Do 18 vs. Bv 138

[Jukka Juutinen]

Common sources claim that the Do 18 was supposed "obsolete" and that the Bv 138 replaced it because of that. However, why is the Do 18 supposedly more "obsolete" than the Bv 138?the references I have indicate that the Bv 138 wasn't much faster and had actually considerably shorter range. And if for example Eric Brown's comments are reliable, the Do 18 was much more pleasant to fly and handle.

[Nick Beale]

Interesting question.

Pure guesswork but the better defensive armament and payload of the Bv 138 may have been factors in the overwater reconnaissance and submarine hunting roles. Also I wonder if we should see the Do 24 as the Do 18’s replacement? The Do 18 was serving in the sea rescue role in the Battle of Britain and the first Do 24’s were arriving to take over that work. I don’t remember that the Bv 138 was used by Seenot units (don’t hold me to that, I haven’t checked).

[Mike Watson]

Hi. I do not have any books specifically on these types but Seeflieger (Adam Thompson) and Les Hyradavions de la LW Vols 1 and 2 (Roba and Neulen) do a good job of explaining the issues with respect to the obsolesence of the Do18 and the capbilities of the Bv138. I also have not seen Eric Browns reports on the Do18/Bv138 (I only have the 1977 Book) but would see no reason to doubt him. The fact that the Do18 was nicer to fly does not however mean that the Bv138 did not represent a considerable enhancement in operational capability.

With respect to performance figures you refer to I find that a number of sources do not provide equivalent data in particular for range/endurance. I have put together the following from a range of sources. There are some gaps for the Do18 - maybe someone else can fill them in. Hope it helps clarify the differences in this area at least.

[Graham Boak]

The Do.18 was more obsolete because it was considerably older and thus due for retirement soon, for which the Bv138 was to be the replacement. The requirement called for a considerable improvement in power, armour and general capability. For which it was inevitably heavier and thirstier, as part of the trade-off with all aircraft designs.

In practice, the light Do.18 was immediately found vulnerable to enemy fighters, even such obsolescent types as Gladiators and Skuas. In contrast, the Admiralty desired 4 cannon on its Seafires in order to deal with the armoured shadower that proving much less vulnerable (i.e. the Bv138). They didn't get them, but that's another story. Having a third engine probably provided some of the benefit.