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Difficulty: Very hardSkid Control and Recovery

While driving a fully loaded combination vehicle on a descending, curved interstate off-ramp, a light rain begins to mix with accumulated road oils. Your engine retarder is fully engaged. Suddenly, the rear of your tractor begins swinging rapidly out to the right side of the lane. Which of the following is the most appropriate sequence of actions to regain control and prevent a tractor jackknife?

  1. Immediately depress the clutch to remove the braking force from the drive wheels, turn the steering wheel to the right, and anticipate the need to quickly counter-steer as the vehicle aligns.Answer
  2. B
    Turn off the engine retarder switch, turn the steering wheel to the left to counteract the swing, and apply steady pressure to the trailer hand valve.
  3. C
    Maintain engine retarder engagement to safely manage your descent speed, steer to the right, and lightly pump the service brakes.
  4. D
    Apply firm pressure to the service brakes to aggressively reduce your curve speed, disengage the clutch, and hold the steering wheel firmly in the straight-ahead position.

Answer

Immediately depress the clutch to remove the braking force from the drive wheels, turn the steering wheel to the right, and anticipate the need to quickly counter-steer as the vehicle aligns.
The correct sequence addresses both the mechanical cause and the physical dynamic of the skid. Depressing the clutch instantly neutralizes the engine retarder's braking torque on the drive axles, which is crucial for regaining rolling traction. Steering to the right follows the tractor's rear swing (steering into the skid) to bring the vehicle back into alignment, while anticipating a counter-steer prevents a secondary whiplash skid.

Step-by-Step Solution

1
Recognize the cause of the skid.
Identify that the engine retarder on a slippery, wet surface has caused a drive-wheel braking skid.
Light rain mixed with oil creates a very slick surface where retarder torque easily breaks traction.
2
Remove the braking force.
Depress the clutch immediately.
Pushing the clutch instantly disconnects the engine retarder from the drivetrain, allowing the drive wheels to roll freely and regain lateral traction.
3
Steer into the skid.
Turn the steering wheel to the right.
Because the rear of the tractor is swinging to the right, steering right points the front wheels in the direction the vehicle is moving, helping to push the tractor back in front of the trailer.
4
Prepare for a secondary skid.
Anticipate the need to counter-steer.
Once the vehicle snaps back into alignment, momentum often carries it into a skid in the opposite direction. Quick counter-steering prevents this oscillation.

Key Concept

Drive-Wheel Skid Recovery and Engine Retarder Management
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Topics

Skid Control and Recovery

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