In 1912 the His Majesty Balloon Factory was transformed into the Royal Aircraft Factory (not to be confused with the RAF, Royal Air Force).

- It was located in South Farnborough, Hampshire.

-Around 1913 it presents the 1A and 1B models, both air-cooled, 8-cylinder V-engines that owed much to Renault solutions.

“RAF-1A”

-They had a similar valve system configuration, and the propeller was mounted on a camshaft extension, spinning half the crankshaft rotations, but while the Renault gave 80 HP, the RAF-1A and 1B gave 92 hp and 115 hp respectively.

“RAF-1A, rear view”

-From the Royal Aircraft Factory is the RAF 1A engine exhibited at the MAE and suitably restored.

“RAF-1A engine at the MAE”

“The same RAF-1A from behind”

-They used aluminum pistons, instead of cast steel, and a different lubrication system. They rotated at higher revolutions: The  -1A at 1,600 rpm, and the -1B at 1,800 rpm.

-The 1A had a bore of 3.94 inch and 5.51 inch of stroke. Both the -1A and -1B were air-cooled.

"And in left side view"

“RAF-1B”

-The RAF-1C, from 1915, was made with aluminum cylinders.

-The RAF-1D was like the -1A with steel cylinders and aluminum cylinder heads. Later this method would be used with the -4A. The RAF-1D engine gave 150 HP at 2,000 rpm.

-The RAF-1E was similar to the -1D but with RAF-4E cylinders.

“RAF-3A”

-The 3 and 3A had 12 liquid-cooled cylinders in V and delivered between 200 HP the former and 244 HP the latter at 1,800 rpm both, rising to 266 HP increasing the compression to 5.5: 1.

-With 4.5 inch bore and 5.5 inch stroke, the 3A weighed about 780 lbs.

-The water-cooled RAF-3A was made under license by Napier, as we see in the below engine exhibited at the Polish Museum in Krakow.

“Napier-RAF-3A”

-The RAF-4A culminated the series of air-cooled V-engines, it was mass produced due to the UK being in the middle of WWI.

“RAF-4A”

-This engine had the V at 60°, a compression ratio of 4.2: 1, two carburetors and a single spark plug per cylinder.

-Two BTH magnetos that fed 6 cylinders each. Powers were between 140 and 160 HP, the latter at 1,800 rpm.

-It was mounted on BE12, BE12A, FE4 and some RE7 and RE8 aircraft. The most important engine was the 150 HP RAF-4A.

“RAF-4A”

It was followed by the RAF-4D with 100 mm bore and the RAF-4E with 105 mm bore, giving 200 hp the former and 240 HP the latter, both at 2,000 rpm.

-The compression ratio went up to 4.7: 1. Both engines are from 1916.

“RAF-4D”

-The RAF-5 was a RAF-4D version for pusher installation instead of puller.

-It had a fan to force cooling.

-It gave 150 HP but the fan absorbed about 10 HP of the power.

-The B version of the RAF-5 gave 170 HP, which was to be installed in pusher position as well.

-In the following illustration we see them installed on an R.A. Factory FE4 model aircraft.

“RAF-5”

-The RAF-7 was a RAF-3A with high compression -relatively speaking-, and had valves with longer strokes, etc. It gave 300 HP.

-With the RAF-8, from 1916, the production of RAF engines ends.

-By government resolution, it stops manufacturing and becomes the Royal Aircraft Establishment, analyzing material and its approval.

“RAF-8”

-The 14-cylinder RAF-8 production continued. With relevant personnel from its development it passed to Siddeley-Deasy Motor Co. where it would end up being the Armstrong Siddeley Jaguar engine. (See).

-Originally, the Jaguar was the RAF-8, but here we noticed a great evolution, with its 14 cylinders it gave 400 HP at 1,700 rpm.

-It is the Mk-IVC model.

-The RAF-21 was an improved ABC Dragonfly to give 350 HP.

-The RAF-22 was the ABC Wasp but with a new cylinder design to increase engine power from 180 to 190 HP.

“Armstrong Siddeley, Jaguar -ex RAF-8”

From Appendix 7: Below we state a more complete list of the engines built at the Royal Aircraft Factory.

-From 1913 to 1917:
-Model 1, 90 HP, prototype.
-Model 1a, 90 HP, production.
-Model 1b, did not go into production.
-Model 1c, 105 HP experimental high compression.

-From 1913:
-Model 2, 120 HP, experimental,

-From 1914 to 1915:
-Model 3, 200 HP, prototype.
-Model 3a, 200 HP, production.
-Model 3T, experimental.

-From 1914 to 1916:
-Model 4, 140 HP based on the RAF-1.
-Model 4a, 140 HP, production.
-Model 4b, 170 HP based on 1b.
-Model 4c, 170 HP and with aluminum cylinders.
-Model 4d, 200 HP supercharged.
-Model 4e, 200 HP supercharged.
-Model 4f, 1200 HP, only the crankcase was made.

-From 1915:
-Model 5, 140 HP "Pusher" type 4 with fan.
-Model 5a, 140 HP production.
-Model 5b, 170 HP, “Pusher”, 4b version.
-Model 5c, 170 HP with aluminum cylinders. it did not go into production.
-Model 5d, 170 HP with overhead valves. It did not go into production.

-From 1915:
-Model 6, air-cooled, 90° V8. 90 HP pusher from 1st.

