I came across these two books in a local Charity Shop. They had others but I thought I'd try two before buying loads.
The best way I can describe them it Biggles meets H.P. Lovecraft.
The first is Squadron of the Scorpion (1935) and the second Scourge of the Sky Beast (1936).
For more details see this Wiki link.
I'll let you know what I think of them. once I have started reading them.