Business & GA, Commercial

RVSM Avionics: Down to the Wire

By David Jensen | November 1, 2004

In mid-September, officials from FAA, Nav Canada and Mexico's Direccion General de Aeronautica Civil (DGAC) gathered in Washington, D.C., to sign an agreement that has the three countries concurrently implementing reduced vertical separation minimum (RVSM). It was a formality. Aircraft operators in North America were informed of a program called Domestic RVSM (DRVSM) as far back as May 2002, when a notice of proposed rulemaking was issued. In October 2003, the final rule was published. Nevertheless, the agreement represented just one of many activities in the current hustle to meet the DRVSM launch date of Jan. 20, 2005. Countries in South America and the Caribbean, too, plan to implement RVSM on that date.

When the Western Hemisphere comes on board with programs that reduce vertical separation from 2,000 feet to 1,000 feet in the cruise altitudes, much of the world will enjoy the efficiencies of RVSM. FAA estimates that DRVSM alone will save commercial aviation some half a billion dollars annually, largely through fuel savings brought by the greater flexibility pilots will have in selecting an optimum cruise altitude. Reduced vertical separation -- generally at altitudes from 29,000 to 41,000 feet (FL290 to FL410) -- already has been implemented over the North Atlantic, Pacific, Europe and parts of Asia.

This worldwide application of RVSM represents the culmination of a long effort that began in the 1970s, when, with fuel prices on the rise, the International Civil Aviation Organization (ICAO) initiated studies to determine whether reduced vertical separation is feasible. Successful results initiated RVSM operations in the North Atlantic and parts of the Pacific region.

So RVSM isn't exactly new. What is new, in addition to the tri-nation agreement, is the fact that FAA is beginning to provide RVSM training to air traffic controllers and avionics companies are introducing new RVSM packages for aircraft. Meanwhile, U.S. service centers and dealer shops are busy serving operators, who are scrambling to achieve RVSM compliance by Jan. 20.

Not all of them will make it. The industry analysis group, Frost & Sullivan, estimates that more than 1,600 business jets in the United States will not meet the DRVSM deadline. (The air transport industry already enjoys almost universal compliance.) The operators who are not in compliance will not be able to operate in airspace between FL290 and FL410.

Some bizjet operators have put off equipping their aircraft for RVSM for the obvious reason of cost. Aircraft equipage can exceed $100,000, depending largely on what avionics may be needed. Paul Clouse, RVSM program manager at ARINC Inc., breaks down the cost of RVSM compliance, generally, at 50 percent avionics, 30 percent installation labor and kit costs, and 20 percent to secure certification. After the Jan. 20 deadline and with competition heating up from new RVSM packages entering the market, costs could eventually come down significantly. Lower prices plus a growing awareness among "holdouts" of RVSM's benefits could well create market growth for manufacturers, dealers and service centers.

Still, some noncompliant operators may try to operate in the upper airspace by flying through the RVSM altitudes, to 43,000 feet or higher. However, this option may not be satisfactory. The DRVSM rule allows such climb-throughs but states that noncompliant aircraft must make a steady climb from FL280 to FL430, with no level-offs. And even then traffic density may forbid such maneuvers. "Our expectations are that the traffic will be such that only occasionally will noncompliant aircraft be allowed to climb through RVSM airspace," says an FAA spokesman.

In preparation for the January deadline, FAA began providing RVSM training in October to controllers in the agency's 21 air route traffic control centers (ARTCCs) in the continental United States and Alaska. The training involves computer-based instruction followed by a one-day course on RVSM. Training will continue until the Jan. 20 deadline, and according to an FAA official, controllers who receive their instruction prior to Dec. 20 will need to take refresher instruction.

Also in anticipation of RVSM implementation, more companies are developing avionics packages that, for compliance, must include the following:

  • Two independent, cross-coupled digital altimeters,

  • A Mode C or Mode S transponder,

  • An automatic altitude hold system (to with +/-65 feet [+/-20 m]),

  • An altitude alerter system, and

  • Dual air data computers.

