Urs_Wildermuth Posted May 25, 2012 Report Share Posted May 25, 2012 Hi there, question for you out there. In the POH of the "C" Model, they give a cruise setting with 1800 RPM which is supposed to bring the best range, however at the cost of massive speed penalty. For the C, they write of speeds around 100 kts TAS at 5-6 GPH, for the E about 120 kts TAS at 1900 RPM and a similar flow. Has any of you ever tried that? Does it work? Does it make sense? If I look at the POH and extrapolate, it may well mean you can get about 60-100 NM more range out of these planes, that is around 700 NM instead of about 600 in the case of the C model. I don't have computer models for the E yet as mine is a "C". A friend is thinking of buying an "E" and the previous owner sais he flies it like that, but I'd like to hear from you guys rather than a seller. I somehow question if this makes any sense. On a 500 NM trip you'd save about 3 USG at the cost of 1 hour additional flight time. IMHO it appears as if the money saved for avgas will be eaten up and beyond by the fixed costs share resulting from 1 hour additional time. And I also do wonder if it makes sense to sit on this plane for 6-7 hours if not absolutely necessary. Your take on this is highly appreciated. Best regards Urs Quote Link to comment Share on other sites More sharing options...
gregwatts Posted May 25, 2012 Report Share Posted May 25, 2012 Life is short....fly fast! Roy Lopresti Quote Link to comment Share on other sites More sharing options...
lamont337 Posted May 25, 2012 Report Share Posted May 25, 2012 Don't quote me, but i believe those numbers relate to L/Dmax, and there is probably a certification reason that requires the manufacturer to find those numbers during testing. If you have the same manual I do, you'll notice those numbers are also about the same as your best glide speed. You are right though, the fixed costs of operating the engine will most likely eat up any savings in fuel and I can only think of a few reasons to fly at those speeds, such as being dangerously low on fuel or sightseeing. I vaguely remember some aircraft/engine combos developing problems because they were ran like this during search and rescue/loitering operations, but the specifics escape me at the moment. I guess the real question is, why would a guy regularly fly such a fast airplane so slow? Quote Link to comment Share on other sites More sharing options...
Urs_Wildermuth Posted May 25, 2012 Author Report Share Posted May 25, 2012 He was right. He would think again today when Avgas prices here in Europe are between $10 and $15 per USG. Quote Link to comment Share on other sites More sharing options...
Urs_Wildermuth Posted May 25, 2012 Author Report Share Posted May 25, 2012 Quote: lamont337 Don't quote me, but i believe those numbers relate to L/Dmax, and there is probably a certification reason that requires the manufacturer to find those numbers during testing. If you have the same manual I do, you'll notice those numbers are also about the same as your best glide speed. You are right though, the fixed costs of operating the engine will most likely eat up any savings in fuel and I can only think of a few reasons to fly at those speeds, such as being dangerously low on fuel or sightseeing. I vaguely remember some aircraft/engine combos developing problems because they were ran like this during search and rescue/loitering operations, but the specifics escape me at the moment. I guess the real question is, why would a guy regularly fly such a fast airplane so slow? Quote Link to comment Share on other sites More sharing options...
moodychief Posted May 25, 2012 Report Share Posted May 25, 2012 I have a C model and to tell you the truth I would have to land after 4 1/2 hours max (kidney/bladder range) so I might as well fly fast. I have played around with 19 in/1950 rpm and got 105 knots. I wasn't able to check the fuel burn as my tanks were 3/4 full on takeoff. Quote Link to comment Share on other sites More sharing options...
carusoam Posted May 26, 2012 Report Share Posted May 26, 2012 Search for the guy who flew from the pacific coast to Florida in a Mooney, nonstop. Efficiency is the only reason for this type of flying. If you are trying to build flight hours, this would be efficient. Driving a diesel powered VW would be more efficient and even less fun... Flying LOP increases efficiency with an acceptable cut in speed for the E, LOP is probably not possible for the C. Watch CHT and oil T. They may go to the low end of their ranges. You may be operating in an area that few have been operating long term in. I did it once for about an hour seeing if I could ridge soar with a low power setting. Fun, but not the way I would want to have to fly. I did not have 4CHTs or FF data either in the old bird. -a- Quote Link to comment Share on other sites More sharing options...
ahe Posted May 27, 2012 Report Share Posted May 27, 2012 I have a '59 A model with 49 gal fuel. The manual says that on endurance it will fly 6.3 gph 120kt 2200rpm/16.5" I have flown 700nm trips with 115kt 6.5gph average over the whole trip including start/landing. It is slow, but still faster than landing for fuel after 500nm. With that in mind, and the fuel prices in Europe (13$/gal) it makes sense for me. I should say that i verifyed the fuel flow in endurance configuration before i did any 500nm+ trip. I did it by emptied my rear tank (14 gal on 2:15) - i have no fuel flow meter etc. Best regards Quote Link to comment Share on other sites More sharing options...
Vref Posted May 27, 2012 Report Share Posted May 27, 2012 Although these low rpm setting may look like giving a longer range in practice is not. On most flight there is headwind where flying at low speed may actually reduce your range. Jose Quote Link to comment Share on other sites More sharing options...
WardHolbrook Posted May 27, 2012 Report Share Posted May 27, 2012 Quote: Vref Although these low rpm setting may look like giving a longer range in practice is not. On most flight there is headwind where flying at low speed may actually reduce your range. Jose Quote Link to comment Share on other sites More sharing options...
ahe Posted May 28, 2012 Report Share Posted May 28, 2012 You have a point about headwind, but anyways, headwind or not, it would not be possible in my A model in any normal cruise settings to fly 700nm!. I assume you would need a lot of headwind to offset the fuel- and timesavings (no landings for tanking, less time used). All this get's very academic - i do not fly very academically, neither is my very simple fuel "management". 30m left tank - taxi, runup, start, climb to cruise altitude and a cruising30m right tankapproximately 2.15 empty rear tank1h left tank1h right tank1h+ empty left tank Because i start on left tank i now know that the time i just have flown on left tank (1h+)is LESS than i have in right tank, so i have at least have the same time + some more in right - if i am not very close to my destination airport now, i would fly to the alternative (closer) airport. In reality i have never tried to empty the left tank, when i decent for landing i change to the fullest tank with 1h+ in. I must still be young - i do not need to "hitting the john" for a fligt of 6.5 hours, and if i did i would do as the gliders do all the time. I have flown both in the US and the Europe - remember that here (in Europe) landing and fueling in different countries is more time consuming and expensive than in the US. I do not want to waste time and money if not absolutely neccecary!. Best regards Quote Link to comment Share on other sites More sharing options...
aviatoreb Posted May 28, 2012 Report Share Posted May 28, 2012 Quote: carusoam Driving a diesel powered VW would be more efficient and even less fun... Quote Link to comment Share on other sites More sharing options...
xftrplt Posted May 28, 2012 Report Share Posted May 28, 2012 Deleted. Quote Link to comment Share on other sites More sharing options...
rbridges Posted May 29, 2012 Report Share Posted May 29, 2012 Quote: Vref Although these low rpm setting may look like giving a longer range in practice is not. On most flight there is headwind where flying at low speed may actually reduce your range. Jose Quote Link to comment Share on other sites More sharing options...
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