Archive

Archive for June, 2010

Oil Cooler

I spent what little time I had available on Monday fabricating mounting brackets for the oil cooler. It’s crazy how much time this little stuff can take. Here are the brackets installed temporarily to check the fit. I’ll need to visit the aviation aisle at Ace to pick up some slightly longer case bolts to accommodate the thickness of the new brackets.

This is the front side of the cooler. I mounted nutplates in the new brackets and used 8-32 panhead screws to hold the cooler in place.

This is the outlet side of the oil cooler. The depth of the oil cooler worked out that in this case, I drilled holes in the brackets and installed a couple of nutplates in the oil cooler flange. There were already holes drilled for nutplates in the flange from a previous installation so all I had to do was clean out the silicone caulking and do a slight touch-up on the machine countersinking.

After the installation, I once-again verified the clearance by installing the upper cowl and using this piece of angle between the firewall and the spinner. Nothing rubs!

I left the hangar a few minutes early this afternoon so that I could drop off the cooler at the local radiator shop before they closed for the evening. I’ll pick it up Friday morning when I get back to town. I figure it’s worth spending a few bucks having it checked out and cleaned. It’d be a shame to have engine problems due to a problem with the oil cooler.

The next big task will be creating a fiberglass diffuser box and tubes to come off the front end of the cylinder plenum. I’ll probably get started with that on Friday. I ordered another few feet of Aeroquip 303 hose and firesleeve to fabricate the additional oil lines. Man, that stuff isn’t cheap! By the time all’s said and done, I’ll have a total of about $150 in 2 30-inch hoses!


2nd Flight & Oil Cooler

After talking with my engine rebuilder, I decided I may have been a little too conservative regarding my oil temperature on the first flight. I decided to try another flight before taking measures to mitigate the “problem.” Yesterday morning provided nearly ideal conditions for a 2nd flight. The winds were calm, the skies were clear and the temperature was a very mild 70 degrees. The airplane flew beautifully, but the oil temperature was even higher. I landed as the oil temp reached 240 degrees. I called a few friends to see if anyone could suggest a local source for an oil cooler.

A friend of a friend had this 5-row Stewart Warner cooler laying around his workshop collecting dust. He agreed to sell it to me at a very reasonable price. After receiving an email from another Midget Mustang builder, I’ve decided to try mounting the oil cooler on top of the case.

I fabricated these brackets using some scrap aluminum angle I had laying around my shop. I’ll need 4 of these in this same basic shape. These will hold the forward edge of the cooler.

With the cooler bolted into place, I installed the upper cowling to check for clearance. I couldn’t feel anything touching even when I banged on the top of the cowling. I also used this piece of aluminum angle to verify the clearance. Looks like I’ll be in good shape.

Unfortunately, I have a few outside commitments this afternoon so I had to quit out at the hangar by a little after noon. Depending on how things go, I may make it back to the hangar later this evening. If not, I should be able to spend most of the day tomorrow working on this project.


