Return to Home Page
20 Jan 10 Today - 1.0 Total - 42.6
Finally got back into the air. We have the Spruce Creek 100 race coming up so I ran the course to practice what everyone calls the critical turn. The engine ran great and I trued about 187 for the course. During my MX downtime, I made a number of changes so this was also an evaluation flight for those changes.
Fly race route
Watch oil pressure and temp for changes
Check effectiveness of aileron tab
Compare actual to indicated fuel calculation
Check for NW shimmy
Test changes to starter system
Check RPM to see if governor adjustment is correct
The change to the fuel computer was almost exactly twice too much. I had changed the computer K factor bias from 680 to 749 revolutions per .01 gallons. Now I'm going to readjust it to 713 and test fly again.
The oil leak that had "worsened" hadn't actually worsened. I had done zero G flight and the air-oil separator filled up and over flowed. I changed the oil from mineral oil to Exxon Elite 20W50 which is a semi-synthetic oil. I did an engine run to check for oil leaks and then closed up the cowling. During flight, the oil pressure was up slightly to 80 PSI and the oil temp was the same as before. The oil temp got up to 194 today, but that was because I was running WOT at 1000' MSL and 2650 RPM. Number 3 CHT went to 420, but no higher. The other three cylinders are within 7 degrees of one another and were running about 370. No post flight indication of oil leak.
I taped a wedge under the left aileron to try to correct for the heavy wing, but to little avail. I still had to hold left stick pressure, so I'm ramping up from a 4 inch wide wedge to one foot. I'll test fly it tomorrow AM.
The ram air intake was readjusted and seems to be staying in place now.
I tightened the nose wheel breakout force to about 28#, but still got significant shimmy during landing roll. Sure wish Van's would work on a solution for that.
Of course, the bulk of my MX work had to do with the electrical system. I changed out several wires for heavier ones - the alternator to #4 and the starter to #2. I changed the routing of the starter cables so I have a positive means to cut off power to the starter. Additionally, I added a starter engaged light to indicate when power is being supplied to the starter. All of those changes are working as advertised, but I still have an anomaly in the electrical system I can't figure out and it appears to be worsening. I have two points where I check amperage - a Hall effect device on the alternator B lead to sense the load being put on the alternator and a shunt on the wire from the aft standby battery. Occasionally, my bus voltage will drop and simultaneous with the drop the standby battery amps go negative and the alternator amps drop. I had similar indications before my wiring changes - although not as extreme. I'm not sure if I have a short somewhere or if the alternator is faulty. I doubt the alternator is the problem - it is likely an installation error. But, so far, I'm stumped. I was really hoping to not have an electrical issue like this because they are so difficult to track down. But, guess I'll have to get out my detective gear.
I installed the map storage panels and I'll put them to good use on Friday. I also finally installed the stick boots for both sticks. I sure hope I don't have to get under the floor again any time soon because it is a real hassle to pull everything out.
21 Jan 10 Today - 1.8 Total - 44.4
I learn more each time I fly the airplane! And I built it! You'd think I understood everything about it. Well, 99.5% I do understand, but there is the elusive bit that stumps me occasionally.
I got in two flights today to fine tune things before my first long flight. Very rough at low altitude with winds from 190/74 at 1000' and 205/25 at 2000'. Very odd. Tomorrow I'm flying to Atlanta to pick up my son, it it's the first opportunity to get stuck out somewhere without tools and equipment.
Today, the first flight was to check several things. I had adjusted the fuel computer K factor and needed to see if it was correct. I wanted to check AP ops again at low altitude in prep for the upcoming race. I also wanted to check the VOR reception and check the voltage on the bus with the standby battery turned off. I wanted to see if the bus voltage would increase or become less erratic with the standby battery off. I had also added a 12 inch wedge under the left aileron to attempt to correct for the heavy wing problem. I expected the wedge to adversely affect the top speed.
