Introduction
Effective Date: 15 June 98
Introduction
Stability and control and handling qualities testing have been combined into one section because they are so closely related. In many tests the data required to determine stability and control and handling qualities are obtained from the same maneuvers. Stability and control parameters are obtained from quantitative data analysis, and handling qualities data is determined primarily from qualitative data, i.e. pilot ratings and comments.
In modern aircraft using an active flight control system, it is often difficult or impossible to evaluate handling qualities characteristics directly from flight test data. Rather, the handling qualities are rated by the pilots using the Cooper-Harper rating technique. In addition, the aircraft responses to pilot inputs in flight are compared to an equivalent model which has know characteristics based on proven aircraft response parameters. These subjects will be discussed in some detail later.
This section will attempt to discuss, in brief, the techniques that are used to determine some of the more common stability and control parameters typically used in military and civilian aircraft specifications. Each section in the Test And Analysis Techniques section contains the following for a particular stability and control test:
A brief description and purpose for the requirement,
A description of the tests required to obtain the required data,
Data measurements required,
Data analysis and presentation.
The discussion in each of these sections is intended as a guideline only. For a detailed description of the requirements, test techniques, and analysis techniques it is suggested that the reader refer to the applicable system specifications, government requirements and listed references.
Abbreviations And Symbols
The following is a list of symbols and abbreviations that will be used throughout this section:
Speed:
VH - Maximum Attainable Level Speed
VM - Maximum Speed
VMC- Minimum Control Speed
VS - Stall Speed
Power Setting :
NRP - Normal Rated Power
MRP - Maximum Rated Power
PLF - Power for Level Flight
Symbols:
Alpa - Angle of Attack
Beta - Sideslip Angle
CG - Center of Gravity
dA - Aileron Deflection
de - Elevator Deflection
dR - Rudder Deflection
dPS - Pitch Stick Input
dRS - Roll Stick Input
dPED - Rudder Pedal Input
dT - Trim Input
Fa - Lateral (Roll) Stick Force
Fr - Rudder Pedal Force
FS - Longitudinal Stick Force
Fx - Engine Thrust
Theta - Pitch Angle
Psi - Heading Angle
Phi - Roll Angle
- Damping Ratio
- Damping Ratio for Dutch Roll
M - Mach Number
nz - Normal Acceleration
p - Roll Rate
q - Pitch Rate, or Dynamic Pressure
r - Yaw Rate
n - Undamped Natural Frequency
- Undamped Natural Frequency for Dutch Roll
Conventions
The following sign conventions will be maintained throughout this section:
Aircraft Axes:
X - Positive toward the front of the aircraft
Y - Positive toward the right side of the aircraft
Z - Positive Down
Aircraft Rotation:
Pitch - Positive is nose up
Roll - Positive is right wing down
Yaw - Positive is nose right
Control Surfaces:
da - Positive produces right roll
de - Positive produces nose down pitch
dr - Positive produces nose left sideslip
References
1. AFFTC Stability And Control Techniques, AFFTC-TN-59-21, N.D. Flack
2. MIL-F-8785, Flying Qualities Of Manned Aircraft
3. NASA TN D-5153, The Use Of Pilot Rating In The Evaluation Of Aircraft Handling Qualities, G.E. Cooper and R.P. Harper