Dynamic Hydroplaning


Chapter 8—Approaches and Landings
Table of Contents Normal Approach and Landing Base Leg Final Approach Use of Flaps Estimating Height and Movement Roundout (Flare) Touchdown After-Landing Roll Stabilized Approach Concept Intentional Slips Go-Arounds (Rejected Landings) Power Attitude Configuration Ground Effect Crosswind Approach and Landing Crosswind Final Approach Crosswind Roundout (Flare) Crosswind Touchdown Crosswind After-Landing Roll Maximum Safe Crosswind Velocities Turbulent Air Approach and Landing Short-Field Approach and Landing Soft-Field Approach and Landing Power-Off Accuracy Approaches 90° Power-Off Approach 180° Power-Off Approach 360° Power-Off Approach Emergency Approaches and Landings (Simulated) Faulty Approaches and Landings Low Final Approach High Final Approach Slow Final Approach Use of Power High Roundout Late or Rapid Roundout Floating During Roundout Ballooning During Roundout Bouncing During Touchdown Porpoising Wheelbarrowing Hard Landing Touchdown in a Drift or Crab Ground Loop Wing Rising After Touchdown Hydroplaning Dynamic Hydroplaning Reverted Rubber Hydroplaning Viscous Hydroplaning	DYNAMIC HYDROPLANING Dynamic hydroplaning is a relatively high-speed phenomenon that occurs when there is a film of water on the runway that is at least one-tenth inch deep. As the speed of the airplane and the depth of the water increase, the water layer builds up an increasing resistance to displacement, resulting in the formation of a wedge of water beneath the tire. At some speed, termed the hydroplaning speed (VP), the water pressure equals the weight of the airplane and the tire is lifted off the runway surface. In this condition, the tires no longer contribute to directional control and braking action is nil. Dynamic hydroplaning is related to tire inflation pressure. Data obtained during hydroplaning tests have shown the minimum dynamic hydroplaning speed (VP) of a tire to be 8.6 times the square root of the tire pressure in pounds per square inch (PSI). For an airplane with a main tire pressure of 24 pounds, the calculated hydroplaning speed would be approximately 42 knots. It is important to note that the calculated speed referred to above is for the start of dynamic hydroplaning. Once hydroplaning has started, it may persist to a significantly slower speed depending on the type being experienced. Previous \| Next
Copyright 2012 PED Publication

Chapter 8—Approaches and Landings

Table of Contents
Normal Approach and Landing
    Base Leg
    Final Approach
    Use of Flaps
    Estimating Height and Movement
    Roundout (Flare)
    Touchdown
    After-Landing Roll
    Stabilized Approach Concept

Intentional Slips
Go-Arounds (Rejected Landings)
    Power
    Attitude
    Configuration
    Ground Effect

Crosswind Approach and Landing
    Crosswind Final Approach
    Crosswind Roundout (Flare)
    Crosswind Touchdown
    Crosswind After-Landing Roll
    Maximum Safe Crosswind Velocities

Turbulent Air Approach and Landing
Short-Field Approach and Landing
Soft-Field Approach and Landing

Power-Off Accuracy Approaches
    90° Power-Off Approach
    180° Power-Off Approach
    360° Power-Off Approach

Emergency Approaches and Landings (Simulated)

Faulty Approaches and Landings
    Low Final Approach
    High Final Approach
    Slow Final Approach
    Use of Power
    High Roundout
    Late or Rapid Roundout
    Floating During Roundout
    Ballooning During Roundout
    Bouncing During Touchdown
    Porpoising
    Wheelbarrowing
    Hard Landing
    Touchdown in a Drift or Crab
    Ground Loop
    Wing Rising After Touchdown

Hydroplaning
    Dynamic Hydroplaning
    Reverted Rubber Hydroplaning
    Viscous Hydroplaning

DYNAMIC HYDROPLANING

Dynamic hydroplaning is a relatively high-speed phenomenon that occurs when there is a film of water on the runway that is at least one-tenth inch deep. As the speed of the airplane and the depth of the water increase, the water layer builds up an increasing resistance to displacement, resulting in the formation of a wedge of water beneath the tire. At some speed, termed the hydroplaning speed (VP), the water pressure equals the weight of the airplane and the tire is lifted off the runway surface. In this condition, the tires no longer contribute to directional control and braking action is nil.

Dynamic hydroplaning is related to tire inflation pressure. Data obtained during hydroplaning tests have shown the minimum dynamic hydroplaning speed (VP) of a tire to be 8.6 times the square root of the tire pressure in pounds per square inch (PSI). For an airplane with a main tire pressure of 24 pounds,
the calculated hydroplaning speed would be approximately 42 knots. It is important to note that the calculated speed referred to above is for the start of dynamic hydroplaning. Once hydroplaning has started, it may persist to a significantly slower speed depending on the type being experienced.

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