BEAUFIGHTER HISTORY & SPECS

Design and development

The idea of a fighter development of the Beaufort was suggested to the by Bristol. The suggestion coincided with the delays in the development and production of the Westland Whirlwind cannon-armed twin-engine fighter. By converting an existing design, the "Beaufort Cannon Fighter" could be expected to be developed and produced far more quickly than starting a completely fresh design. Accordingly, the Air Ministry produced Specification F.11/37 written around Bristol's suggestion for an "interim" aircraft pending proper introduction of the Whirlwind. Bristol started building a prototype by taking a part-built Beaufort out of the production line. The prototype first flew on 17 July 1939, a little more than eight months after the design had started, possibly due to the use of much of the Beaufort's design and parts. A production contract for 300 machines had already been placed two weeks before the prototype flew, as F.17/39.

By fighter standards, the Beaufighter Mk.I was rather heavy and slow. It had an all-up weight of 16,000 lb (7,000 kg) and a maximum speed of only 335 mph (540 km/h) at 16,800 ft (5,000 m). Nevertheless this was all that was available at the time, as further production of the otherwise excellent Westland Whirlwind had already been stopped due to problems with production of its Rolls-Royce Peregrine engines.

The Beaufighter found itself coming off the production line at almost exactly the same time as the first British Airborne Intercept (AI) sets. With the four 20 mm cannon mounted in the lower , the nose could accommodate the radar antennas, and the general roominess of the fuselage enabled the AI equipment to be fitted easily. Even loaded to 20,000 lb (9,100 kg) the plane was fast enough to catch German bombers. By early 1941, it was an effective counter to night raids. The various early models of the Beaufighter soon commenced service overseas, where its ruggedness and reliability soon made the aircraft popular with crews.

A night-fighter Mk VIF was supplied to squadrons in March 1942, equipped with AI Mark VIII radar. As the faster took over in the role in mid to late 1942, the heavier Beaufighters made valuable contributions in other areas such as anti-shipping, ground attack and long-range interdiction in every major theatre of operations.

In the Mediterranean, the USAAF's 414th, 415th, 416th and 417th Night Fighter Squadrons received 100 Beaufighters in the summer of 1943, achieving their first victory in July 1943. Through the summer the squadrons conducted both daytime convoy escort and ground-attack operations, but primarily flew defensive interception missions at night. Although the Northrop P-61 Black Widow fighter began to arrive in December 1944, USAAF Beaufighters continued to fly night operations in and France until late in the war.

By the autumn of 1943, the Mosquito was available in enough numbers to replace the Beaufighter as the primary night fighter of the RAF. By the end of the war some 70 pilots serving with RAF units had become aces while flying Beaufighters.

Coastal Command

1941 saw the development of the Beaufighter Mk.IC long-range . This new variant entered service in May 1941 with a detachment from No. 252 Squadron operating from . The aircraft proved so effective in the Mediterranean against shipping, aircraft and ground targets that Coastal Command became the major user of the Beaufighter, replacing the now obsolete Beaufort and Blenheim.

Coastal Command began to take delivery of the up-rated Mk.VIC in mid 1942. By the end of 1942 Mk VICs were being equipped with torpedo-carrying gear, enabling them to carry the British 18 in (457 mm) or the US 22.5 in (572 mm) torpedo externally. The first successful torpedo attacks by Beaufighters came in April 1943, with No. 254 Squadron sinking two merchant ships off .

The North Coates Strike of Coastal Command, based at RAF North Coates on the Lincolnshire coast, developed tactics which combined large formations of Beaufighters using cannon and to suppress flak while the Torbeaus attacked at low level with torpedos. These tactics were put into practice in mid 1943, and in a 10-month period, 29,762 tons (27,000 tonnes) of shipping were sunk. Tactics were further adapted when shipping was moved from port during the night. North Coates Strike Wing operated as the largest anti- shipping force of the Second World War, and accounted for over 150,000 tons (136,100 tonnes) of shipping and 117 vessels for a loss of 120 Beaufighters and 241 aircrew killed or missing. This was half the total tonnage sunk by all strike wings between 1942-45.

