FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1956
1956 - 0354.PDF
354 FLIGHT, 30 March 1956 PROVING THE BRITANNIA . . . ability that the Rolls-Royce Dart has foreshadowed for propeller-turbine engines. During the 250 hours of route-proving flying there was one engine failure, but this was due entirely to com-pletely unorthodox use of the engine during test work; apart from this incident there was literally no other engine trouble whatever.The reduction gears were modified from spur to double-helical tooth-form some 18 months ago, and the new gears have now given10,000 trouble-free engine-hours in flight. The monotonous ease with which these engines will start upor relight ki hot weather or cold, at sea level or at altitude, breeds confidence; but the most impressive feature, at least to a pilot newto turbines, is the power available at "continuous" rating. The old idea of a "maximum diving speed" is, of course, defunct forturbine-powered aircraft. The Britannia can, in fact, exceed its Vn<> ("never-exceed speed") in level flight with cruising power ataltitudes up to 11,000ft; similarly, on any two engines, it can reach its maximum operating speed of 234 knots i.a.s. at approximately3,000ft. Because of this power the three-engined and four-engined pro-cedures for approach, overshoot and landing are practically identi- cal except that on four engines it is inconvenient to use full powerfor an overshoot. In practice this has the advantage that trainees can progress straight to three-engined practice without spendingmuch, if any, time on four-engined approaches. Because an operator does not want to go to the expense of layingdown spare engines at numerous overseas stations, the three- engined ferry performance of a civil aircraft is of vital importance.The Britannia can, as an example, take off on three engines from Khartoum (1,250ft elevation) in the morning during the hotweather and fly to Entebbe, carrying normal diversionary and reserve fuel. If, during take-off, a second engine should fail andthe undercarriage remain down, it would be possible for the air- craft to climb to 1,500ft above the aerodrome level, do a circuit,and land again. If the electrical system of the Britannia appears complex atfirst sight, the operation of it is not. Following modern practice the generation is A.C. from four engine-driven alternators [in theBritannia 100.—Ed.], the total output of 130 kVA being enough, in layman's language, to supply three miles of sodium street-light-ing or 50 houses. The failure of one alternator still leaves enough supply available for all electrical services. The failure of twoalternators does not affect the technical operation of the aircraft, except for the loss of a small amount of the tail de-icing system.If, by great misfortune, only one alternator should be left economies have to be effected, but all services essential to the safe operationof the aircraft can be maintained. As the alternators are not of the self-exciting variety, an emerg-ency battery is maintained to re-excite them in the unlikely event of a serious earth on a busbar. One of the more-pleasing demonstra-tions is to isolate all batteries and switch off all alternators, and fly around for a while with no electrics on the aircraft at all,subsequently restoring generation by means of the emergency battery. The operation of the electrics is made simple by thediagrammatical layout of the control panels and by the use of transfer switches in the event of failure of alternators or inverters.These switches transfer or shed load in a manner appropriate to the failure, and magnetic indicators on the panal clearly indicatewhich circuits have been made and which broken. How not to conduct an airliner—but how nice to know how safe: A take- off with the "pole" held fully back from the start of the run. (Picture from a cine record.) (Below) 53A inches of ice on the elevator horn balance made no difference to the Britannia's controls, from 180 knots down to the stall. A word might be said about the bogie undercarriage of theBritannia. It must be admitted that a bogie doubles the number of bumps on a bad runway, and (naming no names) there are quitea few of the latter in the eastern hemisphere. But this is a small price to pay for the safety that multiple wheels provide, thebraking effect that can be achieved with eight wheels all fitted with Maxaret non-skid units, and the low runway loading factor sonecessary in aircraft that only encounter acres of perfect concrete once on each round trip. The load concentration for the Britanniais, in fact, lower than that for either the Stratocruiser or the Super Constellation—and, of course, considerably lower than that forthe DC-7C. The fuel system is simplicity itself; four tanks supply the fourengines and, for flights where no more than ten hours' fuel is carried, the operating drill is to switch on the pumps and cocksat the beginning of the flight and switch them off at the end. Where more fuel than this is carried a certain amount of cross-feedinghas to be carried out. There are various philosophies behind the arrangements em-ployed on different aircraft of controls to deal with an engine fire. On the Britannia the essential controls for each engine are in a row,in the correct order, on a roof panel accessible to both pilots. When the fire bell rings, a red warning light appears in the featheringbutton and another, at the bottom of the row of fire switches, clearly indicates the appropriate H.P. cock, L.P. cock, oil cock,fire-door switch and first- and second-shot fire extinguishers. Incidentally, the feathering takes only two seconds. Taken all round, the Britannia will be operating to higher per-formance standards for take-off and landing than any other civil aircraft with a British Flight Manual and, what is more, it canoperate at its maximum all-up weight at hotter and higher aero- dromes. As an example, we shall be able to use the maximuma.u.w. out of Johannesburg except during the very hottest hours of the summer days. A most impressive piece of performance wasan accelerate/stop carried out on the main 10,000ft runway at Jan Smuts at an a.u.w. of 150,000 lb; the aircraft was accelerated to120 kt and then the H.P. cock on No. 4 engine was closed; the other three engines were then put into reverse and full wheel-brakes applied. When the aircraft came to rest there was still half a mile of runway left. There have been many high-lights like this in the last two yearsof association with the Britannia; one in particular that comes to mind was the 10 hr 50 min direct flight from Khartoum to Filton,2,730 nautical miles, against an average headwind component of 60 kt all the way. There is one feature, however, that has won thehearts of all her pilots in no uncertain manner—and that is the search radar. There have been many improvements in aircraftand in associated facilities over the years—such as feathering air- screws, high-lift flaps, instrument landing systems and approach-lighting and two-mile runways, but all these things have barely kept pace with the increased size, wing loading and approachspeeds of present-day aircraft. Judged by weather minima (coupled landings apart) the pilot has gained nothing and we are back towhere we were 20 years ago when aircraft came in at 65 m.p.h. on "series QDMs". In search radar the pilot really gets something, all for himself,with no strings attached. Its secondary use for map painting is a great comfort when beacons are scarce (Nairobi to Johannesburg)or when the A.D.F. is pointing to the nearest thunderstorm, and on some sections of a route, such as from Dijon to Caraffa, itgives a continuous indication of position. It is on a filthy black night, however, with solid medium cloud and embedded cumulo-nimbus, that it becomes the pilot's best friend. As each fresh horror comes up on the tube he makes a small adjustment to the autopilot,takes another sip of coffee and thinks what hell it must be for the people on the ground. Surely, as a colleague remarked, the greatestthing for stomach acid since bicarbonate of soda. Editorial footnote: The following are the manufacturers of some ofthe items mentioned by Capt. Rendall. Airframe—Bristol Aircraft (assisted by Short and Blackburn); engines—Bristol Aero-Engines; air-screws—de Havilland Propellers; undercarriage—British Messier; brakes and "Maxaret"—Dunlop; search radar—Ekco; de-icing—Bristol and Napier.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