-From 1917:
-Model 7, water-cooled V12, at 60°. High compression of Mod. 3.

-From 1916:
-Model 8, with 14 double row radial cylinders, cooled by air. Base for the Armstrong Siddeley Jaguar.

-From 1916:
-Model 9, Single Cylinder with Slide Valve. Experimental.

-Of unknown date:
-Model 10, 12 cylinders in W, water-cooled, Lion prototype.

-Of unknown date:
-Model 11, 3 cyl. air-cooled model 8.

-From 1917:
-Model 12T, Double Acting Opposed Cylinders, 2-stroke. Experimental.

-From 1917:
-Model 13T, a single cylinder, air-cooled and experimental.

-Of unknown date:
-Model 14, 16 cylinders in X, air-cooled.

-From 1917:
-Model 15. Air-cooled V12 at 60°.

-From 1918:
-Model 16, a V12 at 60°, air-cooled.

-From 1918:
-Model 17T, air-cooled cylinder. Tests.

-From 1918:
-Model 18T, sliding sleeve cylinder, air-cooled and test.

-From 1918:
-Model 19, air-cooled test cylinder.

-From 1918:
-Model 20, water-cooled test cylinder.

-From 1918:
-Model 21T,
-Model 21TD, base design for the ABC Dragonfly.

-Of unknown date:
-Model 22TW, base design of the radial ABC Wasp.
-Model 22W, redesign of the 7-cylinder radial. ABC Wasp.

-Of unknown date:
-Model 23T, two-valve Bristol Jupiter design.
-Model 24T, Jupiter redesign with four valves.
-Model 25T, base Armstrong Siddeley Leopard design.
-Model 26T, Experimental 2-stroke, water-cooled.
-Model 27T, Air-cooled 2-stroke, Experimental.
-Model UT, Carter for cylinders, experimental.

From Appendix 9: RAF is the Royal Aircarft Factory. They designed and manufactured their own engines. But some models like the RAF-3A was also made by Napier.

“The RAF-Napier Model 3A”

-This is the Royal Aircraft Factory. It designed new engines and studied parts like cylinders. After the year 1918 the authorities decided that this company should dedicate itself to research and homologation.

-Its works are ordered by ordinal number (RAF-1, RAF-2 ...) and with sub-models (RAF-1A ....). We now have a more up-to-date list of all of them:

-RAF-1 prototype and in V8 form. Air-cooled.
-RAF-1A, production (production years 1913-1917)
-RAF-1B, did not go into production.
-RAF-1C
-RAF-1T, experimental.
-RAF-2 (year 1913) of 120 HP, 9-cylinder rotary radial, experimental.
-RAF-3, from the year 1914/1915, with 12 cylinders in V giving 200 HP, prototype. Air-cooled.
-RAF-3A, production of 200 engines
-RAF-3T, experimental
-RAF-4. Years 1914/1916. V-12 of which the prototype gave 140 hp.
-RAF-4A, production. Air-cooled.
-RAF-4B. Reaches 170 HP.
-RAF-4C, 170 HP with aluminum cylinders.
-RAF-4D, without s / c.
-RAF-4E, without s / c
-RAF-4T, only evolution of the crankcase.
-RAF-5, (Year 1915). V-12 prototype. Air-cooled.
-RAF-5A, 140 HP, production.
-RAF-5B, 170 HP.
-RAF-5C, 170 with aluminum cylinders.
-RAF-5D, 170 HP with OHV. Not built.
-RAF-6, (1915) V8 "pusher" of the RAF-1A. Air-cooled.
-RAF-7, V-12, (1917) water-cooled. High compression. Ref. With 3.
-RAF-8, from the year 1916 is the base engine for the Armstrong Siddeley Jaguar with 14 radial cylinders.
-RAF-9, from the year 1916 is only 1 experimental cylinder “Sleeve-valve”.
-RAF-10, 12-cylinder W engine, was the inspiration for the Napier Lion.
-RAF-11, 3-cylinder RAF-8, air-cooled.
-RAF-12, from the year 1917. Prototype -12T with double-act and 2-stroke opposed cylinders.
-RAF-13, from the year 1917, An air-cooled single cylinder, experimental.
-RAF-14 of 16 cylinders in "X", experimental.
-RAF-15, from 1917, is an air-cooled V-12.
-RAF-16, from the year 1918, V-12, a test cylinder.
-RAF-17, from 1918, and 18-T, air-cooled. A test cylinder.
-RAF-18, (1918), the 18T is an air-cooled sleeve-valve cylinder.
-RAF-19, from the year 1918 is another air-cooled cylinder.
-RAF-20, 1918, with a water-cooled cylinder.
-RAF-21, (1918). the -21TT and -21TD was the design of the ABC “Dragonfly”.
-RAF-22, the -22TW was the design of the ABC "Wasp", and the 7-cylinder -22WW was a redesign of the same "Wasp".
-RAF-23. The -23T was the 2-valve cylinder design of the Bristol Jupiter.
-RAF-24T, the new cylinder design of the Bristol Jupiter with 4 valves.
-RAF-25. the -25T was the cylinder design of the Bristol Leopard.
-RAF-26. The -26T was a water-cooled experimental 2-stroke cylinder.
-RAF-27, the -27T is the same air-cooled 2-stroke cylinder.
-RAF-UT, from a917, experimental engine.