FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1939
1939 - 1254.PDF
APRIL 27, 1939 FLIGHT. k LOW-POWERED PERFORMANCE Features of the Bibi 550 : Side-by-side Cabin Flying at 120 m.p.h. on 60 h.p. GENUINE and saleable low-powered aeroplanes have been out and about for the last thirteen years or more, so it is not surprising that we should now have reached the stage when a maximum speed of 120 m.p.h. should be obtainable with side-by-side cabin seating on little more than 60 h.p. The old original Moth, after all, had a maximum of 90 m.p.h. on much the same power, and this worthy machine, though a tandem- seater, was a somewhat adequately bestrutted and braced biplane. Curiously enough, the price in England of the Benes Mraz Bibi 550 monoplane is almost exactly the same as that of the original Moth. So, in spite of the moanings of the pessimists, '' popular aviation'' has advanced a little way. The landing speed figures of these time-dimension-distant machines are practically the same, so the additional performance in the case of the Bibi has not been obtained by the simple expedient of moving the entire speed-range up through a couple of A.S.I, markings. This erstwhile Czech machine (the new international situa tion is not, apparently, likely to interfere with normal de liveries from Prague) is being sold over here by Aircraft and Allied Enterprises. They propose, if they can get their new aerodrome and club plans past the C.A.G. Commissioners and the Council of Associated Light Aeroplane clubs, to use the machine for ab initio training. Whether or not it is suitable for such specialised and strenuous work remains to be seen, but as a private owner's or amateur's aeroplane it has a number of really good points. Easy Ingress Apart from the performance—and the machine genuinely cruises at 105 m.p.h. or more at rather less than the normal revolutions—the side-by-side seater cabin is amply roomy for two large people, and can be entered with, for the type of machine, outstanding ease, through a door on either side; there is plenty of room on a full-width tray behind the seats for luggage of any normal dimensions. The Bibi's characteristics in the air are very good indeed, with light, well-proportioned and really effective controls, and the cruising consumption of fuel should be rather less than three gallons an hour. Further more, the machine is sold with very reasonably full equip ment. This equipment includes wheel brakes, a vertical- reading compass, and a built-in fire extinguisher. For the available power, the take-off, even with two people and luggage aboard, is very good indeed, though the machine which I flew had an airscrew which was, if anything, on the coarse side. The initial climb is in the region of 600 ft./min., or a little less. In smooth air it is almost entirely stable and can be flown for quite extended periods hands and feet off. As usual, none but short course-correction turns can be made on the rudder alone, but the machine can be flown indefinitely on the ailerons. Although split flaps are fitted, these are not of very adequate area and the approach is still somewhat flat and, consequently, a little difficult to judge. Minor height adjustments can be made by means of crab sideslip, though in anything resembling a steep slip the speed cannot be kept down to a reasonable figure by means of top rudder. The flaps are directly operated from a three-position-lever on the pilot's left, and the "half" and "full" flap positions can safely be used to stretch the glide or otherwise, since, when the flaps are raised to the "half" position, there is no marked decrease in lift. The effect of lowering the flaps is to make the machine slightly tail heavy and it is necessary to use a touch of trimming control movement. This trimming lever is conveniently placed and the range of the tab movement is covered in a short and more or less identical angular dis placement of the control. In the ordinary way this hardly requires to be touched except when settling down to cruising attitude. For instructional work one would say that both the elevator and the rudder controls are over-light and sensitive at low speeds, and that it is too easy to over-correct during the last phase of the approach. The necessity for accurate fore-and-aft control while holding off, is, however, compensated for by the fact that more or less any kind of landing at any speed below 50 m.p.h. is safe and final, provided that the control is not pulled sharply back. If it is held more or less neutral when making a level "wheeler," the machine will stay com fortably on the ground. At the full control position there is just enough elevator and not too much for a good three-pointer —w hich is as it should be. Knowing nothing of its test history, I did not attempt any stalling experiments to the extent of pre cipitating a possible spin. A gentle stall, Cleanly conventional in the modern manner, the Bibi has no unnecessary pro tuberances — hence the performance.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
