy and skidding on my seat if an engine is so tired and slower on startup as normally.

[ShyTorque]

Thankfully never had a real fire but a few spurious warnings on a number of different types, including one during a rotors running refuel.

Here's something that might be of interest to those flying Squirrel aircraft (might only be relevant to twins as I haven't flown the single engined ones). An interesting incident report was published in UK a couple of years ago but I feel it wasn't given enough emphasis at the time, so some pilots might be unaware of it.

Following an airborne FIRE warning light, a (UK Police) pilot carried out the appropriate drills, i.e. shut down the engine and fired off a bottle into the suspect engine. The FIRE warning remained lit so the second bottle was also fired into it. The light still remained on and then smoke appeared inside the cabin. The aircraft was understandably put down short of the airfield they were diverting to...scary stuff, especially as I believe it was dark at the time.

BUT it was a spurious fire warning! Worryingly, the smoke was actually caused by an overheated fire extinguisher system control circuit board inside the centre console. The smoke apparently occurred because the advice in the FM to "unlatch" the fire extinguisher buttons after firing the bottles hadn't been followed (in the heat of the moment?).

The AS-355 engine bay fire extinguisher buttons are of the "latching" (press ON / press OFF) type, in other words pressing them once leaves the button connected electrically, pressing it a second time unlatches it.

The fire bottles are fired by a "squib". This is actuated electrically on pressing the FIRE button, by blowing a built-in filament. The filament is supposed to burn through on actuation. However, sometimes it doesn't (as in this case) and the firing circuit stays intact and live connected unless the button is unlatched. The control circuit board isn't able to withstand a continuous current and so it may overheat, giving smoke and fumes in the cabin.

The UK CAA asked the manufacturers (now Eurocopter) to modify the system to prevent a recurrence. As far as I recall, they declined the request and there has not been a mandate so to do on UK registered aircaft. It seems to me that all that would be required to modify the aircraft is to fit a different type of firing switch, non-latching and spring loaded so that it returns to "OFF" when released.

Any Squirrel pilots NOT heard about this gotcha? I would be interested to know how effective the dissemination of the information was, as I've moved on to a different aircraft now. I must admit, that at the time I was flying the same type but I was unaware of the significance of that FM advice until then and it certainly had not been pointed out to me on my type training.

Be careful out there!

[the coyote]

Thanks to all for your replies.

I fly the S76 and in our checklist, if you get a fire light/tone, the first thing is to confirm the fire. Once you've done that then the obvious: establish OEI flight, pull the fire T handle to shut it down and fire off a bottle etc.

Most if not all experienced pilots I have spoken to have said in this situation they would do that, even if they couldn't confirm the fire, ie act on the warning light alone.

From what I have heard, most warnings have also been false indications. But obviously all warnings must be treated as the real thing.

I guess the grey area I am getting at is at what point do you think you must CONFIRM the fire before shutting the engine down? For example, your 50-100nm offshore, what would you do if you did that, fired off both bottles and the fire warning remained?

[tecpilot]

Have never flown a S-76 but some other twins since 18 years.
My advice, if you are unable to fly 50-100nm OEI in a twin, especially offshore, at night or any other hostile conditions, it's better to use a single, it's much cheaper! ;)

There are some other possible causes to fly OEI, not only the engine fire. If you, personally as the pilot and the a/c, are able to fly safe under OEI condition, don't hesitate to cut the engine.

It's foolish to try to "interprete" the warning lights or the instruments. Have flown a MD 500 with permanent eng-chips light. Never chips on the chip detector. At last, no one including the engineers, believed on real chips and they were right on the moment! "Screw out the bulb for the next hours and have a look at the other engine instruments" nice advice isn't it?, "At home we fix the problem" 5 flight hours later i experienced an engine failure on the ship, with very much chips on the detectors. Fortunately on ground, life-long thanks and some beers free to my ground crew, they refused the next sling load, against my certain and stormy order, i was so stupid!!! because they could hear!!! the engine grinding and screaming. With ear protection and helmet i couldn't hear the noise and all instruments and lights were "green". With one exception the eng-chips light on, with an real electrical problem (short circuit) that makes the system unable to detect chips. Crazy story or?

If you have a possible false fire warning and you would decide to ignore it, may be you have some minutes later a real fire? In which situations you will trust the warning lights? Stay on the flight manual and refer on the chapter "Emergencies" - it's my advice.

And for the young guys: if you ignore a warning light or indication, your boss and the insurance takes your TV-Screen, your car..., ..., ... and you can feel fired, because of the resulting damage. At first it was only a chip or a to low oil pressure and some times later it was a new engine or MR gearbox!

[Shawn Coyle]

Consider that the Polish W-3 (and as far as I know all Russian machiens) has fire detection systems that are pretty sophisticated. They have sensors for rate of temperature change, absolute temperature and airflow (the engine compartment is pretty well sealed).
Lots of logic for different states, but essentially, they all have to agree (rate of temp change is greater than x/sec, absolute temp is greater than y, airflow more than z meters/sec) - and when they do, it says - you have a fire, and automatically discharges the fire bottle into the engine compartment.
Several million hours and years of experience has shown they never have false indications and it has never failed to detect a fire.
And then we tell them about our wire within a wire systems....

[donut king]

I've had a false fire light/ tone in the '76.

Short final....100 ft above the pad....basically at cdp.Finished the approach, minimum hover time landed, shutdown.

Luckily, at idle the indication extinguished. Faulty sensor!

Taught me to never rush the handling of an emergency( given my cat like ninja skills!!!!) but rather, take it slow and methodical.

[tecpilot]

@Shawn Coyle

I know russian helicopters well, especially Mi-2 and Mi-8.
And you are rightly, the fire warning, protection and extinguish system is other and on some parts much better than western systems.The main problem i experienced personally one time and some times by other guys is the sensitivity of the russian system. On the first view the system seems to be perfect. Very good sensors, oh yes, rate of temp change is greater than x/sec, absolute temp is greater than y, airflow more than z meters/sec, 2 or 3 bottles, extinguishing in various compartments including gearbox section, not only the engines and fully automatic release of the first bottle in case of fire detection!
And that's the problem. Current variations, peaks or some other electrical problems, hot air from outside and you have lost the engine. Mostly on ground within the startup and pre-takeoff procedures, the fire system is "hot", refering to checklist before engine start, and the susceptibility is high. In flight it seems the system works constantly or better. On older ships, the fire-bottles are filled with foam and that makes unhappy if you have to clean the whole compartment :( All electrical problems counted as finger trouble, some times only a forgotten switch and the problem was under the (pilot)helmet. It's never possible to built a pilot safe system!
And the weight of their systems and parts it's really russian style. Much more parts and really strong built. Happy times changing to fly western and russian twins! From Mi-2 to Bk 117, nearly the same weight!, but there are some small differencies...