FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1956
1956 - 0117.PDF
27 January 1956 / be described as a "one-handed aeroplane." All operation from take-off to landing, including violent manoeuvres, could be con- ducted by the pilot with only one hand on the flight controls, leaving the other available for cockpit operation. The 707's control system was, in Boeing's view, the "ultimate development of a fail-safe and responsive system." All primary controls were operated by control tabs and balanced by unique pressure-plate balances located forward of the surface hinge-lines. The stabilizer was manually adjusted by the pilot except for large trim-changes occasioned by large speed-changes or operation of the wing flaps. In this event, a small electric motor actuated the manual stabilizer trim system for the pilot, if he so desired. The wing-mounted spoilers were the only hydraulically-operated surfaces. Complete loss of the dual hydraulic systems merely reduced the crosswind landing capability of the 707 from approximately 35 m.p.h. to 10-12 m.p.h. of crosswind component. In this event, of course, both the landing gear and wing flaps must be lowered manually. The pilot control-forces and flight-stability charac- teristics of the 707 were "deemed superior by the many airline and military pilots who have flown the aircraft, thus indicating that Boeing design objectives have been attained with a fail-safe system." Structural philosophy.—In the case of the 707, this might be briefly summarized as follows: —(a) Anticipate that structural integrity will inevitably be compromised by flight or ground damage or collisions, defects in manufactureor faulty maintenance in service. (b) Select the structural design criteria to control the consequencesof such damage. Test and redesign and test again to substantiate the validity of the design criteria. Thus Boeing had provideda fail-safe structure that could absorb damage without sudden or rapid progressive failure, thereby providing ample time forroutine inspection to detect any structural damage. (c) Establish close liaison with each operator to aid in maintainingthe original design reliability. In order to satisfy this design philosophy, many specific design criteria had to be established and confirmed by component and/or full-scale tests. A few general examples could be listed: (a) Provide multiple load-path structure such that a single componentfailure will not cause the structure to fail. This could be applied, for example, to the attachment points for the verticalfin, control-surface hinges or the more complex structure around cutouts for windshields, doors and windows. (b) Provide tear resistance by incorporation of tear-stopping rein-forcement material and/or selecting low working stress levels. (c) Select low working stresses to preclude abnormal fatigue main-tenance or inspection requirements. (d) Provide ample fatigue endurance after partial failure to provideadequate time for discovery of any failure. (e) Use plug-type doors, hatches and windows to eliminate catas-trophic failures of latches and hinges. When creating a light and efficient structure, a designer had to rely heavily on past experience. Thus the extensive structural tests completed on the B-47, B-52 and prototype tanker-transport were of great value. The B-47 and B-52 had been static-tested on the ground and flight-tested to establish loads and load distri- bution under all manoeuvres. Flight-load testing had already been accomplished on the prototype 707, as well as flight flutter tests to ensure a flutter-free structure at all speeds up to M = 0.95. Fatigue testing of critical wing joints, splices, and structurally complex areas or sections was now being accomplished at Seattle. Additional fatigue tests on fuselage components, body tear-resist- ance tests, and, later, full-scale body fatigue tests were planned. As this work proceeded and was evaluated, additional testing would be planned as required. [Continued overleaf The curves below for the Boeing 707 family show C.A.R. field lengths required for take-off (left) and landing at sea level ISA. Though its landing requirements are relatively modest, the 707 will apparently need rather longer take-off distances than are generally available at major airports today H its payload-range capabilities are to be fully exploited. 117 Subject Aerofoils B-47 wings B-52 wings 707 wings Nacelles ... Flutter ... No. of models 30 34 68 53 306 24 Type of model Two-dimensional Complete, three-dimensional Complete, three-dimensional Complete, three-dimensional Pod and strut configurations Complete dynamic-response models Tabulated above are details of wind-tunnel testing carried out by Boeing in the development of their three large multi-jet projects— B-47, B-52 and 707. Aerodynamic tests accounted for 10JD93 wind- tunnel hours, and flutter-test time totalled 4,930 hours. 40 VI ^> M•v _» g20 fc t— tt Ar FLA i ^^ DOWN B-377 FLA PS UP \ i 120 140 (60 180 200 220 240 INDICATED AIR SPEED (m.p.K) 2«0 Comparison of rates-of-roll of the Boeing 707 (upper curves) and Stratocruiser. •PARIS-NEW YORK (67 mph HEAD WIND 1.000 2J3O0 JjWO 4.000 RANGE (it. miles) M»0 4.000 7,000 10.0001- 5,000 WOO 4.000- 2JW0- 707-120 7.000r 707-320 180 200 GROSS 240 260 WEIGHT (Ib 280 300 K1.OO0 (Above) Payload and cruising speed (upper graph) are here plotted against range for all three versions of the Boeing 707. Each is assumed to take-off at maximum gross weight, and allowance is made tor fuel reserves of 7,600 US. gal (707- 120) and 1700 US. gal (707-220 and 707-320). o 140 150 160 (70 1»0 1»0 GROSS WEIGHT (b x UXX
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
