Continued Airworthiness and RVSM

The effective date for domestic RVSM -- Jan. 20, 2005 -- is almost upon us, and if you are not already operating under a Letter of Authorization (LOA), you need to get moving. Even though the approval process is getting more efficient as the various Flight Standards District Offices (FSDOs) become more experienced in handling applications, approvals can still take months to obtain. And if your aircraft, crews and maintenance procedures are not certified by that January launch date, you will not be permitted to operate above FL 280. There is discussion on issuing of waivers, but the clock is ticking.

As those who have already obtained approval and those deep into the process know well, the procedure is the bureaucratic equivalent of undergoing a root canal: painful, but necessary.

The reason behind the belabored and exacting process is obvious: By reducing vertical separation to 1,000 feet, the FAA has to ensure as best it can absolute accuracy among participating aircraft. Each aircraft's dual altimetry systems must be accurate to plus or minus 80 feet, and that tolerance must be maintained; system degradation over time is not an option. Simple arithmetic demands it.

For example, imagine that your aircraft's RVSM system -- hardware and software -- has a 1-percent error. At 10,000 feet that results in a 100-foot error; at 40,000 feet it works out to 400 feet. Now, what if the airplane above or below has a similar error margin, or slightly worse? You can't count on TCAS to sound the alarm since that system relies on the aircraft's altimetry as well. If something happens to degrade the accuracy of the aircraft altitude indicating system, there's nothing to alert the crew. And it is for those reasons the FAA is requiring operators to present for approval an ongoing maintenance plan for all RVSM aircraft.

An approved plan addresses maintenance procedures, quality control and individual accountability. European operators and U.S. FAR Part 121 and most Part 135 operators are already familiar with the amount of effort required to win plan approval. Part 91 operators about to immerse themselves in RVSM maintenance matters ought to begin by familiarizing themselves with the program's requirements. Two key documents to review are Part 91, Appendix G, Section 3, which stipulates the requirement for an approved RVSM maintenance program, and the Airworthiness Inspector's Handbook, 8300.10 Change 16, Chapter 5.

An RVSM maintenance manual is essentially an operations guide that spells out how you intend to satisfy the requirements specified in Part 91, Appendix G, Section 3. The manual becomes your quality control system. While the OEMs of RVSM type certified aircraft and the STC holders (in most cases) are responsible for establishing the maintenance procedures, it is the responsibility of the operator to ensure full operational compliance. The manufacturers have been providing operators assistance to varying degrees.

"Gulfstream has been very helpful," said one operator of two different models, who did not wish to be identified. He explained that the Savannah manufacturer created a maintenance plan that has been "pre-approved by the Atlanta FSDO, where the operator fills in the blanks and submits to its local FSDO." However, he further noted that the various FSDOs have different opinions as to what an RVSM maintenance package should contain. That matter of local interpretation of the rules can prove frustrating. After polling many operators who have received approval of their manuals, the path to success seems to be paved with "cooperation." Do not insist that the "FSDO does it differently in Wichita," if you're seeking approval from a FSDO elsewhere. You need to find out what your local inspectors want and make sure they get it.

"The key to our success in getting our plan approved was working closely with our local office," said Steven Reed, chief pilot on a Learjet 60 with Bretford Manufacturing, in Waukegan, Ill. "By working with our FSDO, we were able to format our plan the way they wanted it. They rejected the Bombardier plan and wanted changes made, so we made them."

There seems to be some confusion at the FSDO level about approval for the maintenance plans on new aircraft that are already type certificated for RVSM operations. One Learjet 45 operator seeking RVSM approval for his aircraft said, "The FSDO does not seem to understand that the aircraft has come from the factory equipped for RVSM and we should not have to reproduce test data. They also do not understand that most of the system is contained in the electronics and there are not as many components in our system."

