Flight 8. Jan 3, 2016.

Woohoo, fuel vent leak fixed.

Preflight:

Added 1/2 quart of oil. Also found the source of my fuel smell. Last night when the FBO filled the tanks, they filled them so full that fuel was displaced when I reinserted the fuel caps (thats full!). However, this also caused more fuel than normal to burp out the fuel vents overnight. When doing the pre-flight today, I noticed fuel staining on the exterior fuselage side skin, below the root/leading edge of the wing on the right side. This coincided with the area where the fuel vent entered the fuselage. I pulled the wing root fairing expecting to find fuel staining inside the wing root area on the fuselage skin above where I saw the stains. However, there were no leaks on the outside of the fuse in the wing root area; (see clean picture above) it seemed to be coming from the fuselage skin seam between the side skin and the floor skin.

This led me to climb into the cabin and stick my head up under the panel with a flashlight and inspect the fuel vent on the inboard side of the fuse wall. Lo and behold there was some evidence of weeping fuel from the flare fitting where the 90 degree elbow attaches to the fuel vent tube. There are 4 of these vent tube connections inside the fuselage, and it turns out I hadn’t fully tightened any of the 4! This is probably the biggest mistake I have found in the build to date, and is a big blow to confidence to find 4 vent connections only finger tight (makes you wonder where else you missed something no matter how careful you try to be).

I tightened the one that was leaking at the wing root on the right side and its corresponding brother on the left side (connection was loose, and only minor evidence of fuel staining there). I also attempted to tighten the other two connections near the firewall where they exit the floor to the fuel vents. Harry helped me by holding a 11/16 wrench on the outside of the fuel vents while I tightened the nuts on the inside. Once the bulkhead fitting was tight, I was then able to tighten the flare fitting on each side.

Flight 8:

I filed for a 1 hour flight out of HEF (instead of my normal 1:30) just to check if the fuel smell issue was resolved. I’m happy to report that the issue seems to be cleared up. I’ll watch this as we go forward, but I’m 90% sure the issue is fixed.

During the flight I also managed some 65% and 75% cruise at 7,500. And also some slow flight at 70 KIAS and 80 KIAS flaps up. I did lots of left and right turns with 30 and 45 degrees bank.

Flight Data

Flight Map

1.5 hours engine, 1.5 hours electrical, 11.1/12.5 cumulative.

Post flight:

14 gallons dipstick on right tank. 10 gallons remaining dipstick on left tank. Fuel truck added 5 gallons to the right tank, and 9.9 gallons to the left tank. Dipstick then measured 20 gallons on the left tank, and 20.5 gallons on the right tank. I know these don’t add up perfectly, but such is the precision of dipsticking with 2 gallon intervals.

Also noticed during this flight I forgot to reset the fuel totalizer so the following measurement also includes the fuel burn from flight 7 (17.9 gallons). Fuel totalizer = 34.1 used, 25.8 remaining. Compensating for the 17.9 gallons from flight 7, leaves a totalizer measurement for this flight of: 34.1-17.9=16.2.

I forgot to download the flight data from the G3X so I will post that here later.

Oh, and I polished the top of the right wing the other day. This is what it looks like when the wing top is polished and the fuselage still looks crappy:

Flight #7. Jan 2, 2016.

I preheated the engine for 1:20 and saw the oil temps increase from 41F to 52F. CHTs from 40F to 47F.

Today I flew 1.8 hours and tested a variety of level flight cruise power conditions. This is without wheel pants and without gear leg fairings (worth a reported 15 knots extra) and without a calibrated airspeed probe.

146 KTAS @ 2500 RPM @ 18.5″ MAP @ 12,000 feet MSL

148 KTAS @ 2600 RPM @ 18.5″ MAP @ 12,000 feet MSL

Descended to 8000 MSL

156 KTAS @ 2660 RPM @ 22″ MAP @ 8,000 feet MSL

This is about 180 MPH.

During the descent, I saw 177 KTAS (Vne=200 KTAS). This is about 204 MPH.

Flight Data

Flight Map

Again I noticed the fuel smell in the cabin on two separate times for just a few minutes. The first time was on climbout, and the 2nd time was during a left 180 degree turn. After reading quite a bit about possible sources for this smell, I learned on VAF that sometimes with full tanks the fuel vents can burp a few drops of fuel on the belly. The first time I smelled the gas on this flight was with both tanks full just after takeoff. The 2nd time I smelled it in the turn was approximately 45 minutes later, and I’m not sure if I was still on the first tank (leaving the 2nd tank still full to drip in a turn). Apparently, if the drips hit the belly, the fumes can get sucked into the flap pushrod holes due to the lower cabin pressure. I’m still not giving up on searching for weeping fittings, but this theory may also have some merit.

