Good morning/afternoon
I am just wondering if anyone might have come across the following problem ? The one year old engine will not give a clean cut off (LCO) when hot (runs on for 5-10 secs). It has two P mags installed. The engine has done 110 hrs but the problem has been there some time. Superior stated that the normal problem with these symptoms is a scored plate (mixture control rotating plate). Engineering at my airfield (UK) have plenty of experience of servos (mine is a Precision) so I worked with them for a couple of hours to try and find and fix the problem. We checked to see if any fuel was leaving the servo outlet to go to the spider with the Andair pump on (+/- 35 psi) at LCO and there may have been a hint of fuel but minimal. We took out the plate and although the slightest marks could be seen the chief engineer was one hundred percent sure that it did not amount to scoring or could be the cause. We took the last filter (servo) out and cleaned and inspected (perhaps the smallest debris from manufacture but hardly noticeable) and flushed fuel through before reassembly. Took each injector nozzles out to ensure air bleed holes clear. We reassembled everything and tested for fuel getting past the servo at LCO ? none. Test flew two circuits and LCO fine. Next longer flight, and on the ground, taxying back for several mins (meaning hot everywhere under the cowlings) and LCO was the same problem. It is also the same whether LCO is attempted at 1000 rpm or 700. LCO is only a problem when very hot under the cowlings (eg after a long taxi on landing) and that?s only ever been the circumstances when the problem occurs. In addition, my RV7 has always been particularly difficult to start, hot, trying all normal, ?Injected Engine? hot start procedures (cold she starts perfectly). I am wondering whether the cause of the difficult hot starts could be associated with whatever is the cause of the poor LCO (I realize the hot start difficulty may be nothing to do with the LCO problem). As an aside, it is a vertical air intake servo.
Any similar experiences and solutions would be much appreciated.
Regards
David Robbins
I am just wondering if anyone might have come across the following problem ? The one year old engine will not give a clean cut off (LCO) when hot (runs on for 5-10 secs). It has two P mags installed. The engine has done 110 hrs but the problem has been there some time. Superior stated that the normal problem with these symptoms is a scored plate (mixture control rotating plate). Engineering at my airfield (UK) have plenty of experience of servos (mine is a Precision) so I worked with them for a couple of hours to try and find and fix the problem. We checked to see if any fuel was leaving the servo outlet to go to the spider with the Andair pump on (+/- 35 psi) at LCO and there may have been a hint of fuel but minimal. We took out the plate and although the slightest marks could be seen the chief engineer was one hundred percent sure that it did not amount to scoring or could be the cause. We took the last filter (servo) out and cleaned and inspected (perhaps the smallest debris from manufacture but hardly noticeable) and flushed fuel through before reassembly. Took each injector nozzles out to ensure air bleed holes clear. We reassembled everything and tested for fuel getting past the servo at LCO ? none. Test flew two circuits and LCO fine. Next longer flight, and on the ground, taxying back for several mins (meaning hot everywhere under the cowlings) and LCO was the same problem. It is also the same whether LCO is attempted at 1000 rpm or 700. LCO is only a problem when very hot under the cowlings (eg after a long taxi on landing) and that?s only ever been the circumstances when the problem occurs. In addition, my RV7 has always been particularly difficult to start, hot, trying all normal, ?Injected Engine? hot start procedures (cold she starts perfectly). I am wondering whether the cause of the difficult hot starts could be associated with whatever is the cause of the poor LCO (I realize the hot start difficulty may be nothing to do with the LCO problem). As an aside, it is a vertical air intake servo.
Any similar experiences and solutions would be much appreciated.
Regards
David Robbins