I think most often when we think of prototype aircraft its as the first example of some famous type. But of course the term actually has much broader usage. There are actually four completely different sorts of prototypes I’ll look at for this theme build.
One will be exactly that most expected sort. But I’ll also do one that’s an established type’s alternate. Any time there was a significant change to an airframe it could lead to a new prototype. One famous example comes to mind is the P-51 Mustang, when two early examples were held back for conversion to a new Packard built Merlin engine they became “XP-51B”, test beds for the new power-plant. Later yet, the rear fuselage was cut down for an improved visibility bubble canopy; the first experimental build was tagged “XP-51D”. Which is all to say any major aircraft type may have several “prototypes”. In US usage this meant an “X” in front of the designation. In German usage this usually meant a “V” suffix. Every nation’s services had their own ways of tagging these things.
I will also build what was known as a service test, or pre-production prototype. Often with more unusual new designs a number are ordered before the main production run. In US use this is a “Y” prototype. These aircraft are often assigned to a test squadron that is trying to identify all service needs in addition to the best ways of using the new aircraft. Often, the various “Y” prototypes aren’t even all built the same way, and may have different features too. This is all about figuring out what’s going to be the best way to build, maintain and use the aircraft. Often these service test types do not lead to a production type, I suppose from a manufacturer’s perspective that means they failed the test. But the military user may still feel valuable lessons were learned that can be applied to whatever comes next.
Another prototype I’ll look at is straight up test aircraft. For my use here this is still stopping short of what we think of as pure “X” craft today; that is, at some point they were considered as a possible new combat type and are given a military designation. But before the prototype ever flies the operator has decided it will not lead to a production order. They are looking at experimental data, something that may impact another aircraft in development or an idea that’s not fully formed yet. Usually, if an aircraft technology is rendered obsolete before it ever flies the project dies. But in many cases, really more often that you might expect, someone feels there is still a lot to learn from a design they know will never advance. Several of the aircraft I looked at in my previous “Hypotheticals” theme were derived from this sort of project. But this time I will only look at things that were built and flown.
The four prototypes I will build are for a Mitsubishi A6M, Grumman F4F, Blohm und Voss
Bv 141 and Curtiss P-55.