Noise from an aircraft is loudest underneath its flight track, so knowing the paths flown by various types of aircraft is key to understanding noise patterns.
The airport has three runways, numbered at each end according to the approximate compass heading:
Almost all commercial airliners and military fighters use Runway 18/36, which accounts for about 70 percent of all aircraft operations in and out of the airport. The other two runways are mainly used by smaller business jets and small general-aviation aircraft.
Fighter jets make up about 15 to 20 percent of airport aircraft operations, mostly from the local 115th Fighter Wing of the Wisconsin Air National Guard. Fighter jets almost exclusively use the main north/south runway (18/36), both because the jets need a longer runway and because it has a cable arresting system for stopping the jets in case of a rejected take-off or an emergency landing. Rarely, fighters use Runway 03/21, which has a less capable cable-arrest system.
A standing military noise-abatement "NOTAM" for the airport directs fighters and other military aircraft to depart to the north whenever possible. If a south departure is required, fighters are directed to turn to a heading of 140 degrees or less. Local fighters typically climb quickly after departure to help mitigate noise over the area.
Fighter jets that do not follow the local military NOTAM departure procedures are almost always itinerant aircraft from other bases and are likely unfamiliar with the local noise-abatement procedures.
About 60 percent of arriving fighter jets execute a military-style "overhead" approach. This involves flying at high speed directly over the center of the airport about 2,500 feet above the ground, then executing a circling 360 degree descent to the runway. The Madison military NOTAM requires overhead approaches to break to the west unless otherwise directed by air traffic control. This puts the aircraft over Maple Bluff and other areas along the eastern shore of Lake Mendota. Fighters often execute this approach in formation arrivals of 2 to 4 aircraft, which break to the west at different points in order to create spacing for landing.
About a third of fighter-jet arrivals are straight-in approaches similar to commercial airliners, mainly when poor weather does not allow for a visual overhead approach. The shallower approach angle for straight-in arrivals requires a higher power setting (and thus more noise) than overhead approaches, but also avoids the areas to the west of the airport.
A small percentage of arriving fighter jets execute an approach similar to a standard "traffic pattern" approach used by smaller general aviation aircraft. This involves flying downwind parallel to the runway before turning 180 degrees and descending to land into the wind.
Fighter jets are mostly invisible to the MSNSound system because they do not broadcast ADS-B data. However, TIS-B rebroadcasts of radar data are picked up by flight-tracking sites such as ADS-B Exchange. These are not identified as fighter jets per se, but are readily identifiable as such based on their high speed and rapid climb/descent rates. The Fighter-Jet Flight Track Explorer allows visual exploration of local fighter jet flight paths based on more than 2,000 tracks downloaded from ADS-B Exchange. Although these tracks are typically individually incomplete, in aggregate they provide a useful view of the routes fighter jet take in and out of the airport.
Data Source: ADS-B Exchange
Large jets are here defined as turbofan aircraft with a maximum gross take-off weight of 20,000 pounds or more. This includes the larger commercial airline aircraft that operate in and out of the airport, such as the Boeing 737, Airbus A319, Embraer ERJ-170 and Bombardier CL-600. A few larger business jets are also included in this category, as well as the occasional visiting military transport aircraft, such as the Boeing C-17A.
Most large jets depart using the main north-south runway (Runway 18/36), then head towards fixed navigational waypoints in the general direction of their destination shortly after departure. Departing airliners generally climb quickly to 4,000 feet above the airport elevation shortly after departure: this significantly reduces the noise impacts beyond about 5 miles from the airport.
In contrast to the dispersed nature of departing large jets, large-jet arrivals are highly concentrated along tracks that align with the airport runways. This is because commercial airliners practice stabilized-approach procedures that call for lining up with the intended runway 5 miles or more away from the airport to avoid last-minute maneuvering during landing. Homes near the extended runway centerline for especially the heavily-trafficked Runway 18/36 thus experience more noise from many daily large-jet arrivals.
Small jets (i.e., turbofan-powered aircraft with a maximum gross take-off weight of less than 20,000 lbs.) include general-aviation business jets such as various Learjet and Cessna Citation models as well as smaller commercial aircraft such as the Embraer ERJ-145. These aircraft are more likely to utilize the airport’s smaller two runways for departures and arrivals.
Large prop aircraft are defined here as propellor-driven aircraft with a maximum gross take-off weight of at least 12,500 pounds or having seating for 15 or more people. The most common aircraft in this category at the airport are the Pilatus PC-12, Shorts 360 and the Beech Super King Air, with the latter including its military equivalent, the Beech C-12 Huron. Lockheed Martin KC-130 military refueling tankers also occasionally operate in and out of the airport as well.
Small propellor-driven aircraft are those with a maximum gross take-off weight of less than 12,500 pounds and fewer than 15 seats. By count, this category comprises the greatest number of aircraft operating in the Madison area, comprising all manner of light single- and twin-engine general aviation aircraft such as the familiar Cessna 172, Piper Cherokee and Piper Twin Comanche.
Flight tracks for these aircraft show a fair amount of circuit pattern work and touch-and-go landing practice at the Madison airport and at the nearby Morey Airfield in Middleton.
Civilian helicopter traffic in the Madison area mostly consists of Med Flight aircraft operating in and out of UW Hospital or Meriter Hospital. These aircraft often refuel at the Madison airport.
Military helicopter traffic is almost entirely Sikorsky UH-60 Black Hawk aircraft for the Wisconsin Army National Guard (1st Battalion, 147th Aviation Regiment) based at Truax field.
