Managing Interruptions: HEMS Call-Out During Engine Rinse

Managing Interruptions: HEMS Call-Out During Engine Rinse – Panel Lost (ANWB Airbus EC135T2+ PH-MAA)

On 7 February 2022 air ambulance Airbus Helicopters EC135T2+ PH-MAA of ANWB Medical Air Assistance suffered the in flight loss of an engine inspection panel shortly after departure from Groningen Airport.

ANWB Airbus EC135T2+ PH-MAA at Groningen (Credit: DSB)

According to the Dutch Safety Board (DSB) safety investigation (issued in March 2023), the operator conducts an engine rinse “every 5 flying hours / 3 days, or after flights over sea and/or a polluted environment”.   This involves the aircraft commander in the cockpit and a second person operating the necessary ground support equipment.  The investigators explain that:

The procedure required the engine cowlings of the EC135T2+ to be opened in order to access the compressor rinse connection and to be closed after the rinsing procedure was completed.

The…procedure also stipulated a plan in case of a Helicopter Emergency Medical Service (HEMS) scramble during the rinsing procedure.

In this case a call-out did indeed interrupted the task.  Shortly after take off…

…the pilot heard a noise and suspected the helicopter had struck a bird.

Another ANWB EC135T2+ had indeed suffered a bird strike on 14 January 2021.  Investigators note that:

There were no indications or warnings in the cockpit of a helicopter system malfunction and the commander decided to continue the flight.

However shortly after the call out was cancelled anyway and the helicopter proceeded to return to base. Only after landing was an engine inspection panel found to be missing.

The investigators conclude

It is likely that the right engine cowling was not properly closed after the engine compressor rinsing procedure was interrupted by a HEMS scramble. Consequently, as a result of aerodynamic overload, it departed the helicopter during the flight.

Our Observations

It is good that the operator’s engine rinse procedure reportedly considered the task could be interrupted by a call-out.

A lazy analysis would be to simply conclude there was a ‘failure to follow procedures’.  That is lazy because:

  1. the DSB don’t actually describe what was expected in the event of an interruption
  2. it fails to recognise that by their very nature interruptions and distractions break and disrupt procedural flow.

For this specific task one advantage is that it needs two people, so there are two people who can be used to cross-check key steps to return the aircraft for flight (e.g. disconnecting GSE, securing panels etc).

Safety Resources

The European Safety Promotion Network Rotorcraft (ESPN-R) has a helicopter safety discussion group on LinkedIn.  You may also find these Aerossurance articles of interest:

You might find these safety / human factors resources of interest:

The UK CAA has issued this infographic on distraction:

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