Jerry 5TJ

What are the wear limits on the uplock block? Photo is of "C" model with 4000 hours, apparently the original uplock block. Taken in flight, the view is from below and shows how the steel top of the Johnson bar has worn a groove in the aluminum block's ramp. The hole is worn oval, and the end of the locking pin appears worn to a bevel, too. It feels secure when I latch it, and give a big "heave ho" test on the handle as part of the GUMP check. Questions for the forum: (1) Is there a wear limit specified anywhere in Mooney literature? (2) If/when the block is changed, does the gear rigging tension change much? FYI -- the rectangular tab visible in the center of the uplock hole is the gear safe light switch. It toggles a microswitch to light the red and green gear indicator bulbs.

If you really want to save weight, buy a composite tank. They are super in volume-to-weight ratio. But they cost a lot; like a nice bicycle, you pay for the weight you don’t have to carry. Those old, low-tech 3AA series steel tanks are cheap. I have one with a 1960s manufacturing date. It has been hydro tested any number of times, most recently last week. It holds 50 cu feet and cost me $5 at a pilot swap meet plus a hydro test. Yes, it weighs 32 pounds, but it will give 40+ man-hours with an oxymizer at 12K feet. Cost to fill is $40 at the airport -- so that's $1.00 per hour. I go on O2 at 9000’ day and 5000’ at night. Yes, you can get your O2 bottle filled at the scuba or welding shop, but make sure they put in O2 and not air or Nitrox. No, that's not a joke -- I recall an accident report where the NTSB found the O2 bottle contained 21% oxygen, to wit, compressed air. Reference NTSB IAD97FA060.

Maybe the question should be: Why are our airplanes so cheap? If Mooney produced a new M20C today, it would probably sell for at least $300K (in 2009 dollars) , not the $40K (in 2009 dollars) or so it is worth used, but heck, they're over 40 years old. If I were to buy vintage 1960's avionics they would be darn cheap, too (even in 2009 dollars they're worthless). My point is the obvious one -- we're putting new avionics into our antique airframes, and we should not compare a new-in-2009 radio with the used price of the old airframe. Elsewhere on this forum are some original Mooney factory invoices from the 1960s. It is interesting to see how much the optional avionics added -- more than 15% was not uncommon for a "full panel" with VOR, ADF and Brittain autopilot. At today's hypothetical M20C $300K base (in 2009 dollars) that woud be over $45K (in 2009 dollars) -- just about the price of a nice panel upgrade today.

Many steel O2 tanks can be recertified every 5 years indefinitely, at a test cost of $20 (current 2009 prices). Some lighter-weight steel tanks, and composite tanks have service life limits. In the USA, the DOT regulates these tanks: Type 3AA 1800 steel cylinders must be tested every five years. They have indefinite service life provided they pass inspection criteria. Type 3HT 1800 steel cylinders must be tested every three years, and they have a service life limit of 24 years, after which they must be destroyed. Type 3AL seamless aluminum cylinders require test every 5 years and generally have a 15-year service life. Composite cylinders (often Aluminum with Kevlar wrap) must be tested every three years and have a 15-year service life, after which they must be destroyed. Another point on O2 costs -- most shops charge a flat rate to fill your tank, be it large or small. So I have a big one, oxygen tank that is, and that makes my O2 at least twice as cheap per hour as the smaller tanks more commonly seen in portable systems.

I have significant but far from total hearing loss in both ears. So, I have a SODA - a Statement of Demonstrated Ability - issued by the FAA via my AME. It permits me to hold a Class II or III medical, and requires I use "hearing amplification devices" such as headsets or hearing aids when flying. It might be possible to get a SODA for Class I, I don't know, I never tried. Talk to your AME. The SODA is issued once, and you present it at each medical exam.

Voltage Regulation During Flight I recorded the voltage during a "typical" 45-minute flight in my M20C. The DVM recorded 2 samples per second; there are just over 5000 points in the first graph. Overall comments The generator is only "on line" when the engine is running >1600 RPM or so The voltage is noisy even in steady state conditions The voltage of the bus depends strongly on the applied load If you look closely -- see the "First 5 Minutes" expanded graph -- you can see the mag checks which reduced the RPM from 1700 by about 100 RPM and the voltage about 1/2 volt. After run-up, back to 1000 RPM and the voltage fell back to ~ 12 V. During flight I turned on various loads -- for example, at 15:44 local time I turned on the landing light (250W) and the voltage dropped. At 15:49 I turned the landing light off and the voltage increased again. Background Information Voltage was measured at the radio master bus The plane has original-type 50A generator It has an original-style mechanical voltage regulator I notice that the battery appears to be reaching full charge only near the end of 45 minutes of flight -- fully charged is a voltage of about 2.35 volts per cell for a lead-acid battery, or 14.1 volts. Does anyone think that changing to the newer solid-state type generator regulator (Zeftronics, for example) will improve this situation and reduce the noise "hash" seen here?

One of the top assist springs broke on my M20E a few years ago. I noticed it right away as the manual gear forces increased greatly. I could still operate the gear but it took a real heave-ho to bring it up. It came down real fast, though.... Lasar at Lakeport CA had the spring in stock. They also have the Mooney tool -- a big long lever with the proper fittings -- to install the thing. I was happy to watch rather than help as it took two strong and experienced A&Ps about half an hour and a lot of hard pulling to get the new part installed.