Page 36 - Volume 20 No. 6

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Because N503CC is not certified for RVSM (reduced vertical separation minimums), the airplane is currently restricted to FL280 instead of its original 35,000-foot operating limit. Therefore, comfortable endurance is limited to about 2.5 hours. However, 28,000 feet is very near the early Citation’s best-speed altitude, and Fisher says it’ll climb up there quickly at 2,000 fpm or more and run dependably at 340 knots, burning 150 gallons of Jet-A per hour.
Maximum usable fuel is 536 gallons (3,600 pounds), and with an aircraft empty weight of about 7,000 pounds, an early Citation would have been short of payload with full tanks in its original as-certified configuration. However, a steady progression of gross weight increases added utility to the Citation 500s, and by serial #303 the ramp weight was up to 12,000 pounds. These factory increases have been retrofitted to most early C-500s, via upgrades or STC.
Other than the King EFIS 50 panel on the left side, installed as part of a Silver Crown avionics upgrade in 1998, most of the vintage Citation cockpit remains intact, including the vertical-readout engine gauges. A reliable KLN90B GPS provides space-based navigation output, and the KFC325 digital flight control system is a far cry from the original Bendix FGS-70 flight director and autopilot of 45 years ago.
N503CC’s only significant modification was Sierra Industries’ Longwing mod, which adds three feet to the wingspan, much as Cessna did at serial #350; Sierra also holds an STC to increase the C-500’s takeoff weight to 12,500 pounds, greatly enhancing utility at very little cost. Sierra Industries, of course, is well known for its work in adding performance and value to the original Citation airframe, including retrofit with Williams FJ-44 high-efficiency fanjets.
The Longwing mod enhances the wing’s aspect ratio to 8.5: 1, improving climb, cutting drag and further reducing the Citation’s already-minimal runway length requirements. Fisher says he routinely operates at 3,500- foot runways, and he has used strips as short as 3,000 feet. As a Part 25 certificated airplane, a balanced- field length must be calculated and observed for each takeoff. However, the reference speeds are similar to the operating numbers for light twins, in the 100-knot range. Thrust reversers are not worth their weight for these slow-landing airplanes, their chief value coming on contaminated runways.
With only 3,500 hours on the airframe, and over 1,000 hours remaining on the engines’ TBO, N503CC is still a relative youngster, despite its chronological age. More importantly, it’s a benchmark airplane, a significant indicator of the correctness of Dwane Wallace’s vision, bringing jets to towns and companies of every size. It still has a lot of life left in it.
34 • TWIN & TURBINE
JUNE 2016