dhillier
07-04-2017, 05:39 AM
I should know the answer but..
I have a O-235 with a Sensenich M76A 74" diameter by 52" pitch cruise prop on my PA-16.
I am trying to establish approximate RPM values for 65 and 75% power for leaning and fuel consumption purposes.
The O-235 operators manual just states RPM vs % power values but does not state which prop this is based upon.
I have not found complete POH for the PA-16 but I do have a PA-22-108 POH (which, lets face it, is as similar as possible ignoring the gear) and that has figures based upon a standard prop which i believe is 74x48. The Sensenich installation guide shows both the PA-16 and PA-22 use 74" diameter props but differ in pitch - (standard / cruise / climb)
PA-16 - 50/48/52 pitch.
PA-22 - 48/-/50.
My questions:
Has anyone any experience between speed and fuel burn differentials for the different types of prop?
For a given RPM I would expect the cruise prop aircraft to be flying at a greater IAS - but will it be doing so at a greater % power and thus greater fuel burn? Surely a greater pitch prop requires more power to spin at a given RPM?
How would I expect the % power to vary between an engine with a climb, standard and cruise prop?
How can I estimate what RPM gives a % power? In the PA-22 POH there is a formula of max cruise RPM - 10% = 75% power. Any comments on this?
I ask all of this as the Clipper cruises at 100mph (TAS - the IAS is very optimistic at cruise speeds) at 2300 RPM with a cruise prop and burns 26L / 6.8 US gallons an hour.
Both the PA-22-108 POH and O-235 manual have very different figures for speed vs fuel consumption.
Obviously I do not expect a 1949 aircraft and an 800hr engine to perform exactly as per the book.
Regards
Dean
N5240H
I have a O-235 with a Sensenich M76A 74" diameter by 52" pitch cruise prop on my PA-16.
I am trying to establish approximate RPM values for 65 and 75% power for leaning and fuel consumption purposes.
The O-235 operators manual just states RPM vs % power values but does not state which prop this is based upon.
I have not found complete POH for the PA-16 but I do have a PA-22-108 POH (which, lets face it, is as similar as possible ignoring the gear) and that has figures based upon a standard prop which i believe is 74x48. The Sensenich installation guide shows both the PA-16 and PA-22 use 74" diameter props but differ in pitch - (standard / cruise / climb)
PA-16 - 50/48/52 pitch.
PA-22 - 48/-/50.
My questions:
Has anyone any experience between speed and fuel burn differentials for the different types of prop?
For a given RPM I would expect the cruise prop aircraft to be flying at a greater IAS - but will it be doing so at a greater % power and thus greater fuel burn? Surely a greater pitch prop requires more power to spin at a given RPM?
How would I expect the % power to vary between an engine with a climb, standard and cruise prop?
How can I estimate what RPM gives a % power? In the PA-22 POH there is a formula of max cruise RPM - 10% = 75% power. Any comments on this?
I ask all of this as the Clipper cruises at 100mph (TAS - the IAS is very optimistic at cruise speeds) at 2300 RPM with a cruise prop and burns 26L / 6.8 US gallons an hour.
Both the PA-22-108 POH and O-235 manual have very different figures for speed vs fuel consumption.
Obviously I do not expect a 1949 aircraft and an 800hr engine to perform exactly as per the book.
Regards
Dean
N5240H