With newer systems, there are fewer physical components, and functionality has been combined into a computer or other integrated unit. Lack of familiarity on the part of the FSDOs with the many different configurations is certainly understandable. This is where a little bit of patience and communication can help smooth out any misunderstandings. The Learjet operator noted that his first two applications were turned back and seemed more than a little frustrated with encountering so many obstacles in getting operational approval for a new, RVSM-compliant aircraft. Several operators who have either just received new aircraft, or are going to receive new aircraft, are looking toward the manufacturer for help, but it seems that there is little the OEMs can do at the local level. "The manufacturers should be working with the FAA to get this resolved," the Learjet operator said.

Another point of controversy is the question of an operator including the actual manufacturer's or STC provider's maintenance manual as part of the RVSM submittal. Roger Lipcamon, maintenance manager with Knapheide Manufacturing Co., Quincy, Ill., contracted Cessna to install RVSM modifications in his company's Citation CJ. Then he submitted the entire Cessna-provided RVSM-specific manual as a part of his operation's application, only to go back again when Cessna then revised its document. "Our FSDO was concerned with making sure we had an updated table of contents and list of effective pages for our manual," he added. "So, if there are more changes, we will have to resubmit each time."

Other operators report that they have been allowed to use references to the manufacturer's manual in their submissions, greatly reducing the amount of paper. Von Campbell, president of QC Enterprises, Inc., Oakwood, Texas (, has consulted for many companies seeking RVSM approvals and has dealt with over 15 different FSDOs. "The biggest mistake most operators make is to submit the entire manual instead of making reference to it. They end up having to make revisions to their own manual to keep it up to date," he said. "Each FSDO is a little different, but making reference keeps the workload down."

To get a better understanding of what your local inspector is looking for, get a copy of the Airworthiness Inspector's Handbook, which is available on the FAA Web site. This publication provides guidance to the FAA inspector who will be approving your maintenance program. What follows in bold italics are some key RVSM matters addressed in the handbook. Advice on compliance follows.

Identification of components considered to be RVSM Critical, and identification of structural areas noted as RVSM Critical Areas.

To comply with this requirement, an operator needs to understand how the aircraft's altitude indicating system operates, from the pitot tube to the autopilot. Remember, each component will have an accuracy tolerance. If an individual component is on the ragged edge of tolerance, it may be enough to push the entire system over the limit. The electronics need to be properly identified by part number and software level, as appropriate. If a component is replaced in the hangar with an identical part number component, but the technician fails to recognize the software level is non-compliant, you may end up with a non-compliant aircraft.

The area surrounding the static port can be a particularly critical area, depending upon the aircraft involved. Paint buildup, dents, even skin depressions can affect system performance. Surface condition and the serviceability criteria for this should be included as part of the aircraft certification package or included in the maintenance manual.

The phenomenon known as "skin waviness" in the area of the static port refers to tiny indentations or ripples in the aircraft skin no larger than a thumb print and invisible to the naked eye. These can cause erroneous indications in the altitude indicating system. Some aircraft may need periodic inspection of the area using specialized equipment. The training of the technician and certification of the equipment to check waviness need to be identified. If the area is critical, you will need to specify how you will protect it from scratches and dents and what procedures will be employed to assure the condition is not altered. For example, if the aircraft goes in for paint, the paint crew must be alerted to the critical nature of the area and proceed accordingly.

To obtain RVSM compliance, some aircraft need their actuators and mechanical flight controls upgraded to maintain a precise altitude. Older actuators may not be able to maintain the necessary tolerance at altitude. If you require specific actuators for RVSM operations, you need to identify them and put measures in place to maintain configuration control.

On the subject of parts, be sure that those most likely to be replaced, such as pitot tubes, air data computers and actuators, are on your shelf and RVSM-compliant. This is especially true if yours is a unique RVSM configuration.

Name or Title of the responsible person who will ensure that the aircraft is maintained in accordance with the approved program.

Self-explanatory, but operators need to stay current on this stipulation. If your designated maintainer has left your operation, you could be found non-compliant on this technicality during an audit. Better safe than sorry, so keep the ID current.

The method the operator will use to ensure that all personnel performing maintenance on the RVSM system are properly trained, qualified and knowledgeable of that specific system.

