Getting ready for the Third First-Flight
The summer of 2005 lasted here from April to October. This 100 degree OAT timeframe was scientifically chosen for first flight and engine testing in order to prevent frost from being a safety issue. This note chronicles a few thoughts and reactions to the evolving understanding of how well or not the 0-290 engine installation works, first on ground runs and then in the air.
April 2005The 0-290 now has ten starts and 0.7 ground run time. The new plenums and wraps and such have been step-cured. And now I finally have all the new components on speaking terms – accomplishing mag timing, confirming electronic ignition operation, and getting to know the carb accelerator pump. Pilot starting technique aren’t ever be a problem of course, ha, but am gaining experience. Six of the ten starts have been on the first or second pull. The way it purrs, I may call it Morris or Garfield, or Felix.
Why is this called the Third First Flight?VariEze N95BJ’s first flight back in 1996 was uneventful. That 0-235 and prop had already flown a year and a half on Scott Carter’s LongEZ and was just broken in good. I also had the advantage of three months in the front seat of Nat Puffer’s original VariEze before lifting off in mine for the first time. The airframe was the only unknown. It only needed a small rudder shim to get on the straight and level.
The second-first flight, three years later was with the new untried downdraft plenums. That flight was actually approached with more apprehension than the airplane’s first flight because of the significant unknowns with the unique plenum cooling installation. Ground tests were good but then I somehow had to determine that it would also work at two thousand feet. I was well aware of what over-temping on climb-out could mean. But once in the air the summertime CHT’s were tamed on takeoff roll and then reduced nicely on downwind. It worked. Ha.
This Third First-Flight – with the 0-290 – is upcoming (This was written in summer of 05. It wasn’t yet known that the development period would include a pesky leaking intake valve fouling one cylinder occasionally, and a firing but bad plug).Last night the three friends (mag, E.I. and accelerator pump) let the pilot in a little on their mutual philosophy/conspiracy. In other words, I am getting the hang of how to prime and pump and position the throttle this time of year.
The carb heat temp effectiveness was also tested last night. Ground runs have shown interesting intake cooling activity (condensation on the long, curved intake) so a considerable number of carb heat designs were scuffled through to come up with a robust system. This one feeds from the lower plenum next to the exhaust and travels only a few inches to the intake.
At the suggestion of Terry Schubert, a Radio Shack remote outdoor/indoor temp gauge temp sender was plugged into the gourd / carb intake for an actual temperature measurement, rather than just looking for the engine run-up drop in rpm. At a thousand rpm the carb heat lever was fully opened. I was looking for a 90 F degree increase. The gauge started at 62 degrees and in a few seconds went to 96, and then 119, and then blinked HHH, obviously still climbing. Robust enough.
Overall the throttle and engine response is what I would have expected from a normal intake setup. Scott Carter spent a day helping to trace proper engine operation. There was a hesitancy that he resolved by finding and tightening up one of the intake tube hose clamps. It had been tightened appropriately so someone must have snuck in and loosened it.
Four A&Ps have had their toes in the pie working on or checking the engine along the way. Fresh eyes are good and I like to learn from them. Each has contributed in his own way to accurate installation and adjustment of normal items, as well as sometimes offering comments on the implementation or expectations of the unique components.
Cowl Fire Warning System- At least one other person is installing the engine fire detection loop. I’ll look back in a few years to see if that simple dual wire element was ever used to advantage in the heat of battle.
For liftoff this third time, the alien-like entrails and repositioned elements of this “air pump” will have to orchestrate together in flight. The ground runs have helped to step normally through some areas. Of course I can only totally confirm the mutual cooperation of these creations at 12 K… when up there at 12 K. Oh, and eventually, Jackpot if possible.
May 2005Liftoff.Here we go. Waiting for the afternoon to fly ensures frost won’t be a factor All items on the pre-first flight checklist are marked off and there’s nothing left to be gained on the ground. Already checked the safety of flight items; the canopy safety catch catches, and the warning system checks good for the nose strut and canopy handle and throttle positions.
Rolling onto 17L there is a slight left crosswind. There is six thousand feet ahead of me and the abort point is generous. Canopy latches have caught the bolts, and it’s locked. Could land back on the runway or the two parallel taxiways, or the cross taxiway; nope no one is on them right now.
Throttle up, good oil and fuel pressure, good rpm, airspeeds moving, half-throttle matches the old acceleration, elevators trimmed ¾ inch TE down, nose lifting at 55, rpms still good, we’re off like a prom dress, good vibrations (none) and the end of the runway coming up at 200 feet and 150 mph, can make a comfortable loft back to the runway from here if needed, turning crosswind into the wind keeps me closer to the centerline for a turn back around if needed, but for now looking good on crosswind here, leveling out downwind, CHTs 400, 405, 390, 410. Oil pressure good,
Holding 140 mph up to 2500 feet. That didn’t take long. Let tower know I’ll be up here a while and level and power back a little for a minute. Winglets and everything still on and cooling inlets look…good I guess; they’re still there. A little nose down trim. CHTs all about 360. Smaller inlets now for the 0-290 and still got about the same CHTs as with the 0-235. (I wont’ know for sure until the chrome cylinders are broken in, but there might be a slight bump-up of CHT temperature, indicating that the inlets might have finally been reduced (from 2×9 each) to about optimum at 1×5 inches each).
