Launch; Flying The Towfish - C-Max CM2 User Manual

CM2 Sidescan Sonar User Manual 5. Operating the Towfish
Using the Wing Depressor
If the optional wing depressor is used, refer to Section 18 for advice and important warnings.

Launch

Launch the towfish astern with the vessel preferably at slow speed.
DO NOT ALLOW ANY SLACK IN A WINCHED TOW CABLE during launch and whenever the towfish is in
the water. A slack cable can start to wind outside the winch drum. It can also form loops that can pull tight
and SERIOUSLY DAMAGE THE CABLE.
The "soft" tow cable can be handled without gloves but is still capable of giving friction burns if allowed to
slip.

Flying the Towfish

Set the display to show the water column (i.e not slant-range-corrected) then lower the towfish to an altitude
in the range 5-15m initially. The indicated altitude (not necessarily the true altitude at this stage) is shown in
MaxView's sonar parameters, or equivalent, and may also be also marked on the display by a pair of lines
overlying the initial bottom echoes.
Check that the altimeter is locked on the initial bottom echo, not on the surface echo, nor is left in a "neutral"
position.
IF THE ALTIMETER INITIALLY FAILS TO LOCK ON TO THE BOTTOM CORRECTLY USE THE FORCE
UP – DOWN CONTROL TO PUSH IT INTO LOCK.
Locking the Bottom-Tracking after Launch
Towfish – Bottom-Tracking Altimeter
In MaxView the bottom-tracking control is (or in early versions).
The indicated altitude cannot exceed 20m for EF operation, 40m for HF, and 60m for LF. If the towfish is
operated above these maximum altitudes, the image may be degraded; also the altimeter may try to lock on
to surface echo instead of the bottom.
Minimum indicated altitude is 1.4m. MaxView and other acquisition programs may sound an alarm if the
altitude falls below a preset value.
Version 3.6 (2008)
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