All about aircraft magnetos

There are times when it feels like I just can't get over the final part of building the RV-7A. The last few hours are taking forever -- months, really -- and the most recent disappointment was discovering the other day that I couldn't get the RPM over 1900. I adjusted the throttle cable and was able to get it to 2000, but lost the ability to get it to idle below 1,000. Geez. So it appears the total throw of the throttle assembly at the fuel servo is greater than the total travel of the throttle cable. What do I do about that? I have no idea.

This revelation revealed something more serious over the weekend. The engine is seriously mistimed. We originally timed it just before first start last September. But because I had removed the ring gear and reinstalled it, the timing marks on the gear were not aligned properly so we had to determined top dead center (TDC) and made Sharpie marks on the ring gear. This was a mistake.

In recent test runs, I noticed the propeller would stop as it started to wind and then start again. It was on the cusp of a kickback,apparently.

My first step was to remove the propeller this weekend and orient the timing marks properly. That helped us determine, thanks to Mike Hilger, who actually knows what he's doing, that the impulse coupling is firing wayyyy early.

I'll need to retime things but I don't have the equipment. I ordered the Rite System deluxe kit from Aircraft Spruce yesterday and it should be here in a few days. That will help me determine -- perfectly, I hope -- top dead center of the #1 cylinder piston, which should allow me to adjust the mag to fire at the proper time.

And therein lies the problem. First, I don't know much about this process but, second, I do know enough that the oil cooler hoses have to come off, the oil filter has to come off, and some fuel hoses may have to be removed to allow me access to the mag. Also some secured probe and electrical wires may be in the way.

It feels like starting over. When I take the oil filter off, it burps oil out of the crankcase, presumably coming from the oil cooler, which sits slightly higher. To avoid the mess, I guess I'll just drain all the oil out of the crankcase. Nothing but time and money. Time and money.

In the meantime, I have to try to learn what I'm doing with the mag. Fortunately, the EAA -- you remember the EAA, right? It's the outfit that all the whiners on Van's Air Force regularly say has nothing for homebuilders anymore -- has provided this webinar on magnetos.



So, it appears reports of this plane being nearly ready for inspection are somewhat incorrect.

This week, I'll pass 3,000 hours on the project.

Brad's first engine start

My RV-building pal, Brad Benson, fired up his RV-6 engine today for the first time at South St. Paul's Fleming Field (KSGS). He estimates 6-8 weeks before he's flying.



Shortly before that, Brad's hangar mate -- Vince Bastiani -- invited me along for a ride to Red Wing in his RV-7 and back. Bryan Flood, who has an RV-9 formed up for a flight of two to Red Wing.

Update After all of the festivities, the B-25, "Miss Mitchell" dropped by.

The solo

If I had to do it over again, I think I'd try to enjoy the first solo -- sole manipulator of an airplane. Mine was back around 1997 and all I can really remember is that after the CFI got out of the plane and told me to go do three touch-and-goes, I taxied out to the runway at St. Paul's Holman Field while singing some Z.Z. Top song, only to be overcome by panic that I'd accidentally keyed the mic.

I hadn't.

And that's pretty much all I remember. I was concentrating and working too hard that I didn't write the memories to disk.

So it was fun today to stumble across this video that a young man up in St. Cloud provided about his first solo.

Good job, kid.

It's in the mail!

I'll be darned. You can fit 11 years of work into a 9x12 envelope.

The plane is done -- more or less -- and a few weeks of organizing paperwork culminated today with walking the envelope to the Post Office. Inside is all the paperwork I need to get the process started for a final inspection by the DAR (Designated Airworthiness Representative) of the FAA.

It's really happening.

There's still plenty of work to do. I've organized the paperwork and logs at the hangar. I'm a little concerned because I don't have a paperwork trail of inspections by technical counselors along the way of this project, but the DAR -- hopefully -- will be Tim Mahoney of St. Cloud, who knows the RV community pretty well and took a quick look at my project last year when he was doing the inspection for my hangar mate. And, let's face it, I'm not much of an unknown in the world of building RVs.

I've also scheduled transition training with Tom Berge for the week of May 22nd. The insurance carrier requires five hours of transition training, but even if it didn't, I'd want significant stick time in an RV before venturing out on my own.

The sales tax has been paid (actually, just added to the home equity; my plan to have the engine paid off by first flight failed and failed miserably), the insurance has been upgraded to full flight coverage, and now I'm looking for a temporary hangar at Airlake in Farmington/Lakeville.

