Hard Landing


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	HARD LANDING When the airplane contacts the ground during landings, its vertical speed is instantly reduced to zero. Unless provisions are made to slow this vertical speed and 8-32 cushion the impact of touchdown, the force of contact with the ground may be so great it could cause structural damage to the airplane. The purpose of pneumatic tires, shock absorbing landing gears, and other devices is to cushion the impact and to increase the time in which the airplane’s vertical descent is stopped. The importance of this cushion may be understood from the computation that a 6-inch free fall on landing is roughly equal, to a 340-foot-per-minute descent. Within a fraction of a second, the airplane must be slowed from this rate of vertical descent to zero, without damage. During this time, the landing gear together with some aid from the lift of the wings must supply whatever force is needed to counteract the force of the airplane’s inertia and weight. The lift decreases rapidly as the airplane’s forward speed is decreased, and the force on the landing gear increases by the impact of touchdown. When the descent stops, the lift will be practically zero, leaving the landing gear alone to carry both the airplane’s weight and inertia force. The load imposed at the instant of touchdown may easily be three or four times the actual weight of the airplane depending on the severity of contact. 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

HARD LANDING

When the airplane contacts the ground during landings, its vertical speed is instantly reduced to zero. Unless provisions are made to slow this vertical speed and 8-32 cushion the impact of touchdown, the force of contact with the ground may be so great it could cause structural damage to the airplane.

The purpose of pneumatic tires, shock absorbing landing gears, and other devices is to cushion the impact and to increase the time in which the airplane’s vertical descent is stopped. The importance of this cushion may be understood from the computation that a 6-inch free fall on landing is roughly equal, to a 340-foot-per-minute descent. Within a fraction of a second, the airplane must be slowed from this rate of vertical descent to zero, without damage.

During this time, the landing gear together with some aid from the lift of the wings must supply whatever force is needed to counteract the force of the airplane’s inertia and weight. The lift decreases rapidly as the airplane’s forward speed is decreased, and the force on the landing gear increases by the impact of touchdown. When the descent stops, the lift will be practically zero, leaving the landing gear alone to carry both the airplane’s weight and inertia force. The load imposed at the instant of touchdown may easily be three or four times the actual weight of the airplane depending on the severity of contact.

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