Cowling test mount

Since a majority of the stuff in the engine compartment (aka firewall forward in airplane lingo) has been installed I needed to start thinking about the cowling. This is a notoriously hard task because the fit and finish of the fiberglass cowl from the factory sucks. The cowl and the baffling work together to cool the engine. Keep in mind aircraft engines are not typically cooled with a radiator like your car - they use air to cool down the engine.

We ran into some problems installing the cowling. The fuel injection servo has brackets on either side to control the throttle and mixture. Evidently, the mixture bracket is under some stress because of the angle that it's supported. It's hard to describe but I'll grab a photo as I explore a solution. In addition, The mixture "bracket" is controlled by a cable with a threaded rod end, but I'm pretty sure that should have safety wire to secure it in place. Need to follow up on that.

So, with the mixture linkage all screwy the problem is that the cowl doesn't fit properly. For some reason, the forward air box (basically ram air intake) is slightly angled to the co-pilot's side by about 15 degrees. Even with that eccentricity, the mixture cable linkage interferes with the side of the cowling. What's even weirder is that on the pilot side (where the mixture is) there is not any clearance at all, but on the co-pilot side (where the throttle is) there is 3 inches of extra space. This is all while the cowling is secured on the perimeter so it should be pretty much centered. Kelly suggested finding out if we can cut the fiberglass and expand the scoop portion of the ram air intake so there is just more room to work with.

Thottle side - plenty of room

Mixture linkage interefence

Magneto drive gear

In the previous post, I had just purchased an EMag Air brand PMag  Model 114 electronic ignition to replace my left side Slick brand magneto ignition model 4370. To run the internal alternator and provide a position sensor, you need to take the gear drive off the magneto and put it on the PMag.

My friend Kelly from work came over to give me a hand. He grew up around airplanes but never got around to flying, he built a show winning '44 ford pickup that he inherited from his grandad. He knows his way around a machine shop and engine better than I do so he was a helpful hand. So, off came the old gear drive, which required a gear puller and a busted finger (sorry Kelly!) 

Here's the PMag with the gear drive installed. It was a tough balancing act to torque the castle nut to the correct torque value (120 - 150 in-lbs) but still have the hole line up for the cotter pin. The PMag came with 2 washers so we ended up just using one so we could expose more threads and allow the cotter pin to line up with castle nut.

The final step was attaching the cotter pin. Turns out it wasn't as easy as I thought to crimp that down but prevent it from protruding past the gear so it won't scrape up the engine case when it's bolted in the accessory case. Anyway, all done! Just need to install it, and of course I forgot to bring the mounting nuts from home. But it should be easy to just pop it in the next time.

Engine work: Ignition

The ignition systems on most small planes are dated technology that are relatively reliable, but require frequent maintenance and don't deliver very good performance. When I got the project, it had 2 magentos - Slick brand 4370 on the left ignition and a Slick 4371 on the right ignition. Kind of like nuke plants, there are 2 (or more) of everything. In case one ignition breaks, you have another one. For those not in the know, each ignition system delivers a spark to each cylinder. If you're good at math you'll realize that this means a 4 cylinder engine has 8 spark plugs. Sounds great, until you find out that some of these spark plugs can cost $50 each, or more.

So what's the answer? Fortunately, engines in airplanes work the same way the ones in your car do. Except your car has better performance than the typical airplane engine because it has fancy electronics that use solid state sensors. Well, cars abandoned distributors sometime in the 90's (I think?) and went to electronic ignitions. These are finally being adapted to airplanes. Now, why go with electronic ignition? Well, for one the maintenance is non-existent... you don't have to rebuild it every 500 hour (or less). You don't have power being robbed from the crank and accessory case. The spark advance is variable with manifold pressure (as it should be). Mags run fixed spark advance timing so your engine won't run optimally across the rpm range. They are lighter (weight reduction is a big deal in small planes). It uses regular car spark plugs (about $2.50 each). Oh, and it makes the engine run smoother, easier to start, and the spark is more efficient so you can reduce the mixture to run lean of peak and save gas. Of course, there's no free lunch. The downside? Unknown failure modes, electronics could shit the bed, sensitive to heat, might have electromagnetic noise (bad for navigation radios), and ... it needs power to run. The mags run straight off the engine.

I chose an E-mag air PMag model 114. The reason I went with this brand instead of something else was:

• long time on the market
• good performance reviews
• no need for electrical power (internally powered)
• plus, they are a Texas company!

So, last weekend I pulled the old Slick 4370 magneto off the left side of the ignition to make way for the PMag. The 4731 will stay because it is the impulse magneto, which basically means it has extra pieces parts that allow it to start the engine. This means I can start the engine with either the left side 4371 magneto, or with the new PMag, or ideally both. Plus, I needed the accessory case drive gear  from the old 4370 for the new PMag. Some people replace the 4371 since it has more moving parts and needs a 1 inch spacer (weight). I figure I'll start here, and maybe down the line upgrade the left one.

Lawnmower

Laura's dad had an "extra" lawnmower in the attic and he was kind enough to give it to me. The only problem was that it didn't work. He told me that it would run for about 1 second if you poured gas directly into the intake. Should be an easy fix, right?

Carburetor

So, I grabbed a can of carb cleaner, and sprayed it all over the intake and carb. Ok, good enough, let's start it up. Sure enough it would start, but only run for about 1 second. I probably repeated this process 50 times until my arms gave up. 

I figured that the carbon deposits would clear out eventually. Well, nope. Then it was off to amazon to purchase the rebuild kit. Unfortunately, I had no manual or clue what carb this was so ordered one on a hunch. Good thing Briggs & Stratton appears to be universal because it worked. I also found this great YouTube video with tips on how to get the o-rings out. Anyhow, as you can see it was gummed up with old gas.

Take note of the bolt used to secure the bowl of the carb at the bottom. It has a hole in it that meters the fuel so clean that out really well.

The $7 part kit worked fantastic, after replacing the parts and cleaning it out worked great! If you have problems with the lawnmower engine starting but failing to run, this is the first place I'd look.