The study was undertaken after the undercarriages of SAS planes collapsed in Denmark and Lithuania, causing the airline to cancel all flights using the Q400 planes.
In both cases, the fault was caused by rusty bolts on the hydraulic cylinders used to raise and lower the landing gear.
“I have heard from several other airlines with these Dash planes that they have discovered similar faults,” said SAS inspector Karl-Erik Mårtensson.
“I am surprised that so many planes were affected considering they were maintained entirely in accordance with the existing maintenance programme. It shouldn’t have been possible for this fault to occur,” he added.
The airline said it had carried out maintenance checks at regular intervals after a recommended number of flights.
“We have followed every single step of the maintenance programme,” said SAS spokesman Bertil Ternert.
The Dash 8-Q400 planes in the SAS fleet were supplied by Canadian manufacturer Bombardier. SAS said it did not want to comment on whether Bombardier had provided insufficient guidelines.
“It’s not possible to answer that question until the Danish and Lithuanian accident commissions have completed their work,” said Ternert.