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Aviation History
1926
1926 - 0197.PDF
MARCH 25, 1926 LONG-DISTANCE AEROPLANE FLIGHTS* MR. ALAN J. COBHAM, who has just completed a remarkable 17,000-mile flight from London to Cape Town and back, gave a very interesting lecture before the Royal Aeronautical Society last Thursday. Mr. Cobham first apologised for being unable to prepare his lecture, as he had intended, but he had had so little time since he came back—in fact, he had only started on his paper that afternoon. There were, he said, two main types of long-distance flying. Firstly, long non-stop nights, and, secondly, long flying journeys where many landings were made. The former, so far, had mostly been made purely as stunts or demonstrations of propaganda of some particular type of aircraft. These, were very spectacular, and would, he thought, always be a good advertising medium. A few had been made as a commercial proposition, to carry some important dispatches, photographs or special passenger. The length of a long non-stop flight depended practically on the petrol capacity of the aeroplane, which probably had been increased until the extra weight brought the machine up to its maximum loading. Thus it was up to the designer to work out which was the most economical—a machine that could lift a tremendous load at moderate cruising speed, or the very fast machine which could not carry such a big load. Personally, he thought, the greatest long-distance efficiency came from a machine half-way between these two extremes. On the question of petrol economy he thought the extra speed gained by opening out the engine in no way paid in distance covered for the extra fuel so used—the greatest distance on a given quantity of fuel could always be obtained by running at approximately two-thirds one's horse-power. Mr. Cobham then pointed out the great disadvantage to a long non-stop flight, especially for commercial work, owing to the necessity of an enormous petrol reserve that must be carried in order to cope with a head wind. He showed that the weight of such a reserve was far greater in proportion to that required for a short-distance flight. The question of refuelling, said Mr. Cobham, was purely a matter of organisation, and to-day, even on the best aero- dromes, it was hardly possible to land, fill up and get away again in under an hour. He thought the job should not take one quarter of this time, and as proof he quoted the case of the King's Cup Race (1924), where competitors were allowed ten minutes on their handicap for refuelling. Although it was doubted if this could be done in the time, by proper organisation it was actually accomplished within two minutes. If it was possible to refuel in two minutes, what use was there, he asked, in a long non-stop flight ? It would be seen, therefore, proceeded Mr. Cobham, how important a part good ground organisation would play in the development of aviation. The main thing in all flying was speed, so why, having gained hours by flying from one place to another, waste it all again by inefficient service on an aerodrome ? He therefore emphasised the importance of revolutionising the existing modes of refuelling. Instead of pouring cans of petrol through a hole in the top of a tank, or pumping, slowly, in 5-gallon measures through the same hole, surely in these days of modern engineering it would be possible, having landed within 20 yards of a given spot, for a flexible pipe to be fitted (by a quick attachment) to a valve at some accessible and convenient point on the aeroplane and petrol under pressure put into the tanks at 50 gallons a minute or more ? The varying changes of weather conditions, said Mr. Cobham, was one of the great difficulties of long non-stop flights, owing to the fact that the great distances covered very often go from one weather zone to another. Therefore unless there was an elaborate system of wireless communica- tion, the machine that landed often would have the advantage of picking up weather reports of conditions ahead. Another point to be remembered on long non-stop nights was that even for the most hardened it was not good for the passengers—none would do it for pleasure and few out of necessity. It was also very difficult to maintain regularity on a long non-stop flight. Referring to the effect of long non-stop nights on the pilot, Mr. Cobham said that from his own experience he always noticed that the first half-hour of the flight always seemed the longest. After four or five hours continuous flying, except that he may become a little fidgety he does not usually notice any undue strain and can generally carry on without any desire for food—possibly because he is fed by the oxygen in the * Paper read by Mr. Alan J. Cobham before the Royal Aeronautical Society On March 18, 1926. 177 pure air in which he flies. In his own longest non-stop flight(London-Madrid) of 9 hours 40 mins. he was quite fresh at the end and able to attend to his refuelling and then carry onfor another four hours to Tangier. He thought the most fatiguing part of flying was worry—worry caused by lack of confidence in the machine and engine and the worry of whether one's destination can be reached onthe petrol supply, or the difficulty of finding one's way. As time goes on improved aircraft will banish most of theseworries, especially with the development of the thrce-engined machine. The only other worry the pilot has is that ofencountering bad weather. Regarding the subject of navi- gation, Mr. Cobham stated that the pilot while piloting couldnever be a real navigator, because while it may not be a mental impossibility to do the two it is a physical impossibilityas the pilot only has one pair of hands ! He thought, however, that the navigator should most certainly be a pilot,and possibly in the future the stepping stones in the pilot's profession would be second pilot, first pilot, and commandernavigator. The commander navigator of the future big air liners would have had years of experience in piloting a machineover a particular air line, and he would be in charge and navigate the liner. The first pilot would no doubt take theaeroplane off the ground and put it on its course in the air, when it will be taken over by the second pilot. On moments ofemergency or when sighting the next port the first pilot would take charge. His own system of navigating was purely one of deadreckoning combined with map reading (using the map to check up drift). A good system was to draw a line on the mapbetween the two points and then take the compass bearing with a protractor. Having allowed for variation and deviationand ascertained magnetic bearing and set the compass accord- ingly, one set off on the bearing indicated. After the firstfew miles one located the first landmark on the line—if one passed right over it the course was free from drift, if notone must allow a few degrees (right or left) to compensate this. This was repeated every few miles, but after 20 or30 miles it was quite simple to find out the correct bearing, allowing for drift, and by carrying on this course it was easyto hit up one's destination by continually checking up the position by the line on the map. After referring briefly to other matters regarding navigating,Mr. Cobham came to the question of long-distance flights in the nature of aerial tours, from one country to another,or long-distance survey flights across the world. Possibly, he said, these flights were the finest test for both machine andengine that it was possible to have. From his own experience one could fly a machine round an aerodrome for years andreally get to know little about it, for it was not until one took that same aeroplane out into the blue across the worldthat one began to find all its faults and snags. For general touring work and everyday long distanceflights it should be remembered that an engine was required in the early days of aviation that would run on any kind offuel and lubricant that could be found available. On the other hand when special supplies were laid down these diffi-culties were eliminated. In comparing his two recent flights—Rangoon and back,and Cape Town and back—Mr. Cobham said that the out- standing difference between them was the fact that whereasthe flight to Rangoon was accomplished on a DH 50 with a 230 h.p. Siddeley " Puma " engine, the flight from Londonto Cape Town could never have been accomplished with this engine. That was why they had to install extra horse-power in the form of a Siddeley " Jaguar ". This was mainly due to the high altitude aerodromes of Central Africa. Referring to the subject of rarefied atmospheres, Mr.Cobham stated that there were three ways of getting over the difficulty. One was by light loading, the other was by extrahorse-power, and the third was by constructing huge aero- dromes. Personally, he thought the best course of action wasto adopt some of each of the last two—construct a machine with about 35 per cent, more horse-power and an aerodromedouble the usual size, a good 1,000 yards square. Mr. Cobham then referred to one or two instances in this connection thatoccurred during the London-Cape Town flight. Mr. Cobham stated that he had found on long distanceflights when journeying across the world that providing one had sufficient sleep it was possible to keep up, providing alsoone had no other undue worries, six to eight hundred miles per day, and that after the first fewr days one settled down tothis mode of existence, getting better able to carry on at this rate as one progressed.
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