Operational investigation of TCAS reports by pilots

Transcription

1 direction générale de l Aviation civile direction des services de la Navigation aérienne Operational investigation of TCAS reports by pilots Christian Aveneau, Bernard Hasquenoph & Beatrice Raynaud 1

2 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 2

3 TCAS RA reporting rate by pilots About half (48%) of / Descend RAs are reported Reporting of other RAs (that do not require deviation from ATC instruction or clearance) is lower (2%) RA onboard controlled flight / Descend RA Other RA Reported Not reported RAs of short duration are often not reported CIATM/C2336/N999/BR, version 1., 27 October 29 3

4 Timing of TCAS RA reports by pilots Shorter for / Descend RAs compared to Adjust Vertical Speed, Adjust RAs Half of these RA reports are within less than 1s after RA issuance (and two thirds within less than 15s) Median = 9s Median = 18s Number of aircraft simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s TCAS report after first RA onboard CIATM/C2336/N999/BR, version 1., 27 October 29 RAPositive_TCASRepFirst RAAdjust_TCASRepFirst s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s 4

5 Correctness of TCAS reports by pilots TCAS reports are not limited to RAs that require deviation from ATC instruction or clearance (even after November 27) / Descend RAs without report are sometimes not followed by pilots and often combined with pilot reports from threat aircraft For RAs other than / Descend RAs, TCAS reports often reflect pilot s response to RAs (regardless of applicable phraseology) CIATM/C2336/N999/BR, version 1., 27 October 29 5

6 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 6

7 Background (1/3) Carriage and operation of ACAS II by defined civil aircraft (cf. Phase 2 of European mandate for ACAS II, with implementation completion date of 31st March 26) For all civil, fixed-wing turbine-engined aircraft having a maximum take-off mass exceeding 57 kg or a maximum approved passenger seating configuration of more than 19 Change in ICAO provisions related to ACAS RAs (cf. ICAO Procedures for Air Navigation Services) applicable by end of November 27 New phraseology for TCAS RA reports by pilots (i.e. TCAS /descend replaced by TCAS RA ) Updated procedures to reduce likelihood of unsafe interaction between ACAS RAs and ATC clearances and instructions, as well as to limit controller s and pilot s workload and frequency load CIATM/C2336/N999/BR, version 1., 27 October 29 7

8 Background (2/3) When deviating from clearance, pilots have to report TCAS RAs to ATC as soon as possible (cf. ICAO Procedures for Air Navigation Services, November 27) Cf. PANS-OPS 3.2 c) in the event of an RA, pilots shall: 1) respond immediately by following the RA as indicated, unless doing so would jeopardize the safety of the aeroplane 2) follow the RA even if there is a conflict between the RA and an air traffic control (ATC) instruction to manoeuvre; 3) not manoeuvre in the opposite sense to an RA; 4) as soon as possible, as permitted by flight crew workload, notify the appropriate ATC unit of any RA which requires a deviation from the current ATC instruction or clearance; Cf. PANS-ATM When a pilot reports an ACAS resolution advisory (RA), the controller shall not attempt to modify the aircraft flight path until the pilot reports Clear of Conflict. CIATM/C2336/N999/BR, version 1., 27 October 29 8

9 Background (3/3) Automatic notification of ACAS RAs to controllers (based on RA downlink) seen as a potential element of a future overall coordinated concept for airborne and ground-based safety-nets Cf. FARADS (Feasibility of ACAS RA Downlink Study) RA Downlink can prevent the controller from issuing a clearance to an aircraft responding to RA; it reduces the amount of R/T during the RA encounter; it improves controller s awareness of the RA encounter; and it supports the prevention of follow-up conflicts. Cf. ICAO ACAS Manual In spite of the guidance given to flight crew, controllers should not assume that the pilot is obeying the RA. Nor should controllers assume that the RA information presented to them is current and correct, because ACAS can modify, and even reverse, the RAs, and there is an unavoidable delay in conveying RA information to controllers Already in operational use in Czech Republic Phase 1 initial operations: Information for ATCO RA in the label is used for ATCO information only. Responsibility for separation is on ATCO until PIC reports RA. However, ATCO should not give instructions contradictory to the RA direction. CIATM/C2336/N999/BR, version 1., 27 October 29 9

