Sea Attacker

Sea Attacker by Roy Cross

In common with all the later Spitfires, Seafires, the Spiteful and the Seafang, Supermarine's first jet fighter, the Attacker, was designed at Hursley Park, near Winchester. This establishment centres around a fine old country mansion set in many acres of rolling grounds, surroundings oddly at variance with the sleek aeroplanes which come off the drawing office boards. Test flying is now done at the nearby aerodrome of Chilbolton, previously used by the Americans, who operated Lightnings from it during the war. At Chilbolton we saw the second Attacker, TS 413, which at that time had flown a total of six or seven viceless hours since the initial test hop in June. Test flying of both the first and the second machines really has been singularly trouble-free. The Attac- ker TS 413 is fitted out as a naval fighter, and apart from the usual Navy trimmings-deck hook, etc.-has one or two interesting gadgets which we'll talk about later.

E.l0/44 specification

Part of the drawing office staff at Hursley Park started on design work for the Attacker in October 1944, a month or so after receipt of the E.10/44 specification. Some of the conditions laid out therein may be worth relating, bearing in mind the date they were Issued. The engine specified was the' Rolls-Royce Nene RB-41, itself built to a 1944 specification for a 4,000 lb. thrust engine to power a projected single-seater fighter-probably the Attacker. Four thousand pounds thrust was a lot for those days, and a minimum 550 m.p.h. top speed and 45,000 ft. ceiling were expected, figures which are, in fact, easily surpassed.

Further items were as follows. Armament: Standard R.A.F. four-cannon installation, but with sufficient ammunition for fifteen seconds continuous fire from each gun (the same as for the Spiteful). Tankages: 300 gallons, plus provision for an outsize 270 gallons drop tank. Also dive recovery flaps, and a sealed cockpit with a 3 ½ lb. differential pressure.

Only a small design team could be spared for the Attacker due to the pressing demands for improvements and modifications on machines already in production, but construction of a few minor parts, and jigging up, did begin about two months after design started. In fact, having in mind the tremendous pressure of work then being coped with by Hursley's strictly limited staff, and that the whole works was shifted bodily from the bombed-out Southampton location during a critical phase of the war, it is amazing that the flow of new marks and types for the R.A.F. and Royal Navy never showed signs of drying up.

First flight of the Attacker prototype, TS 409, was on 27th July 1946, by which time the Nene was giving 4,500 lb. thrust. About the only changes made so far on TS 409 after quite a lot of testing are to the engine end of the air intake, the "gramophone horn", to slightly increase efficiency, and the introduction of spring tabs on ailerons and the port elevator, an addition which had been contemplated in any case. Latterly, compressed-air-operated emergency lowering systems for the main flaps and dive recovery flaps have been added.

Naval Attacker

Converting the Attacker for Navy use has meant, as always, the altering and addition of a number of details, but first we'll mention two changes to the second machine which have nothing to do with its intended use as a naval fighter.

The Attacker takes in air for the engine through large ducts on either side of the cockpit, and so as to increase intake efficiency, turbulent air next to the aircraft skin is skimmed off separately, finding its way on the first machine into the belly of the aircraft where a louvre is provided for its exit. This arrangement has been tidied up for machine No.2, on which the boundary layer air is directed smartly to exit grilles just aft and above and below the main intake. Thus the tired air is got rid of quickly and neatly. Incidentally, the boundary layer intakes have since been faired in on TS 409 in order to assess their exact value, and the result has been a slight but noticeable reduction in performance, due solely to the added congestion in the air ducts.

A second minor change to the basic machine introduced on TS 413 is that a steerable double tail wheel is fitted. That on the first machine was a non-steerable type which had the double wheels revolving on a common axle. Due to the rake of the supporting leg, one of the wheels lifted partially off the ground in a turn, scuffed along, and made steering (with the brakes) difficult. On the second machine, the double wheels are fitted with a differential axle, and are moreover adjustable to three conditions: fully castoring (360°); locked central; or steerable from the rudder six degrees either side.

While discussing tail wheels and steering, we might mention the fact that the rudder on the Attacker, as on any pure jet type, is practically useless for steering while taxying due to the absence of slipstream from a propeller. The Attacker can be taxied quite fast with the rudder flapping wildly from side

to side and deviate scarcely an inch from its path. The absence.of slipstream, too, is the reason for the ten degrees forward-rake of the top lip of the jet outlet-about 250 lb. . pressure is exerted by the jet on the bottom lip, and serves to keep the tail hard down when running up or taxying.

Turning to naval gear, the second Attacker has a vee-frame hook near the extreme tail; presumably the presence of the tail jet pipe precludes the use of a sting-type hook as on the Seafang. Also, Seafang undercarriage legs with longer shock- absorber travel are fitted to compensate for the greater shocks of deck landings. The retracting mechanisms of these are so arranged that the legs shorten as the wheels move up, and so are accommodated within the length of the existing housing.

Accelerator gear

Accelerator fittings on the Sea Attacker are of the latest type to be used by Naval Aviation, and are similar to those used by the U.S. Navy, replacilig the old catapult trolley and aircraft spool gear. Accelerator hooks are mounted in the wheel bays, and from them cables lead forward over pulleys ili the deck and down to cordite charges in the bowels of the carrier. Burning of the cordite exerts a growing tension on the cables, tending to pull the aircraft forward. The aircraft is held in place by hold-back gear at the tail until the mounting force snaps the linkage and the machine is shot forward and into the air.

Provision of R.A.T.O.G. caused some minor headaches, since no less than eight rockets were called for. After various schemes had been discarded, the rockets were finally arranged two above and two below each wing so that the resultant thrust forces were inline with the aeroplane C.G. The blast of eight rockets should get the Attacker off the deck in double quick time, but from a visual examination the airframe structure looks more than tough enough to withstand even this tremendous stress.

