B767 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 90; Flight Crew Total 10500; Flight Crew Type 5000
Confusion; Distraction; Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Aircraft; Weather
About 30 minutes after reaching cruise altitude; Captain and First Officer altimeters fluctuated as I've never seen in 23 years of flying this aircraft. The fluctuations were on the order of 20-60 feet most of the time; but at times it was 100-200 feet. The fluctuations were very rapid and directly proportional to turbulence intensity; the greater the turbulence intensity; the greater the fluctuation. The standby altimeter fluctuated 20-30 feet. The Captain and First Officer altimeters fluctuated independently.We were in RVSM airspace; but I was never in doubt that we were precisely maintaining our assigned altitude. The autoflight at no time 'chased' the altitude fluctuations. Our altitude relative to TCAS targets was as expected and ATC never queried our altitude. Before our flight; the aircraft was parked for several hours in a heavy blowing rain. It is possible that water incursion into the static ports may be a factor.
A B767 Captain reported that at FL360 in cruise both altimeter systems fluctuated independently in turbulence up to 200 FT after the aircraft was previously parked in heavy blowing rain for several hours. The aircraft remained stable during the repeated altimeter excursions.