PT20J

Good idea to check the aiming when you replace the bulb.

Thanks. Any idea what rpm it’s calibrated for?

According to the wiring diagram, the hour meter is fed from the electric tachometer on my M20J. Does anyone know how this works? Is there a cut-in rpm below which it doesn’t record, or does the tach pilse modulate to simulate the hour meter on a mechanical tach? Skip

Should be possible to determine if the flaps are closing by noting CHTs.

Here's what I got from Mooney - they told me this is all they have. Skip Mooney Service Manuel M20J Vol. 2 of 2.pdf

Well, best glide is the speed that, power off, gives the minimum descent angle. Any speed, higher or lower, will result in a steeper descent. Low power isn't much different than power off.

Best glide is CL/CD max speed. To get truly on the backside of the power curve, you have to be below the minimum power required speed where CL3/2/CD is maximum, which works out to 76% of the best glide speed (for a derivation of this, see Anderson, Aircraft Performance and Design, Chapter 5). That turns out to be pretty slow. For a Mooney (and most piston powered GA airplanes) the backside of the power curve isn't the big deal that it's been made out to be. Skip

There's nothing particularly special about trimming a Mooney. It's a matter of nailing the attitude and taking the care to get it properly in trim. With a lower performance airplane like a C-172 or a PA28, the airplane doesn't gain or lose altitude very quickly with small pitch changes, so if they are slightly out of trim you don't notice the excursions as much. With a higher performance airplane, it will quickly gain or lose altitude with very small pitch changes. In other words, it is more sensitive to being slightly out of trim. Also, the nose attitude in level flight is relatively low in a Mooney compared to some other airplanes and this can cause a tendency to trim it too nose up. Cross checking with the attitude indicator will help with this. Another way to get the feel for proper trim if you have a 2-axis autopilot is to set power and put the autopilot in altitude hold and let it trim. Then disconnect the autopilot and manually move the trim wheel slightly each way to get the feel for finding the perfect trim again.

I gererally have run Lycoming O-360 and IO-360 engines between 6 and 7 qts. Probably have a couple thousand hours behind them and never saw oil pressure fluctuations as you describe. Last summer I ferried a M20J that was burning about a quart every 2 hrs and saw the oil pressure decrease to the top of the yellow (60 psi). Checked the oil level after landing and it was 4 qts. Added three qts and it was fine. I’d try running it between 6 and 7 qts, and if everything is OK, just operate it that way and don’t worry about it. If you do go tightening bolts, check the torques in the Lycoming manual. Some engine bolt torques are different than general bolt torques. Skip

Turned the lights on in a dark hangar today. The mirrors reflect the taxi light outboard and slightly ahead of the wing I suppose so you can see better to turn. The old lights were so dim that I never noticed, but the LEDs are bright enough that it may be helpful.

I’ve never received an 8130 from Mooney for any part so It’s probably a special request to get one. Lately Mooney lead time have been longer (for me anyway). I think they’re keeping inventory down and building a lot of parts to order. Zinc Chromate isn’t the best corrosion protection for steel. Mooney switched to epoxy primer at some point, which is much better. Your new parts should be epoxy primed.

Yep, that's the one. Drawing from the IPC shows the K-Mart mirror in the right wing, inboard of the taxi light.

The first annual is usually painful, in my experience. You get to find all the little things that the previous owner deferred, and they add up. Sounds like this annual was pretty thorough, so next year it should be much better. Hang in there and think of all the fun you’ll have when you get it out of the shop.

Anyone know the purpose of the little convex mirror inboard of the taxi lights on the M20Js with wing-mounted taxi and landing lights? Also, thought it funny that the IPC lists K-Mart as a source for replacement. Mine are fine; just can't figure out what they do. I never noticed it until I was replacing landing/taxi lights with LEDs today. Skip

Agree with Don. Chandelles and Lazy Eights are coordination maneuvers that are very graceful once you get the feel for the airplane at constantly changing airspeeds. One sure way to screw them up is to muck around with the power setting which puts you out of trim. Skip

Tire manufacturers recommend replacing on condition, not age. Tubes are frequently replaced along with tires as they stretch and grow in service and may be difficult to reassemble without pinching. If tubes leak significantly, the tube and valve should be leak checked in a tub of water. Taxiing and takeoff also wear tires. It’s not worth altering landing technique to save wear. A Michlen rep once told me that airline tires wear most an takeoff because the weight is greatest (fuel load).

