If you're paying for it wet then you've already paid for the fuel in the hourly rate. In which case you're best served by going like the clappers to get there & back as quickly as you can.

Fly at the Full Throttle Height (ahem....altitude) for max continuous power in nil wind. If wind then work out the difference in TAS gained or lost by climbing or descending vs. the beneficial effect of more tailwind or less headwind.

If paying for it dry ie you buy all the fuel, then you need to compare the fuel consumption at different power settings vs the flight time to see how fuel consumption costs changes wrt to the cost for the aircraft using the same speeds.

Ah yes. Cost index 9999.

Economy cruise power < Performance cruise power < Maximum cruise power < Maximum rental power

:)

Going like the clappers
 

Irresponsible, and why FBO's always rent wet. If renters paid for fuel, with a lower overall rate for the a/c, some dolts would fly with pistons pinging, enjoying their extended time in the air. Pilots are responsible in the great majority, but taking a chance on the odd nitwit isn't worth it, believe me.

AF

What??? You ought to get current with modern engine management.

IMHO, a far bigger reason for wet rental is (a) lack of training on the Red Lever in the UK PPL syllabus, and (b) that most rental stuff is clapped out wreckage without accurate (or any) fuel flow instrumentation so there would be no way to invoice for the fuel separately.

Coming back to this - the thread was started with malice aforethought; I did the trip I had in mind this weekend - 8500 out, 9500 back. Fairly high OAT generally - 43C on ground / +20 cruise out, and 30/15 back.

Both ways the chart showed me to be above full throttle height, so I naievely expected to push the black lever fully forward and lean for max rpm.

Interestingly I had to keep the throttle some way back to keep the revs under the red line (cruise was at about 2650rpm, PA28-161). What did I miss?

POH showed 75% at full throttle/2700rpm. Was very thermic so didn't risk running at 2700 due to lack of wobble room...

9500' in a -161 at +20deg? My, you have done very well.

Same prop as the book? Same fuel? Similar weight (wont make much difference)?

Out of interest, what IAS did you manage?

Sheer bl00dy minded determination :} - 40+OAT at 2000, felt a lot more inside. If I hadn't had 3 pax plus a whole weekend and accomodation booked at the other end I'd have stayed inside with the house with the aircon on.. Damn silly weather to go flying. I'd have sold body parts for oxygen and the horses to get above it all...

IAS was around 95kts, TAS nearer 110 (according to the twiddlable sub-scale, not particularly accurate). Acceleration from climb was painful to say the least - just slightly less painful than the climb.

As far as I know standard prop - graph was from the aircraft's own POH, but it was a rental. Weight - MTOW less whatever we burned in the climb - probably around 30ltrs. Running on regular 100LL avgas..