freightdog

Our runs were usually less than an hour flying time and especially in the socal area, it made no sense to going "balls to the wall" on the power, because by the time you were in cruise, you'd have to start pulling the power back to start stage cooling. As you said, you were getting 50gph and we were getting 18 gph, over a day's worth of flying at 5 days a week, that starts to add up at the end of the year. I think across the system we were saving $10,000/day with the reduces power settings. That's with about 40 PA31's operating.

jonnyjetprop

Ameriflight wrote the book on operating the PA-31. When I worked there, we were the largest operator by a wide margin.

TangoBar

It is low and lean, but the loss in speed isn't important for the kind of legs most of the PA-31s fly (100 to 150nm). FD is right- the extra power doesn't matter on short legs. Changing from 30" to 26" gives a speed difference of about 15kts TAS. At 30", a realistic fuel burn at that lean setting is 18gph. But at 26, most engines will lean down to 13gph. So comparing the fuel burn, running 2 engines at 30" will burn 36gph, or 3.6lb/min (36*6/60). Running at 26", you can expect a burn of 26gph or 2.6lb/min.

On a short leg, 75nm, I'd expect to see a 2 minute reduction in flight time: Climb to 9000 takes about 20nm. With 55nm remaining, and a 180 vs 165kt cruise, you can get a difference of 1.7min, of course excluding any vectoring or delays or adverse descent conditions caused by ATC. Savings? Well, you might save two gallons, even with the longer flight time, for $6. But it looks like your fixed costs are about $4.58/min, adding about $9 so I'd call the short leg a wash.

Even on long legs, there's not a huge difference. At 325nm, it looks like the time difference stretches out to about 10 minutes. Fuel savings might be $36 at $2.95/gal, but the extra flight time would add $46 in fixed costs, not to mention what your pax may think. However, if the fuel price goes up, now it makes a lot more sense. At $4/gal, the fuel savings are $50. $5/gal, and now it's over $60.

However... that's all no-wind calculations. Toss in a headwind of 40kts, and now that 165 TAS turns into 125 GS. Your 300nm remaining takes an extra 34 minutes- 144min versus 110. At the higher power setting the time would be 128min, so you'd save 16min and spend about $43 more on gas. However, that 16 minutes equates to about $73 in fixed costs... So at low fuel prices, bumping the power up seems to make sense. As fuel costs rise, the reduced power settings make more sense.

None of that takes into account the extra wear and stress of operating at the higher power settings, though. I don't have good info on what kind of a difference the power changes make on the MX side. I DO know that leaning to 25 rich of peak is a bad, bad idea. AMF tried this a year back or so, and it was trouble. Especially at 30", it leads to burned cylinder heads and cracked exhausts.

deadstick35

per side, right? Didn't you do trend monitoring ,too, for higher TBO's?

cpatterson19

Wow.....its amazing to see all these fuel saving techniques. What I am skeptical about is if it would cause engine damage to some extent. All these high manifold and fuel mixtures. Now you save the money in fuel and so on but at the end of the day do you end up spending more in mx is the question.

Just something to consider I guess......I really appreciate all these responses. I am learning alot on this type of aircraft so far. Keep em coming guys. Very much appreciated.

freightdog

We were required on any leg over 30 minutes, if i'm right, chieftain drivers jump in here, to do trend monitoring in the mx logbook.

freightdog

And we still are. It's always fun going on Airliners.net and seeing what airline these PA31's used to fly for.

freightdog

I was sitting in MMH one day and saw a passenger executive interior chieftain sitting on the ramp next to mine and asked the captain if I could take a look inside and see what it looked like with seats in it. He asked me what I was flying and I told him the cargo chieftain next to his. He asked me if I wanted a job.
Supposedly he was the chief pilot of the operation and his insurance guy said if they can find an Ameriflight pilot with chieftain time then the insurance rates would go down.

cpatterson19

Bet you got hired on the spot freightdog. A a significant amount of chieftain time and bring there insurance down......phew they struck gold.

freightdog

well, i refused the job and three months later found myself in a 99 then 6 months later found myself in a metro, so in hindsight glad i turned it down, but it was a nice airplane. I've seen a lot of nice Pa31s and panther conversions for sale with nice interior/avionics setups.