TCAS II V7.1 Intro booklet

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T CAS RA ”Cl i mb” i s s u e d CPA AL I M AL I M T h r e a t RAs can be classified as positive (e.g., climb, descend) or negative (e.g., limit climb to 0 fpm, limit descend to 500 fpm). The term "Vertical Speed Limit" (VSL) is equivalent to "negative." RAs can also be classified as preventive or corrective, depending on whether own aircraft is, or is not, in conformance with the RA target altitude rate. Corrective RAs require a change in vertical speed; preventive RAs do not require a change in vertical speed. Figure 18. Selection of Non-Crossing RA Sense Due to aircraft climb performance limitations at high altitude or in some flap and landing gear configurations, an aircraft installation may be configured to inhibit Climb or Increase Climb RAs under some conditions. These inhibit conditions can be provided via program pins in the TCAS connector or in real-time via an input from a Flight Management System (FMS). If these RAs are inhibited, the RA Selection Criteria will not consider them in the RA selection and will choose an alternative upward sense RA if the downward sense RA does not provide adequate vertical separation. TCAS is designed to inhibit Increase Descent RAs below 1450 feet AGL; Descend RAs below 1100 feet AGL; and all RAs below 1000±100 feet AGL. If a Descend RA is being displayed as own aircraft descends through 1100 feet AGL, the RA will be modified to a Do Not Climb RA. The second step in selecting an RA is to choose the strength of the advisory. The strength of an RA is the degree of restriction placed on the flight path by a vertical speed limit (negative) RA or the magnitude of the altitude rate wanted for positive RAs. TCAS is designed to select the RA strength that is the least disruptive to the existing flight path, while still providing ALIM feet of separation. An exception introduced in Version 7.1 is noted below. A new feature was implemented in Version 7.0 to reduce the frequency of initial RAs that reverse the existing vertical rate of own aircraft. When two TCAS-equipped aircraft are converging vertically with opposite rates and are currently well separated in altitude, TCAS will first issue a vertical speed limit (VSL or Negative) RA to reinforce the pilots’ likely intention to level off at adjacent flight levels. If no response to this initial RA is detected, or if either aircraft accelerates (vertically) toward the other aircraft, the initial RA will strengthen as required. This change was implemented to reduce the frequency of initial RAs that reversed the vertical rate of own aircraft (e.g., displayed a climb RA for a descending aircraft) because pilots did not follow a majority of these RAs, and those that were followed, were considered to be disruptive by controllers. An exception to the “least disruptive RA” rule was introduced in Version 7.1. After TCAS Version 7.0 was introduced into the airspace, opposite initial responses to corrective VSL RAs (annunciated as “Adjust Vertical Speed, Adjust”) were identified. The correct response to an AVSA RA is always a reduction in vertical speed. Several encounters were observed where the pilot increased vertical speed, causing further reduction in separation between own aircraft and the intruder. In Version 7.1, all corrective VSL RAs requiring non-zero vertical rates (500, 1000, or 2000 fpm) are changed to VSL 0 fpm RAs before being displayed to the pilot and are annunciated as “Level Off, Level Off”. The VSL 0 fpm RA 30
is stronger than required, however this change was made to make the intention of the corrective VSL, i.e., a move toward level flight, unambiguously clear. Table 3 provides a list of possible advisories that can be issued as the initial RA when only a single intruder is involved in the encounter. Table 3 is derived from DO- 185B, Table 2-16. After the initial RA is selected, the CAS logic continuously monitors the vertical separation that will be provided at CPA and if necessary, the initial RA will be modified. Strengthening Advisories In some events, the intruder aircraft will maneuver vertically in a manner that thwarts the effectiveness of the issued RA. In these cases, the initial RA will be modified to either increase the strength or reverse the sense of the initial RA. Reversed sense RAs will be discussed separately. A VSL is strengthened by changing to a more restrictive VSL or to a positive Climb or Descend RA. A Climb or Descend RA is strengthened to an Increase Climb/Descent RA. An Increase Climb/Descent RA can 31
Page 2 and 3: Preface This booklet provides the b
Page 4 and 5: TCAS/TCAS Coordination.............
Page 6 and 7: One of the most important collision
Page 8 and 9: Operational Performance Standards (
Page 10 and 11: in 2003. To guarantee the effective
Page 12 and 13: transmitting extended squitters, it
Page 14 and 15: status of traffic can be derived by
Page 16 and 17: SPEED ALT L-NAV AP1 A/THR 360 FL 31
Page 18 and 19: Aircraft that are not equipped with
Page 20 and 21: Interference Limiting Interference
Page 22 and 23: Collision Avoidance Concepts Airbor
Page 24 and 25: 14 12 Range, Nautical Miles 10 8 6
Page 26 and 27: Protected Volume A protected volume
Page 28 and 29: The CAS tracker also uses the diffe
Page 32 and 33: RA Type Positive (Corrective) Posit
Page 34 and 35: there will be sufficient horizontal
Page 36 and 37: alert. TCAS aural annunciations wil
Page 38 and 39: also responding to a TCAS RA, do no
Page 40 and 41: Table 6. Recommended Phraseology fo
Page 42 and 43: environment. When the inclusion of
Page 44 and 45: Version 7.0. While unnecessary devi
Page 46 and 47: Summary TCAS II is a last resort ai
Page 48 and 49: KIAS LCD LED MDF MHz MOPS MTL NAS N
Page 50: TRANSPONDER, MODE C: ATC transponde

TCAS II V7.1 Intro booklet

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