PT20J

I learned a while back working on radials (most of which have planetary reduction gears): the tach always reads crankshaft RPM.

My experience is that pretty much no company will admit they ever made an inferior product. I don't know why. Once you have a better replacement, being honest helps rebuild trust. Denials in the face of evidence to the contrary never makes the problem go away (I know this from experience: my career was in tech product development). We have literally a 5 gal bucket at the museum full of Champion massive electrode plugs that have >>5K ohm resistance that we've removed from the B-25, DC-3, Tigercat and all the other airplanes. We remove them from service because high plug resistance can cause insulation breakdown (punch through) in the shielded ignition harness. Want to have a really bad day: try replacing ignition leads on a radial engine. Joe did offer that Champion would replace the resistors in them at no charge if we returned them, but the design is bad and they'd just fail again. Now, if Champion would replace them with the new design, we might have something to talk about. But, we've long ago switched to Tempest; massives in the front and fine wire in the rear (we remove and gap the fronts every year to do the compression test at annual inspection, but we seldom remove the rears as they are a PITA to get to. There is no need to rotate plugs on a radial -- odd number of cylinders).

Interesting. Here's the Champion chart. I checked the Tempest chart and it agrees with Lycoming.

I spoke with Joe Logie from Champion Aerospace at a trade show yesterday. He had a cutaway of Champion's improved massive electrode plug with the molded-in resistor (no more resistor/spring/screw). I'd be willing to bet these are as good as the Tempest plugs. Anyway, I got a set with my factory rebuilt Lycoming IO-360-A3B6, so I'll keep a check on the resistance and see how they age. I asked about fine wires vs. massives. His take is that there is a theoretical advantage because, especially when new, the spark may jump the gap deeper in the plug closer to the insulator on a massive electrode plug. As the electrodes wear, the bending adjustment to close the gap causes the spark to be more likely to occur nearer the tip. So, maybe worn out plugs perform better? This is all theory -- there's no data. He did say you could get the same effect at lower cost with the BY plugs for engines that will accept them (the angle valve Lycoming IO-360s will not). He said Champion recommends the fine wires for engines that are oily, run several hundred hours per year, or have plugs that are difficult to remove (rear plugs on radials for instance). Skip

Did you check the compression on that cylinder? Curious if it changed during the break in process.

Try airpowerinc.com

I did a little research on the Cherokee wing and tail. The PA28-181 has 10 square feet more wing area than the PA28-180, and 5-1/2 feet greater span. The PA28-181 stabilator is also about 7 square feet larger than on the PA28-180. Both airplanes have the same wing loading. I doubt the change in the wing would have any effect on pitch trim with flaps. The pitch effect of flaps on any wing (it doesn't matter high wing or low wing or short wing or long wing) is to increase the negative (nose down) pitching moment. The downwash interaction with the tail is what determines whether the whole airplane pitches up or down when flaps are extended. The semi-tapered wing, being of greater aspect ratio, has less induced drag than the rectangular wing. At low airspeeds, where induced drag predominates, the semi-tapered wing gives improved climb performance and a reduced power off sink rate compared to the rectangular wing. This comes at a slight penalty in cruise speed and the necessity of adding washout to the wing to get the root to stall first (Mooney did it with an airfoil change rather than washout). The rectangular wing naturally stalls at the root first.

Interesting. How did you figure out which cylinder was the culprit?

The G switch responds to longitudinal deceleration. Turbulence and hard landings generate (mostly) vertical accelerations.

Good question. I haven’t flown a Cherokee for a few years and I don’t recall. But I don’t remember the Hershey bar being different from the semi-tapered wing in terms of pitch trim with flaps, and I don’t see any reason why it should be. Flaps increase effective wing camber which increases the nose down pitching moment of the wing. It also increases the downwash angle which changes the effective angle of attack at the horizontal stabilizer. The interplay of these two effects determine whether flap deployment requires nose up or down trim. Hey, Nate @Natemuncy17 help us out here. Remind us which way you need to add trim when putting in the first two notches of flaps. And tell us whether it's a PA28-180 or a -181 (constant chord or semi-tapered wing). Thanks. Skip

Good question. I haven’t flown a Cherokee for a few years and I don’t recall. But I don’t remember the Hershey bar being different from the semi-tapered wing in terms of pitch trim with flaps, and I don’t see any reason why it should be. Flaps increase effective wing camber which increases the nose down pitching moment of the wing. It also increases the downwash angle which changes the effective angle of attack at the horizontal stabilizer. The interplay of these two effects determine whether flap deployment requires nose up or down trim.