Getting the feel of the old steed again, it seems a little weird in a couple of ways maybe, but probably just because I’m paying too much attention. Leave her alone and she’ll be fine. This turn could be better…wonder if I got the same aileron-throw back after the paint job? Hey there she is, liking that rudder. Now I remember – a little rudder makes things nice. I’m the one that needs to be getting up to speed again, not her.
I’m liking it here at 2500 feet. Nice that the sunset has stayed about the same while I’ve been gone. What is that hissing noise? Something’s hissing every few seconds. I don’t even have anything pressurized but it sure is hissing. Let’s see, which of the new items … Hey you’re not going to trick me into loosing track of things here, oil’s good…good pressure but the temp is still rising, no traffic coming over the top here…there’s that hissing again…CHTs good, RPMs, speed, good, no one sneaking up on me, what could be hissing?Everything’s stable now so let’s focus on this hiss. Don’t see any canopy seal flapping and all three catches are in place. OK the last was about four seconds in duration, clear left, there it is again, let’s time it here…about six seconds, I’ve got time to watch it awhile, the plane’s good, just got to keep an eye out for transients up here, everybody likes 2500 feet…there’s the hissing again…four seconds, again, six seconds…What the…Good grief.Hope no one ever finds out that the demons I’ve been chasing up here were vanquished by readjusting the David Clarks a little. Only heard the hissing when looking way around back. I guess the ear seals were not quite as supple after sitting in the locker a while – What a dunce.
Oil temp is not going to come down. Time to hit the showers. One guy entering on downwind on the other side. Let him know I’m descending over here, will probably beat him to calling base. Oil temp will need some attention. Aiming on touching down a third of the way down the runway, coming around nice with a little rudder, right there, settling in just like we knew what we were doing. Set that Eze attitude and… cool, on the ground with no bounce or joggle, hold the nose up here for some drag, cheated death again.
June 05. After thirteen flights now N95BJ has returned to shapely elegance on the ground and in the air. But, she is adroitly evading oil cooling advances with a flip of her winglets. Each short flight is a little longer with more and more room for dalliances and power runs. The upholstery finishes off the new look nicely. The engine intake system continues to act normal. Carb heat temperatures have been normal – good – from the beginnig. Cool.
This always-almost-there pilot has been in sunset withdrawal for some time. But now the much needed airborne therapy is once again salving the ravaging wounds of life. Of course this is part of living the Big Life, right? Whatever, I am again ushering the sleek steed into the hangar after sunset tinged outings, with both of us better for it. The oil temps are still high, but maybe only about as high as everyone else’s in this Texas heat. Still working on getting it down a little, probably with a relocation of the oil cooler. Will probably incorporate it into the lower plenum ducting for some augmented draw from the exhausts. (Did that, worked some but not well enough).
Oil Blow-byI had heard about the possibility of significant oil blow-by in 0-290s from the case vent, and experienced a little of it. Tim LoDolce suggested relocating the case breather vent from near the prop, to the accessory case with the elbow welded into the mag hole cover plate. This was simple and worked. The ‘clear’ case vent tube exits by the exhaust. There is an in line air-oil can that is emptied occasionally.
Along the way the vernatherm operation was confirmed. On the next flight the oil temp stabilized with moderate power. The good cylinder temps continue to allow the engine and my stomach to be comfortable in the 98 degree OAT. After about 45 minutes of this longest yet flight the CHTs were happily observed to make a pretty uniform 35-45 degree reduction. With all the one-after-another delays this was a welcomed advance.
What do they call someone that tries the same thing expecting different results? OK, that title fits, but what about someone that tries half a dozen different things and gets the same inglorious results…Actually, because of past experience and the expected need for robust oil cooling, it was approached in an aggressive manner from the start, hoping to capitalize on earlier oil cooling successes. A lightweight oil sump with internal cooling tubes is used to assist the more traditional components, like the oil cooler. But that still hasn’t been optimized.The previous 0-235 oil cooling finally worked with unlimited full power runs and climbs by enclosing the oil sump and directing a cool air inlet blowing up its aluminum skirt. This lowered summer oil temps about 15 degrees at full throttle. You can see the skirt with the rubber baffling in the Featured Canards section.It is hoped that the internal tubes will also be a helpful addition at some point. I will know more after fiddling with that area some more.
At this point (summer 05) there is little time spent on one distraction. Once normal or acceptable operation in confirmed in that area, it is no longer a squeaky wheel and attention is turned to the next distracter.
Besides the still undetected leaking intake valve and sputtering spark plug, the initial 0-290 flights were thwarted by two inaccurate oil temp gauges in a row. The first gauge read way low, giving a false indication of good temps. Fortunately keeping an eye; actually a hand, on the oil sump caught the inaccuracy. The second gauge indicated 75 degrees high, with flights cut short unnecessarily, mucking up otherwise impeccable troubleshooting prowess and delaying progress. The third gauge now is within 5 degrees of the two test thermometers. Thanks to the author of the article that described how to check the gauges.
The oil cooler location will be moved. Several tweaks have stabilized the temp but didn’t appreciably reduce it. The old girl is back and just needs a little skirt straightening.
>>Summer 06 – Oil cooling is now good even on hot days. Ha. Am selectively removing the little spoilers that had helped to improve airflow in the cowl to see if they are still needed. Stay cool,Bill James, Fort Worth VariEze
