AT3 destroyed by fire just before takeoff Somersby Airfield

[Flea_Nut]

As the pilot was doing a full power runup prior to taking off, the engine cut out ( Rotax 912 ) and then burst into flame. The pilot managed to scrambled to safety, and the aircraft was totally consumed by fire.  The AT3 was the only one in Australia (Kitplane)

It is thought that fuel hose came off.

 

Approximately 4 weeks ago

[facthunter]

Be something like that. Good it happened on the ground if it WAS going to happen. Fire in the air is about the worst thing that can happen. Nev

[onetrack]

How can a fuel hose just "come off"? Surely, you make 101% sure these connections are totally secure, when you're doing checks?

[facthunter]

Murphy's Law.. Nev

[KRviator]

3 hours ago, onetrack said:

How can a fuel hose just "come off"? Surely, you make 101% sure these connections are totally secure, when you're doing checks?

Not always that easy. I can't remove the cowl on the RV without a screwdriver, pliers, 15 minutes and about a dozen profanities. The easy to see result of that is the hoses & pretty much everything under the cowl goes physically unchecked between oil changes.

 

I touch what I can through the inlet & oil door but that isn't much.

 

Quote

Good it happened on the ground if it WAS going to happen. Fire in the air is about the worst thing that can happen. Nev

A seconds later and it would have been particularly nasty. There is SFA chance of a good outcome if you have an early EFATO at Somersby. Truly a lovely little airfield that was beautifully close to home but I always had a good dose of nerves for the first 30 seconds or so till you get enough height to glide clear of the trees. This satellite shows why...

[Old Koreelah]

6 hours ago, onetrack said:

How can a fuel hose just "come off"? Surely, you make 101% sure these connections are totally secure, when you're doing checks?

This discussion is based on second-hand information; perhaps we should wait until the pilot of the aircraft in question makes a contribution.

[facthunter]

No harm in kicking it  around. No one has died.  Nev

[Thruster88]

The report to RAAus. 

 

 STATUS: Under review EXTRACT FROM REPORT SUBMISSION: The pilot completed the preflight and started the engine and proceeded to taxi to backtrack runway 35, the aircraft and engine indications were normal. The engine ran normally at 4000rpm; Ignition check normal, 120 rpm drop Ign1 & Ign2; but roughly at 3000rpm and at idle (1600-1800rpm). The engine was shut down for investigation (ignition 1 & 2 OFF, master switch off). There was no indication of smoke or fire. Then light smoke appeared from forward part (NACA inlets) of engine cowl. The pilot exited aircraft to investigate. The smoke thickened & darkened from within engine cowl. (the pilot return to the cockpit, to pull the fuel shutoff lever to it cut-off). The smoke darkened and began to blister the cowl paint and flames appeared from the nose cowl. Fire services were called and the fire was extinguished.

 

Me, it is possible that the carburetors were flooding and venting fuel overboard.  How this is handled on some aircraft is criminal,  not saying that is the case here. Certified aircraft  have fuel drain tubes for failed components, these exit the bottom of the cowl and have been proven to work over a long time period. How does your aircraft handle carb flooding, inside or outside the cowl?

[pylon500]

I guess it would have been this one...

https://aeropedia.com.au/content/aero-at-3/

[facthunter]

Like I posted very recently. A float equipped carburetter is too risky on an aeroplane. Where they are located below the motor and properly protected, MAYBE.

  Quite frankly the BING  CD is a piece of crap and a lot of people know it. Nev

[ClintonB]

My old charger had a problem with needle valve and float once, because I had modified things fuel was squirting onto hot extractors (from the overflow pipe)with smoke starting. I think luck and a short run stopped a full blown fire starting.

[kgwilson]

Carbs on top of the engine is a disaster waiting to happen even with deflectors to theoretically dispense fuel overflows. At least the Jab Bing is at the bottom behind everything including the exhaust.

Edited April 21, 2021 by kgwilson

[Old Koreelah]

6 hours ago, kgwilson said:

Carbs on top of the engine is a disaster waiting to happen..

My first engine (VW-type) had the carb on top, plus a drain tube to take overflowing fuel away.
When I noticed petrol spilling down onto the hot bits I discovered that a previous owner (one was a LAME) had cut this tube off and never replaced it.

 

[jackc]

I wonder IF it had the red coloured fuel line?  Mako?

