iscover
The 250 turboprop is basically the same engine as the turboshaft model used In helicopters. A reduction gearbox has been added to lower the turbine output shaft speed to usable propeller rpm, suitable for fixed-wing aircraft. Operation is similar to the turboshaft, also. Air enters the compressor and Is compressed to over six times atmospheric pressure. This air is discharged rearward through twin air transfer tubes into the combustion chamber where it is used in the combustion of fuel. The resulting hot gases (expanded compressed air) then pass forward at high velocity through four turbine stages. The first two stages of the turbine receive power from these expanding gases and drive the compressor, while the remaining energy is extracted by the free power turbine which drives the propeller"through a system of reduction gearboxes. The exhaust gases are released through twin ducts. As in the turboshaft engine, the 250 turboprop can operate at essentially a constant speed, or the propeller speed can be varied by a condition lever to give optimum performance at reduced noise level. Variations in aircraft power are obtained by varying the pitch of the propeller blades.
Clubair’s Mini Airliner
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MIKE CLAYTON investigates the one airline in Australia that is using the Nomad in regular commuter service and finds that results are so good that more are to be ordered.
As a commercial aviation enthusiast, rather than as a technocrat, the opportunity to report on the GAF Nomad airliner was taken to be a most interesting assignment. And the end result is pleasing. The airliner is proving itself to be very worthwhile.
But back to basics. The GAF Nomad aircraft, now available in two primary versions – the N22 series aircraft with 14 seats or the extended fuselage variant – the N24B has been with us for some time. It is used overseas with commercial operators, military and medical authorities, while at home it is primarily employed with the two latter services. Only relatively recently has the airliner been purchased for third-level use. Currently, as an airliner, the aircraft is operated in Papua New Guinea, the South Pacific, in South America and now, in Europe. The first home-based commercial order didn’t eventuate until April 1978 after several test evaluations with various operators.
Clubair Pty Ltd of Maitland in NSW (operating from Maitland’s Rutherford Airport) was then running three return services per day into Sydney with a Cessna 402 (VHFTR). Within two months of their commencement, it was necessary to increase the weekday flight frequency up to four return flights a day for a regular 10 to 12 per cent growth. Yet the service had been started only as recently as October 1976. Thus, early in 1978, Mr Grahame Swanson, the owner and chief pilot of Clubair, commenced an aircraft replacement evaluation project. Every possible aircraft type was investigated. Some very thoroughly indeed for the paperwork figures had seemed impressive. Now, as the ultimate choice aircraft was being purchased for a specific role, no compromises were to be made.
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