PT20J

I thought I'd resurrect this old thread because the original question gets to the core of a misunderstanding about the Mooney tail feathers that I see on MS from time to time. It turns out that a vertical stabilizer with a vertical leading edge is more effective than one with a swept back leading edge, and this allows it to be of smaller area which in turn reduces the weight and drag. The Mooney tail design wasn't greatly different from other airplanes back when Al designed it - just a bit more angular. It wasn't until around 1960 I believe that Cessna started the swept fin craze making the Mooney tail appear backwards. The interesting question is why is the vertical leading edge design more efficient? I has to do with the angle that the relative wind flows with respect to the chord line of a wing (aerodynamically, the vertical stabilizer is a vertically mounted wing with a symmetrical airfoil). The cord line is perpendicular to the leading edge of a wing. In the case of a vertical leading edge, the relative wind flows parallel to the chord line. This airflow produces the necessary aerodynamic side force ("lift" - think Bernoulli, Newton) whenever a yaw creates an angle of attack. Now consider the swept back leading edge. The chord line is still perpendicular to the leading edge, but the relative wind is now at an angle to the chord line. Some of the relative wind will flow parallel to the chord line and some will flow spanwise. The spanwise component is "wasted" in the sense that it doesn't produce any aerodynamic force. So, the useful component of the relative wind is lessened. Aerodynamic force is a function of airspeed, angle of attack and area. To achieve the same aerodynamic force at the same airspeed and angle of attack, the swept tail will need to be larger than the straight tail. Drag is also a function of area, so as the area increases, so will the drag. I believe that Bill Wheat said in Boots on the Ground that Al calculated that a swept tail would need to be about 20% larger. So, if the swept tails are just for show on small planes, why do jets have them? Jets fly fast and recall that the air flowing over a wing accelerates. When the airspeed of this accelerated air gets close to the speed of sound, the drag goes way up. The rapidly increasing wave drag as the aircraft approaches the speed of sound is why it used to be caused the "sound barrier". By applying sweep, the wing sees reduced airspeed of the component of relative wind along the chord line, and this reduces the drag. Sweep is applied to all the airplane's "wings" (wing, horizontal and vertical stabilizers) for this reason. Skip

Gee, Paul, with such a beautiful panel, you should consider one of these to replace the cigar lighter USB. Lots of configurations - even available illuminated. http://www.truebluepowerusa.com/aviation-products/usb-charging-ports/ Skip

The angle between the shaft that slips into the nose gear truss and the shaft with the T handle should be slightly acute. The T part of the handle should be about in line with the center line of the airplane when the nose wheel is straight. Put the shaft that goes into the nose gear truss in a vice and bend the handle slightly. If the angel is right, it doesn't slip out (even my fancy optional chrome plated one) even when wet. Skip

Aeroshell W100 and Philips X/C are not synthetic. Aeroshell 15W-50 is part synthetic. The additive in Aeroshell W100 Plus is the same as Lycoming LW16702 which is required for some Lycoming engines. With W100 Plus you don't have to fool around with LW 16702 which is not the same as Camguard. Camguard composition is proprietary. It might be great, or it might be unnecessary. Lot's of opinions. For sure it won't hurt anything. For what it's worth, a flight school I know of has a fleet of C-172s with O-320's. They use Philips X/C and generally get 2200+ hrs on an engine. Flying often and frequent oil changes.

Another interesting Mooney Myth If it were true, Mooney wouldn't need to specify control surface balance.

Control surfaces are mass balanced primarily to prevent flutter. There are other methods that may be used. For instance, analysis might show that a particular configuration will not flutter without balancing. Modern airliners have irreversible controls which might be less prone to flutter. So, there is no general rule except to do whatever the maintenance manual calls out for your airplane.

Amount of flap on approach is a personal preference - there are pros and cons to all. On go around or missed approach, the goal should be to get the airplane climbing in the takeoff configuration as expeditiously as possible. The sequence would be: Takeoff power, pitch to Vy attitude, if full flaps then flaps to takeoff, gear up with positive ROC, flaps up. It’s common not to pitch up aggressively enough and that’s the cause of excessive airspeed. I prefer takeoff flaps for approach for the lower nose angle and use the mnemonic PUFF: Pitch, Undercarriage, Flaps (wing), Flaps (cowl). Skip

Yep, that’s a Dzus. Miserable things. Takes a special tool to set them. Slots in the heads cam out if you don’t use the proper tool to open and close them (the old Snoopy Dzus tools work best). Springs break - and always in a place where access is problematic. It’s hard to line them all up when there are a bunch on a cowling piece. The last one never seems to catch, so you have to loosen them all and start over trying a different order. Usually the third or fourth try works. Great fun out on the ramp on a hot (or cold) day standing on a ladder wrestling DC-3 cowling pieces into place. Camlocs are the way to go. Skip

The pictures can be hard to make out. Here is a drawing showing the location of all 8 main gear zerk fittings. I verified that this is correct for my '94 M20J today while changing the oil.

