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Final report N800PB

rv8ch

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https://data.ntsb.gov/Docket?ProjectID=102005

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/102005/pdf

Inflight fire, possibly due to engine failure. Seems like the #2 cylinder bolts came loose, dumped all oil, triggered fire, but not 100% clear from Superior's report:

SUMMARY OF ENGINE EXAMINATION

• Superior XP Experimental IO-360-B1DA2 s/n 03207

• The airplane was subject to a fire and the engine exhibited significant thermal damage and corrosion.

• Data plate missing. Doesn’t appear to have been installed.

• The engine had already been removed from the airframe

• The rear accessories were still attached

• Oil filter 6/10/2019. Filter element cut open and was unremarkable. No visible contamination or metallic debris

• Slick magneto internal components were likely fire damaged. Impulse coupling snapped when the engine was rotated through

• Timing was not possible due to magneto damage

• Case deck studs and through studs were inconsistent, some loose and some tight.

• No. 2 cylinder bottom forward deck stud was mostly backed off and hanging on by ½ thread. The top rear through bolt was tight. The top forward deck stud was missing and coincided with the hole in the case

• No. 2 cylinder removed. The piston was seized inside the cylinder. The connecting rod was seized on the piston pin and couldn’t move. The rod end was distorted and damaged.

• No. 1 cylinder flange was impact damaged and rounded in a couple places which wouldn’t allow it to be removed

• Nos. 3 and 4 cylinders removed and documented. No obvious issues

• Oil sump contained metallic debris and honeycomb material. Likely came in the from hole in the case and settled in the bottom of the oil sump

• Not much oil observed but the oil lines had burned away and likely allowed the system to drain after the accident

• Oil sump screen clear on the inside with thick dark oil on the outside

• Oil pump and gears unremarkable with no metallic debris noted. Rinsed with solvent and no scratches noted.

• Split the case in order to remove the No. 1 cylinder

• Connecting rod bearing all worn and oil starved. No. 2 was the worst since it failed, then in order most damage 3-4-1

• The main journal bearing are worn and slightly oil starved but not as bad as the rod bearings

• No fretting observed on the case mating surfaces

• No signs of metallic debris in the engine that would indicate a slow/gradual failure of any component
 
So did the bearing oil starvation damage occur as a result of the #2 separation and oil loss, or as the cause of that?
 
So did the bearing oil starvation damage occur as a result of the #2 separation and oil loss, or as the cause of that?

I’m guessing that the #2 cylinder connecting rod hardware came apart and punched a hole in the side of the crankcase next to the #2 cylinder - or something similar. The loss of most/all of the oil most likely resulted in loss of lubrication and fire. I know for a fact that the builder did not build in any extra FWF firewall protection.

What’s the lesson to be learned here? I don’t know if it would have made a difference anyway, but if you look at the pictures on this post, you’ll appreciated the destruction that is possible with a FWF fire. The firewall was lost, as was the entire cockpit area. Much of this may have happened after the airplane was on the ground, because the pilot managed to extricate himself from the cockpit, but the message for us should be - do what you can do to protect yourself from an unlikely, but possible fire - fire wall forward - where all that potential energy exists, fiberfrax or something similar. If it gives you a minute or two to get the airplane on the ground anywhere that you can survive, it’s worth it. An inflight fire is by far the worst circumstance that any of us can imagine, especially considering the time involved in that type of scenario.
 
... An inflight fire is by far the worst circumstance that any of us can imagine, especially considering the time involved in that type of scenario.

That's for sure. There are two places to invest - making sure that this never happens, and making sure if it does you have a much fire resistant material between you and the fire.

These photos of the engine case are shocking, and possibly the result of the cylinder replacement not being done perfectly. Mike Busch has a webinar on this exact thing called Perils of Cylinder Work.

https://www.youtube.com/watch?v=3-3pkRLqoGw

Image from Investigative Photo's-Rel, page 4.jpg

Image from Investigative Photo's-Rel, page 5.jpg
 
How do we know it was in 'inflight fire' and not a fire after the crash (maybe I missed it)?
(If we turn off the fuel in the case of an inflight fire there really is not much left to burn).
I've seen cylinders blown off/crank cases punctured before and doesn't usually result in inflight fire.
Crash landing: turn off fuel and all electrical!
 
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How do we know it was in 'inflight fire' and not a fire as a result of the crash (maybe I missed it)?
(If we turn off the fuel in the case of an inflight fire there really is not much left to burn).

First, this wasn't a fuel fire. it was an oil fire. (From the report: Smoke striations from the cowling into the cockpit were consistent with an in-flight fire
that originated in the engine compartment.
) If the prop continues to turn, the oil pump continues to feed oil to the rotating rod throw. Centrifugal force makes it a sprayer, with atomized oil droplets going everywhere. It's not too different from the classic Parks oil burner formerly used in FAA fire lab tests.

