Originally Posted by
nigelw
There isn't any 4 hour daily limit, there is a 13 hour daily limit that can go up or down a bit depending on various things (for example timezones crossed or how long off duty before hand), and there are weekly, fortnightly, monthly, and yearly limits as well. But no daily 4 hour limit
The route is LHR/LCA
I don't believe the respondent to your OP was implying their was a 4 hour duty limit. But, if you do the math, 2 x 4 hour sectors, with report time, clear time, turnaround, generally gets a crew nearer to the duty limit, so they tend to be the longest sectors that are return crewed.