[AT3 pilot]

I am the pilot and owner of AT3 19-4226 which was consumed by fire at Somersby 11 Feb 2021, and I am submitting this report to clarify and correct some commentary which has been made about the event.

 

1. the engine run-up was standard for a Rotax 912 i.e. 4000rpm, not 'a full power runup' as suggested on 20 April
2. the engine did not 'cut out' during the 'engine run' - it was shut down after the throttle had been retarded to the idle setting
3. the pilot did not 'manage to scramble to safety...after the engine had burst into flame' - once the engine was shut down, and the pilot noticed smoke observed coming from the engine cowl he vacated the airplane . Fire commenced several minutes later.

Other points: 

 

a  thorough pre-flight inspection, had been conducted....including engine & airframe, all items including  all hoses, wiring, battery, etc secure and in good condition; hydraulic fluid, coolant & oil levels all at correct levels. 

 

All maintenance requirements were met and the airplane was in excellent condition.

 

the airplane had 48 litres fuel ( 98 octane car fuel ) at start-up.

 

The engine started normally, and all indications ( oil temp, oil pressure, coolant temperature etc ) were normal.

 

10 minutes after  start the oil and water temperatures were warm enough for an engine run-up....

 

 the ignition check: engine smooth at 4000rpm, ignition drop 125rpm each ignition system ( 300 allowed ).

 

the idle check: Upon reducing throttle to achieve 3000rpm the engine ran slightly rough...reducing further to 2500 rpm then 1800rpm the engine ran very rough. Back to 2500rpm, still rough so I closed throttle, the engine on verge of cutting out so I switched off both ignitions, and switched off electric master switch. Engine stopped.

 

I thought, momentarily, that there may be a fuel supply problem, hence rough operation. 

 

I then looked ahead at the stationary propeller and noticed that light, thin smoke was emanating from front of engine cowl.

 

I opened the canopy, released my harness, got out of plane and hurried to the engine cowl, noting that smoke only coming from the front of the engine ( note: airplane parked into wind, strength 5-8 knots ).

 

looking inside the engine cowl, from the rear inspection hatch, there was no evidence of smoke behind the engine, or any flames. Looking at the nose again I cd see that the smoke was thickening and darkening in colour and rising from the air inlets mounted on top of the engine cowl.

 

( I did not have a fire extinguisher in the airplane; had I had one I would have fired it into the engine cowl at this time ).

 

I rushed back to the cockpit, and pulled the fuel shut-off valve lever ( the valve is below the fuel tank, which is ahead of the instrument panel, but behind the firewall and the engine bay ). 

 

However, once the engine had ceased rotating there cd be no fuel pumped by the engine-driven pump, and the electric pump had been switched off, prior to the engine run-up. So there had been no pressure feeding of fuel into the fuel lines once the engine had been shut down.

 

I then walked back to the front of the airplane, noted the smoke becoming more dense, then in an instant, flames erupted from the nose cowl inlet.

 

 

The flames rapidly expanded, consuming the composite engine cowl ( top & bottom halves ), the coaming above the instrument panel, the fuel tank aft of the firewall, the perspex canopy and then the combustible materials in the cockpit.

 

 

After 10-15 minutes the metal keel of the fuselage melted and the nose fell forward due the weight of the engine; later the centre-section and mainwheel attachments melted and the airplane fell onto its belly.

 

The fire burnt for 30 minutes ( the Fire services arriving 20 minutes after they were called, reasonable considering then 25 kms they had to travel ).

 

After all combustible materials ( fabric, fibreglass, perspex, carbon-fibre, 48 litres 98 octane fuel ) were consumed, the fire extinguished itself. What remained was a pile of ash with metal wing-tips and the metal tail sticking out !

The engine was charred and rendered unusable.

The firewall ( aft of engine bay, ahead of the fuel tank ) was scorched but intact

The battery was not Lithium-Ion, and had been replaced approximately 12 months before the accident. It exploded during the fire, as did two of the three tyres.

 

Possible causes of the fire ?

 

An electrical problem ? - such as ignition short-circuit / spark / failure ? Would have had to be instantaneous as engine only ran roughly for less than 30 seconds after engine run-up and before shutdown ( engine guage indications remained normal throughout ). Fire fuelled by airplane fuel , oil,  combustible materials ? Probably the engine ran rough due to fuel disruption..... possibly a fuel hose rupture, a fuel hose coming loose or a carburettor flooding due some internal jamming ( note: all hoses within 5-year life, were well-secured and were in excellent condition ).

