Flying Qualities
João Oliveira
Departamento de Engenharia Mecânica,Área Científica de Mecânica Aplicada e Aeroespacial
Instituto Superior Técnico
Estabilidade de Voo, Eng. Aeroespacial
Versão de December 4, 2010
João Oliveira (ACMAA, IST) Flying Qualities Estabilidade de Voo 1 / 16
Summary
Flying QualitiesControl forcesClassification of airplanesFlight phasesFlying qualities levelsLongitudinal flying qualitiesLateral flying qualities
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Flying Qualities
Flying Qualities
Flying Qualities: those stability and control characteristicsimportant in forming the pilot’s impression of the airplane.
Factors that influence the pilot’s impression of theairplane:ñ Longitudinal and lateral dynamicsñ Stick forceñ Stick force gradients
The flying qualities expected by the pilot depend on thetype of aircraft and the flight phase.
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Flying Qualities Control forces
Example of stick force limits
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Flying Qualities Classification of airplanes
Classes of aircraft
Class I Small, light airplanes (such as light utility, primary trainer,and light observation craft)
Class II Medium-weight, low-to-medium maneuverability airplanes(such as heavy utility/search and rescue, light or mediumtransport/cargo/tanker, reconnaissance, tactical bomber,heavy attack and trainer for Class II)
Class III Large, heavy, low-to-medium maneuverability airplanes (suchas heavy transport/cargo/tanker, heavy bomber, and trainerfor Class III)
Class IV Heavy maneuverability airplanes (such as fighter/interceptor,attack, tactical reconnaissance, observation and trainer forClass IV)
(source: Nelson)
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Flying Qualities Flight phases
Flight phase categories
Category A Nonterminal flight phases that require rapid maneuvering,precision tracking or precise flight path control, such as air-to-air combat, in-flight refueling (receiver) , terrain-following,and close formation flying (applies only to military aircraft)
Category B Nonterminal flight phases that are normally accomplishedusing gradual maneuvers and no precision tracking, al-though accurate flight path control may be required. In-cludes climb, cruise, loiter, descent, in-flight refueling(tanker) and aerial delivery
Category C Terminal flight phases requiring gradual maneuvers but pre-cise flight path control. Include takeoff, catapult takeoff, ap-proach, wave-off/go-around, and landing.
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Flying Qualities Flying qualities levels
Cooper Harper scale
“Flying qualities: those stability and control characteristicsimportant in forming the pilot’s impression of theairplane.”
ñ To establish relationship between:ñ stability and control parameters of the airplane andñ the pilot’s subjective opinion
ñ the Cooper-Harper rating scale has been developed.
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Flying Qualities Flying qualities levels
Cooper Harper scale (2)
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Flying Qualities Flying qualities levels
Flying qualities levels
Flying qualities are usually defined in terms of the followingthree levels:
Level 1 Flying qualities clearly adequate for the missionflight phase
Level 2 Flying qualities adequate to accomplish the missionflight phase but with some increase in pilot work-load and/or degradation in mission effectiveness
Level 3 Flying qualities such that the airplane can be con-trolled safely but pilot workload is excessive and/ormission effectiveness is inadequate.
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Flying Qualities Flying qualities levels
Flying qualities levels
The flying qualities levels are related to the Cooper-Harper scaleas follows:
Level 1 Cooper-Harper scale = 1–3.5
Level 2 Cooper-Harper scale = 3.5–6.5
Level 3 Cooper-Harper scale = 6.5–9+
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Flying Qualities Flying qualities levels
Flying qualities levels and stability parameters
The stability and controlparameters (in this case,the natural frequencies anddamping ratio of the short pe-riod mode) can then be re-lates to the flight levels.
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Flying Qualities Longitudinal flying qualities
Flying qualities for the phugoid mode
Level 1 ζ > 0.04
Level 2 ζ > 0
Level 3 t2 > 55 s
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Flying Qualities Longitudinal flying qualities
Flying qualities for the short-period mode
Short-period damping ratio limits
Categories A and C Category B
Levels Minimum Maximum Minimum Maximum
1 0.35 1.30 0.30 2.00
2 0.25 2.00 0.20 2.00
3 0.15 — 0.15 —
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Flying Qualities Lateral flying qualities
Flying qualities for the roll mode
Maximum roll mode constant
Level
Flight phase category Class 1 2 3
A I, IV 1.0 1.4II, III 1.4 3.0
B All 1.4 3.0 10
C I, II-C, IV 1.0 1.4II-L, III 1.4 3.0
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Flying Qualities Lateral flying qualities
Flying qualities for the dutch-roll mode
Minimum dutch-roll frequency and damping
Levels Flight Phase Class Min ζ Min ζωn Min ωn
1 A I, IV 0.19 0.35 1.0II, III 0.19 0.35 0.4
B All 0.08 0.15 0.4
C I, II-CIV 0.08 0.15 1.0
II-L, III 0.08 0.15 0.4
2 All All 0.02 0.05 0.4
3 All All 0.02 — 0.4
(ωn in rad s-1)
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