Cessna’s pressurized Skymaster has a number of STCs developed by Jack Riley, of Riley Rocket fame. Cessna Flyer recently talked to Skymaster authority Bill Crews to get a brief history of the various P337 conversions.
Entrepreneur, innovator and master salesman Jack M. Riley came to the airplane business only after retiring from his first career in blueprinting. By 1962, Riley had been assigned the patent for an Engine Supercharging Apparatus, and it would prove to be one of his most important contributions to General Aviation.
“Jack Riley called me around 1988, maybe ’89,” recalled Bill Crews, owner of Skymasters International. “He did conversions for all kinds of different aircraft, and he was looking for a Skymaster.”
The turbocharged engines on the P337s were known to run hot. “His first mod [for the 337] was an engine intercooler system, and he needed an aircraft to test it on,” Crews explained, “so he bought an airplane from me. It was a P337 with 225 hp.”
Riley’s testing worked, and he was able to secure his intercooler STC for the P337. Riley soon began doing partial conversions to P337s at his California facility.
The Skyrocket is born
Never satisfied, Jack Riley was back on the phone to Crews. “He was getting tired of doing partial conversions installing his intercooler modification and a STOL kit and wanted a total conversion,” he explained.
“I helped him with finding derelict aircraft—by derelict, I mean they had low total time, all logs, zero corrosion and no damage history—but he didn’t care about engine times, paint and interior, because he stripped them to the fuselage, starting over.”
For the P337 conversions Riley International was creating, Jack Riley added the same Horton STOL kit as he used on the Riley Rocket conversion for P210s, and also came up with a metal panel. “The original plastic overlay would vibrate because it never seemed to fasten on correctly,” Crews said.
“A metal panel is so much nicer because the instruments are actually attached. Everybody hated that plastic panel, but Riley was the first one to do away with it. It was a great upgrade.”
“One very big thing he did was soundproofing all of his aircraft,” said Crews. He also upgraded the radios to state-of-the-art and put in an S-TEC 65 autopilot. “After a couple of years he came up with pressurized mags and [an] inflatable door seal,” Crews explained.
Riley marketed his creation as the Skyrocket. The paint scheme for these 337s was the same as what Riley was doing on the P210 Riley Rockets. “But he still didn’t have the air conditioning that customers wanted,” Crews pointed out.
“One customer did come [to see Jack] and he had developed his own air conditioning system for his personal P337,” said Crews. “Jack and the customer worked out a deal: if Jack would do certain mods on the customer’s airplane, they could work out a deal on this owner’s air conditioning design.”
“Jack then went about getting the STC for the air conditioning system, which he added to his future Rocket conversions,” said Crews.
“So, I’d sell these P337s to Jack, and Jack was turning these things out. We sold about 20 to 25 over two or three years. Pricing started at $225,000 in 1989ish, then up to $250,000, then $275,000.”
“The last one he sold with the 225 hp engines was in 1993 or 1994 I believe, and the cost was $425,000 or more,” Crews said.
The Super Skyrocket
“Then Jack Riley called me one day—he had himself a turbo 310 hp Skymaster, not pressurized, which he had bought at a government auction for $50,000. Only Jack Riley could get a deal like that,” Crews joked.
He then added, “I’m surprised he didn’t talk them in to giving it to him!”
“I can’t say what the previous owner was using it for, but it seems he was hauling something the U.S. government wasn’t happy with him hauling,” he said. This aircraft was Riley’s test bed for the 310 hp Riley Super Rocket.
“Riley got that 310 hp conversion approved, and started doing the Super Skyrocket in about 1994, ’95,”said Crews. There were over 300 changes in the Super Skyrocket, according to Gene Smith in “The Faster Mixmaster,” published in US Aviator in April 1994.
The Super Skyrocket was the sixth 300 mph aircraft in Riley’s Rocket series. These Cessna P337s were the fastest of them all, with an additional 85 hp per engine, three-blade props, a 2,500 fpm rate of climb—and higher fuel consumption to match.
“He sold 10 or 12 of those, and they were doing pretty good,” Crews said. “Then Jack Riley had a stroke, and then another.” Riley was partially paralyzed and unable to continue working.
“Now, you have to understand, Jack was Riley International; the company stayed open [after its founder became ill] but sales fell off.”
The company declared Chapter 7 bankruptcy in California in 1996, and in 1997, SuperSkyrocket LLC bought all of the STCs. (These Riley STCs are now held by Tim Kasper of Kasper Industries. —Ed.)
“Riley had a real good product, but by the mid- to late 1990s, it was all over,” Crews said.
“The Super Skyrockets are rare; I sold one this year—there are maybe 20 Skyrockets and maybe another 10 Super Skyrockets still flying in the United States. The value has come down quite a bit, as these are now older conversions.”
Riley Rockets today
Bill Crews, along with Hank and Matt Kozub at Aircraft Sales, Inc., have developed a newer P337 conversion product called the Rocket II. “We’re continuing what Riley did,” Crews explained. “We just do the 225 hp engines, and the concept has been 25 years in the making.”
The Rocket II conversion includes two remanufactured Continental TSIO-360-CB engines with a factory warranty plus new engine mounts and engine hose kits as well as overhauled turbochargers, wastegates and turbocharger controllers. The aircraft uses Riley’s intercooler system on both engines and includes pressurized magnetos.
Two freshly overhauled props and governors are installed along with polished spinners. The aircraft has a four-color paint scheme and new stainless steel hardware is used all external fasteners.
Inside, the aircraft offers leather seats, integrated headsets—and the best soundproofing available, the same level of noise reduction that Jack Riley was so fond of.
The avionics package includes a Garmin GMA 340 audio panel with four-place stereo intercom and music input; one Garmin GTN 750 WAAS Nav/Com/GPS and one Garmin GTN 650 WAAS Nav/Com/GPS; as well as a Garmin 345 transponder. It also includes an S-TEC 55X autopilot and an engine monitor in its custom aluminum panel.
“One T337 has been completed with a glass panel, and will probably be the way most new Rocket II conversions will be outfitted,” Crews explained.
It took a lot of hard work by Jack Riley and his associates in order to transform stock Cessna aircraft into customized, high performance personal air transportation.
Today, as far as remade Cessna 337s are concerned, Bill Crews, Hank Kozub, Matt Kozub and others are picking up where Riley left off. But they know they owe a debt to their predecessor.
“Jack Riley was one of those guys in life,” Crews said. “One of those guys you are just glad to have had the privilege of knowing and working with.”
Sources: 337skymaster.org, AOPA.org, CessnaFlyer.org, Skymaster.com, TwinNavion.com.
Special thanks to Bill Crews for his wealth of information and ready assistance, and to Herb R. Harney for posting the following helpful articles on the SOAPA forum: “What’s in a Name?” by Chuck Stewart. Air Progress, January 1996. “Riley Super Skyrocket” by Geza Szurovy. Private Pilot, November 1998. “The Faster Mixmaster” by Gene Smith. US Aviator, April 1994.
P337 CONVERSIONS AND INFORMATION
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