10 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 1

11 Context of the study (1/3) Performance and safety Aspects of STCA, full Study (PASS) Phase 1: Monitoring & understanding of current situation (28) Different levels of ANSPs contribution in Europe: Specific contribution of DSNA, skyguide and DFS Indirect contribution of other European ANSPs (UK, Denmark, Czech Republic, Ireland and Estonia) through public safety occurrences Set of (18) reported safety-net related occurrences with sufficient available data to analyse the sequence of events (i.e. STCA, TCAS, controllers and pilots events) Dated from September 27 to July 28 Cf. PASS/WA1/WP4/9/W STCA + RA 59 RA only 16 STCA only 15 CIATM/C2336/N999/BR, version 1., 27 October 29 11

12 Context of the study (2/3) Insight on TCAS reports by pilots (based on safety-net related occurrences with TCAS RAs) Cf. PASS/WA1/WP5/1/W Diversity of observed pilot reports Type of pilot report No report TCAS alert (with no other detail) Adjust vertical speed Higher reporting rate in single RA occurrences Maintaining current level 3 that in double RA occurrences (i.e. with Clear of conflict 2 coordinated RAs onboard both aircraft) Total 17 TA RA (with no other detail) Descent Count Single RA occurrence; own with RA Double RA occurrence; own with RA TA report; 1; 3% No report; 1; 3% No report; 15; 21% Over-estimate of RA reporting rate due to focus on reported RA occurrences! RA report; 35; 94% RA report; 55; 79% CIATM/C2336/N999/BR, version 1., 27 October 29 12

13 Context of the study (3/3) Set of (88) recorded TCAS RA occurrences (i.e. encounters with at least one RA) collected via RA downlink for specific analysis Dated from September 27 to March 28 Six Mode S radars in European Core Area (~ 1 33, flight hours) At least 16% of intentional TCAS RA occurrences (mainly due to military or flight threat aircraft) Cf. PASS/WA1/WP4/38/W 18 Mode A/C threat 29% Mode S threat 12% (no TCAS or inoperative TCAS) Ghost threat 7% TCAS threat in TA-only 2% TCAS threat (RA capable) with coordinated RA 17% TCAS threat (RA capable) without RA 33% Number of sequences with active RA all encounters intentional unintentional unknown duration (s) CIATM/C2336/N999/BR, version 1., 27 October 29 13

14 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 14

15 TCAS RA reporting rate (1) - General Which report rate of TCAS RA by pilots? Correlation of reported and recorded occurrences for one ANSP for which all TCAS RA occurrences have to be filed by Air Traffic Controllers (ATCO) when reported by pilots on the frequency Under-estimate of the TCAS RA reporting rate by pilots (in case of events not filed by ATCO or without Air Safety Report (ASR) from the pilot) Which key factors influencing RA reporting rate? Type of RAs, number of RAs, altitude of RAs, duration of RAs, other human, technical and environmental factors CIATM/C2336/N999/BR, version 1., 27 October 29 15

16 TCAS RA reporting rate (2) - General Recorded occurrences (via RA downlink in available Mode S coverage) RA outside ANSP area of responsibility RA onboard flights not controlled by civil ATC unit Not reported RAs with no deviation from ATC clearance Not reported climb/descend RAs etc Reported climb/descend RAs Other reported RAs Legend: ANSP: Air Navigation Service Provider ASR: Air Safety Report ATCO: Air Traffic Controller RA: Resolution Advisory TA: Traffic Advisory Reported occurrences (ATCO, ASR, Airprox) TA RA outside Mode S coverage RA without Mode S recording etc CIATM/C2336/N999/BR, version 1., 27 October 29 16

