Wednesday, October 24, 2012

The First Start

You can tell when an airplane project is almost done when you start to get visitors that want to sit in it and pretend to be flying. To be fair, I asked Co-pilot Egg to try it on for size.  She got a real kick out of the video-game style avionics.

Before too long, she was trying to bridge her knowledge of what old-style mechanical gauges looked like to what the new fancy-schmancy stuff built into the Dynon. Unfortunately her experience with the antique stuff never prepared her for an electronic HSI, synthetic vision, or terrain avoidance.

With the tourism obligation fulfilled, I turned my attention to the first time starting the engine. This is not as trivial as one might assume. The Rotax is very different from the traditional airplane engines that I cut my teeth on lo those many years ago, and continue to use today. A couple of major differences are the dry-sump engine oil system and the fact that the sides of the cylinders are liquid cooled. Both of these differences manifest themselves quite heavily when it comes time to introduce the applicable fluids to the engine. This became difficult almost immediately - I spent quite a bit of time trying to deduce the correct flavors of antifreeze and motor oil. I ended up with a 50-50 pre-diluted DexCool antifreeze (Prestone, I think, but the actual brand name matters not) and Mobil 1 V-Tail synthetic motorcycle oil. Motorcycle oil is used because it contains the additives required to keep the gear box happy.

Having the proper fluids on hand is important, but it is equally important to know how to introduce them to the engine. There are procedures spelled out in Rotax Service Instructions (which you're more or less required to go find for yourself), but they are somewhat reticent in nature. They aren't completely useless, but they certainly spare words whenever and wherever they can. Best, I thought, to have The Jackson Two lend a hand given that they have relatively recent experience with the process.  Now the thing to know about these guys is that they don't just come up from Jackson and consult from the sidelines; it really ends up being something more akin to an Amish barn raising. They jump right in and we get some really efficient teamwork going almost immediately. This is, of course, one of the chief selling points of the Van's RV airplanes - the spirit of camaraderie and the willingness to share knowledge simply isn't available in any other community.

So, here's the antifreeze going in. It actually gets poured into two locations: the little reservoir on top of the engine and the additional reserve in the little plastic jug hanging on the firewall.

The oil purging process is where the real complexity lies. You don't just pour the oil in like you would with a dry sump Lycoming. Rather, you have to put air pressure on the system to assist in getting the oil pushed completely through the much longer path of hoses and coolers that are the hallmark of the Rotax dry sump engine.  To get the air pressure behind the oil, the oil return line is removed from the oil tank and the fitting gets plugged. The overflow line is removed and the air source is plugged in at the fitting. A regulator is used on the air hose from the compressor to keep the PSI below a meager 15 psi. The maximum allowed is 15 psi, but we used something more like 5 - 7 psi.

Naturally I was in charge of making sure all of the required parts were on hand, which is why we didn't have a cap for the oil tank. I ended up taking the "parts on hand" responsibility quite literally as a result.

While I held the air pressure in with a finger, Kyle swung the prop. Pete monitored the engine monitor. The idea was that somewhere between 20 and 60 swings of the prop, Pete would see an oil pressure indication on the Dynon.

Quite a few prop rotations later, success!

And there we were: the moment of truth!

We spent the last few moments going over the start procedure (throttle to idle, choke on, ignition switches on, crank the engine, choke off when it catches, throttle to 2,000 rpm for two minutes, throttle up to 2,200 - 2,500 rpm until the oil temp reaches 122 F degrees) before I locked myself in for the big moment.

And there it goes!!

Kyle hunted for leaks or other untoward events while I puzzled over the big red FAIL X sitting over the indication for the right side cylinder head temp. 

Great, a wiring problem. Ugh.

After the required oil temp was reached, I shut it down and pushed her back into the hangar to the next step.

The idea is that the engine would have run long enough to fill the valve lifters with oil. This needed to be checked, though, because a "soft" lifter is going to be a problem when the engine is run at higher power settings.

It only takes the removal of a single allen head bolt to get the covers off. Then it's just a matter of pushing on the valve springs to test their resistance.

The piston for each cylinder has to be at the top of its travel to make the test work correctly.  That means looking down into the sparkplug hole looking for the top surface of the piston.

With all that done, I went for extra points. I don't have a big cut-off wheel, so I had them bring theirs. I wanted to take an inch off of the exhaust pipe because it's too long and interferes with the installation and removal of the bottom cowling.

In case you're wondering about the marked improvement in the quality of the pictures, most of them were taken by Pete's son Keith. I should have hired him on as staff photographer ages ago!


Steve said...

Congrats, Dave!

Watched the video last night. Nice to hear more about it in the write-up. Good call on on the photographer, too.

Kevin said...

Very exciting to read your latests posts, Dave. If possible, could you amend the post to document exactly how much motorcycle oil was added to reach "full" before startup? Thanks!

DaveG said...

It took 3.5 quarts.

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