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Many ways exist to correlate the human heart and an aircraft’s powerplant. For example- neither humans nor aircraft survive long with unhealthy powerplants. Similarly- both benefit from regular- hearty exercise. But even after living a healthy life- they can- over time- develop problems that need correction. Surgeons can even make repairs to heart valves and muscle to restore lost utility- much as a good technician can rebuild an engine to bring it back to better health.

Dave Higdon   |   1st September 2008
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Dave Higdon Dave Higdon

Dave Higdon writes about aviation from his base in Wichita Kansas. During three decades in...
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Aero Heart Transplants:
Engine upgrades yield more-youthful performance.

Many ways exist to correlate the human heart and an aircraft’s powerplant. For example- neither humans nor aircraft survive long with unhealthy powerplants. Similarly- both benefit from regular- hearty exercise. But even after living a healthy life- they can- over time- develop problems that need correction. Surgeons can even make repairs to heart valves and muscle to restore lost utility- much as a good technician can rebuild an engine to bring it back to better health.

Yet in more instances among airplanes- a full upgrade involving the transplant of a younger-design powerplant delivers more than just restoration of past performance. Instead- upgrading to new-technology power can give an aircraft performance- utility and efficiency unavailable with even a factory-new substitution using the original engine design. And when accompanied by upgrades to other equipment – panels- in particular – that older airframe may match even the sophistication of a factory-new model of similar size- but at a cost far less than new.

For the uninitiated- such upgrades involve major work adapting both powerplant and airframe to perform harmoniously and safely. But significant benefits exist – for the right operators and owners.

An Involved Process
In a generic sense- an engine upgrade requires a Supplemental Type Certificate financed and obtained by a company with an idea for improving an old- otherwise desirable airframe. During development and tests required to win the STC- the developers will install- test-fly and prove the safety and basic durability of this change.

That means fuel-system and control-system changes- developing new operational and performance data- as well as creating the materials and procedures that will be used to convert future aircraft in a repeatable way.

Another element in the test and documentation program will be fuel consumption- fuel need and payload information- a new weight-and-balance and runway- and climb-performance figures. The STC process is a demanding one- particularly for a change as dramatic as replacing the original powerplants with something new.

Finally- the replacement engines involved all benefit from their own individual approvals- approvals as part of other aircraft- and operating histories that provide a starting point for earning an STC. The process can be lengthy and expensive but the developers hope to recoup their investment in sales of an STC they believe will prove attractive to those with the target aircraft.

And these enterprises often package other upgrades worthy of consideration for an older aircraft. By combining a panel upgrade- interior refurbishment and an engine transplant- a corporate aircraft maybe getting a little beyond its time can once again run with the younger set.

What an owner opts to embrace should involve balancing potential gains and plans against the costs and value of the enhancements.

Weigh Factors Carefully
Of course- buyers spend more than a share of the STC-development costs when they opt for this type of change. Hardware alone accounts for a large part of a price. And it can be a lot of hardware- much of it expensive.

Engine upgrades that replace an original powerplant design for something different typically include factory-new versions of the upgrade engine- plus sundry other hardware that supports and controls the engine – fuel pumps- for example- maybe FADEC systems with its associated linkages and wiring- as well as those nacelles and engine mounts.

This means these upgrades cost in the millions. It also means new-equipment warranties and a new level of performance. For an owner happy with the base airframe- such an upgrade offers many attractions compared to outright replacing the trusted bird.

Lower direct operating costs stand as perhaps the most visible benefit. Newer technology engines often offer much-lower specific fuel-consumption numbers. They also tend to deliver more thrust - and more thrust up in the flight levels- enhancing both climb and speed. Faster climbs to lower fuel burns at higher speeds add up to dramatically lowered fuel costs.

Newer engines often come with higher hot-section inspection cycles and- even if they don’t- overall lower maintenance needs.

More cost cutting
In some instances- those better fuel- speed and time specifics allow use of lower overall fuel capacity. That reduced fuel weight can couple with lower engine weights to allow a higher full-fuel payload. In other words- the converted airplane can carry more in the cabin. So what’s not to like? Better speed and climb with less fuel- lower maintenance costs and the flexibility to lift more; sounds like a win-win situation.

Well- there are those upfront costs- for one. According to a number of brokers and dealers- putting the airplane through such a conversion makes most sense for those who plan to keep the aircraft long enough to recoup most of the investment. For someone considering an engine upgrade as a way to increase the price of a jet they plan to sell- the value of the investment can be debatable.