17 TCAS RA reporting rate (3) - General Recorded RA outside ANSP area of responsibility; 53 Recorded RA onboard flights not controlled by civil ATC unit; 113 Recorded RA onbaord controlled flight, but RA not reported; 31 Recorded RA onboard controlled flight and RA reported; 123 Less than one half (4%) of recorded RAs occurred onboard a controlled flight in ANSP area of responsibility, of which less than one third (29%) was reported to ATC (based on reported RA occurrences) CIATM/C2336/N999/BR, version 1., 27 October 29 17

18 TCAS RA reporting rate (4) - Type of RAs Which reporting rate of TCAS RA by pilots (of flights controlled by ANSP)? By correlating recorded RAs and reported RAs For positive RAs (i.e. and Descend RAs) For other RAs (i.e. Adjust Vertical Speed (AVSA), Maintain and Recorded RA for controlled flights 12 Monitor RA) Before Nov 27 1 After Nov 27 8 Before and after 6 November 27 4 (based on 2 recorded RAs) Descend Reversal AVSA Maintain Monitor CIATM/C2336/N999/BR, version 1., 27 October 29 18

19 TCAS RA reporting rate (5) - Type of RAs Reporting rate is greater for positive RAs (48%) than for other RAs (2%) that do not require deviation from ATC instruction or clearance or Descend RA AVSA, Monitor or Maintain RA Reported Not reported Same trend observed over the monitoring period (before and after November 27) Cl/Des RAs Mean: 5% Std dev: 1% Other RAs Mean: 25% Std dev: 8% 1% 8% 6% 4% 2% % 31 sept Reporting rate depending on time oct-7 nov-7 déc-7 janv févr-8 mars- 8 or Descend RAs AVSA, Maintain or Monitor RAs CIATM/C2336/N999/BR, version 1., 27 October 29 19

20 TCAS RA reporting rate (6) Type of RAs Positive RAs that require deviation from ATC instruction are not always reported (before and after November 27) Non-reported Cl/Des RAs Before Nov 27: 5% After Nov 27: 54% Reported RAs not limited to RAs that require deviation from ATC instruction (even after November 27) Reported RAs other than Cl/Des Before Nov 27: 17% After Nov 27: 22% Reported Not reported or Descend RA Reported Not reported or Descend RA Before November 27 After November 27 AVSA, Monitor or Maintain RA AVSA, Monitor or Maintain RA CIATM/C2336/N999/BR, version 1., 27 October 29 2

21 TCAS RA reporting rate (7) Number of RAs Which reporting rate of TCAS RA by pilots (of flights controlled by ANSP)? By correlating recorded RAs and reported RAs In single RA occurrences & double RA occurrences (based on recorded RAs) double- RA occurren ces; 51 For positive RAs (i.e. and Descend RAs) and other RAs (based on recorded RAs) single- RA occurren ces; 323 CIATM/C2336/N999/BR, version 1., 27 October 29 21

22 TCAS RA reporting rate (8) Number of RAs Regardless of type of RAs, reporting rate by individual pilots is four times greater in double RA occurrences (81%) than in single RA occurrences (21%) Likely because first RA reports prompt second RA reports (by the other pilot) No aircraft reports; 254 Both aircraft report; single-ra occurrences double-ra occurrences One aircraft reports; 69 For double RA occurrences, ATC got informed that at least one RA occurred in about three quarters (76%) of the occurrences No aircraft reports; 12 One aircraft reports; 24 Both aircraft report; 15 CIATM/C2336/N999/BR, version 1., 27 October 29 22

23 TCAS RA reporting rate (9) Number of RAs For and Descend RAs, reporting rate is greater in double RA occurrences (54%) than in single RA occurrences (35%) Single RA occurrences Reported Not reported or Descend AVSA, Maintain or Monitor Double RA occurrences For other RAs, reporting rate is three times greater in double RA occurrences (44%) than in single RA occurrences (16%) or Descend AVSA, Maintain or Monitor Reported Not reported CIATM/C2336/N999/BR, version 1., 27 October 29 23

