Hoffar Aero Engines

Hoffar Aero Engines was a manufacturer of aircraft engines and other components in British Columbia between 1923 and 1948. It exists today as Hoffar Aero, the BC division of BAE Systems.

History
Vancouver-based Hoffar-Beeching Shipyards got into the aero engine business in 1923, quickly establishing a division, Hoffar Aero Engines (HAE), to specialise in the manufacture and development of aircraft engines. Its original plant was located at Dollarton, North Vancouver, alongside Hoffar Marine's facilities; in 1943, an enormous new plant was erected in Prince George, well away from feared Japanese attack.

HAE was bought in 1948 by the British Armstrong Siddeley, and continued to produce complete aero engines until 1950. Preparations for production of the Armstrong Siddeley Sapphire jet engine were begun in 1949 pending an order by the Royal BC Air Force, but after the order failed to materialise, the massive plant in Prince George was down to producing dwindling numbers of Heron engines and replacement parts for them. Not willing to give up on its investment so soon, Armstrong Siddeley decided to set up production of the Armstrong Siddeley Whitley 18 automobile. To this end, it formed the Hoffar Auto division, which took over the vast Prince George facility. Hoffar Aero returned to the Dollarton plant, to continue as a parts supplier for the parent - Armstrong Siddeley until 1961, then Bristol Siddeley until 1966, then Rolls-Royce until 1971, then the British Aircraft Corporation until 1977, then British Aerospace until 1999; since then, it is exists as the Hoffar Division of BAE Systems.

Products
The following descriptions of HAE's engines is written in roughly chronological order.

Harpy
Introduced in 1923, the HV-8A Harpy was HAE's first engine, a derivative of Hoffar's HV-8 Haro marine engine for use on aeroplanes; the HV-8 Haro was in turn based on Liberty L-12 components. It was an upright, water-cooled V-8.

Hobby and Hawkmoth series
Based on the HV-8A, the HIV-8A Hobby of 1924 was an air-cooled inverted V-8 using cylinders derived from Allison's reduced-bore 1A-1650, which was an air-cooled inverted V-12. It spawned two derivatives, the 4-cylinder HIL-4A Hawkmoth-4 of 1925, and the 6-cylinder HIL-6A Hawkmoth-6 of 1926; both of these were upright inline engines.

Hawk
In 1926, HAE introduced a new air-cooled, 60° inverted V-8 engine called the HIV-8A-2 Hawk; although an original design, it nevertheless used a number of HV-8 components. It was available in two versions, with or without supercharger.

A derivative of the V-8 Hawk, designated HIV-4 and nicknamed "Half Hawk", was developed in 1929. This was, as the nickname suggests, essentially half of a Hawk - an air-cooled inverted V-4. The intention was to make a smoother-running light engine to replace the HO-4 Honeybee, but ultimately the project was cancelled for cost reasons.

Honeybee and Hoverfly series
Also in 1926, the Honeybee series of light engines was introduced in two versions, the HO-2 Honeybee a 2-cylinder, the HO-4 Honeybee a 4-cylinder. They were horizontally opposed and used the cylinders from the HIV-8A Hobby. In the following year, an upright single-cylinder variant called the HU-1 Hoverfly was introduced as well.

Unnamed HIL series
1927 saw a project to develop replacements for the Hawkmoth series; like the Hawkmoth, this unnamed project was an air-cooled upright inline engine in two versions - the HIL-4A-2 having four cylinders, the HIL-6A-2 having six cylinders. Neither entered production, as the project was cancelled due to indifferent market prospects.

Harrier
In 1928, HAE introduced the HIV-12A Harrier inverted V-12. This was a "stretched" version of the Hawk, essentially adding four more cylinders onto the Hawk design; in other respects, it was very much the same as the earlier engine.

The following year, a larger, more powerful experimental version, the HIV-12A-2, was built, but this failed to get past bench testing.

HB Dragon series
The Dragon series of engines was a joint project begun in 1931 with Bolas Aircraft, initially designed by Harold Bolas specifically to power his Dragonfly STOL aircraft. Several variants were built. First was the HB-4A Dragon IV in 1932, a 120 hp air-cooled inverted inline 4-cylinder with direct drive, followed in 1933 by the HB-4A Dragon IV-G, which was a geared version of the Dragon IV that was built as a prototype only. A version of the IV-G optimised for military inverted flying was built in 1934, called HB-4A Dragon IV-M. Also in that year, an 8-cylinder, designated HB-8A Dragon VIII version was considered, but this project was not pursued beyond the paper stage. 1935 saw the arrival of the HB-6A Dragon VI, a 6-cylinder evolution of the Dragon IV, and this was followed by the HB-6A Dragon VI-G and the HB-6A Dragon VI-M - geared and military versions respectively.

