gyropilot
06-20-2004, 04:18 PM
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.
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.