24 TCAS RA reporting rate (1) Number of RAs For RA occurrences with at least one or «Descend» RA, ATC got informed in about three quarters (76%) of the cases, Double RA occurrences with at least one or Descend RA Only one aircraft with /Descend and both report 22% Both aircraft with /Descend and both report 8% Both aircraft with /Descend and none reports % Only one aircraft with /Descend and none reports 24% although both pilots reported in only one third (3%) of the cases Only one aircraft with /Descend and only it reports 19% Both aircraft with /Descend and one reports 16% Only one aircraft with /Descend and only the other reports 11% CIATM/C2336/N999/BR, version 1., 27 October 29 24

25 TCAS RA reporting rate (11) Other factors Are other RA characteristics influencing the reporting rate by pilots (for flights controlled by ANSP)? By correlating recorded RAs and reported RAs Effect of RA altitude and RA duration (based on recorded RAs) Altitude of recorded RAs Duration of recorded RAs AVSA, Maintain or Monitor RAs or Descend RAs AVSA, Maintain or Monitor RAs or Descend RAs 4 2 < FL5 FL5-FL1 FL1-FL15 FL15-FL2 FL2-FL25 FL25-FL3 FL3-FL35 FL35-FL45 CIATM/C2336/N999/BR, version 1., 27 October >5 25

26 TCAS RA reporting rate (12) Other factors For and Descend RAs, reporting rate increases with RA altitude and RA duration (both effects sometimes combined) Reporting rate depending on RA altitude 1% 8% 6% 4% 2% % < FL5 FL5-FL1 FL1-FL15 FL15-FL2 FL2-FL25 FL25-FL3 FL3-FL35 FL35-FL45 or Descend RAs AVSA, Maintain or Monitor RAs For other RAs, reporting rate seems not influenced by RA altitude and RA duration 1% 8% 6% 4% 2% % CIATM/C2336/N999/BR, version 1., 27 October 29 Reporting rate depending on RA duration >5 or Descend RAs AVSA, Maintain or Monitor RAs 26

27 TCAS RA reporting rate (13) Other factors Which primary factor influences the non-reporting of TCAS RA by pilots (for flights controlled by ANSP)? Human, technical and environmental factors (based on reported RA occurrences) Pilot has traffic information or avoidance instruction Pilot has reported visual acquisition Pilot has probably visual (RA at low altitude, or against VFR threat, not followed) Procedure is associated with frequent RAs (e.g. 1-ft level-off) Pilot not on frequency Frequency overloaded RA is spurious (e.g. self tracking, ghost intruder, RA on the ground) RA does not require deviation Unknown (e.g. pilot s stress, workload, ) CIATM/C2336/N999/BR, version 1., 27 October 29 27

28 P ilo th a stra fic in fo rma tio n o ra v o id a n c e in stru c tio n P ilo th a sv isu a l P ilo th a sp ro b a b lyv isu a l(lo w a ltitu d e,v F R th re a t) P ro c e d u re isa so c ia te d w ith fre q u e n tr A s R A isto o sh o rt P ilo tn o to n fre q u e n c y F re q u e n c yo v e rlo a d e d R A isp u rio u s R A d o e sn o tre q u ire d e v ia tio n U n k n o w n P ilo th a stra fic in fo rma tio n o ra v o id a n c e in stru c tio n P ilo th a sv isu a l P ilo th a sp ro b a b lyv isu a l(lo w a ltitu d e,v F R th re a t) P ro c e d u re isa so c ia te d w ith fre q u e n tr A s R A isto o sh o rt P ilo tn o to n fre q u e n c y F re q u e n c yo v e rlo a d e d R A isp u rio u s R A d o e sn o tre q u ire d e v ia tio n U n k n o w n TCAS RA reporting rate (14) Other factors Primary factor influencing the nonreporting of TCAS RA by pilots is different for positive RAs and other RAs, although some common influencing factors exist (e.g. procedure associated with frequent RAs, RA too short, pilots has probably visual) Pilot has traffic 8 information or avoidance instruction 4 Pilot has visual Pilot has traffic 4 information or avoidance 2 instruction Pilot has probably visual (low altitude, VFR threat) Procedure is associated with frequent RAs Procedure is associated with frequent RAs Pilot has probably visual (low altitude, VFR threat) Operational investigation of TCAS Pilot reports has visual by pilots, CIATM/C2336/N999/BR, version 1., 27 October 29 RA is too short Not reported or Descend RAs Pilot not on frequencyfrequency overloaded RA is spurious Unknown RA does not require deviation Not reported AVSA, Maintain or Monitor RAs RA is too short Pilot not on RA is spurious frequencyfrequency overloaded RA does not require deviation 28 Unknown

