One of the aircraft parked at the NBAA static display at the Las Vegas Convention Center during the NBAA Convention in October was a highly modified Cessna Citation 501SP. The Citation was the first 501SP equipped with the recently certified Sierra Industries G501SP cockpit upgrade, featuring a Garmin G1000 panel and Cobham digital engine displays. Sierra Industries also modified the jet with its Stallion upgrade, replacing the original 2,200-pound-thrust Pratt & Whitney Canada JT15D-1s with 2,300-pound-thrust Williams International FJ44-2As, plus a quick-release radome, pneu-lift baggage door and other modifications.

The Garmin G1000 package replaces the Citation 501 and 501SP’s original mechanical gyroscopes and avionics with a three-display Garmin system driven by dual Garmin GRS77 attitude heading reference systems and dual GDC 74A digital air-data computers. The panel, precision cut using a waterjet, features two 10.4-inch Garmin GDU 1040 primary flight displays flanking a center-mounted GDU 1040 multifunction display, which is mounted just below the Cobham electronic engine instrument displays.

Development of the G501SP STC took two years, from the initial pitch to Garmin to FAA certification, according to Mark Huffstutler, Sierra Industries CEO. Huffstutler estimates that the entire job took about 5,000 man-hours, including about 3,000 hours just to test and conform every step of the installation.

“It is a total remake of the cockpit and nose section of the aircraft involving all of the avionics and instruments,” he told AIN. “Coming out of the aircraft is more than 150 pounds of analog gauges and old wiring. Going back into the aircraft is about 50 pounds of Garmin avionics and new wiring. The G501SP system is unique to this application in that there was a good amount of software written especially for us. You can imagine that installing this system in a pressurized turbine twin operating at 43,000 feet and up to Mach 0.75 presented some unique challenges.”

The base G501SP package also comes with dual Garmin GIA63W 16-watt, 8.33-kHz transceivers, dual GMA 1347 digital audio panels (with marker beacon and intercom), dual GTX 33 transponders, dual GMU 44 magnetometers, GWX 68 weather radar and Sierra autopilot interface and glareshield/annunciator panel. The base package costs $284,000.

The Cobham engine instrument displays are optional, as are standby instruments, Garmin synthetic vision technology, electronic charts, XM WX and radio, pedestal-mounted GCU 477 alphanumeric keypad, Taws A or B and GTX 330 mode-S transponder with traffic information services. Installation time is typically five weeks and can be done at Sierra’s Uvalde, Texas headquarters or by dealers at other locations. “From an installation standpoint,” Huffstutler explained, “it is a beautiful kit that is well within the average avionics shop’s ability to install. Our kit comes with all the wiring harnesses pre-made with as many connectors and terminations already done as possible.”

Sierra Industries has been modifying Citations for the past 30 years and holds more than 300 FAA supplemental type certificates. In November, Sierra was nearing completion of its 58th and 59th Williams engine Citation upgrades.

The Stallion engine upgrade makes the Citation 501 competitive with later models such as the Hawker Beechcraft Premier I/IA and Citation CJ2 and CJ3. With the more powerful Fadec-controlled Williams engines, which are able to deliver more thrust at higher altitudes than the JT15D-1s, the Stallion offers maximum IFR range of 1,230 nm and maximum cruise speed of 402 knots, up from 910 nm and 355 knots for the stock Citation. The Stallion’s max-fuel payload is more than double, 1,670 pounds compared with the unmodified Citation’s 820 pounds.

Huffstutler firmly believes that modifying older Citations is well worth the expense, even given the dramatic drop in value of business jets during the economic downturn. “Where can you find a personal jet with a Garmin 1000 panel, 1,200-nm range, single pilot and eight seats for under $1 million? Add to this the Williams engines and there is no comparison available today at this price.”