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Roll Rate and Bank Angle Oscillations
Assessments are done in terms of normalized roll rate and bank angle oscillations for a step roll command input [23-26]. The roll rate oscillations should be kept to an absolute minimum. The requirements are based on the linear model of the aircraft. The roll rate and bank angle oscillation boundaries are defined. The roll rate at the first
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TABLE 10.6 LD Modes Specified Values |
Flight Phase Category |
Level 1 |
Level 2 |
Level 3 |
|
Time to double the roll angle should be |
A, C |
12 |
8 |
4 |
|
greater than |
B |
20 |
8 |
4 |
|
Zrsvrs |
B, C |
0.5 |
0.3 |
0.15 |
|
Equivalent roll time delay should be less than |
— |
0.1 |
0.2 |
0.3 |
|
Source: Shaik, I. and Chetty, S. HQPACK User’s Guide, Vols. 1, 2. PC based SW package in MATLAB ver 5.2 for the prediction of handling qualities and pilot induced oscillation tendencies of aircaft. NAL Project document, PD-FC-9810, December 1998. |
|
TABLE 10.7 DR Mode Parameters Specified Values
Source: Shaik, I. and Chetty, S. HQPACK User’s Guide, Vols. 1, 2. PC based SW package in MATLAB ver 5.2 for the prediction of handling qualities and pilot induced oscillation tendencies of aircaft. NAL Project document, PD-FC-9810, December 1998. |
minimum, following a step input, after the first peak should have the same polarity. It should not be less than the specified percentage of the roll rate of the first peak: For Level 1 Categories A and C 60%, for Category B 25%; and for Level 2 Categories A and C 5%, for Category B 0%. For bank angle HQ level boundaries are specified in Ref. [8].
10.4.2.3 Roll Performance
Roll performance is indicated by the time to achieve the specified roll angle change [6,8]. Certain requirements for various classes of aircraft are often specified (Table 10.8).
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TABLE 10.8 Time to Attain the Specified Change in Roll Angle for Classes I and II Aircraft Category A Category B Category C
Source: Shaik, I. and Chetty, S. HQPACK User’s Guide, Vols. 1, 2. PC based SW package in MATLAB ver 5.2 for the prediction of handling qualities and pilot induced oscillation tendencies of aircaft. NAL Project document, PD-FC-9810, December 1998. |
The pilot should be able to make certain necessary maneuvers and changes in the roll altitude. As far as possible the sideslip should be zero.
10.4.2.4 Sideslip Excursions
While making a turn, coordination between yawing and banking is required so that the aircraft does not ‘‘skid.’’ The pilot should be able to make precise changes in the heading. There should be minimum yaw coupling in roll entries/exits, and the sideslip excursions should be minimal. The pilot usually performs a coordinated turn. The required yaw control for coordination of turn entries and recoveries should not be objectionable to the pilot. The limits on the amount of the sideslip permitted after a small step roll command (up to the magnitude that causes a 60° roll angle within 2 s) are specified. The maximum sideslip excursions (during coordination in turn entry/exit) permitted are 6° for Level 1/Category A; 10° for Level 1/Categories B and C; and 15° for Level 2/all categories, for right roll command (this causes adverse beta). For left roll command (which produces the right sideslip/pro verse) the limits are 2° for Level 1/ Category A; 3° for Level 1/Categories B and C; and 4° for Level 2/all categories [6,8].
Unit step and pulse responses and the turbulence response of the aircraft are studied as is done in the case of the longitudinal mode. The idea is that these responses should be acceptable from the control point of view and the RMS value of the turbulence should be acceptable.
