180 Challenger Fuel burn

It looks like the book shows 9-10 gph for burn for cruise. I don't have fuel flow yet but plan on getting one. What numbers do you use for flight planning which would include start, taxi, and climb to a typical 5000-8000 ft cruise? What do you see in climb? Do you have a first hour number? and then a second hour number? Do you use something like 12-13 per hour for a 2 hour trip?

Thanks

Comments

  • edited July 17

    While it is an interesting exercise to calculate in advance fuel burn for taxi, climb, cruise, descent, and landing, in practical terms for the Cherokee 180, planning on 10 gal/hr has always worked for me.

    In my case, I rarely fly more than 3 hour legs or climb above 8000 feet. In my 1966 Cherokee 180 with O-360-A4A, I just plan on 10 gal per hour and always have at least 1 hour reserve after a 3 hour flight.

    Even after all the detailed planning, it really depends on routing, leaning technique, engine condition, gross weight, and winds aloft as to how much fuel will be required to get from point A to B. I rarely leave without full tanks unless weight and balance require less fuel.

    Try it for awhile and see how much your aircraft really consumes during the type of flying you actually do. Even if you “exactly” calculate how much fuel you will burn and you take on that much fuel plus legal reserves, other real time factors will determine if the time in your tanks are enough to reach your destination safely.

    Regards,

    Mike

  • edited July 17

    If this is a new-to-you plane, at the risk of insulting, might want to sand-bag the numbers a bit and go conservative until getting actual data. Would not hurt to plan on 12 - 13 gph at first and then see where the numbers actually lie after time. Always better to have more fuel in the tanks than expected rather than less (or none).


    Toward calculating climb burn rates and consumption after each hour of duration, the POH should have reasonably accurate numbers to calculate consumption. While good to know, am suspecting that after time this set of data will simply turn into too much background work and fall into the overthink category. Although, I do recall that my primary CFI had me to go through the drill of calculating out each hour's worth of fuel consumption.


    Agree with Mike's numbers and thoughts. Flew both a Cherokee 180 and an Archer where the fuel burn was about 10ghp from engine start to engine stop. Duration did not really seem to matter unless it was a super short hop or doing pattern work. Neither of those planes had a fuel flow meter and the gph was hand calculated from topping the tanks and dividing by the time (per Hobbs). Naturally, the 10gph number was from not running WOT in lower altitudes and looking for a lower power setting. IIRC, speed was usually in the 105 - 110 range.


    If taking shorter hops, might consider only filling to the tabs (if the tanks have them) rather than to full, especially on severe clear days with plenty of alternate fields within 20 minutes of the destination. Less weight translates to quicker climbs and less power necessary to get there.



    If the focus is to stretch out the tank as far as possible (within safety margins), focus should go to making sure rigging is in spec and there are no unnecessary drags. Toward unnecessary drags, IIRC wheel pants on the Archer made a difference of 5 - 7 knots in cruise. And toward trimming, watch the ball while in each phase of flight as having it off center can eat a knot or two. Too forward a CG will also eat a little bit of cruise speed, but just make sure weight placement remains in the envelope. And from what I recall of CG, as fuel burns, the arm moves forward and a zero fuel situation might put the arm too far forward of the envelope; but please trust the POH and not my memory on this 😉

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