Biggles and the Black Peril by W E Johns
When zero visibility forces Biggles to land his Vandal amphibian aircraft on the North Sea he thinks he's just got a spot of aeroplane bother. Bigger trouble is ahead for Biggles when he takes an unchartered ride in a flying boat manned by 'Blackbeard' - a cohort of the Russian Airfleet and accomplice in a plot to bomb Britain.