Engine-out "practice"

[thallett]

Takeoff oK. Climb to 500 feet oK. Left traffic crosswind oK. Then SILENCE. Very sudden. No clunk, shudder or sputter. Just that golden silence, except the reassuring shwoos-shwoos of the blades. Turned back toward the airport and landed on a cross-taxiway. On the way down I called in a dead-stick landing and tried a restart on the engine: no firing. After landing, tried a restart and got only a sputtering. On climb out had noticed the aft cyclinder temp was higher than the other cylinder at about 500 degrees (536 is max by the book). EGT was about 1400. That's normal for the sensor location which is at the junction of exhaust for both cylinders. RPM ran between 5500 and 6000. Climb was about 500 FPS at 50-60 mph. At home I checked cylinder pressure and got 130 PSI on the front and 60 on the aft cylinder. Found that it would run oK briefly to 4000 RPM. Couldn't try more power here in the yard. Looks like I need new rings/cylinder. Removed the head and looks good. I'm wondering if the higher temp could have been due to leaking rings/lean running?? I couldn't find a record of cylinder pressure from before this. Anyone know where parts are available for HIRTH 2703 55hp?
Thanks. Tom Hallett

[Brian Jackson]

...Climb was about 500 FPS...

Holy cow! :eek:

[Chuck Irby]

Well, we know what he meant, huh? :D

Tom, what engine do you have?

[thallett]

Engine is a HIRTH 2703 55 hp.

[Chuck Irby]

Tom, I know that we're all disappointed for you re that problem with the Hirth, but glad that it happened where it did. Please keep us informed as to what you discover re the problem.

I practiced twelve engine outs yesterday morning. However, I wonder a lot about how it will all work out if it happens for real, when I am away from an airport and have to land on a road bed, or worse. My all time best friend had to set a turbo prop down on an Interstate highway once. He was fortunate that time.

[StanFoster]

Chuck: The first real one is like hitting a hole in one. :) I was ecstatic when I had to walk home three miles to get a truck to retrieve my mac attacked Bensen. I captured the moment and its in my scrapbook. :)

It makes you so glad you practised and practised engine outs. Nothing like the real one cause it catches you off guard...and your mind just focuses and you do what is conditioned....

Stan

[GyroRon]

Been there, Done that. Keep practicing them when you get it running.

[thallett]

Here's a picture of the aft piston showing scuffing that locks up the rings, hence little compression. I'm not sure what the mechanism is that does this to the piston, but feel that heat is responsible(?). But how does it get started? All comments are welcome.

[scottessex]

Looks like it was too lean, Blown head gasket, or leaking carb boot perhaps.
Time to re-sleeve the cylinder too.

[Chuck Irby]

Wow, that is pretty bad. I agree with Scott... too lean, for some reason.

The reason your engine quit is because that piston ceased in the cylinder. By the time you were able to turn it over, it had cooled off and the piston moved freely again, but with very little compression. Yep, new piston, rings and sleeve. And be sure to find the reason for it leaning out before you start it up again.

Stan, good point about the hole-in-one.

[GyroRon]

Time to get a Rotax

[scottessex]

I've got an Arrow engine that looks similar to that on the inside!

[Doug Riley]

Don't know how Hirths are put togther, but in Rotaxes you can get leaning in one cylinder if the crankcase chamber for that cylinder is letting air in. This can happen as a result of hardened or worn crankshaft seals as well as leaky gaskets. It's common at quite low hours on the Rotax 618, for example. 618 owners will sometimes richen the jet just for the carb that feeds the lean cylinder, as opposed to rebuilding the engine every 30 hours.

It's best to check sparkplug color frequently and calibrate your EGT to what the plug color shows.

[Greg Mitchell]

G'Day Doug,
Would you mind taking the time to explain the process of plug colour/EGT Calibration. Be appreciated.
Regards,
Mitch.

