Yet more puzzling engine behaviour!

During the course of today's flying my pal hand launched my Warlord combat plane which promptly dropped out of the air. A second attempt was aborted when it was discovered that the engine was running backwards a major clue was the a spray of fuel was being sucked out of the venturi and forwards through the prop!. I thought that only the older side ported diesels like Mills could run backwards. Was this incident a fluke? The fact the plane dropped out of the air indicated the possibility that the engine was running backwards then too. The engine is a CS Oliver Tiger replica with three radial ports.

I have had 2 of the CS replical. One iis a very good motor, the other was so bad I could not get it to start and sent it back. It may be that the one you have has some magor problem. I do think that the oliver had advanced timming so that may be the problem. Try starting it with a softer compression setting and see if that helps.

>During the course of today's flying
>my pal hand launched my
>Warlord combat plane which promptly
>dropped out of the air.
> A second attempt was
>aborted when it was discovered
>that the engine was running
>backwards a major clue was
>the a spray of fuel
>was being sucked out of
>the venturi and forwards through
>the prop!. I thought
>that only the older side
>ported diesels like Mills could
>run backwards. Was this
>incident a fluke? The fact
>the plane dropped out of
>the air indicated the possibility
>that the engine was running
>backwards then too. The
>engine is a CS Oliver
>Tiger replica with three radial
>ports.
>
>Vernon

Vernon,

Are you SURE it was running backwards? One of the symptoms of running way over compressed is that sometimes it will fire prematurely and flip the prop back. When it comes up on compression it will again fire prematurely. The end result is an oscillation that appears to be turning but actually never fully rotates. Sometimes if an engine is doing this, you can lower compression and it will start correct rotation.
Something that always works for me is to make final adjustments by lowering compression until it starts running ragged, then increase compression until it smoothes out.
Remember that adjusting compression is regulating timimg. Once you have reached optimum, increasing compression further only increases running temperature. You may have to compensate a bit for unloading at air speeds, AND final adjustments should be made after the engine has heated up to proper running temperature.

Good luck, hope this helps.
George

> Are you SURE it was >running backwards?

Very definitely. A full throated roar that sucked the exhaust fumes and fuel from the spray bat forwards throght the prop.

> The end result is an oscillation that appears to be turning
but actually never fully rotates.

I am familiar with this phenomenon, my old DC diesels do this occasionally.

> AND final adjustments should
>be made after the engine
>has heated up to proper
>running temperature.

I am still trying to get my flying partnet/mechanic to do this but he is an inveterate tinkerer and will not leave the settings alone. He's getting there.

> Good luck, hope this helps.
>
> George

What I think about diesels this week. The ideal situation is that the engine is started at the running settings of both needle and compression, and that it warms up to a smooth run while one walks out to the handle. I think the engine has to be well broken in and the engineperson needs to be very familiar with the engine for this to work. I'm not sure it will work, even then, with all engines.

For first-flight adjustment, I start the engine set a bit rich on the needle. I set the compression where the engine is running a fairly clear exhaust, let the engine run a few seconds and then point the nose up and turn the needle in until the engine starts missing and then richen it up until the engine is running smoothly. If the engine misses in maneuvers, I rich the needle up a little, If the exhaust is dark, I back off the compression a little. Then try again.

Jim,

what you do is exactly what I do and I leave all my engines set up to run perfectly in the air leaving only the compression to be upped a bit for starting purposes. Unfortunately if I leave my pal with the plane he will tweek the needle and compresssion on my way to the handle, I know he's doing it even with my back turned as I can hear the change in engine note...he can't as he has suffered some hearing loss. Short of replacing the compression screw with a Hex socketed screw and supergluing the needle valve in position I don't know how I can gurantee that the engine will run as I have set it up. I do get cheesed off sometimes when I wipe the dark grey overcompressed engine oil evidence off my planes knowing that I left them with clear efflux.

It sometimes makes me want to move to glow engines - one less thing to play with