- Joined
- Apr 13, 2017
- Messages
- 124
- Reaction score
- 33
Hi folks,
I have been fighting the " Stec porpoise ".
On all flights she is " dead level " for awhile... but acts up on every flight. The porpoise will progressively oscillate from +- 50 fpm to +- 500 fpm..and probably more if I let it go.... It's a wild ride ! Ironically on RNAV approaches it follows and holds the GS very well.
My Archer, ( 2001), has static ports on the rear sides of the fuselage. When recently searching for the Altitude Pressure Transducer , ( found it back by the fuselage static ports... ), I discovered all the tubing connecting the fuselage static ports were rotted and laying on the " belly ".
My understanding is the APT " monitors " the static system... and when I " lock up " an altitude on the 55X programmer it takes a " snap shot " of the APT " state " , using same as the reference to drive trim commands, ( I have auto trim ) , to maintain the selected altitude.( i.e. barometer )
Lastly... when I disable auto trim she flies level ....
Stec advises I send in my trim servo for overhaul $$$... but I'm thinking the APT / lack of static supply is more likely. Stec has been numb on my request for feedback on this potential source of the problem.
In any event has anyone dealt with this situation ?
Thanks !
I have been fighting the " Stec porpoise ".
On all flights she is " dead level " for awhile... but acts up on every flight. The porpoise will progressively oscillate from +- 50 fpm to +- 500 fpm..and probably more if I let it go.... It's a wild ride ! Ironically on RNAV approaches it follows and holds the GS very well.
My Archer, ( 2001), has static ports on the rear sides of the fuselage. When recently searching for the Altitude Pressure Transducer , ( found it back by the fuselage static ports... ), I discovered all the tubing connecting the fuselage static ports were rotted and laying on the " belly ".
My understanding is the APT " monitors " the static system... and when I " lock up " an altitude on the 55X programmer it takes a " snap shot " of the APT " state " , using same as the reference to drive trim commands, ( I have auto trim ) , to maintain the selected altitude.( i.e. barometer )
Lastly... when I disable auto trim she flies level ....
Stec advises I send in my trim servo for overhaul $$$... but I'm thinking the APT / lack of static supply is more likely. Stec has been numb on my request for feedback on this potential source of the problem.
In any event has anyone dealt with this situation ?
Thanks !
