PT20J

Per attached: Counterweight Applications: On 4 cylinder models – the #6 as the 4th suffix character indicates one sixth and one eighth order counterweights. SSP-110-1 Certificated Engines.pdf Skip

I think you are right. I thought the override was on all models after Mooney ditched the squat switch for the airspeed switch, but I looked at a F owners manual and don’t see it mentioned. Perhaps some other F owners can clarify if it was ever on the F, or got added at the J.

A safer option is to press the little red button next to the gear switch to override the airspeed switch.

According to the Service Manual for my J, the factory used rivets instead of the two right side fuselage screws on some later models. I don’t know if this applies to the K or not, but if you don’t have screws, you will have to drill out the two rivets. Skip

Has anyone run a G5 all the way down on its internal battery? Did the "time remaining" displayed on the screen match reality? How long did it actually last? I've never had a laptop that accurately predicted battery life and so I'm wondering if the aircraft instruments are any better. Skip

According to the service manual section 32-60-03, the switch should be adjusted for 60 +/- 5 kts. When it was replaced, the shop should have calibrated it per the service manual procedure. Skip

I didn’t try it but from the way it was acting, I think it would fly it into a stall. I know that the S-TEC on the early SR-22s would. Skip

Today I tried an experiment in my 1994 M20J with a KAP 150 autopilot. I set the autopilot on heading hold and altitude hold in cruise and reduced power. The 40 year old autopilot (KAP/KFC 150 was introduced in 1980 according to the installation manual) held heading and altitude at 65 KIAS. Roll response was a little sluggish but acceptable if I added enough right rudder to keep the ball centered. The airplane was in trim when I disconnected the autopilot. Skip

I think that's a great idea. And as you noted, the FAA doesn't have the same view of logbooks that we do. For example, suppose an owner had an annual inspection performed thirteen months ago and none since, and that inspection was recorded on a single page in the aircraft logbook. As far as the FAA is concerned, the aircraft is unairworthy until it passes a new annual inspection. So, why would it care about the last one that is no longer valid? Water under the bridge. Per 91.417, you could legally rip that page out of the logbook and throw it away -- the FAA doesn't care. Skip

Agreed I was really just trying to see how far I could get at the system component level, but the exercise quickly pointed out to me how little I know -- or could find out -- about the internals of these boxes. Skip

Avionics used to be simple. Every radio or instrument performed essentially one function and there was minimal interaction between devices. Failures were pretty easy to detect, and their effects reasonably obvious. But, as my recent GTX 345 AHRS failure has shown, that's no longer the case. The AHRS acted squirrelly in both pitch and bank without any warning indication on the iPad running ForeFlight. Garmin Pilot did put up a DEGRADED warning long after I would have lost control of the airplane. Garmin tells me the AHRS system in the GTX 345 is the same used in many of their primary flight displays. I started working on a simplified Failure Modes and Effects Analysis (FMEA) for my set up. This requires several steps: 1. Identify all possible failures modes 2. Identify how each failure mode can be detected 3. Identify the effects of each failure mode 4. Design a mitigation plan for each failure mode The problem I had with doing this was identifying the failure modes for complex equipment, and knowing how to detect that a failure has occurred. Consider something complex like a PFD which displays primary instruments and navigation information. It's easy to know you have a problem if you get a big red X. But will all failures cause this indication? Who knows? Without understanding the internals, it's hard to tell what failures there might be or how you would come to find out that something has failed. The manufacturers aren't a lot of help. I called Garmin and asked how loss of the external GPS signal would affect the accuracy of the internal AHRS in the GTX 345. The tech support person didn't know and put me on hold to ask an engineer. The answer was, "It shouldn't have an effect." That's not entirely comforting. I think what saves us from falling victim to a probable host of subtle and undocumented failure modes is that modern avionics are pretty reliable. I have reasonable backups and don't worry too much about it. But, I'm retired, try not to have to be anywhere on a strict schedule, fly a NA M20J and avoid bad weather minimizing (but not completely eliminating) my IMC exposure. If I had a turbocharged airplane with FIKI and flew in the weather a lot, I would think about this more carefully -- a lot more carefully. Skip

ELTs are great, but nothing beats calling that airliner passing overhead.

