The Mitsubishi Mu-2, Diamond, & MRJ

v1.0.1 / 01 mar 17 / greg goebel

* In the 1960s, the Mitsubishi company of Japan introduced a twin-turboprop light transport, the "MU-2", that proved very successful. It was followed in the early 1980s by the "MU-300 Diamond", which was also successful, though most production of that variant was by Beechcraft. Mitsubishi is now following up the MU-300 with the "Mitsubishi Regional Jet (MRJ), which is in advanced development. This document gives a history and description of the MU-2, MU-300, MRJ -- and also the Honda "HA-420 HondaJet" light executive jet.

Mitsubishi MU-2



* In 1956, the Mitsubishi firm of Japan, famed for its World War II Zero fighter, began work on its first postwar aircraft design -- a light twin turboprop transport for civil and military use. The result, the "XMU-2", performed its initial flight on 14 September 1963. This first prototype, and the three initial series "MU-2A" pre-production machines, were powered by Turbomeca Astazou Mark II turboprops with 420 kW (562 SHP), driving three-bladed reversible Hartzell props.

Following the MU-2A, 34 production "MU-2B" machines were then produced, along with an upgraded MU-2A, all powered by Garrett TP331-25AA or -25AB turboprops with 430 kW (575 SHP) each -- not counting a fair effective additional increment of power from exhaust thrust. Some sources also claim that the MU-2B had a wider wingspan than the first four MU-2s. All subsequent MU-2 variants had TPE331 engines, including a series of stretched machines, discussed later. Incidentally, the name "Peacock" is associated with the MU-2, but it's not often used in literature, and may have been a late innovation.

The MU-2 -- "Mitsubishi Utility 2"-- was built mostly of aircraft aluminum. It featured high, straight, flat wedge-shaped wings, a wedge-shaped tailplane with narrow leading-edge root extensions, a swept tailfin with a smoothly curving forward fillet, and tricycle landing gear. The wing featured full-span trailing-edge double slotted flaps, with roll control provided by spoilers; the full-span flaps ensured a low stall speed on take-off and landing, while the spoilers could provide more effective control at low speeds than ailerons. Flight control surfaces were manually driven, except for electrically-driven flaps.

Mitsubishi MU-2

The twin-wheel nose gear retracted backward, while the single-wheel main gear tucked up into the sides of the fuselage. The landing gear was electrically actuated. The MU-2B had integral wing tanks and fixed wingtip tanks with a capacity of 246 liters (65 US gallons) each; the tip tanks were not fitted to the XMU-2 or MU-2As. They were quickly replaced in later variants by extended wingtip tanks with 341 liters (90 US gallons) each, with late-production variants also featuring four-bladed Hartzell propellers. There were two cockpit crew and seats for seven passengers, with the passenger door on the left rear fuselage, hinged on the left, and an emergency exit under the right wing. The aircraft was pressurized and climate-conditioned.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                11.94 meters        39 feet 2 inches
   wing area               16.55 sq_meters     178 sq_feet   
   length                  10.13 meters        33 feet 3 inches
   height                  3.94 meters         12 feet 11 inches

   empty weight            2,685 kilograms     5,920 pounds
   MTO weight              4,500 kilograms     9,920 pounds

   cruise speed            585 KPH             365 MPH / 315 KT
   service ceiling         10,120 meters       33,200 feet
   range                   2,705 kilometers    1,680 MI / 1,460 NMI
   _____________________   _________________   _______________________

Not everyone was enthusiastic about the MU-2's looks, but it did have a clean and businesslike appearance. The MU-2 had plenty of power and was regarded as a "hot" aircraft in its class; it also had good short-field performance. The MU-2 had a high accident rate initially, partly due to design issues that were soon rectified; more so because pilots weren't used to its high performance, or the fact that it handled differently under engine-out conditions than other small prop twins. Recommendations for improved flight procedures and training reduced the accident rate to a much more tolerable level, and the MU-2 would become recognized as being at least as safe as any other aircraft in its class.

