LESSON: Structural Integrity and Velocity/Load Factor Chart

OBJECTIVE:

To develop the students understanding of Structural Integrity and the Velocity/Load Factor Chart

ELEMENTS:

 Load Factors and Airplane Design  Effect of Turns on Load factor  Effect of Load Factor on Stalling Speed  Effect of Speed on Load Factor  Effect of Flight Maneuvers on Load Factor  Effect of Turbulence on Load Factor  The Velocity/Load Factor Chart

SCHEDULE:

 60 Minutes Total

EQUIPMENT:

 Appropriate textbooks  Chalkboard & chalk  Model aircraft  Appropriate slides/Visual Aids

INSTRUCTORS ACTIONS:

 Discuss lesson objective

 Introduce the concept of Load Factors

 Discuss Effect of Turns on Load factor  Discuss Effect of Load Factor on Stalling Speed  Discuss Effect of Speed on Load Factor  Discuss Effect of Flight Maneuvers on Load Factor  Discuss Effect of Turbulence on Load Factor

 Discuss The Velocity/Load Factor Chart  Ask pertinent questions to determine students understanding  Assign appropriate study material

STUDENTS ACTIONS:  Listen, take notes, ask questions  Respond to instructors questions  Leave with a framework understanding of the subject

COMPLETEION STANDARDS:

The student should demonstrate adequate understanding of Structural Integrity and Load Factors by successfully completing an oral quiz or written exam

Introduction

Attention/Motivation

If you accidentally flew into moderate or greater turbulence what airspeed would you fly through it at? Would you do a 60º-bank turn to get out of it? An understanding of load factors is very important if you don’t know the answers to these questions

Overview

This lesson introduces the concept of Load Factors and the affects of different flight conditions on load factors

DEVELOPMENT

 Anytime an airplane changes its flight path (Climbs, descends, or banks) some loads imposed on the airplane  Loads on the airplane are caused by centrifugal force  Load Factor then is the ratio of the total load supported by the airplane’s wing to the actual weight of the airplane and its contents

( Actual load supported by the wings/Total Aircraft Weight )

 Load factor is expressed in G’s. The airplane is at 1 G in straight and level un- accelerated flight

Load Factors and Airplane Design

 All airplanes are designed to meet certain strength requirements depending upon the intended use  Three Categories: Normal (3.8 G’s), Utility (4.4 G’s), Acrobatic (6.0 G’s)  All airplanes must be certified to 50% beyond these values

Effect of Turns on Load factor

 The Load supported by the wings increases as the angle of bank increases  In a turn lift is divided into two components, Horizontal & Vertical  Airplanes turn because of the horizontal component of lift  Steeper the angle of bank the more horizontal component of lift is required  Load factor at 60º-bank is 2 G’s (Load Factor Chart: Load factor Vs. Bank Angle)

Effect of Load Factor on Stalling Speed

 Stalling speed and load factor are directly proportional: As Load factor increases the airplane will stall at a higher and higher airspeed  An airplane that has a normal 1 G stalling speed of 50 knots will be subject to a load factor of 4 G’s when stalled at 100 knots  Stall Speed Chart (Percent Increase In Stall Speed Vs. Bank Angle

Effect of Speed on Load Factor

 Increasing speed of an airplane increases the load factor  At high airspeeds abrupt movement can cause the wings to produce so much lift that structural damage occurs before the wings stall  Maneuvering Speed (Va) – Any airspeed at or below Va the wings will stall before they can produce enough lift to cause structural damage

Effect of Flight Maneuvers on Load Factor

 Straight and level, un-accelerated flight will always have a load factor of 1 G  Turns as previously discussed increase the load factor  Stall itself will produces a load factor toward zero  Stall recovery technique may produce positive or negative load factors  Advanced maneuvers- Spins, chandelles, lazy eights, Cuban eights, Immelmanns, etc are more airplane specific and the pilot should consult the Pilot Operating Handbook

Effect of Turbulence on Load Factor

 Turbulence is simply an abrupt change in the relative wind  Same effect as a sudden sharp control movements  Airplanes should be flown at or below Va when passing through turbulence

The Velocity/Load Factor Chart

 The Velocity/Load Factor Chart, also referred to as the V-n Diagram, shows the relationship between airspeed and load factor  It displays the airplane’s maneuver envelope  Top of the maneuver envelope is called the positive limit load factor (3.8 G’s).  This is the maximum load factor at which the plane should be flown, No structural damage below this

 Curved Line from Zero to Va represents the Maximum lift line or stall line  Any airspeed at or below Va the wing will stall before excessive loads are imposed  Vno – Structural consideration based on gusts, 50 feet per second. Only fly between Vno & Vne in smooth air  Vne – Designers use FAR’s determine where this point is based on wing loading and airplane category

CONCLUSION

 Airplanes are designed to meet certain strength requirements

 Load Factor increases with angle of bank  As Load factor increases so does stall speed  An Increase in airspeed increases the load factor  Straight and level, un-accelerated flight will always have a load factor of 1 G  Flying into turbulence increases load factor  V-n Diagram, shows the relationship between airspeed and load factor