The Archer is one of my favorite airplanes and the one I most enjoyed instructing in. It has a comfortable cabin and seating position, nice handling characteristics, gentle stall. The rear seats come out easily to haul cargo, the manual flaps are simple and you can step on them getting into the airplane. The oleo struts cushion your landings even if you drop it in a little. It seems a well thought out design (well except for that stupid air cylinder vertical seat adjustment device). Best of all, Piper has made a ton of them, parts are available and any mechanic worth his A&P certificate can work on one without screwing it up. So, why did I recently buy a Mooney? Well, it goes faster on not much more gas, kind of looks like a Cherokee and is easy to describe to non-pilots meeting you at the airport (we'll be in the airplane with the tail on backwards). Transitioning from a Cherokee to a Mooney is pretty simple. Both airplanes are single-engine, low wing monoplanes with nearly the same power and size. Of course you will have retractable gear, constant speed prop and cowl flaps to deal with, but in my experience everyone gets the hang of these pretty quickly. The Cherokee is a little touchy to get trimmed just right and that's good practice for the Mooney. The Mooney flaps are more effective in reducing stall speed that on the Cherokee. The wing is low to the ground -- lots of ground effect and the effective flaps will make for a lot of float if you are a couple of knots too fast. The Mooney is, of course, much cleaner so it takes more planning to slow down. If you have speed brakes, don't use them until you can manage the energy perfectly well without them. That way, they won't become a crutch for poor technique. You'll find it faster in the landing pattern so make your patterns wider to give yourself room until you get the hang of it. And, with those rubber doughnuts instead of the oleos, you will really feel your touchdowns. Most Mooneys have better avionics than the typical Archer, so for the first few hours concentrate on flying and leave all the fancy avionics alone no matter how tempting it is to play with the new toys. And keep engine operation simple at first, too. Just run ROP at reasonable power settings. Lots of time to explore all the avionics can do and LOP operations in your future. You'll have a blast. Skip

You're going to have to explain that to me. Don't see why that would be aerodynamically - the airfoil didn't change, just the aspect ratio and wing area.

Let's see if we can summarize: ELTs have two problems: failure to activate in a crash, and high false activation rate. From an engineering standpoint, it is difficult to achieve both at low cost. There are three generations of ELTs meeting TSO-C91, TSO-C91a and TSO-C126. Each generation has attempted to improve these parameters. The failure to activate rate has improved; the false alarm rate has not (see Molnar 2005 - pg. 95 and InFO18007) No one knows why some ELTs go off absent a crash. Most activations are thought to be mishandling, accidental activation or maintenance related. There is some evidence that first generation ELTs did suffer from switch and corrosion issues (Trundell 1990, Pg. 7-8). This data is suspect since it is unexplained how the failure mode was determined in each false alarm case. It may just be the reporter's best guess. If every falsely activated unit were returned to the manufacturer for analysis, then we might know something, but this is not generally done. TSO-C91 units have not been manufactured or legal for new installations since 1995, but there are probably a lot of them in the field. So, what to do? An ELT that falsely activates when the cause is unknown should be considered unreliable. TSO-C91 and TSO-C91a units have not been monitored by satellites since 2009 and are of marginal SAR value and should be replaced with a TSO-C126 406MHz unit. A malfunctioning TSO-C126 unit should be returned to the manufacturer for analysis and repair. The minimum legal requirement per 91.207 in any case is to replace the battery if it has been activated for more than an hour. Skip InFO18007.pdf Molnar 2005.pdf Trudell 1990.pdf

Kind of like that master switch that keeps failing ON and running the battery down? Or the moisture that makes the the gear retract all by itself? Maybe ghosts?

Good idea Phil!

An ELT is pretty unlikely to go off for no reason. Most likely scenario is that it was set off the last time you flew, and the hangar shielded it so that the signal was weak, and so it took a long time to find it. You didn't say what ELT you have but if it was a TSO-C91A ELT, the satellites haven't monitored its 121.5/243.0 MHz transmissions since 2009, so someone would have had to listening to 121.5 nearby to even notice it. Since you have no way of knowing how long it was transmitting, you'll have to replace the battery anyway and that would be a good time to have it checked out.

Tell me more...

Noise in headset and voltage drops under moderate load sounds like a bad diode in the alternator.

Guy, @GEE-BEE can you make the wing walk in one piece? Is it self-adhesive backed or does it require glue? What kind of glue? Skip

There are other airplanes out there without this baggage

Well, maybe it's just a good copy. The Mooney engineers used to tell how Piper was looking for a competitor to the Bonanza and wanted to buy the Mooney design. Supposedly, Mooney flew a plane to Lock Haven and while Mooney and Piper were having lunch, the Piper engineers swarmed the M20 with cameras and tape measures. I have no idea if this story is true or not. However, the two airplanes bear an uncanny resemblance: they have similar dimensions, the same forward swept wing, similar airfoils and the planforms lay over each other amazingly well with the exception of the empennage.

Isn't the Cirrus stall recovery to pull the chute The falling leaf is a great coordination exercise and a lot of fun.

Yep. So...... tell us about it.

Good feedback, Bob. Hey Clarence, @M20Doc since you shelled out $2K, can you convince me I should switch to iridium plugs at my next plug change on my new rebuilt IO-360-A3B6? Skip