Airflow Performance Idle Issue

After another phase one flight yesterday and a phone call to AFP, the FM200 and flow divider has been UPS'd back to Spartanburg.

The problem is intermittent and somewhat of a nuisance, one of those things you could live with but it isn't quite right.

The system works great when off idle. But I am wearing out the brakes trying to keep the airplane slowed down with the engine running at 1000-1200 rpm, the lowest smooth rpm available.

Normal fuel flow at idle is about 1.1 gph. The engine is smooth at 700 rpm and accelerates without hesitation. About 70% of the time when the throttle comes back to idle, fuel flow hangs up at 2.2 - 2.4 gph flooding the engine with the throttle closed. It keeps running but very rough and is just on the edge of quitting. This is not a good situation on final as it has gotten quiet on 2 occasions now. The engine comes back to life quick with a nudge of the throttle off of idle but it is a nuisance.

The consensus is there is some junk in the controller preventing the ball from seating properly when at idle. Idle fuel uses its own plumbing and the extra fuel leaking through the high flow route is the problem. I tried flushing for about 5 minutes yesterday and the first taxi and take off was normal but by the end of the day it was back metering over 2 gph at idle after landing, and just like that without touching anything fuel flow dropped to 1.1 and it was smooth again. The ball must have been hung up and seated itself.

I asked about taking the thing apart and checking things over but Kyle said it would be a better idea to let them do it, and I agreed. They have all the necessary test equipment to get to the bottom of it. I must say, the service at AFP is excellent. Stuff happens and they are very interested in resolving the issue.

Has anyone here had a similar problem with the FM200?

I don't know if it is exactly similiar, but my engine would idle at a higher RPM cold than it would hot. I adjusted the idle stop screw down to 450-500 RPM. Upon landing, if I pulled the throttle all the way back, the engine would cough. I just nudged it a nick. However, it really looked like it was leaning out, not over-riching.

Don and his guys will get to the bottom of it.

David-aviator said:

After another phase one flight yesterday and a phone call to AFP, the FM200 and flow divider has been UPS'd back to Spartanburg.

The problem is intermittent and somewhat of a nuisance, one of those things you could live with but it isn't quite right.

The system works great when off idle. But I am wearing out the brakes trying to keep the airplane slowed down with the engine running at 1000-1200 rpm, the lowest smooth rpm available.

Normal fuel flow at idle is about 1.1 gph. The engine is smooth at 700 rpm and accelerates without hesitation. About 70% of the time when the throttle comes back to idle, fuel flow hangs up at 2.2 - 2.4 gph flooding the engine with the throttle closed. It keeps running but very rough and is just on the edge of quitting. This is not a good situation on final as it has gotten quiet on 2 occasions now. The engine comes back to life quick with a nudge of the throttle off of idle but it is a nuisance.

The consensus is there is some junk in the controller preventing the ball from seating properly when at idle. Idle fuel uses its own plumbing and the extra fuel leaking through the high flow route is the problem. I tried flushing for about 5 minutes yesterday and the first taxi and take off was normal but by the end of the day it was back metering over 2 gph at idle after landing, and just like that without touching anything fuel flow dropped to 1.1 and it was smooth again. The ball must have been hung up and seated itself.

I asked about taking the thing apart and checking things over but Kyle said it would be a better idea to let them do it, and I agreed. They have all the necessary test equipment to get to the bottom of it. I must say, the service at AFP is excellent. Stuff happens and they are very interested in resolving the issue.

Click to expand...

The FM-200 and flow divider arrived back from Spartanburg yesterday afternoon.

The problem I described could not be duplicated on their equipment, but Kyle tore down, thoroughly cleaned and reassembled both units, and tested them again. Both checked out like new.

The system was reinstalled on the engine today and I went flying. I works perfect!

Whatever was causing the rough, rich idle is gone. It may have been a small piece of junk and was flushed out in the cleaning process. The engine idles nicely at 670 rpm with a fuel flow of 1 gph. In flight, I can pull it back to idle and it just sits there running smooth at minimum power.

I need that feature because this RV does not like to slow down with the FP Catto.

Very good service from AFP - turn around including the Easter week end was 6 days.