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Aviation History
1959
1959 - 2395.PDF
274 FLIGHT FLIGHT-PLANNING MADE EASY . . . throttling and max. continuous power, this means that power willnot affect the outcome of the flight and may be chosen to give the most convenient cruising height. Cruising height is determined by stopping in the T.A.S. graphat the mean anticipated air temperature, and then running into the height graph on the right to read off, on the shaded or dottedscales as appropriate, cruising height. If the original entry into the headwind graph had terminated in the white area, heightshould be determined, generally speaking, as mid-way between the shaded and dotted heights (T.A.S. being reduced 5 kt for eachthousand feet below dotted height, since wind is reducing by an average of 5 kt per thousand feet in the white area). To determine flight time, subtract from T.A.S. the mean head-wind component at mean cruising height, and divide this into track distance to give equivalent cruising time. Add 15 minutes tothis to allow for climb and descent. To ascertain arrival weight (i.e., weight l,OOOft over the destina-tion, assuming that all reserves are intact except for en route fuel reserves) enter the second chart, as shown by the arrow, withT.A.S. and run through air temperature, flight time and arrival weight, finally reading off take-off weight. This is the least take-off weight in which the flight can be made,allowing for a 5 per cent en route fuel reserve. If runway con- siderations permit a heavier take-off, either the flight can be madeat a higher T.A.S., or more payload can be carried. In this case select a higher speed and go through the process again to find anappropriate take-off weight. In many cases where "dog leg" tracks along airways makeoverall averaging of winds and temperatures unreliable, a sector- by-sector flight plan is required. (The word sector, in this context, Among the Britannia operators making use of the new flight planning method are Cubana, who have four Britannia 318s in service means a segment of one particular flight, and does not imply thata landing is made.) In this case, the procedure described above should be run through for each sector, but instead of running downto the flight-time graph, turn off at the sector-time graph and into the sector-starting-weight graph to determine sector fuel. For the first sector, starting from take-off, 1,500 lb should beadded to sector fuel and ten minutes to sector time to allow for take-off and climb. For the last sector, 500 lb should be subtractedfrom sector fuel and five minutes from sector time to allow for the descent. These quantities do not vary much from one flight toanother. If you emerge from the chart with less than the "minimumsector fuel" (i.e., the minimum fuel required by operational requirements below which it is never permitted to go), then, ofcourse, it is possible to use a higher speed. It is in this way that, by saving aircraft hours, complete extra flights can be squeezed inbetween checks, thus saving money. The graphs at the bottom of the first chart, so far not referredto, are an in-flight guide to achieving the optimum flight that has been planned. In practice this amounts to deciding when tochange from one to another of the cruising heights permitted by A.T.C. The example shown by the dotted line tells the captainthat the best time to change, in one particular situation, is when the A.S.I. shows 230 knots. Another use for this part of the chart is in planning the quickestpossible flight regardless of fuel used, in accordance with the dictum that flying time costs more than fuel. Engine power isdecided as before, and you enter with 250 kt I.A.S. (Britannia Vno, recently increased to 258), running up to the 2,000ft or4,000ft lines depending upon the step-climbs required by A.T.C., or to the "basic" line if a drift-climb is permitted. Thence runacross to approximate mean weight, then up to T.A.S. (shaded or dotted as appropriate), and also via air temperature and meanweight again to height. The system makes it possible also to determine quickly, in caseswhere A.T.C. prohibit use of a particular height band, to go above or below this height. In other words, it is possible in a fewseconds to see whether the aircraft is too heavy to attain the necessary height, and if so what amount of throttling is needed tofly below without exceeding Vno. One possible limitation of the method is that it does not, in itspresent form, make allowance for three-engine cruising. How- ever, range of the Britannia on three engines is claimed to beabout the same as on four, and destination can still be made, though at a lower height, for the same I.A.S. In general, an enginefailure would require a drift down of 7,000ft or 8,000ft. The foregoing provides merely an outline of the method, whichmay well come to be used regularly by Britannia operators, in place of, or at least as an alternative to, the full "steam" manualmethod. It is indeed already used by C.P.A.L., Cubana and Hunting-Clan, and R.A.F. Transport Command are said to bemost interested. Furthermore, the principle of the method may well be adapted to other turbine aircraft; and Bristol will havemade an important contribution not only to the operation of their own product, but to the art of flight-planning in general in theturbine age. j. M. R. FOUR NATIONS, THREE JETS YJ^ITHOUT doubt one of the most significant events of recent*~ times in the field of air transport was the equipment agree- ment in October 1958 between S.A.S. and Swissair. Althoughthe terms of this agreement between the carriers of four sovereign nations have been recorded and commented on in Flight on anumber of occasions, it is of particular interest to note the follow- ing abridged extract from Swissair's annual report for 1958: — "During the course of the year under review it became ever moreapparent that the three DC-8s we had ordered would not be adequate to put us in a sufficiently competitive position in the period beginning1960. "We made a long and thorough investigation to find the best possiblesolution for our company. Right from the start we were forced to take account of the characteristics of our route structure which consists oflong, medium, and short segments, with traffic, in some cases, varying greatly. Considered from this standpoint, there was no doubt that afleet made up of three types of turbo-powered aircraft—with varying range—would be the best solution, and that, in the interest of our gainingthe best possible competitive position, they should all be pure iet. On the other hand, considerations of operational economy pointed equallyclearly to the advantage of restricting ourselves to two types of aircraft. "It so happened that our friends in S.A.S., whose network, like ours,consists of long, medium, and short segments, were faced with similar problems. As both companies have thus far followed practically thesame policy in the purchase of new equipment, they both own highly similar fleets of propeller-powered aircraft. Both have also orderedDouglas DC-8s. Moreover both companies agree to a great extent on their basic concepts of air transport operations, and both work without government subsidies and without state intervention in the conductof business. "In view of our past cordial relationships, it was only natural forSwissair and S.A.S. to attempt to find a more economic solution to the problem of changing over to jet equipment than either carrier wouldhave been able to find alone. The result of our studies and negotiations, as approved by the boards of both airlines, may be summarized asfollows: — "Swissair and S.A.S., by the beginning of 1961, will each introducethree types of jet aircraft, namely the Douglas DC-8 for routes with particularly long stages and substantial traffic, the Convair 880 forroutes with medium-length stages, and the Caravelle for the more important routes in Europe and the Mediterranean area. All aircraftof these three types will be completely standardized for both com- panies. Maintenance will be divided: S.A.S. will handle overhaulingand certain periodic maintenance checks for Swissair's DC-8s and Caravelles, and Swissair will take on the corresponding work for S.A.S.Convair 880s. Swissair has ordered five Convair 880s costing a total of 170 million francs for planes, spares, special operational equipment anda flight simulator. Of these, Swissair is leasing two to S.A.S. for a period of four years. On the other hand, S.A.S. has ordered four addi-tional Caravelles which will likewise be leased to Swissair for four years. "Each carrier, in principle, will only need to purchase parts of thetypes of aircraft for which it does the maintenance work. To a con- siderable extent crew training will be carried on jointly. In every waypossible, both carriers will also assist each other in engineering and operational matters. Hand in hand with this technical co-operation,both companies will continue to work together on the commercial side as in the past."
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