This ppt contains an overview of different types of agility and their dynamics. Various examples are used to compare agility and super-maneuverability of aircraft.

1. High Agility Flight Dynamics and
Control of Aircraft
Guide
Prof. Ashok Joshi
By
Chirag Sadadiwala
163010045

2. Introduction
• Why Agility?
• Super-maneuverability is the
ability of an aircraft to fly in post
stall region.
• Post stall region is domain of
flight at high alpha.
• Agility is defined as the quick
movement of body or of mind.
𝐿 𝑣𝑠 𝛼 𝑎𝑛𝑑 𝐷 𝑣𝑠 𝛼.
[Patrick Le Blaye, HCAA Jan 2001]

3. Other definitions
• Ability to shift from one maneuver to other. [Ref. Col. Boyd]
• Ability to rapidly change both the magnitude and direction of the
aircraft velocity vector. [Ref. Northrop]
• Time rate of change of aircraft velocity vector. [Ref. MBB]
Total aircraft agility is a function of airframe, avionics, weapons,
and pilot.

4. Aspects of Agility
1. Airframe Agility
• Maneuverability
• Controllability
2. Systems Agility
3. Weapons Agility
4. Operational Agility
5. Transient Agility
Airframe Agility components
Patrick Le Blaye, HCAA, Jan 2001

5. Agility Metrics and Dynamics
• Agility metrics are measures of merit used to quantify the short-
timescale maneuvering capabilities of aircraft.
• Intended to quantify and influence the way fighter aircraft maneuver
are realized through a comparative study of the transient capabilities.
AOM;
Metric
Longitudinal Lateral Axial
Traditional Nmax STR T/W
Agility Pitch rate ∆𝑡 𝑅𝐶90° 𝑃𝑠
Traditional vs Metric
Aditya A. Paranjape and N. Ananthkrishnan, CAAM, 28 Dec 2005

6. Classification of Metrics
Timescale;
AOM
Transient
(1-3 sec)
Functional
(10-20 sec)
Potential
Lateral t90;
Torsional
Roll Reversal
Parameter
Lateral Agility
Criteria
Longitudinal Tmax; Tunload; Load
Factor Rate
Pointing Margin Pitch Agility
criteria
Axial POP; Power Loss CCT; DST;
Relative Energy
State
Agility
Potential
Classification of Metrics
Randall K. Liefer, John Valasek, David P. Eggold, and David R. Downing, Journal
of aircraft, Vol. 29, No. 3,June 1992.

7. Axial Agility Metric
• Axial agility is required to accelerate rapidly when the target is seen
and has to be intercepted within a limited time period.
Factors
• Measures the rate of change of excess power i.e. 𝑃𝑠
• Max. thrust available
• Engine spool time
• Large and positive 𝑃𝑠, gives higher agility.

8. Parameters to quantify axial agility.
1. Power Onset Parameter – POP
𝑃𝑂𝑃 =
∆𝑃𝑠
∆𝑡
=
𝑃𝑠𝑓 − 𝑃𝑠𝑖
𝑡𝑓 − 𝑡𝑖
• ∆𝑃𝑠 is the change in excess power in
going from min. power or max. drag to
max. power or min. drag.
POP Comparison
Aditya A. Paranjape and N. Ananthkrishnan, CAAM,
28 Dec 2005

9. 2. Power Loss Parameter
• Intended to measure the effectiveness and
response times of engine and drag
producing devices.
• Defined as
∆𝑃𝑠
∆𝑡
• But, ∆𝑃𝑠 is change in specific excess
power in going from a max. power to a
min. power configuration.
Power Loss Parameter
Randall K. Liefer, John Valasek, David P.
Eggold, and David R. Downing, Journal
of aircraft, Vol. 29, No. 3,June 1992.

10. Torsional Agility Metric
• Torsional agility is relative to the roll rate around the velocity vector,
with constant AOA and with zero sideslip.
• Roll rate about velocity vector gives better decoupling of flight path
and attitude at high AOA.
Torsional Agility
Patrick Le Blaye, HCAA, Jan 2001

11. • Torsional Agility is given by
𝑇𝐴 =
𝑇𝑢𝑟𝑛 𝑅𝑎𝑡𝑒
∆𝑡 𝑅𝐶90°
(𝑑𝑒𝑔/𝑠2)
• TA metric measures how well an
aircraft rolls when loaded.
• Low maneuverability increases
∆𝑡 𝑅𝐶90° at low roll rates.
• At high roll rates, aircraft is
maneuverable but less
controllability.
Aircraft A has higher TA than C,
when both are at higher turn rates.
TA Comparison
Andrew M. Skow, Eidetics Aircraft, Inc., (VOL. 29, NO. 1),
1992.

12. Lateral Agility Metric
• This is used when main objective of the pilot is weapon pointing and not
force vector orientation.
𝐿𝐴 =
1
∆𝑡 𝑅𝐶90°
(1/𝑠)
1. ∆𝒕 𝑹𝑪𝟗𝟎°
• measures the time taken by an aircraft
to roll through 90° starting from 0°.
F-5 has inferior roll performance than
that of F-18 and F-16.
∆𝑡 𝑅𝐶90° Comparison
Aditya A. Paranjape and N. Ananthkrishnan,
CAAM, 28 Dec 2005.

