"Flame-Out" Over Olympia!

[gyropilot]

Hi everyone,

As Paul Plack mentioned over on the 2-stroke durability thread, I had experienced my first real engine failure while performing on Friday at the 6th Annual Gathering of Warbirds (a.k.a. Olympia Airshow). Both me and my GyroBee are fine.

I was maybe 3/4 way through my flying routine when this happened. I had just climbed downwind to 1000' AGL directly over the airport at full power, throttled back to cruise, did a tight left hand 180 degree turn into the wind, and was setting up to demonstrate a vertical descent down to 500' AGL. I smoothly throttled back to idle while pulling the cyclic back to zero out the airspeed. Upon reaching zero airspeed, the vertical descent started and, as expected, rudder control became non-existent. The gyro began an uncommanded yaw to the left, and since I didn't want to turn completely away from the crowd, I began applying a bit of throttle to regain some rudder control.

Everything happened to fast from there that I'm not exactly sure I trust my memory on the exact details. I think I remember the engine started to increase in rpm, and I remember I was starting to regain the rudder control I wanted and was starting to yaw back to the right. As this was happening I felt the engine vibration change... maybe getting a slight bit rough and starting to bog down or "load-up"... that's the best way I can describe it. My instinctive reaction was to apply a slight bit more throttle to smooth things out, but as I advanced the throttle, the engine further bogged down, and as I continued to push the throttle to the stop, the engine died.

There I was with the throttle all the way open and dead silence except for the hum of the radio in my ears. It felt like someone had just reached out of the sky and shut the fuel off, or maybe the ignition off. No warning... no coughs... no sputtering... nothing. The engine felt like it made a normal stop (not screeching to a sudden stop). It probably took just a couple of seconds from the time I started advancing the throttle until the engine stopped.

The training kicked in and I instinctively nosed the gyro over to regain my airspeed and set up my approach for landing to the main runway. I was probably 300 feet off to one side of the main runway and started a turn to line up. On the way down I remember thinking what a great location for an engine failure... 1000 feet over the middle of a huge airport with no traffic but me and a 5800 foot long runway, and a 10 mph wind blowing within 20 degrees of the runway! I thought that if I screwed this up, I deserved whatever thrashing I would be subjected to at the bottom.

I remember concentrating on keeping the airspeed in the green (45 to 55 for my gyro) and not flaring too early. The initial and final flare were right on and I nailed a perfect zero roll landing. All those 100's of engine-idle approaches I've made over the last 2 or 3 years paid off. The only difference I could detect was the silence (I could hear the popping of the blades during the flare) and it seemed like I had to work harder to keep the airspeed from bleeding off. This later phenomenon could have been caused by me being anxious to start the initial flare.

Upon landing my initial reaction was to get the blades stopped, tied down, and get the gyro off the runway so the air show could continue. It was a long brisk walk back to the parking area pulling the gyro all the way. The tower sent out a tug and support vehicle but they were of no use... no way to quickly hook up to a gyro nose wheel.

I was thoroughly embarrassed at the whole thing. All morning I was blabbing on to air show visitors about how reliable my little 2-stroke Rotax 503 is and how it's never so much as coughed on me. The shame!

Mercifully, I later found for the airshow PA system quit at the same moment I had my engine failure. I wonder if the two might be connected? Aliens? Anyway, because of the PA system failure, later it became apparent the crowd watching simply thought the whole thing was part of the routine. When I told them the truth, a few reported they did think it odd that I had to walk the gyro a mile back to parking... like wouldn't it have been easier to taxi back?

You always hear it's not "if" you'll have an engine failure when flying someday... it's "when." I can't tell you how happy I am that my "when" came at the place and time it did! Immediately after it happened I had flash backs of every tree, house, and wire I've flown over in the last 50 hours of flying. Sends chills up my spine.

At this time I don't know what caused the engine to quit. After I got the gyro back to the parking area, I found the fuel lines full and the carb bowls completely and equally full. I didn't think to actually measure the fuel level in the float bowls, nor did I think to pull a plug and see if it was wet with fuel (to rule out flooding). It would seem that fuel starvation was not the cause.

As I went over the events in my head that night, I started thinking I might have induced a cold seizure.