My airport -- Fleming Field in South Saint Paul -- does not allow first flights because the houses are backed right up to the airport fence. Instead, I'll get a corridor assigned to me to take off and travel to Airlake. I'm not sure how I'm going to find temporary quarters but I've begun the search.

The only things left for the plane itself are a fire extinguisher (ordered) and a new ELT battery (not ordered yet).

When will the first flight be? Sometime in June. Do you really need a hint?

The history of N614EF

Now that the plane is about finished, I've posted a PDF version of my builder's log, with plenty of pictures and commentary. It's a big file so be patient.

Find it here.

N614EF weight & balance

She's a good-sized girl!

I rented some aircraft scales today and weighed the new plane. The total came in a little higher than I thought it would, until I remembered I have manual trim which requires a heavy cable, I've done a lot of fiberglass work, and I've got a full interior.

In the end, it came in 3 pounds lighter than the sample RV-7A in Van's Aircraft's weight & balance guidelines.

The air racers

I've never been motivated to head to Reno to watch the air races, but I'm pretty sure I'm going to find an iMax theater showing this new film soon.

What happened in Reno?

(cross posted from the day job)

In the aftermath of last fall's tragic crash at the air races in Reno, some "experts" suggested the age of the pilot was a contributing factor in the disaster that killed 10.

Today, the National Transportation Safety Board released its recommendations as a result of the crash and none of them involve the age of the pilot. Instead, it focuses on the decisions he made months before the race.

"Our investigation revealed that this pilot, in this airplane, had never flown at this speed on this course," Chairman Deborah Hersman said.

The NTSB recommendations center on the fact that the air racing officials exercise no or little control over the designs airplane owners resort to in order to wring as much speed out of the planes as possible.

In its letter to race organizers today (available here) , the NTSB said the organizers relied only on the say-so of the pilot that the plane was safe:

The NTSB notes, however, that such a statement does not necessarily mean that the airplane, with its modifications, was evaluated while operating within the speed and flight regimes that would be encountered on the race course. Review of the airplane's maintenance records and documentation associated with its experimental airworthiness certificate found no evidence that any engineering evaluation of the modifications had been performed. Such an evaluation would provide an opportunity to identify potential unintended consequences of the modifications. For example, shortened wings require higher angles of attack, which, if executed at higher speeds, raise the possibility of destabilizing effects or control anomalies. The use of one tab to drive both elevators raises concerns about structure and flutter; the pinned elevator tab also raises concerns about stiffness and flutter. The addition of weight behind the hinge line of the elevator tabs may decrease the flutter margin.

It's significant the NTSB focused on the trim tab on the elevator. Here's what I wrote last year:

I have no idea what happened, but it was pretty clear to me by watching the video that it involved the area of the elevator -- the control surfaces on the back of the tail that control aircraft pitch. Am I right? I don't know.

Since then, there's been a focus on the "trim tab," a small piece along the elevator that a pilot can adjust to set a plane's pitch without needing to exert control input via the yoke so intensely.

The NTSB hasn't yet determined the specific cause of the crash, but it appears heading for a ruling that "flutter" is the culprit. Flutter is a frequency that oscillates perpendicularly, is eventually transferred to sound waves that literally rip a plane apart.

The agency said it's concerned that the Reno Air Racing Association didn't analyze any of the plane's modifications to ensure that it could safety operate over crowds.

The NTSB also urged a change in the course design and confirmed that the pilot probably blacked out because of high g forces. It recommended g-force training for all pilots and a requirement they wear g suits to minimize the effects of decreased blood flow to the brain.

Hotline post: Installing wheel pants

April 6, 2012) -- Perhaps like you, I've been able to get a lot of good construction information during the 11-year build of my RV-7A from the various builder websites that have sprouted up in the last decade or so.

But one of the areas where good information is hard to come by is the installation of wheel pants and leg fairing. My suspicion is that by the time most builders get around to this, they're pretty sick of updating their websites. Also, many builders are so anxious to get into the air, they save wheel pant work for well after the plane is flying, and well after they've stopped documenting their build.

(More at RV Builder's Hotline)

The woman who landed an airplane

I've loved the story this week about Helen Collins, who landed a twin-engine plane in Sturgeon Bay, Wisconsin after her husband collapsed and died.