I performed a few stalls clean during this flight. I let these stalls get just a bit sharper and deeper than previous flight’s stalls, but I’d like to get spin training before I push this any further.

Most annoyingly, the Garmin G3x MFD rebooted in flight twice. This is almost certainly a software bug and it happened during me fiddling with the knobs and buttons and the same sequence of button presses and knobs caused it to happen again after the first reboot. All I had to do was: Press NRST. Defaults to rightmost page: Airspace. Spin the knob rapidly to the left (trying to get to NRST Airports). Boom: Instant reboot. This “feature” might really piss you off if you needed to find the nearest airport in a hurry! I’ll need to notify Garmin and see if there is a software update.

I did not notice any fuel pressure dips during this flight, but post flight looking at the data, I see one did occur dropping to 20.4 PSI. I’ll need to read up on this and determine if this is normal.

1.7 hours engine, 1.8 hours electrical. 9.6/11 cumulative.

Post flight:

Removed top and bottom cowl. Wiped brake reservoir overflow (this seems to be decreasing).

Right tank dipstick: 8 gallons. Left tank dipstick: 16 gallons.Fuel totalizer used 17.9 gallons (24.1 remaining). Right tank fuel truck added 13.35 gallons. Left tank fuel truck added 4.75 gallons. Reset totalizer. Set 42 gallons onboard.

Jan 1, 2016. Taped the hole in the lower cowl nose gear leg area to help prevent pressurization of the lower cowl area.

Prior to the flight, I installed 2 Reiff 100W oil sump heater pads (one on each side of the sump at the rear of the engine) and the thermostat’s ceramic cube on the back of the engine oil sump (in the center rear). I ran the heater for less than an hour this morning and saw the oil temp and CHTs rise a few degrees from 50 to 53. It looks like it is working, and this is plenty warm for starting.

Today I flew for 1.7 hours. I did 2 stalls clean, 2 stalls at 15 deg flap, 2 stalls at 30 deg flap, and 2 stalls at 45 deg flap. Stalls at 45 deg flap have a tendency to drop the right wing slightly.

I did at least two climbs from 4,000 to 10,000 feet MSL under various RPM settings and power settings.

I tested the cabin heater valve. It heats but not a whole bunch.

Noticed a fuel vapor smell in the cabin during initial climb (this smells different from an exhaust smell). This has been a recurring event and I am trying my best to locate the source. Since I sealed the remaining holes in the firewall prior to this flight, it doesn’t seem like it is coming from the engine compartment (and there are no fuel leaks in the firewall forward area that I can find. Bob says fuel vapor can frequently can come from the wing root areas and into the cabin around the aileron pushrod holes (there is positive pressure in the wings and it forces air into the cabin under the seat pans. I pulled the wing root fairings (external) several flight ago and found no evidence of fuel leaks at the wing root connections. Other ways can be if the fuel tank is leaking at the back baffle and running down the inside lower surface of the wing to the wing root area. From there if it is more than a drop or two, it can run into the fuselage cabin floor since the cabin floor underlaps the wing for a few inches (I think). I can’t find any evidence of this happening. I plan to pull the fuel selector valve covers and the fuel pump cover and look for evidence of drips around those connections. The smell doesn’t last for long and is lessened when I open the cabin fresh air vents (in rush air may help pressurize the cabin slightly).

I also noticed occasional fuel pressure dips. You can see the two dips in green here (dropped to about 18 PSI):

Oil temp was also fairly cold on this flight (150’s & 160’s). I’d prefer to see 180 and I already have 1/4 of the oil cooler air inlet taped over.

Full data from flight

Map from flight

1.6 hours engine time. 1.7 hours electrical time.  7.9/9.2 cumulative.

Post flight:

Post flight fueling: 8.7 gals right tank from fuel truck. 10.6 gals left tank from fuel truck. Right tank 20 gals dipstick. Left tank 21 gals dipstick.

Wiped overflow on brake fluid reservoir.

Put foil tape on 4 holes in the lower fuselage surface where the upper gear intersection fairings mount (but are not currently installed) in an attempt to block any vapor entry in this location.

Added 0.25 quarts of oil to bring the oil above 6 quarts.