Why is there different power setting tables for an PA28R-201 depending on year when they use the same engine?!
In the POH from 1986→ you have 2500RPM and in the POH from 1978 you have 2400RPM
Also higher MP in the later POH…
They may have changed the propeller? Check also whether the propeller is the same for these tables.
Same Engine, Same Propeller…?
Interesting perhaps Lycoming’s thinking has evolved? The fact that the -201 is taper wing and a better aspect ratio might be a reason, but not sure why.
I expect the taper wing involved more flight testing which resulted in newer, possibly more accurate, performance tables. The old Arrow 2, if I recall, had better performance figures in cruise, while the taper wing 3, the performance reduced, counterintuitively, despite a more ‘efficient’ wing.
Both are from Arrow III POH 1978 vs ~1995
Or it’s this simple that Piper wanted to have “better” performance figures and added 100rpm and some MP…
The early version appears by the font to be a direct extraction from Lycoming’s operator handbook while the later version adds the the phrase “as installed in”, which may have some relevance. However looking at the change in the numbers the connection to things like airframe inlet/filter restriction is not immediately clear to me.
Similarly the phrase “best power mixture” may also be relevant.
It any also be that Piper tested the engine in the airframe and created the second version themselves, highlighting errors or different undocumented environmental assumptions.
@Darkfixer I think you are right, but perhaps they had a stricter, more honest testing regime and had to add 100 rpm, to make the more honest figures look better. What does the performance table for the two years say at 7,500 feet 65%? FT at lower RPM and close to FT at the higher RPM
The 200 HP Arrow II was a 141 KTAS airplane, while the III, which in theory should be faster, was around 136 KTAS. Something must have happened in the regulations or testing regime.
Maybe this is the answer, they are both correct?
I was digging around on internet, and found this.
Some old Arrow owner that was asking the same question…
Not sure if it’s good to fly with 2700rpm in cruise and engine at 70% power…
But that’s another question.
I might have stated this before (…), but the free (and ad free) AircraftPower app for iPad, courtesy of Jim Petty, is a gem for those amongst us not having a direct % display.
This app permits the playing of RPM against (or with?) MP in a finger snap 
Thanks Dan!!
Didn’t know of that app, and it is quite similar to the Excel .jpg above.
I
