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Aviation History
1988
1988 - 3698.PDF
decision to move onboard equipment or to install ballast. The CL-215 was never designed to be the ultimate triumph of power over weight and drag; nevertheless, Canadair elected to move equipment rather than add dead weight to restore e.g. flexibility. The solution was to move the main elec trical distribution centre (MDC) well forward from its position immediately aft of the left- hand landing-gear support structure. Because the MDC was not intended to be moved, some redesign was necessary. At this point Canadair bit the bullet and modified electrical distribution to meet FAR 25 with a split busbar system. The MDC is now located immediately behind the crew compartment bulkhead on the starboard side. As a result the e.g. was restored and 2,0001b saved. Canadair has used the saving to increase water-tank capacity, and to intro duce a 1,5001b foam-generation kit. From Ship 1056, CL-215 structure had been modified to cater for the extra weight which was expected to be carried following the projected introduction of long-term powder retardants. Modifications included increasing the thickness of stringers on top and bottom wing skins between the root and the engine on each side. There is little provision for access to the area between the wing and the fuselage after initial attach ment, so Canadair wanted to avoid any work in this area on aircraft being retrofitted with turbine power. Structural changes to the wing for retrofit aircraft are all outside the fuselage interface region. Local areas of upper wing skin are thicker, and both front and rear spars are beefed-up locally. The wings for new CL-215Ts include these changes from scratch, and the wing attachment is essentially unchanged on new-build aircraft. Original aircraft from the first production batches—Series 1 and 2, and the first five in Series 3—will need alternative modification if they are to use turbine power, and will operate at lower weights. Powered ailerons, previously developed by Aerospatiale for French CL-215s, are to be fitted to all turboprop aircraft. Canadair says that the control forces on piston-powered aircraft were unbalanced, with light elevators and heavy ailerons, even with large control- stick movement available. Powered ailerons will be an option on retrofit aircraft, after being introduced on the second prototype CL-215 (Ship 1114). A major change involves the water- dropping system, CL-215's raison d'etre. New aircraft will have a sequenced four-door dropping system, a foam-generation system, greater water capacity, and higher after- scoop weight. Canadair claims that the new main system permits the dropping of "salvoes" of water in a long line or in a deluge. New aircraft will also have air-conditioned cockpits. By definition, most water-bombing operations take place in hot regions, in the The Canadair's CL-215T's PW123AF turboprops are inboard and aft of the previous piston location heat of the day, and in the hottest part of the sky—above the flames. This will also be a standard fit for retrofit aircraft, although launch customer Quebec decided to do with out it. Fuel system changes include the intro duction of pressure refuelling, and the adoption of product improvements since the original design. The CL-215 windscreen meets dual-pilot requirements, and a heated unit is being developed for public-transport applications. Canadair claims that it has had no struc tural problems with the original design in 20 years of operations. It says that normal fire operations have involved lyhr operations each involving as many as 20 scoops. The manufacturer regards each water scoop run as equivalent to a conventional take-off or landing, even going so far as to suggest that this represents the most strenuous operation, exceeded only by aircraft-carrier operations. The introduction of the turboprop engine means that Canadair has to provide rotor- burst protection, the greatest concern being aileron-control cables which run through the cabin-roof structure. A titanium deflection shield has been mounted on the outside of the fuselage, immediately forward of the wing. Initially, Canadair had been content to maintain CL-215 power ratings, if only to minimise other changes in its quest for low- risk, low-cost development, but the company soon realised that utilising the full power available from the PW123 would increase the potential of the CL-215T. The new 2,380 s.h.p. engines provide a better rate of climb, a major consideration for an aircraft scooping water and dropping fire retardant in hilly country, often at high weights. Raising the power meant looking more closely at the aircraft's handling, says Rhodes. The single-engine case was critical, because lateral stability was thought to be insufficient at higher power ratings. The most cost-effective solution was to adopt endplates, or what Canadair insists on calling winglets. (Not that it claims any enhanced thrust, or drag reduction. The dictionary just said that this was the name for any wingtip- mounted fin structure.) The laws of cause and effect continued to apply, and Canadair then had to re-evaluate the whole wing structure because it was using a lighter engine and had introduced new aerodynamic loads at the wingtip. "A lot of engineering assessment time went into summarising the implications," says Rhodes. The company was acutely aware that the wing had to work with a higher, 46,0001b after-scooping weight, compared with the earlier 43,5001b maximum. The maximum take-off weight has grown from 43,5001b to 43,8501b. The nacelle for the new Pratt & Whitney PW123AF engines is essentially that devel oped by Boeing Canada for the Dash 8-300 commuter, which uses very similar engines. The interface for the engine, which had been underslung on the Dash 8, unlike the CL- 215T's overwing exhaust system required the oil cooler to be moved. Canadair sees a market for 11 new aircraft a year through to the end of the century, and an additional 50 retrofit kits. Sales of 50 air craft and 50 kits are expected to be sufficient to cover non-recurring costs. The three-year development programme will cost about C$50 million. In the 1988 fiscal year Cana dair parent company Bombardier allocated C$30 million to CL-215T development. The Canadian province of Quebec has a requirement for 19 CL-215s to be retrofitted with turboprops (including some from the latest batch of Series 5 machines). At least ten of the planned 125 CL-215s remain unsold, with the last due for completion late in 1989. Ships 1114 and 1115 are being used as CL-215T prototypes for flight testing and certification before being delivered. Canadair says that it is in final negotiation with three "established customers" for the last CL-215s. The first international 24 FLIGHT INTERNATIONAL, 24/31 December 1988
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