marooneypilot

Update on this topic, I was able to fly with another Mooney and do some airspeed indication comparisons during various phases of flight and confirm that my ASI is reading low. I’m now talking with the avionics shop that did the IFR cert about this and hoping they come to the table to resolve the problem.

That's my thought too. Thanks for confirming my thinking. And yeah, my analog gauge does match the aspen, and they are from the same pitot tube.

I had to change altitude to be at correct VFR altitude for direction. Given my location I wanted to be safe (9k feet 30 miles from a Charlie). I realize this has an effect on the validity of the tests. They did mess with the cowl flaps and brake line on the right main, but I had them swing the gear to make sure nothing was dragging (and that wouldn't explain the discrepancy between GS and TAS). And yes, landings are a little sporty since I'm fairly sure I'm coming in hot. I think next test is to go do some power on/off stalls and see what the indicated shows, although I suspect the error is lessened at lower airspeeds.

So after a bunch of trouble with the battery, I finally managed to get back in the air. Here are four photos from that flight, going in four different directions. The short version: Hdg 140: KIAS 113, GS 135 Hdg 320: KIAS 110, GS 169 Hdg 050: KIAS 115, GS 154 Hdg 230: KIAS 111, GS 147 The average GS is 151, but the TAS is always within a couple of knots of 135 according to the Aspen. This makes me think that the pitot static system is having issues as we suspected. I've asked the mechanic to have another look and see if anything was messed up during the annual. I have the logs back now, things they did: IFR cert on static system and transponder New air induction filter Cleaned and gapped spark plugs Complied with a fuel injection line AD Thoughts on how to proceed?

Thanks jaylw314 - glad it's not just mine Sounds like it's worth confirming the pitot is working by verifying the IAS/TAS readings against GPS - should be easy enough with a methodical flight test. Will do that and report back my results.

To clarify, I'm not referring to any add-on, this is a standard safety feature that is in all modern Mooneys. It is in the POH as the gear safety switch and is documented as being airspeed actuated. There is an alarm attached to it, which is annoying when you swing the gear on the ground. I'm not referring to the throttle actuated gear horn, which is a separate system. See the attached, this is the red button next to the gear lever

Thanks for the ideas folks! First off, I should be more specific. I said slow flight but didn't mean "Slow Flight". I noticed at towards the end of a chandelle (so still in high power, no flap, gear-up configuration) as the speed bled off below 70kias the gear safety horn would go off (fast beeping). There are two gear horns - one that is linked to airspeed (this ordinarily sounds when attempting to raise the gear too soon after takeoff, and can be overridden with the safety bypass switch next to the gear handle, sounds like a fast beeping), and one that is linked to throttle (this sounds when pulling the throttle to idle or near-idle with the gear still up, different intermittent beeping). These sound different in my aircraft, and it is the former that I am hearing when the airspeed is decreasing. This does not normally sound with the gear up - so something is amiss. It's definitely not the stall horn because the stall horn is a continuous tone, which this is not. Now, to the thoughts: Flaps - I can confirm these are fully retracted. Engine - I believe there was some work done around the turbo. I haven't got the full work log back but understand there were some fittings that were tightened. Engine sound - Engine sounds the same as normal. Indicated vs GPS - looking at the track log, and comparing eastbound vs westbound to account for wind, I'm seeing a wind-corrected GS of 139kts. This is barely higher than my regular indicated, so I'm fairly confident the plane is actually going slower. This is a good thought though - next flight I will do more deliberate investigation of this. Carusoam: I'm confident that the 70kts is _relatively_ accurate, or at least that I'm not flirting with the stall. For two reasons: I did this at altitude near the end of a chandelle, so I am familiar with how the plane starts to feel as it creeps into a stall (it wasn't mushing, wallowing, or buffeting), and the stall horn didn't go off. And I'm confident this isn't the gear-up warning since I was still pushing over 30" at this point. As far as I know the stall horn wasn't touched during annual, but P/S system was - got IFR cert done. 1) How can I know if I'm generating max power without hooking up a dyno? I can easily red-line (get to 37" and 2700rpm), and it "feels" lively on takeoff, not sluggish. 2) Will measure, but I'm lifting off at the same point on the runway as I always have 3) It's been bumpy here in central Texas, but as far as I can tell it's climbing more or less as usual (I never did get book in my plane) 4) I didn't calculate for DA, but it's hot here, so if anything I'd be expecting my TAS to be higher. 5) I believe so - both tower flyby, and mechanic gear swing confirmed looks good 6) Yes, flaps stowed fully 7) Step is down and welded 8) As expected 9) About 600 hours since overhaul on both the engine and turbo. Has the Merlyn wastegate, and airflow intercooler. 10) Good question - worth a recheck 11) TIT is in the same range as before 12) I have two TIT gauges, an engine analyzer with CHTs, and fuel flow. Using these in combination to set power as I did before I'm seeing all the same temps and flows. Their consistency makes me think that those readings are as reliable as they were before the annual. 13) Sadly, cannot download from my engine analyzer Sounds like I have to do a bit more digging around on the ground and in the air. I may also try an in-air mag-check and lean test and make sure that is all the same as before. Listing out all these answers though makes it sound like it's a drag thing. Could they have messed up the rigging during annual to cause this? David (Flying Piper speeds is not why I own a Mooney)

I just got my 231 back from annual and it isn't cruising as fast as it used to. Previously I would cruise at lower altitudes (6kish) at 130 kias, and true out close to 150. Faster as I went higher. This is on 32", 2400rpm and LOP around 9.7 gph. Now I'm seeing kias around 115 with the same power settings. First flight I noticed that in slow flight the gear safety horn would start beeping around 70 knots (as if I were trying to raise the gear too soon after takeoff). I did a low pass past the tower and they didn't see anything, and the shop swung the gear too and saw nothing out of the ordinary. What could be causing this reduction in cruise speed? David

First time to Oshkosh, first time in the caravan too (obviously).

So I tried the fix that @Cardinal767 suggested. PSA: The King servo is located in the starboard wing, one inspection panel outboard of the aileron pushrod. (I discovered this after looking all over the port-wing based on something else I'd read). Everything in there is strapped down and connected so tight that I can't imagine there was any poor connectivity, but I gave it all a wiggle anyway. I haven't had a chance to fly since trying Cardinal's trick, but will report my results here when I do. However I did have about a minute of perfect autopilot flight last weekend, so at least I know the problem is intermittent. David

Yeah, right up til the point your passengers start to turn green

On a recent flight, my autopilot has started performing small roll oscillations. Here's what I know: KFC 200 Yoke rotates about 5 degrees either direction, on about a 1-2 second period Happens in HDG mode and wings-level, haven't tried NAV or APCH Altitude mode and pitch-hold don't affect it Tried cycling the circuit breaker Happened on multiple flights I've read that it's possible this is a problem with the tachometer feedback from the servo to the AP computer. Does that sound likely? Anyone else experienced this or have other hypotheses? David

Worst I've had (so far, knock on wood) is alternator failure in VMC within 20 miles of my home airport.

Thanks @kortopates - fascinating stuff!

Interesting reasoning. I've never heard that reducing power (specifically MP) results in a leaner mixture - reduced fuel-flows, sure, but mixture is about ratio. Is there further reading you could point me to on that topic?