Introduction
The following specification summarises the key updates in the Helideck Certification Agency (HCA) document “Standard Measuring Equipment for Helideck Monitoring Systems (HMS) and Weather Data – Revision 9c (2023)”.
This revision aligns with CAP 437 Edition 9 issued by the UK Civil Aviation Authority (CAA), providing detailed technical requirements for moving helidecks — i.e., floating installations and offshore vessels subject to deck motion and meteorological variation.
Scope and Applicability
This specification applies to moving helidecks, including vessels, FPSOs, semi-subs and floating platforms where deck motion must be measured and monitored for safe helicopter operations.
It is intended to implement the CAP 437 Edition 9 framework for HMS performance and weather-data systems and is not designed for fixed helidecks (which fall under CAP 437 without the HMS motion requirement).
Compliance with this document is typically required for UK-sector installations and may be accepted by other jurisdictions or classification societies that reference CAP 437 and HCA HMS standards.
Key Differences: HCA Rev 9b vs Rev 9c
Here is a summary of the principal changes from Rev 9b to Rev 9c relevant to HMS and weather data systems:
| Topic | Rev. 9b | Rev. 9c (February 2023) |
|---|---|---|
| Sampling Rates | Motion: 2HzWind: 4Hz | No change |
| Update Rate | Minimum 0.1 Hz | No change |
| SHR Landing Status Logic | SHR logic applied but rounding method unspecified | Requires use of rounded-up values to determine landing status |
| Declination Handling | May be applied manually | Declination must be automatically calculated and applied |
| Marked Discontinuity (MD) | Not explicitly required on HMS display | MD must be visibly presented in the compass rose display |
| Anemometer Switching | Dual anemometers recommended in some configurations | Automatic switching required when a secondary is available |
| Helicopter Type Defaults | Defaults to Category A often implicit | Category A helicopter must be explicitly applied by default at start-up and in pre-landing mode |
| Day/Night Status | Operator input common | Automatic detection required; system must default to night if undetermined |
| Trend Presentation | Trends required for key parameters | Now mandates 20-minute max values and limit lines for Pitch, Roll, Inclination, and SHR |
| Touchdown Heading Alerts | Alerts on invalid data entry recommended | Mandatory alerts if heading input will cause red/amber RWD status |
| Vessel/Helicopter Δ-Heading | Highlighting optional | Numerical and plot highlighting required for large heading or wind direction changes |
| Repeater Light Control | Testing available | Test function must be inhibited during wind or motion exceedance |
| Sensor Faults | General fault indicators required | Specific requirements for excluding faulty data from buffers and flagging missing data (e.g. greying out parameters) |
| Vessel Categories | General categorisation | Category 1 subdivided into “Cat 1 Semi-Sub” and “Cat 1 Other” |
| Helicopter Categories | Based on older type classification | Updated nomenclature reflecting industry changes |
| Screenshot Sharing | Display transmission methods vary | Streamlined screen capture must be available for sending HMS data to flight crew |
| Training Material Approval | Good practice | Formal review and acceptance of training material now required by national aviation authority (e.g. CAA) |
Compliance & Implementation Notes
To achieve full compliance with CAP 437 Edition 9 via HCA Rev 9c, operators must ensure the following:
- Proper installation and calibration of HMS sensors (motion, wind, temperature, pressure, etc.).
- Verification of data-handling logic and alerting mechanisms (based on the Rev 9c table).
- Operator training and documented procedures that reflect the HMS configuration, alert logic and maintenance regime.
- A Site Acceptance Test (SAT) and audit, typically by the HCA or the relevant national aviation authority for the UK sector, moving helidecks.
- Change-control and software-version management to ensure any HMS modifications maintain compliance with Rev 9c logic.
Why Choose WISE Group
At WISE Group, we specialise in delivering helideck-monitoring and meteorological systems designed around CAP 437 Edition 9 and HCA Rev 9c requirements.
Our experience includes:
- System design, hardware selection and integration for moving helidecks worldwide.
- Firmware and software configuration in line with HCA logic and alerting rules.
- Full calibration, verification and commissioning services.
- Upgrade paths from earlier revisions (e.g., HCA Rev 8c → 9b → 9c).
- Training, documentation and class/HCA audit support to facilitate certification.
Contact us to discuss your moving-helideck monitoring requirements and how we can ensure compliance and operational readiness.