Message Name:

ALTIMETRY SYSTEM ERROR REPORT (ASE-R) ISSUED BY REGIONAL MONITORING AGENCY (RMA)

Altimetry System Error (ASE) is defined as the difference between the static pressure sensed and the actual altitude flown. ASE is invisible to the pilot and Air Traffic Control (ATC) and can lead to hazardous loss of separation. ASE is an aerodynamic condition and cannot be simulated by ground testing.

• Irregularities in the RVSM Skin and RVSM Critical Areas
• Incorrect Lower Probe Angles
• Pitot/Static Probe 1 (MT149)
• Pitot/Static Probe 2 (MT152)
• Pitot/Static Probe 3 (MT150)
• Standby/Pitot Static Probe (MT151)
• Angle of Attack Sensor (AOA)

Advisory Wire/Service Bulletin:

• AW 700-34-0346 - Air Data Computer (ADC) and Pitot-Static Probes - Altitude Split and Troubleshooting Guidance

Forum Articles/Infoservice/Newsletter: None

NOTES:

• The Altimetry System Error Report process is described in the attached FAA document
  InFO 17002 (Information for Operators).
• Additional information is available on the FAA Separation Standards Analysis Branch website.
  ASE-R_FAA Description document.
• Additional information is available on the FAA Separation Standards Analysis Branch website.
  https://www.faa.gov/air_traffic/separation_standards/ .
• The Air Data System of Global Express/XRS/5000 aircraft has four pitot-static probes installed along with two ATC Transponder systems for transmitting the Automatic Dependent Surveillance - Broadcast Out (ADS-B Out) data. The upper probe pair (ADC #1 & Standby) is primarily dedicated to Air Data System #1 and ATC Transponder #1, while the lower probe pair (ADC #2 & #3) is primarily dedicated to Air Data System #2 and ATC Transponder #2.
• The active ATC Transponder, as selected by the pilots, determines which probe pair system is actually being height monitored by RMA (ref AFM Supplement 07-08 RVSM Operations). The upper and lower probe pairs have their own unique ASE characteristics, and it is possible that one probe pair can be out of monitoring limits while the other probe pair is well within the limits.
• Therefore, it is essential that both upper and lower probe pairs are evaluated for their respective ASE. For Global Express/XRS/5000 aircraft, there is an eight-table, airspeed and altitude RVSM flight evaluation sheet for recording Air Data System data under specific conditions.
• The eight tables cover two different altitudes in RVSM airspace (FL310 & FL410) and two Mach speed points should read: (0.80M & 0.86M or 0.85M & 0.88M) for each probe and Transponder pair. Each of the eight tables are performed for a minimum of five minutes in a steady heading, level flight attitude.
• RMA monitoring system can easily plot this profile with reliable results once all of the data is collected and processed (ADS-B plus weather modelling). This provides a very accurate evaluation of the ASE for both the upper and lower probe pairs.

Steps to address an ASE-R:

NOTE: 

• A chargeable SERVICE REQUEST for PRODUCT SUPPORT ACTION (SRPSA) is required for all Bombardier Engineering analysis and aircraft structural reworks.
• Refer to the following documents for the Flight Evaluation.
  RVSM Flight Evaluation_9002-9158
  RVSM Flght Evaluation_9159

NOTE:
The following steps are required in order to establish a baseline condition and performance evaluation of the complete Air Data System. The analysis of this data may result in a specialized, structural rework of the aircraft skin in the vicinity of the pitot-static probes along with an optimized structural rework of lower probe angles. This requires a dedicated and planned visit to a capable Bombardier Service Center with an aircraft downtime of several weeks. 

