PT20J

Just be aware that most of the rocker switches are also circuit breakers powered from the aux bus which is powered from a single breaker on the circuit breaker panel. So, unless you replace them with appropriately rated circuit breaker switches, you will need to do some rewiring and install additional circuit breakers somewhere.

Sounds like you are looking at the Lycoming altitude performance curves or the Aircraft Power app based on them. If so, those curves will overestimate power because they are based on test cell measurements with no exhaust system or induction system losses. You need to reference the POH power tables that are based on the airframe installation. Very doubtful you could get 85% at 6500’ (BTW, was this indicated or density altitude? What was the OAT?) Also, the fuel flow doesn’t sound high enough for that much power. Comparing the TAS to the POH should give you a check on power.

M20J SN-0001- 24-1037 had a wingspan of 35'. Thereafter, the wingspan is 36' 1" according to the SMM. The advantage of the wingtips is added recognition lights, and lower roll forces because the ailerons are moved inboard away from the tip vortices.

25 squared at 6500' is somewhere around 75% power. According to the IO-360 Operator's Manual Figure 3-6 it should burn about 73pph at 75% and 2500 rpm best power mixture which is about 100 dF ROP. This is 12.1 gph. So 11.7 at 50 ROP is in the ballpark. My M20J POH lists 10.4 gph for 75% at 2500 rpm at 25 dF ROP. So, again 11.7 gph at 50 ROP is in the ballpark. If it's running well, I wouldn't fret over it. Another check is that you should be getting around 18 gph +/- at sea level 2700 rpm and full throttle.

That sounds about right. The FF drops off when you go LOP if you keep MAP and rpm constant due to improved brake specific fuel consumption (gph/hp) because all the fuel is being burned as opposed to some being unburned ROP, and also because the engine is producing less power.

From my 1994 M20J

Good idea, Rick!!

I've never had one apart either. What I know comes from talking to people that have worked on them, reading articles about them and studying the service literature. There also used to be some good pictures on MS which were lost when we moved to the new server. I believe it is a wrap spring brake in one direction and a wrap spring clutch in the other. From the accident report descriptions, the failure mode that causes the gear not to extend is when one of the tangs breaks off and jams the actuator gear train so that it cannot rotate.

Might have been in another thread on this topic -- there are a lot of them RAM-B-408-75-1U handlebar mount RAM-B-201U-C Long arm RAP-B-202U Ball RAM-HOL-AP36U EZ Roll'r mount for iPad mini 6/7

You'll have to ask Don - I've never heard one make a noise.

As near as I can determine there was a catastrophic failure of an Eaton no-back spring about 25 years ago. Eaton recalled a bunch of actuators in 2002. I have never been able to find any documentation regarding the findings of the recall but there is a general belief (unsupported by evidence, but perhaps still true) that some springs may have been improperly manufactured. If any of those springs have never been replaced, they are probably not going to fail catastrophically or they would have by now. The spring acts a brake to prevent back driving (hence the descriptive name) the ball screw actuator and thus hold the retracted landing gear in the up position. Since it is a friction device, there will be some wear on it. Presumably when it completely wears out it will slip and the gear won't stay fully retracted, but that's conjecture. According to Don Maxwell, when the spring is wearing out it makes a distinctive chattering sound. This makes sense as it is probably beginning slip a bit. Anyway, Don's advice to me was that if it's not chattering, don't mess with it. There have been several catastrophic failures of the spring in the Plessey actuators (Plessey calls it a torsion spring, but Mooney tends to call the spring in both brands a no-back). The first two occurred at a little over 1000 hours and I believe that is likely the origin of the 1000 hr replacement interval. There are no parts available for the Plessey actuators and they seem be the units that fail and cause the gear ups.

I suspect that when they were new, the spring latch held the handle securely. But, after years of use (the emergency system is supposed to be tested annually) and perhaps people stepping on them, the tang gets bent a bit. Mine is pretty secure. If it seems loose, I'd just bend it back a bit to hold the handle more securely.

To my knowledge the best available drawing of the emergency retraction mechanism in the actuator is in chapter 32 of the Service and Maintenance Manual. The actuator has two drive systems that drive the same gear train which in turn rotates the ball screw to operate the landing gear: There is the normal motor and the recoil drive for the emergency gear extension. The recoil system is a one way ratcheting design; it can rotate the gear train to lower the gear but not raise it. There is a clutch to engage the recoil mechanism that is engaged by the lever in the cockpit. Because the recoil mechanism can only rotate in the down direction, it will stall the motor if the clutch is engaged and the gear is selected up electrically. The stalled motor draws excessive current and that pops the circuit breaker. If properly rigged, the coil spring located on the actuator clutch engagement arm should cause the lever in the cockpit to fully raise when it is unlatched which will in turn fully engage the clutch. If, for some reason the lever is not fully raised and the clutch is only partially engaged, operating the motor can damage the clutch mechanism. I don't know why replacing the cockpit lever to the locked position will not allow the motor to operate. Usually that clears the problem. But, given that these actuators cost several thousand dollars to repair and parts are in short supply, if it were mine, I would put it on jacks, remove the belly panel and carefully investigate the situation to determine what's hung up.

When the actuator breaker pops it's because the motor is jammed. Agree with @N201MKTurbo, but safest thing to do is to put it on jacks and work out the issue there with no loads on the gear.