Ejector seat

The specification E.10/44 mentioned that full consideration must be given to safely evacuating the pilot at all speeds. It was logical, then, to use an ejector seat. Vickers installed their own design of seat in TS 409, and it proved completely satisfactory. Subsequent machines have the Martin Baker seat, now standardised for the R.A.F., and in the case of the Attacker this seems rather a pity, for the Vickers seat is some 40 lb. lighter.

Structure of the Attacker is massive, and we formed the initial impression that the machine would be on the heavy side. For example, the nose section is a heavy-gauge shell, half an inch thick in places and with only an apology for internal stiffening, while elsewhere the skin and some of the frames are immensely strong. Yet in actual fact the Attacker is, at 11,300 lb. normal all-up weight, little heavier than the rather smaller Seafang.

As distinct from the logical, workman-like layout, there are a number of intriguing design details built into the Attacker; the spring-out pilot's footstep is an example, and also the ingenious disposition of fuselage tanks about and between the air intake ducts. Provision for radio servicing is also rather clever, although it exis~ only in mock-up form as yet. The main set is to be housed in the nose above the bottom access door, and may be pulled down on counter- balanced telescopic arms and released at one side to hang loose beneath the nose, completely exposed for servicing. The usual transmitter-receiver and I.F.F. sets fitted (TR. 1464 and R. 3212 were specified) are at present mounted on ordinary fixing, or are taken out to make way for the camera and auxiliary instrument panel of the automatic recording equipment.

Engine installation

The whole engine bay, or plenum chamber, is exposed by removing the compartment ct>ver, which is tightly sealed in flight, like the cockpit canopy, by pneumatic rubber tubing, so that in effect the whole bay is pressurised. During running up or taxying, a temporary depression is likely to set in inside the bay, so that extra intakes are provided in the compartment cover which are sucked inwards to admit air when subnormal internal pressures obtain. Another feature of the installation is the volute bleed around the jet pipe, fitted to break down the harmonic fluc- tuationswithin ihe jet pipe which sometimes cause starting difficulties. The volute bleed is operated via a Teleflex cable from a handle in the rear starboard fuselage side. The tail pipe, by the way, expands as much as It in. in length at full engine power and so is mounted on special hinged linkages.

The overall impression we received from the design staff and from seeing the actual machine is that the Attacker has enormous potentialities for further development. The third machine will have various (unspecified) improvements, while a forth has all surfaces swept back 45 degrees or more, and in either form a determined attack on the air speed record could be made. Even at present, the Attacker is among the fleetest jet fighters in the world; with a few mOre months' development it should become a world-beater.

The jet engine itself is a Rolls-Royce Nene I, which gives 5,000 lb. thrust at 12,300 maximum revs., weighs 1,550 lb. (less jet pipe), consumes fuel at the rate of 1.065 lb./lb./hr. at full power, and measures 49}; in. in diameter. Engine accessories are mounted remotely around the top of the air intake" gramophone horn", driven by a common shaft which may be readily disconnected in the event of removal of the engine. Incidentally, removal of the long tail pipe requires a special jig consisting simply of a long, trolley- mounted, horizontal bar which is run right up the jet pipe. The pipe is then disconnected and rests on padded supports along the bar, which is then withdrawn with, tfte-"-jet pipe threaded neatly over it.

Normal fuel capacity is a shade over 290 gal., giving a range of 410 miles, but a 270-gal. belly tank is available which boosts the range to 1,100 miles.

ATTACKER

LEADING PARTICULARS

Dimensions

Span 36 ft. II in.

Length 37 ft. 6 in.

Maximum height, tail down 9 ft. II in.

Wing area 226 sq. ft.

Weight and Loadlngs

All-up weight-normal 11,300 lb.

Engine Installation

One Rolls-Royce "Nene" engine 5,000 lb. static thrust

Capacities

Fuel tanks: Total Internal capacity. 290 gal.

Auxiliary jettisonable tank 270 gal.

Armament

Four 20 mm. Hispano guns

PERFORMANCE DATA

(Under I.C.A.N. conditions)

Level Speeds (combat rating at 95% of normal all-up weight)

Sea level 590 m.p.h.

10,000 ft. 583 m.p.h.

20,000 ft. 561 m.p.h.

30,000 ft. 538 m.p.h.

Rate of Climb (combat rating at initial weight of 11,300 lb.)

Sea level-6,600 ft./mln Time to height mins. 0

10,000 ft. - 5,600ft./mln 1.64 min.

20,000 ft. - 4,500 ft./mln 3.61 min.

30,000 ft. - 3,280 ft./min 6.17 min.

Operational Ceiling

48,500 ft.,I.e. height at which the rate of climb becomes 500 ft./min.

Range and Duration

Range at 30,000 ft. Normal With 270 gal. drop tank

Average cruising speed. 380 m.p.h. 392 m.p.h.

Miles per gallon 2.94 2.76

Duration of cruise 1.08 hrs 2.81 hrs.

Total distance 410 miles 1,100 miles

Endurance at 30,000 ft.

Maximum endurance 1.6 hrs 3.78 hrs.

Note. - The ranges and endurances quoted above include

allowance for 2 minutes at take-off power, climb to 30,000 ft.,

and IS minutes combat at 30,000 ft.

Take-off Distance

Take-off distance to clear a SO ft. screen in still air 847 yds.

Landing Distance

Over a 50 ft. screen at 9,760 lb. (including 100 gal. of

remaining fuel) 855 yds.