Of interest Bruce. Our H36 is S/no 3537. Ex Thai Air Force. I have included some more modern features which are .. 1). Am electronic VDO tachometer. It is driven by a Hall effect sensor (from Spruce and Specs) mounted in the lower Mag vent. Very accurate as 50Hz ( our mains power frequency here is a good calibration source .... 3000 RPM) 2) MGL fuel computer. It is multi point calibrated at flying attitude using the original VDO float and displayed the fuel quantity in both a LCD barograph and digital, plus instantaneous fuel flow in L/hr or Gallons, Plus range calculations etc. 3). An MGL CHT. It monitors all 4 Cylinders
Probably the most helpful is the fuel computer as the Dimona is a bit tricky to check fuel level. Re yr problem.. you could check the fuel flow. Take off the feed to the RHS carb and drain into a measuring cup. Run the pump for say 10 secs and calculate the per min and per hr flow. U should get around 40L per hr from memory If u have a Hardi pump (should be behind the seat along side the brake master cyl) they have a 1500 hr life. And not that reliable if used longer. The electronic ones havn’t got that limitation. Also if the SB has been followed there is an in line fuel filter mounted behind the rear panel of the baggage area. The engine driven pump also has a gauze strainer to check. We have had a bit of drama down here regarding Hoffman prop servicing which I think is getting sorted ... I am still waiting after 6 mths for a Grob 109 prop to be returned. Of interest, I use a small piezo buzzer and a 1.5 volt battery for mag timing. Works well. Sent from my iPhone > On 2/06/2020, at 3:14 AM, Ian Williams <[email protected]> wrote: > > Hi Bruce, > Nice Video. We are just going into winter in New Zealand so not much > flying at the moment. > Re low RPM > Are all compressions ok. Check tappets I set to 6thou inlet and 8 exhaust > What do the spark plugs look like. The centre anode should be a slightly > darkish brown and all plugs should look the same > Check out the condition of the carb rubber diaphragms there may be a split > one. Easily done by taking the top off the carb. Be careful putting it > back together the diaphragm has a little key protrusion on it. > Replacement “kits” for those carbs are still available > I have had a magneto failure... caused by a failed condenser .. had a 20 > year life of no action then broke down after around 120hrs. But that was a > dramatic power loss. > Presumably the mag has had its 2 year bench check and the timing was set up > correctly > Also presumably the prop has had its 7 year maintenance “relife”. If so > maybe the pitch angle is too coarse. > Just a few ideas. I would be interested in what u find > > We get around 2950 static 3200 at 55kts climb in fine pitch > Cruise at 2800 to 2900. Coarse pitch and cruise speed around 90 to 95 kts > Our Dimona is a early one with the original aileron push rod configuration so > we do get some aileron upward deflection at cruise. Not a bad thing tho ... > both ailerons deflect upwards around 15 to 20mm giving some reflex. > > Best regards > Ian Williams > ZK-GCB > New Zealand > > > Sent from my iPhone > >> On 2/06/2020, at 1:23 AM, pattoninfl.aol.com via dog >> <[email protected]> wrote: >> >> Hello All, >> >> We now have our Dimona flying again after her 12 year hiatus. Check out the >> video: >> >> https://youtu.be/kKg5CO4YZlw >> >> I was able to fly her but we are still getting limited RPMs. On ground I >> was barely getting the required 2700 RPMs. In flight the most I could get >> was 3000 RPMs. Due to this she had a much slow climb than experienced when >> I flew her 12 years ago. When I tried to fly her yesterday, which was a >> much hotter day, I could only get 2500 RPMs during preflight checklist so I >> didn't fly. >> >> Can you give me any suggestions that might be causing the loss of RPMs? >> >> Thanks, >> Bruce Patton >> N22TC