[Doug Riley]

Greg: Maybe "calibration" is too strong a word. Call it confirming or cross-checking.

The correct plug color is chocolate-brown. Lighter brown, tan or gray indicates too hot an EGT and usually is a sign of excessively lean mixture. Black is too cool and typically too rich. This information is based on 2-stroke Rotax experience. Aluminum alloy pistons are aluminum alloy pistons, though, no matter what the brand, and they'll all be really close to melting at 1300-1400 F EGT. Pure aluminum melts at under 1300; alloy a little higher.

(The engine must be shut down promptly after operating at flight RPM for these tests to be valid. An appreciable amount of idling before shutdown may alter the results.)

[Greg Mitchell]

Thanks Doug,
Good info.
Best regards.
Mitch

[Screw]

Screw-In

Hey Doug, How about 4 stroke VW engines? Chocolate still perfect?

Screw-Out

[Doug Riley]

John: I may not be the guy to ask. My VW was forever quitting; usually fried bearings, although one time a piston did look almost like a seized 2-stroke would look.

The Rotax 912S manual provides a max takeoff EGT of 1620 F; max continuous of 1560 F and normal of 1470 F. 4-strokes don't produce as much power per cubic inch as 2-strokes. They have more opportunity to cool off between power strokes at a given RPM (one power stroke every 2 revs instead of one every rev), so they can stand higher peak temps than a 2-stroke can.

[Harry_S.]

Your actual emergency (emergencies) will be a duplicate of all your practiced ones, providing you picked out a respectable landing spot.
That's a reason why I still try to fly over friendly terrain whenever I can, even tho I have confidence in the Soob.

I don't have as many EO's as Stan, but those MAC attacks I did have, were really no problem.

[Ron Marlett]

A tool that every 2 stroke owner should make is a Leak Down tester. It is very simple to make and use. You remove the exhaust manifold and block off the ports. You remove the carbs from the boots and install a plug which has a pressure gauge and a valve on it. You plug the port to the crankcase pressure operated pump. Set the crankshaft so the piston is low enough to expose the inlet ports. You inject about 10-15 PSI of compressed air from a regulated source into the valve then close it and watch for the pressure to leak down on the gauge. It should not. If it does, start with some bubble mix and find your leak. This checks the integrity of the case components(cracks?) the case seals, the crankshaft seals, the cylinder base and head gaskets, the intake manifold and gaskets and the carb boots. I recall a link on a 2 stroke motorcycle forum I visit regularly that had instructions on building your own. I will look for it and post it here if anyone is interested.

[thallett]

Thanks Ron, that pressure check sure looks like a worthwhile setup!

[Ron Marlett]

Well this wasn't the link I was thinking of but it has the same basic info and shows a tester with a schrader valve and reccomends a bicycle pump which would be good if you don't have a compressor where you are wanting to do the test.

http://www.off-road.com/atv/ptester.htm

[Hognose]

Guys,

when I was talking to Hank in the AAI booth, a gentleman named Göbler stopped in announcing new Hirth engines. I believe he is the (new?) owner of Hirth. You can reach Göbler-Hirth Motoren AG at info@hirth-engines.de. Yeah, they can sprechen englisch. Also their website lists Matt Dandar of Recreational Power Engineering in Tiffin, OH as their US distributor. rpe@bpsom.com or website http://recpower.com. The 2703 is still in production so parts should be available. The Hirth Nikasil cylinders might be pretty expensive though.

Sorry you had this problem; glad you landed safely, and hope you are back flying shortly.

cheers

-=K=-

[thallett]

Parts arrived quickly from Recreational Power Hirth Rep and will be doing rebuild soon.

[thallett]

Rebuilt and running break in. I now have "A" size pistons in "A" size cylinders instead of the "B" (oversize) pistons in "A" cylinders. Runs great, but I'm not over 3000rpm yet. We'll see how it does at high power/rpm this week. By the way, the PRESSURE test was a good one with no leaks.