Second, there is indeed a lot of other material to support combustion. I'm working a post-fire repair right now, something I took on partially because of my interest in the area. This one was very benign as engine fires go...airplane parked, engine stopped, no oil, no pumped fuel supply. The "match", so to speak, was fuel escaping from inside a length of firesleeve after the failure of the rubber hose liner. The photo below is illustrative, charring of the really stupid fiber insulation on the cabin side of the firewall panel, telling us where the other side was hot. Source was the hose from pump to throttle. Fire spread was convective, just like a room in a house fire. Heat rises, things get very hot near the ceiling, ignition begins, followed by radiant heating downward and eventual flashover. Here almost all of the combustion was fueled by the rubber and plastic components behind and above the accessory case, which led to igniting the epoxy in the cowl.

Returning to 800PB, I can only theorize from the burn pattern, but the fuselage melting is heavily biased toward the right fuel tank. Witness statements say "...the pilot answered her he was pinned down and needed an ax to free himself, there was fuel and a fire so please hurry". The pilot's request for an ax suggests inability to open the canopy, but that conclusion is speculative. None of us really want to think about how things went from there.
 

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Inflight (or any) fire.

There are two places to invest - making sure that this never happens, and making sure if it does you have a much fire resistant material between you and the fire.

Well, I was having a pretty good morning until I read these posts. Inflight fire has to be THE WORST. I have always worn a Nomex flight suit (and a helmet) just to have those final layers of protection. I was standing in line at OSH decades ago when I noticed the man in front of me had burns on his forearms. An RV-4 fire. :eek::eek: He wished he had a Nomex suit on....

Crash landing: turn off fuel and all electrical! and mags.......

During an emergency landing, this is likely one of the most neglected areas. I think (having been in engine-out situations several times), there is a hope that the engine is going to start again. If you turn the fuel and mags off, you have committed yourself and your airplane to (usually) an off-airport landing. I practice my emergency procedures routinely (probably once a month or so) to have those things I need to do firmly in place in my memory and muscle memory. Among those things are: 1) my emergency check list in my memory without having to look at the red-outlined check list); 2) what landing areas I will likely be able to reach by where they line up on various parts of the airplane.

Again, the best insurance is maintaining your aircraft (and your piloting skills) so that the possibility of these events happening become more remote.....and, if they do, that you are able to "fly it all the way to the crash".

I think I'll go for a bike ride.....:(:(:(
 
An argument to be made for wearing parachutes every flight, aerobatic or not. An inflight fire definitely warrants ditching the airplane.
 
An in-flight fire is likely to see most of the flames pour out through the cowling exit and run the down the belly under your feet. Won't take long before the aluminum floor melts through with the cowling following soon after. The fire isn't going to stay FWF.

Firewall protection standards are only meaningful if the fire stays FWF or is starved of combustibles in the first minute or less.
 
An in-flight fire is likely to see most of the flames pour out through the cowling exit and run the down the belly under your feet. Won't take long before the aluminum floor melts through with the cowling following soon after. The fire isn't going to stay FWF.

Firewall protection standards are only meaningful if the fire stays FWF or is starved of combustibles in the first minute or less.

Yes, I agree. Looking at the cowl exhaust, there's no paint discoloration, and there's no honeycomb there either acting as an insulator, indicating that not much fire went out that way. Doesn't the -8 also have a stainless floor insert behind the cowl exhaust which could have staved off floor burn-through a tiny bit?

Another thing I noticed is the #1 fuel injector stainless line is bent back, like the impact from the crankcase casting piece flying off broke the line at the fuel distributor. If that really happened that way, fuel would have been squirting directly at that hole in the crankcase, making the fire that much worse, plus causing serious power loss in the rest of the cylinders due to fuel starvation. 1st pic also shows the propeller tips intact, indicating the engine was not rotating at impact.
 
Yes, I agree. Looking at the cowl exhaust, there's no paint discoloration, and there's no honeycomb there either acting as an insulator, indicating that not much fire went out that way.

I too agree. The very limited view we have of the underside (first airframe photo, from right front) does show a lot of heavy soot aft of the exit. If in flight, this particular fire would have been in the upper plenum, and heavy soot suggests incomplete combustion, i.e. low temperature. It's different from a fire like some we've seen, when a fuel line came off the engine driven fuel pump. Those have burned through the front floor.

Doesn't the -8 also have a stainless floor insert behind the cowl exhaust which could have staved off floor burn-through a tiny bit?

Stock ramp is aluminum, but it's not the floor.

Another thing I noticed is the #1 fuel injector stainless line is bent back...

Good catch.
 
I am going to withdraw my original comments from this post. With further review, the comments of DanH and hgerhard have merit but I can not add a plausible comment regarding the cause of the seizure within the chain of events.
 
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