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Aviation History
1948
1948 - 0630.PDF
502 FLIGHT MAY 6TH, 1948 The Franklin engine is cooled by a fan, the coofing air passing through the Icuvres in the roof of the engine compartment. The ends of the exhaust pipes can be seen on each side. The Irvin-Bell 47B but, briefly, the bar, which is mounted below the rotor head and at 90 deg to the blades, tends to remain in its plane of rotation. It is hinged to the mast by a " see- saw " arrangement, and if the mast is tilted, the bar would remain in its former plane but for the friction in the attachment, which gives it a slight tendency to follow the mast. This following time is under control by means of two hydraulic dampers. It should be explained that the stabilizing bar is linked to the cyclic pitch control so that a tilt of the rotor from the datum provided by the bar is automatically corrected. Introduced into the system is what is termed a mixing lever in the control linkage, so that the rotor is under two controls: that of the pilot and that of the stabilizing bar. By suitable adjustment of the hydraulic dampers, the cor- rect compromise is achieved between stability and control. One might sum-up the action by saying that the stabilizing bar corrects small angles of tilt, such as might result from gusts of short duration, while the pilot corrects larger dis- turbances. In still air the 47B can be hovered for short periods with hands off the controls. Reference has already been made to the fact that forward speed is limited to 92 m.p.h. It is difficult to assess cruising speed, since this can be varied a good deal as circumstances require. However, in transition from hovering flight to A four-wheeled undercarriage is used on the 47B, The two front wheels, one of which is shown here, are castering. The pitch of the tail rotor is operated by the pedals in the fore- ground, and a cycli: pitch control column for the main rotor is . , seen behind them. forward flight less power is required, until a speed of about 50 m.p.h. is reached, when the power required begins to rise again, owing to the rapid increase in drag. Thus in still air a speed of about 50 m.p.h. would, presumably, give the most economical flight. „ The 47B has an empty weight (including trapped fuel and oil) of 1^521 1b, and the normal gross weight is 2,108 lb, the normal load being made up as follows: Pilot and passenger, 340 1b ; two gallons of oil, 15 lb ; 32 gallons of petrol 192 1b ; luggage, 40 lb. Since, however, the machine has a permissible gross weight of 2,200 lb, the disposable load may be increased to 679 lb. Main dimensions are : — Maximum length . . . 41ft ioin Height 8ft 6in Main rotor diameter 35ft i^in Tail rotor diameter 5ft 8|in Stabilizer bar 8ft 4in Wheel base 7ft 5-|in Wheel track 5ft loin CASUAL COMMENTARY (Concluded from page 499) That being so, I am surprised that the industry does notshow more signs of wishing to work as a complete team where technical experience is concerned. There are far too manvcases of wasteful overlapping, and particularly of the obstinate ploughing of lone furrows. Time after time, firms can bewatched repeating each other's errors and learning the hard way, without even an attempt to obtain the advice and help ofthose who have done the very same job before. Competitive secrecy will always be necessary over advanced projects, andone can hardly expect any^ successful firm to hand over its knowledge to the stragglers*. But there are certain develop-ments of a general nature—sueh as those concerned, for in- stance, in pressurization or aerodynamics—about which infor-mation is a\'ailable merely for the asking. Any technician employed by firm A has merely to visit firm B to be told ofthe problems to be expected and the means by which they may be overcome. It is generally as easy as that, yet the twofirms might often be a couple of million light years apart for all the advantage that is taken of the opportunities available. In particular, I should say that Farnborough is insufficientlyused. The R.A.E. should have quite a bit of full-scale infor- mation of one kind or another, and I don't altogether believethe superior people who deny the value of model tests. TJic cynics who offer the report on the spinning tests of the B.A.T.Bantam as the latest available aerodynamic information just haven't been to Farnborough recently. Postscript: A perfect recent example of a misleading ref'herring has been the communication-cord story after the Wins- ford train crash. The fact that the cord was pulled, or thatthe train stopped from any cause whatever, clearly has no bearing at all on the primary cause of the accident. But sucha story acts as a useful cushion for some less attractively dramatic reality.
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