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- Mar 5, 2017
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After reading the GPH and TAS you all attain in your Dakotas, I really feel that Im burning more fuel than I should be. I will try to state my observations only without too much conjecture because I am quite limited in my knowledge of mechanics.
1) I attain close to book TAS numbers when I leak to peak EGT or ROP. However, I am burning anywhere between 1-2GPH than indicated in the POH for leak of peak and burn 3GPH more than indicated in the POH for ROP. For example,
-last night I attempted 65% lean to peak power settings at 5,000ft 15 degrees C. I leaned to the first cylinder that peaked and obtained 120TAS, 5 knots less than book but at 12GPH which is 1.1 GPH more than book.
-I have more experience flying at 55% power setting, during which I reproducibly require 11.5GPH to fly the book TAS. However, POH says that I should be at 9.3GPH at this setting, but if I try to lean to that fuel consumption the engine runs way too rough. At 9.8-10GPH GPH, the engine runs smooth but the TAS decreases to 105-106 knots or so at 4,000 feet at 16 degrees (again about 5 knots slow compared to book and burning more fuel than I should).
-I trust my fuel flow meter based on correlating gallons remaining with the amount that I fill to top off at the pump.
2) Two or three of my cylinders run below 300 degrees. I have attributed this to usually running 55% power, but this remained to be the case after flying the plane yesterday at 65%. #1 always runs below 300. #2 often runs below 300 at 55% power but did increase to 310 degrees at 65% power. #6 has always run at about 320 degrees (at 55%) but yesterday was one of the colder cylinders running about about 290 degrees only on the return trip. The point is, most people talk about being careful about not getting CHTs too hot, and here I am with the opposite problem.
3) Mag checks are rough on the first attempt of the day. I do lean aggressively for taxi, almost to the point of the engine quitting. I have managed this by leaning during the run-up at 2000 RPM whereas I previously did the run up smoothly with the mixture full rich.
This engine is 77 hours post overhaul and have otherwise no complaints. The mag check roughness appeared about 25 hours ago. During the first 25 hours I ran it full rich at 75% power settings and 50 degrees ROP above 5,000 and otherwise full rich according to what the overhaul shop recommended.
Have any of you experienced this in your Dakotas? I was wondering if I may have already fouled my spark plugs especially the way that I didnt lean the first 50 hours or so. Or perhaps there is no problem at all and I fall within 2 SD in the bell curve.
1) I attain close to book TAS numbers when I leak to peak EGT or ROP. However, I am burning anywhere between 1-2GPH than indicated in the POH for leak of peak and burn 3GPH more than indicated in the POH for ROP. For example,
-last night I attempted 65% lean to peak power settings at 5,000ft 15 degrees C. I leaned to the first cylinder that peaked and obtained 120TAS, 5 knots less than book but at 12GPH which is 1.1 GPH more than book.
-I have more experience flying at 55% power setting, during which I reproducibly require 11.5GPH to fly the book TAS. However, POH says that I should be at 9.3GPH at this setting, but if I try to lean to that fuel consumption the engine runs way too rough. At 9.8-10GPH GPH, the engine runs smooth but the TAS decreases to 105-106 knots or so at 4,000 feet at 16 degrees (again about 5 knots slow compared to book and burning more fuel than I should).
-I trust my fuel flow meter based on correlating gallons remaining with the amount that I fill to top off at the pump.
2) Two or three of my cylinders run below 300 degrees. I have attributed this to usually running 55% power, but this remained to be the case after flying the plane yesterday at 65%. #1 always runs below 300. #2 often runs below 300 at 55% power but did increase to 310 degrees at 65% power. #6 has always run at about 320 degrees (at 55%) but yesterday was one of the colder cylinders running about about 290 degrees only on the return trip. The point is, most people talk about being careful about not getting CHTs too hot, and here I am with the opposite problem.
3) Mag checks are rough on the first attempt of the day. I do lean aggressively for taxi, almost to the point of the engine quitting. I have managed this by leaning during the run-up at 2000 RPM whereas I previously did the run up smoothly with the mixture full rich.
This engine is 77 hours post overhaul and have otherwise no complaints. The mag check roughness appeared about 25 hours ago. During the first 25 hours I ran it full rich at 75% power settings and 50 degrees ROP above 5,000 and otherwise full rich according to what the overhaul shop recommended.
Have any of you experienced this in your Dakotas? I was wondering if I may have already fouled my spark plugs especially the way that I didnt lean the first 50 hours or so. Or perhaps there is no problem at all and I fall within 2 SD in the bell curve.
