AAIB investigation to DHC-8-402 Dash 8, G-JECR, 15 November 2018
Pitot static probe contamination, Exeter Airport, 15 November 2018.
Summary:
Whilst climbing to FL190 en-route to Charles De Gaulle Airport, Paris the pilots received an alt mismatch message and they elected to return to Exeter Airport. Following an inspection after landing, a small white crystalline deposit was found covering three of the four static pressure holes on the left primary pitot static probe. It is probable that the use of a non-approved product, to improve the seal between a test adaptor and the pitot static probe during maintenance immediately prior to this flight, may have resulted in the blockage of the static holes and led to the alt mismatch message. Two Safety Recommendations have been made; one to the air data accessory kit manufacturer and one to the aircraft manufacturer to improve the instructions for the use of testing kits when carrying out leak tests of the pitot/static system and to only use approved lubricants. The maintenance organisation has taken Safety Action to introduce tighter controls on the test kit equipment.
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