First Flight

At approximately 9:15am Mountain Daylight Time on June 20, 2010, N881MM took to the skies. I made about 6 laps around the pattern and called it a day. The oil temperature was creeping higher and higher and I wanted to stop to investigate. After talking with the engine guy, I will do 1-2 more flights before considering an oil cooler. I don’t mind adding a cooler, but don’t want to unnecessarily add weight and complexity if my oil temp issue is simply a matter of breaking in a new engine.
The only other real squawk is that I managed to wire my electric trim backwards so that UP is DOWN and DOWN is UP. Woops. Luckily, the plane has very good control authority and trim is a luxury item, not a necessity. The situation is easily corrected by reversing two wires at the control servo.
I achieved 2100 rpm in a full power static run-up just before launching. I was climbing at 90-95 mph indicated at about 8-900 feet per minute. The density altitude at field elevation was 6400′. It was a relatively cool morning.
I’m not real current in small airplanes or taildraggers so I planned to use all of our 8500′ runway. I pretty much did. Again, more of a luxury than a necessity. The plane seemed to track nice and straight. It was sensitive, but in a good way, not a twitchy way.
I left the power in on one long leg and let the plane accelerate to an indicated 145 mph. I didn’t think to look at my GPS for a ground speed, but a post flight check of the GPS history showed a max ground speed of 167 mph. Given almost calm winds and a density altitude of approximately 7500′, my groundspeed was pretty close to my true airspeed. I’m satisfied that my airspeed indicator is fairly accurate at that airspeed.
I have to go to work this evening, but I’ll be back tomorrow morning. If the weather cooperates, I’m hoping for a second flight tomorrow night before I leave for a 4-day trip on Tuesday morning.
If I don’t have any additional problems, I think I’ll be able to make it to Oshkosh this year. I still need to fabricate an auxiliary fuel tank, install wheel pants and possibly install an oil cooler. I’m sure the next 4 weeks will pass quickly!


Tailwheel, Alternator & Neoprene

After painting my tailwheel assembly black, I reinstalled it on the aircraft. I also installed the springs and chains for tailwheel control. As I mentioned in my previous post, I taxied this setup around the airport the other day and it works great.

I purchased this B&C permanent magnet alternator via a Barnstormers classified ad. After a few discussions with the good folks at B&C, I have discovered that this is one of their earlier generation alternators and I’ll most-likely send it in for an upgrade to the newest version. I still feel like I got a pretty good deal on this alternator because not only was the price for the alternator itself reasonable, it also came with a voltage regulator AND the O-200 gear drive assembly. The gear drive is apparently becoming more and more expensive and difficult to come by. I’ll get the plane flying first and install the alternator as a rainy day project.

I found a local source for 5mm neoprene rubber. I stopped by my hangar this Tuesday morning before reporting to work at my regular job. I cut and glued up these tubes of neoprene so that they’d have a chance to cure while I’m out of town. I’m hoping to return to my hangar after I get off work tomorrow evening to glue these tubes to my plenum and to my cowling. The neoprene will provide the flexible connection between my engine cooling and combustion air intakes and my cowling.


It Moooooves!

No pictures from today yet, but I achieved another milestone. The airplane moved under its own power today! After re-installing the freshly painted tailwheel and the wing root fairings, I hopped in and taxied it around the airport. The whole event only lasted one-tenth on the Hobbs meter, but it was really cool.
As part of my refurbishment process, I replaced the original, stiff spring tailwheel setup with a Van’s Aircraft tapered rod tailwheel. I’m very pleased to say that the Van’s tailwheel provides a MUCH improved ride on the ground. Prior to the Van’s tapered rod, I swear I could feel a bump every time the tailwheel crossed even a painted line on the taxiway. Now, the plane just seems to float down the taxi lane.
My brakes felt firm, but not grabby. I tried out the full-swivel tailwheel and it worked exactly as I had hoped it would. I have steering via the rudder pedals until I lightly tap the brake which causes the tailwheel to pass a detent and go into full-swivel mode. To stop swiveling, lead the turn and tap the brake in the other direction. Voila! It works very intuitively.
I messed up and waited too long to go buy neoprene foam fabric to finish up my cowling inlet transitions. By the time I had arrived at the local vendor, they had gone home for the weekend. Oh well, there’s always Monday morning. I also still need to visit Aerographics to have them produce my labels for the instrument panel. The Airworthiness Certificate didn’t arrive in today’s mail, either. I’m hoping to make contact with my engine rebuilder tomorrow afternoon to have him fill out my engine logbook. I’m working on and off all weekend so progress will be hit and miss. Monday will be the most likely day to see any progress. I go to work next week Tuesday through Friday. Looks like my first flight will be next weekend sometime.


