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VHF Performance Evaluation Report

VHF Performance Evaluation Report. DCIT 22 14 March 2013 Mike Matyas. Contents. Background RCP, RCTP, and ACTP Data Conclusions Next steps Detailed data and results. Background – Hierarchy. FAA Data Comm program uses FANS FANS uses AFN, CPDLC, and ADS-C applications

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VHF Performance Evaluation Report

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  1. VHF Performance Evaluation Report DCIT 22 14 March 2013 Mike Matyas

  2. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data and results

  3. Background – Hierarchy • FAA Data Comm program uses FANS • FANS uses AFN, CPDLC, and ADS-C applications • AFN, CPDLC, and ADS-C applications use ACARS network • ACARS network uses five subnetworks • VDL Mode 0/A (uses “plain old” ACARS [POA] protocol) • VDL Mode 2 (uses ACARS over AVLC [AOA] protocol) • Inmarsat Classic Aero SATCOM • Iridium SATCOM • HF Data Link (HFDL)

  4. Background – Media Management • FANS applications (in FMC) are independent from router function (in CMU) • FANS applications cannot select which subnetwork to use or even determine which subnetwork is in use • Like smartphone e-mail app that cannot select Wi-Fi, 4G, or 3G • Router function switches between subnetworks to maximize communications availability • Operator priority preferences are usually VHF (VDL Mode 2 AOA then VDL Mode 0/A POA), then SATCOM, and then HFDL • This behavior often called “FANS media management” • FAA has decided to accept it as-is, which will avoid requiring significant and widespread avionics changes

  5. Background – Purpose and Means • Purpose: Characterize VHF datalink performance for FANS in domestic NAS • Is VDL Mode 0/A POA performance acceptable? • About 40% of US 737NG, 757, and 767 fleet does not have VDL Mode 2 AOA capability • Means: Assess round-trip times of ADS-C demand contract request-report pairs • One ADS-C demand contract request results in one ADS-C demand contract report • Representative of FANS technical performance • No flight crew AFN log on or other action required

  6. Background – Block Diagram • Boeing acted as ATSU (ANSP) to send requests to and receive reports from aircraft in normal operation

  7. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data and results

  8. RCP, RCTP, and ACTP (1/6) • Per ICAO Doc 9869, Manual on Required Communications Performance (RCP), RCP “characterizes the performance required of communication capabilities that support ATM functions without reference to any specific technology” • In other words, RCP provides a framework for performance-based, technology-agnostic voice and data communications • RCP is expressed in terms of end-to-end transaction time and measured in terms of time, continuity, availability, and integrity

  9. RCP, RCTP, and ACTP (2/6) • E.g., RCP240 as specified by ICAO Global Operational Data Link Document (GOLD): • RCP expiration time (ET 99.9%) provides real-time operational basis: “The maximum time for the completion of the… transaction after which the initiator is required to revert to an alternative procedure.”

  10. RCP, RCTP, and ACTP (3/6) • RCP nominal time (TT 95%) provides non–real-time compliance basis: “The maximum nominal time within which 95% of… transactions is required to be completed.” • From SC-214 Plenary 16 minutes: “The OPA will… provide performance values for 99.9%, but these values will be guidance material rather than requirements. (The 95% performance specifications remain requirements… for certification).” • 95% performance is accordingly most relevant absolute measure for FAA’s decision to whether to accept VDL Mode 0/A POA

  11. RCP, RCTP, and ACTP (4/6) • Required Communications Technical Performance (RCTP) is the “… portion of the (intervention) transaction time [i.e., subset of RCP] that does not include the human times for message composition, operational response, and recognition of the operational response.” • RCTP is round-trip (uplink plus downlink) time • RCTP is ATSU (ANSP), CSP (DSP), and aircraft systems transfer and processing time • Actual Communications Technical Performance (ACTP) is simply observed RCTP

  12. RCP, RCTP, and ACTP (5/6) Controller – not included ATSU, CSP, aircraft systems – included Flight crew – not included ATSU, CSP, aircraft systems – included Controller – not included

  13. RCP, RCTP, and ACTP (6/6)

  14. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data and results

  15. Data • 30,178 POA and 10,395 AOA data points collected • 160 days: from July 20 to December 26, 2012 • 5 operators: ANZ, DAL, FDX, UAL, UPS • 12 aircraft types: B744, B753, B762, B763, B764, B772, B77L, B77W, B788, MD11, A332, A333 • 319 aircraft registrations (i.e., individual ships/hulls) • 2 DSPs: both ARINC and SITA (one 69%, one 31%) • 52 data points (0.13%) excluded from evaluation because invalid (e.g., -3,593s PORT)

