Citation IIs Sierra Style

With its FJ44 re-engining programs for the Citation 550 and S550, Sierra Industries transforms some great old airplanes into brand-new stars.

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Sierra Citation Super II

Uvalde, Texas, seems like a strange place for a world-class business jet re-engining company to call home. Located 70 miles west of San Antonio in a part of Texas better known for deer hunting and off-road racing than for high technology, Sierra Industries is way off the beaten path, unless you fly a bizjet, that is.

It was through an improbable chain of events almost 30 years ago that Sierra founder and president Mark Huffstutler found himself in Uvalde running an FBO. And then, almost before he knew it, he was the man behind a series of ever more ambitious aviation ventures, including a full-service maintenance hangar and a busy mod shop. Starting in 1986, Sierra acquired the rights to several modifications packages, including the Citation Eagle and Longwing mods, the well-known lineup of Robertson STOL modifications, and the mods owned by the Dee Howard company, in nearby San Antonio.

Before long, Sierra found itself as one of the handful of companies in the world that specialize in breathing new life into older jets in large part by putting new technology engines on them.

Sometimes it's easy to get lost in the details of a mod package by focusing not on what a program does for the airplane but on how it does it. The end result can't happen without the little details getting taken care of, but what most customers are looking for is the bottom line.

And with the Sierra Citation Super II and Super S-II, those bottom lines are very impressive.

Sierra's Mission: Find New Homes for the Williams FJ44

While Sierra Industries today owns more than 300 STCs, many of them for Cessna Citations, it is safe to say that it wouldn't be the same company without the Williams FJ44 turbofan engine. Developed in the late 1980s as a 1,900-pound thrust engine for the original CitationJet, the Williams powerplant has since gone through numerous growth cycles, each one engendering at least one new and improved Citation along the way. (The Beech Premier I uses FJ44s, as well.)

Sierra's first engine replacement program was for the Citation I. The Eagle 400 swapped out the original Pratt & Whitney JT-15D-1 engines of the 500 with the JT-15D-4 model used in the original Citation II. The airplane also got an increase in max takeoff weight to 12,500 lbs, and the boost in power from 2,200 pounds of thrust per side to 2,500 pounds gave the Eagle 400 much improved climb and cruise speed performance, compared with the stock Citation I.

But it was the introduction of the Williams FJ44 turbofan engine in the 1990s that gave Sierra a launching pad for new programs. The first FJ44 program, the FJ44 Eagle II, certified in 2002, put FJ44-2A engines in the Citation I, making a whole new airplane out of it, with far greater fuel efficiency and impressive performance improvements across the board. Sierra's Stallion mod, which puts FJ44s on a modified Longwing Citation 500 or a 501, was introduced in 2006. In all, Sierra has re-engined nearly 50 Citation I aircraft.

Citation IIs Take Off

Sierra has two programs for Citation II airplanes, both of which offer spectacular performance improvements over the originals.

For those of you who aren't familiar with Citation genealogy, the Citation II was a larger follow-on to the original Citation. Introduced in 1978, the Citation II featured a larger cabin and more powerful engines. The S-II model came about in the mid-80s and for a time took the place of the II -- it's a complicated family tree. On the same fuselage as the II, the S-II featured a new wing and improved Pratt engines.

Those early Citations are remarkably durable airplanes. Sierra has done engine swaps and full refurbs on Citations with more than 10,000 hours on the airframe, and the fleet leader, they told me, has around 25,000 hours and is still going strong. They are very solidly built.

People who don't know the airplanes assume that the Citation II is a relatively small airplane; it's not. With 10 passenger seats and an impressive range, even unmodified, the II and the S-II are substantial and capable business aircraft.

They are even more so after Sierra gets done with them.

The centerpiece of the Citation II engine replacement programs is the Williams FJ44-3A. The engines, as installed in the Sierra Citation Super II and Super S-II, produce 2,820 pounds of thrust each, compared to 2,500 pounds per side for the Pratt & Whitney JT15 engines on the original airplanes.

At an approximate cost of $1.9 million, when you trade in the airplane's serviceable JT15s, the engine swap isn't cheap.

But it does bring big benefits. In addition to being more powerful than the original Pratt & Whitney engines on the original Citation II models, the FJ44-3As feature dual-channel full authority digital engine control (fadec). The fadec makes the pilot's job easier while eliminating the need for thrust reversers. Because the residual thrust with the fadec engines is so much lower, by several hundred pounds in fact, there is no need for reverse thrust for braking. This saves weight, complexity and cost.