Oil Screen, Baffles, Seatbelts, Tailwheel

I had a very slight oil leak from the oil screen and temperature probe area so I removed the screen and probe and replaced the copper crush washers. In the process, I discovered that the temperature probe was not torqued adequately. Subsequent engine runs have confirmed no more oil drips. I examined the filter looking for any bad stuff. The only thing I found was a few flakes of red paint and these tiny white flecks of what looks like lithium grease. They’re not hard and can be smeared with a finger. Good news. I cleaned the screen and reinstalled it.

Next on my list of things to do was tying the cylinder baffles in place with safety wire. It took a little patience, but I think it came out well. Once the plenum is screwed in place, everything firms up very nicely. I hadn’t done this before because I wanted to convince myself that my fiberglass baffles wouldn’t instantly turn to goo when I started the engine. They’re holding up very well.

My EAA Tech Counselor suggested that I add a couple more nutplates to the forward edge of my leftside plenum. Sounded like a reasonable idea so I got the job done.

I hadn’t taken the time to paint my tailwheel parts. Since they’re pretty much all steel, they were starting to show some surface rust even in the relatively dry climate of my Colorado hangar. I don’t want problems with rust down the road, so I took time this afternoon to paint them. This is the fork from my tailwheel setup hanging from the inside of my hangar door.

I intentionally held off on installing my seatbelts because I didn’t want them to get dirty or be in the way. The time has come and the seatbelts are installed! I think they look pretty sharp. Hooker Harnesses, by the way, if anyone’s interested.

Yet another picture of my instrument panel. I’m really happy with the way this turned out. I need to get with the folks at Aerographics to cut the labels for me. I’m thinking I may go see them on Friday. It’s really nice to have them local.

When the A&P visited last Friday to start the Condition Inspection, we both knew there were things that still needed to be done before the plane would be airworthy. We started with a clean white board and made a list. Lists like this help me stay on task. I had a few family things and a little work to do over the past few days, but I made a pretty good dent in the list today before having to go to work tomorrow.
UPDATE AS OF Monday Morning:
I received an email from the DAR who’s going to reissue my Airworthiness Certificate with my new N-Number. He’s going to do it this week and I should have a new Airworthiness Certificate in my hand on Thursday when I return home from work. Aside from the panel labels, about the only thing remaining to do is make sure the paperwork is in order. I’ve got a pretty busy work schedule between now and June 18th, so a realistic time for my first flight is probably sometime between June 19th and 21st. Woo, hoo!


Weight & Balance, Engine Start

I continued taking measurements for my weight and balance. This picture of my scale readout is after I’ve added all the fuel my header tank will hold. I did this as the plane sat on the scales with the tail in the level flight attitude as I had done for the initial weighing. As you can see, with full fuel, the plane weighs 743 pounds. This is 90 pounds or exactly 15 gallons of fuel. Pretty cool how that worked out. Also of special importance is that the tail weight did not change a single pound as I added fuel. This means that the fuel is EXACTLY on the aircraft’s CG. This is GREAT news because I won’t have to worry about a weight shift and potentially being out of CG depending on the fuel quantity.

After I finished with the fuel, I trolled around the airport until I found a guy wandering around who looked to be of average proportions. There’s a guy who sits “on call” at a fire bomber near the corner of our airfield. He made the mistake of riding his bicycle close to my hangar and I nabbed him! He sat in my Midget Mustang and I again raised the tail to the level flight position and took a measurement. Working backwards from these numbers, I derived the Arm measurement for the pilot seat. The calculated Arm is 87.8 inches aft of the tip of the spinner. I’ve seen others use 92.6 inches. I’m happy that mine’s actually a little forward of the 92.6 because I need as much weight forward as I can get.

The day had finally come. On June 2, 2010 at approximately 8:30am I wheeled my little beast outside for the first engine start.

At the suggestion of my EAA Tech Counselor, we removed the bottom plugs and spun the engine with the starter until we had oil pressure. It was almost scary how fast the prop spun with my B&C starter and very little resistance!

