The Duncan Download Blog: Business Aviation Advice & Observations

Is there a way to access Hawker 800 / 800XP avionics boxes at a remote location without disturbing RVSM critical areas? Most definitely. Yes.

Protecting Hawker RVSM Certification

Restoring the RVSM certification for Hawker 800 / 800XP aircraft in-the-field is not for the faint of heart. Talk to the many operators who have landed in remote locations for AOG avionics servicing, only to discover that those locations were not capable of restoring the aircraft's RVSM certification.

Duncan Aviation explores the issues surrounding RVSM recertification in its updated field guide “Sealing Pandora’s Box,” with details on how to avoid disturbing RVSM critical areas when accessing the avionics nose bay.

For Hawker 800 series aircraft, the nose avionics bay access panels are located in a RVSM critical area. This critical area has very tight tolerances for gaps and skin variances as called out by the aircraft’s RVSM Service Bulletin.

This significantly increases the ground time required for maintenance and troubleshooting on flight guidance and Electronic Flight Instrument System (EFIS) systems, negatively impacting flight schedules.

Even the simple replacement of a Flight Guidance Computer results in the recertification of the RVSM critical zone, including any rework of that area required to meet OEM specifications.

The Hawker 800 / 800XP avionics bay door panels have become the modern aviator’s equivalent to Pandora’s Box.

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Contributed by Randy Dill, RVSM GMU Flight Monitor

In 1988, the International Civil Aviation Organization (ICAO) completed a study that concluded the safe implementation of separation between aircraft at flight levels above 290 from the standard 2,000-ft to 1,000-ft as technically feasible. Reduced Vertical Separation Minimum (RVSM) was subsequently implemented and today the 1,000-ft separation is the global standard.

The United States implemented RVSM in January of 2005 from flight level 290–410 thereby, increasing airspace capacity, and allowing aircraft to fly more optimum profiles and gain fuel savings. As a part of the implementation, aircraft participating in the program were to be monitored to identify aircraft not performing to RVSM standards and identify adverse altitude holding trends in aircraft types.

On November 18, 2010, in conjunction with internationally agreed changes to ICAO Annex 6, operators issued a U.S. RVSM authorization approval will have their height keeping performance monitored every two years or 1,000 hours, whichever is longer from the date of last monitoring.

With this monitoring standard in effect, many aircraft will soon be coming due to for their RVSM monitoring again. Two major monitoring options are available.

AGHME Monitoring

There are seven Aircraft Geometric Height Measurement Element (AGHME) stations located throughout United States and Canada. Operators with aircraft currently outfitted with Mode S transponders are able to overfly these stations for RVSM monitoring at no cost.

The downside to AGHME stations is they are only able to read aircraft with Mode S transponders and will provide no physical evidence of the flight to the operator other than a posting on the FAA website. Currently AGHME coverage is in the southern half of the U.S and the far west is very limited.

GMU Monitoring

The second option for RVSM monitoring is to use the GMU, or GPS-Based Monitoring Unit. There is a fee to this option as it requires a trained technician to ride aboard the aircraft for 30 minutes in RVSM airspace to monitor and record the altitude keeping capabilities with GPS antennas in the side windows. This is the preferred RVSM monitoring option for aircraft with Mode C transponders.  

An advantage of the GMU flight monitoring option is that it can be performed anywhere in the U.S. and operators are provided a copy of the results as well as a posting on the FAA website.

To control costs, many operators request a technician ride and monitor the aircraft during a scheduled flight then return via commercial airline. Some operators with Mode S transponders also opt for the GMU monitoring method even though there is a fee, as a better option than flying a long distance to overfly an AGHME station.

It is not unusual for several operators in a specific geographic area to coordinate and schedule GMU flights on multiple aircraft at the same time, utilizing the trained RVSM technician and sharing expenses.

Duncan Aviation RVSM Monitoring

With two GMU monitoring units located in Lincoln, Nebraska, and Ft. Lauderdale, Florida, Duncan Aviation has performed an estimated 700 GMU monitoring flights since the start of RVSM in 2003. The Ft. Lauderdale facility has the capability of traveling outside U.S. airspace to perform GMU flights.

