Sunday, June 10, 2012

Phase 1 Follies -- Part I

As crappy as yesterday was in terms of operating and diagnosing the performance of a new airplane, today was much different as some of the classiest people on Planet RV stepped forward with great assistance.

Unbeknownst to me, Stein Bruch stopped by the hangar -- did I mention he's letting me use his hangar during Phase 1 testing? -- and gave the plane a pretty complete onceover. He reported that the left magneto is fine, thought the plane was well built, and identified a few areas that might contribute to the heavy wing Tom Berge noted on the test flight a week ago. One was a twist in the elevator alignment, and the other was a slight flap misalignment from left to right.

There's nothing to be done about the former, but the latter can be adjusted. But first I'll fly and see the extent to which the wing is heavy. I adjusted the aileron alignment the other day. I didn't notice a heavy wing on that first flight I made, but I was busy with other stuff.

Stein also noted -- correctly -- that the throttle cable is very stiff. We looked for kinks -- Stein stopped by on his way home from work, too -- in it but didn't find anything. So I'm going to try another cable. Question: Who's got another cable they'd like to let me try out?

As I was driving down to Lakeville, Alex Peterson called (actually, he called earlier and I called him back) while he was driving up north. He offered to fly down Monday evening and look at the RPM problem. But, he said, "you may not have a problem. The engine may not be performing as poorly as you think." Indeed, I do want to get the RPM indicator cross-checked for accuracy.

We also talked about the manifold pressure problem and he suspected a bad gauge and explained to me what it should be reading.

What was especially illuminating was when Alex talked about the noises I heard. He indicated that when the wind is blowing from a certain direction, he gets a "popping" sound from the air vent ports on the side of the fuselage. What he described fit perfectly with what I was hearing yesterday and probably wasn't backfiring at all.

Anyway, I tackled the manifold pressure problem first in an all day/night session this afternoon/tonight and found that I had failed to properly configure the engine monitor. I was supposed to enter some code that was on the Grand Rapids EIS 4000 manifold pressure box into the engine monitor. Once I did that, the MP indication on the monitor with the engine off read the barometric pressure indicated when I set the barometer to zero. That was a big one out of the way and means the manifold pressure problem I had was not an engine problem. Oh, I also blew out the manifold pressure lines and they were fine.

I also realized that the fuel pressure alarm that went off while climbing out of the pattern yesterday was not a fuel pressure alarm at all; it was a fuel flow alarm. I had configured the engine monitor to indicate an alarm whenever the fuel flow exceeded 19 gph. It was supposed to alert me to a leak in the system, but the FloScan module hasn't been calibrated yet so it was a worthless alarm. So, again, what I thought was an engine problem was not.

I took the filtered air box off and looked at the throttle plate to confirm that it opens complete. It does. Reinstalled the airbox and moved on.

I wanted to remove the fuel filter on the high pressure fuel pump but I didn't get around to it. However, I did repeat the fuel flow test by running the boost pump and pumping fuel into a five-gallon container at the fuel servo. It came out to about 43 gallons per hour, which pretty well matched the FloScan fuel flow indicator on the engine monitor. So all was good there. That number is actually better than it was when I ran a similar test a summer ago.

As far as the oil, I'm pretty sure now the oil was coming out of the breather tube, so I wiped up what I could and reinstalled the cowling, pulled the plane out, and hooked up my laptop to the engine monitor serial output, started the engine and went about seeing where things stood.

Here are some of the things I found, in no order of importance:

-- The Lightspeed tach reading and the manifold tach reading matched. I got about a 100 RPM drop when operating only on the mag. That's about 40 more than yesterday. I really should've leaned out the engine and cleaned some carbon, but I didn't. I got about a 20 RPM drop operating only on the the Lightspeed.
-- On runup, the static RPM reading was about 2020. About 120 more than I got yesterday,and about 90 less than what Tom Berge recorded last Sunday.
-- Fuel pressure was reading 36 with the boost pump on.
-- I took the runway and accelerated. I did not hear the infamous "noises" and developed 2105 indicated RPM (and increasing) when I pulled power when I reached 41 knots. It appeared to accelerate fine. It was a lovely night. If not for the operating limitations,I might have considered going flying.
-- On that run, EGTs were: 1143/1086/1062/1094
Cylinder temps were: 354/318/325/320
Outside air temperature: 80
Fuel flow: 12.9 GPH
Manifold pressure: 28.5
Fuel pressure: 36
Oil pressure: 81
Oil temp: 149
Total time from throttle forward to throttle back: 9 seconds

I taxied off the runway and back and tried it again. On the next run, I was at 2120 RPM when I shut down at 43 knots.