* After initial manufacture in Nippon, Mitsubishi set up an arrangement with Mooney in the USA to built, sell, and support the MU-2 internationally, with Mooney setting up an assembly plant in San Angelo, Texas, in 1965. Major assemblies were shipped from Japan, with Mooney installing engines and props, avionics, then fitting out the interior. In 1969, Mooney was in financial trouble, so Mitsubishi took over the San Angelo plant. Following the MU-2B, variants included:

As mentioned above, there were two specialized militarized variants of the short-fuselage MU-2s. The first was the "MU-2C (MU-2B-10)", which was built for the Japan Ground Self-Defense Forces (JGSDF), service designation being "LR-1". It was for liaison and photo-reconnaissance work, with a vertical and an oblique camera in the belly. Four MU-2Cs were built, the first having no wingtip tanks -- this apparently being the only production MU-2 that didn't have them -- instead having an extra fuel tank in the rear. The JGSDF then acquired 16 MU-2Ks in the same configuration, also giving them the "LR-1" designation (for "Liaison-Reconnaissance"), for a total of 20 LR-1s. There are photos of some of the LR-1s with "cheek" fairings that could be used to accommodate more surveillance gear and even machine guns, but this doesn't appear to have been a normal fit.

Mitsubishi LR-1

The second was the "MU-2E", internal designation unknown, a search and rescue (SAR) variant of MU-2DP for Japan Air Self-Defense Forces (JASDF), service designation being "MU-2S". It featured radar in a thimble nose radome, bulged observation windows, larger fuel supply, and a sliding door that could be opened in flight for dropping rescue kit. 16 MU-2Es were obtained. Images suggest that some of them had the small wingtip tanks, though most had the big tanks.

No foreign military services acquired specifically militarized MU-2s, but from the late 1980s the US Air Force acquired a fleet of MU-2K and MU-2M machines, to be flown from Tyndall Air Force Base in Florida for "Air Battle Management (ABM)" training. The MU-2s simulate opposing fighter teams, with ABM controller trainees directing their respective teams. The MU-2s still seem to be in service at Tyndall, being given an engine upgrade from 2012.

* The first of the stretched MU-2 variants was the "MU-2G (MU-2B-30)", which featured a fuselage stretched by 1.91 meters (6 feet 3 inches), for seating 8 to 11 passengers; main landing gear in sponsons to free up internal space; forward-retracting nose gear; a larger, straight-edged tailfin fillet; and twin fixed ventral fins under the tail. Despite its greater size, it retained the TPE331-1-151A engines, with the 495 kW (665 SHP) derating. Initial flight was on 10 January 1969; 46 were built.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                11.94 meters        39 feet 2 inches
   wing area               16.55 sq_meters     178 sq_feet   
   length                  12.01 meters        39 feet 5 inches
   height                  4.17 meters         13 feet 8 inches

   empty weight            3,085 kilograms     6,800 pounds
   MTO weight              4,900 kilograms     10,800 pounds

   cruise speed            555 KPH             345 MPH / 300 KT
   service ceiling         9,320 meters        30,800 feet
   range                   2,500 kilometers    1,555 MI / 1,350 NMI
   _____________________   _________________   _______________________

The MU-2G was followed by refined stretched variants:

There were no specialized military variants of the stretched MU-2s, but the JASDF obtained four MU-2Js for navaids calibration duties, and apparently some military services obtained a few for utility and liaison work.