29 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS RA reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 29

30 Timing of TCAS reports (1) - General Which delay of TCAS reports by pilots (based on reported RA occurrences)? In single RA occurrences & double RA occurrences Effect of first TCAS reports on second TCAS reports (when present during double RA occurrences) Double RA occurrences ; 35; 49% Single RA occurrences ; 37; 51% Effect of traffic information or avoidance instruction from ATC (if any) on TCAS reports by pilots CIATM/C2336/N999/BR, version 1., 27 October 29 3

31 Timing of TCAS reports (2) - General Timing of (first or second) RA reports compared to time of first RA on board own aircraft is quite distributed simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s Number of aircraft Median: 16 seconds Mean: 23 seconds Std dev: 26 seconds (over 64 TCAS RA reports) > 12 s CIATM/C2336/N999/BR, version 1., 27 October 29 TCAS report after first RA onboard 31

32 Timing of TCAS reports (3) Second reports Timing of second RA reports (when present during double RA occurrences) is quite delayed compared to first RA reports likely due to frequency occupancy Median: 11 seconds Mean: 18 seconds Std dev: 22 seconds (over 49 first RA reports) Median: 29 seconds Mean: 42 seconds Std dev: 28 seconds (over 15 second RA reports) Number of aircraft simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s CIATM/C2336/N999/BR, version 1., 27 October 29 TCAS report after first RA onboard RA_TCASRepFirst RA_TCASRepSecond s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s 32

33 Timing of TCAS reports (4) Second reports For double RA occurrences, relative timing of second RA reports (when present) compared to first RA reports is quite distributed Number of aircraft Median: 22 seconds Mean: 31 seconds Std dev: 25 seconds (over 15 double RA occurrences) simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s Second TCAS report after first TCAS report CIATM/C2336/N999/BR, version 1., 27 October 29 33

34 Timing of TCAS reports (5) Type of RAs Is the type of RA onboard influencing the timing of first TCAS reports? Effect of positive RAs (i.e. or «Descend») Effect of «Adjust Vertical Speed, Adjust (AVSA)» RAs RA onboard own aircraft Monitor; 3; 3% Maintain; 1; 1% ; 34; 32% AVSA; 41; 39% Descend; 27; 25% CIATM/C2336/N999/BR, version 1., 27 October 29 34

35 Timing of TCAS reports (6) Type of RAs Timing of first RA reports is shorter for positive RAs ( or «Descend») than for «Adjust Vertical Speed, Adjust (AVSA)» RAs Median: 9 seconds Mean: 14 seconds Std dev: 15 seconds (over 32 Cl/Des RA reports) Median: 18 seconds Mean: 28 seconds Std dev: 3 seconds (over 16 AVSA RA reports) Number of aircraft simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s CIATM/C2336/N999/BR, version 1., 27 October 29 TCAS report after first RA onboard RAPositive_TCASRepFirst RAAdjust_TCASRepFirst s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s 35

