ADS-C Performance

For ADS-C the downlink latency is monitored using all received ADS-C reports from which we can extract an aircraft timestamp.

As with CPDLC individual airline fleets are monitored on a monthly basis, to detect any performance variation and then the consolidated latency graphs are compared to detect variations between fleets.

We have found that some data filtering is required to obtain an accurate representation of actual performance:

• Duplicated ADS-C reports are relatively common from all aircraft types. These are the same reports sent two or three times from the aircraft and if left in skew the ADS latency data.
  
  
• We check the extracted data over known periods of system outages that have been notified by the CSP or where our ground system has been down. Any delayed reports during these periods are filtered from the data.
  
  
• If a known problem exists with an aircraft type, or a particular tail in a fleet, that is causing degraded performance data e.g. VHF transition on the B777, we will often filter these delayed reports to verify that there is nothing else impacting performance.”

A consolidated summary for 2008 ADS latency via SATCOM is shown below and some observations on the performance of the different types are noted.

Note 1: The performance seen here on airline III B777 is typical of the degraded performance caused by the known problem with VHF transition areas and the B777. This problem has been identified and fixed and will be available to airlines in the third quarter 2009. The typical performance seen from the B777 when delayed reports caused by VHF transition areas are filtered is illustrated by airline DDD B772 filtered.

Note 2:  This is the typical degraded performance seen at an ANSP that is caused by the degraded performance of a “rogue” aircraft in an airline fleet. Observation of the delayed reports on a monthly basis is usually enough to identify the “rogue” tail and enable corrective action to be initiated.

Note 3:  a. This is typical performance of the A343 aircraft using high speed  ACARS channels.
b. This is typical performance of the A343 aircraft using low speed ACARS channels.

Note 4: Typical performance of B744 fleets. Airline CCC uses the high speed ACARS channel, and airline BBB changed from low speed to high speed channels in sepust 2008.

Note 5: An example of a lower performing B744 fleet. Airline AAA converted to high speed channel use in July 2008 and we are still investigating why the fleet is only achieving around 90% of messages delivered by 180 seconds.

These accumulated analysis graphs provide a clear visual indication of the relative     performance of the different airlines aircraft types. They provide a very visible representation of where improvement is needed.

Click on any of the thumbnail images below to view larger

Last Modified : August 13, 2010

1. Comparative Fleet Analysis

SATCOM Chart 1	SATCOM Chart 1a
SATCOM Chart 2	SATCOM Chart 2a

2. B747 SATCOM Performance

Airline XXX	Airline GGG
Airline NNN

3. B777 SATCOM Performance

Airline DDD B777 DDD illustrates typical performance degradation associated with the known VHF transition issue affecting the B777. A fix for this issue is expected with the AIMS1- BP14 software upgrade.	Airline QQQ B777 QQQ does not utilise the SITA VGS in NZZO FIR and the performance data is unaffected by VHF transition issues.
Airline LLL	Airline PPP
Airline VVV	Airline FFF
Airline EEE	Airline RRR

4. A340 SATCOM Performance

Airline AAA	Airline ZZZ
Airline BBB

5. A380 SATCOM and SATCOM+HF Performance

Airline SSS SATCOM	Airline SSS SATCOM + HF
Airline UUU SATCOM	Airline UUU SATCOM + HF

6. All Aircraft – All RGS

RSP180	RSP180a
RSP400	RSP400a

7. All Aircraft – SATCOM

RSP180	RSP180 a
RSP400

8. All Aircraft – SATCOM + HF

RSP180	RSP180 a
RSP400

9. All Aircraft – HF

RSP180	RSP180 a
RSP400	RSP400 a

10. All Aircraft – VHF

RSP180	RSP180 a
RSP400