The Home Machinist: Routers Redux

Occasionally I receive a letter from a reader that offers an insight a bit beyond the expected. An especially well-informed source, Rawson M. (great first name!) recently wrote to relate his experience working for an unnamed aircraft company. The subject of his letter was a recent installment of "The Home Machinist" in which various methods of cutting sheet aluminum were examined. The results were less than stellar when using a common router.

In another "Home Machinist" I had sneered at a kit manufacturer’s suggestion of using a disk sander to shorten a cylindrical bearing spacer.

Rawson wrote, addressing both of these subjects.

"I worked for a major aircraft company for 14 years. Routers are used to trim the ends of fuselage sections and the passenger door openings. Hand-held power saws were used to cut aluminum plate. Large disk sanders were used to trim parts to dimension.

I was not a mechanic so I can’t report on the specifics, carbide cutters, etc., but did use the technique by using my 10-inch table saw with a carbide blade to cut 0.25-inch aluminum plate and 0.25-inch wall aluminum tubing for a boat radar antenna mast. A 10-inch sanding disk worked well to dress the corners of the plate to the desired curves.”

Many years ago I'd heard that a router was used to cut window openings for the Concorde, but in that the story was 20th-hand, I didn't put a lot of credibility to it. Rawson, on the other hand, is firsthand.

So, there it is.

As for using a disk sander, in his examples of the door curves I can't think of what might work better. Additionally, putting an entire fuselage section on a lathe is a bit more than difficult, so there a sander is also the best tool.

However, "The Home Machinist" is directed to lathe owners, and in the case of a 2-inch-long cylindrical bearing spacer, there is a better tool: a lathe.

So in retrospect I have to accede to Rawson’s side of the issue by simply acknowledging that sometimes the best tool may be a rock.

Rawson, thanks for the confirmation of the router story and an illustration that the rules are not laws, only guidelines; think outside the box.

News: Cheap(er) Cubs for Sun 'n Fun

American Legend Aircraft has just announced special pricing for both its ready-to-fly Light Sport aircraft and the kitbuilt Texas Sport Cub. The airplanes are essentially the same, except that the Texas Sport Cub can be built to a 1600-pound maximum gross weight; the LSA version is limited to 1320 by the rules of the game.

For the SLSA (turnkey) versions, the new base price is $91,785, reflecting a 12% reduction. This configuration includes a traditional yellow Cub paint scheme with a black "lightning bolt" trim line, standard VFR flight instruments and engine instruments, but no radios save for an ELT. Many options are available.

The Legend Cub base model comes with the open cowling and the Continental O-200 engine turning a fixed-pitch prop. The 120-hp Jabiru 3300 is an extra-cost option; either engine choice can be had with a closed cowling.

For those who want to build the design from an Experimental/
Amateur-Built kit, there's the Texas Sport Cub. It is being offered with a $2000 credit toward options and accessories. The base kit, which includes "all the necessary components to fully complete [the airframe] section down to every nut, washer, bolt, and cotter pin," sells for $38,600 minus engine, interior, paint and avionics. The company also offers a 14- or 21-day KwikBild program.

These special offers will continue until the end of Sun 'n Fun on April 13.

We last reported on the Texas Sport Cub in our March 2008 issue.

Marc's Sportsman: Fun and Games With Pitot and Static

Every two years, as regular as rain on Saturday in Seattle, we're supposed to test the pitot-static system and confirm that the transponder and encoder are kicking out what they're supposed to be kicking out. Simple enough, but a test that I'd always sort of scorned. Day to day, everything seems to work, ATC isn't any crabbier than usual, so why open it up and muck about? This year, I'm glad we did.

After receiving recommendations from the airport locals, I called Brian Gerdes of Gerdes Aviation to come by for N30KP's pitot-static and transponder test. He quickly set up his equipment, tapped into the static line—hooking directly to the left port, and covering the right—while also sliding a curiously condom-like thing on the pitot mast. (Better safe than... oh, never mind.)

It wasn't long before he delivered some bad news. "You have a big pitot leak," he said. You mean static leak, as that's what I've heard is far more common? Nope, pitot. Hmmm, very curious.

Gerdes kept after it, and within a minute said, "Ha. Found it." I peeked over the panel and, sure enough, the plastic block on the TruTrak autopilot had cracked at the pitot fitting. (On the photo below, can you see the tiny bit of raised plastic just forward and to the left of the "P" on the label on the photo?) Lesson learned: Go easy on those fittings from now on. The autopilot will be temporarily taken out of the pitot-static loop and sent back to TruTrak for repair (plus a software upgrade, as I'm on a fairly old version), though I suspect a touch of 5-minute epoxy would do the trick.