HLR series
The relationship between Hoffar and Société Lorraine-Dietrich began several years after the end of the First World War, when the French company was looking to dispose of stocks of engines rendered superfluous by the end of the war lest they be declared war profiteers. Between 1917 and 1922, Lorraine-Dietrich at its Argenteuil works had built 1200 Type 12D water-cooled 60° V-12 engines producing 370 hp; in 1920, Hoffar's Marine Engines division bought several hundred of these to adapt for use in yachts and rum-runner boats. This led to a licencing deal with Société Lorraine for the North American rights to their Mizar and Algol radial engines for light aircraft.

In 1934 three prototypes with 105 mm × 125 mm (4.13×4.92 in) bore and stroke were assembled based on the Lorraine designs. These were built, but not tested, as they were not intended for production: the HLR-3Ab was a 60 hp 3-cylinder, the HLR-6Ab was a 130 hp 6-cylinder, and the HLR-9Aa was 185 hp 9-cylinder engine - in essence, a scaled-down version of the Algol. Meanwhile, the designs of the Mizar and Algol were converted from metric to Imperial measures for production in BC, becoming the HLR-7A Mizar (7-cylinder) and the HLR-9A Algol (9-cylinder). HAE's version of the Algol differed from the original, in that it was air-cooled, where the Lorraine version was water-cooled.

HB Bombus series
The HB Bombus series was another joint project with Bolas, begun in 1938 with the HB-4 Bombus IV, a direct-drive, 110 hp inverted V-4 for light aircraft using the cylinders of the HB Dragon VI; a geared version of this, the HB-4 Bombus IV-G, was proposed, but work on this was cancelled in September 1939. Earlier in 1939, a 6-cylinder version was produced in civilian and military variants (HB-6 Bombus VI and HB-6 Bombus VI-M respectively), along with an 8-cylinder derivative, the HB-8 Bombus VIII. In early 1940, a military version of the Bombus VIII was put into production, designated HB-8 Bombus 8M.

Petrel series
In 1934, HAE bought the North American rights to Lorraine-Dietrich's latest engine, the 12H Pétrel, a water-cooled, fuel-injected upright V-12 with an aluminium crackcase and separate cylinder blocks. Several prototypes were assembled in 1935 using parts from Lorraine, designated HLV-12X Petrel, producing 600 hp, whilst the design was converted to Imperial measures. This resulted in the HLV-12A Petrel, which produced 700 hp and was identical to the original design in its 5.71"×5.71" bore and stroke and 6:1 compression ratio; however, unlike the 12H, the HLV-12A was glycol-cooled, and with a dry weight of 1090 lbs, was heavier than the original. Unsatisfied with the power output, HAE revised the design, replacing the direct fuel injection of the Lorraine design with a more conventional updraught carburettor. The result was the HLV-12A-2 Petrel, which weighed only 10 lbs more but produced from 750 hp up to 890 hp on 80 octane fuel, and went on to become a landmark in BC aviation history after being selected to power the second generation of Supermarine BC's Skemcis fighters for the RBCAF and the first generation of the Sea Skemcis for the navy.

Two derivatives were projected in 1937, the HLV-12A-2a with an SU carburettor in place of the Bendix unit in the 12A-2, and the HLV-12A-3, a moteur-canon derivative with a 20 mm cannon firing through the propeller hub. Neither of these projects were built.

Tern series
Convinced that the Petrel had reached the peak of its power output, HAE set out to design a successor. Introduced in 1939, the HV-12A-4 Tern was a slightly enlarged version of the Petrel, retaining its aluminium block construction with screw-in steel cylinder inserts. However, the Tern's bore and stroke were increased to 6"×6", which placed its piston capacity between that of the Rolls-Royce Merlin and later Griffon engines. It also retained the Petrel's 6:1 compression ratio and its updraught carburettor; its dry weight was 1150 lbs, and it produced 990 hp. Coincident with the development of this was a variant designated HV-12A-4A Tern which foresaw the replacement of the carburettor with the direct fuel injection of the original Petrel design, but this did not proceed past the paper stage. The HV-12A-4 could be considered a pre-production variant, as only a dozen were built.

