With only about 15 months left to go before the start of domestic reduced vertical separation minimums (DRVSM) in the U.S., the clock is ticking for business jet and turboprop operators that have yet to schedule an appointment with their local service center for needed upgrades.

Not surprisingly, modifying older models for DRVSM is proving the toughest challenge. While newer aircraft benefit from certification solutions that have been developed by their respective airframe and avionics manufacturers, many older airplanes are being left out in the cold. These airplanes are not being certified under “group” status because of their limited numbers and are therefore proving far more difficult and costly to bring into RVSM compliance.

More than any other single item, the autopilot in older analog airplanes is to blame for the complexity and expense of compliance. RVSM requires very strict height-keeping capability, and the older analog boxes simply are not up to the task. And the disappointing truth is that manufacturers aren’t producing new-technology autopilots for the vast majority of older airplanes in service today.

For some airplanes the overall equipment STCs do not yet exist and, indeed, may never exist. For others, the upgrades to avionics and additional systems will set owners back as much as $250,000, a steep price to pay for the fleet’s old dogs, many of which might be worth more sold off in pieces than their owners can attract on the used market with an intact airplane.

“The reality is that requirements for upgraded avionics and quieter engines are relegating lots of otherwise perfectly airworthy airplanes to the scrap heap,” said aviation consultant and former NBAA president Jack Olcott. Still others are being converted into aeromedical transports, which are exempt from many of the FAA’s requirements, or are being pressed into service outside the U.S. and Europe.

There appears anecdotal evidence that a growing number of operators have deemed RVSM too costly and will not seek certification. According to Dan Frahm, director of avionics business development for Elliott Aviation in Moline, Ill., it is likely that many operators of King Airs and other high-performance turboprops who normally fly at FL290 or FL310 will want to cruise just below the floor of DRVSM at FL270. The minor increase in fuel consumption, these operators reason, is preferable to the major cost of RVSM certification.

“The downside is that they will sometimes be unable to fly above weather, eliminating an important safety option,” said Frahm.

What is likely to happen once DRVSM becomes the law of the land, he added, is that older business jets not certified for the new rules will be forced into the airspace just below the RVSM flight levels and non-RVSM turboprops will be assigned altitudes below the jets. This will mean that a King Air 350 operator who is used to cruising at FL310 on long trips may now have to settle for FL230 while non-RVSM Learjet 25s and older Hawkers, Citations and Falcons are given FL250 and FL270.

“RVSM is the most expensive mandate in my lifetime, and it’s also got the shortest implementation time of any mandate in memory,” said Frahm. “But it’s an airline-driven world and we in business aviation unfortunately don’t have that many choices.”

The FAA estimates that DRVSM will save the airlines about $5.3 billion in fuel costs in the next decade. With a figure that dramatically high, it’s unlikely the burden RVSM creates for business aircraft operators will persuade the FAA to rethink its RVSM policy. Still, it’s a fact of aviation that operators of older business airplanes usually fly such aircraft because they can’t afford anything newer and more capable. When hit with the costs for RVSM upgrades in the very airplanes that are the most costly to modify, some of these operators may decide it’s time to get out of aviation altogether or go back to flying piston twins.

Taming the Older Learjets
The Learjet 20 series is among the list of older models for which RVSM approval has been elusive. Two companies, Avcon Industries of Newton, Kan., and LJSC in Wichita, have dived into the approval process, but so far both firms have been stuck in flight-test mode. A third, Spirit Wing of Guthrie, Okla., was preparing its Learjet 24D RVSM testbed for flight at press time.

Avcon president Larry Franke said the initial test airplane in his firm’s RVSM program, a company-owned Learjet 25D, met RVSM height-keeping requirements (±65 feet) for autopilot operation, but so far the company has been unable to develop a group approval package. The modifications are now being tested by Avcon and its program partner, Bizjet International, using the Learjet 24/25’s original FC-110, which must first be sent back to the manufacturer (now L-3 Avionics Systems) for bench testing and any needed repairs. The $149,500 upgrade also adds an autopilot interface unit, in addition to digital air-data units and altimeters from Malvern, Pa.-based Innovative Solutions & Support (ISS), and new Rosemount pitot probes.

According to FAA specifications, the autopilot must be able to maintain level flight in its “altitude hold” mode between FL290 and FL410. Due mainly to the slow sampling rate of the older autopilot, the FC-110 in some airplanes has had a hard time maintaining altitude to within 65 feet and has been known to porpoise under certain conditions. Before the FAA can grant group approval status for the Learjet 24/25 series, Avcon had to solve this technological shortcoming. The company gained the initial equipment STC for the Learjet 20 series late last month. Franke said he planned to have three of five airplanes involved in flight testing for group approval by the start of this month’s NBAA Convention.

There are about 500 Learjet 20-series aircraft in operation worldwide, many of them based in the U.S., where domestic RVSM will begin in the airspace from FL290 to FL410 on Jan. 20, 2005.

Meanwhile, LJSC, a two-year-old engineering and certification consulting company based in Wichita and composed of ex-Bombardier employees, has been flight testing
a Learjet 25 in preparation for an RVSM group package of its own for the series, priced at $149,975.