For the shopper interested in an aircraft that’s a good value- one of the candidate aircraft with or without the conversion may be a smart option to something else pre-owned but newer – and a big winner against the cost of new- if lead times even make new feasible.

Interestingly- just as Williams International’s FJ44 powerplant spawned a redefinition of the entry-level business jet- this powerplant family underpins the majority of the light-jet-powerplant upgrades we visit below.

Nextant Aerospace:
400NXT Beechjet

Formed last year specifically to develop an upgrade for the venerable Beechjet 400/Hawker 400 series light jet- Nextant Aerospace announced its status on the program earlier this year. While the package may seem a bit pricey compared to others portrayed here- the overall package beyond the engines accounts for much of the value.

For under $5 million- Nextant offers a converted 400 installed with a pair of FADEC-managed Williams FJ44-3AP powerplants in place of the original Pratt & Whitney Canada JT15D engines. The converted jet includes a package with a new interior for the cabin and a Rockwell Collins Pro Line 21 integrated avionics system in the panel.

For owners of the aircraft interested in the payback of the engine conversion alone- Nextant wants $2.4 million for the work that delivers the big payback. The Williams engines help boost range for the 400-series jet to more than 2-000 nautical miles – up from the 1-180-nautical range when carrying the same four-passenger-two-crew load.

To reach this level of efficiency- Nextant is tackling some of the aerodynamic issues associated with the original engines and their installation. Nacelles- pylons- inlets and tailpipes are all receiving a makeover based on computational fluid-dynamics data developed for the aircraft.

These aerodynamic changes couple with the lower fuel specifics of the FJ44-3AP engines to reduce the trip costs a whopping 27 percent below the originally equipped aircraft- according to Nextant.

Beechjet/Hawker 400 owners also have the option of upgrading the panel to the Pro Line 21 as a stand-alone package for $390-000. The engine STC is expected early in 2010- while Nextant says the Pro Line 21 STC will be in hand during the third quarter.

More information from www.nextantaerospace.com

Premier Aircraft:
Falcon 50Dash4
The 50Dash4 Falcon engine upgrade package stands as an unusual example of an enhancement targeting a mid-cabin aircraft – and a triple-engine machine at that.

Premier- a partnership of West Star Aviation and Pacific Aerospace- offers a conversion with the impact of an outright engine swap. In this case- Premier takes the three Honeywell TFE731-3/3D engines off the Falcon 50- ships them to the engine maker where new components and systems convert them to the TFE731-4-1C engines. But in this case the 50Dash4 engine upgrade does exactly what all those light-jet engine transplants promise – just proportionally more due to the higher baseline numbers involved.

That means the Falcon 50Dash4 can use less runway or runways at higher- hotter levels- get to altitude quicker- then fly farther – or carry more at the original range. At the end of the trip- the travelers will have spent less time in the airplane while spending less on the trip. Distance wise- the gain starts at 300 nautical miles and can go as high as 600- depending on the departure field and trip.

Best of all- the conversion from the Falcon 50’s original engines to the TFE731-Dash 4 involves some Premier-created changes to the nacelle and a new nozzle. The combination brings sound levels of the 50Dash4-converted Falcon down to below ICAO Stage 4 standards ahead of this level becoming a requirement.

Premier also offers a panel upgrade to the Rockwell Collins Pro Line 21 glass panel as part of the 50Dash4 work. For the engine work- alone- however- the use of the original engines as the conversion basis helps make this triple-mill job far more reasonable than you’d expect. And the company also offers substitute engines to keep the customer’s airplane useful during the engine conversion process.

Best of all- depending on the Falcon- the 50Dash4 upgrade can come in well under $2 million – or higher for engines not enrolled in Honeywell’s MSP maintenance program.

More information from www.50Dash4.com

Sierra Industries:
FJ44 Eagle II; FJ44 Stallion; Super II

The revolution of Cessna’s jet line continues with Sierra Industries’ performance upgrades. The backbone of these performance upgrades is the incorporation of new jet engine technology and design- giving the aircraft greater speeds- better fuel efficiency and less impact on the environment. Sierra’s line of upgrades replace the breakthrough engine technology of 35 years ago which made possible Cessna’s original line of straight-wing Citations – the Pratt & Whitney Canada JT15D.

