Why? Cam doesn't track av when doing vertical loops.

Cameras follow the target when making sideways turning motions, but don't seem to when making up/down motions.
Eg: on an aeroplane; the camera follows nicely when turning left and right, but fails dismally when trying to do vertical loops.
Is there a way to make it follow behind the av at *all* times?

I believe this is a restriction with the viewer. try disabling camera constraints and see if that works.

If you're talking about while flying a vehicle yourself and the camera following you, you should be able to set those to be locked in behind the ship no matter which way it's going with llSetCameraEyeOffset and llSetCameraAtOffset

Good example can be found here:
http://lslwiki.net/lslwiki/wakka.php?wakka=llSetCameraEyeOffset

Using these will make it where the camera should stay exactly where you put it.

If you're setting the camera to be a bit more loose, then that will be using the more general camera params and would be a bit trickier, but should still be possible.

However, if you're talking about just tracking a plane someone else is flying by centering your view on it, then see the previous post regarding camera constraints.

Camera constraints: I disable these as soon as i log in.

The scenario is that I am in an aircraft, and the camera does not track me when doing steep vertical climbs and loops like it does any other time.
It's basically the standard HC-1 code I'm using btw - Kerian's HoverCar-1 'Halcyon'. And 'flight' (vector thrust as opposed to hover mode) is where the problem lies.
I have set all the camera params to be as tight as they can be. So unless it's something I'm missing, I just assume its a feature of normal cam behaviour.
...I'm hoping i'm overlooking something.

Here is the code i was using last time i was tinkering:
(for normal hover mode - works fine)
list drive_cam =
[CAMERA_ACTIVE, TRUE,
CAMERA_BEHINDNESS_ANGLE, 0.0,
// CAMERA_BEHINDNESS_LAG, 0.5,
CAMERA_BEHINDNESS_LAG, 0.0,
// CAMERA_DISTANCE, 4.0,
CAMERA_DISTANCE, 10.0,
CAMERA_PITCH, 10.0,
// CAMERA_FOCUS,
CAMERA_FOCUS_LAG, 0.05,
CAMERA_FOCUS_LOCKED, FALSE,
CAMERA_FOCUS_THRESHOLD, 0.0,
// CAMERA_POSITION,
// CAMERA_POSITION_LAG, 0.5,
CAMERA_POSITION_LAG, 0.0,
CAMERA_POSITION_LOCKED, FALSE,
CAMERA_POSITION_THRESHOLD, 0.0,
CAMERA_FOCUS_OFFSET, <0,0,3>
];


(for 'flight' mode - vector thrust/pure linear thrust flight - great until i do a vertical loop)
list jump_cam =[
CAMERA_BEHINDNESS_ANGLE, 0.0,
CAMERA_BEHINDNESS_LAG, 0.0,
CAMERA_DISTANCE, 10.0,
CAMERA_PITCH, 10.0,
// CAMERA_FOCUS,
CAMERA_FOCUS_LAG, 0.05,
CAMERA_FOCUS_LOCKED, FALSE,
CAMERA_FOCUS_THRESHOLD, 0.0,
// CAMERA_POSITION,
CAMERA_POSITION_LAG, 0.0,
CAMERA_POSITION_LOCKED, FALSE,
CAMERA_POSITION_THRESHOLD, 0.0,
CAMERA_FOCUS_OFFSET, <0,0,0>
];