The other day while returning from Fredrickton NB (great trip, no hassle from customs and got to see a lot of cool stuff), I was westbound out of Bangor ME at 8000 ft on the backside of a front. Weather was clear with some broken cumulus, very strong winds out of the north. While straight and level on Trutrak altitude hold, my airspeed slowly began to climb, from 160 IAS to 180 IAS. The altimeter and VSI never budged. After about 1 minute or so, airspeed went down to about 140 IAS. THat cycle began to smoothly and gradually repeat with a period of of about 3 minutes and repeated for about 15 minutes and slowly smoothed out. After close scrutiny, I did detect the nose rise about two degrees nose up above level during decelerations and drop 2 degrees nose low during accel up to 180. Speed changes were accompanied by appropriate groundspeed changes. Again, absolutely no changes in altitude or VSI. My theory was this gentle roller coaster ride was due to the Trutrak climbing and descending to maintain the barometric altitude as I tracked across closely packed isobars?? Does that seem plausible
Later on a second leg well west of the front, and in very calm air, the Trutrak held altitude and A/S prefectly.
Anyone else ever experience this?? When it first happened I thought I magically gained 20 Hp - or that my pitot system was some how failing - until I slowed backdown and then decelled. It was actually kinda cool. Wish the 180 knot cruise had stuck!!
Later on a second leg well west of the front, and in very calm air, the Trutrak held altitude and A/S prefectly.
Anyone else ever experience this?? When it first happened I thought I magically gained 20 Hp - or that my pitot system was some how failing - until I slowed backdown and then decelled. It was actually kinda cool. Wish the 180 knot cruise had stuck!!