Helimission helicopters often land in dusty villages. Generally speaking, helicopters don’t like dust. Dust wears down the edge on the rotor blades as well as the compressor part of the engine. The compressor has multiple blades and turns at 50,000 revolutions per minute (A good kitchen hand blender reaches a maximum of 17,000 rpm).
To protect our turbines from sand and dust, we have installed a sand filter certified for our machines (AS–350/H125). This filter must be maintained. At Helimission we often need to clean the filter after a 5-day operation in the bush. The filter is then washed and re-soaked with a special oil. The compressor is also washed, especially after flights over or near the sea. The salty sea air promotes corrosion (rust). We also wash the complete helicopter inside and out regularly.
If the air filter does not allow enough air to pass through to the compressor / turbine due to a lot of dust and dirt, the performance of the turbine is reduced. This is indicated by a warning light in the cockpit. If the pilot still needs a lot of power from the turbine, for example when taking off or landing, he can then open two bypass flaps and let the air pass unfiltered to the compressor. It is better to have a little more wear on the compressor blades than risk a crash landing due to lack of power.
The other day I had the job of replacing the air hoses responsible for the indicator (warning light) in the cockpit. Our maintenance manager, Dalee, has introduced me patiently to this work. When installing the filter unit, it is important to adjust the screws carefully to avoid stress cracks in the filter holder. This is one of the various “tricks” that I have learned from Dalee’s years of experience.
Jan, Mechanic
