No posts were found because the word a41-208 is not contained in any post.
The same thing happens if I put in a USAF serial, e.g. 63-8028 (today's RCH953 flight going home to Alaska) or a civilian registration (G-ZIOO, etc.). However, the search does work if I put in an RAF serial (e.g. ZK373). Therefore, it would appear that the dash must be a problem character.
Is there any chance that the forum search facility can be extended to accept keywords that contain non-alphanumeric characters like "-" (a dash)?