Here, the inspector wants to know your training regimen and records keeping, and how you keep the information current. If you choose to use a service center or repair station, identify how you will check the operation's records to ensure they are up to date. Training on the RVSM system is not mandatory per the FAR, but you may need to indicate how those who work on the aircraft will be made aware that it is equipped for RVSM and then ensure they consult the appropriate manual before servicing RVSM equipment or systems.

The method the operator will use to notify the crew if the aircraft has been restricted from but is airworthy for an intended flight.

If for example, you need to replace an RVSM-specific component with a non-RVSM-compliant part, you may be airworthy but not RVSM capable. How are you going to notify the crew? Temporary placard? Logbook annotation? Both? You must make sure both the pilots and mechanics are aware of the notification method and ascertain the aircraft's RVSM status before any flight.

The method the operator will use to ensure conformance to the RVSM maintenance standards, including the use of calibrated and appropriate test equipment and a quality assurance program for ensuring continuing accuracy and reliability of test equipment, especially when outsourced.

If you use your own test equipment, you will need to identify the calibration method and frequency with which it is done, and identify the person performing the calibration. If you outsource the testing, you need to be able to verify that the vendor's equipment is calibrated and what program they use to keep it that way.

The method the operator will use to verify that components and parts are eligible for installation in the RVSM system, as well as to prevent ineligible components or parts from being installed.

This can be a line item referring back to a list in your manual, or it can be a statement referring back to the manufacturer's manual.

The method the operator will use to return an aircraft to service after maintenance has been performed on an RVSM component/system or after the aircraft was determined to be non-compliant.

Most maintenance can be checked on the ground; however, there will be times when you will have to fly the airplane to demonstrate its RVSM compliance. The worst-case scenario would be to receive a letter from the FAA informing you that your aircraft was painted by a Height Monitoring Unit (HMU) and found out of spec. You need to determine the cause of the problem and what corrective action to take. If you cannot isolate the problem on the ground, prepare for troubleshooting flights.

Periodic inspections, functional flight tests, and maintenance and inspection procedures with acceptable maintenance practices for ensuring continued compliance with the RVSM aircraft requirements.

To receive RVSM certification, an aircraft's flight performance must be checked or confirmed by an HMU or GPS Monitoring Unit. With the latter, instruments are installed aboard the subject aircraft, which then flies a set heading and altitude for about a half hour to an hour. Further confirmation flights may be required periodically, if specified by the manufacturer or STC holder.

If you need to remove a component for other maintenance, usually a post-maintenance ground check will suffice. But you need to identify the specific components that definitely require inflight testing. That would be a good time to align any other altimetry-related scheduled maintenance with any RVSM peculiar checks. You do not want to replace components that could affect RVSM performance and possibly lead to a flight test. Use of Built In Test Equipment (BITE) is specifically excluded by RVSM regulations.

The maintenance requirements listed in Instructions for Continued Airworthiness (ICA) associated with any RVSM associated component or modification.

This is where you reference each specific RVSM maintenance requirement, or basically a Chapter 5 with RVSM-specific items. This is the item where operators have seen differences of opinion between different FSDOs. Providing a reference to the maintenance requirements will greatly simplify the approval process.

Any other maintenance requirement that needs to be incorporated to ensure continued compliance with RVSM requirements.

The phrase "any other" is a red flag. This allows local inspectors to use their own discretion in imposing either temporary or permanent maintenance requirements. If yours is the very first RVSM-compliant aircraft of its type in the region, maintenance criteria more stringent than the guidance or the regulations specify may be imposed.

Operators using the services of FAR Part 145 certificated repair stations must include provisions to ensure that the requirements of their RVSM programs are being met.

Operators that contract RVSM work with a repair station need to ensure the outfit is approved to perform the work and that its program meets the aircraft's specifications and equipment requirements. If allowed, avoid citing the repair station by name in your RVSM maintenance program application. If the shop is named in the maintenance plan and later goes out of business or is otherwise unavailable to perform work on the aircraft, the operator would have to add a new repair shop name to the maintenance program, and then apply for and receive approval before it could return the aircraft to RVSM operations.

