FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1964
1964 - 0486.PDF
;50< •4 8* ft* *50 16-77 .0 856 DISTANCE-NAUTICAL SUPESSOMC ^.iziz SUBSONIC TIMt IH HiNU'ES iso ?ou HUES * FUGHT /nternotiono/, 20 February (964 297 Rg 6 Comparative descent profiles for the Concord at different speeds PROGRESS WITH THE CONCORD (Continued from p. 273) traffic also, so it is an emergency which is already allowed for in traffic scheduling. The onset of individual flares, however, is rapid and should one occur whilst the aircraft is in flight a change of flight plan to permit cruising below 50,000ft can be made with the Concord's normal fuel reserves. Cosmic radiation detection apparatus will be carried on the aircraft and an emergency descent could be made within a few minutes of detection of a build up in radiation level. Radiation due to contamination from accumulated radioactive debris in the aircraft is almost certain to be unimportant. It is more likely to endanger maintenance personnel due to accumulated debris on airframes and engine components, but with special cleaning and the use of protective clothing the hazard can be eliminated. Noise Noise, like dirt and friction, is an unwelcome but impor- tunate companion to useful work and the cost of reducing it to a negligible level is often prohibitive. As a symptom of wasted energy, it must be avoided at source wherever possible. Beyond certain limits, it is intolerable to human society and in extreme cases it can cause physical damage; these limits must obviously be observed. Below them, noise should be mitigated to the point where economic aspects prevail. First generation subsonic turbojet transports have probably already reached the tolerable noise limit in respect of adverse community reaction. In this respect the Concord presents no new problem. It has been designed throughout with existing and future airport standards in view and even if it is marginally noisier at commencement of take-off than other four-jet transports of similar or greater weight, it is likely to be quieter on the climb because its large reserve of thrust will permit partial throttling very soon after take-off. The novel feature to be catered for is the sonic boom which accompanies a supersonic aircraft continuously along its flight path. Although only of short duration at any given point, the sonic boom carpet commences with acceleration through about Mach 1.13 and ends with deceleration through the same speed. It has been alleged that populations will be exposed to a "supersonic threat" in the form of a never-ending noise pattern ranging from "the brave music of a distant drum" to the oppression of a full-throated thunderstorm immediately overhead, accompanied by breaking glass and falling plaster. This prospect, if true, would indeed be a grim one but on this whole subject there has been far too much speculation based on insufficient firm evidence. The aviation authorities of at least three countries have been observing public reaction to supersonic military aircraft over a period of several years and seem close to agreement on "overpressure limits" with which civil aircraft will be required to conform. The intensity of overpressure in free air is a function of aircraft weight and altitude, ™t is complicated near the ground in a random manner by reflection and focusing effects which magnify the effect into a "pressure jump" nominally about twice the free air overpressure, but statistically varying around this value. Observations of public reaction suggest that pressure jumps of 0.51b per sq ft are hardly noticed, while those up to 1.51b per sq ft produce some isolated complaints. Frequent pressure jumps over 2.01b per sq ft, however, represent an unjustifiable nuisance. With the present Concord weight appropriate to transcontinental operations, it is estimated the pressure jumps will not exceed acceptable daytime levels. Mach 3 transports of necessarily greater weight would have to cruise at least 10,000ft higher to achieve comparable intensities. On descent, in order to minimize focusing effects, it is important to avoid a nose down attitude at too low a height before decelerating through Mach 1.13. Operational Performance Like subsonic aircraft, the Concord has a wide choice of climb techniques, but in fact these boil down to the compromise between minimum fuel requirement and mini- mum sonic boom. Fig 3 shows a typical long range profile. For minimum fuel consumption the flight path would be a climb at Mach 0.3 from sea level to Mach 0.6 at 5,000ft and then acceler- ation to Mach 1.13 at 36,000ft followed by an accelerating climb to cruising altitude and a speed of Mach 2.2. However, the boom consideration delays acceleration beyond Mach 1.13 until 44,000ft is reached, with an unavoidable fuel penalty in consequence. Accelerating climb commences at 44,000ft and ends at 54,000ft at Mach 2.2 with no constant altitude acceleration phase. Thereafter the aircraft cruise-climbs at constant Mach 2.2 to about 63,000ft where let-down begins. Descent is supersonic down to 50,000ft, where it decelerates to Mach 0.95 in level flight, thereafter descend- ing at that speed to 30,000ft and then continuing descent at 255kt CAS. In preparing the flight plan, to keep as closely as possible to the foregoing profile, values of all factors affecting fuel requirements will need to be fed into the computations. These factors include (a) temperatures at the point of take-off and throughout the remainder of the flight, (b) airways distances between departure and destin- ation airports, (c) climb technique required by air traffic control, (d) reserves for diversion and holding, and (e) effect of winds. It is hoped that supersonic aircraft will not be forced to adopt a stepped climb procedure, which will require about 4 per cent more fuel in the cruise. As a result of discussions with the various interested airlines, the Concord has been optimized for eight basic missions, covering London to New York and return and Paris to New York and return, both in winter and summer. These take into account actual "air- ways" distances, fuel reserves, available runway lengths, allowance for weight of full flight systems and operator's items, together with actual winter and summer temperatures and prevailing winds. From this study it appears that the maximum weight for an aircraft to operate on the North Atlantic route is determined by the prevail- ing winds on the west-bound mission in winter, and by high temper- ature at take-off at New York on east-bound operation, in summer. It will be seen from the payload range curve in Fig 4 that the Concord is well ahead of FAA recommendations for fuel reserves. The curve shows the datum aeroplane with the effect of applying both the US SR 427C formula for fuel reserves, which we under- stand is being used for the analysis of American SST's, and those of customer airlines. The former calls for a reserve quantity of approximately 23,0001b of fuel comprising: A quantity equivalent to 10 per cent of the flight time; a diversion of 260 n.m.; and 30min holding at 1,500ft. The latter reserve formula calls for about 30,0001b of fuel which typically comprises: 5 per cent of stage fuel; 15min holding at 30,000ft at destination; a diversion of 260 n.m. from sea level; Fig 7 Comparison of the Concord's modest field-length require- ments with those of a typical subsonic jet MAXIMUM : TAXE-OFf • WEfCHT ,-- HAXIMUM | LANDING «)GHT !• FlttS 1-EXG1H REOUIftEO-Fi ?.ooo woo tooo aooo 3" 1,000 2500 iyo '•-• $^830^' i£^ •
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