The cylinders of a radial engine are arranged in a vertical plane and gravity causes oil to flow down to the bottom cylinders after shutdown. It can get past the rings, but mostly it fills up the lower rocker boxes and seeps into the cylinders through the valve guides. The starters on radials have a friction clutch that's supposed to slip before any damage is done, but we never trust it and always pull the props through a couple of engine revolutions before starting if it's been sitting a while. Also, when you observe someone starting a radial, you might notice the prop turning a long time before it starts. That's because we count 12 blades before turning on the mags -- just to be sure. It's unlikely that a horizontally opposed engine would have a hydraulic lock from just sitting around. However, if an engine is preserved using Lycoming's procedure in SL 180B, you will have added 2 oz. of preservative to each cylinder and this could certainly cause a problem if it were not removed. If the engine has been sitting a long time, it might be a good idea to pre-oil it as Lycoming recommends before starting a new, overhauled or rebuilt engine. This can be done by removing the spark plugs and spinning the prop either by hand or with the starter until oil pressure is indicated. This will also ensure that there is no chance of a hydraulic lock. Skip

That's what I've always heard from guys that have torn down a lot of engines.

Lycoming Service Letter L180B covers this. The engines that really rust out are the ones that live in high humidity regions and are operated infrequently over a period of years. I can't see one period of inactivity killing it. Think about automobile disk brake rotors. A few weeks of inactivity in high humidity and you'll definitely notice the rust the first time you apply the brakes. But the corrosion is on the surface and comes right off after a stop or two. You have to let them sit a long time to have them actually pit. And, the rotors didn't start out being coated with oil like the engine parts. Of course, if you had known that the annual would take so long, you would have done something differently. But, that's hindsight and you can't do anything about that. Just get it going as soon as possible and fly it often.

Mooney maintains the IPC by annotating the pdf with comments and notes and there is no revision number, so you can’t determine that yours is current. My copy, which is about 6 months old, has about 34 changes noted since the 2003 issue date. So be sure to confirm latest part numbers with your MSC when ordering.

I think Shapeways is pretty honest stating that the switches are not smooth and need sanding. I found it took quite a bit of sanding, so I can see if you sent them directly to an engraver that there would be issues since I wouldn't expect the engraver to spend the time sanding that I put in. The plastic is pretty hard and getting a reasonably smooth surface probably took me fifteen minutes for one cover -- but I'm picky. Also, the material seems a bit porous. Rather than engraving the legends, I found a font in MS Word that was a reasonably close match and then I printed it out on a clear Avery label sheet on a laser printer. Then I cut out the legends and stuck them on and sprayed the switch cover with several coats of semi-gloss clear Krylon. When I put it on the switch, it didn't seem like the fit was quite perfect, but it works great so far. I've attached the legend file I made. RADIO MASTER.docx

I'm curious how many have actually found water in the tank sumps. Maybe it's because I live on the west coast, but I've sumped thousands of times and I can only recall finding water -- and a small amount at that -- once (in Alaska 30 years ago). Now, I am NOT advocating skipping this preflight ritual -- I still sump tanks. I'm just curious about the prevalence of water. Regarding runnups: I fly for a large, well-respected 135 operator (with a very good safety record) and our FAA-approved procedure calls for the mag check, prop check and carb heat check on the first flight of the day only. Skip

The Mooney wing planform is a forward swept tapered wing. Without some form of washout, the stall would likely be uniform over the span. Stall strips disrupt the boundary layer at high angles of attack causing flow detachment (stall).

Actually the "thick" Cherokee airfoil is also laminar flow: NACA 65-415. The purpose of camber and other design parameters is the efficient generation of lift. A flat plate will generate lift at positive alpha, but it also generates a lot of drag. Remember, you only need to generate enough lift to equal the weight (and the tail down force, +/- any effects from any thrust line angle). The trick is to do it efficiently (minimum drag).

Rectangular planform (Hershey bar) wings naturally stall at the root first -- one of the reasons for choosing that planform for RVs and Cherokees. The Mooney wing has aerodynamic washout to accomplish the same thing: NACA 63-215 @ root, NACA 64-412 @ tip. Due to manufacturing tolerances, the left and right wing generally do not reach stall at exactly the same time and the stall strips are added to adjust for that. Not sure how it is done today, but in the early 90's during each airplane's factory test flights, the stall strips were attached with duct tape and adjusted until the roll at stall met specification and then they were permanently installed. At least that's what Rob McDonnell who was VP of Engineering at the time told me.