europaxs wrote:
Does LOP make such a difference?
Compared to what ? Full rich – yeah, big difference, 100° ROP – about 15% less.
5.7 gph is a very small engine.
Peak EGT is about 30% better SFC than full rich.
Flyer59 wrote:
the intention was not do an VFR or IFR fuel calculation. Just to find out how long the airplane could be in the air, from full to dry. A realistic range for the SR22 is 900-1000 NM, depending on power setting.
That is the question if you calculate like that. I was going by over the thumb for too long initially until I once had time and really started to calculate this stuff out. But even if you calculate range to dry, you at least need to take the airplane up to the level from where you go, otherwise the whole exercise is mute. And you might be surprised that the actual feasible range of your SR22 might be more than you think.
And of course you can calculate like that for comparison’s sake but then one needs to know how it’s done so others can do the same.
If I were to do that, Climb to FL100 and then fly on with max range setting, I’d run out of fuel after 860 NM and 6:30 hrs.
With a realistic plan it’s 770 NM and 5:40. So the difference is 90 NM and 50 minutes.
Longest flight I’ve done was just under 5 hours with a remaining fuel of 8 USG.
europaxs wrote:
I don’t know that much about Lycos, but you quote 5,7 GPH @ 55% LOP. Which engine is this? TigerFlyer quotes 35 liters=9,25GPH for 60% and this is a 180hp engine AFAIK. Does LOP make such a difference?
An underlying issue is injected versus carburated Lycomings. Fuel distribution on carburated Lycomings does not allow leaning to the same fidelity, and they burn more fuel as a result. The better leaning capability of injected Lycomings is the only thing I prefer about them relative to carb engines, but it is definitely better.
I think you can throttle and lean an injected O-320 (150 or 160 HP) to 5.7 gph, and maybe even an O-360 (180 HP). In a very efficient airframe like the RV-4 you’re still doing 150 kts TAS.
@europaxs
I actually plan with this FF of 35 lph and depends on altitude. So I calculate always on the safe side. Running out of fuel is the worst error of a pilot. I don’t like fuellevel less than 20-25 liters total.
OK well using this system of calculation.
MTOW, ISA all the way. FL410. No wind. Fuel to bottom of tabs (POH but could load more) – 2580lbs. 2000fpm descent. Max cruise thrust. No reserve.
You say to the bottom of the tabs. So what would a regular calculation with reserves look like if you fill to tops?
You say to the bottom of the tabs. So what would a regular calculation with reserves look like if you fill to tops?
You lose about 250nm versus the other calculation with 600lb reserve but filling tanks to the brim. With my preferred more comfortable 800lbs you lose another 130nm. So a clean 1000nm. These calcs all include allowing for 10 minutes holding and a 30nm approach at low alt in addition to the reserve.
Piper Dakota: I have found absolute range is about 900 NM (with the engine quitting on rollout).
The Dakota has a thirsty carburetted O-540, spam can aerodynamics and fixed gear, so is not designed for range. I happened to fly EKRK-ENHA round trip, both ways without any wind component, and all the cruising was at FL 100 and on the same tank (the other was used for climb and descent). I cruised at 52% power giving 120 KTAS, on 9,0 gph. Topping the tanks after returning showed I had landed with 18 gals in the tanks, or 2,0 hrs of economy cruise.
So useful range is max 780 NM, if throttled back, leaned carefully in all flight phases, enduring 6½ hrs in the old Piper seat and landing with 60 minutes of slow cruise endurance.
But the plane needs a pilot, and if that is me, max endurance is around 4 hrs, 3 hrs is better. In which case TAS can increase to 135 KT, giving a practical range of around 4-500 NM +/÷ wind.
