In a more recent example, the F35 Jet is having delay and cost overrun problems. I hear that one of the reasons is that there is 3 different version of the same jet and it may have been cheaper to design 3 completely different planes oriented toward each niche.
The 3 configurations are:
A) Conventional takeoff and landing (CTOL). A normal fighter jet, intended to replace the F16.
B) Short takeoff and vertical landing (STOVL). This model essentially has a big fan in it to allow it to hover and land on aircraft carriers.
C) Similar to A, but with larger, foldable wings and a stronger tailhook for landing with a carrier arrestor cable.
Model B is intended for the Marine Corp, and C is intended for the Navy.
Now I admit that I am fairly uninformed about military hardware and design, but I think something can be concluded from the F35 program issues.
And the exact same thing happened with the TFX in the '60, except it was proposed to also fill the air superiority role that the F-22 was designed for, and not the V/STOL one. The F-111, in the deep interdiction role, was the only surviving model.
Not clear the Navy or Marines had anything to do with this Charlie Foxtrot, at least prior to the decision to save money by having only one basic plane.
This is a common peacetime "savings" measure. Same thing happened with the M14 rifle, which had about the shortest time as a combat rifle in US history (although part of that was due to the utterly corrupt Army institution that procured it when pretty much every other contemporary battle rifle design was better, except for trigger pull).
If I remember correctly, the Marines use amphibious assault ships that don't have conventional runways (such as on Navy aircraft carriers) to take off/land on thus the need for a VTOL aircraft. A VTOL wouldn't be necessary for a Navy aircraft carrier (example: F18 Super Hornet). Another example of this is why the Marines wanted to keep the Harrier around for so long before it became too problematic and expensive hence why they wanted VTOL capabilities on the F35 JSF (also another factor in the cost/time overruns).
The 3 configurations are:
A) Conventional takeoff and landing (CTOL). A normal fighter jet, intended to replace the F16.
B) Short takeoff and vertical landing (STOVL). This model essentially has a big fan in it to allow it to hover and land on aircraft carriers.
C) Similar to A, but with larger, foldable wings and a stronger tailhook for landing with a carrier arrestor cable.
Model B is intended for the Marine Corp, and C is intended for the Navy.
Now I admit that I am fairly uninformed about military hardware and design, but I think something can be concluded from the F35 program issues.