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Introduction to DRVSM

Domestic Reduced Vertical Separation Minimum (DRVSM), also designated as RVSM, is a new altitude structure program in the U.S. that has been in use in numerous regions of the world and in designated flight tracks across the Atlantic Ocean since 1977.

It has been designed around the principals of:

• Extending the usable airspace at and above FL290 (29,000 feet MSL) to FL410 to enhance ATC flexibility with traffic flow
• Helping alleviate crossing traffic and conflict points in high density airspace
  Increasing airspace capacity
• Providing enhanced operating efficiencies of flying at more fuel efficient flight levels and user preferred routing
• Reducing ATC controller work load

DRVSM is currently the designation of RVSM airspace and operations within the United States. The designation DVRSM is synonymous with RVSM and it currently identifies all intended Reduced Vertical Separation Minimum (RVSM) airspace operations and is designated as the airspace beginning at FL290 and extending up to and including FL410.

This block of airspace is considered “Special Qualification Airspace” by the FAA because you are required to have training and the proper equipment in order to fly in that block of airspace. All aircraft and flight crews that operate in RVSM are required to have FAA approval and authorization prior to conducting flight operations within this airspace.

NOTE: Most likely you do not need to get your own RVSM certification. The company you work for or will be working for will provide the necessary training and equipment in order for you to operate in RVSM airspace. Furthermore, getting RVSM certification before going to your interview, hoping that it will increase your chances of getting hired, would most likely be a complete and total waste of you time and money!

Key Elements of RVSM

Background

RVSM designated airspace became effective in the United States on January 20, 2005, at 0901 UTC. RVSM airspace designation was also be implemented within Canadian and Mexican airspace at this same time as well.

As pointed out earlier, RVSM is comprised of all airspace from FL290 to FL410 inclusive, and provides 1,000 feet vertical separation between each flight level.

Prior to the implementation of RVSM, vertical separation of aircraft requirement between FL290 and FL410 required 2000 feet vertical separation under the Conventional Vertical Separation Minima (CVSM) standard.

RVSM Altitudes (FL)  CVSM Altitudes (FL)
430————-430
410————-410
400                               
390————-390
380                               
370————-370
360                                
350————-350
340                               
330————-330
320                                
310————-310
300                                
290————-290

New RVSM Standard – FL 290 to FL410 require only 1,000 feet Vertical Separation Minimum

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And, just like from your Private Pilot days, flight level assignments for direction of flight at these altitudes will follow the same altitude designations:

• Magnetic Courses between 000º through 179º – Odd Flight Levels (FL290, FL310, etc.)
• Magnetic Courses between 180º through 359º – Even Flight Levels (FL300, FL320, etc.)

Some RVSM Requirements

In order for an airline to operate within these flight levels, FAA approval of an airlines RVSM program is required prior to authorization to conduct flight operations within RVSM airspace.

In order to achieve this, several issues had to be addressed by the airline to get this authorization.

For instance, aircraft airframe and systems validation for increased tolerances for operations within RVSM designated airspace had to be completed. This includes but is not limited to:

• Aircraft skin mapping to identify and eliminate any sources of interference or errors within aircraft static system inputs and measurement.
• Increase inspection intervals for critical RVSM aircraft systems.
• Upgrade of the Traffic Alert and Collision Avoidance System (TCAS) II system to Version 7.0 for altitude threshold reductions in RVSM airspace.

Furthermore, flight crews needed to become familiar with the following RVSM elements:

• Operational procedures when flying within RVSM airspace which include notifying ATC if unable to continue flight within RVSM criteria.
• The importance of flight crews to cross check each the others instruments to ensure that ATC clearances are promptly and correctly complied with.
• The importance of flight crews to validate all aircraft altimeter indications during preflight checks to verify that the instruments are within 75 feet of each other and within 75 feet of the field elevation when the correct barometric pressure is set.
• Understand the problems of visual perception of other aircraft operating at 1,000 feet separation during night time conditions, during turns, same direction traffic, or when encountering phenomena such as the northern lights.
• The characteristics of aircraft altitude capture systems which may lead to the occurrence of altitude overshoots during climbs and descents.

TCAS Differences

Besides the above elements, crews also needed to be aware of some TCAS differences as well.

1) The TCAS II system has been updated to Version 7.0. This software update provides for reduced traffic threat tolerances when operating within RVSM airspace. It should be noted that with the update of the TCAS II system software to Version 7.0, there have been very few Resolution Advisory (RA) during current normal RVSM operations, but Traffic Advisories (TA) can and do occur regularly.

2) With the threshold traffic threat criteria reduced and when operating in RVSM airspace, flight crews should continue to configure and operate the TCAS system normally as outlined in their SOP. This includes all responses and subsequent actions to a TCAS TA and RA.

3) Flight crews should implement the following procedures when climbing or descending through RVSM airspace to help mitigate and/or eliminate potential TCAS TA and/or RA occurrences.

• Climb and descent rates in RVSM airspace should be limited to 1,000 feet per minute when operating within 5 nautical miles and within 2,000 feet of other aircraft to minimize the possibility of generating a TA and or a RA (reference the Threat Detection Criteria table below).
• Flight crews must ensure that altitude capture and overshoot of an assigned and selected altitude does not exceed 150 feet.

Flight Crew and ATC Communications

Now, with the introduction and implementation of RVSM operations, it is even more important that crews maintain more awareness of their altitudes tracking.