The fuel efficiency is another benefit both in terms of cost and utility. Both Sierra airplanes have substantially better range than the originals, thanks to higher cruise speeds and more efficient engine design. According to Sierra's numbers, the Super II has an NBAA range of 1,775 nm, a 397 nm improvement over the Citation II, and its 400 knot max normal cruise speed is 45 knots faster than the unmodified airplane. The Super S-II has an NBAA range of 2,300 nm, which is 461 nm better than the S-II, and its 420-knot typical cruise speed is 35 knots faster than the already fast Citation II's 385-knot figure. With the Sierra mods, max fuel payload is especially noteworthy in the Super II, which has 1,278 pounds of payload compared with just 328 for the Pratt-equipped Citation II. The Super S-II improves on the S-II's 1,036-pound max fuel payload by better than 400 pounds.

The speed and range improvements are striking, but the climb performance upgrade is arguably the most noteworthy benefit that owners will see. As part of the STC, the ceiling on both IIs increases from FL 410 to FL 430, and while both previous airplanes needed to step climb to their maximum altitude, a process that would take well over an hour or substantially longer depending on temperatures, the Super II and Super S-II can get up to 430 with no intermediate stops in right around 25 at max takeoff weight. As you might guess, this is one of the main drivers of the improved range figures, as the airplanes get up to more fuel efficient altitudes much faster, saving fuel and increasing trip speed.

Flying the Super II: An Eye Opener

A short while back Mark Huffstutler and Gary Buchanan from Sierra flew up to Austin in a Super II to pick me up and fly me down to Uvalde so I could see firsthand just what Sierra does and how they do it.

What they mainly do, of course, is make good airplanes better, and my experience in the airplane was an eye-opening introduction to that fact.

For the first flight, Mark was at the controls, and he, like demo pilots the world around, wanted to show me what his airplane could do. We were fairly light, with 2,100 pounds of fuel and roughly 600 pounds of people aboard, for a takeoff weight of 10,374 pounds.

After getting cleared to take off, Mark lined it up and advanced the throttles while holding the brakes. The Super II is a single-pilot airplane, and the addition of fadec makes it without question a better and safer single-pilot airplane. When Huffstutler released the brakes, we rocketed forward. It was quite a spectacular display, and as we departed and climbed out he had to raise the nose to an extremely high deck angle, in order to keep the airspeed at the desired 200 knots. It seemed as though it took no more than 30 seconds to reach our preliminary clearance altitude of 4,000 feet, and Huffstutler had to push the nose hard over to level off. It's not how one would normally fly the airplane, but it made the point. There is performance to spare. We were, in fact, seeing a rate of climb of around 5,000 fpm. Single-engine climb is better than 1,700 fpm at max takeoff weight.

As usual, we didn't get a direct climb to FL 430, but factoring out the brief level-offs it took us less than 18 minutes to get to our ceiling. And at FL 430 we were seeing a true airspeed of 390 knots on 775 pounds of fuel per hour. In all, the trip down to Uvalde -- we made a lengthy detour so I could see the airplane do its thing -- covered 279 nm, took one hour and seven minutes to fly, and we burned 900 pounds of fuel in the process. The flight culminated in an RNAV approach to near minimums at Uvalde.

Based on our flight compared with the POH figures for the original, Pratt-powered airplane, the Super II is 44 knots faster at the same fuel burn under the same conditions. When you pull the power back to the same cruise speed as the Pratts, the fuel burn is around 25 percent lower with the FJ44s.

Touring Sierra

Normally, I'd call what I did when in Uvalde a "factory tour," but I had to remind myself that Sierra doesn't really build new airplanes, even though it does seem like it at times.

The municipal airport at Uvalde has a single, 5,000-foot-long runway with hangars huddled around it. Many of those hangars belong to Sierra Industries. As of my visit, the company had 85 full-time employees and 84,000 square feet of hangar space, where workers perform every imaginable kind of maintenance work on airplanes, mostly Citations but not exclusively.

On my visit I got the chance to see not only the scope of what Sierra does -- it's quite an operation -- but how it goes about it.