36 Timing of TCAS reports (7) Effect of ATC Is ATC intervention influencing the timing of first RA reports (based on reported RA occurrences)? Effect of ATC intervention before or after RA onboard Effect of Traffic Information (TI) or Avoiding Action (AA) > 6 s s 54-5 s s 44-4 s s 34-3 s s 24-2 s s 14-1 s 9-5 s 4-1 s simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s AA before RA AA after RA > 6 s s 54-5 s s 44-4 s s 34-3 s s 24-2 s s 14-1 s 9-5 s 4-1 s simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s TI before RA TI after RA CIATM/C2336/N999/BR, version 1., 27 October Number of aircraft Number of aircraft

37 Timing of TCAS reports (8) Effect of ATC Timing of first RA reports possibly influenced by ATC intervention (TI or AA) close to first RA on board, and vice-versa > 6 s s 54-5 s s 44-4 s s 34-3 s s 24-2 s s 14-1 s 9-5 s 4-1 s simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s 4 2 TCAS report before AA TCAS report after AA > 6 s s 54-5 s s 44-4 s s 34-3 s s 24-2 s s 14-1 s 9-5 s 4-1 s simultaneous 1-4 s 5-9 s 1-14 s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s s 9-94 s s 1-14 s s s s > 12 s TCAS report before TI TCAS report after TI CIATM/C2336/N999/BR, version 1., 27 October Number of aircraft Number of aircraft

38 Timing of TCAS reports (9) Effect of ATC Timing of first RA reports possibly influenced by ATC intervention (TI or AA) close to first RA on board, but not only Median: 11 seconds (over 17 RA reports with RA after ATC) Median : 12 seconds (over 19 RA reports with RA before ATC) Median: 7 seconds (over 13 RA reports without ATC intervention) Number of aircraft simultaneous 1-4 s 5-9 s CIATM/C2336/N999/BR, version 1., 27 October s s 2-24 s s 3-34 s s 4-44 s s 5-54 s s 6-64 s s 7-74 s s 8-84 s TCAS report after first RA onboard RAafterATC_TCASRepFirst RAbeforeATC_TCASRepFirst RAwithoutATC_TCASRepFirst s 9-94 s s 1-14 s s s s > 12 s 38

39 Timing of TCAS reports (1) Effect of ATC 15 RA_TCASRepFirst Timing of ATC intervention compared to first RA onboard (in seconds) ATC intervention after RA ATC intervention before RA ATC intervention before RA RAwithoutATC_TCASRepFirst RAwithTI_TCASRepFirst RAwithAA_TCASRepFirst ATC intervention after RA report ATC intervention after RA, yet before RA report Timing of TCAS report compared to first RA onboard (in seconds) CIATM/C2336/N999/BR, version 1., 27 October 29 39

40 Timing of TCAS reports (11) Effect of ATC Traffic Information before RA followed by prompt RA reports Traffic Information after RA possibly delaying RA reports Traffic Information prompted by RA reports Traffic Information after RA Traffic Information before RA CIATM/C2336/N999/BR, version 1., 27 October 29 RAwithTI_TCASRepFirst Delayed TCAS report (more than 1s after first RA onboard)

41 Timing of TCAS reports (12) Effect of ATC Example of Traffic Information after RA possibly delaying RA report due to frequency occupancy by ATC Time Who Message (VHF or TCAS) AC2 AC1 Vertical profiles 17:22:34 17:24:3 17:25:17 17:25:32 17:25:42 17:25:37 17:25:48 17:25:57 17:26:14 17:26:28 17:26:3 ATCO ATCO ATCO ATCO AC2 TCAS1 TCAS1 ATCO AC1 TCAS1 AC1 AC1, descend FL 3-6- AC1, minimum rate of descent, 15 fpm AC1, I confirm descend FL 3-6- and increase your rate of descent AC2, traffic 1 O clock, 15NM, left to right, descending 1, feet above your level Traffic in sight, AC2 Traffic, Traffic Adjust Vertical Speed, Adjust AC1, traffic, 2 O clock, 5NM, right to left, 1, feet below your assigned level. I confirm, maintain FL 3-6- when reaching TCAS RA, AC1 Clear of conflict AC1 clear of conflict CIATM/C2336/N999/BR, version 1., 27 October 29 41