Mitsubishi MU-2 Marquise

* Final production tallies for the MU-2 were as follows:

   variant            number        notes 

   short     long     short   long        

   XMU-2                  1         Proto with Astazou engines.
   MU-2A                  3         Pre-series machines, Astazous.
   MU-2B                 34         Initial production, TPE331s.
   MU-2C                  4         JGSDF LR-1 liaison variant.
   MU-2D                 18            
   MU-2DP                 3         Introduced large tip tanks.
   MU-2E                 29         JASDF MU-2S SAR variant.
   MU-2F                 95
              MU-2G             46  1st stretched MU-2.
              MU-2J            108 
   MU-2K                 83         Including JASDF MU-2S SAR.
              MU-2L             29 
   MU-2M                 27
              MU-2N             36  Went to 4-blade props.
   MU-2P                 31         Went to 4-blade props.
   Solitaire             57
              Marquise         139
   SUM:                 385    358     TOTAL 743
   There are variations between sources on production numbers, totals 
   given the range of 700 to 750.

The majority of MU-2s were built in the US, where production ended in 1986. The last Japan-built MU-2 was rolled out in early 1987. The MU-2 remains in widespread civilian service, most machines still having plenty of airframe life remaining. There have been third-party upgrades of MU-2s for cargo, combination cargo-passenger, and medical evacuation use, while upgrades have been on offer to fit MU-2s with a modern "glass cockpit".



* In the mid-1970s, Mitsubishi began work on an executive jet, with the first of two "MU-300 Diamond" prototypes performing its initial flight on 29 August 1978, with the second following in December. As it emerged, the Diamond was of conventional executive jet configuration, with all-swept flight surfaces including a low mounted wing and tee tail; turbofans mounted on each side of the tail; and tricycle landing gear. Following development, the two prototypes were shipped to Mitsubishi Aircraft International INC, the parent company's American subsidiary, for certification as the "Diamond I". FAA certification was granted in late 1981, with initial customer shipments in the summer of 1982. 63 Diamond Is were built at the plant in San Angelo, Texas, using assemblies shipped from Japan.

The Diamond I was made mostly of aircraft aluminum alloy. Its wings had a sweepback of 20 degrees at quarter chord and an incidence of three degrees. Each wing had trailing-edge flaps running almost the full span, with double slotted flaps inboard and single slotted flaps outboard, with a small aileron near each wingtip. There were spoilers above the wing to aid in roll control, as well as to act as airbrakes and lift dumpers. There was a small fence about a third of the way outboard on the wing. De-icing was by engine bleed air.

The tailfin had a long leading fillet, with a small yaw damper surface above the rudder. The tailplane featured elevators, and had variable incidence to handle flight trim. There was a ventral fin under the tail, and a small strake along each side of the tailfin. All landing gear assemblies had single wheels, the main gear hinging in the wings to retract towards the fuselage, the steerable nose gear retracting forward.

Mitsubishi MU-300 Diamond

Powerplants were Pratt & Whitney Canada (PWC) JT15D-4 turbofans with a take-off thrust of 11.1 kN (1.146 kgp / 2,500 lbf) thrust each, max cruise thrust being 94% of that. There were fuel tanks in the tail and integral wing tanks, with a total maximum useful capacity of 2,445 liters (646 US gallons). There were three refueling points, one in each wing, one in the tail.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                13.23 meters        43 feet 5 inches
   wing area               22.43 sq_meters     214.4 sq_feet   
   length                  14.73 meters        48 feet 4 inches
   height                  4.19 meters         13 feet 9 inches

   empty weight            3,765 kilograms     8,300 pounds
   MTO weight              6,395 kilograms     14,100 pounds

   cruise speed            760 KPH             470 MPH / 410 KT
   service ceiling         12,500 meters       41,000 feet
   range                   2,315 kilometers    1,440 MI / 1,250 NMI
   _____________________   _________________   _______________________

There were two flight crew and, typically, seven seats, with a toilet and a baggage compartment in the rear. Of course, the aircraft was pressurized and climate-conditioned. There was a forward-hinged passenger door on the left side of the fuselage in front of the wing, with fold-down airstair, and an emergency exit on the right side of the fuselage, above the front of the wing root. Avionics were conventional, including radios, navigation aids, air traffic control transponder, and color weather radar.

