Operationally, those skills addressed and the guidance provided on TCAS training
in paragraph 9 should be followed and implemented by each operator electing to use TCAS II and
apply the appropriate 14 CFR.
b. Pilot Responsibilities.
TCAS is intended to serve as a backup to visual collision avoidance,
application of right-of-way rules, and air traffic separation service. For TCAS to work as designed,
immediate and correct crew response to TCAS advisories is essential. Delayed crew response or
reluctance of a flightcrew to adjust the aircraft’s flight path as advised by TCAS due to Air Traffic
Control (ATC) clearance provisions, fear of later FAA scrutiny, or other factors could significantly
decrease or negate the protection afforded by TCAS. Flightcrews are expected to respond to TCAS
in accordance with the following guidelines when responding to alerts:
(1)
Respond to TAs by attempting to establish visual contact with the intruder aircraft and
other aircraft which may be in the vicinity. Coordinate to the degree possible with other
crewmembers to assist in searching for traffic. Do not deviate from an assigned clearance based only
on TA information. For any traffic that is acquired visually, continue to maintain or attain safe
separation in accordance with current regulations and good operating practices.
(2)
When an RA occurs, the PF should respond immediately by direct attention to RA
displays and maneuver as indicated, unless doing so would jeopardize the safe operation of the flight
or the flightcrew can assure separation with the help of definitive visual acquisition of the aircraft
causing the RA. By not responding to an RA, the flightcrew effectively takes responsibility for
achieving safe separation. In so choosing, the following cautions should be considered:
(a)
The traffic may also be equipped with TCAS and it may maneuver in response to an
RA that has been coordinated with your own TCAS.
(b)
The traffic acquired visually may not be the same traffic causing the RA.
(c)
Visual perception of the encounter may be misleading. Unless it is unequivocally
clear that the target acquired visually is the one generating the RA and there are no complicating
circumstances, the pilot’s instinctive reaction should always be to respond to RAs in the direction
and to the degree displayed.
AC 120-55B 10/22/01
Page 8 Par 11
(3)
Satisfy RAs by disconnecting the autopilot, if necessary, using prompt, positive control
inputs in the direction and with the magnitude TCAS advises. To achieve the required vertical rate
(normally 1,500 feet per minute (fpm) climb or descent), first adjust the aircraft’s pitch using the
suggested guidelines shown in the table below. Then refer to the vertical speed indicator (VSI) and
make all necessary pitch adjustments to place the VSI in the green arc.
SPEED PITCH ADJUSTMENT
.80 MACH 2
°
250 KIAS below 10,000 feet 4
°
APPROACH below 200 KIAS 5
° to 7°
(a)
On aircraft with pitch guidance for TCAS RA displays, follow the RA pitch
command for initial, increase, and weakening RAs.
(b)
For TCAS to provide safe vertical separation, initial vertical speed response is
expected within 5 seconds of when the RA is first displayed. Excursions from assigned altitude,
when responding to an RA, typically should be no more than 300 to 500 feet to satisfy the conflict.
Vertical speed responses should be made to avoid red arcs or outlined pitch avoidance areas and, if
applicable, to accurately fly to the green arc or outlined pitch guidance area.
(4)
Respond immediately to any “increase” or “reversal” RA maneuver advisories. Initial
vertical speed response to an increase or reversal RA is expected by TCAS within 2 1/2 seconds after
issuance of the advisory. Again, avoid red arcs or outlined pitch avoidance areas and fly to the green
arc or outlined pitch guidance area.
(5)
The PNF should advise the PF on the progress of achieving the vertical rates commanded
by TCAS. The PNF and any on-board observers will assist in the visual search for the intruder and
continue to cross-check the TCAS displayed information with other available traffic information to
ensure the RA response is being flown correctly.
(6)
If an initial corrective RA is downgraded or weakened, such as a “climb” RA
downgraded to a “do not descend” RA, pilots should respond to the weakening RA and adjust the
aircraft’s vertical speed accordingly, but still keep the needle or pitch guidance symbol out of the red
arc or outlined pitch avoidance area. Pilots are reminded that attention to the RA display and prompt
reaction to the weakened RA will minimize altitude excursions and potential disruptions to ATC.
This will allow for proper TCAS-to-TCAS resolution of encounters and reduce the probability of
additional RAs against the intruder or other traffic.
(7)
Excessive responses to TCAS RAs are inappropriate and may increase interference with
other traffic and result in additional RAs.