FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1983
1983 - 0652.PDF
The first order came from the Govern ment of Ontario, for two aircratt for its NorOntair consortium of small airlines—the first time DHC had received a Government order at such an early stage in a project's life. First production Dash 8s for NorOntair will be delivered in July 1984—slightly after the SF.340, which goes into service next April. Total Dash 8 sales now stand at 45. with 74 options. In deciding to build a new aircraft in the 36-seat class, DHC thought of taking the easv route and scaling down the Dash 7, losing two engines on tne wav. The result, says Sandford. would not have been the "best aircratt for the job. Scaling down inevitably leads to an overweight deriva tive while ;he excellent siiort field performance oi tne Dash 7 whicn carries a weight penalty inherent in its soph isticated Stol equipment was not a Dash e design ariver. So the Dasn 8 is a new design. Althougn it retains a lot of structural commonality with its forebear, it is different in several important aspects. Most of the changes relate to the higher cruising speea of the new aircraft, now set at 270kt instead of 230kt. The nose is much more stream lined, with curved, fixed side windows, while the fuseiage is slimmer by four inches. Because of the new engine instal lation, nacelles are longer and more streamlined, reducing drag, and higher aspect ratio supercritical wings are usea. Many lesser features, such as the faired-in undercarriage legs, help ail-round ef ficiency. Another .-hange. which will appeal to militarv anu freight-handling customers, is the fitment oi a large cargo door as standard in the rear fuselage. 'Hie Dash 8 had to be last. On rhe LOO n.m. sectors at which it should excei. it will be competing fin the USA at least) for commuters wno might prefer to drive themselves from point-to-point rather than trom airport-to-airport. Encouraging businessmen to leave their cars at the 1006 airport and fly demanded an aircraft capable of fast, punctual service, with minimum time-to-height and the ability to dron quickly into a landing slot after the cruise. DHC reckons that the Dash 8's 100 n.m. sector time will be a little over 32min, so it should be competitive with 55 m.p.h. drivers—even with time allowed for car parking, passage through the airport, and possible air traffic control difficulties. The Dash 8 can fly four 100 n.m. sectors or one 600 n.m. stage fully loaded without refuelling, with 1FR reserves constituting a 100 n.m. diversion plus 45min at 6,000ft, The 1FR estimate is ''conservative', savs DHC. The Dash 8 will complete a 200 n.m. stage in 56min. On a sector such as this. DHC claims that its 36-seater will have a 39 per cent advantage over current turbonron commuters in terms of avail able seat miles per gallon. The choice of engine and propeller combination was fundamental to Dash 8 competitiveness. The same is true of the other commuters, and to meet the demand Pratt & Whitney (Canada) and General Electric have Oeen offering their latest <~urboprops, one an all-new design, the other based on an existing, and very successful, core. According to John Sandford, the two engines were very ciose on both price and guarantees, but for the Dash 8 the choice was driven by the need for enough power to lift 36 passengers and full fuel off the ground in under 3,000ft. The power is also needed to enable the kind of hot and high performance that is an important Dash 8 selling point. So GE's 1.650 s.h.p. CT7-5. which might have won the competition on grounds of maturity, lost the battle to the PW120. which is a bigger engine ,ated at 1,800 s.h.p. for laKe-off. Two PW120s will give the Dash 8 a 3.800ft take-off at ISA+30°C, while at ISA4- 10°C the commuter will be able to fly from a 6,000ft-high runway after a 4.000ft take-off run. Engine-out performance is taken care of by a 2,000 s.h.p. automatic power reserve rating. To match the new engine, a propeller made by Hamilton Standard was chosen. Cynical observers may note that Hamilton Standard, like Pratt & Whitney, are both subsidiaries of United Technologies. But DHC is at pains to point out that the | parent company has had no influence on j equipment choices, and that eacn decision has been made entirely on its merits. | Hamilton Standard's competitor was Dowty, the principal difference between the two products being that Dowty's propeller is constructed entirely from composite materials, while Hamilton Standard's uses composites built up around an aluminium spar shell. Dowty's propeller was chosen lor the SF.340. The Hamilton Standard blade is more mature, with five million hours service and 5,000 blades produced to date. Dash 8's high wing allows a 13ft diameter disc, so the propellers will spin at a relatively slow, and hence quiet, 1,200 r.p.m. The Dash 7's lift diameter propeller turns at about 1,300 r.p.m., although DHC reckons that the external noise of both aircraft will be very similar, and "appreciably less" than specified by FAR Stage 3 limits. Avionics on the Dash 8 can be tailored to suit the customer. Standard in the commuter version is Sperry's custom- designed DFZ-800 automatic flight control system. This takes its inputs from j the same company s new attitude and I heading reference system ana two digital I air data computers which provide altitude j airspeed, and temperature information. I The DFZ-800 is "fail active/fail passive,'' j meaning that the svstem remains fully . operational on its second channel if chan- j nei 1 fails, any further failures causing it to drop off the line altogether. Sperry also supplies the Primus 800 eoiour radar, which looks at weather system size and density up to 300 miles away. Standard Navcom fit was originally the Collins Pro-Line 1 analogue system, but this has now been discarded in favour of the digital Pro-Line 2. This system competes directly with King s Gold Crown 3. leading DHC to re-open the Navcom competition. DHC says that the decision on which system will be standard will be announced before the Paris Air Show. Customers will still, of course, have the option oi fitting the system of their choice, but de Havillana notes that most remain with the supplier originally specified. Offered as an option on the commuter and as stanaaro on the corporate Dash 8 is Sperry's electronic flight instrument system (Efis), in which cathode ray tubes replace the electromechanical ADI and HSI. Asked why Efis, which allows more information to be displayed to the pilot more reliably, is not original equipment on the commuter, DHC replies that it FLIGHT International, 9 April 1983
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
