Precision-stabilised to remove the effects of a ship’s pitch and roll, giving a stable and constant beam of light along a specified glide slope, the AGI Glide Slope Indicator is a precision-stabilised light projector which is used to guide a helicopter pilot along a safe angle of approach for a landing aboard ship.

The equipment has been introduced to replace the ‘Glide Path Indicator (GPI) Mk II’ previously in service with the British MOD and many other navies worldwide. A prime objective of the replacement programme is to extend and improve the Royal Navy’s helicopter operational capability under environmental extremes. To achieve this, the SGSI had to offer significant improvements in performance and, in doing so, provide real operational benefits. The second primary objective was to lessen the workload placed upon the pilot in flying larger, more sophisticated aircraft and, in this respect, the replacement device had to contribute a significant reduction in his workload.

The improvements in performance obtained in deploying the replacement SGSI, when compared to its predecessor are:

Better Optical Performance

Higher light intensity
High colour definition
Absence of ‘ghosting’ to ensure unambiguous projection of light beam signals
Fully variable light output for night-time operation and NVG compatibility
A beam pattern which provides instantaneous positional information during approach

Better Mechanical Performance

Precise stabilisation under pitch and roll conditions
Extended azimuth cover under remote control

Better System Performance

Higher reliability
Extended roll/pitch capability
Fail-safe design
Better self-diagnostics
Safer design

The benefits which have accrued as a result of these improvements are:

All weather day/night operation
Reduced pilot workload
Improved safety
Low maintenance
Reduced through-life costs

The system’s modular construction allows it to be factory-configured to provide a light beam geometry, as observed by the pilot, to the preferred customer format. Therefore, deployment of the replacement glide slope indicator will not require pilot re-training. Where NVG-compatibility is required, the SGSI would be configured with beam characteristics that are Night Vision Goggle Gen III Class A or B compatible and comply with MIL-Spec MIL-L-8562A.

The SGSI has been designed, not only to provide a high performance, but also to reduce its cost of ownership. Installation is straight forward, requiring no special tools. Its high reliability and low mean-time-to-repair results in a high availability and low support costs. Furthermore, there are no environmental hazards, no filters/blowers to change while preventative maintenance is reduced to the occasional checking and cleaning. Lastly, the equipment was purposefully designed to be software-free. Therefore there are no hidden bugs or potential hazards that could jeopardise safety.

The primary benefits in adopting the SGSI into service would be:

a low-risk, low-cost solution (being non-developmental, proven design, in-service)
improved operational capability (via high performance and NVG-compatibility)
reduced operating costs (having high reliability, low maintenance)

The SGSI is a proven device having been developed with UK MoD sponsorship and tested exhaustively at sea by them. Adoption of this equipment could, therefore, result in massive savings in comparison to a developmental or refurbishment solution. The SGSI has been designed to operate autonomously in conjunction with the HELIVAS System, that incorporates a Stabilised Horizon Reference Bar and Deck Edge Lighting of LED or advanced Electro-luminescent Panel design.

Finally, the SGSI’s background would provide the operational and design assurance required, thus minimising the risks normally associated with introducing new equipment into service.

The AGI SGSI pointing aft, in service aboard HMS Iron Duke, a Type 23 Frigate.



The AGI SGSI is available and in service with different beam colour formats to match the operational procedures utilised by different countries, and is therefore particularly suited to the refit of existing outdated equipment.