While you’ve got it apart, you might also want to do the mod to prevent the aileron center link from rubbing on the landing gear bell crank if that hasn't been done. http://www.mooney.com/en/sb/M20-289A.pdf Skip

Do you have a preferred technique? Can you catch them with a small bolt extractor or left hand drill bit? If the IPC is correct (for the M20J) the forward trunnion uses a press-in zerk and the rear trunnion uses a tapered thread Do you have a favorite grease gun coupler that minimizes damage in the tight spaces? Skip

And, before someone asks: you can’t remove the roller tappets out of the newer Lycomings without splitting the case either. Hopefully, the roller tappets will obviate the need to.

Thanks for clarifying that, Clarence. I was looking at 32-10-01 which doesn’t show the grease fitting. I missed the cross reference to 57-10-02. Love the Mooney IPC Skip

Interesting that the guys that championed LOP operation and promulgated the red box concept have said they don’t see much use for percent power. Most of us learned to fly using power settings based on percent power and clearly many still do. For those that don’t — how do you decide where to park the throttle, prop, and mixture?

Interesting - my M20J IPC doesn’t show a grease fitting on the forward trunnion. Do some planes have that? From the drawing it appears that the forward trunnion uses a roller bearing which might be pre-packed and sealed, but I’ve never had one apart. Perhaps @M20Doc can shed some light here. BTW, I believe they are properly called zerk fittings (Invented by Oscar Zerk in 1929 according to Wikipedia). Skip

Just put the part that slips into the nose gear truss in a vise and bend the shaft enough that the T handle is approximately in line with the centerline of the airplane when the nose wheel is centered and it will be good. Did that on my ‘78 J after the third time I fell on my butt (slow learner). My ‘94 J has the optional very pretty chrome plated (very smooth and slippery) tow bar with the proper factory angle and it never slips, even when wet.

The standard bar won’t slip if you bend the shaft slightly so that the part that slips into the nose gear is at a slight acute angle to the shaft. Piper has nice clips on the Cherokees - you could get those, unless Piper parts prices are as bad as Mooney parts prices

Mike Busch also has recommended setting up an escrow account for a fixed duration that holds back a portion of the purchase price. If the cam survives the escrow term, the seller gets the money; if not it goes to the buyer. Seems pretty reasonable. All part of the negotiation. Skip

Pretty much this. You can minimize it but hard to check things like metallurgy. I think this sums it up. Just like the asking price, the depth of the pre-buy is whatever the buyer and seller negotiate and this will vary according to each party's perceived risk and risk tolerance. In my case, I found a 94 J with less than 1200 hours on it that had been well maintained and had some nice avionics upgrades. On the down side, it was burning about 1/2 qt per hour and hadn't been flown much the last few years. I had a thorough pre-buy done by Don Maxwell who personally borescoped the cylinders. No metal in the filter, compressions in the mid-70s, oil analysis was good and trends OK compared to previous several. The engine started and ran well. The airplane seemed a little slower than I recalled my last one, but that was many years ago, with less instrumentation and fewer antennas. I didn't even consider pulling a cylinder. I negotiated a fair price based on known condition (the rest of the pre-buy showed only very minor issues). Twenty five hours after purchase, the oil ring in #4 broke taking out part of the piston skirt and scoring the cylinder. When we pulled the jug (low compression, metal in the filter) we found the cam spalled. So, now I have a rebuilt A3B6. Cost some money, but I ditched the dual mag, and got roller lifters and a zero-time logbook. Maybe the ring was broken before I bought it. Maybe we could have figured it out if we had pulled the #4 jug. Maybe we should have pulled them all. Maybe we should have disassembled the entire engine. I think at some point you just have to accept that buying a 25-year-old piece of complicated machinery is a risky proposition. The point is: I'm fine with my decision based on what I knew at the time; others might have wanted to probe further. Skip

No, that sounds exactly right. A coordinated turn is a pitching and yawing maneuver. (A flat turn would be all yaw, a 90 deg banked turn would be all pitch. A coordinated turn is a combination of both). The g in the turn comes from the pitch rate. Rolling into a turn to counteract a pitch up is the counterpoise to leveling the wings to stop a spiral. 737 MAX guys would have to roll inverted first though.

Electrical engineers use “conventional current” -flows from positive to negative. Yes, of course we know that electrons flow the other way, but the convention predates that understanding. That’s why the emitter arrow on a transistor is in the direction opposite electron flow.

Electrical term is bus. Buss is a kiss. https://www.merriam-webster.com/dictionary/buss I was admonished about this in my first engineering job out of college.

The ACU converts digital outputs from the PFD to analog for the BK autopilots and is required on all installations. The EA100 interfaces the PFD AHRS to the BK autopilot and is only required if you remove the BK vacuum AI. Both units are external to the PFD. I don’t have a EA100 but I did just have an ACU fail and I got the impression from Aspen support that failures are not uncommon. If it’s out of warranty, you might see if you can buy a used one on eBay. Aspen also has a program through dealers to exchange failed units for refurbished ones. If you do a lot of business with an avionics shop that is an Aspen dealer, I’d try to get them to do the exchange for their cost. Skip

You know how twins have twice the probability of engine failure as singles? Well, it’s like that with electronics, too. The more stuff you cram in the cockpit, the greater the likelihood that some of it will be inop. And, inop equipment messes up your workflow. There are advantages to keeping it simpler and thinking through failure modes and avoiding single point of failures that can take out multiple capabilities.