GNSS IFR InstallationsGNSS IFR Installations&&

ApprovalsApprovals

Ron Doggett

Aircraft Certification Unit1

ContentsContents

GNSS AC Development Installation Requirements and Issues Autopilots & Instrument Switching Other Requirements Flight Testing Future Requirements

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GNSS AC DevelopmentGNSS AC Development

Part 19 Sub Part D out of date. GNSS AC is an interim solution until Part 91 Rules

are amended by PBN implementation. Exemptions are required to Part 19 to recognise

GNSS(GPS) maturity and enable AC provisions. CAA 2129 will have operational capability added

as Part B. Goal: draft for public comment by the end of the

year.3

Installation RequirementsInstallation Requirements

Equipment must be approved for Level 1 (TSO). Installation must comply with FAA AC 20-138A

Airworthiness Approval Of Global Navigation Satellite System (GNSS) Equipment requirements.

TSO C129a equipment requires a pressure altitude input (from an approved source). Recommended for TSO C129 equipment.

Relevant airworthiness requirements must be met.

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Human Factors & System SafetyHuman Factors & System Safety

Perception …

Pilots are cool dudes who can hack anything…- including dealing with bad designs -

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Human Factors & System SafetyHuman Factors & System Safety

Reality …

Design engineers must design for the “inverse” of the perception!

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Installation Human FactorsInstallation Human Factors

System safety and human factors is not about how easy it is on a good day, but how hard it is to get it wrong on a bad day.

Remember -

The Domino Theory and Reason’s Swiss cheese are extensions to Murphy’s law –

If it can happen, it will and at the worst possible time.

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Installation PointsInstallation Points

System(s) must be integrated with flight instruments. Two crew aircraft require integration with both pilot’s

flight instruments (FAR 23.1321). CDUs must be clearly visible under all lighting

conditions, and be easily reached. Dual antenna installations require lateral separation. Lit panels need to be properly modified.

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Autopilots & Instrument SwitchingAutopilots & Instrument Switching

Interface to flight instruments and autopilots has a high human factors risk, particularly for switching and pilot workload. Clever switching is behind the panel, not in front.

Switching systems must be independently powered. Autopilots must maintain the aircraft within half

the CDI scale on straight segments. Adjusting CDI scaling from default values for

autopilot gain is not permitted.9

Poor Installation ExamplesPoor Installation Examples

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Pilot View Actual Display

Control panels also need to be modified.

Other RequirementsOther Requirements

Steering interfaces need output to input compatibility analysis, particularly for analogue systems.

Electrical Load Analysis is required for the aircraft. GNSS installations are becoming essential systems.

The complete installation must be considered in the assessment, including interfaces to other systems.

Flight Manual Supplements need to address autopilot coupling, if applicable.

ICAW are not optional!

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Flight TestingFlight Testing

A formal flight test plan is required. A risk assessment must be carried out with any

identified risks being mitigated or minimised. Installations that change the instrument arrangement or

couple to the autopilot require flight test and pilot workload assessment.

Production installations require flight validation only. Pilots need to be experienced and rated on the aircraft

and the equipment (Refer AC 19-1).

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Flight Test PlansFlight Test Plans

Preamble identifies: Changes made to the aircraft, prerequisites, personnel

requirements, flight profile, etc.

Tests procedures state: Test objective and pass / fail criteria. Identifies each process step for the test. Identifies any data to be recorded by the crew. Short or generic test specifications are not acceptable.

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Operational ApprovalsOperational Approvals

TSO C129 systems require FAA Order 8110.60 approval for oceanic / remote continental use.

For dual installations, the software configuration must be the same.

Operational approval for an aircraft is endorsed on the CAA 2129.

Foreign STC installations will be accepted per Part 21. Foreign and NZ modifications require CAA inspection

and flight test.

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Future RequirementsFuture Requirements

NZ will transition to area navigation with high reliance on GNSS. Requirements will be defined during PBN

implementation activity.

Air transport IFR GNSS will require dual systems fully integrated.

TSO C129 systems will require retention of legacy navigation systems; TSO C145/146 may not.

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Any questions?