Mitsubishi MU-2 versus MU-300 Diamond

* In 1983, Mitsubishi announced development of the improved "Diamond IA", with uprated JT15D-4D turbofans, an electronic flight instrumentation system (EFIS), and increased take-off weight; another window was added on the left side of the fuselage. Initial deliveries were in 1984, with 27 built.

Mitsubishi then developed a further improved variant, with JT15D-5 engines, lower maximum take-off weight, but increased fuel capacity, as the "Diamond II". Mitsubishi only built a prototype, selling off the design to Beech in 1985, which then built 64 as the "Beechjet 400" from Mitsubishi assemblies. The production machines featured thrust reversers. In 1989, Beech introduced the "Beechjet 400A", featuring a Collins Pro Line 4 avionics system, including a glass cockpit, and a rearranged interior.

In 1990, Beech won a contract from the US Air Force for what would end up being a total of 180 slightly modified Beechjet 400s as the "Tanker / Transport Training System", for training KC-135, C-5, KC-10 and C-17 aircrews. Differences included militarized avionics, with the avionics moved from nose to rear to simply maintenance; an additional fuselage fuel tank, along with single-point fuel system refueling; better air conditioning; plus windshield and leading-edge reinforcement to deal with birdstrikes. The modified aircraft was designated the "Beech 400T T-1A Jayhawk", with initial deliveries in 1991 and introduction to service in 1992.

The Jayhawk normally flies just with trainee and instructor, but it can be fitted with four seats for passengers or observers. From 1997, the Jayhawk fleet was fitted with GPS navigation receivers. In something of an irony, the JASDF also obtained 13 400T trainers, similar to the T-1A but with thrust reversers.

Raytheon Beechcraft T-1A Jayhawk

In 1993 Raytheon, the parent company of Beech since 1980, bought the Hawker business jet product line from British Aerospace, with the Beechjet 400 then becoming the "Raytheon Hawker Beechcraft 400" to map it into the Hawker product line. In 2003, production went on to the "Hawker 400XP", the "XP" standing for "extra payload", with a 90 kilogram (200 pound) increase in MTO, thrust reversers, plus avionics and systems updates.

In 2006, Raytheon sold off Beechcraft, with the spun-off company announcing a "Hawker Beechcraft 450XP" in 2008. It was cancelled in 2009 due to the slow economy, which was just a prelude to the bankruptcy of the firm in 2013. Beechcraft did emerge again after a re-organization, but dropped the jet product line. A total of 953 400A / 400XP machines had been sold to that time, not including the military trainers.

* The company still supports the 400 series, but to a degree it has been taken over by Nextant Aerospace, a startup that was born in 2007 to remanufacture and update old business jets. The first product introduced by the firm was the "Nextant 400XT", a rebuilt and modernized 400A/XP with:

FAA certification was in October 2011. Hawker Beechcraft had been pushing a similar update, the "400XPR", which disappeared when the firm when bankrupt. In 2013, Nextant introduced the refined "400XTi", with a refined and more spacious cabin with better noise insulation, winglets, and other tweaks such as lithium batteries instead of lead-acid batteries. Nextant claims the 400XTi costs only about half as much as new-build competitors, but compared to the 400A has 50% more range, almost a third more fuel economy, and lower noise. The company has sold at least 40 to date.



* In 2004, the Mitsubishi firm of Japan announced development of the "Mitsubishi Regional Jet (MRJ)" small airliner, a twin-engine jetliner with a capacity of 70 to 90 passengers. Development was to be conducted by the Mitsubishi Aircraft Corporation, a partnership between majority owner Mitsubishi Heavy Industries and Toyota Motor Corporation, with assistance from Fuji Heavy Industries, a Toyota affiliate with experience in aircraft manufacture.

