Downhill descent control

Does anyone know the details around how the downhill descent control works? Mine seems to allow some strange behaviours, like allowing the car to build up speed when you dont want it to and really letting go on loose steep sections - again when you dont want it to. Some dangerous moments experienced and I am now too scarred to use it.

I take it you mean the yellow Hill Decent Control button

This is from the Owners Manual of a Discovery TD5, you don't mention what vehicle you have

HILL DESCENT CONTROL
Hill Descent Control (HDC) operates in conjunction with the anti-lock braking system to provide greater control in off-road situations particularly when descending severe gradients.
To select HDC
HDC can be selected with the vehicle in any gear, but will only operate when low range gears are engaged with the vehicle travelling at less than 50 km/h, and the clutch is engaged (manual gearbox vehicles).
Press the switch (illustrated above) to select HDC.
If low range gears are engaged, the HDC information light (GREEN) on the instrument panel will illuminate (if low range gears have NOT been selected, the light will flash).
To deselect HDC, press the switch a second time (the information light will extinguish and a single warning sound will chime).
Hill descent control in action During a descent, if engine braking is
insufficient to control the vehicle speed, HDC (if selected) automatically operates the brakes to slow the vehicle and maintain a speed relative to the selected gear and the accelerator pedal position.
When driving off-road, HDC can be permanently selected, to ensure that control is maintained whenever low range gears are engaged. ABS and traction control are still fully operational and will assist if the need arises.
NOTE: With HDC selected, gear changes can
be carried out in the normal way.
If the brake pedal is depressed when HDC is active, HDC is overridden and the brakes will perform as normal (a pulsation might be felt through the brake pedal). If the brake pedal is then released, HDC will recommence
operating if necessary.
If the clutch is depressed for longer than 3 seconds while HDC is operating, the HDC information light will flash. If, after 60 seconds the clutch is still depressed, the information light extinguishes and the HDC
’failure’ warning light flashes as the system gradually fades out (see ’HDC fade-out’).
In extreme circumstances, the HDC system may cause brake temperatures to exceed their pre-set limits. If this occurs, the HDC ’failure’ warning light (AMBER) will start to flash and the warning chime will sound continuously.
During this time HDC will function as normal.

Hope this helps

Thanks for the info, the operation I understand, but have my reservations about how safe it is. Sorry forgot to mention, I have a Disco II TD5 2002 ES and take it on serious off-road trips with our local Land Rover club. I have noticed on loose material and severe descents the car seems to "slip away" out of control - very scary, the brakes seem to "let the car go" and then grab and let go again until traction is regained - not good when you have a 200m drop on your side. I am not sure if this is normal or if something is wrong - the light stays on and indicates no failure. Any advice will be welcomed. I have resorted to not using it as low range first and some heavy braking feels safer.

Antman said:

I have noticed on loose material and severe descents the car seems to "slip away" out of control - very scary, the brakes seem to "let the car go" and then grab and let go again until traction is regained - not good when you have a 200m drop on your side.

Click to expand...

not even HDC can overcome the effects of gravity and tyres running out of grip

So it is pretty much a case of assessing the terrain and deciding if going down under manual control is better or if HDC is better. I suppose it's back to understanding your vehicle.