Guidance on the mixing of icing inhibitors to helicopter fuel offshore

  • Operations Notice: 76
  • Issue Date: November 2008


This guidance is for dutyholders operating installations served by helicopters requiring icing inhibitors (FSII) to be mixed with their fuel load when the outside air temperature (OAT) falls below a specified level.


During a recent offshore inspection in the Southern North Sea (SNS) HSE Inspectors were made aware of a document, from a specialist aviation fuel supplier, serving notice that fuel supplied to helicopter operators in the SNS for use in both Sikorsky S76 and AS365 Dauphin helicopters will no longer be pre-mixed with FSII onshore. The document set out the reasons for this, gave a description of the FSII injector and its operation, the procedures for calibration and maintenance and for the testing of the fuel/FSII mix offshore. Since not all helicopter types require FSII to be mixed with fuel, concern has been expressed that uncertainties about whether a helicopter requires FSII or not could lead to mistakes being made.

Current Situation

In the UK offshore fleet, the only helicopters currently requiring FSII to be injected into the Jet A-1 fuel supply when the OAT falls below a specified level are:

  • AS 365 Dauphin at OAT below +5 degrees C
  • Sikorsky S76 at OAT below +4 degrees C

These two helicopter types generally operate in the Southern Sector and Morecambe Bay areas. The S76 may occasionally be operated out of Aberdeen to serve the Outer Moray Firth, Central North Sea, and other areas.

General advice to offshore installation managers (OIM's) / helicopter landing officers (HLO's) when preparing helideck facilities for winter operations is as follows:

  1. If the AS365 Dauphin or S76 is the current contract helicopter or may be used for ad-hoc flights, dutyholders should contact the helicopter operator to confirm that FSII additive will be required for offshore refuels.
  2. Ensure the offshore helifuel system FSII injection equipment is correctly installed, properly maintained and correctly calibrated.
  3. Ensure that sufficient stock of FSII additive is available on the installation for the estimated fuel uplifts.
  4. Prior to fuel deliveries to AS365 / S76 helicopters offshore, HLO to confirm with a member of the flight crew that FSII will be injected in the delivered fuel load.
  5. Record fuel delivery on the standard forms as normal and add a note that FSII has been mixed with delivered fuel load.
  6. In the event of any uncertainty, dutyholders should first consult directly with their specialist fuel suppliers, well ahead of the winter season.

Further Information

Any queries relating to this notice should be addressed to:

Health and Safety Executive
Hazardous Installations Directorate
Offshore Division
Lord Cullen House
Fraser Place
AB25 3UB
Tel: 01224 252500
Fax: 01224 252648

This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance as illustrating good practice

Updated 2021-02-16