The engine started instantaneously and ran pretty darned good. The idle mixture was a little rich so we fiddled with that. It sounds like the meanest Harley motorcycle you’ve ever heard. We had a very slight oil drip from where the oil temperature probe screws into the back of the oil screen housing. My bad… I just didn’t tighten the probe well enough. I’m a little paranoid about over-torquing things.
I guess I don’t have any more pictures so I’ll just tell you about the other events of the last few days.
Yesterday (Friday) an A&P conducted a Condition Inspection. He suggested we do this to help determine what needs to be accomplished to make the bird airworthy. We both knew there were things remaining to do, so we just made a list on a white board on my hangar. When I’ve accomplished the things on the list, he will come back and verify everything and then sign my logbooks. I’ve been in contact with a local DAR who will be issuing a new Airworthiness Certificate to match my new N-number. Since the plane has already been certified as an aircraft and received its original Airworthiness Certificate back in 2002, the new Airworthiness Certificate is just a paperwork item. I’m hoping to hear back from the DAR in the very near future because I don’t think it’ll take me that long to fix the squawks we found during the condition inspection.
Unfortunately, my commercial flying schedule is very full for the next several weeks. Even though I only have a few things left to do, it might take me several weeks to get the project in the air. I’ve got a total of 3 days off in the next 2 weeks. Bummer.


Cowling, Plenum, Weight & Balance

Where does a single guy store his newly-painted airplane cowling until he’s ready to install it on an airplane? Why, the living room, of course! Might as well. It’s not like there’s any furniture in there to get in the way of airplane parts storage! I filled, sanded, and primed the inside of my cowling until it was as smooth as the exterior. I had the paint shop paint it white. I like the idea of having it smooth and finished so it’s easy to keep clean. White will make any oil leaks very easy to spot.

I’ve propped the two cowl halves together just to see what it’s going to look like. Very cool if you asked me!

Here’s a birds eye view of my engine compartment with the plenums and the baffles installed. I still need to buy some neoprene to make the connection between the cowling and the plenums. I managed to mess up the paint on the plenums by spraying the clear before the black had fully cured. Anywhere the black paint was a little heavy, the clear dried to a crinkled look. I’m going to go with it for now with the idea that I may sand and repaint at a later date.

The cowling installed on the airplane. I think it looks pretty decent.

This is the closed thing I’ve got to a picture of the finished project. Kinda exciting to see it this far along. I’m hoping to start the engine sometime this week.

The weight & balance session. It’s necessary to have the airplane level in pitch and roll. I used my Smart Level with the “beep” function activated to do this by myself. I have a few things laying on the airplane where they’ll be installed. Specifically, the wheel pants, a couple of aluminum fairing pieces and a short piece of scat tubing are laying on the airplane.

This is the brain box for my new set of Intercomp racing scales. They work very well for weighing aircraft. I’m happy to say that once my plane was leveled left to right and front to back, the weights came out dead on in the left/right axis. The tail is a little heavier than I’d like it to be, but it’s a workable number. 653 pounds is not the lightest Midget Mustang, but it’s far from the heaviest. I included 5 quarts of oil in these measurements.

The “balance” portion of the weight & balance computation requires that a reference datum be established. I stuck with tradition and used the tip of my spinner as the zero point. I dropped a plumb bob and measured aft from there to find the location of the main gear and the tailwheel. I’ll add fuel tomorrow and work backwards to find the exact arm of the fuel. I’m also hoping to use my FAA-standard 170# brother to objectively determine the arm for the pilot station. I’ll use dumbells for the baggage compartment.
Well, I guess that’s all for today. I really need to push pause on the airplane project again to do some other work, but I hate to stop now when I’m so close to a few more milestones. I’ll probably split the difference and spend tomorrow morning at my office and then head to the airport tomorrow afternoon again. I’ve got to go fly big airplanes on Thursday and Friday. I’ll use the time in the hotel room on Thursday to gather my thoughts and develop a plan of action for the rest of the project.