João Oliveira - ULisboa · Flying Qualities João Oliveira Departamento de Engenharia Mecânica, Área Cientíﬁca de Mecânica Aplicada e Aeroespacial Instituto Superior Técnico

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


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.


Flying Qualities Control forces

Example of stick force limits


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)


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.


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.



Cooper Harper scale (2)



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.



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+



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.


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


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 —


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



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)



Flying qualities for the spiral mode

Minimum time-to-double amplitude

Class Flight Phase Level 1 (s) Level 2 (s) Level 3 (s)

I and IV A 12 12 4B and C 20 12 4

II and III All 20 12 4


João Oliveira - ULisboa · Flying Qualities João Oliveira Departamento de Engenharia Mecânica, Área Cientíﬁca de Mecânica Aplicada e Aeroespacial Instituto Superior Técnico

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