Over the years there have been a number of issues with proper cowling door latching. And procedural and sticker changes have been implemented.
Quite recently there was a more serious case in the UK which caused an in-flight engine fire (no casualties).
One of the basic things with the cowling latches is that they are at the bottom centerline. And you really have to go down on your knees to be able to see if they are properly latched and locked. Murphy ...
In the UK case maintenance had half-latched the doors because they were not finished yet. Were called away. Returned but picked the wrong plane. That plane had its cowling doors closed. So the assumed someone else had closed it. Leaving the doors half latched.
The pilot doing the preflight check had not noticed that the cowldoors were not properly closed. In the specific case there even was a gap visible while standing, because of the half-latched position.
Maintenance had not followed procedures. And yes these require putting and later retrieving (labels/flags) from the cockpit. If they had followed procedures, the pilots even when missing the opening on the walkaround, would have seen the labels in the cockpit.
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When you are interested in the subject the UK case gives a nice overview:
AAR_1-2015_G-EUOE 24May2013 A319 Heathrow
Last edited by A0283; 25th Feb 2016 at 09:05.
Reason: adding UK case reference