The media did her a great disservice in originally portraying her as a woman who didn't know how to fly. She did. She'd actually soloed in an airplane (though not a twin) although she never got her pilot certificate.

She apparently did so at the insistence of her husband, who wanted her protected in case something happened to her.

WBAY in Green Bay has made the entire incident available. Click here to listen to it and you'll notice at one point she complained about too many instructions, "and I'm forgetting about flying." A good lesson, indeed, to remember to fly the airplane.

For you pilots who have a non-flying spouse, you should consider the Pinch Hitter Course. It's pretty cheap insurance.

Let's not twist again

A lot of RV airplane projects that aren't nearly as far along as mine have had their first flights, but I'm not ready to fly mine quite yet. I decided some time ago that I would complete the plane as far as possible before its flight test, even if some of the parts I'm working on will be removed for first flight.

Hello, gear leg fairings!

The fairings, which will not be installed for first flight, are usually left to the "I'll get around to it stage" of experimental aircraft projects. They're needed to provide a smoother air flow over the wheels and gear legs and increase speed by 5-10 knots, a helpful thing when you consider the current price of a gallon of 100LL fuel at Fleming Field (KSGS) is currently $5.19.

But the process of fitting them properly is painstakingly slow. By this point in the construction process, however, if you haven't learned patience, you probably shouldn't be building.

My pal, Chris Knauf, was good enough to do some of the construction in the gear leg fairings and he did a great job getting them trimmed and the hinges installed. All that's left to do is fit them properly.

A misfitting fairing can act like a rudder or aileron and change the direction the airplane wants to fly from straight-and-true to didn't-we-just-fly-over-here?

My job this week has been getting those fairings fitted properly. The right-side leg fairing fit pretty well-- a very minor twist that I can take care of easy enough.

Last night, I set the left-side fairing up. The process for this is pretty funky. You mark the centerline of the fuselage, then pick three points on the gear-leg fairing and make an "extended centerline" back to a point on the horizontal stabilizer. I'm using an advanced aviation tool to provide the marking of that point from the tail to the floor -- a broomstick; three actually.

Then I take dental floss (it doesn't sag like string and allows for more precise measurement, plus it makes the hangar smell minty fresh!) and attach it to one of the three points on the front of the fairing and run the string back to the broomstick, so you have two parallel lines of dental floss to the front of the fairing. This, basically, simulates airflow over the fairing.

The distance between the center of the aft end of the fairing and each piece of string should be the same, indicating that the fairing is perfectly centered in the airstream with regard to the centerline of the fuselage.

On this particular fairing, I adjusted the bottom of the fairing to make that distance about 15/32". The mark halfway up the fairing was a little more off, and the distance on one side of the top mark was about 14/32" and on the other side was about 27/32". This, you may have surmised is the dreaded "twisted fairing."

There's no real way to work this out because the fairing is only clamped at the very top. There's nothing -- without an intersection fairing -- to hold the bottom from moving in order to twist the top into position.

The solution? I don't know, but I assume I'm not the first one to experience this problem. I'll begin researching it and eventually solve the problem and include it in an article I'm writing for the RV Builder's Hotline.

I just need a little more patience.

Thinking Oshkosh

Outside of my office window in Saint Paul, Minnesota, there's a lot of construction going on for light-rail coming from Minneapolis.

But all I see is something that's got me thinking Oshkosh (AirVenture). That's the way it is around this time of the year for us EAAers.

Mystery of the unbalanced elevator

As I near the end of the RV-7A project, it seems as though the mysteries grow a bit deeper.

Here's one I had today:

A few weeks ago, when Tom Berge and Doug Weiler came by to do the pre-inspection inspection, they pointed out the unbalanced elevators, which have lead counterweights in them so that they default to level with the horizontal stabilizer.

I, of course, had noticed this too and it was a bit puzzling since long ago I put the horizontal stabilizer on the workbench and attached the elevators and made sure they balanced perfectly. But, as you can see, now they don't.

We kind of figured that because the lead counterweight wasn't fully mounted forward on the "counterbalance arms" on the right elevator, that this was the problem. So I ordered a 25 pound bag of lead shot and planned to mix up an epoxy slurry to fill in the gap, adding weight to make it balance perfectly.

Then I unbolted the elevators from each other and from the pushrod to the elevator bellcrank (which goes forward to the control sticks, which, by the way, are all perfectly aligned).