Older aircraft also must have an autopilot interface unit (AIU), so the digital computers can deliver the barometric altitude setting to the autopilot.

Continuing Market

Since the DRVSM deadline is only two months away, the newcomers would appear to be entering the field late in the game. However, Tim Roberts, Honeywell's manager of aftermarket new business development, predicts that the RVSM retrofit market will "go well into 2005 and even into 2006."

Honeywell is one of the established companies in RVSM equipment with whom the newcomers must compete. The company claims "countless numbers" of supplemental type certificates (STCs) for RVSM, having produced compliant systems since the 1970s for aircraft ranging from King Airs to Boeing 747s. Honeywell stresses a "building block" approach to RVSM installations. It recognizes that some fully equipped aircraft may only need to update their static source error correction (SSEC) to ensure more accurate altitude corrections--a software change--while others may require new line replaceable units (LRUs), such as air data computers, according to Roberts. "Sometimes you also have to tweak the autopilot, but that's not a Honeywell job," he adds.

Rockwell Collins, working largely through its dealer network, also is a long-time supplier of altimeters and air data computers for RVSM. The company also supplies autopilot interfaces, primarily for Collins autopilots, says Tom Simon, manager of retrofit marketing for business aircraft.

Although IS&S is a relative newcomer to the RVSM field, having introduced a system for the Gulfstream II in the late 1990s, it has made up for lost time, with systems installed in close to 2,000 aircraft, according to Mike Cawley, IS&S' director of sales. These include the U.S. Air Force's KC-135 tanker fleet and U.S. Navy's C-9 fleet. IS&S systems are approved in about 25 aircraft types.

In 2000 IS&S streamlined its RVSM system, developing the air data display unit (ADDU), which combines an altimeter, air data computer and altitude alerter in a single package. For certification, aircraft need to be equipped only with two ADDUs and an analog interface unit.

Revue Thommen AG, a more than 200-year-old Swiss clock maker, produces a system comparable to IS&S' ADDU. It received a technical standard order (TSO) in January and an STC in a Cessna Citation 650 in July. ARINC, which partnered with Revue Thommen in October 2003, secured the STC and now installs RVSM systems made by both IS&S and its Swiss competitor at its service centers in Colorado Springs, Colo., and Scottsdale, Ariz.

Cawley contends, however, that IS&S distinguishes its product from Revue Thommen's and other manufacturers' RVSM systems with its recently developed "configuration module." This memory device, which includes aircraft-specific information (including the SSEC), fits in the back of the ADDU. Information in the module can be specific to the aircraft model or even to the individual aircraft.

The configuration module's primary benefit is that it speeds up the certification process. With a laptop computer, an RVSM equipment installer can program the module with the SSEC and not have to have the manufacturer configure the system.

Another Newcomer

Revue Thommen isn't the only newcomer to the RVSM field. Minneapolis-based Shadin Co. has developed its ADC-6000 dual air data computer, which was scheduled to receive its TSO in October and approval in a Cessna Citation 500 soon thereafter. Taking advantage of processor miniaturization, Shadin is able to produce an RVSM-compliant dual air data processor that fits in the same space as the old single, analog processor in the Citation 500, Beechjet 400, Diamond 1A and other business jets.

The ADC-6000 can use an aircraft's existing wiring and sensor system, according to Rasheed Reda, Shadin's president. "You only need extra wire for the second processor, on the right side." The only additional avionics required may be a third altimeter for redundancy.

By plugging the ADC-6000 into the aircraft, the left-side pilot's station is brought instantly into RVSM compliance. The operator can retain the original interfaces for the altimeter, autopilot, flight director and vertical navigation (VNAV) without extra wires. Reda claims the dual computer system also consumes less power than the single processor it replaces, again thanks to miniaturization.