The Beaufighter arrived at squadrons in Asia and the Pacific in mid-1942. It has often been said - although it was originally a piece of RAF whimsy quickly taken up by a British journalist - that Japanese soldiers referred to the Beaufighter as "whispering death", supposedly because attacking aircraft often were not heard (or seen) until too late. The Beaufighter's Hercules engines used s which lacked the noisy valve gear common to poppet valve engines. This was most apparent in a reduced noise level at the front of the engine.

Variants

Beaufighter Mk IF: Two-seat night fighter variant.

Beaufighter Mk IC: The "C" stood for Coastal Command variant; many were modified to carry bombs.

Beaufighter Mk II: However well the Beaufighter performed, the bomber program by late 1941 had a higher priority for the Hercules engine and the Rolls Royce Merlin XX- powered Mk II was the result.

Beaufighter Mk IIF: Production night fighter variant. Beaufighter Mk III/IV: The Mark III and Mark IV were to be Hercules and Merlin powered Beaufighters with a new slimmer fuselage carrying an armament of six cannon and six machine guns which would give performance improvements. The necessary costs of making the changes to the production line led to the curtailing of the Marks.

Beaufighter Mk V: The Vs had a Boulton Paul turret with four 0.303 in (7.7 mm) machine guns mounted aft of the cockpit supplanting one pair of cannon and the wing-mounted machine guns. Only two Mk Vs were built.

Beaufighter Mk VI: The Hercules returned with the next major version in 1942, the Mk VI, which was eventually built to over 1,000 examples.

Beaufighter Mk VIC: Torpedo-carrying variant dubbed the "Torbeau".

Beaufighter Mk VIF: This variant was equipped with AI Mark VIII radar.

Beaufighter Mk VI (ITF): Interim torpedo fighter version.

Beaufighter TF Mk X: Two-seat torpedo . The last major version (2,231 built) was the Mk X, among the finest torpedo and strike aircraft of its day.

Beaufighter Mk XIC: Built without torpedo gear for Coastal Command use.

Beaufighter Mk 21: The Australian-made DAP Beaufighter. Changes included Hercules CVII engines, a dihedral tailplane, four 20 mm cannon in the nose, four Browning .50 in (12.7 mm) in the wings and the capacity to carry eight 5 in (130 mm) High-Velocity Aircraft Rockets (HVAR), two 250 lb (110 kg) bombs, two 500 lb (230 kg) bombs and one Mk 13 torpedo.

Beaufighter TT Mk 10: After the war, many RAF Beaufighters were converted into target tug aircraft.

BEAUFIGHTER ENGINE TESTS

SUMMARY

...... Level speed and climb performance has been measured on Beaufighter VI X.7542. During the course of the tests, the engines were re-rated. At the later rating the following performance figures were obtained at a weight of 19,750 lb.

2,325 feet/minute at 4,600 Maximum rate of climb feet. Time to reach 15,000 feet 7.5 minutes Time to reach 25,000 feet 19.0 minutes Service ceiling 28,000 feet Maximum level speed in M.S. 327 m.p.h. at 8,500 ft. gear Maximum level speed in F.S. supercharger gear 333 m.p.h. at 15,600 ft.

1. Introduction:

...... Performance measurments were required on Beaufighter VI, fitted with the Hercules VI engines.

2. Scope of tests.

...... The performance of the aeroplane on climb and in full throttle flight has been measured. Partial climb tests showed that the best climbing speed was 120 m.p.h. A.S.I. Subsequent climbs made at an initial climbing speed of 140 m.p.h. A.S.I., to give improved cooling, showed a nearly equally rapid rate of climb compared with the climbs made at 120 m.p.h. A.S.I. At 120 m.p.h. A.S.I., the aeroplane climbs at a very steep attitude, and pilots much preferred to climb the aeroplane at an initial speed of 140 m.p.h. A.S.I. Since there is no measururable loss of performance our results are quoted at the higher climbing speed.

