Last fall I bought a 2010, D180-equipped RV-12 with about 150 hours TT. I've been flying it regularly since May with 100LL and had a couple experiences of very high fuel flow:
The first was in late May during straight and level cruise on a long cross country from Norcal to Socal. 5500ft/7660DA, 23.4"/5170rpm at 97kt IAS/110kts TAS, I noticed fuel flow indicated about 8GPH and stayed around that level for something like an hour. The level in the tank upon landing indicated much higher than planned fuel use as well so I think the reading was roughly accurate. On the second leg of the trip it started out normal (6-ish) and then climbed again to 7-8GPH for maybe a half hour. Then with no changes to the throttle or anything else it went down to 5.9GPH and stayed there.
On my return trip a couple days later I saw around 5.9-6 the entire way under similar conditions; speed, altitude, etc.
Earlier this month I experienced a related event. At 6000ft/7900DA, WOT 24"/4950rpm at 87kt IAS/98kt TAS climbing at about 400fpm I watched as fuel flow increased from 6GPH to 8.5 over the course of about a minute. Leveling out at about 7000ft/9000DA I pulled the throttle back about 2" and stayed at about 85kt IAS, 21.2"/4520rpm for several minutes but I never got below 6.8GPH.
This doesn't seem to happen when I'm down low around sea level. That same day, at 1400ft/2900DA, 26"/4820rpm at 101kt IAS / 105kt TAS I saw 4.9GPH indicated.
I believe the k-factor is relatively accurate based on what the fuel totalizer says compared to what I actually end up with in the tank, but to be honest I haven't kept accurate enough records to know precisely. I've weighed the carb floats and they're all within spec. The engine is from 2010 but has the 893114 fuel pump installed.
I believe the prop is pitched too coarse as I've never seen the tach above about 5200rpm, compared to the Sling2 I flew previously that would happily do >5500rpm WOT and could get up to 5800 when descending with throttle in. Perhaps prop pitch explains why my fuel economy is generally poor? I don't think it explains why the fuel flow would intermittently be so high, however.
Any thoughts?
The first was in late May during straight and level cruise on a long cross country from Norcal to Socal. 5500ft/7660DA, 23.4"/5170rpm at 97kt IAS/110kts TAS, I noticed fuel flow indicated about 8GPH and stayed around that level for something like an hour. The level in the tank upon landing indicated much higher than planned fuel use as well so I think the reading was roughly accurate. On the second leg of the trip it started out normal (6-ish) and then climbed again to 7-8GPH for maybe a half hour. Then with no changes to the throttle or anything else it went down to 5.9GPH and stayed there.
On my return trip a couple days later I saw around 5.9-6 the entire way under similar conditions; speed, altitude, etc.
Earlier this month I experienced a related event. At 6000ft/7900DA, WOT 24"/4950rpm at 87kt IAS/98kt TAS climbing at about 400fpm I watched as fuel flow increased from 6GPH to 8.5 over the course of about a minute. Leveling out at about 7000ft/9000DA I pulled the throttle back about 2" and stayed at about 85kt IAS, 21.2"/4520rpm for several minutes but I never got below 6.8GPH.
This doesn't seem to happen when I'm down low around sea level. That same day, at 1400ft/2900DA, 26"/4820rpm at 101kt IAS / 105kt TAS I saw 4.9GPH indicated.
I believe the k-factor is relatively accurate based on what the fuel totalizer says compared to what I actually end up with in the tank, but to be honest I haven't kept accurate enough records to know precisely. I've weighed the carb floats and they're all within spec. The engine is from 2010 but has the 893114 fuel pump installed.
I believe the prop is pitched too coarse as I've never seen the tach above about 5200rpm, compared to the Sling2 I flew previously that would happily do >5500rpm WOT and could get up to 5800 when descending with throttle in. Perhaps prop pitch explains why my fuel economy is generally poor? I don't think it explains why the fuel flow would intermittently be so high, however.
Any thoughts?