Although Gerdes bypassed the autopilot, we still had a pitot leak. By carefully and methodically working through the system, we knew we'd find the leak, which was now smaller. "It's a crack in the line," he said, "not a full-on break. I can tell by how quickly it's leaking down."

We eventually isolated the behind-the-panel items from the line running up through the wingstrut to the pitot head and found no leaks there. With the panels off the wing for the annual, it was easy to disconnect the pitot head itself and cap the line; after retesting, we discovered there must be a break in the main pitot line between the head and the fitting behind the panel. Methodical troubleshooting works every time. Problem is, this line runs down the wingstrut, under the seats and well along the left side of the cabin. It's a long bit of nylo-seal, and the leak could be anywhere.

Ah, but luck was with me. When I built the airplane, I planned to use the Dynon angle-of-attack pitot tube, which requires its own reference line to the instrument. By the time I was out of Phase I flight test and wanting to fly some IFR—where, it's my view, you need to have a heated pitot head, period—Dynon still had only the unheated model. It was therefore replaced with a traditional Falcon heated pitot, and the extra line was simply capped off.

Easy solution, then: Swap lines. The old AOA line became the new pitot line. Ten minutes later, everything looked good. With the test rig's vacuum pump chugging away, Gerdes brought the system up to 20,000 feet, where the Dynon's maximum discrepancy was 40 feet and the backup United altimeter's was 70 feet. What's interesting about the test chart is how the steam-gauge altimeter can trend high or low from one 2000-foot increment to the next, while the Dynon is very consistent. Yet another check mark in the "good stuff" column for electronics.

The final test was on the Garmin GTX 327 transponder for frequency stability, sending the correct codes and modes, and RF output. It passed, no problem.

In all, I spent an enjoyable morning talking airplanes with Gerdes. I was grateful that we (he) found the pitot leaks, which never showed up in flight. He told me that many airplanes fly with just such problems, but I'm happy we discovered mine. The Dynon EFIS is dependent upon pitot input to, er, keep its head on straight, so it behooves me to maintain that system in top shape. Without this inspection, I never would have known about the leak.

Gerdes charges $225 for the inspection. Money well spent.

News: Lancair Continues Flight Testing Its Evolution, Releases Prelim Performance Stats

Lancair continues to put hours (and now four flights) on its Evolution turboprop in the run up to Sun 'n Fun. According to the company, the preliminary handling assessment is "Stick forces: balanced, light control inputs. Stall characteristics: Meets FAR Part 23, docile, full aileron authority in stall. Roll rate: > 80°/second."

Performance is a claimed 338 knots true on 39 gallons per hour of Jet A. Pulling back to economy cruise, true airspeed is said to be 270 knots on 24 gph. Both performance figures assume the prototype's Pratt & Whitney PT6A-135A engine. "Solo" rate of climb is listed as 4000 feet per minute.

Lancair is aiming for a 61-knot landing-configuration stall speed.

We expect to hear more from Lancair about the continuing flight-testing during next week's Sun 'n Fun show in Lakeland, Florida. The KITPLANES staff will be there to bring you all the latest news.

Rick & Ace's Folly...er, GlaStar: Tales of the Repeat Offender

The "Repeat Offender" epithet isn't really mine. KITPLANES editor Marc Cook bestowed it upon me when I recently advised him that I was building another airplane. He's just as guilty as I am, seeing how his first project (a Pulsar XP, back in his pre-family days) was just a warm-up for his Glastar [he refuses to capitalize the S] Sportsman project. Coincidentally, my current airplane-to-be is a GlaStar that just happened to become available at the right time.

Funny thing is, I had been itching to build something again since finishing up the Zodiac 601 XL back in January of 2007. But finding another project immediately wasn't a huge priority, as there are plenty of things in daily life that preclude devoting all of your time to messing about with airplanes. Unfortunately.

Sometime around the first of March in 2008, I got a phone call from my buddy Earl Hibler, who always has his ear to ground (!) where aviation is concerned. Seemed he knew of a virgin GlaStar kit that had only made it to the initial inventory stage, then spent the last five years carefully stored away while its original builder followed the siren song of Formula 1 air racing. That pursuit led to an abrupt and tragic conclusion in late 2007, leaving those who knew and cherished Patrick Gleason the difficult task of picking up the pieces and moving on. Earl allowed that finding a quick buyer for the kit would not only help out those left to settle the estate, but the lucky purchaser would most likely end up with a nice airplane as well. Did I know of anyone who might maybe be interested? Someone who might actually be able to pay for it?