...... After these tests had been completed, information was received that the Hercules VI engine had been re-rated and that the R.P.M. boost limitations had been increased. Climb and level speed performance tests were repeated at the new limitations. The climbs were made at the higher climbing speeds.

...... The old and new engine limitations are:-

Old limitations New limitations

Boost Boost R.P.M. R.P.M. lb/sq.in lb/sq.in Maximum permitted for take-off 2800 +7 2900 +8 and full throttle level speed. Maximum permitted for 2400 +5 2400 +6 climb ...... The performance results under each condition are included in the Report. The tests were made between 28.10.41 and 10.4.42.

3. Condition of aircraft relevant to tests.

...... This aeroplane is the prototype Beaufighter VI. Externally it is similar to the Beaufighter I, the main difference being the installation of Hercules VI engines and larger oil coolers and oil cooler ducts.

...... Tapered shrouded slotted flame damping exhausts were fitted on both engines.

...... The aeroplane was painted with the normal green and brown camouflage, not night fighter black. It had undercarriage doors and not skirting pieces as on some previous Beaufighters. 4 x 20 m.m. guns were fitted in the nose and neither the gun tunnels nor the ejection chutes were sealed for these tests. The holes for the 6 x .303" guns in the wing were covered over, but the ejection chutes remained uncovered.

...... The aeroplane had a "straight" tailplane, not the 12 1/2 deg. dihedral version. There was no camera gun above the cabin roof. A W/T aerial was fitted between the aerial mast on top of the fuselage and the tail. Neither A.I. nor I.F.F. aerials were fitted.

4. Loading: The tests were made at a weight of 19,750 lb. with the centre of gravity 49.1 inches aft of the datum, measured with the undercarriage down. Raising the undercarriage moves the centre of gravity aft by 0.6 inches at this loading.

...... The design centre of gravity limits are from 41.0 inches to 51.0 inches aft of the datum, or to 52.0 inches aft including the 1%P S.M.C. aft extension (undercarriage down)

5. Results of tests:

.....5.1 Climb: The results of the climb tests are given in Tables I and II and in Fig.1. These show that at the new limitations the maximum rate of climb is 2,325 ft./min. at 4,600 feet and the time taken to reach 15,000 feet is 7.5 minutes and to 25,000 feet, 19.0 minutes. These times are less than 1/2 minute shorter than the times to height at the old limitations. The service ceiling is 28,000 feet.

.....5.2 Level Speed: The results of level speed tests are given in Tables III and IV and in Figure 2. These show the following:-

Old engine New engine limitations limitations Maximum speed in M.S. 325 at 9,900 ft. 327 1/2 at 8,500 ft. gear Maximum speed in F.S. 334 at 16,400 ft. 333 1/2 at 15,600 ft. gear ...... In calculating these speed the same position error correction has been used as for the Beaufighter I. (Table I., Climb results at old engine limitations, omitted) Table II. Climb results at new engine limitations Ht. in Time True Rate of Comp. Boost Super- stand. from Air A.S.I. P.E.C. R.P.M. Cooling climb Corr. lb./sq.on. charger atmos. start Speed m.p.h. m.p.h. (Mean) gills ft./min. m.p.h. (Mean) gear Feet. Mins. m.p.h. Sea 0 ...... Fully Level 1,000 .4 2315 145.5 140 +3.5 - 2400 +6.0 M.S. open 2,000 .9 2320 147.5 140 +3.5 -0.1 2400 +6.0 " " 3,000 1.3 2320 150 140 +3.5 -0.1 2400 +6.0 " " 4,600* 2.0 2325 154.5 140 +3.5 -0.2 2400 +6.0 " " 5,000 2.2 2285 157.5 140 +3.5 -0.2 2400 +5.8 " " 6,500 2.8 2125 158 140 +3.5 -0.2 2400 +4.9 " " 10,000 4.6 1855 166.5 140 +3.5 -0.3 2400 +5.8 F.S. "