A cabin mockup and a model were displayed at the 47th Paris Air Show in 2007, with official program launch in 2008. The first of five Mitsubishi MRJ flight prototypes was rolled out in October 2014, with initial flight on 11 November 2015. The test program also included two ground-test articles. The prototypes were of the "MRJ90", with a nominal seat capacity of 90 passengers; it was to be followed by the shorter "MRJ70", with a nominal capacity of 70 seats.

Mitsubishi MRJ

The Mitsubishi MRJ is of conventional regional jetliner configuration, being a narrow-body aircraft with tricycle landing gear, a low-mounted wing, and swept flight surfaces -- the tailfin having a forward fillet. Although it was initially defined as an "all composite" aircraft, that was judged too aggressive, and it is primarily made of aircraft aluminum alloy, with a minority of composite assemblies, mostly in the tail section. It is powered by twin Pratt & Whitney PW1217G geared turbofans, with 78.3 kN (7,980 kgp / 17,600 lbf) thrust each, one engine under each wing. The engines are not only highly efficient, they have low noise and emissions.

The wing features Fowler flaps, ailerons, and leading-edge slats. The tail assembly is of conventional configuration, with rudder and elevators, the tailplane being all-moving. Flight controls are operated via a fly-by-wire flight-control system. All landing gear assemblies have twin wheels, the nose gear retracting forward, the main gear retracting inward from the inner wings towards the fuselage. The nose has a distinctive "duckbill" configuration.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                29.2 meters         95 feet 10 inches
   length                  35.8 meters         117 feet 6 inches
   height                  10.5 meters         34 feet 6 inches

   empty weight            25,190 kilograms    55,535 pounds
   MTO weight              39,600 kilograms    87,300 pounds

   max speed               Mach 0.78
   service ceiling         11,855 meters       39,000 feet
   range                   1,665 kilometers    1,035 MI / 900 NMI
   _____________________   _________________   _______________________

There are two cockpit crew, the cockpit featuring a Rockwell Collins Pro Line Fusion glass cockpit, with four color displays. The MRJ90's passenger configuration is up to 88 seats, in rows of four, with large-capacity overhead bins. There is a lavatory and a galley fore and aft, and a single cargo bay, in the rear. There are passenger doors fore and aft of the wing on the left side of the fuselage, with matching service doors on the right side, plus an emergency exit over each wing. An "extended range (ER)" variant, with range stretched to 1,665 kilometers (1,035 miles / 900 NMI) is planned, as well as a "long range (LR)" variant with range stretched to 3,295 kilometers (2,050 miles / 1,780 NMI).

Mitsubishi MRJ variants

The MRJ70 is 2.4 meters (7 feet 10 inches) shorter than the MRJ90, giving a length of 33.4 meters (109 feet 7 inches), 93% that of the MRJ90; empty weight is 97% that of the MRJ90, while passenger capacity is up to 76 seats. Engines are derated to 89% thrust of the powerplants of the MRJ90. Range of the standard version will be 1,520 kilometers (945 miles / 820 NMI); there will also be an "extended range (ER)" variant, with range stretched to 2,720 kilometers (1,690 miles / 1,470 NMI), plus a "long range (LR)" variant with range stretched to 3,370 kilometers (2,095 miles / 1,820 NMI). There has also been consideration of a stretched "MRJ100" variant, but there's been no commitment to it just yet.

A new production facility was built for the MRJ at Komaki Airport in Nagoya. Introduction to service of the MRJ90 is to be in 2018, the program having encountered a series of delays. The launch customer is All Nippon Airways. The Japanese government has considered buying a batch for use as VIP transports.



* In the late 1980s, the Honda company of Japan began to investigate a modern small business jet using the latest technologies, working with Mississippi State University's Raspet Flight Research Laboratory to build the "MH02" demonstrator, which performed its first flight on 5 March 1993. It featured a composite aircraft, a tee tail, a forward-swept wing, and a turbofan engine mounted above each wing. This engine placement scheme had been used on the unsuccessful German VFW-Fokker 614 jetliner in the 1970s, in that case simply to reduce weight and guard against foreign object ingestion; Honda saw it as useful for reducing high-speed drag, and wanted to investigate further.