Ruh roh...

It balances perfectly, so that's not our problem.

Over on the left side, we see the offending elevator.

But that elevator, too, had been balanced on the workbench. So we figure it has to be the very thick and rigid trim cable. I'm one of the few people building an RV, I think, that didn't use the optional electric motor trim. But I installed it per the plans. It attaches at the bottom of the elevator after snaking its way from the tail, into the horizontal stabilizer and out to the elevator in an "S" pattern. I don't have an image of it but it's connected to the trim tab, which hangs on the elevator.

If you enlarge this image, you can see down the forward end of the elevator where the cable exits the horizontal stablizer and goes out through the elevator. There's no play in the cable because it's clamped in the fuselage.

As we follow the cable forward, this is where it exits (or enters depending on which way you're going) the horizontal stabilizer through the horizontal stabilizer spar...

And down into the fuselage. Note the adel clamp to prevent chafing and movement.

Inside that green shroud is the small cable which control the trim tab. We checked it at both extreme settings to see if that also changed the balance, and it did not.

Everything here, as near as we can tell, is per the plans of the aircraft, and yet it overrides the proper balance of the elevators. We're writing to Van's Aircraft support to see what we should do.

I haven't pulled the cable off the stabilizer yet to see what difference that would make because to fully know, I'd have to drill rivets out of the "inspection panel" on the bottom of the elevator and pull the cable forward. It's a real pain in the neck to do that and, even more so, to put it back.

There's one possibility that I haven't checked, it's that I didn't leave enough cable inside the horizontal stabilizer, and with it clamped on the turtle deck of the fuselage, perhaps it's "pulling" on the trim tab connection a little bit, forcing the whole operation down. It's a shot in the dark, but perhaps loosening that Adel clamp and pushing more cable from the fuselage into the HS to see if it pushes the elevators back into position would be a good start to solving the mystery.

By the way, here's another reason why keeping a good builder log is important. I scrolled back through it to be sure that I had the trim tab on the left elevator when I balanced everything originally, and that it was balanced.

One last piece of trivia: While doing this yesterday, I passed 2,900 hours of work on the project.

Update 3/5/12 9:16 a.m. I messed around with the amount of slack in the HS to no significant difference.

Getting ready for Oshkosh

It never fails. It's time to turn the calendar from February to March, and it's snowing in Minnesota. So I'm thinking about Oshkosh.

I've been talking to my pals at EAA Radio in anticipation of returning to do more work with them at this year's AirVenture, in particular doing more segments and stories around homebuilding and individuals (I like telling stories of just one person at a time), and I hope you'll share yours with me this year.

They've also raised the possibility of me hosting a one-hour show Monday-Sunday at noon and what guests I might like them (and me) to pursue.

I don't want to just be "the homebuilder guy" but I certainly want to be a homebuilder guy because I think that perspective hasn't gotten as much attention (although the interview I did with the RVers who flew up from Brazil in '10 qualified).

I'd like to get a list of people you'd like to hear on the air for a segment so I can go about tracking them down (and first finding out they're going to be at Oshkosh). An example: I'd like to have both Lane Wallace and Lauren Paine Jr. on.

Who would you like to hear? Don't hold back, now.

Stow's Minute Man Field defies conventional thinking

What's this? Another good story about aviation? Don't worry. The usual suspects on Van's Air Force and other aviation forums won't be posting this and commenting that "the media never tells positive stories about aviation."

It's in today's Boston Globe and it's about the marvelous Stow Airport, which isn't far from the ancestral homeland. Add it to your list of fun places to fly to, stop at the on-field restaurant and bitch about the media.

The airport in Stow was a grass landing strip in 1966 when Paul McPherson, an inventor who loved to fly, bought the land and renamed it Minute Man Air Field.

The new airport opened in 1969 as a family business. McPherson’s son, Don, then 23, paved the runway and began to manage the airport. His wife, Peg, opened a coffee shop called Peg’s Place, where their daughter also worked.


After just three years, Paul died in an airplane crash, probably caused by a heart attack, in Acton. Don McPherson took over and still owns and runs the airport, which is now home to a second runway, several flight-training schools, a bakery, a printing company, and more than 60 planes and helicopters. His wife, Nancy, runs a restaurant that serves vegetables, meat, cheese, and other products from local farms. On the weekends, Don is a host at Nancy’s Air Field Café.