Longitudinal Flying Qualities Criteria Robert Stengel, Aircraft Flight Dynamics MAE 331, 2016 Copyright 2016 by Robert Stengel. All rights reserved. For educational use only. http://www.princeton.edu/~stengel/MAE331.html http://www.princeton.edu/~stengel/FlightDynamics.html • Cooper-Harper Ratings • MIL-F-8785C criteria • Normal load factor • CAP, C*, and other longitudinal criteria Learning Objectives 1 Review Questions ! What is the advantage of using one 4 th -order model over using two 2 nd -order models for analysis? ! What are gain and phase margins? ! What is a Nichols chart? ! What are some general characteristics of a pilot’s feedback control effects on aircraft dynamics? ! What are the principal dynamic effects of thrust and power on longitudinal stability? ! How are angle-of-attack-rate effects different from pitch-rate effects? 2
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Longitudinal Flying Qualities Criteria!
Robert Stengel, Aircraft Flight Dynamics!MAE 331, 2016
Copyright 2016 by Robert Stengel. All rights reserved. For educational use only.http://www.princeton.edu/~stengel/MAE331.html
•! Cooper-Harper Ratings•! MIL-F-8785C criteria•! Normal load factor•! CAP, C*, and other longitudinal
criteria
Learning Objectives
1
Review Questions!!! What is the advantage of using one 4th-order model
over using two 2nd-order models for analysis?!!! What are gain and phase margins?!!! What is a Nichols chart?!!! What are some general characteristics of a pilot’s
feedback control effects on aircraft dynamics?!!! What are the principal dynamic effects of thrust
and power on longitudinal stability?!!! How are angle-of-attack-rate effects different from
pitch-rate effects?!
2
Design for Satisfactory Flying Qualities•! Satisfy procurement requirement (e.g., Mil
Standard)•! Satisfy test pilots (e.g., Cooper-Harper ratings)•! Avoid pilot-induced oscillations (PIO)•! Minimize time-delay effects•! Time- and frequency-domain criteria
3
!SP
!nSP
4Robert Harper,
Cornell Aero Lab
Short-Period Bullseye or Thumbprint
Cooper-Harper Handling Qualities !Rating Scale
NASA TN-D-5153,19695
MIL-F-8785C Identifies Satisfactory, Acceptable, and Unacceptable Response Characteristics
Damping Ratio
Step Response
Frequency Response
Short-period angle-of-attack response to elevator input
6
Military Flying Qualities Specifications, MIL-F-8785C
•! Specifications established during WWII •! US Air Force and Navy coordinated efforts
beginning in 1945•! First version appeared in 1948, last in 1980•! Distinctions by flight phase, mission, and aircraft
type•! Replaced by Military Flying Qualities Standard,
MIL-STD-1797A, with procurement-specific criteria
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MIL-F-8785C Aircraft TypesI." Small, light airplanes, e.g., utility aircraft and
primary trainersII." Medium-weight, low-to-medium
maneuverability airplanes, e.g., small transports or tactical bombers
III." Large, heavy, low-to-medium maneuverability airplanes, e.g., heavy transports, tankers, or bombers
IV. " Highly maneuverable aircraft, e.g., fighter and attack airplanes
frequency–! Lower short-period damping–! Reduced time delay in DFCS–! CHR = 2 Input frequency,
rad/s
13 dB Gain
Margin
25
YF-17 Landing Approach Simulation
Next Time:!Advanced Problems of Lateral-
Directional Dynamics!
26
Fourth-order dynamicsSteady-state response to control
Transfer functionsFrequency response
Root locus analysis of parameter variations
ResidualizationRoll-spiral oscillation
Learning Objectives
Flight Dynamics!595-627!
Supplemental Material
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Large Aircraft Flying Qualities•! High wing loading, W/S•! Distance from pilot to rotational center•! Slosh susceptibility of large tanks•! High wing span -> short relative tail length
–! Higher trim drag–! Increased yaw due to roll, need for rudder
coordination–! Reduced rudder effect
•! Altitude response during approach–! Increased non-minimum-phase delay in
response to elevator–! Potential improvement from canard