-- On that run, EGTs were: 1131/1085/1072/1103
Cylinder temps were: 346/302/313/315
Outside air temperature: 80
Fuel flow: 17.1 GPH
Manifold pressure: 28.4
Fuel pressure: 36
Oil pressure: 81
Oil temp: 164
Total time from throttle forward to throttle back: 10 seconds

During taxi back to the hangar:
Fuel flow: 5.7
Fuel pressure: 38 (left the boost pump on)
Manifold pressure: 13.3
It took 846 RPM to feed 14 volts (strobes, all lights, and all systems on)

I did try to use the GRT-recommended system of checking the RPM by trying to "freeze" the propeller at 600 RPM with a 60hz (or is it Mz, I forget) light in the background and I could not get it to do that at any number of RPM settings. I'll have to find an optical tachometer somewhere.

Total testing time: 21 minutes 33 seconds.

I did not notice any immediate pools of oil in the bottom cowling or around the breather tube.

I feel pretty good about these numbers. The static RPM is still a little low, but as I said, we need to doublecheck the tach readings.

If anyone wants the spreadsheet with all of the numbers, just holler.

12 comments:

  1. I'm working on both my A&P and an rv7a. I haven't finished either so my advice may not count for much. However it sure sounds to me you have figured out all of your problems. The only other thing I might do is to check cylinder compressions but I highly doubt that is a problem. I have an O-360 on a Grumman tiger and your fuel flow full rich is in the same ballpark as mine. You have confirmed the air is open and unrestricted so your fuel / air is probably ok. Only thing left is ignition and mechanical (rings, valves, etc). You seem to feel good about the ignition. I don't know if there is any way to check timing on your non mag system. I installed a new set of mags once and after 25 hours the timing settled in about a degree too far advanced wihich contributed to me glazing a cylinder. Your rpm drops seem in spec. Your engine data looks ok. Would be good to find someone else with the same prop and engine to see if ground max rpm (not rolling and little wind) is close or not. Yes I would check the rpm as you suggest but it is likely your measurements now are right.

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  2. If Alex is able to fly down on Monday, he's going to bring a timing light for the Lightspeed. There's a timing mark on the back of the ring gear for reference.

    In terms of other examples, a friend on Van's Air Force was out yesterday morning his and recorded about 100 more RPM at 70 degrees (I was at 80). He got about 2250 on the roll.

    I'm pretty sure I could have gotten a little more RPM out of things by leaning a bit. Density altitude around here yesterday was well over 3500, I believe.

    The idea of glazing a cylinder has been on my mind as I've been out and about on taxiing missions. Scares the hell out of me. I've tried to keep CHTs below 350.

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  3. Regarding "freezing the prop" to check RPM, florescent lights flash 120 times per second, or 7200 times per minute. The prop should appear to stand still every time the number of blades per minute divides evenly into 7200. (Example: a 2-blade prop at 1800 RPM = 3600 blades per minute, and 3600 divides into 7200 with no remainder.) 600 rpm should work too: 2 x 600 = 1200 and 7200 / 1200 = 6. All the ambient light has to be florescent for this to work. Incandescent light and sunlight won't do this.

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  4. Your cylinder temps are fine and I won't be afraid of glazing. My fuel flow on the tiger full throttle and full rich is at most around 13 gph. 17 sounded high but not sure you have really calibrated that either. Don't lean the new engine too much just to try to get more power on takeoff unless you live in high altitude areas. Easier on the exhaust valves.

    Ellis

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  5. Progress! What was that thing you said, "90% done, 90% to go"? I kid.

    Glad you're able to get a few things off the concern list.

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  6. Brian C(hydroguy)June 10, 2012 at 11:00 AM

    go launch that thing and stay above the field. you'll get more useful information and be better for your engine. With those numbers I would be cautious but flying. Leaning will make a difference on your RPMs. Also with out wheelpants and fairings in place you may not be able to reach Full rpm even in cruise.

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  7. I can't fly it today. Minnesota has been in an atrocious pattern of southerly winds gusts to 20 and most of the runways are toward prevailing winds of course, so the net effect has been a 90-degree crosswind at the field where the plane is based. Sometimes in the evening it calms down a bit. But we'll see.

    I'm a little gun-shy after the reception in that thread on VAF

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  8. I know I've been reluctant to post on VAF at times. Never sure if some expert will see dog crap in the grass near my plane and blame me for building a shitty plane. :)

    You've been cautious and meticulous during your 11 years building, I don't see an unsafe attitude. Keep up the quest. These are just little issues that you will figure out. It's all part of the E-AB process. Many of us had the same and different issues during phase 1...heck I still find things that need attention or rework.

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  9. I found a loose KB-00 inlet fitting to the fuel pump today. Trying to look up torque value on that puppy. Not sure if this is a contributor to the remaining "problem" or not.

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    1. probably not and RPM issue, but could be a cause of fuel flow or pressure alarms. Maybe even surging or intermittent misses. You'll find more loose fittings, I know I did. I'm guessing vibration and hot/cold cycles loosen up the marginal ones. I found 3, one of which took 80hrs to locate.

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