Viewing page 277 of 507
This transcription has been completed. Contact us with corrections.
268 HELICOPTER AIR SERVICE PROGRAM APPENDIX M FACT SHEET FOR PT-6 TURBINIZATION OF CHA'S S-58 FLEET GENERAL Following the development of the S-62 as a modernization of the S-55, Sikorsky Aircraft has directed considerable research and investigation in a similar program of modernizing the S-58. Feasibility of such turbinization of the S-58 was proven during installation of two General Electric T-58-6 engines in an S-58 in February 1957. Turbinization of the S-58 has already taken place in the UNited Kingdom, a development completed by Sikorsky's licensee, the Westland Co. This aircraft, known as the WEssex, is in production in two configurations; one with a single Napier Gazelle engine and the second with two de Havilland Gnome engines (T-58 licensee), the former for the Royal Navy and the latter for the Royal Air Force and Royal Australian Navy. In addition, Sud Aviation in France has conducted trials with twin turbine versions of the S-58. In November of 1963, Sikorsky Aircraft and affiliate, United Aircraft of Canada, Litd., met to consider the joint development of an S-58 powered by three PT-6 engines. These engines have been designed by and are in production at UACL. Although some consideration was given to the production of a new aircraft so configured, the major emphasis was to be directed toward a modification program of existing helicopters, particularly in view of the large quantities of S-58 helicopters operating around the world. Today, Sikorsky has manufactured over 1,700 S-58 helicopters which present a sizable market for such a modification. Sikorsky Aircraft has thus far made a number of unofficial proposals to United States and foreign military services. Considerable interest has been generated, particularly within foreign military services and within the branches of U.S. forces which operate the S-58 in conjunction with military assistance programs. Evaluation of this modification program by these military agencies is still in process. While particularly attractive to indigenous and foreign operated military forces, the significantly increased payload and performance led inevitably to consideration of the commercial market. The advantages of the three PT-6 installations which were found to be so attractive to military interests are even more significant in airline operations. Two great airline benefits are inherent in the S-58 turbinization program. one is the long-sought goal of multiengine performance with minimum effect of performance as a result of having to shut down one engine. With a three-engine installation, two-thirds of installed power remains available; two-engine installations afford only one-half of installed power. In sharp contrast with some of the limitations which plague twin-turbine helicopters, the PT-6 powered S-58 would permit category A and vertical operations without payload or site restrictions up to 100° F. Perhaps of even greater importance is the fact that this performance will now truly permit full penetration of the city center with favorable economic and operational factors. The second great benefit is that the PT-6 S-58 as a modern helicopter will have the great economic advantage of already high aircraft and component TBO's with no limit in sight on their continued development. These economics, taken together with the low operating costs of the Pratt & Whitney PT-6 engine, continue to create an ideal VFR-IFR-VSTOL with lower operating cost. The advantages which are particularly important to CHA are briefly summarized as follows: 1. 500-POUND INCREASE IN USEFUL LOAD CHA's current S-58 operating weight (empty) of 8,820 pounds will be reduced by 500 pounds. This of course permits a 500-pound increase in payload with no change in maximum certificated gross. Alternatively, the aircraft could be operated at a 500-pound lower gross weight with the same payload, thereby reducing fuel consumption, increasing cruising speed, and vertical performance. 2. FUEL CONSUMPTION Although the basic fuel consumption at equivalent power outputs of the three PT-6 engine package is slightly greater than that of the R1820, the elimination of the large cooling fan and the hydro mechanical clutch reduces power requirements by over 100 hp so that the resulting fuel consumption at a 95-knot cruising
