AC 120-55C Air Carrier TCAS - Code7700

AC 120-55C 2/23/11Appendix 6NOTE: In some installations, the loss of information from other onboardsystems such as an inertial reference system (IRS) or Attitude HeadingReference System (AHRS) may result in a TCAS failure. Individualoperators should ensure their pilots are aware of what types of failures willresult in a TCAS failure.(c) An intruder aircraft within 380 feet AGL (nominal value) may or may not bedisplayed by your TCAS (i.e., declared to be airborne or on the ground, respectively) dependingupon whether the intruder is Mode S or ATCRBS Mode C equipped and whether yourTCAS-equipped aircraft is airborne or on the ground.(d) TCAS may not display all proximate transponder-equipped aircraft in areas ofhigh density traffic.(e) Because of design limitations, the bearing displayed by TCAS is not sufficientlyaccurate to support the initiation of horizontal maneuvers based solely on the traffic display.(f) Because of design limitations, TCAS will not track intruders with a VS in excessof 10,000 feet per minute (fpm). In addition, the design implementation may result in some shortterm errors in the tracked VS of an intruder during periods of high vertical acceleration by theintruder.(g) GPWS warnings and windshear warnings take precedence over TCAS advisories.When either a GPWS or windshear warning is active, TCAS aural annunciations will beinhibited.d. TCAS Inhibits.(1) Objective. To verify the pilot is aware of the conditions under which certainfunctions of TCAS are inhibited.(2) Criteria. The pilot must demonstrate knowledge and understanding of the variousTCAS inhibits including:(a) Increase descent RAs are inhibited below 1,450 (±100) feet AGL.(b) Descend RAs are inhibited below 1,100 (±100) feet AGL.(c) All RAs are inhibited below 1,000 (±100) feet AGL.(d) All TCAS aural annunciations are inhibited below 500 (±100) feet AGL. Thisincludes the aural annunciation for TAs.(e) Altitude and configuration under which Climb and Increase Climb RAs areinhibited. Know if your aircraft type issues climb and increase climb RAs when operating at theaircraft’s certified ceiling. If your aircraft type provides RA climb and increase climb commandsat certified ceiling, the commands are to be followed.Page 4