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. 1)

ИЖЗ312

БГМ9493

Examples of LHDs (Example No. 2)

БАВ10

ГЛП39

Examples of LHDs (Example No. 3)

ЦАП204

ОРБ9438

AAD Protocol

Thank you!