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Aviation History
1959
1959 - 0397.PDF
194 FLIGHT, 6 February 1959 Dart Overhaul by B.E.A. PILOT SCHEME AT L.A.P. ENGINEERING BASE NEW facilities for the complete overhaul and testing ofRolls-Royce Dart turboprops have recently been broughtinto use by British European Airways at London Airport at a cost of about £300,000. This is the first time that a U.K.airline has undertaken the complete overhaul of this type of engine. At present B.E.A. are carrying out this work on Dart 506son an experimental scale in an engine overhaul and test shop forming part of the existing engineering base. On completionof the new engineering hangars and shops now under construc- tion, more extensive overhaul facilities and two additional testplants will be installed there, and Dart 510s and 520s will also be handled. Dart overhaul by the Corporation means the elimination ofthe time and cost of road transit of engines to Rolls-Royce at Derby, and a considerable reduction in the number of spareengines required by B.E.A. With more than 250 Darts in service, the airline now claims to have more gas turbines in use than anyother civil operator. Under the new scheme, engines coming out of service arereceived at the engineering base, where they are reduced to their sub-assemblies which are in turn dismantled. The special toolsrequired for this work are mounted on panels close to the indi- vidual operations, and dismantled parts are then passed on to thecleaning bay. Most of the machines in the salvage or re-work section areof general-purpose type, but in some cases are fitted with special fixtures and equipment. Stands of special design are used fordismantling and re-building of engines to and from their sub- assemblies. These are provided with power rotation about thelateral axis and can be manually rotated about the longitudinal axis. This affords maximum accessibility and enables the engineersto position the work comfortably for their purposes. When the overhauled engines are completely assembled theyare subjected to a rigorous test schedule. To save space the engine test plant has been placed in an underground cell andcare has been taken to ensure that the minimum of time is needed to change from one engine to another. The method adopted by B.E.A. in collaboration with Heenanand Froude Ltd. of Worcester, who designed, built and installed the test plant, has been to provide two engine carts, one of whichmay be in use on the test bed while the other is in the overhaul shop above having an engine fitted to it. By this means thenecessary electrical harness, piping, adaptors and the like can be fitted to an engine before it enters the test cell, and while theplant below is testing another engine. Outrigger guides are provided on the test-cart sling to protectthe engine from damage during descent to the test chamber. A sliding door, motorized to open and close horizontally, covers The engine test cell with Dart 506 installed. From the left are (1) Heenan dynamometer, (2) cardan shaft guard tube, (3) engine test cart and base plate, and (4) accessory trolley carrying extension exhaust pipe and Froude water brake the entrance to the cell, and sound-proofing has been achieved bylowering the door on to thick felt pads. The underground installation is divided into two compartments;the single test cell and the control room. When the engine cart is lowered into position it is automatically located by dowels,the pipe connections on the cart automatically engaging with matching self-sealing connections on the base plate. All pipeconnections for oil, water /methanol and fuel are thus made instantaneously and without effort. After the engine cart is locked in position the Dart propellershaft is coupled to a tubular cardan shaft, connecting it to a Heenan-Dynamatic Mk 6 CA dynamometer capable of absorbingand measuring up to 2,500 b.h.p. The necessary loading of the accessory drive of the engine is achieved by means of a smallFroude hydraulic dynamometer carried on an accessory trolley. A good view of the test bed is obtained through the observationwindow of the control room, and observation of the far side of the engine is by means of a large mirror mounted on the remotewall of the cell. The engine's fuel consumption can be read from gauges sitedbehind glass, but no fuel pipes run through the control room. Safety precautions are good throughout the plant: exhaust gasesare taken through a sound-proofed uptake to the roof of the build- ing and discharged to atmosphere, and electro-pneumatic ramsare provided to operate the shutters of the main air intake as a fire precaution measure, in addition to carbon-dioxide and water sprayequipment. The floor trenches are continuously scavenged to remove fumes by means of ducting and a separate fan. Thisextraction system is interlocked to prevent fuel being supplied for testing until scavenging has been operating for 20 min froma shut-down condition. The main fuel tanks are located outside the building. A considerable number of engines have already passed throughB.E.A.'s Dart overhaul shop. The two Heenan and Froude test beds to be incorporated in the new extension to the engineeringbase will be situated above-ground. In addition to testing Darts, these beds will also be capable of testing B.E.A.'s Tynes. „ Control room of the Heenan and Froude underground test plant. A mirror in the cell permits observation of the far side of the engine The sub-assembly bays in the overhaul shop a/e each equipped for a particular series of operations. Note racks and mobile stands
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