N3XH Phase 1 Flight Testing

[whee]

Good stuff Rod! Phase 1 flying can be so fun or a significant challenge. I enjoyed it but was glad when I was done.

133kts…I’m always jealous of you big engine guys.

Sounds like you’re getting some MP. I’d love to see 23” at 7500 feet.

[rodsmith]

I now have 19 hours on the plane. It is flying great, and I am now much more comfortable with it, especially landing. After 17 hours of break in, my oil usage is 1 qt in 10 hours. I'm afraid it won't get much better. Although, I tried to limit it, I spent too much time on the ground before getting in the air for the first flight. Finally started working through the test cards. In the test manual there is a matrix showing weight and CG for each test. I have completed all those at light weight/forward CG. I'll now do the tests requiring heavy weight/forward/CG. I have determined that clean stall is 46kt,
flaps 2 stall is 44kt, and flaps 4 is 41kt. I have calibrated my airspeed at several intervals between 50kt and 135kt. It is within 1kt of measured speed using 3 leg gps ground speed, except at 50kt where is reads 2 kt low. It took me 3 iterations to calibrate the fuel flow. This was a pain because our fuel pad is not level, so I would fill the tanks, then park it in my hangar and weigh the additional fuel I had to add from a can to get the tanks totally full. The initial K factor was quite a bit off, so fuel flows that I reported before were low. At 8000' 24/2200 my fuel flow is 15.5gph at 135kt. That is with the engine leaned to best power, 125 deg rich of peak. I did a test at what I think I will normally cruise at. 8000', 2100 rpm, 50 deg lean of peak. Fuel flow 9.9 gal hr and 125 kt. I didn't record the manifold pressure, I think it was about 21.5, full throttle. That extra 10kt comes at a huge cost! The lean assist feature in the G3X is great. As each cylinder peaks, the graphic changes from green to blue and you see a number showing how far below peak each cylinder is. I was thrilled to see that all 6 cylinders peaked within 15 deg. One of my biggest surprises was simulating a go around with full flaps. I thought it would require a large forward force on the stick until you adjusted the trim. With trim set for 52kt, when I went to full power and lifted the nose it didn't take much pressure on the stick to keep from over rotating. Biggest problem in that scenario is getting the flap setting reduced before you over speed them. I was surprised at the 46kt clean stall speed, expected it to be less. I am on the fence over installing VGs. Would like to see lower stall speeds. I'm thinking I should install them before completing the tests if I am going to. I think completing the tests should go pretty quickly now. I am thoroughly enjoying the testing, you really get to know your airplane.

[jaredyates]

Thank you for the update, all of that sounds totally in line with my experience, except for maybe the trim on go-around. The amount of pitch force needed during a go around will depend on CG. The more forward the cg, the more pitch trim is needed to reduce the stick force, so that may have been a factor in our differences of experience.

I'd be curious to know which fuel flow sensor you have and which k-value you started with and ended up on. I'm knee deep in fuel flow sensors at the moment and hope to have a lot of detailed info when I make it to the other side. But so far I'm 6 weeks into a fuel flow odyssey without any flying. I hope to have it resolved shortly so that I can also complete the condition inspection.

[rodsmith]

Thank you for the update, all of that sounds totally in line with my experience, except for maybe the trim on go-around. The amount of pitch force needed during a go around will depend on CG. The more forward the cg, the more pitch trim is needed to reduce the stick force, so that may have been a factor in our differences of experience.

Hi Jared, I was flying at 2150lbs and 15" cg when doing the go around testing.

I'd be curious to know which fuel flow sensor you have and which k-value you started with and ended up on. I'm knee deep in fuel flow sensors at the moment and hope to have a lot of detailed info when I make it to the other side. But so far I'm 6 weeks into a fuel flow odyssey without any flying. I hope to have it resolved shortly so that I can also complete the condition inspection.

I have the EI FT60 red cube. The default setting was 68000. I ended up at 66145.

[alaskabearhawk]

FWIW, I used the gold cube, FT-90. The fuel sensor product comparison on the EI web site says: "Up to 350 HP engines, engine driven fuel pumps only" Since I have a boost pump, I went with the gold cube. I don't know if that makes any difference in practice.

[jaredyates]

Thanks Rod, that is interesting. One of the selling points of the EI units is that they are supposed to be pre-calibrated so that you don't have to adjust the k-value but I'm glad you've got it sorted.

[svyolo]

I assumed that was the case as well. My EFI computer spits out a "red cube signal" that was waaayyyy way off for my engine monitor. It is probably within 10% now, but I won't get it tighter until I go somewhere for an hour or two.