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MSP Noise Programs

Fleet Evolution

Since the advent of the Jet Age in the late sixties, and passage of the Airline Deregulation Act in 1978 by the U.S. Congress, airline traffic has been on a steady climb in the United States. MSP has seen major growth in air traffic over the past 27 years. In 2005 the total number of operations at MSP was 531,947, which represents approximately twice the level of annual operations in 1978.

Review of operational trends and related noise impacts at MSP over the last 20 years shows apparent fundamental changes in the number of operations, aircraft fleetmix and the related noise impacts at MSP.

The 1990s saw a transition in the methodologies and proposed strategies for addressing airport noise. Increased technological advances in the areas of aircraft engines, airport facilities and navigational systems provided new alternatives to the traditional airport noise abatement methodology. In the area of aircraft engines, a new philosophy emerged centered around addressing the source (aircraft engines) of aircraft noise.

The stage designation of an aircraft refers to the noise generated by a specific engine on a specific airframe. Stage 3 aircraft employ some type of noise reducing technology or design. In contrast, Stage 2 aircraft are typically older aircraft and are louder than Stage 3 aircraft. The FAA has determined that roughly three to five Stage 3 operations cumulatively equal the noise level of one Stage 2 aircraft. Although the MAC has no authority over decisions related to the type of aircraft that operate at MSP, the MAC does, and will continue to, support and encourage any efforts by the airlines to utilize the quietest aircraft technologies available to meet the traveling demands of the public.

Following enactment of the provisions of ANCA (requiring the phase out of all Stage 2 aircraft over 75,000 lbs. in the U.S. by January 1, 2000), several companies developed applications to modify Stage 2 aircraft to meet the Stage 3 noise requirement. Typically referred to as hushkitting, the modifications to the older aircraft made them Stage 3 compliant. However, these aircraft still represented among the loudest aircraft in the post-January 1, 2000 airline fleetmix in the United States. Some airlines, including Northwest Airlines, made fleetmix decisions that focused on hushkitting older aircraft, as opposed to buying new aircraft to replace the older models. The decision was seen by many as a way to avoid additional operating expenses through the continued use of older aircraft owned by the airlines. In the case of Northwest Airlines this translated into the hushkitting of McDonnell Douglas DC-9 and Boeing B-727 aircraft to meet the Stage 3 requirement. The continued use of hushkitted aircraft at MSP has been the predominant driver of the noise impacts around the airport. However, as a result of higher operations costs, the number of Stage 3 hushkitted aircraft are on a significant decline at MSP.

The highest number of monthly Stage 2/Stage 3 hushkit operations at MSP was 16,132 in September 1996. However, following the events of 9/11 the number of monthly Stage 3 hushkit operations dropped off significantly at MSP, and has never returned to pre-9/11 levels. In September 2001, the number of Stage 3 hushkit operations dropped to 9,450 and has continued to decline. More recently, following the Northwest Airlines bankruptcy filing, Stage 3 hushkit operations dropped to an all-time low of 4,152 total operations in November 2007. At the same time older hushkit aircraft operations are reducing, the use of newer and quieter manufactured Stage 3 aircraft is on the rise. The best example at MSP of the newer aircraft that are increasing in use are the Airbus A320/319, Canadair Regional Jets – CRJs, Boeing B757-200/300 and Boeing B737-800, replacing older hushkitted Stage 3 aircraft like the DC9 and B727.

Based on over 113,000 aircraft noise events, the monitored noise levels provide a clear distinction between the noise emission levels characteristic of hushkitted aircraft and the noise benefit provided by newer technology manufactured Stage 3 aircraft. When comparing the DC9 hushkitted aircraft to the CRJ-200 regional jet (the CRJ one of the replacement aircraft for the older DC9s at MSP), 43 CRJ operations would be the same noise impact as one DC9 operation. The CRJ-200 aircraft represents newer technology engine noise emission levels.

From 1995 (456,265 total MSP operations) to 2005 (531,947 total MSP operations) annual aircraft DNL as monitored at MSP have decreased. For example, in many communities around MSP, DNL decreases ranged from 1.1 dB in the City of Minneapolis to 14 dB in the City of Richfield. Additionally, from 1995 to 2005 aircraft DNL impacts and significant single event aircraft noise levels have been decreasing around MSP.

From 2002 to 2006 the total number of single and multi-family dwellings in the 60+ DNL contour reduced from 33,466 in 2002 to 17,353 in 2006, a reduction of 48.1%. Dwellings within the 60, 65 and 70 DNLs reduced by 12,554 (49.4%), 2,749 (40.0%), and 810 (68.5%), respectively.

Although the MAC has no control over aircraft fleetmix decisions at MSP, considering the impact that the aircraft fleetmix has on the noise environment around the airport, the MAC will continue to closely follow aircraft fleetmix developments and remains keenly aware of the importance of new aircraft technologies in reducing noise levels around the airport.

The modernization of aircraft fleets around the world is a positive development not only in areas like noise reduction, but also in the area of air quality.

The highest number of monthly Stage 2/Stage 3 hushkit operations at MSP was 16,132 in September 1996. However, following the events of 9/11, and other significant airlines events, the number of monthly Stage 3 hushkit operations dropped off significantly at MSP, to an all-time low of 4,152 total operations in November 2007. At the same time older hushkit aircraft operations are reducing, the use of newer and quieter manufactured Stage 3 aircraft is on the rise. The best example at MSP of the newer aircraft that are increasing in use are the Airbus A320/319, Canadair Regional Jets – CRJs, Boeing B757-200/300 and Boeing B737-800, replacing older hushkitted Stage 3 aircraft like the DC9 and B727.

As calculated below, based on the IPCC Guidelines for National Greenhouse Gas Inventories: Reference Manual data for Landing and Take Off Cycles (LTO), the reduction in greenhouse gas Carbon Dioxide emissions associated with these aircraft transitions are significant.

At MSP the DC9 aircraft, which has a kg/LTO Carbon Dioxide emissions value of 22.24 per passenger, is being replaced by aircraft such as the A320 which has a kg/LTO Carbon Dioxide emissions value of 17.29 per passenger (22.2% reduction per passenger in Carbon Dioxide emissions). The B727 aircraft, which has a kg/LTO Carbon Dioxide emissions value of 29.89 per passenger, is being replaced by aircraft such as the B757 which has a kg/LTO Carbon Dioxide emissions value of 22.58 (24.5% reduction in Carbon Dioxide emissions per passenger). The other chemical components of aircraft emissions, such as NOx, are less than 1% of the total aircraft emission composition.

Although the MAC has no control over aircraft fleetmix decisions at MSP, considering that aircraft are the largest source of emissions at the airport, MAC will continue to support and encourage any efforts by the airlines to utilize aircraft technologies that produce the least amount of greenhouse gas emissions while meeting the traveling demands of the public.