Supermarine Aircraft Spitfire

Supermarine Aircraft

Company type	Private company
Industry	Aerospace
Founded	1995
Founder	Mike O'Sullivan, John McCarron
Headquarters	Clyde, Texas , United States
Area served	United States, Australia, United Kingdom, International
Products	Kit-built aircraft (Spitfire replicas)
Website	www.supermarineaircraft.com

This article is about the homebuilt replica. For the original World War II fighter, see Supermarine Spitfire.

The Supermarine Aircraft Spitfire is a kit-built aircraft from the United States, manufactured by Supermarine Aircraft. It serves as a scaled replica of the iconic British World War II fighter, the Supermarine Spitfire. Initially, this replica was constructed at 75% of the original’s size. Later versions expanded the fuselage dimensions and incorporated an additional seat.

Design and development

Mike O'Sullivan, an Australian aviator and engineer, fulfilled his ambition to own a Supermarine Spitfire by constructing a personal replica in 1991. This effort led to the creation of a prototype in 1994 powered by a 75 horsepower (56 kW) Rotax engine. In 1995, he partnered with John McCarron to establish the Supermarine Aircraft company, focusing on producing all-Australian kits for homebuilders. Although the aircraft features a constant-speed, four-blade propeller, this component was sourced from a specialist manufacturer based in New Zealand. Despite sharing its name, Supermarine Aircraft has no direct connection to the original British Supermarine firm; however, permission to use the Supermarine brand was granted by its current owners.

The inaugural production variant was designated the Spitfire Mk 25, replicating the original Supermarine Spitfire at 75% scale. Its stressed-skin airframe employs 2024 aluminium alloy sheets along with formers and longerons, complemented by some moulded components made from Glass-reinforced plastic, such as fairings and air scoops. The design incorporates electrically actuated retractable landing gear with differential braking on the main wheels and includes landing flaps.

Subsequent models include the Spitfire Mk 26, which retained the Mk 25 wing design but enlarged the fuselage to 80% scale to accommodate a tandem passenger seat behind the pilot. The Mk 26B further increased this to 90% scale. Notably, these kits maintain a power-to-weight ratio comparable to that of the original aircraft.

In 2001, the Australian Ultralight Federation evaluated the aircraft and confirmed its compliance with Australian regulations governing kit-built planes. By 2004, Supermarine had begun marketing their kit for the United States market. The British Light Aircraft Association has also granted approval for this model.

Currently, Supermarine Aircraft operates out of Cisco Airport in Texas, with its headquarters located nearby in Clyde, Texas.

Powerplant

The initial Mk 25 prototype was equipped with a Rotax engine before evolving through several more robust Jabiru variants. Early production units utilized Australian-made eight-cylinder Jabiru engines delivering approximately 200 hp (149 kW). Later on, the manufacturer introduced a V6 Isuzu engine conversion, offering outputs of 260 or 320 hp (194 or 239 kW) with the addition of a supercharger. Additionally, a V8 automotive engine conversion sourced from General Motors was developed, capable of producing around 430 hp (321 kW).

Initial iterations of the Spitfire Mk 26 were powered by an eight-cylinder 180 hp (134 kW) Jabiru 5100 horizontally opposed aero engine, though early configurations encountered cooling challenges. Presently, the company provides a V6 engine option. The naturally aspirated variant generates roughly 226 hp (169 kW), while the supercharged model can reach up to 310 hp (231 kW).

Since propeller maximum rotational speed (approximately 2800 rpm depending on size) is about half the peak torque and power rpm of typical automotive engines (around 5500 rpm), these engines require a reduction drive unit. These units typically consume about 20% of the engine’s power output, meaning the normally aspirated Isuzu version delivers comparable maximum power to the Jabiru 5100. Recent advancements in the Jabiru engine line by Rotec have introduced water-cooled cylinder heads for the 5100 model. This innovation has resolved previous overheating issues and enabled redesigning the Mk26’s nose cowling to eliminate the air intake, significantly reducing frontal area and restoring the streamlined silhouette reminiscent of the original Spitfire design.

Variants

File:F-PFAF Super Marine Aircraft Spitfire Mk.26 (9705875977).jpg

Side view of a Spitfire Mk 26, Sywell Airfield, 2013

Mk 25

This single-seat model, no longer in production, was built at 75% scale. It represented an authentic 'three-quarter' scale rendition of the World War Two Spitfire Mk 5.

Mk 26

A two-seat variant constructed at '80% scale'. Production ceased by 2011 to make way for a '90%' scale version. The '80% scale' designation applies solely to the fuselage length, which was extended to 80% of the original Spitfire Mk 5 length. The wing remained unchanged from the 75% scale version, resulting in wingspan and undercarriage height identical to that smaller model.

Mk 26B

An enhanced version of the Mk 26 featuring optional dual controls and built at '90% scale'. This measurement pertains only to the fuselage length, which was increased to approximately 89.5% of the original Spitfire Mk 5 length and broadened around the cockpit area. The wing retained its dimensions from the 75% scale aircraft, maintaining identical wingspan and undercarriage height as that earlier model.

Construction

Building the Spitfire demands proficiency in metalworking along with specialized tools, and extensively utilizes aviation-grade pull rivets, commonly known as pop rivets. Although pre-assembled kits are available, the assembly process still requires approximately 1,200 man-hours of labor to complete.

Operational history

To date, over 92 Spitfires have been sold internationally.

Fatal accidents and controversies

Following a fatal incident involving a Mk 26 at Gympie, Australia, in October 2010, the coroner's report issued on December 29, 2014, revealed significant findings. Michael O’Sullivan, CEO of Supermarine Pty Ltd, acknowledged that the aircraft’s test flight duration was only 20 hours rather than the declared 37.5 hours. He further admitted to deliberately falsifying documentation to register the aircraft with RA-Aus (Recreational Aviation Australia) instead of undergoing the stricter CASA (Civil Aviation Safety Authority) certification. Additionally, he confessed to substantially underreporting the aircraft's weight by roughly 200 kg—approximately half of its stated empty weight of 401 kg.

In 2013, an 80% scale Mk 26 Spitfire crashed near Adelaide, Australia. The sole occupant, who was piloting the aircraft, died due to the accident. Investigations identified pilot error as the primary cause; however, the Australian Transport Safety Bureau (ATSB) highlighted that the aircraft was susceptible to aerodynamic stall without clear warning signs and lacked a stall warning device, thereby increasing the risk of an unintentional stall.

In August 2023, a Mk 26B Spitfire at 90% scale crashed close to Enstone, Oxfordshire in the United Kingdom during a test flight aimed at securing a Permit to Fly. The test involved evaluating leading edge stall strips as part of an authorized program. The pilot suffered fatal injuries when control was lost and the aircraft impacted the ground. Post-accident examination found that the fin and rudder were misaligned. While this misalignment may have contributed to wing drop during stall conditions, it would not have prevented recovery from stall or subsequent spin or spiral dive. Investigators could not rule out pilot incapacitation or control limitations as potential factors.

A second Mk 26B Spitfire crashed at Enstone Airfield on July 24, 2024. The pilot was killed after the aircraft rolled left during takeoff. As of late July 2025, this crash remains under active investigation.

Specifications (Mk 26B)

File:SpitfireMk26b.jpg

Instrument panel of the Mk 26B

External links

• Supermarine Aircraft official website.
• Spitfire MK26 at Pilotfriend.com.
• Photograph of Spitfire MK26 on pbase.com.
• Supermarine Spitfire Mk 26b at retrothing.com.