User manual

B&G Hydra & Hercules User Manual
Part 3 - Commissioning and Calibration
HB-0842
3-23
3.4.14 Boat Lag Value
Boat Lag is the time taken for the boat to respond to changes in helm.
For example, heavy displacement hulls require a larger value for boat
lag.
3.4.15 Checking the Boat Lag
(1) Engage the autopilot as previously explained in Initial
Pilot Sea Trial.
(2) At a speed not exceeding 15 knots, change course
by 90
o
in each direction.
(3) Observe the autopilot steering performance. The
boat should turn onto the new heading with minimal
overshoot (a slight overshoot is acceptable).
(4) If the overshoot is consistently more than 5
o
for
course changes in both directions increase the Boat Lag
value in steps of 0.1 until the overshoot is corrected.
(5) It is easier to spot overshoot than undershoot, hence
if no overshoot is observed decrease the boat lag in steps of
0.1 until a small overshoot is seen. Use the smallest value of
Boat Lag to stop overshoot.
Boat Lag Value Correct Boat Lag Value
Incorrect (too small)
Fig 3.2 Boat Lag Response