Shadin's goal was to make the ADC-6000 easy to install and reasonably priced. Reda claims the installed price would be approximately $75,000. The company holds the Citation 500 STC for its RVSM system. However, it is working with service centers to gain STC approval for the Beechjet 400, Diamond 1A and Piper Cheyenne (with Beech Technology); Gulfstream II and III (with Business Jet Service), and older (below serial no. 375) Citations (with Northeast Aeromotive).

Like Honeywell's Roberts, Tom Chapman, Shadin's business development manager, foresees an RVSM market extending well beyond January 2005. "We believe there's a market for 500 to 600 Citation jets alone," he tells Avionics Magazine.

Insight Avionics Corp. expects strong RVSM sales, too--for Learjets. Pursuing the Lear 20 and 30 series market, this Buffalo, N.Y.-based company had expected to have its newly developed system STC'd in its Lear 35 in October. Insight Avionics believes it holds an advantage for Learjet owners, particularly in installation time, because its RVSM product was designed specifically for their aircraft. The company claims installation takes no longer than three days, and that the total cost for compliance would be about $100,000.

"Very little modification and rewiring are required," according to Brian Wrightman, the company's marketing manager. Insight Avionics' RVSM system, which includes digital altitude preselectors, comes with interfaces for Learjet autopilots: models 110, 220, 431 and 431A. And, says Wrightman, the company is working on an interface for the model 535 for U.S. military Learjets.

Achieving compliance to DRVSM can be a complex process, involving maintenance and crew training plans, a revision of the aircraft's minimum equipment list, a height-monitoring test flight, and a letter of authorization (LOA), which the local Flight Standards District Office grants following the approval of the monitored flight data.

The one company that provides all three services for RVSM compliance -- equipment installation, monitoring tests and satisfactory completion of the LOA --i s ARINC. The LOA activity, performed at the company's Annapolis, Md., headquarters, has doubled over the past 12 months, according to Clouse. "We average about 80 aircraft a month," he tells Avionics Magazine.

For its monitoring service, ARINC has developed a portable, initial monitoring system, which includes a GPS receiver, two antennas and a laptop computer that records the GPS positioning signals. The antennas are attached to each side of the aircraft cabin to ensure signal reception from at least three GPS satellites. ARINC has initial monitoring systems at five locations throughout the United States and offers same-day or next-day service to operators.

Means for Monitoring Height

Initial monitoring is a prerequisite for RVSM approval. If, however, an operator has a large number of same-type aircraft requiring RVSM equipage, the operator needs to have only a sample size (usually 60 percent) of its fleet tested by an initial monitoring system. And if the operator has gained RVSM experience from previous installations, it needs to have only two aircraft tested, according to Clouse.

Initial monitoring should not be mistaken for the passive height monitoring that will be conducted by FAA, using the agency's newly developed ground-based system (see story in Industry Scan, page 10). Nor should it be confused with the tests conducted by Aeromech Inc., Everett, Wash., and Kohlman Systems Research, Lawrence, Kan., which use a towed trailing cone to determine an aircraft's "air curve," i.e. outside air flow around the airframe and static air system. Results from these tests are used to create RVSM data packages for the certification of aircraft groups or individual aircraft that might have special equipment impacting the surrounding air pressure. The Citation 500 with Sierra Industries' re-engined "Eagle Mod" or a plane with a new radome would be examples of individual aircraft requiring cone testing, according to David Doucette, vice president, Aeromech.

ARINC and its competitor in initial monitoring, CSSI Inc., also conduct safety assessments for countries and regions preparing for RVSM. The U.S. Trade Development Agency--in an effort to expand overseas markets for service and product providers in the United States-- recently contracted CSSI to assist seven countries in South America and the Caribbean region that plan to implement RVSM. The countries are Argentina, Ecuador, Venzuela, Cura�ao, the Dominican Republic, Haiti, and Trinidad and Tobago.

Bob Miller, CSSI's director-airspace analysis and modeling, says his company is working with FAA to assist the seven countries, which were chosen "because of their amount of traffic flow, progress in RVSM implementation, and because of countries' request for assistance."

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