Mitsubishi Heavy Industries (MHI), a name synonymous with Japan’s illustrious aviation heritage, has made indelible marks on the aviation world with its innovative aircraft designs. Among these is the MU-300, known as the “Diamond,” which later evolved into the renowned Beechjet. This transformation reflects the legacy of Mitsubishi’s aviation expertise and its impact on the global aircraft market.
Mitsubishi’s prominence in aviation dates back to before and during World War II. After the war, Japan’s vast industrial empires, including Mitsubishi, were disbanded and their names temporarily forbidden. However, with the end of the Occupation in April 1952, Mitsubishi resumed its historical name and reformed into Mitsubishi Heavy Industries in 1964.
MHI spearheaded the rebirth of Japan’s aviation industry post-Occupation. In the mid-1950s, Mitsubishi was integral to developing the YS-11 twin-turboprop airliner and later, the MU-2 high-wing, small-cabin twin. The MU-2 saw considerable success, with over 700 units built by 1987. Concurrently, MHI also produced U.S.-designed fighters during the Cold War, further solidifying its aviation prowess.
Entering the Business Jet Market
Encouraged by the success of the MU-2, Mitsubishi ventured into the general aviation market with the MU-300 Diamond business jet in 1977. The Diamond, a conventional jet with all-swept surfaces and a T-tail, featured advanced aerodynamics and powerful Pratt & Whitney Canada JT15D-4 turbofan engines. The aircraft accommodated two pilots and seven or eight passengers, offering a blend of performance and comfort.
The first prototype flew on August 29, 1978, and after trials in Japan, was shipped to the U.S. for FAA Part 25 certification, achieved on November 6, 1981. Production began in San Angelo, Texas, from Japanese-built kits, with customer deliveries starting in July 1982. Despite initial favorable impressions, the aircraft showed a tendency to “snake” at high speeds, leading to subsequent modifications.
Evolution and Transition
In 1983, Mitsubishi introduced the Diamond 1A, featuring upgraded engines and increased maximum takeoff weight (MTOW). The Diamond II followed in 1984 with further enhancements, including more powerful JT15D-5 engines and increased fuel capacity. However, a significant change occurred in December 1985 when Beechcraft acquired the design rights for the Diamond II, rebranding it as the Beechjet 400.
Beechcraft, under Raytheon ownership, continued to evolve the aircraft. The Beechjet 400A, introduced in 1989, incorporated advanced avionics and interior redesigns. Nearly 700 units of this model were built, including military variants like the T-1A Jayhawk for the U.S. Air Force and the T-400 for the Japan Air Self-Defense Force.
The Hawker Legacy and Modern Upgrades
In 1993, Raytheon’s acquisition of British Aerospace’s business jet line led to the Beechjet 400A being rebranded as the Hawker 400. The 400XP, introduced in 2003, featured additional payload capacity and minor improvements. However, economic challenges in the late 2000s led to the cancellation of the planned 450XP and the eventual failure of Hawker Beechcraft in 2013.
Despite the end of production, the MU-300 lineage continued to thrive through remanufacturing programs. Nextant Aerospace’s 400XT and Textron’s 400XPR upgrades revitalized existing airframes with modern engines and avionics, enhancing performance and efficiency. These programs ensured that the MU-300’s legacy endures, with the aircraft remaining popular among corporate, air taxi, and private owners.
From its origins as the Mitsubishi Diamond to its evolution into the Beechjet and beyond, the MU-300 has left a lasting legacy in the aviation industry. Its journey reflects the innovation and resilience of Mitsubishi Heavy Industries and the enduring appeal of its designs. As modern upgrades continue to breathe new life into these aircraft, the MU-300 remains a sparkling gem in the history of aviation.
