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RVSM Workshop
Large Height Deviations (LHD)
LHD Reporting
RMA Eurasia
France, Paris
September 2014
HEIGHT-KEEPING PERFORMANCE
MONITORING TASKS
• The height-keeping performance monitoring is a
complicated task from the technological point of view,
and it requires significant efforts and special technical
measurement systems (EGMU, HMU, AHMS)
• Large Height Deviations (LHD) monitoring is a task,
which requires the development of special organizational
procedures. At the present day organizational and
technical methods are also used to complete this task
Large Height Deviation
Large Height Deviation (LHD) is a deviation of 90 m (300 ft)
or more in magnitude from the cleared flight level
(Doc 9937)
Item 2.2.24 Doc 9937: “Experience has shown that LHDs –
errors of 90 m (300 ft) or more in magnitude – have had
significant influence on the outcome of safety
assessments“
LHDs are taken into account during the overall collision
risk calculations.
Note. – During the calculations not only the number of LHDs is taken into account but
also the characteristic parameters of each LHD, i.e. magnitude of the deviation and its
duration.
Main Causes of LHDs
• automatic altitude-keeping system error
• turbulence and other meteorological conditions
• flight crew inconsistence with the stipulated procedures including
unforeseen conditions and aircraft emergency landing
• flight crew actions when implementing the Airborne Collision
Avoidance System (ACAS) recommendations
• flight crew inconsistence with the ATC clearance
• ATC unit error during issuance of the ATC clearance
• errors in coordination between adjacent ATC units while transferring
aircraft flight control responsibilities
LHD Data Collection and
Processing Procedure
• For the LHD data collection at regional level an LHD reports
collection program is established
• Main sources of the LHD reports are ATC units, which are providing
ATC service and which have to actively participate in the LHD
reports collection program
• ATC units have to report such occurrences every month
• RMA’s scrutiny Group conducts assessment and classification of
LHD reports
• RMA has to take into account these reports when assessing the
overall collision risk value and provide the information on receiving
of reports to the Regional Planning Group
LHD Report Contents
• Name of the unit providing the report
• Location of the deviation event indicating the
latitude/longitude or bearing and distance to the
reference point
• Date and time of the LHD event
• Specific airspace region, e.g. route
• Flight number and aircraft type
• Cleared flight level
• Actual flight level or altitude
LHD Report Contents (Continued)
• Actual altitude data source, e.g. pilot report or
transponder data
• Duration of flight at an incorrect flight level or at incorrect
altitude
• Opinion of the reporting person on what caused the LHD
• Presence of another aircraft posing a potential threat at
the moment of deviation
• Flight crew’s comments after notifying them on the
deviation
• Reporting ATC unit’s comments
LHD Reporting to ATS Units
During its latest meeting EANPG voiced a concern on the
common trend in decreasing of the ATS units involvement
in LHD reporting within the European region of ICAO. Thus
in the region of RMA Eurasia the number of LHD reports in
2013 decreased five times compared to 2011. A similar
trend can be seen in the region of EUR RMA as well.
Additional Way of Receiving the LHD Data:
Automated Surveillance Data Analysis
• Radius – 600 km
• ∆ H – 8,600-12,100 (m)
Atypical (Aberrant) Deviation
• Large Height Deviation (LHD) – A
deviation of 90 m (300 ft) or more in
magnitude from the cleared flight level
(Doc 9937)
• Atypical (aberrant) deviation – A deviation
of 90 m (300 ft) or more in magnitude from
the cleared flight level, which has been
detected by the objective control means,
when there is no information available at
ATS that such flight has been cleared
Scrutiny Analysis
Includes:
1. Automatic computer
analysis of the aircraft
flow
2. Experts’ visual analysis
3. Cooperation with an
ATS unit for comments
Examples of LHDs (Example No. 3)
ЦАП204
ОРБ9438
AAD Protocol
Thank you!