Results: The fuel computer thought we burned 10.2 gallons. Actual burn was 8.07, so another adjustment was needed. The AP tracked the GPS with little problem. The altitude hold was still a little off. VOR reception on the SL30 was good. The surprise of the flight was the electrical. I originally designed the electrical system such that the bus tie would normally be off unless needed in the event of an alternator and main battery failure. I've been flying with the bus tie open and the standby bus and standby battery are powered/charged from the main bus through a Schottky diode to prevent reverse power flow. I've always had voltage at only 13.5 or so and recently some very low voltage anomalies. Today when I turned off the standby after engine start, the bus voltage plunged. I tried it several time with the same result. Going through the diagrams in my mind, I decided that maybe the Schottky diode was reversed. I turned on the bus tie and - bingo - the bus voltage shot up to 14 volts and stayed there the rest of the day. On the next engine start, the engine spun over much much quicker and the entire electrical system seemed to be working more correctly - that is, the voltage was solid at 14 and amps from the alternator and on the standby battery made sense (17 or so on the alternator and 1/2 on the standby battery). Adding up the amps need by the electrical devices turned on approximately match the alternator load and the standby battery was working only to hold the contactor closed (1 amp). The indication looked right - as opposed to the reading I'd been getting before. So, I'll fly the airplane with the bus tie closed and retrace the diagrams to figure out what is happening and why. Finally, the aileron wedge was overkill. With such a large wedge, the airplane wanted to roll left. The top speed was absolutely unaffected by the wedge.
So, after changing the FC K factor and entering the race route in the GPS and cutting down the size of the aileron wedge, I was off to see what resulted. I also wanted to try 24 square to check IAS and TAS and FF.
Results: The AP tracked the GPS route very well and held altitude within about 50 feet. Not bad! The 9.5" aileron wedge was about right - maybe slightly too much (I cut it down after the flight to 8.9"). It flew wings level hands off. The voltage and amps were right on where they should be. While cruising at 2000' MSL on AP, I set RPM at 2400 and MP at 25 and with peak power EGTs I got 152 KIAS, 159 KTAS and 10.1 GPH. This time the fuel computer thought we burned 10.8 while the actual was 11.9, so I overcorrected. I adjusted the computer AD value again and I'll get very good readings and comparisons on the trip to ATL.
Engine Readings from today
First Flight - 2000' - WOT - 2670 RPM - 28.1" MP - 188 KTAS
Second Flight - 2000' - 25" MP - 2400 RPM - 159 KTAS
It looks like I need to add an air dam in front of the #2 cylinder so as to bring it's CHT to match #1 and #4. Then all I have to work on is getting #3 down by 40 degrees. I made changes to the lower baffling on #3 to allow more airflow, but that seemed to make little or no difference in CHT. The oil pressure and oil temps are right on target.
30 Jan 10 Today - 1.4 Total - 53.4 Fuel Burn 12.3 L 6.9 R 5.4 Fuel Comp 13.0
Interesting flight today. Our intention was to fly to Panama City, but weather turned us around near Ocala. It began raining shortly after takeoff at 7FL6 and rained until we returned. That turned out to be a revealing situation.
During flight, the engine began running a bit rough so we closed the ram air and used filtered air. Note to self - when approaching rain, switch to filtered air. Also, we had water dripping in a several locations. It appears water is getting in along the canopy to windscreen seal and running down the frame and dripping in at the canopy rollers. Also, this was my second RCP sortie and it allowed me to discover where there are air/water leaks in the back. The canopy skirt bows out a bit in flight which allows air (and water) to blow in under the skirt - on both sides. There is still a bit of air coming in from the aft canopy, so I'll add a seal to block it. Then, after the plane sat for a couple of hours, I discovered water dripping along the centerline seam, but there was no water running down to that low point. Water got inside the airplane and settled in the low spot under the floor. Fortunately, my floor panels are removable, so drying it out is fairly straight forward. It may have entered at the main gear upper fairings.
The rain also peeled some of the prop paint off and pitted the front cowl and nose wheel fairing fiberglass. I'll need to fill those spots and refinish them. I also need to check all other forward facing fiberglass for pitting.
So, before next flight in rain:
Add seal to hat shelf and canopy skirt
Fill pitted fiberglass and refinish
Seal main gear fairings
Today's Engine Readings - About 2800' MSL - 150 KIAS - 165 KTAS