pkofman Posted August 4, 2019 Report Share Posted August 4, 2019 So I'm flying along in the bravo ( m20m) and I notice in level flight that the altimeter is oscillating a bit ( maybe 15 ft up and down, think flickering rapidly up and down ) , clear day at about 5000 temps in the 20c range. I had never really seen that before ( or noticed ). I was not sure what was going on but then I noticed the rudder trim was way off. Not sure what I did next, except trim the rudder. Is it possible that if the rudder trim is way out that turbulent air at the static ports would create this effect . My guess is that is what happened but curious. Quote Link to comment Share on other sites More sharing options...
Yetti Posted August 4, 2019 Report Share Posted August 4, 2019 A sideways rain will put a fair amount of water in the static system. There should be a drain under the battery compartment. There should be an alt static valve above your left knee. Quote Link to comment Share on other sites More sharing options...
thinwing Posted August 4, 2019 Report Share Posted August 4, 2019 Also a second drain pilots side wing about mid way back. Quote Link to comment Share on other sites More sharing options...
OR75 Posted August 4, 2019 Report Share Posted August 4, 2019 Did you use the alternate static to see if it makes a difference ? Quote Link to comment Share on other sites More sharing options...
anthonydesmet Posted August 4, 2019 Report Share Posted August 4, 2019 6 hours ago, pkofman said: So I'm flying along in the bravo ( m20m) and I notice in level flight that the altimeter is oscillating a bit ( maybe 15 ft up and down, think flickering rapidly up and down ) , clear day at about 5000 temps in the 20c range. I had never really seen that before ( or noticed ). I was not sure what was going on but then I noticed the rudder trim was way off. Not sure what I did next, except trim the rudder. Is it possible that if the rudder trim is way out that turbulent air at the static ports would create this effect . My guess is that is what happened but curious. Not sure from your post but did fluctuation stop after you were all trimmed up? Then greatest percentage answer is yes - you were causing more unstable air with all the summer lifties. I kind of assume this might have been after level off in flight after climb so you had a lot of right trim/slip? Could have caused a differential. But going to stby will help you isolate next time. I’m sure your fine. Just make sure you drain before each flight. Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 5, 2019 Report Share Posted August 5, 2019 Long bodies get two static ports that should balance out the tail trim issue... might have a bit of a blockage in one side...? +1 See if any water drains out... static is the tail cone drain... Pitot drain is under the wing... +1 See if alt static valve makes a difference... +1 water is good for making needle wagging type errors... PP thoughts only, not an instrument guy.... Also search for water in static system for other MSer experience... one recent one and a couple of others... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
DXB Posted August 5, 2019 Report Share Posted August 5, 2019 My analog altimeter wags maybe 10ft in my M20C. So did the altimeter in my Piper trainer before I got my Mooney. So I thought this was normal. After seeing this thread, I opened my alternate static in flight today, and it made no difference. Same wag. My Aspen PFD dampens this wag. I'm guessing normal? Quote Link to comment Share on other sites More sharing options...
carusoam Posted August 5, 2019 Report Share Posted August 5, 2019 Dev, you can always check your static system’s dead leg... to see if anything has gotten in there. Often, it gets checked at annual... There may be a spec for allowable needle waggle... it may be age related... but not quite normal... Sounds like your Aspen is handling it well. Indicating the age of the mechanical altimeter to be a possible issue... probably easy to OH if desired... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Hank Posted August 6, 2019 Report Share Posted August 6, 2019 23 hours ago, carusoam said: Long bodies get two static ports that should balance out the tail trim issue... might have a bit of a blockage in one side...? +1 See if any water drains out... static is the tail cone drain... Pitot drain is under the wing... +1 See if alt static valve makes a difference... +1 water is good for making needle wagging type errors... PP thoughts only, not an instrument guy.... Also search for water in static system for other MSer experience... one recent one and a couple of others... Best regards, -a- My C has two static ports, just no tail trim to balance out, only slips. The only time I've had jssues with water in my static line was when a new IA did an annual, and apparently finished washing the plane while Imwas driving over to pick it up. The stall horn sounded as soon as I turned in the master, and his "fix" was to pull the breaker. That was the last time he touched my plane (Jan 2015). I used to religiously push both drains during preflight, but years of nothing even when parked outside in the rain has led to complacency. Guess it's time to recommit before something happens . . . . . 1 Quote Link to comment Share on other sites More sharing options...
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