Paul Millner's New Engine

(This article was written in 1999)

Most if not all of you know Paul Millner as our capable and (usually) patient moderator of the CFO email digest. And most of us read with interest of his '76 RG's triumphant return to the air after a bird strike/spinner failure was finally repaired. All pictures can be clicked on to load a larger image.

Of course it was only good news for a short while, as a long festering gear rigging problem reared it's ugly head, causing a nose gear collapse. The issue is a simple one, the fix nearly free. It's an excellent item for each of us to check at annual. This page contains some information on that issue.

But of greater interest are the other consequences of this event. For Paul rarely takes the easy way out, seeing opportunity where others see only problems. Paul took this opportunity to convert his RG to the separate magneto system.

These photos answer several questions: How's the project coming? What caused his gear problem? What does the back of a non-dual mag look like? What's all this about an oil filter adapter? Read on for the answers.

For those of you who missed the story, Paul had just completed a cowl repair brought on by the loss of a spinner in flight. Check out this page for pictures of that event. After landing, as he was taxiing in, his nose gear collapsed. The problem turned out to be three-fold:

The nose gear uplock indicator switch was shorted. This is the magnetic reed switch that closes when the '76 landing gear is either completely up or completely down.
The wire to the uplock indicator switch had moved out of it's correct position. This had two consequences:
- First it hammered the insulation over time, finally causing the wires to short together (that's what caused the first item.)
- Secondly, the extra layer changed the uplock geometry of the uplock eccentric. This is the switch affected by the presence of the small rubber strip that most RG's need to replace every few years. It had the same effect as having a rubber strip far too thick, changing the downlock force. Check out this page for information on this rubber strip.
Finally, Paul's gear pump had started to cycle more and more often. This is an indicator that the system had begun to develop one or more small internal leaks. The gear pump should cycle every hour or two in the air, on Paul's airplane it was down to about 6 minutes per cycle.

The means that after the nose gear touched the ground and opened the squat switch, within 6 minutes the hydraulic pressure had fallen to the point that it was no longer helping hold the nosegear down, relying on the downlock force to do that.

So as is so often the case in aviation incidents, more than one thing was wrong, in fact the more normal 3 things were wrong in this case.

For those of you celebrating your ownership of a fixed gear aircraft as this story unfolds, let us point out that with over 1000 Cardinal owners and flyers on the list for over three years, we have not heard of this situation occurring in our collective memories. At least not until this article smokes one out.. somehow there is always one!

I happened to be in town when Paul's new engine came into his repair shop. The picture to the right shows the engine being unloaded from the truck. It was a rather exciting process, with the tines of the fork truck pointed directly at the $29,000 engine as he struggled with a sticky clutch and uneven ramp.

Paul took advantage of this event to change his engine from an IO-360-A1B6D to an IO-360-A1B6. The difference is primarily in the accessory case, which has two separate mags rather than the single dual mag. The dual mag has a reputation of sorts due to it's reliance on plastic drive gears to run each mag from a central metal drive gear. Should those gears break or something physically come loose in the mag, both magnetos may come off line, especially if there are parts flying around inside the case.

Finally the engine was firmly engaged on the forks and gently lowered to the hangar floor, the lid removed and the inspection process begun.

The A1B6 engine, with separate mags, provides full magneto redundancy. There are a few modifications that need to be made to use this engine, but the legalities are easy: it is a simple log book entry since the '71 RG was originally certified with this engine.

As can be seen in the picture to the right, the accessory case looks quite different. Most significant is the lack of an oil filter. The oil screen that is evident in the picture can be replaced with an adapter that allows for use of a spin-on oil filter, although a different type than the filters that fit the A1B6D engines, as can be see on this page.

Of course there is more to a project like this than simply unbolting one engine and bolting on another.

For one thing, any issues with baffling seem to become very apparent when the little bits are all off on the floor. Some have been repaired many times while others were never correctly modified for Paul's turbo and some were badly worn.

To the right can be seen most of the baffles, laid out for inspection. They will be repaired or replaced, sent out for powder coating and reinstalled as the engine goes in, along with new silicon baffle seals.

The shop that Paul's insurance company highly recommended seemed very thorough in their inspection and capable in their repairs.

There has been some discussion of the cost of these parts from Cessna, but this shop simply makes their own. They are hand-built, a task requiring some craftsmanship but not beyond the ability of most owners, given time and patience.

There were also a number of parts to order from Cessna®. One of the nose gear side doors was available as can be seen to the right. The other one is still being located, with the option of repairing the old one remaining as a possibility.

This is the new nose gear door that arrived from Cessna®. Paul has mentioned the extra tab on the bottom of the door in the digest, wondering if that tab would protect the door from hanging up should the door link fail in the future.

Evidently one of the tricky parts of the process is trimming the gear door to fit the opening it should go into. This is a trim-to-fit part, and requires a little extra effort to make fit properly. Check out this page for information on this process.

All in All, Paul's airplane looks like it may yet get put back together. And by the time he's done he'll know even more about the Cardinal. Now that is a frightening thought.. :-)

Keith Peterson, CFO Webmaster