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Helideck Foam Systems
Helideck Foam Systems covers the fixed equipment that fights a fuel fire on the landing area: deck-integrated fire-fighting systems (DIFFS) with nozzles in the deck, fixed foam monitors at the deck edge, foam concentrate tanks, proportioners and hose reels. A used system's value depends on the D-value and foam performance level it was sized for, and on its annual test history.
How a helideck foam system works
Fire water from the main fire pumps reaches a proportioner, which meters foam concentrate into the stream at the design ratio. The foam solution then leaves through monitors or deck nozzles and spreads a blanket over burning fuel. The system aims to reach full rate within seconds of release, so control valves and release panels sit at protected points near the deck access routes.
Configurations
- Fixed monitor system (FMS). Two or more monitors around the deck edge throw a jet of foam across the landing area.
- Deck-integrated fire-fighting system (DIFFS). Pop-up or flush nozzles set in the deck spray foam over the whole surface. CAP 437 now names DIFFS as the preferred option.
- Water-only DIFFS on a passive fire-retarding surface. CAP 437 accepts seawater alone in some cases, because the perforated deck drains burning fuel away.
- Compressed air foam (CAF). Some packages inject air into the solution to make a drier, longer-lasting foam.
Key specifications
| Parameter | Why it matters | Typical classes or units |
|---|---|---|
| Foam performance level | Sets the application rate | ICAO level B or C |
| Application rate | Must cover the D-value circle | Litres per square metre per minute |
| Concentrate | Sets proportioning and tank size | 1, 3 or 6 percent |
| Discharge time | Sets the concentrate stock | Minutes |
| Water demand | Must match the fire pumps | Cubic metres per hour and bar |
| Nozzle or monitor count | Must suit the deck layout | Number and positions |
Standards and certification
CAP 437 and ICAO Annex 14 Volume II set the rates. With level B foam the minimum is 5.5 litres per square metre per minute, and with level C foam 3.75, over a circle of diameter D. A solid plate deck needs at least five minutes of discharge, and a passive fire-retarding surface with a water-only DIFFS at least three. The foam concentrate must be tested and approved to its stated ICAO performance level. On a mobile unit, class and flag state approval also apply.
Failure modes and inspection
- Proportioners drift or stick, giving weak or rich foam. Test the finished foam's concentration and expansion.
- Pop-up nozzles seize from salt and paint. Check springs, seals and that each nozzle rises and drains.
- Foam concentrate degrades with age and heat. Sample it and send it for laboratory testing.
- Mixing concentrates of different types or brands in one tank causes sludge. Check the tank history.
- Pipework corrodes where seawater lies stagnant. Check low points and drain valves.
- Release valves and remote panels fail to actuate. Test each one under flow.
CAP 437 expects the full system to be tested on commissioning and every year, including foam quality from the discharge points.
Documentation
- Design calculation showing the rate, area and D-value
- Foam concentrate type, approval certificate and latest laboratory test
- Annual test reports, including finished foam samples
- Nozzle or monitor layout drawing against the deck markings
- Pump flow and pressure data at the helideck elevation
Integration and compatibility
A foam system is only as good as its water supply. Confirm that the fire pumps and hydrants deliver the design flow at the helideck height, with a back-up source. DIFFS nozzles must sit clear of the TD/PM circle, the H and the deck exits, so their pipework belongs to one deck's layout. Monitors need clear arcs across the deck and must not breach the obstacle sectors. Machinery space foam belongs with foam and CO2 systems, not here.
Refurbishment and recertification
A used DIFFS suits an identical deck or a sister unit, because its nozzle positions are cut to one layout. Monitors, foam tanks and proportioning skids move between units more easily. Recalculate the rate for your design helicopter, refill with tested concentrate, and run a full flow test with foam sampling before the first helideck inspection.
FAQ
Frequently asked questions
What foam application rate does CAP 437 require on a helideck?
CAP 437 requires at least 5.5 litres per square metre per minute with ICAO level B foam and 3.75 with level C foam. The area is a circle with a diameter equal to the design helicopter's D-value. A solid plate deck needs at least five minutes of discharge, which sets the concentrate stock.
What is a DIFFS on a helideck?
A DIFFS is a deck-integrated fire-fighting system, a set of nozzles fitted in the helideck surface that spray foam or seawater over the landing area. CAP 437 now names it the preferred alternative to fixed monitors at the deck edge. Nozzles are pop-up or flush types, and some systems discharge seawater only.
Can a used DIFFS be fitted to a different helideck?
Usually only to a deck of the same size and layout. DIFFS nozzle positions and pipework are designed around one deck's markings and exits, so a used set suits a sister unit. Fixed monitors, foam tanks and proportioning skids are easier to reuse on another deck after recalculating the rate.
How often must a helideck foam system be tested?
A helideck foam system must be tested on commissioning and every year after that, under CAP 437. The test covers the whole foam production system, including samples of finished foam from the discharge points. Ask for the last annual report and the concentrate's latest laboratory test on any used system.
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