I saw a number of Citations in various states of modification, some just getting started on the project and some nearly ready to fly. On one airplane Sierra technicians had just gotten finished installing the engine support for the new FJ44s, and the structure itself was telling. Instead of removing and beefing up the existing supports, Sierra adds an extra member running through the fuselage side to side, supporting each engine, adding strength without compromising the existing underlying support structure. It's a smart and robust solution.

As a part of its core work, Sierra has to create new parts, and to this end it has invested in that capability, with state of the art machine and sheet metal shops, as well as a separate fabrication shop.

With all of its STCs, the company generates a lot of business on work other than re-engining projects. Sierra has popular STCs for adding extended fuel, a quick-release radome, glareshield switches, an enlarged cabin door, four-point pilot harnesses, and even a three-place aft divan. Often, customers who come in to get new engines on their Citations, and new engines only, leave with a handful of other mods.

One selling tool that isn't really intended that way, or so Sierra says, is their loan/lease program. Occasionally when Sierra customers take an FJ44-equipped Sierra Citation to fly while their jet is in the shop for maintenance, they come back complaining that now they need engines too. Sierra both apologizes and is glad to oblige them.

There are, in fact, lots of other services in addition to engine swaps and radome refurbs that Sierra, or its Uvalde-based partners, offer. While their airplane is in Uvalde, many customers choose to completely redo the airplane while they're getting new engines, opting for fresh paint, a new interior and upgraded avionics.

The airplane we flew was the factory demonstrator, and it was completely refurbished, with a nice leather interior, new upholstery and carpet, and, of course, brand-new FJ44s.

It was also outfitted with a mostly new avionics system, featuring dual Universal primary flight displays and a pilot MFD, with dual Garmin GNS 430 navigators and more. The autopilot was the original and still capable Sperry SPZ-500. It's a good and modern avionics system, though it's not on a par with the Pro Line 21 system in a new CJ3, for example. For a variety of reasons, when it comes to the avionics, it's tough for modifiers to compete with factory-new airplanes.

There are other additions particular to the new engines, including new gauges and controls, and the throttle system is modified for the fadec. Also gone are the controls for the thrust reversers. Huffstutler said that while some customers express concern over their loss, they quickly get over it when they realize the new airplanes simply stop in less distance than the old ones, even without TRs.

Huffstutler says that the decision on the part of Citation II owners to go with brand-new FJ44s on their old birds is a value proposition. While it's hard in this economy to measure the value of any investment, there is still a lot to be said for upgrading the airplane you already own. And for those looking to purchase a used airplane, buying an already refurbished Super II or Super S-II instead of a new, smaller airplane gives you a lot of performance with the comfortable cabin of the Citation II. When Sierra puts its airplanes side by side with existing, unmodified IIs, the performance delta is striking. When it compares them to comparable new airplanes, like the CJ3 or Learjet 45, the performance numbers are comparable and the acquisition price is about half. While prices vary widely based on options chosen, and needed, an extensively converted Super II goes for between $3.5 and $4.6 million.

A big part of the value is to be found with the improved performance of the Williams engines. You go farther on less fuel. Over time, those savings add up. And Sierra is a true believer in the Williams maintenance plan, the Total Assurance Program (TAP), touting its lower overall costs, including no signup fee, better labor and shipping coverage, and 100 percent coverage for wear-out items and mandatory service bulletins. Sierra estimates the savings on maintenance with the FJ44s over the life of the engines (TBO) to be in the neighborhood of $300,000.

Of course, not everything in life is a value proposition. The quality of life improvements that the Super II and Super S-II offer are profound. Compared to the originals, the Sierra airplanes are faster, quieter, smoother and more comfortable. They fly higher, farther and more efficiently, and on some longer trips do away with the need for the fuel stop.

It's interesting to think that with an infusion of new technology, some tender loving care and a sizable investment in the process, you can get a 30-something-year-old airplane up to speed. That you can make it nearly as good or, in some cases, better than new in the process is nothing short of remarkable. It's all testimony to the stout, smart and capable airplanes that Cessna built starting back in the 1970s, and to the improvements in small turbofan engine design that Williams International has achieved in more recent years with the FJ44-series engines.

Ever since it showed up on the scene in Uvalde, Texas, some 30-odd years ago, Sierra Industries has put itself in a great position, taking that new engine technology and marrying it to some great existing airframes.

The results of that marriage are some truly remarkable "new" airplanes.