1. Provide to Bombardier Engineering, a detailed maintenance record of work performed on the Air Data System (ADS), including probe and/or sensor replacements (e.g., TAT, AOA), any structural repairs/alterations in the RVSM area (SRPSAs, SNIEOs), nose access door repairs/replacements, radome repairs/replacements and aircraft paintwork. The time period should cover between the last known successful RVSM altitude monitoring to the present. A sudden shift in RVSM performance monitoring by the RMA may be attributable to a recent and/or specific maintenance action.
2. Provide to Bombardier Engineering, recent pilot reports for any ADS performance issues such as altitude splits, fluctuations, etc., and the speeds and altitudes where they occurred.
3. Perform the visual inspection of the RVSM critical area (zone 4). Make sure that the steps and gaps of the forward equipment compartment doors, forward hydraulic bay door, oxygen service door, RAT door and radome are within the tolerances (SRM 51-14-04). Make sure that the pitot-static probes sealant is smooth. Record and report results to Bombardier Engineering.
4. Perform a detailed inspection of the pitot-static probes (AMM TASK 34-11-01-220-801). Record and report results to Bombardier Engineering.
5. Perform the alignment check of the pitot-static probes (AMM TASK 34-11-01-820-801). Record and report results to Bombardier Engineering.
   NOTE:
   Record the angular value for all four probes using the Pitot Probe Alignment Table (ref SmartFix Plus (SFP) Observed Fault 341OBS001). If a probe is removed for cleaning or replaced, the installation of the probe has to be done at the same angle.
6. Perform a servicing of the visual drains in (AMM TASK 34-11-03-616-801).
7. Perform a contamination removal of the ADS pitot-static lines (AMM TASKS 34-11-01-100-801 through -809).
8. Perform individual leak tests of the ADS (AMM TASKS 34-11-00-790-801 through -804). Record and report the individual system leak rates to Bombardier Engineering.
   NOTE:
   When performing the leak check after the contamination removal procedure, each system should be tested one at a time, leaving the system open to ambient pressure, this to detect any inter system issue (i.e., incorrect installation).
9. Perform a baseline ADS calibration on all four pitot-static systems (AMM TASK 34-11-00-720-801). Record and report results to Bombardier Engineering.
10. Perform a baseline calibration of the Static Source Error Correction (SSEC) of the Air-Data Computer (ADC) System (AMM TASK 34-11-00-750-801). Record and report results to Bombardier Engineering.
11. For aircraft with a dedicated Mach Transducer installed (MT80), perform a functional test of the Mach Transducer (AMM TASK 27-32-13-720-801). Record and report results to Bombardier Engineering.
    NOTE: 
    Not applicable for aircraft with a baseline, factory installed Thales ISI (9159 & Subs).
12. At the next ADS-B flight monitoring opportunity (Mondays only for FAA/NAARMO airspace), perform the RVSM Flight Evaluation per the aircraft effectivity (below) and record the data for Bombardier Engineering. It is recommended to perform this flight as early in the day as possible as NAARMO has a UTC cut-off time of 23h59 to record a full flight. The flight evaluation takes approximately two flight hours to complete.
    RVSM Flight Evaluation_9002-9158 (doc)
    RVSM Flight Evaluation_9159 and Subs (doc)
13. For each evaluation table, press the pilot event marker (PEM) and record the start and stop times (AMM TASK 45-45-00-970-819) as indicated in the table. The PEM provides a time stamp on the FDR data and also triggers the SPC to record ADS parameters in non-volatile memory (NVM).
    NOTE:
    There are eight separate evaluation tables to record the required airspeeds and the altitudes. The set-up instructions are in the evaluation sheet. Bombardier Engineering can assist with a pre-flight briefing as required.
    NOTE: 
    Prior to the RVSM evaluation flight, Bombardier Engineering may request to perform a baseline RVSM area skin mapping along with a laser measurement of the upper and lower pitot-static probe angles. This work needs to be performed at a capable Bombardier Service Center and may involve a third-party provider capable of performing this specialized work.(SRPSA required)
14. After the evaluation flight, perform a download of the Flight Data Recorder (FDR) data and Stall Protection Computer (SPC) CHA & CHB NVM (AMM TASKS 31-31-00-970-801 and 45-45-00-970-822). Send the FDR and SPC data files along with the completed RVSM Flight Evaluation sheet to the Bombardier Customer Response Center (CRC). The CRC can assist with large file transfers.
    NOTE:
    QAR data may be downloaded (AMM TASK 31-33-00-970-801) in lieu of FDR data if the aircraft is equipped with a QAR (Post SB 700-31-026/700-1A11-31-008). Ensure that the QAR is not full and is capable of recording the flight data.
    NOTE:
    It normally takes 3-4 business days for the FAA Separation Standards Analysis Branch to process the flight data and provide the required data plots to Bombardier Engineering. Once the data is analyzed, Bombardier Engineering will provide further instructions on the work to be performed.(SRPSA required)
    NOTE:
    After the required work has been carried out on the aircraft, a subsequent flight evaluation is required in coordination with the FAA (Mondays only) in order return the aircraft to service (Steps 12, 13 and 14).
    NOTE: 
    Any structural rework in the RVSM area will require an additional RVSM skin mapping and a laser measurement of the pitot-static probe angles prior to the final evaluation flight. (SRPSA required)
15. Check if the flight data is satisfactory (FAA and Bombardier Engineering).

    1. If the flight data is satisfactory, do close out.
    2. If the flight data is unsatisfactory, Bombardier Engineering will advise on the next steps.
       NOTE:
       Contact your FSR or Customer Response Center (BA CRC) for guidance.

16. Do close out.