Several Learjet 25s have been flown for its program to test the compatibility with RVSM requirements of the airplane’s autopilot, also the FC-110. Modifications outlined by LJSC (and tested by the company’s partner in the program, Wichita-based Executive Aircraft) include removing the existing pitot tubes, altimeters, shoulder- and flush- mounted static ports, static-defect correction module, autopilot air-data computer/sensor and the altitude alerter. These items are replaced with the Rosemount pitot-static probes, standby altimeter, air-data digital units and an analog interface unit in a similar configuration to the Avcon/ Bizjet package. Group approval is expected by year-end.

RVSM for Hawkers, Citations and Falcons
One of the issues for Raytheon Aircraft customers has long been RVSM certification for the company’s older aircraft. Operators have been asking Raytheon customer-service officials to address the RVSM timetable. ISS announced last month that it had received a $3 million order for RVSM-compliant avionics intended for the Beechjet and its predecessor, the MU-300 Diamond. Deliveries of the equipment are scheduled to start in the fourth quarter. A Raytheon official said the RVSM program for these aircraft is scheduled for completion by the end of the year.

For the Hawker 700B equipped with Collins avionics, Raytheon Aircraft Services in Chester, England, has certified RVSM for 17 aircraft and has obtained group approval, an important milestone. Raytheon Aircraft in Atlanta has an STC for RVSM on the 700A/B with Collins avionics.

The FAA has already certified RVSM compliance solutions for the Falcon 10 and 20 from Garrett Aviation, making these a couple of old dogs that have learned new tricks. Garrett’s package for Falcon 10s and Falcon 100s equipped with the Collins APS-80 avionics includes dual ADC-87A digital air-data computers; ALI-80A altimeter; two-inch standby 50,000-foot backlit altimeter; and Rosemount dual-temp probe.

On the Cessna Citation front, Shadin has been in the news recently for its RVSM compliance package, a solution that involved joining forces with two other specialty companies– Arinc and AeroMech–to provide fully compliant, plug-and-fly RVSM solutions for a number of Cessna Citation models, spanning the 500/ 501, 550/551, S550 and 560.

The Shadin package consists of a drop-in dual air-data computer replacement of the original AZ241 ADC. Shadin’s program is organized among shops that have reputations for Citation experience. The company provides a document template to help relieve regulatory paperwork issues for the package. Estimated completion time for the modification is less than 40 hours.

The Minneapolis company is also currently working on RVSM applications for the Beechjet 400, Diamond IA and Gulfstream II/III, and a spokesman said that an STC program for Piper Cheyenne II RVSM is nearly complete.

Jet Source, a full-service FBO located at the McClellan-Palomar Airport (KCRQ) in Carlsbad, Calif., offers the Shadin ADC. According to Patrick Tierney, Jet Source director of avionics, the ADC-6000 system works well as a direct replacement for the existing AZ-241 single air-data computer.

Jet Source recently held a one-day RVSM seminar at its 120,000-sq-ft facility, inviting representatives from Shadin, Aeromech, the FAA, Bendix/King, L-3 Avionics, Garmin, Collins, Sandel and Air Cell to display and demonstrate their products to Citation owners and operators.

Maintenance Shop Slots Filling Up Fast
Another well known shop that says it’s ready for an influx of customers needing RVSM work is West Star Aviation, a Learjet specialist located on the Western Slope of the Rocky Mountains in Grand Junction, Colo. The maintenance outfit has co-developed an RVSM modification package with Honeywell for the Learjet 35. On August 1 West Star received an STC, and it delivered its first RVSM-certified aircraft, a 1977 Learjet 35A, two weeks later.

As of last month, West Star had already booked an additional 40 aircraft for the modification. It forecasts that it can handle at least half of the more than 400 candidate aircraft in the Learjet fleet. The package is currently the only non-factory RVSM for Learjet 35/35A/ 36/36As equipped with the FC-200 autopilot and Century III Softflite wings, and includes those aircraft that have been modified with Avcon fins and/or Raisbeck body lockers. (Interestingly enough, one FAA official told AIN that Learjets with Raisbeck lockers are actually more stable at altitude than non-modified airplanes and therefore are just as easily upgraded for RVSM.)
More than 30 of the aircraft that are scheduled to come to Colorado for the makeover are Model 35s and 35As from AirNet Systems of Columbus, Ohio.

“At an installed price of $165,000 for standard-configured aircraft, it is the least expensive RVSM alternative on the market for the Lear 35/36 series,” said Russ Williams, West Star’s vice president of sales and marketing.

The West Star package includes Honeywell digital altimeters and air-data equipment, an Aerosonic standby altimeter and Rosemount probes that provide reliable and consistent pitot-static pressure data.

Williams said the goal of getting 200 aircraft certified in the time available depends on the company expanding its own capacity and working with other qualified facilities. “We are aware that many operators frequently wait until the last minute to meet compliance deadlines,” he said. “But if they wait until next year to begin planning their RVSM modifications, it may limit their ability to obtain a slot in our schedule.”