5.8 1855 172 140 +3.5 -0.4 2400 +5.8 " " 12,100** 13,000 6.3 1850 174.5 140 +3.5 -0.5 2400 +5.2 " " 15,000 7.5 1530 180.5 140 +3.5 -0.5 2400 +3.8 " " 16,500 8.5 1370 184.5 140 +3.5 -0.6 2400 +2.9 " " 18,000 9.7 1200 189.5 140 +3.5 -0.6 2400 +1.8 " " 20,000 11.6 980 189 135 +3.8 -0.7 2400 +0.7 " " 23,000 15.3 655 195 132 +4.1 -0.8 2400 -1.1 " " 25,000 19.0 435 199 130 +4.3 -0.9 2400 -2.2 " " 26,000 21.6 325 201 129 +4.4 -1.0 2400 -2.7 " "

32.0 100 205.5 127 +4.5 -1.1 2400 -3.6 " " 28,000+ * Full throttle height in M.S. supercharger gear **Full throttle height in F.S. supercharger gear + Service ceiling Estimated absolute ceiling = 29,000 feet. (Table III., Level speed measurements at old engine limitations, omitted) Table IV. Level speed measurements at new engine limitations Ht. in True Position Compress- Super- stand. Air A.S.I. error ibility R.P.M. Boost Boost Cooling charger atmos. Speed m.p.h. corr. coor. (Mean) Port St'bd. gills gear Feet. m.p.h. m.p.h. m.p.h. 4,000 312.5 302.5 -7.4 -0.9 2900 +8.0 +7.9 M.S. Fully 5,000 316 301.5 -7.3 -1.0 " +8.0 +7.9 " Closed 6,500 321 299.5 -7.2 -1.3 " +8.0 +7.9 " " 8,500* 327.5 296.5 -7.0 -1.7 " +8.0 +7.9 " " 10,000 327 289.5 -6.6 -1.9 " +6.7 +6.4 " " 13,000 325.5 274.5 -5.7 -2.4 " +4.4 +3.8 " " 14,000 324.5 269 -5.3 -2.4 " +3.6 +3.0 " " 10,000 314 277 -5.8 -1.7 " +7.9 +7.8 F.S. " 13,000 324.5 273.5 -5.6 -2.1 " +7.9 +7.8 " " 15,000 332 271.5 -5.4 -2.7 " +7.9 +7.8 " "

333.5 270.5 -5.4 -2.8 " +7.9 +7.8 " " 15,600** 16,500 333 266 -5.1 -2.9 " +7.4 +6.8 " " 18,000 332 258 -4.5 -3.1 " +6.0 +5.6 " " 20,000 330 247.5 -3.8 -3.1 " +4.5 +4.1 " " 22,000 326.5 236.5 -3.1 -3.3 " +3.1 +2.5 " " * Full throttle height in M.S. supercharger gear. ** Full throttle height in F.S. supercharger gear. 6. Discussion of results.

...... It will be noted, as would be expected, the rate of climb has been increased below full throttle height in both M.S. and F.S. supercharger gear, due to the increase in boost at the new limitaions.

...... In level flight in M.S. supercharger gear, there is a small increase in speed (2 1/2 m.p.h.) due to the increased r.p.m. and boost limitations. In F.S. gear, however, there is a decrease in speed of about 1 1/2 m.p.h., above full throttle height at the new limitations. It wouild appear that the increase of power due to increasing engine r.p.m. is small and that the decrease in efficiency at the higher r.p.m. produces a nett decrease in thrust horse power in this case. It seems doubtful in view of these results, whether the increased R.P.M. limitations are worth while, in view of the probable decrease in engine life.