Piper Enforcer

Last revised March 15, 2014

This saga of the P-51 Mustang ends with the story of the Enforcer--an attempt to bring the Mustang back in to service in the 1980s!

Even the end of the Korean War and the official withdrawal of the last Mustang from ANG service in 1957 was not to be the end of the story for the Mustang. Many Mustangs served with foreign air arms, remaining as first-line equipment well into the 1970s. Hundreds of surplus Mustangs ended up on the civilian market, and many of these were used on the unlimited racing circuit during post-war years. Many are still being raced at present.

The last Mustang officially left ANG service in 1957. It is not generally known, but there have been periodic attempts to reintroduce the Mustang into USAF service in the years after that. In fact, such efforts continued up until the early 1980s.

The final withdrawal of the Mustang from USAF and ANG service dumped hundreds of P-51s out onto the civilian market. The rights to the Mustang design were purchased from North American by the Cavalier Aircraft Corporation, which attempted to market the surplus Mustang aircraft both in the US and overseas. In 1967 and again in 1972, the USAF procured additional batches of Mustangs from Cavalier, most of them destined for air forces in South America and Asia that were participating in the Military Assistance Program (MAP). These aircraft were remanufactured from existing F-51D airframes but were fitted with new V-1650-7 engines, a new radio fit, tall F-51H-type vertical tails, and a stronger wing which could carry six 0.50-inch machine guns and a total of eight underwing hardpoints. Two 1000-pound bombs and six five-inch rockets could be carried. They all had an original F-51D-type canopy, but carried a second seat for an observer behind the pilot. Although these new Mustangs were intended for delivery to South American and Asian nations through the Military Assistance Program (MAP), they were delivered with full USAF markings and were allocated new serial numbers (67-14862/14866, 67-22579/22582 and 72-1526/1541). One additional Mustang was a two-seat dual-control TF-51D (67-14866) with an enlarged canopy and only four wing guns.

In 1968, the US Army employed a vintage F-51D (44-72990) as a chase aircraft for the Lockheed YAH-56 Cheyenne armed helicopter project. This aircraft was so successful that the Army ordered two F-51Ds from Cavalier in 1968 for use at Fort Rucher as chase planes. They were assigned the serials 68-15795 and 65-15796. These planes had wing-tip fuel tanks and were unarmed. Following the end of the Cheyenne program, these two chase planes were used for other projects. One of them (68-15795) was fitted with a 106-mm recoilless rifle for evaluation of the weapon's value in attacking fortified ground targets.

Cavalier believed that the Mustang design still had potential for further development. In the late 1960s, the company began to explore the possibility of replacing the Packard Merlin piston engine of the F-51D with a turboprop engine. The owner of Cavalier, Dave Lindsay, preferred to use the Lycoming T55 turboprop as the powerplant of the reengined Mustang, but was unable to obtain one. In 1968, the company mounted a 1740 e.s.h.p Rolls-Royce Dart 510 turboprop into a F-51D and flight-tested the aircraft as the Turbo-Mustang III. It bore the civilian registration number of N6167U.

However, the Cavalier company decided to sell the rights for further development to the Piper Aircraft Corporation, and cancelled any further work on the re-engined Mustang project. On November 4, 1970, the Dart-powered Mustang prototype was delivered to the Piper factory at Vero Beach.

At that time, the US was embroiled in the Vietnam War, and combat experience indicated that there was a need for a low-cost, high-performance close-support aircraft for use by foreign air forces obtaining MAP assistance. This project was given the name Pave Coin.

In pursuit of production contracts under the Pave Coin program, the Piper company undertook a more ambitious Mustang conversion effort. One single-seat F-51D and one two-seat TF-51D airframe were fitted with the 2455 s.h.p. Lycoming T55-L-9 turboprop engine. The project was given the name Enforcer by Piper. The first Enforcer conversion was flown on April 19, 1971. The second conversion (civilian registration number N202PE) flew for the first time on April 29 1971, but crashed due to a structural failure at Vero Beach, Florida on Jul 12, 1971. Later that year, the USAF evaluated one of these Enforcers and confirmed the original performance claims, but did not show very much enthusiasm for the project.

Even though the USAF never saw any use for the Enforcer, Congressional pressure led eventually to a contract in September 1981 for Piper to construct two new prototypes for evaluation. They were known under the company designation of PA-48. The two PA-48 prototypes were given civilian registrations rather than military serial numbers, and were never given any military designations.

The PA-48 Enforcer bore only the slightest resemblance to the F-51D--only ten percent of the parts were in common. The fuselage was lengthened by 19 inches aft of the wing and larger tail surfaces were fitted. Power was provided by a Lycoming T55-L-9 turboprop. The familiar trademark Mustang ventral scoop was completely removed, and a large turboprop exhaust was fitted on the left-hand side of the fuselage just ahead of the cockpit. A Yankee rocket ejector seat was fitted in the single seat cockpit. Provisions for wingtip tanks were made, and ten underwing hardpoints were fitted. The fixed wing-mounted guns were removed, and all gun armament was carried within underwing pods. The two PA-48s first flew on April 9 and July 8, 1983 respectively, and the USAF conducted its evaluations at Elgin AFB and Edwards AFB during 1983/84. Gross weight was 14,000 pounds. Maximum speed was 403 mph and cruising speed was 363 mph. Service ceiling was 37,600 feet and combat radius (with two gun pods) was 469 miles.

The PA-48 Enforcer was unsuccessful in obtaining any production orders, and both prototypes were put in storage by the USAF in late 1986. One of them (N481PE) is now on display in the Annex building at the WPAFB Museum in Dayton, Ohio. The other Enforcer is on display at the Edwards AFB Flight Test Museum.


  1. United States Military Aircraft since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  2. Classic Warplanes: North American P-51 Mustang, Bill Gunston, Gallery Books, 1990.

  3. E-mail from Howard Austin, who was a test pilot on the Cavalier Turbo Mustang III.

  4. E-mail from Joe Hawkins on location of second PA-48.