42 Timing of TCAS reports (13) Effect of ATC Avoiding Actions after RA possibly delaying RA reports A few Avoiding Actions after prompt RA reports Avoiding Action after RA Avoiding Action before RA CIATM/C2336/N999/BR, version 1., 27 October 29 RAwithAA_TCASRepFirst Delayed TCAS report (more than 1s after first RA onboard)

43 Timing of TCAS reports (14) Effect of ATC Avoiding Actions issued by ATC after RA reports Pilots following the reported RAs Avoiding instructions given in the horizontal plane Pilots not always following ATC instruction First RA onboard own aircraft Pilot s response to RA Type of pilot report Avoiding Action by ATC Pilot s response to AA Descend Descent RA Turn left heading n - Descend Descent Descent Turn left n degrees - RA Turn right n degrees Turn right n degrees CIATM/C2336/N999/BR, version 1., 27 October 29 43

44 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 44

45 Correctness of TCAS reports (1) - General Regardless of applicable phraseology (before and after November 27), TCAS reports (when present) not always reflect RA onboard Type of pilot report No report TCAS alert (with no other detail) TA RA (with no other detail) Descent Adjust vertical speed Maintaining current level Clear of conflict Total Legend: AVSA: Adjust Vertical Speed, Adjust LC: Limit RA LD: Limit Descent RA Total Unknown RA onboard own aircraft CIATM/C2336/N999/BR, version 1., 27 October Descend AVSA (LD) 3 (LC) 1 (LD) Monitor Maintain

46 Correctness of TCAS reports (2) Positive RAs RAs that require deviation from ATC instruction or clearance are not always reported (before and after November 27) or Descend RA Before Nov 27 After Nov 27 No report TCAS TA RA Descent Adjust Vertical Speed Maintaining level CoC TCAS reports for positive RAs still include or Descend reports instead of TCAS RA reports after November 27 CIATM/C2336/N999/BR, version 1., 27 October 29 46

47 Correctness of TCAS reports (3) Positive RAs Not reported or Descend RAs 1) sometimes not followed by pilots 2) sometimes compatible with ATC avoiding instructions 3) often combined with pilot RA report from threat aircraft Avoiding instruction from ATC First RA onboard Pilot s response to RA Pilot s response to ATC Coordinated RA onboard threat aircraft Pilot report from threat aircraft - Descend Descent Descend RA FL FL Descend Descent Descend FL Descend Descent Descend FL - - Monitor - Expedite descent Descend Descent Reduced descent; then descent RA Descend TCAS Maintain FL - Maintain FL Descend Descent Expedite climb FL FL Descend RA CIATM/C2336/N999/BR, version 1., 27 October 29 47

48 Correctness of TCAS reports (4) Other RAs TCAS reports not limited to RAs that require deviation from ATC instruction or clearance (particularly after November 27) No report TCAS TA AVSA, Monitor or Maintain RA Before Nov 27 After Nov 27 RA Descent Adjust Vertical Speed Maintaining level CoC For RAs other than and Descend, TCAS reports often reflect pilot s response to RAs (regardless of applicable phraseology) CIATM/C2336/N999/BR, version 1., 27 October 29 48