When I put the gyro away back in my hanger today, I did make a couple of cursory engine checks to rule out a few more possibilities. The good news is that nothing appears to be wrong with the engine. The bad news is that I have no idea what's wrong with the engine!

I pulled the exhaust manifolds and using a flashlight, found no evidence of a seizure on either the pistons or the cylinder walls. An aside: I was pleasantly surprised to find the piston domes and cylinder heads free of any carbon deposits. I've been using Texaco Havoline 2-stroke oil exclusively since the last decarboning about 25 hours ago. The only thing of interest I noticed by looking in the exhaust ports was that the that PTO end (rear) piston had a thin film of black semi-dryish soot on it that I could easily smear off with my finger. This might be a clue of something, but I'm not sure what... yet. I used a rag to wipe the soot off and found the piston in perfect condition otherwise. When I worked the piston up and down in the cylinder, a trace film of dirty oil appeared in places on the piston skirt... apparently being picked up from the cylinder wall. The mag end piston appeared clean and lightly lubricated with oil.

So at this point cold seizure appears to be ruled out... as well as lubrication failure (I carefully premix my fuel and it had the proper amount of oil in it). Oh... the fuel mix was about a week old... not the idleal thing to use I know, but hardly the culprit for an engine failure.

I pulled the plugs and found them as usual... medium brown with no sign of fouling, soot, or running lean.

I checked that the piston rings are free in their grooves and I performed a compression check with the engine *cold* (as I'm not restarting it until I'm positive it's not damaged. The CPS catalog says normal hot compression readings for a 2-stroke Rotax engine are between 120-160 psi with an electric starter. I got 110 psi on one cylinder and 116 psi one the other with 3 brisk pulls of the pull-starter. That seems pretty good for a cold 150-200 hour engine.

I pulled off the air cleaners and verified both carb slides open equally and in unison.

That was all I had time for today. When I get a chance I plan to check the ignition for spark and verify the crankshaft "timing" (that the two halves of the crank haven't moved in relation to each other). Failing finding anything there, I might try looking at the carbs (rebuilt only 25 hours ago). After I've exhausted all possible static checks, I'll try some ground run-ups with the gyro tied down.

If anyone has any other suggetions, I'm open.

Best regards,

John L.

[GyroRon]

John I wouldn't be able to resist temptation and not try to run it to see if it will even restart. I would try to start it myself and see if it runs.

[scott heger]

John, glad to see you are alright. I also would try a restart if the compression checks ok. If it runs well, it is not out of the realm of possiblity that you experienced a carb ice situation. You did not say what the weather was , but the conditions, and the order you did them are perfect setup (partial throttle to idle) for this kind of situation to occur. Iceing on Rotaxs is very rare, but it happened to me while training at SportCopter. All the evidence of this problem "melts" within a few minutes, making it hard to diagnose.

Scott Heger, Laguna Niguel, Ca SportCopter N86SH

[WN]

John,

Your paragragh describing the moment the engine died sounds like a classic fuel pump failure.

[Udi]

Glad you are ok, John. Have you considered inadvertent closure of the ignition switch?

Udi-

[gyropilot]

Originally Posted by GyroRon

John I wouldn't be able to resist temptation and not try to run it to see if it will even restart. I would try to start it myself and see if it runs.

Ron,

It is tempting.

There happened to be a local certified Rotax rebuilder at the airshow hanging around with the powered parachute crowd. After the engine failure I chatted to him a bit, and had couldn't emphasis strongly enough that I shouldn't restart the engine until I had figured out what was wrong. He said that restarting would only cover up any evidence and make a proper diagnosis more difficult, and could possibly damage the engine further making repairs more costly. Since there was no pressing reason for a restart (I wasn't stranded out in the middle of nowhere with no other means to get home), his logic sounded solid to me.

This rebuilder was the one who told me I should remove the exhaust manifold, peer in the exhaust ports, and examine the piston and cylinder walls for signs of seizing. I told him that although I've rebuilt many engines over the years (auto and motorcycle), I've never before actually seen one that's been seized... Rotax or otherwise. He assured me that it would be very apparent if my engine had suffered a seizure (hot or cold) and proceeded to give me a few tips on what to look for.