After a few moments of gut-wrenching indecision, we set a date to go see the kit a few days later. And having just made a recent and sizable investment in the Zenith project, I knew I'd have to find another co-conspirator to help shoulder the investment and buck a rivet or two. One short phone call later, I had my longtime flying buddy Len "Ace" Rodriquez on board. He couldn't break away from work to go check out the kit, but said he trusted my judgement. Man! I thought he knew me better than that after almost 30 years!



Looks like it's all there!
A short time later, Earl and I arrived at the home of Chris Beffa, Pat Gleason's significant other. Introductions were made, and she proceeded to show me the GlaStar kit. The wings, fuselage, rudder and horizontal stabilizer were all carefully hung via block and tackle in her garage. The motor mount was hanging in its own little corner, and the rest of parts had been carefully labeled and tucked away here and there. Some parts, like the fuel tanks, seat pans, cowl halves, and windshield, had been tucked away in various hallway and bedroom closets.

Chris mentioned that it would be nice to regain some living and storage space, and who could resist that? An offer was quickly made, and accepted, and a deposit was placed. The next step was to rent a big truck, get Ace, and set another date to pick up the kit. March 15th seemed good for all parties involved.

Driving home, I called Ace to let him know that he now owned half of a GlaStar kit, and had something else to do on weekends besides lie on his couch with his dog and watch Springer. Normally, he's not the emotive type, but I could tell he was excited about finally getting his own airplane. (And it's about time, as he's always been happy to just fly everyone else's!)

Next step: Go get it!

Amy's RV-10: Just Rewards

I knew it would run eventually; I just didn't know when. I thought that the leaking right fuel tank would slow our RV-10 build down, but so far it is turning out to be just a blip.

With little fanfare the other evening, just before sunset, my husband pulled the project forward, shuffling our airplane stack so that it was the first machine out of the hangar the next morning. I looked out my office window and saw it sitting in the driveway, gleaming in the mottled sunshine, surrounded by a phalanx of small fire extinguishers.

That's how I knew it was time. I rushed out with my camera, not even the good one, just in time to hear the Sky-Tec lightweight starter easily kick over the Lycoming IO-540 for the first light of its rebuilt life. After two years pickled and hanging on its motor mounts, the engine shuddered to life.

White, then dark smoke puffed from the dual exhausts, which seemed, at low power, like they were going to shake right off. But they didn't, and as the engine rpm increased the smoke disappeared, and the airplane seemed to settle into something smoother. One minute. Then shutdown.

The engine was still cool enough to lay your palms on the cylinder fins. Still, a fan was immediately mounted on top of the engine to pull away residual heat. Sealant oozed from the slip joints of the exhaust pipes, and steamed off. A few drops of oil blew out, but then there'd been a lot of oiling going on that morning during the pre-start lube. No obvious leaks. Not even fuel (being provided by the still attached, non-leaking left tank).

A second start and run for 1.5 minutes was nominal. And later, a third 2 minute run at a leaner mixture provided a much smoother experience. The only snags? The throw rod on the primer is a bit long and interferes with the control stick in the cockpit. But that's no problem. We've ordered a shorter rod.

For longer ground runs we've installed an aluminum cooling shroud attached to the top of the engine to duct in air. The hope is to keep those temperatures nominal throughout the initial, and highly critical break-in period. Here's hoping that works.

The end of the day found my husband and a buddy imbibing in a celebratory Lite beer while recapping the excitement. No remorse. Just smiles and deep satisfaction. That's why we build.


http://www.blogger.com/img/videoplayer.swf?videoUrl=http%3A%2F%2Fv1.nonxt7.googlevideo.com%2Fvideoplayback%3Fid%3De355952ce879ddae%26itag%3D5%26begin%3D0%26len%3D86400000%26app%3Dblogger%26et%3Dplay%26el%3DEMBEDDED%26ip%3D0.0.0.0%26ipbits%3D0%26expire%3D1269277384%26sparams%3Did%252Citag%252Cip%252Cipbits%252Cexpire%26signature%3D1FC57C233CFAC9F891689BC6259D7D609D1953A1.856B5F3BC8A8722586BBA8CB22A99E7561652CAC%26key%3Dck1&nogvlm=1&thumbnailUrl=http%3A%2F%2Fvideo.google.com%2FThumbnailServer2%3Fapp%3Dblogger%26contentid%3De355952ce879ddae%26offsetms%3D5000%26itag%3Dw320%26sigh%3DKW03EoWbtyLQC66Zg7Td_LefAzY&messagesUrl=video.google.com%2FFlashUiStrings.xlb%3Fframe%3Dflashstrings%26hl%3Den