49 Correctness of TCAS reports (5) Other RAs More about AVSA, Monitor or Maintain RAs reported by pilots otherwise than by TCAS RA First RA onboard AVSA (LC) AVSA (LD) AVSA (LD) AVSA (LC) AVSA (LD) AVSA (LD) AVSA (LD) AVSA (LD) Pilot s response to RA - Rate reduced Level-off Rate reduced Rate reduced Level-off Type of pilot report CoC (1) TCAS CoC Adjust Vertical Speed Maintaining AVSA (LC) Rate reduced Descent (2) Note: (1) TCAS resolution advisory requiring a slight climb (2) TCAS to descend (3) TCAS descent AVSA (LC) AVSA (LC) AVSA (LD) Monitor Level-off Descent - Maintaining Descent Maintaining Legend: AVSA: Adjust Vertical Speed, Adjust CoC: Clear Of Conflict LC: Limit RA LD: Limit Descent RA AVSA (LC) AVSA (LD) Monitor Maintain AVSA (LD) Level-off - Rate reduced Descent (3) Maintaining TA TCAS CIATM/C2336/N999/BR, version 1., 27 October 29 49

50 Correctness of TCAS reports (6) Other RAs Example of AVSA to not descend reported as TCAS by the pilot while pulling the stick to follow the RA during a 1, feet level-off situation (March 28) Time 21:44:7 21:47:45 21:47:47 21:48:24 21:48:49 21:48:52 21:48:57 21:48:58 Who AC2 ATC1 ATC2 TCAS1 TCAS1 AC1 TCAS1 AC1 Message (VHF or TCAS) ATC2 good evening, AC2, SID2 departure, climbing FL 1-2- AC1, cleared to FL 1-3- AC2, direct to WPT2 and maintain FL 1-2- reaching Traffic, traffic Adjust Vertical speed, Adjust TCAS, AC1 Clear Of Conflict Clear of traffic, AC1 CIATM/C2336/N999/BR, version 1., 27 October 29 5

51 Content Executive summary Background Context of the study TCAS RA reporting rate Timing of TCAS RA reports Correctness of TCAS reports Main outcomes CIATM/C2336/N999/BR, version 1., 27 October 29 51

52 In summary (1/4) TCAS RA reporting rate About half (48%) of / Descend RAs are reported Reporting rate is greater for positive RAs (48%) than for other RAs (2%) that do not require deviation from ATC instruction or clearance Unlike for other RAs, reporting rate of and Descend RAs increases with RA altitude and RA duration (both effects sometimes combined) Primary factor influencing the non-reporting rate is different for positive RAs (e.g. pilots has probably visual, spurious RA) and other RAs (e.g. procedure associated with frequent RAs, RA does not require deviation), although some common influencing factors exist (e.g. RA is too short) CIATM/C2336/N999/BR, version 1., 27 October 29 52

53 In summary (2/4) TCAS RA reporting rate Regardless of type of RAs, reporting rate is four times greater in double RA occurrences (81%) than in single RA occurrences (21%) likely because first RA reports prompt second RA reports For double RA occurrences with at least one or «Descend» RA, ATC is informed in about three quarters (76%) of the cases, although both pilots reported in only one third (3%) of the cases CIATM/C2336/N999/BR, version 1., 27 October 29 53

54 In summary (3/4) - Timing of TCAS RA reports Second RA reports (when present during double RA occurrences) quite delayed compared to first RA reports likely due to frequency occupancy by threat aircraft First RA reports shorter for positive RAs ( or «Descend») than for «Adjust Vertical Speed, Adjust (AVSA)» RAs First RA reports slightly quicker in case of Traffic Information by ATC before RA possibly due to increased pilot s situational awareness First RA reports slightly delayed in case of ATC intervention (Traffic Information or Avoiding Action) after RA likely due to frequency occupancy by ATC CIATM/C2336/N999/BR, version 1., 27 October 29 54

55 In summary (4/4) - Correctness of TCAS reports RAs that require deviation from ATC instruction or clearance are not always reported by pilots (before and after November 27) and Descend RAs without report are sometimes not followed by pilots TCAS reports for positive RAs still include or Descend reports instead of TCAS RA reports after November 27 TCAS reports are not limited to RAs that require deviation from ATC instruction or clearance (even after November 27) For RAs other than and Descend, TCAS reports often reflect pilot s response to RAs (regardless of applicable phraseology) CIATM/C2336/N999/BR, version 1., 27 October 29 55