 

Note that each carburettor had a drip tray, with a drain tube secured on the nose wheel leg at the bottom of the engine cowl.

 

Unfortunetly, no rubber item, including hoses, survived the 30 minute fire, so they cannot be inspected to test hypotheses. However, the left hand carburettor was mostly intact wheras the right hand carburettor was partially melted. 

 

 

 

 

 

So, what did I learn from this accident ?

 

1. Airplanes burn very quickly ( due availability of large quantities of fuel, and possible 'supercharging' by forced airflow, if airborne ).
2. Airplane fires are rare, so existing designs and mechanical practices are obviously successful in ensuring safety. 
3. Install a fire extinguisher accessable in the cockpit. It is not required by regulation and weighs several kilograms, but its use could extinguish a fire or at least, forestall its spreading.
4. Have all fuel & oil hoses sheathed in fire-resistant materials.
5. If the engine cowl is of flammable material, line the interior surface of the engine bay with fire-resistant material, if allowed by regulation.
6. Possibly an engine bay temperature monitor / continuity wire to detect fire ? Could be difficult to achieve, without extensive experiment; might cause unnecessary engine shutdowns, but if developed to a high level of reliability and accuracy, could give early fire warning to the pilot. So, worthwhile.
7. Fuselage-mounted fuel tanks possibly pose a fire risk to the pilots & passengers in an accident and occupy fuselage space which could be used as stowage areas for luggage or equipment; wing-mounted fuel tanks are well away from the cabin and the engine ( on single-engined airplanes ), and also unload the wing spar, so are better from the structural or safety point-of-view ( see item 2 above ).

In summary, this fire was unexpected ( as the airplane was in excellent condition ) and unusual ( as the Rotax engine and LSA's in general have a very good safety record ). It is not possible to conlusively ascertain the cause of the fire.

[planedriver]

Regardless of the cause, I and many others feel for your loss.

At least you are still with us which is the main thing.

[onetrack]

AT3 - Thanks for the clarification and the comprehensive fire report. It's a shame (and of major concern) that the cause of the fire could not be positively identified.

You were very lucky, a fire when airborne is the nightmare of all pilots. The aircraft loss is highly regrettable, but it always pays to keep in mind aircraft can be replaced, humans can't.

[facthunter]

Sad with the sudden loss of the Plane AT3. Hope it's covered and you  recovered from the shock . As I've mentioned in my posts here , I'm not a fan of float carburetters in planes especially when they are mounted high up. Floats are the subject of an AD with that engine. In flight fire is about the most serious thing you will encounter and you are "lucky" to have not experienced it. I'd buy a lottery ticket on the strength of it.  Good luck and thanks for your "on the spot" account..  Nev

[Admin]

Fantastic contribution @AT3 pilot thanks very much, especially what you felt you learnt from this very unfortunate event...but great to know you are still here with us

[F10]

I think the Bings are pretty cool, check floats regularly, easy enough with those pop off float bowls. However the fuel pump locarion on a 912 is not the best... I think I will take my Gazelles lower/top cowlings off every 5 or so hrs, to check for leaks, and all pipes and fittings.  

[jackc]

I wonder IF something like this fire suppression kit is worth considering?

https://www.onallcylinders.com/2016/06/03/race-car-fire-suppression-systems/

 

[F10]

Possibly, but one thing I'm also considering is installing a small fire extinguisher in the cockpit, BUT, clearly this will have to be safe (not go off inadvertently) must be light enough, not potentially foul controls, so...may not be feasible. But it must be bad to have to stand back and watch it burn, powerless to do anything....

[onetrack]

You can buy a .75kg hand-held dry powder fire extinguisher for $21. It weighs 1.8kgs in total. It contains enough dry powder to put out any small fuel or electrical fire. Dry powder is extremely effective.

 

You have to squeeze the two handles together to make them go off, so it's highly unlikely they would go off accidentally.

 

Any fire that's big enough to not be quelled by this extinguisher, and you might as well just call in the firies.

 

https://www.firefx.com.au/product/0-75kg-abe-dry-powder-fire-extinguisher

 

 

Edited May 5, 2021 by onetrack
...forgot to add link

[jackc]

I worry about about an engine fire in flight, rare chance of it happening but catastrophic IF it happens.......

[F10]

That's every pilots nightmare.....!