It turns out that removing the old-generation Pratts and grafting back on a pair of Williams FJ44 engines puts those older Citations on a competitive performance and efficiency footing against the newer CJ aircraft from Cessna.

Going back about a decade- Sierra Industries in Texas began the process of coupling new engines with the Citation airframes - with extraordinary results. Today- the company offers multiple engine conversions- each targeted to a specific airframe- along with a myriad of other proprietary products and services. Sierra is proud to be the only non-OEM company to receive FAA certification for installing Williams engines on a certificated aircraft.

The Stallion conversion STC’d almost two years ago replaces the old P&WC engines with a pair of new 2-300 lb. thrust Williams FJ44-2A engines. According to Sierra’s customers- the converted Citation 500/501 Stallion model can climb directly to FL430 at any weight or temperature- cruise at 385 knots on 620 pounds per hour of Jet A- and cover 1-400 nautical miles on the aircraft’s standard fuel.

Sierra's Eagle II upgrade also replaces the existing engines with the FJ44-2A. But beyond the engine work- the full Eagle II conversion increases the Sierra Eagle’s wingspan and increases its fuel capacity by 730 pounds – enough to increase the range by a whopping 350 additional nautical miles.

The Super II- Sierra's newest STC- upgrades the Citation II's JT15D-4 engines with Williams FJ44-3A powerplants- producing 2-820 pounds of thrust. The new engines enhance fuel efficiency more than 25%- contributing to increased range and payload as well as reduced emissions.

Taken together- these packages raise payload- increase range and enhance flexibility compared to the original engine/airframe combinations. The Super II boasts a maximum cruise speed of 416 knots- 1-775 nm range and shorter climb times- all products of a gain in cruise-altitude engine thrust of about 40 percent- which also gives the plane the ability to climb direct to FL430.

The engine upgrades are under $2 million- and no matter which package of upgrades you choose- the Sierra Industries performance enhanced aircraft are significantly less costly than the closest competing aircraft.

More information from www.sijet.com

Spirit Wing: SpiritJet
The latest news on this interesting program came earlier this year- when Spirit Wing- of Oklahoma- revealed that its ongoing efforts to complete FAA STC approval for its Learjet 25 engine conversion now includes work to make the upgraded aircraft eligible for single-pilot IFR.

The SpritJet conversion of the Learjet 25 includes – a refit- RVSM-compliancy- engine-and-systems-and-airframe upgrade and comes in the mid-$2 million range.

This use of the Williams FJ44 probably does more for the cost-effectiveness of this 1960s-era business jet than any other conversion. In the case of the Spirit Wing engine conversion- the 25D loses about 100 pounds of sea-level take-off thrust versus the venerable GE CJ610-8A jets provided as original-equipment powerplants.

Despite the slight power drop at take-off- the converted Learjet 25 can still cruise at its normal speeds- but with a huge 50 percent drop in fuel consumption to about 800 pounds per hour – with a higher useful load realized by removing the fuselage fuel tank.

Removing the center fuel tank from the Lear 25D still allows the converted aircraft to fly about 1-700 nautical miles carrying four passengers – a gain of almost 70 percent over the original configuration with its payload-robbing center fuel tank. Additionally- the engine’s smaller nacelles and more-rearward mounting helps give the Learjet a sleeker- faster appearance befitting its improved numbers.

Another significant gain from the Spirit Wing engine swap is the gain of Stage 3 noise compliance. During flight testing of the conformal aircraft- the company found improvements in handling that spin off the different thrust angle and position of the engines – handling changes the company maintains make the re-engined Learjet docile enough for the single pilot to handle in IMC.

The company is also enhancing the panel and improving the interior in this upgrade. There are apparently just enough Learjet 25s out there to make this program viable. So here may be your best chance of owning a hot-flying Learjet – without dropping a bundle for a new 40XR.

More information from www.spirit-wing.com

Weigh the options
Last time we visited this topic within these pages- a smaller number of jet conversions existed and only a couple of turboprop programs were getting traction. But the growth in jet conversions adds options for owners at a time when trading up to something new may be a tough financial proposition – not to mention the time span involved when becoming part of today’s lengthy backlogs.

So- in the meantime- shop carefully. You can already find in the pre-owned market some aircraft converted under a couple of these STCs. Or you may be flying one of the target airplanes and find such an upgrade appealing.

Just remember that the best reason for pursuing such a transplant – the person who most needs to want it – is that person staring back at you in the mirror.

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