The first serial version was the HV-12A-4B Tern, entering production in 1940 in time to be used on the latest variant of the Skemcis, the F Mk. VII - the first variant to be truly mass produced, and which gained distinction both as the only BC-designed aircraft to take part in the Battle of Britain, and as the first BC-designed combat aircraft to be exported to a foreign air force (for the Soviet Air Force, after the German invasion of the USSR in 1941). In most respects the 4B was identical to the 4, using the same Bendix carburettor and having the same dry weight of 1150 lbs, but the compression ratio was increased to 6.9:1, resulting in a more powerful engine: the 4B produced 1000 horsepower running on 86 octane fuel; if 90 octane fuel was used, the increase in output was significant - 1090 hp. Its performance in the Battle of Britain and, later, on the Soviet front, was considered a great success. Early in 1941 the HV-12A-4B-1 Tern was introduced, with minor variations to the carburettor resulting in a slight increase in performance, producing 1100 hp, though with an increase in weight to 1175 lbs; it was this version that powered the first batch of Skemcis F Mk. VII B fighters delivered to the USSR. A few months later the definitive version of the 4B arrived - the HV-12A-4B-2 Tern, which featured some revisions to the electrical system that further improved reliability but did not affect performance nor weight.

In 1941, HAE commissioned Hoffar Marine's diesel engine supplier, California-based Atlas-Imperial, to rework the Lorraine fuel injection system of the original Petrel. This resulted in the semi-experimental HV-12A-4C Tern-FI of 1942, which, though otherwise identical to the 4B-2, produced 1150 hp instead of the 1100 hp of the 4B-2. Produced in a short run of 100 units, they were fitted to the latest version of the Skemcis series, the F Mk. VIII, where they proved themselves, meeting all expectations. Meanwhile, further modifications were made to the 4B-2 in 1942 to create the HV-12A-4D Tern, featuring a much improved supercharger that boosted the power output by 100 hp to 1200 hp.

The success of the 4C led to the reintroduction of fuel injection to full production engines in the form of the HV-12A-4E Tern of 1943. Weighing in at 1220 lbs dry, the 4E produced 1280 hp. Within a few months, though, a strengthened, slightly heavier (1230 lbs dry) version, the HV-12A-4E-1 Tern was introduced, bringing about a significant boost in power output. Running on 100 octane fuel, the 4E-1 produced 1325 hp; even on standard 87 octane avgas, its output was still 1280 hp. Because the supply of fuel injectors was not yet up to full capacity, through 1943 the HV-12A-4F Tern was also produced, using the Bendix-Stromberg PD updraught carburettor; this weighed 1210 lbs dry and produced 1280 hp. By 1944, Atlas-Imperial had increased production of fuel injectors enough to meed demand, allowing for full-scale manufacture or the fuel-injected engines, and no further engines with carburettors were produced. In the spring of 1944, manufacture of the HV-12A-4G Tern began, which weighed 1260 lbs and produced 1325 hp, but by the autumn production shifted to the HV-12A-4K Tern. This, the ultimate version of the Tern series, introduced a new two-speed, two-stage supercharger which significantly improved performance at altitude. The heaviest but most powerful of the Terns, it weighed 1320 lbs dry and had an output of 1400 hp.

Heron series
Hoffar Aero Engines received an intact Daimler-Benz DB 605 retrieved from a Luftwaffe Messerschmitt Bf.109 that belly-landed in England in 1942. Impressed with the design, a team of Hoffar engineers led by Harold Bolas began working on a derivative that was originally envisaged as powering a mid-engined pursuit design proposed by Fairey BC. While the Fairey scheme never materialised, HAE continued working on the new engine design. At the end of 1943 a few test engines using salvaged DB 605 components were tested. Designated HV-12A-5 Heron, these test engines produced 1690 hp. From there, the design was modified and improved, slowly moving further from its Daimler-Benz roots until, in late March 1944, another trials type was built. Weighing 1600 pounds dry, the HV-12A-5-1 had steel cylinder blocks and matched the 1690 hp output of the A-5. One was fitted to a modified Skemcis F Mk. XI for flight testing. By August of 1944 a pre-production type, the HV-12A-5-2 was ready. Thanks to aluminium cylinder blocks, the weight of the A-5-2 remained 1600 pounds, but the power output surged to 1775 hp. Twenty of the A-5-2 were built for use in limited production versions of a new Skemcis variant. To test the engine in operation, ten examples of both the Skemcis F Mk. XIIA and the Sea Skemcis F Mk. VIA were built, and were extensively tested in BC in simulated combat conditions.

Whilst the A-5-2 powered variants were being tested, HAE perfected the finalised, regular production version of the Heron. The HV-12A-5-3 took the previous version and fitted a two-stage supercharger, which resulted in an increase of 200 hp - to 1975 hp - for only a ninety pound increase in dry weight to 1690 lbs. Entering production in 1945, it was very soon replaced by the further-improved HV-12A-5-4, which replaced the single-speed, two-stage supercharger with a two-speed, two-stage variant that, for a weight increase of only thirty pounds, boosted output by 115 hp, to 2090. This, the pinnacle of British Columbian piston engine design, remained in production until 1950.