The original J was the same as the F with ailerons going all the way to the tips. I think it was around 1981 that the plastic wing tips and enclosed balance weight were incorporated. The other thing that doesn't help is the chord. It takes a certain area to get the effectiveness desired. A lot of span got used for the flaps so that makes it necessary to increase chord to get the required area. I believe that the hinge moment varies linearly with span and as the square of the chord. Skip

I think this will clear up most 337 confusion: https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.9-1G.pdf Skip

BEVELED AILERONS (again): Mooney introduced beveled ailerons in the 1960s and they may have been added to reduce hinge moments (stick forces) for the PC servos. Thickening a control surface and beveling the trailing edge is a method for improving aerodynamic balance and reducing stick forces used ever since the later P-51s. For some time, I've been trying to understand exactly how they do this. I thought I understood it a while back, but was never completely satisfied. I finally found a good explanation in Airplane Stability and Control by Abzug and Larrabee. The idea goes like this: Suppose an aileron is deflected down (to raise a wing). The protrusion into the airstream thins the boundary layer on the bottom and thickens the boundary layer on the top. The thinner boundary layer tends to follow the surface contour better, so when the air flowing along the bottom gets to the trailing edge it wants to follow the bevel and deflect upward. Curving the airflow requires a pressure change -- in this case a lowering pressure at the bottom of the trailing edge. The thicker boundary layer along the top surface doesn't follow the bevel well so there is a differential pressure effect that tends to pull the aileron down which is in the desired direction. NACA report 927 (referenced by Abzug and Larrabee) quantifies the effect: Skip

The way insurance companies make money is on what Warren Buffett calls “float.” It’s the timing difference between when premiums are collected and claims are paid. The companies get to invest money that isn’t theirs to keep (it will have to be paid out in claims at some future date). But, they get to keep the investment income. When investment returns are low and losses are high, premiums will rise. It’s basic business economics. Competition ensures that the converse is also true. Skip

Pretty interesting how close the three quotes are for the carriers that would quote the risk.

Both by J’s — one manual and one electric— would cruise @ 70% with the cowl flaps closed at peak EGT with hottest cylinder 380 F or less. Manual one had flat left cowl flap rigged slightly open when closed to make room for the tubes, and electric one has the bulge.

For a K maybe. But for a J, I think they only increase my long-term maintenance costs. .

Actually, according to the BK Installation manual, it was developed in 1980. Mine flies great for 40 year old technology. Skip

Good question. Frankly, I can't see any except increased maintenance costs. My 1978 J was manual and worked fine. My 1994 is electric and it works fine, too. When I first got it, I played around with different settings, but I didn't find any utility in it. Bob Kromer has stated that they fly a bit faster when cracked open, but mine doesn't. At some point Mooney changed the left cowl flap from flat to a bulged shape similar to the exhaust pipe bulge in the right flap. I'm not sure if this coincided with adding the electric motor or not. Maybe if you have electric cowl flaps and the flat left flap cracking makes a difference. Does anyone find the electric cowl flaps very useful and if so in what conditions and on what model? Skip

So, how many carriers are left in the market?

FHP is the HP that is required just to rotate the engine at that speed. It lowers the THP — thrust hp, i.e., the power available to the prop.

Precision Airmotive (current manufacturers of RSA fuel injection systems) has a DVD on troubleshooting that includes this test. Call them and they will send it to you free of charge. @flyer338 didn’t mention whether CHTs are higher now than with earlier higher fuel flows. Concern would be that if fuel flows are now too low, engine may be too lean at full power reducing detonation margin. Skip

Depends on what I am trying to accomplish. Really, when power is available, pitch and power are used in concert. But airplane control is quicker and more precise when manipulating the elevator than by adjusting power. So, I use elevator inputs as the primary control for the parameter I want to control most precisely. For instance, on an ILS, I want to be on the glideslope and I don't care if the airspeed wanders around +/- 5 kts, so I fly the glideslope with elevator inputs and adjust airspeed with power. If I am landing on a short runway, I want my speed to be right on target and I control airspeed primarily with elevator and adjust glidepath with power. This is not the only way to do it -- it's just a technique that I find works for me. Skip