The MH02 demonstrator was retired in the late 1990s, with Honda moving towards a production machine from that time. In 1999, the company began work on a small turbofan engine, the "HF118"; it led to the "HF120", developed in collaboration with GE Aviation. Work also proceeded on the "HA-420 HondaJet" production business jet, with a demonstrator performing its maiden flight on 3 December 2003, making its public debut at the EAA AirVenture air show in Oshkosh, Wisconsin, in July 2005. Honda began taking orders in 2006.

Honda set up the Honda Aircraft Company subsidiary to handle qualification, production, and sale of the HondaJet. Manufacture is to be performed in the USA, at Piedmont Triad International Airport in Greensboro, North Carolina. Initial flight of a pre-production was on 21 December 2010. The first production HondaJet performed its initial flight on 27 June 2014, and was displayed at the 2014 EAA Airventure.

Honda HondaJet

* The HondaJet is a low-wing wing aircraft, the fuselage being made primarily of composites, with aluminum wings and tailplane. It has tricycle landing gear, tapered wings and slightly swept tailplane, a swept tailfin with a forward fin fillet, and a turbofan mounted above and to the rear of each wing. The advantage of top-mounting is reduced weight and drag; the problem is that engine intake airflow can cause aerodynamic problems for the wings, a difficulty that Honda got around by placing the engines almost completely behind the wing. The topside mounting also reduces ground noise and vibration into the passenger compartment, as compared to tail mounting; as well as reduces the risk of foreign object ingestion into the engine during runway operations.

The distinctive drooped nose has a "laminar flow" configuration to reduce drag, while the cockpit is slightly domed to improve headspace. The engines are production HF-120 turbofans with FADEC, providing 8.9 kN (853 kgp / 1,880 lbf) thrust each; they are highly efficient and have low emissions. There are fuel tanks in each wing, in the wing center section, and in the rear fuselage, with single-point refueling.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                12.15 meters        39 feet 10 inches
   length                  12.71 meters        41 feet 8 inches
   height                  4.03 meters         13 feet 2 inches
   max speed               785 KPH             490 MPH / 425 KT
   service ceiling         13,100 meters       43,000 feet
   range                   2,185 kilometers    1,355 MI / 1,180 NMI
   _____________________   _________________   _______________________

Flight controls are of conventional arrangement -- one-piece flaps, ailerons, rudder, elevators, with manual actuation, except for electrically-driven flaps. There are trim tabs for all three axes of flight. Engine bleed air is used for wing de-icing, though an electromechanical scheme is used for tail de-icing; the engine inlets are de-iced as well, presumably by engine bleed air. All landing gear assemblies have single wheels, with the main gear pivoting from the inner wings to retract towards the fuselage, the nose gear retracting forward. Retraction is by hydraulic actuation, with the nose wheel featuring electronic steering.

Honda HondaJets

The cockpit has dual controls, and features a Garmin 3000 avionics suite, with three large color flat-panel displays across the dash, and two small touchscreen controllers on the center control station. There is a optional side-facing passenger seat on the right, just behind the cockpit, with four seats in a club configuration in the middle of the aircraft. There is a lavatory behind the passenger compartment, and a baggage compartment behind that. The passenger door is on the front left side of the fuselage, being in a hinge-down configuration with integral airstair; there is an emergency exit above the left wing. Of course, the Hondajet is pressurized and climate-conditioned. Full certification took place in 2015, with initial customer deliveries that December.



* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* This document is heavily reliant on various volumes of JANE'S ALL THE WORLD'S AIRCRAFT, manufacturer's websites, and video reports on the various aircraft.

Mitsubishi MU-2S of JASDF

* Revision history:

   v1.0.0 / 01 apr 15
   v1.0.1 / 01 mar 17 / Review, update, & polish.