FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1955
1955 - 0426.PDF
426 DRIVINGIRON SEALINGSTRIP SEALINGBLOCK RETARDING RAM FLIGHT, 1 April 1955 The steam catapult is shown below in cross-section. The pair of cylinders can be seen, linked to the aircraft- towing shuttle which runs along the deck. A single piston assembly is illustrated on the left; the tapered retard- ing ram, described on this page, is shown shortened. GUIDEPISTON DISTANCE PIECE MAINPISTON CARRIER DEVELOPMENTS ... launching was sought. The most promising solution was found tobe the use of a long, slotted cylinder, supplied with high-pressure steam from the ship's boilers (a convenient existing source ofgreat power), in which was mounted a comparatively light reciprocating piston. As shown in the diagrams, there are two slotted cylinders inthe Royal Navy's steam catapult, mounted below the deck and extending side-by-side for the whole length of the catapult. Thesecylinders are fed with steam from large receiver-vessels under the control of a separate hydraulic system. The cross-sectionshows the manner in which the cylinders are sealed by a rec- tangular-section steel strip which is bent to a curve of largeradius by the passage of the piston assembly, afterwards return- ing to its seating in the slot. Through the gap left by the raisedsealing strip passes a tongue projecting from the driving key, the tongues from the left- and right-hand cylinders carrying dogswhich are arranged to engage with a shuttle mounted on the night deck. When the catapult is fired, under the control of stations in themachinery compartment and at the side of the flight deck, the aircraft hold-back link is broken and the aircraft is acceleratedforward by the throttle and towing bridle—to the accompani- ment of a goodly cloud of steam. The stroke of the catapult is virtually limited only by the deckspace available, and the pistons and shuttle arc the only moving parts. As the latter reach the forward end of their travel, thetapered retarding rams (see drawing) are pushed into massive cylinder extensions which, in a very ingenious manner, are keptfull of bubble-free water, flowing helically around the walls to the far end and axially back down the centre. The high-velocity dis-placement of this water through the narrow annulus between the rams and the cylinder chokes, and the deflection of the waterby annular buckets at the bases of the rams, brings the whole catapult assembly to rest. The mechanism is then returned to thefiring position by hydraulic power. The steam catapult was designed and developed by BrownBros, and Co., Ltd., of Edinburgh (a director of the company, Mr. C. C. Mitchell, O.B.E., B.Sc, M.LMech.E., A.F.R.Ae.S., beingparticularly responsible, and Mr. J. R. C. Waterston having conceived the retarding mechanism). Trials were carried out inH.M.S. Perseus, and it is now the Admiralty's intention to replace all hydro-pneumatic units by catapults of this type. Shipsnow being converted include H.M.S. Ark Royal, Hermes and Victorious, H.M.C.S. Bonaventure and several American carriers. The Side Lift For many years the U.S. Navy have employed"deck-edge elevators" to hoist aircraft from the hangar to the deck. Such devices resemble the lifts of British carriers but are mountedon the side of the ship; American carriers, not particularly adapted for cold-weather operation, employ open-sided hangars alongsidethe lift. The advantages of such a layout are many, and include the possibility of much easier ranging and striking-down andsimpler movement both on the deck and in the hangar, but British ships have only recently begun to have such equipment (knownin British parlance as the side lift). Such ships as Ark Royal have been equipped with large sidedoors to the hangar deck communicating with a side lift, the latter running up to fit neatly into the re-entrant portion immedi-ately forward of the angled-deck extension on the port side. In Ark Royal, a side lift and two centre-well lifts are fitted, allsupplied by the Fraser and Chalmers works of the General Electric Co., Ltd. The Mirror Sight The operation of advanced types of air-craft from carriers requires, in general, the maintenance of closer limits on the approach path than those normally needed forsimilar machines working from land bases. In the past, the pilot of an aircraft landing on a carrier has been assisted during his MAINUNDER approach by signals from a skilled Landing Signals Officer—or "batsman"—whose task it is to assess and govern the approach up to the point at which he can order "cut" or give a "wave-off." (In practice, a "no cut" technique is now used, as described under the sub-heading "Carrier Circuit" on page 427.) Such anarrangement involves lags in the reaction times of both parties concerned; so much so, that the Admiralty and M.o.S. began tosearch for a better scheme—which would, in any case, have been rendered essential upon the introduction of later types of aircraftwith higher landing speeds. The solution was suggested by Cdr. (E) H. C. N. Goodhart,at present Air Engineer Officer to the Naval Staff, B.J.S.M., Washington (a qualified test pilot who was, at the time, technicalsecretary to the C.N.R., M.o.S.). Like the tricks of the 19th century stage, Cdr. Goodhart's idea is "all done with mirrors"—or, rather with one large mirror, concave about a vertical axis, mounted on the port side of the deck and gyro-stabilized againstmovements of the ship. On each side of the mirror is fixed a row of aft-facing colouredlights; and a set of white lights is mounted abaft the mirror, facing forward. When a pilot aligns himself on his approachpath (in American parlance, when he "gets in the slot") he sees the white lights reflected as a blob of light in the centre of themirror. As long as he keeps this blob aligned with the horizontal row of coloured lights he knows that his approach path is correct.The curvature of the mirror also makes the reflected lights visible to the pilot as he turns in towards the carrier. It is therefore possible to carry out a very accurate approachwithout referring to any other instrument or aid. The elevation of the mirror can be set according to the type of aircraft concernedso that, as the pilot flies down the flat beam of light, his wheels pass just over die tops of the arrester wires.Assisting Cdr. Goodhart in the development of the mirror sight were an M.o.S. team led by Mr. D. Lean of the R.A.E.Some 20 pilots were engaged in trials on board H.M.S. Illustrious and Indomitable; die first trials were made by Lt-Cdr. T. G.Innes, A.F.C., and the late Lt. A. E. Facer (whose death was not connected with the device), and night landings were first madeby Lts. W. Noble, D.S.C., and A. G. H. Perkins, ncidier of whom had previously deck-landed at night. Ultimately, it is intended that one or more installations of themirror sight will be provided on all carriers and at Naval Air Stations. Audio Airspeed Presentation. The speed of approach of deck-landing aircraft, at present between 85 and 110 knots, is expected to rise to a foreseen maximum of around 150 kt. Allowing fora wind over the deck of 35 kt, this means that present closing speeds will shortly rise to at least 110 kt—an increase of 40 percent. This will clearly have the effect of further reducing the time in which a pilot can assimilate approach informationand apply it to his landing. In fact, under die established method of landing, the introduction of faster aircraft would have over-taxed any pilot during the critical period of the final approach. The mirror sight has done much to ease the problem of keepingto the correct approach path; effort was therefore concentrated upon finding an improved method, preferably non-visual, oftransmitting airspeed information. The first specialized type of airspeed indication for Naval usewas the mounting of a conventional instrument outside the cock- pit, where it could be seen without taking the eyes away from thedirection of the approaching deck. Another solution was the fining, in a prominent position, of an A.S.I. with an extendedscale; and another was the "flashing light" system. The latter
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