So Sunday when I pulled the exhaust manifold and looked at the pistons and cylinder walls, I really didn't see anything that looked abnormal to me, so I felt pretty confident it was not a seizure. But then later on Sunday evening I re-read some of the excellent fault diagnosis articles in the back of the CPS catalog written by Mike Stratman and am starting to have second thoughts. An aside, Mike's advice was the same... NEVER restart an engine that quit until a careful methodical diagnosis is performed and you absolutely rule out any internal damage. Obviously there are times when you must violate this advice.

One of Mike's article talks in depth about the difference between a cold and hot seizure. He describes where to look on the pistons and cylinder walls for each type. According to him, a cold seizure begins basically at 4 places around the piston as it contacts the cylinder walls. That would be on either side of the wrist-pin holes NOT in-line with the piston skirt and the exhaust ports. Because of these locations, I'm thinking that evidence of a minor cold seizure might not be easily seen by looking through the exhaust ports. It could take removal of the heads and cylinder sleeves. I'm going to call CPS this afternoon to get their opinion of this.

Regarding engine seizures, from what I read, if my engine did seize, it would have been a cold seizure. A hot seizure involves high EGT and a meltdown. Clearly this isn't the case. A cold seizure is simply an interference problem between the pistons and cylinder walls caused by the piston expanding faster than the cylinder walls (or conversely the cylinder walls cooling faster than the pistons). I can rationalize that I could have caused the later the way I was operating the engine (full-power followed relatively closely by engine idle). However, cold seizures are usually seen more often in cold air temperatures when the engine isn't allowed to warm and heat-saturate sufficiently before going to full-power. It was 95 degrees outside when my engine quit and had been running for 18 minutes (by the Hobbs meter)... and 10 minutes of that was between 2000-3000 rpm as I prepared to taxi and taxied out to the runway. All that considered, it would sort of seem to make a classic cold seizure less likely.

Mike Stratman says a cold seizure is the most common type and it leads to what he calls: "The self-healing engine syndrome." This is where an engine quits (cold seizes) and then restarts easily on the ground after a brief cool down. He points out that engines don't magically heal themselves after a seizure and the problem will only get worse later even if it does restart due to cylinder and piston damage. He still suggests an internal inspection to rule out anything.

The bottom line is I really want to make darn sure it wasn't a cold seizure before I attempt a restart. I'm leaning toward making a few more diagnostic checks first (ignition and such), and then probably pulling the heads. It really doesn't take that much time and would be peace of mind.

Regards,

John L.

[gyropilot]

Originally Posted by scott heger

If it runs well, it is not out of the realm of possiblity that you experienced a carb ice situation. You did not say what the weather was , but the conditions, and the order you did them are perfect setup (partial throttle to idle) for this kind of situation to occur. Iceing on Rotaxs is very rare, but it happened to me while training at SportCopter. All the evidence of this problem "melts" within a few minutes, making it hard to diagnose.

Good thought Scott, but in this case I seriously doubt it.

The OAT was close to 95 degrees and even then, I don't think I would have been at idle long enough for it to happen.

Would be be nice if that's all it was.

John L.

[gyropilot]

Originally Posted by WN

Your paragragh describing the moment the engine died sounds like a classic fuel pump failure.

Steve,

That's exactly what I thought it would be as I was gliding to the ground.

However, once back on the ground I found the fuel lines were full and the float bowls were full. I carefully rebuilt the fuel pump (dual Mikuni) only just last winter... some 25 hours ago. I rebuild it with new gaskets and diaphragms each year.

The fact that the fuel lines and float bowls were full seems to me to cancel out a fuel supply problem. I don't see any way they could all fill up after the engine stops.

Regards,

John L.

[gyropilot]

Originally Posted by Udi

Have you considered inadvertent closure of the ignition switch? Udi-

Udi,

I haven't ruled out yet that the ignition somehow stopped working. That's high on my list to diagnose next.

However, my 503 has the dual Ducati electronic ignition systems. These are two completely separate systems with separate spark plugs. The only thing they share in common is some of their components are mounted on the same flywheel. There are two separate kill wires running to two separate kill switches mounted on the instrument panel. The two kill switches share a common grounding wire.

The system is designed to fail "on." If the engine wiring harness connector comes apart, the engine can't be turned off via the kill switches. It would be a remote possibility for both grounding wires or kill switches to short out or fail, but I'm not willing to rule anything out yet! I plan to check it out.

Thanks,

John L.