While looking at all these areas, do not forget your MEL (and MMEL if applicable). Once you have added RVSM capability, you need to reflect this in your MEL. You should add provisions in the MEL for contingencies for non-RVSM operations just in case. While this effort is a bit of duplication with your maintenance plan, it should not be overlooked.

A number of resources are available to help operators through the RVSM maintenance approval process. The FAA has an informative Web site dedicated to RVSM ( The NBAA has a Web page and templates that can be used as a guide: Visit, then do a search for RVSM. For those wishing to receive comprehensive RVSM maintenance training, Global Jet Services, Inc. ( has a thorough and comprehensive program. The manufacturer or STC holder should also be able to provide advice or help.

Many operators report that by employing the reference method, their approved RVSM maintenance manuals ended up being 11 to 16 pages long. Work with your local FSDO and find out what it is looking for. And remember, be patient and cooperative.

The reward for this effort is well within reach and should open up a lot more airspace, thereby saving fuel and flight time, two of our most precious commodities. B/CA


The tolerance for RVSM OPS is plus or minus 65 feet for aircraft built after April 9, 1997, and plus or minus 130 feet for aircraft built prior. This equates to less than one quarter of a percent at FL 40. The basic components of an RVSM-compliant system involve the pitot/static system, which includes the pitot tube/static port, standby altimeter, VSI, airspeed/Mach and associated plumbing. The air data computer is the brain of the system. For domestic RVSM, U.S. operations can have a single ADC, but for international RVSM operations, you need two. Along with the ADC you have associated symbol generators and controllers. The next part of the system is the autopilot of flight director and navigation computers, which are responsible for maintaining altitude as directed by the pitot/static system. The ATC system for encoding altimeters may be included on some systems depending on how they receive their data. Any one of these components may have a built-in error tolerance of much less than 1 percent, but an adverse combination of units may actually put a compliant aircraft out of RVSM tolerance.

A normal pitot/static system check per FAR Part 91.411 is usually 24 months. The problem with this check as it pertains to RVSM is that it cannot detect skin defects near the static port. This necessitates an airborne test using either a ground-based HMU (Height Measuring Unit), which uses a series of five ground receivers that triangulate aircraft true altitude (based in Gander, Newfoundland, and Strumble, United Kingdom), or use of a GMU (GPS Measuring Unit) temporarily installed in the aircraft and operated by a specially trained technician. The GMU flies a straight and level profile for up to 45 minutes to determine compliance. After the test, the operator is given a pass or fail notice.

Failing the test can be very expensive. Since the tolerances are so tight, you may have a hard time determining the culprit. This means you will have to repeat the test. Aircraft are being requested to participate in voluntary measurement as part of an initial data gathering process depending on their build or group status. If you fail your HMU/GMU, you will be notified and will have to respond in writing with what your corrective action plan is. Currently, aircraft found out of tolerance receive written notification with no penalties assigned, just a request for a response with the corrective action plan. This probably will not last long; expect penalties as reflected in FAA Order 2130.3A Appendix 4, with fines reflecting the severity of the infraction.


Group Aircraft

The aircraft have been manufactured to the same design.

Avionics and static systems are installed in a same manner.

Non-Group Aircraft

The aircraft is approved as an individual aircraft.

Altitude-Keeping Equipment

Must be equipped with 2 independent altitude measuring systems.

Must be equipped with at least 1 altitude control system.

A tolerance of +/-65 feet in level flight

A tolerance of +/-130 feet in level flight for aircraft certificated before April 9, 1997

Altitude Alert

Alert signal tolerance at +/-300 feet for aircraft certificated before April 9, 1997

Alert signal tolerance at +/-200 feet for aircraft certificated after April 9, 1997

Altimetry System Error (ASE)

At the full RVSM flight envelope, ASE absolute value may not exceed 120 feet for aircraft certificated before April 9, 1997.

At the full RVSM flight envelope, ASE absolute value may not exceed 80 feet for aircraft certificated after April 9, 1997



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