13. Longitudinal Agility Metric
• Longitudinal agility (pitch up) is the ability to rapidly point the nose of
the aircraft.
• Longitudinal agility (pitch down) is the required to quickly recover
speed, for instance after a shooting maneuver has been achieved.
Longitudinal Agility
Patrick Le Blaye, HCAA, Jan 2001

14. • High AOA reduces speed and increases the load factor.
• This rate of change of the load factor is called G onset. (15G/sec)
Average Pitch Rate Plot
Aditya A. Paranjape and N. Ananthkrishnan, CAAM, 28
Dec 2005.
• Two agile aircrafts F-16 and F-18
are studied to analyze the metric.
• F-18 is superior at low value of
Mach number and more agile.

15. Functional Agility Metric
1. CCT – Combat Cycle Time
• CCT is defined as the time taken to
accomplish a 180° heading change and then
return to the same Mach number.
CCT Concept
Aditya A. Paranjape and N. Ananthkrishnan, CAAM,
28 Dec 2005.
CCT Comparison
Aditya A. Paranjape and N. Ananthkrishnan, CAAM,
28 Dec 2005.

16. 2. Pointing Margin Metric
• Ability to point quickly at an adversary.
• This metric measures the angle between the
adversary’s nose and line of sight of
friendly aircraft at the moment when
friendly fighter is aligned with LoS as
shown in figure.
• A higher value of this metric indicates
better agility.
Pointing Margin
Aditya A. Paranjape and N. Ananthkrishnan,
CAAM, 28 Dec 2005.

17. Control Methods
• Handling qualities and control laws are very important for an agile
aircraft.
• No use of agility if the control system is sluggish and inaccurate.
• Some of the useful methods are given in subsequent section.
Control Structure
Joseph W. Pahle, Keith D. Wichman, John V. Foster, W. Thomas Bundick , HARV, NASA,1996.

18. Thrust Vectoring Vane Mixer
• The HARV produces multi-axis thrust vectoring using an experimental
thrust-vectoring system with six thrust-vectoring vanes.
• Vanes are interfaced with the flight control laws through a separate
function known as mixer.
• Control effectiveness of each vane is highly nonlinear, dependent on
engine parameters and flight condition.
• Independent of position of other vanes.
• This allows the control laws to be designed separately, with three
moment commands (pitch, roll, and yaw) rather than six vane
commands.

19. • The mixer adjusts the thrust-vectoring commands to account for
changes in thrust level and losses in thrust caused by thrust vectoring.
• Limits the commands as a function of flight condition to avoid
excessive structural loads.
Effect of TV on Pitch Rate
Patrick Le Blaye, HCAA, Jan 2001
Effect of TV on Roll Rate
Patrick Le Blaye, HCAA, Jan 2001

20. FCS - Flight Control System
• FCS plays a major role in reducing pilot workload by providing
appropriate handling qualities.
• Actuators limit the deflections of various control surfaces as well as
their rates.
• This restricts the maneuverability of the aircraft in flight regimes.
• Ex. Improvement of Lateral Agility of F-18.
Factors affecting
• Rudder saturation.
• Roll control surface deflection limits at high AOA.
• Rudder actuator rates.

21. • It was seen that increasing the three quantities helps reduce the time to
capture a 90° bank angle change.
• Hence improving lateral agility.
• FCS often makes the aircraft response somewhat sluggish (i.e.
excessive stability), which reduces maneuverability.
• So optimization of parameters is required.

22. Conclusion
• Agility is the need of hour.
• Expansion of flight envelope, performance in post stall region are the
key factors that decides agility.
• Agility metrics helps us to understand and quantify flight dynamics,
since it gives better results than conventional method.
• Advanced control laws and methods are used to achieve such
maneuverability and agility.
• Optimization of parameters are required to meet desired level of
agility and control.

23. References
1. Andrew M. Skow, “Agility as a Contributor to Design Balance”, Journal
of aircraft, (VOL. 29, NO. 1), 1992.
2. M. Dorn, “Aircraft Agility: The Science and the Opportunities”,
AIAA/AHS/ASEE Aircraft Design, Systems and Operations Conference
Seattle, WA / July 31 - August 2, 1989.
3. Patrick Le Blaye, “Chapter 2. Agility: history, definitions and basic
concepts”, “Human consequences of agile aircraft”, January 2001.
4. Aditya A. Paranjape and N. Ananthkrishnan, “Combat aircraft agility
metrics - a review”, 28 Dec 2005.
5. Randall K. Liefer, John Valasek, David P. Eggold, and David R.
Downing, “Fighter Agility Metrics, Research and Test”, Journal of
aircraft, Vol. 29, No. 3, May-June 1992.
6. Joseph W. Pahle and Keith D. Wichman, John V. Foster and W. Thomas
Bundick, “An Overview of Controls and Flying Qualities Technology on
the F/A-18 High Alpha Research Vehicle”, NASA 1996.

24. Thank you