[barnstorm2]

John,

Glad to hear you are OK. I hope you find the problem is something easy and cheap to fix. You are doing us all a big favor by flying your gyro at airshows and introducing gyros to people this way.

I hope you are back in the air safe and soon!

[ToddP]

John,

From experience, the evidence of cold seizure is very apparent. It would have been pretty obvious from your inspection through the exhaust ports.

As unnerving as it may be, it appears you are closing in on the final diagnosis of "**** happens". It was probably a random combination of of uncontrollable variables that created the engine out. Very Hot Day, Humidity, High Power to Idle then Back, Sudden Change in Altitude who knows. Everyone is pretty aware the Rotax will never equal the lycoming for reliability. Your diligence in finding the problem is certainly warranted and it would be ideal if you found the problem, but if you don't, I hope this won't slow you down.

[gyroman]

The way you describe it John sounds like it was choked for fuel. My guess is something in the carbs, especially since you just rebuilt them.. but what the heck do I know, I rebuilt my boat engine completely and for some reason I've gone through 2 powerpacks already, I think I might have a bad coil... but my compression in both cylinders is spot on.... Hope you find out the cause and let us know...

[gyropilot]

Originally Posted by barnstorm2

You are doing us all a big favor by flying your gyro at airshows and introducing gyros to people this way.

I hope you are back in the air safe and soon!

Thanks Todd.

A little story:

Besides having my rating, medical, and BFR verified, I had to have my gyro inspected by an FAA representative prior to performing in the airshow. One of the things he wanted to see was the airworthiness certificate. He also had to look at the aircraft logbook to see my last annual signoff. He flipped through the pages and then while handing it back, he said he'd never seen a neater, more detailed logbook (I keep notes of everything I do to it) on any experimental aircraft he's ever seen. He shook my hand, congratulated me, and commented that he thought everything looked very professional. Coming from an FAA official I felt very proud not only for myself, but for gyros in general. Slowly we're gaining their respect and acceptance.

Then I have an engine failure!

I remember that one of my first thoughts when the engine quit was along the lines of: "Crap! This is a terrible example to set in front of all these people... especially the airshow officials. Why does this have to happen to me?"

Hopefully they were impressed enough with the outcome that it cancelled out the negative feelings. The airshow personnel who knew what happened were really good about it and wanted to make sure I was all right. The FAA officials said nothing about it... and since an engine failure in and of itself isn't a reportable incident, I didn't talk about it either.

Regards,

John L.

[gyropilot]

Made it back to the hanger last night after work and checked the engine for spark... there's plenty.

So there was fuel and spark, that kept pointing in the direction of a cold seizure.

Next I pulled the cylinder heads off and sure enough, I found the rear (PTO end) cylinder appears to have suffered a minor cold seizure. There are two obvious "smears" of aluminum about 1/4 wide by 1" long on opposing cylinder walls in locations that, according to Mike Stratman in the CPS catalog, are in the classic locations for a cold seizure (starting on either side of the wrist pins). The spots were not possible to clearly see when only looking through the exhaust ports... the heads needed to come off to be sure.

Interestingly, the front cylinder looks pretty much fine with maybe one tiny spot that was starting to smear.

The cylinder wall damage looks minor and I'm sure the engine would easily restart and *seem* to run fine. But the condition won't heal itself and would likely get worse quickly. It'll have to be properly repaired to assure reliability. Repairs will involve removing the cylinders, having them bored one size over, and fitting new pistons and rings. The engine can remain on the gyro for this and the total cost should be between $400-$500. I estimate I should be back in the air within a month.

Cause of the failure: Pure operator error by going too quickly to idle after a full-power climb. I wish I could blame it on something else, but I can't. The sad part is I should've known better too!

I remember reading an article somewhere that said one of the worst things you could do to an air-cooled 2-stroke engine was to go to full power with a cold engine. That's followed closely by going immediately to idle after full power. The article suggested that when going from full power to idle, the throttle should be gradually reduced over a period of one minute to give the pistons and cylinders time to cool together at the same rate.

Well my engine gave me a little reminder of that article last Friday and you can bet I won't forget it!

Every flight is a lesson.

Regards,

John L.

[Caribean_gyro]

where is the fuel pump mounted? Next to a hot area? SOund like vapor lock

CHukP