Sun Aug 11, 2019 7:39 pm
#1712150
I'm trying to equate what I am seeing in the aircraft POH (PA32), engine POH io540 3 blade, the wisdom of various blogs e.g. Pelican Perch etc and what I've seen in a couple of test flights!
The question is relating to a cruise climb to 10,000ft plus. From the various sources above I have ascertained:
So my basic understanding of physics suggest that leaning in the climb HAS to happen to achieve best power and the POH's are covering their as* to avoid cooking the engine.
I did try the approach on a test flight.
Interested in your thoughts/wisdom in (a) should I ignore the POH and (b) what did i do wrong in the test flight.
The question is relating to a cruise climb to 10,000ft plus. From the various sources above I have ascertained:
- The POHs suggests mixture full rich until 5000 feet at max power (no limitation on max continuous power due 3 blade prop).
- The POH states 65% cruise power at 10,000 feet should give me 53 litres/hour fuel flow
So far so good. But then: - The aircraft POH then goes on to state that leaning can take place below 65% or above 5000. However this is in the cruise section. Nothing is mentioned in the climb section
- The engine POH states that leaning can be performed by the method of peak EGT or by fuel flow or the "run it till rough and then enrich" method. However, per aircraft POH, it doesnt approve of in climb leaning;
On engines with manual mixture control, maintain mixture control in “Full Rich” position for rated takeoff, climb and maximum cruise powers (above approximately 75%)
- The John Deakin/Pelican Perch method, basically agrees with the "peak EGT" in the engine POH with a couple of deviations. (a) It encourages doing so in the climb. (b) No mention of 5000 feet limitation. (c) It suggests noting the EGT(and eventually CHT) at about 1000 feet and using that. (d) It also mentions, how above a certain altitude, enriching rather than leaning will maintain target EGT/CHT.
So my basic understanding of physics suggest that leaning in the climb HAS to happen to achieve best power and the POH's are covering their as* to avoid cooking the engine.
I did try the approach on a test flight.
- I noted 1500deg EGT, kept leaning to 10000ft, full throttle, 2400 RPM.
- Once I leveled out i noticed i only had 1300deg EGT. I assumed this was due to increased cooling due to airpseed however I noticed that i only had about 40 litres/hour
- so i think I'd hit the peak EGT sooner than anticipated as the POH said I should have about 53 litres/hour for 65% (23 squared)
Interested in your thoughts/wisdom in (a) should I ignore the POH and (b) what did i do wrong in the test flight.
PPL(A) SEP, MEP, SE/IR, IR(R), Night