  16. Data: 0-99% POA ACTP

  17. Data: 0-99% AOA ACTP

  18. Data: 0-99% POA & AOA ACTP • Average AOA ACTP is only 3.3s faster than average POA ACTP • Remember, ACTP is round-trip • POA begins to perform better than AOA at the 97.4% point

  19. Data: 95-99.9% POA & AOA ACTP • POA ACTP is better than AOA ACTP in the 97.4%-99.98% range • Including at the 99% and 99.9% measurement points

  20. Data: 95% POA & AOA RCTP & ACTP • Draft B2 RCP120 95% RCTP requirement of 18s is taken from Table G-2 of RTCA SC-214 / EUROCAE WG-78 PU-10_SPR-J_AnnexFGHI_OPA_3_Dec_2012.doc

  21. Data: 99.9% POA & AOA RCTP & ACTP • Draft B2 RCP120 99.9% RCTP requirement of 32s is taken from Table G-2 of RTCA SC-214 / EUROCAE WG-78 PU-10_SPR-J_AnnexFGHI_OPA_3_Dec_2012.doc

  22. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data and results

  23. Conclusions (1/2) • In (more meaningful?) relative terms… • Average AOA ACTP is only 3.3s faster than average POA ACTP (remember, ACTP is round-trip) • POA ACTP is better than AOA ACTP in the 97.4%-99.98% range (including at the 99% and 99.9% points) • In (less meaningful?) absolute terms… • POA and AOA 95% ACTP (17.4s and 11.0s) meet draft B2 RCP120 95% RCTP (18s) • Neither POA nor AOA 99.9% ACTP (90.3s and 95.4s) meet draft B2 RCP120 99.9% RCTP (32s)

  24. Conclusions (2/2) • POA performance is sufficient for Data Comm FANS use • Especially in comparison to AOA performance • Small advantage of AOA over POA would not justify large cost and schedule impacts of required AOA upgrades • Cost impacts: $xxK to $xxxK per aircraft • Schedule impacts: months to years

  25. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data and results

  26. Next Steps • Thanks to ANZ, DAL, FDX, UAL, and UPS for participating • Compose report in document form with additional detail by end of March • Consider requesting permission from FAA and operators to further analyze and distribute deidentified results (and data?) • E.g., AEEC Data Link Systems Subcommittee would be very interested in how and why POA outperformed AOA • “Deidentified” means no reference to specific aircraft operator, aircraft type, or CSP (DSP)

  27. Contents • Background • RCP, RCTP, and ACTP • Data • Conclusions • Next steps • Detailed data

  28. CONUS • 18,113 (60%) POA data points inside CONUS, 12,065 (40%) outside • Most data points acquired outside CONUS from flights to/from Europe over eastern Canada • 9,719 (93%) AOA data points inside CONUS, 676 (7%) outside • No further analysis performed

  29. CONUS Definition

  30. CONUS 0-99% POA ACTP

  31. Northeast Corridor (NEC) • 8,873 (29%) POA data points inside NEC, 21,305 (71%) outside • 666 (6%) AOA data points inside NEC, 9,729 (94%) outside • No further analysis performed

  32. NEC Definition

  33. NEC 0-99% POA ACTP

  34. Average POA ACTP by Time • Data mixed between domestic / international and passenger / freight flights and across local time zones more data, more stability less data, less stability

  35. Average AOA ACTP by Time • Data mixed between flights and across time zones more data, more stability less data, less stability less data, less stability

  36. Average POA ACTP by Date 5% of data (unstable performance) start start stop

  37. Average AOA ACTP by Date 3% of data (unstable performance) start

  38. Federated vs. Integrated Avionics • Federated avionics: FMC, CMU, etc. hosted in separate boxes; typical for older designs (e.g., 767) • Integrated avionics: FMF, CMF, etc. hosted on cards in cabinet; typical for newer designs (e.g., 777) • 10,467 (35%) POA data points from federated avionics,19,711 (65%) from integrated avionics • 6,294 (61%) AOA data points from federated avionics, 4,101 (39%) from integrated avionics

  39. Avionics 0-99% POA ACTP • Federated POA average ACTP: 8.7s • Integrated POA average ACTP: 7.8s

  40. Avionics 0-99% AOA ACTP

  41. ACTP and ACP • ACTP = ((②-①)/2)+(④-③) • ACP = ④-① • For this evaluation, ACTP and ACP should (theoretically) be very similar because PORT should (theoretically) be zero

  42. 0-99% POA ACTP and ACP

  43. 0-99% AOA ACTP and ACP

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