- Published: Sunday, 28 December 2014 11:48
- Written by Lance Hartley
Taken from: Monaro RFS (Courtesy: Mike Holton)
The correct procedure for heavy vehicle stall recovery is detailed in the Rural Fire Service Specialist Training Manual: Rural Fire Driving at paragraphs 9.6.2 and 9.6.3. The procedure is also instructed as a component of the Rural Fire Driving Course.
The following paragraphs have been extracted from the Rural Fire Service Specialist Training Manual.
Before you contemplate driving off road, particularly in steep country, it is important to consider how to get yourself out of difficult situations. Perhaps the most common difficulty encountered is where the vehicle is negotiating a steep slope (greater than 25 degrees), and either loses traction or stalls. If the vehicle stalls and remains stationary you need to know your way out of this potentially dangerous situation. If the vehicle loses traction or stalls and starts to roll back, you have a slightly different and even more dangerous problem, but still need to make a recovery.
The procedure to be adopted is called "Stall Recovery". It is covered now because you should know the principles before you find yourself in such a situation. These procedures may not be suitable for vehicles with automatic locking hubs.
Note: It is NSW Rural Fire Service policy that, as part of 4WD techniques, Stall Recovery should only be taught by a certified 4WD Instructor.
When it becomes apparent that the vehicle will not make the climb, gradually allow the engine revs to die.
Apply the foot brake, do not use the clutch, allow the engine to "stall-out" in gear, keep your foot on the foot brake.
Note: With some vehicles the motor will continue to run even though the vehicle is stopped and in gear; this indicates a slipping clutch. In such situations switch off the motor, do not use the clutch.
If during any of the above, the vehicle starts to roll backwards down the slope, gently apply the brakes and bring the vehicle to a stop.
- Do not use the clutch.
- Do not make violent or sharp wheel movements.
- Do not use the hand brake (usually works on rear wheels only).
- At this stage, the vehicle should be stationary, in 1st gear, motor off and your foot on the foot brake.
Stop and think, the vehicle will not move so take your time.
Before attempting any recovery action, check to the rear to ensure that no personnel or vehicles are behind you.
If all clear behind the vehicle:
While keeping your foot firmly on the foot brake gently ease the clutch in. The purpose of this exercise is to test the holding ability of the vehicle's brakes. If the vehicle starts to roll back against the brakes, let the clutch out immediately,
If the foot brake holds, with the clutch depressed, de-select 1st gear and select reverse gear in one movement, and release the clutch immediately. Keep hand pressure on the gear lever as reverse gear may not have fully engaged.
If reverse gear is baulked do not use the clutch, hold the gear lever against the reverse gear gate and flick the starter switch. reverse gear should select, do not start the motor.
Gently ease your foot off the foot brake, but keep the brake pedal "covered". The vehicle should now be in reverse gear and held by engine compression. (Petrol powered vehicles may start their engines at this stage. This is normal, control the descent as per step 5 below).
When ready to descend the slope, without using the clutch and keeping one hand on the steering wheel, flick the starter switch, the motor should start and act as a brake as the vehicle descends the slope.
Control your descent by gentle brake applications.
- Do not use accelerator.
- Do not use clutch.
- Do not lock up the wheels.
Note: Sometimes the engine will start at step 4 above and the vehicle will start to move back down the slope. If this occurs use the foot brake gently to control your decent as in step 5 above.
In step 1 above, if the foot brake does not hold, you are in a serious situation which may require the assistance of a recovery vehicle.
If, on easing the clutch as in step 1 above, the vehicle starts to roll backwards, let out the clutch immediately as the vehicle's brakes are not capable of holding the vehicle stationary on their own.
The Mitsubishi Canter 4x4 Category 7 fire tanker may not hold on the foot brake alone under these conditions. With this vehicle it may be necessary to use the parking (hand) brake, which operates on the vehicle's transmission. Apply the handbrake then ease the clutch in to test that the vehicle is holding on brakes alone. If the brakes hold, proceed as in step 1 above. If the brakes do not hold, proceed as follows:
If you have someone with you, have them place chocks behind the wheels. Gently ease the clutch in; the vehicle should now hold with the foot brake and wheel chocks. Proceed as in step 2 above; the vehicle can be driven over the wheel chocks.
If the wheel chocks do not hold, or if you are alone, you are in an extremely dangerous situation. You should:
Leave the vehicle in 1st gear with the footbrake firmly applied. Gently ease the clutch in a little (feather the clutch), to allow the vehicle to move backwards a short distance (0.5m) or less then, let the clutch out to stop the descent, do not fully depress the clutch.
Continue the process of easing and releasing the clutch to control your descent keeping the foot brake firmly applied the whole time until you reach a level enough area for the vehicle to be parked safely. This process is not an exercise in vehicle sympathy, but is an extension of considering life before property. Your life is more important than the vehicle.
Extreme caution must be observed in situations as described above, and all drivers must be aware that there is the potential for an accident even if the correct procedure has been adopted.
Stall recovery procedure may also be employed where it has been necessary to stop a vehicle descending a steep slope.
Under these circumstances you should already be in 1st gear. To start, gently ease your foot off the brake, if the motor starts, gently control your descent with the foot brake, do not lock the wheels - do not use the clutch.
If the vehicle holds in 1st gear and the engine does not start, flick the starter switch, the motor should start, control your descent as in step 5 above.