The North American P-51 Mustang was one of the very best air superiority fighters in the European Theater during World War 2 and had the range to escort bombers all the way to Germany and back. Many P-51 pilots moved up to general officer billets and they sang the praises of ‘their aircraft’.
However it was a poor ground attack fighter. For that role, the F/A, there was nothing better than the P-47 Thunderbolt (jug). And later versions of the P-47 with its beefed up power plant and four blade prop was a war winner. It had a lot of firepower and it could fill any role including the role occupied by the P-51.
Fast forward to 1956, when Cavalier Aircraft, bought the rights to the Mustang from North American Aviation. The P-51 eventually became the Turbo Mustang III.
In 1968, in response to an Air Force search for a counterinsurgency aircraft to fight in Southeast Asia, the Turbo Mustang III moved to Piper Aircraft, which tinkered with the design. In 1971 the PA-48 Enforcer emerged as Piper’s bid for the COIN contract, but time had moved on. The A-1, an excellent ground attack aircraft (sort of a successor to the P-47) was being phased out and a far more lethal aircraft took its place.
The Air Force chose the A-10. Who wouldn’t?
The Air Force awarded Piper an $11.9 million contract in 1981 to build two prototype PA-48s for evaluation (call it a sop if you will). The evaluation team found the PA-48 Enforcer easy to operate and maintain, but they also concluded it was underpowered, lacked maneuverability with a full bomb load and was too fragile, which was why the P-51 wasn’t a good ground attack aircraft in the first place.
And that is the end of the story.