To schedule a GMU RVSM monitoring flight, request a quote or to get more information, contact Duncan Aviation RVSM monitoring experts, Randy Dill  and Brian Redondo. We would be glad to provide you a solution for your monitoring requirements.

Randy Dill   RVSM GMU Flight Monitor Lincoln, Nebraska

Brian Redondo   Avionics Satellite Manager  Fort Lauderale, Florida

Contributed by Jeff King, Chief Inspector - Components/Satellites

Duncan Aviation technicians hook up the RVSM test-set to the right-side static ports to test the copilot's RVSM system.

Though nearly every general aviation aircraft has received RVSM certification, maintaining that certification has become a cloudy process for operators. With the new Height Monitoring Requirements now a reality, operators continue to have questions. Here is a recent question from a Directory Maintenance about long-term RVSM monitoring.

What if my aircraft has the factory RVSM STC, do I still have to have the flight check every two years?

The answer is yes. No matter how the RVSM solution was installed on your aircraft, you are still required to meet the Height Monitoring requirement.

The guidance says every two years or 1000 flight hours, whichever is greatest. So if you fly less than the 1,000 hours in the two year period, you can continue to meet the height monitoring requirement until you reach the 1,000 hour limit.

Meeting Height Monitoring Requirements

Height Monitoring Requirements are easily met if your aircraft is equipped with Mode S transponders. With Mode C transponders you will need to have a qualified technician come on board and perform the monitoring.

For more information, read the regulatory Requirements for RVSM Maintenance Intelligence article, or download the Straight Talk About RVSM booklet.

Jeff King is the Chief Inspector of Duncan Aviation's Component Solutions and Avionics Satellite Network. He specializes in FAA regulatory compliance for repair stations and aircraft maintenance professionals. His aviation career began in 1987.

Contributed by Randy Dill, RVSM GMU Flight Monitor

In a FAA Reduced Vertical Separation Minimum (RVSM) Notam dated March 9, 2011, aircraft of operators authorized to use RVSM airspace must conduct monitoring every two years or within 1,000 flight hours per aircraft, whichever period is longer. This requirement is a follow-up to the RVSM regulation implemented on January 20, 2005, in the United States and parts of Canada and Mexico. It became applicable on May 18, 2011, and operators have until November 18, 2012, to comply.

The majority of aircraft that fly in RVSM airspace, Flight Level 290 through Flight Level 410, must meet RVSM minimum monitoring requirements, meaning aircraft that fly within that airspace will be separated by a distance of 1,000 feet. To accomplish this, aircraft are monitored to ensure the equipment on the aircraft (FMS, autopilot, etc.), keep the aircraft at their respective assigned altitudes.

RVSM Monitoring Methods

If the aircraft is Mode S, it can fly over ground-based stations (AGHME) and have their altitude recorded and then published to the FAA RVSM website. There is no cost to the operator for this method of monitoring; however, they will not receive any form of documentation of the results.

Mode C aircraft, or Mode S if the operator prefers, must be monitored by a qualified technician using a GMU (GPS-Based Monitoring Unit) while aboard the aircraft. They track the altitude for a minimum of 30 minutes while flying at altitude. Both the customer and their local FAA representatives receive physical data from these flights, as well as the results being published on the FAA website.

Duncan Aviation has been monitoring RVSM aircraft since 2004. Many of the aircraft we’ve monitored are now due to be retested before the November deadline. More information on regulatory Requirements for RVSM Maintenance is available in the Duncan Aviation Intelligence Newsletter. 

For more information about scheduling your aircraft RVSM Flight Monitoring, contact:

Battle Creek, Michigan (BTL)

• Adrian Chene, Avionics Installation Tech Rep
• Patrick Mapes, Assistant Manager Avionics Install

Lincoln, Nebraska (LNK)

• Eric Caler, RVSM GMU Flight Monitor / Scheduler
• Randy Dill, RVSM GMU Flight Monitor
• Rich Kempston, Assistant Manager Avionics Install

Randy Dill is a qualified RVSM GMU Flight Monitor and a CNC Fabrications Specialist at Duncan Aviation's Lincoln, Neb., facility. He specializes in manufacturing custom aircraft parts. His aviation career began in 1986.