THE ELECTRAS

Evening Post, Volume CXXIII, Issue 133, 7 June 1937, Page 10

THE ELECTRAS

ALL-METAL PLANES

LANDINGS AT RONGOTAI

REAL AIR SPEED

Though the Wellington-Auckland air service of Union Airways will not be officially opened until June 26, the two | first Lockheed Electra aeroplanes will j probably do a considerable amount of test flying 'over the route in the meantime. The first visit to Rongotai may be made early next week. The Electras are all-metal machines, the principle material used being a high strength duralumin with a protectiv: skin of pure aluminium on either side. Castings are either of nickel steel, one or other of the aluminium alloys or magnesium alloys, and where strength is not required aluminium is used for extreme lightness. Stainless steel is also used for a few special purposes. Fuel and oil lines, electrical conduits, and junction boxes are of aluminium. The wing and fuselage are of the type technically termed j stressed skin construction. | After the first Electra was built it was turned upside down and loaded far above the calculated dynamic factors, with 29,000 pounds of bagged • sand on the wings and 10,000 pounds of pig iron on the engine mountings— j over 17 tons. Under this extreme test the wing tips, 55 feet apart, sagged, to a maximum deflection of only five ■ inches. The loading was removed, and ; from the testing section of the factory j the type machine went into regular , service and remains in service today. ; Such a test is, of course, not practicable with other than metal-clad wings and fuselage, and is repeated .only when new models are produced, not for each aeroplane. The empty weight of the Electras of the model bought by Union Airways is 6500 pounds, that is, a little under three tons, but with ten passengers, two : pilots, mails, freight, and baggage, the ; maximum flying weight is 10,500 pounds, so that the two 400-450 h.p. Pratt and Whitney Wasp Junior en- ; gines lift 4150 pounds of useful load and j : fuel, and the claim is made that these | machines carry the largest useful load : in' proportion to gross weight of any comparable transport machine. CRUISING AT NEARLY 200 M.F.H. Top speed, with full load and full j engine power (400 h.p. from each en- j gine, for though each will develop 450 j h.p. this is used only for take-off and emergency runs of brief duration) is 205 miles an hour at 5000 feet, but allout speed is of far less importance than are cruising speeds; in fact, maximum speed interests transport operators very little, for top speeds do not pay, except in emergency, and emergencies are no part of transport operations. Cruising ; speeds, however,, are still very high, ] well in excess of the top speed of any ( other commercial aeroplane in New Zealand, but ■they vary considerably according to the altitude at which '• flight is maintained. 1 The Electra's cruising speeds vary < from about 160 m.prh. at sea level, with the engines cut back to 260 h.p. each, to 192 m.p.h. with the engines de- i livering 300 h.p. at 9600 feet, but a lot < of play can be made with varying altitudes and engine power; for instance, j if the stage is a fairly long one a climb ; to 12,000 feet may bring fuel economy. . for at that height 183 m.p.h. can be held . with only 260 h.p. per motor. The four wing tanks hold 155 gal- ; lons of petrol, weighing just over half , a ton, but normal filling on American. , airlines is 130 gallons, and as this gives j a cruising range which would allow 1 the longest New Zealand stage to be , flown there and back and still leave a j margin, far less fuel than this will normfily be carried, making room for pro- j fitable loading and for economy,' for , the greater the fuel weight the more fuel will be burned in carrying it. ( RANGE WITH FULL LOAD. 1 With two pilots and ten passengers. ] (allowed for at 170 pounds each) full , fuel and oil tanks and half a ton of J mail, freight, and baggage, the two en- , gines, at 300 h.p., eat up 42 2-3 gallons j of petrol an hour, giving a normal i cruising range of 675 miles. Cut back , to 260 h.p. the motors take 35 gallons , an hour and the range is increased to . 800 miles. To allow 12 stone all round j for pilots and passengers gives a pretty fair margin and it will be very seldom ( that the maximum passenger figure •, will be reached—ten wrestlers would ■ do it, but wrestlers are not gregarious t and travel singly or in pairs. . However, with everything full and everyone a heavyweight or a middle- * weight, the machine will climb to 22,000 feet, something over four miles, with a ' rate of climb from sea level of 1000 J feet per minute. On one engine full load can be taken to 5000 feet and ' maintained there till the completion of' 1 the flight; with lesser loads the ceilings c are higher. OFF THE GROUND IN 300 YARDS. t A point that is of particular interest f to Wellington is the take-off run of these t machines. They. are guaranteed to i leave the ground, with the full load of E twelve-stone passengers, mail, baggage, £ and freight, from a run in still air of r 892 feet —that is, the take-off run is t specified as 850 feet, covered in 13 sec- j onds, and the guarantee is that this specification will not be exceeded by c more than 5 per cent. As the shortest j runway at Rongotai is over 400 yards f there is a fair margin even under the l least favourable landing and take-off conditions, that is, when there is not < a breath of wind, for, with the run ) made into the wind take-off and land- j ing are considerably reduced in length, j In still air—which sometimes does occur at Rongotai—the runs would be made over the greatest available length, of 900 yards or so. BUT RONGOTAI MUST BE ENLARGED. Mr. Moye Stephens, the test pilot from the Lockheed headquarters in California, discussed this point with a "Post" reporter while he was in Wei- ] lington, and said that he had no doubt at all about landing at Rongotai, par- J ticularly as the fuel load need not be ' anything like the maximum to give an £ ample margin over the stages out from f Wellington, but he did not say that, * because the runways at Rongotai were A sufficient for the Electras, the aerodrome should be regarded as satisfac- £ tory, for larger and heavier machines 3 were bound to come to New Zealand c within a few years and for such ' larger machines the present runways ' would not be adequate to give a safe t margin. f Practically the same words, it will be I remembered, were used by Mr. W. 1 Miller, a high official of the United States Bureau of Air Commerce, when £ he was in Wellington a few months 1 ago. •