Communication between the flight crews and ATC require early identification of problems and subsequent notification to ATC of conditions that could impact the ability of the aircraft to continue to operate safely within RVSM designated airspace. Some of these areas of concern could be:

• The inability of flight crews to maintain assigned and selected altitudes within a maximum of +200 foot tolerance due to turbulence and/or mountain wave influence. NOTE: Severe turbulence and/or mountain wave activity (MWA) can induce altitude deviations of 200 feet or greater.
• Failure of any of the following required aircraft systems:

(1) Transponder(s)
(2) Primary altimeter system (captain or copilot)
(3) Altitude alerting and capture capability
(4) Automatic Flight Control System (AFCS) or autopilot

If the flight crew encounters any of the above abnormalities or problems, they should advise ATC immediately that they are unable to continue as RVSM compliant, and coordinate a contingency plan with ATC.

Pre-Flight Planning for Flight in RVSM Airspace

During your pre-flight planning and prior to conducting flight operations in RVSM airspace, crews should be aware of any conditions that may affect operation in RVSM airspace. This can include, but not be limited to:

• Reviewing reported and forecasted weather for the route of flight to identify possible areas of severe turbulence and/or mountain wave activity considerations.
• Verifying that the aircraft is currently approved for RVSM operations. This can be accomplished by ensuring that the placard “RVSM CERTIFIED” is installed and contains no deferral sticker.
• Reviewing any maintenance log actions or MEL issues that would invalidate RVSM certification or capability.
• During the external preflight inspection, you should pay particular attention to the aircraft fuselage skin and areas around or influencing air flow around the static port areas for any potential air flow disruptions.
• During the internal checks, ensure that both primary altimeters are set to the local QNH (field elevation), and that they indicate within 75 feet of the current field location revelation. Additionally, both primary altimeters must indicate within 75 feet of each other (this requirement is only for aircraft that will operate in the RVSM environment).

If the AFCS or autopilot is deferred, then the maximum cruise altitude is FL280. This is an RVSM limitation and not an airplane limitation.

Prior to Entry into RVSM Airspace

As you climb towards FL290 and prior to entering into RVSM airspace, you should check the following items:

• Both primary altimeter systems are operational (captain and co-pilot).
• The transponder is selected to the same side as the autopilot/flight control system is selected to. This ensures that the altitude that is being maintained is the altitude that is being reported to ATC.
• The Automatic Flight Control System (AFCS) or autopilot is operational.
• The altitude alerting system is operational.

During Flight in RVSM Airspace

During flight within RVSM airspace, you should continually monitor altitude indications, and note any deviations or indications from assigned and selected altitudes that exceed 200 feet. If a crew member identifies any problems that effect RVSM capability, you must notify ATC immediately for resolution of non RVSM capability.

Furthermore, when climbing or descending to an altitude, you need to ensure that altitude capture does not exceed 150 feet from selected altitude by either overshoot or undershoot. If it does, consider taking immediate action by disengaging the autopilot and correcting for the altitude deviation. But, before you do that, I would monitor the altitude and see if the airplane is correcting for the deviation.

It is also important that you exercise caution and maintain a heightened situational awareness when climbing or descending within 2,000 feet vertically and 5 nautical miles of other traffic. It is recommended that you climb or descent at rates that do not exceed 1,000 feet per minute to minimize the possible triggering of a TCAS TA or RA event. However, if ATC asks you to descend faster than 1,000 feet per minute, you are obliged to comply, just monitor the aircraft around you.

Also, while flying consider crossing traffic. On occasion, while crossing below and perpendicular to a heavy aircraft, their wake tossed us around. Consider descending to avoid the possible problem or ask for a vector away from the crossing traffics path. 

A good habit to get into is at intervals of approximately one hour, a cross-check of the primary altimeters should be accomplished, and they should agree to within +200 feet of each other. If the error between the primary altimeters exceeds this value, you must advise ATC of the possible failure of one of the primary altimeter systems, and the possible impact of continuing operations within RVSM airspace.

Post Flight

Just as you need to do a thorough walk around after each flight, when flying in RVSM there are a few more things to look for after the flight:

• You should write up and notify maintenance control of any failure of RVSM required systems and/or indication errors observed during flight that would affect RVSM certification capability.
• In making the maintenance log book entries against malfunctions in the height keeping systems, the you should provide as much detail to describe the malfunction/error to enable maintenance to effectively troubleshoot and repair the system.

The following information would be helpful, where appropriate, to troubleshoot the failure/error observed: 

1. Both primary altimeter readings
2. Standby altimeter reading.
3. Altitude selector setting.
4. Altimeter(s) sub-scale settings/readings.
5. Autopilot used to control the aircraft. Any differences if the alternate system was selected.
6. Transponder selected to provide altitude information to ATC. Any differences noted if alternate transponder is selected.
7. Any differences noted when directed by the QRH to select different air data computers, static sources, etc.

Conclusion

So there you have it. RVSM explained.

RVSM is a wonderful thing for those of us that fly at those altitudes. We have more options when it comes to turbulence, winds aloft, weather and routing, allowing us to take advantage smoother air and better winds when possible, which ultimately helps us save fuel and give our passengers a better, more comfortable flying experience.

Occasionally, too, we get a terrific sight as an airplane flies past us only 1000 feet below or above us.

I hope you found this article interesting. If you liked it, please consider sharing it with a friend using one of the buttons below. Also don’t forget to sign up for the RSS Feed or email updates. You can find the links in the top right hand corner of this page.

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To Your Flying Success…

Jeffrey

Jeffrey is a captain at a regional airline and flies the CRJ-200, CRJ-700, and the CRJ-900. He has over 4000 hrs of flying experience in many different airplanes and is a Gold Seal flight instructor to his credit. He has recently written “The CRJ200 Quicknote Study Guide” that simplifies the systems of the CRJ200 into a easy-to-understand, downloadable eBook. Click here to get your copy today!