Learning Center Library Contents

Down Arrow
Welcome Guest
Aviation Learning Center Document AC 91-75 - Attitude Indicator
Author: Federal Aviation Administration Date: June 2003
used for alignment
used for alignment
Viewing Options: View Document as Chapters Chaptersused for alignment View Full Document Full Documentused for alignment View Print-Friendly Document Printer Friendlyused for alignment Search Inside this Document Search Insideused for alignment View PDF Version of Document PDFused for alignment

< Previous Chapter used for alignment Next Chapter > used for alignment

5. Rationale for Change
used for alignment

a. Substituting a second attitude indicator (with a power source independent from the primary attitude indicator) for the rate-of-turn indicator will provide an increased level of safety. It will replace a gyro that only indicates direction and rate of turn with one instrument that presents turn direction, bank angle, and pitch attitude information. Also, a second attitude indicator will be less confusing during partial panel operations because it presents pitch and bank information in the same manner as the primary attitude indicator. The pilot's scan and instrument interpretation during partial panel operations becomes easier because pilots will still be able to rely on an attitude indicator for pitch and bank reference just as they did during full panel operations. Recognition time that a failure condition exists will be equivalent to current system configurations.

b. Replacing the rate-of-turn indicator will mean losing an easy reference for standard rate turns. However, in today's air traffic control system, there is little need for precisely measured standard rate turns or timed turns based on standard rate. Maintaining a given bank angle on the attitude indicator for a given speed will result in a standard rate turn. Pilots using this AC to substitute an attitude indicator for their rate-of-turn indicator are encouraged to know the bank angle needed for a standard rate turn.

NOTE: The FAA preamble language for the 1970 amendment to section 91.33, re-codified to section 91.205, states: "[T]he FAA believes, and all other commenters apparently agree...the rate-of-turn indicator is no longer as useful as an instrument which gives both horizontal and vertical attitude information."

used for alignment