FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1958
1958 - 0723.PDF
30 May 1958 739 altitude, 91,249ft; F-104 Holder of the Absolute Records for Speed and -:,,.- Altitude SUPERLATIVES should have no placein a strictly technical appraisal, par-ticularly when they are the assertions of a publicity-conscious commercial com-pany. It is, therefore, appropriate that this first full description of the Lockheed F-104should appear at a time when its perform- ance has been demonstrated by officiallyobserved flights which promise to bring to it the world records for both absolute speedand altitude—the first time in history that both records have been held by the sametype of aeroplane. The submitted figures are speed, 1,404.19 m.p.h. (about Mach 2.13). The F-104 Starfighter is a product of the California Divisionof the Lockheed Aircraft Corporation. Its general configuration, which is unique among aircraft or missiles of which details havebeen published, was revealed in the spring of 1956. Our issue of April 20 of that year contained an extensive dissertation upon thegeneral design of the aircraft, together with an outline of its history and basic characteristics. It is not proposed to go overany of this ground again; but, given the F-104 as an entity in being, it is now possible to comment upon much of its structuraland engineering design which was previously classified as secret. In the design of a modern high-performance aeroplane there isvery little latitude in which a designer can express his own foibles and promote his ideas; and the F-104 seems to be a typical casein which a design team can explain every feature and prove that it is the only possible choice. For example, one can find standardsheet and sections in the airframe, together with shell-mould and other castings, machined skins, integral stiffening, forgings andimpact extrusions, all in a great variety of materials. Throughout, the design has been most carefully planned to reduce manufac-turing and maintenance costs. Owing to the relatively insignificant volume of the wings, virtu-ally everything carried by the F-104 is housed in the fuselage. As almost half the latter is occupied by the powerplant and its airsupply ducts, it follows that the overall length is considerable; the 104 is, in fact, a full ten feet longer than a Hunter. To facilitate manufacture, the fuselage is broken down intonose, forward, centre and rear portions, and the main centre por- tion is further split into port and starboard halves. As the cut-awaydrawing shows, there are numerous transverse frames, and many of these are very strong forgings—particularly those which carrythe five main wing spars, since these frames have to absorb all wing loads and diffuse them into the fuselage. Many of the largerforgings are close-tolerance "zero-draft" pieces, requiring little finishing.In the design of the wings Lockheed faced a particularly acute set of problems. The thickness/chord ratio of 3.4 per cent accen-tuated the difficulties inherent in driving powered ailerons and flaps (and, in this case, a hinged leading edge), as well as thoseattendant upon designing pipe-runs, electric wiring and fuel- system equipment. At one time it was thought that each wingwould have to be machined from a single slab of light alloy. Another study centred upon the use of a honeycomb core, anotheron the use of forged or cast interior structure and another on casting a semi-wing complete. Finally a conventional structurewas adopted: the major loads are taken by very thick, tapered upper and lower skins and the interior consists of simple, com-pression-formed channel spars and three ribs, one at the root, one at the tip and the third about midway. As far as possible the wing is free from cut-outs. The under-carriage retracts into the fuselage, and accordingly it was found possible to run the skins continuous from root to tip. Each skinpanel is step-milled, stretched to the aerofoil profile and through- riveted to the interior structure. When only one side remains tobe skinned the pipes are put in to carry fuel from the tip or pylon tanks, together with weapon-system wiring for stores atthe same locations. The simple ailerons are hung on multiple piano-hinges and are actuated by ten hydraulic jacks arranged side-by-side. This provides distributed forces along the lengthof the surface (greatly reducing aileron distortion) and permits the use of diminutive jacks capable of being accommodated withinthe inch or so of depth available. Flap actuation is effected by an Eemco electric unit arrangedon each side of the fuselage, driving the surface directly. A different type of Eemco actuator is used to move the hinged lead-ing edge, which can be depressed to preserve the airflow at high angles of attack. A special feature of the 104 is its use of boundary-layer control over the flaps by compressor-bleed air (a system known in Britain as supercirculation or flap-blowing). Air fromthe main engine compressor delivery is taken out through two large ducts, controlled by high-temperature proportional gatevalves, and led outwards to connections at the roots of the wings. These admit the air to spanwise tubes, running the whole 47inlength of each flap and arranged just above the flap leading edge. In the rearward-facing portion of the tube is cut a row of 55 thinslots, each 0.09in deep, O.55in wide and spaced 0.9in apart. Blowing starts as soon as the flap angle reaches 15 deg, and isprogressively increased until the system is at full throttle when the flaps reach their full deflection of 45 deg. Under normal con-ditions the flow velocity through the slots is completely super- sonic at 2,300ft/sec; the system reduces the stalling speed byfrom 12 to 17 kt and the landing run by some 25 per cent, a typical touch-down speed for an operational 104 being 135 kt.As was explained in our issue of April 20, 1956, the horizontal tail is mounted at the top of the squat fin. Both surfaces are built,like the wing, with heavy skins and relatively simple interiors. In addition a 5ft-long ventral stabilizing fin is fitted.The horizontal tail is pivoted aft of mid-chord and is driven by an actuator in the fore-part of the fin. To it is attached theupper rear part of the vertical surface, which slides partially inside the forward portion of the fin-tip as the horizontal tail assumesa negative angle of incidence. Early flight-testing revealed that the 104 could, at extreme speed and altitude, enter a super-stalledcondition leading to uncontrollable pitch-up. To counter this an angle-of-attack sensing unit was incorporated, which first causesstick-shake and then, should the pilot persist in pulling back, reverses the movement of the horizontal tail. The 104 is fittedwith a fully transistorized three-axis autostabilizer, by Lear, Inc. Shown well in the drawing, the undercarriage is exceptionallyneat and comprises three units all retracting forwards into the fuselage (the nose gear on the XF-104 and F-104B retracts to therear). Each main leg is a forging pivoted at its upper end and braced by a single Liquid Spring strut (Dowty patent) manufac-tured by the Cleveland Pneumatic Tool Co. Owing to the restricted size of the wheel bays, the tyre pressure is over 250 lb/sq in; inthe past it has been customary to discard tyres after four landings but a new Goodrich sine-wave pattern promises to extend this bya factor of four. Heart of the aircraft is its powerplant. It is remarkable that—as far as one can tell—neither the U.S.A.F. nor Lockheed have made any effort to fit the F-104 with a rocket motor. Sole meansof propulsion remains the General Electric J79 turbojet, with afterburner—which, it must be admitted, is an exceptionally finepowerplant. Some notes on the J79 appear on page 731 of this issue. It iswell suited to flight at Mach numbers up to about 2.5, and in (Continued on page 742, ajter double-page drawing of the F-104)
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
