Frequently Asked Questions
Thank you for your interest in General Mitchell International Airport (GMIA).
To help you obtain information as quickly as possible, we have compiled this list of questions frequently asked by airport neighbors. If you still have questions after reviewing this information, please feel free to contact us via email at firstname.lastname@example.org.
What are the characteristics of sound?
Sound is a physical phenomenon consisting of minute vibrations which travel through a medium, such as air, and are sensed by the human ear.
The measurement and human perception of sound involves two basic physical characteristics:
- Intensity: Measure of the acoustic energy of the sound vibrations, expressed in terms of sound pressure (Volume)
- Frequency: Number of times per second the air vibrates or oscillates (Pitch)
What is noise?
Noise is regarded as unwanted sound. It is a sound that disturbs our routine activities and infringes on our enjoyment of peace and quiet.
How are aircraft noise levels determined?
The day/night average sound level or “DNL” is the FAA’s standard measure to quantify aircraft noise exposure in the vicinity of an airport. The number of flights, aircraft types, and flight tracks are critical inputs to the calculation. The DNL represents the average sound exposure measured in decibels during a 24-hour period and does not represent the sound level for a specific noise event.
What is a noise contour?
A noise contour is an area on a map that defines levels of aircraft noise exposure. Noise contours of specific DNL levels are developed using the FAA’s Integrated Noise Model (INM). Airport-specific data used in the INM model to develop the contour will result in the depiction of noise exposure in the vicinity of an airport. Airport-specific data used in the INM include: Average Daily Operations, Aircraft Fleet Mix, Runway Use, Flight Corridors and Usage, Departure Destinations and Day/Night Use.The 65 decibel DNL contour is generally identified by federal guidelines as the “threshold of significance” for aviation and other sources of community noise. You can view Mitchell Airport's Noise Study Maps here.
What is a Federal Aviation Regulation (FAR) Part 150 Noise Compatibility Study and what is its purpose?
A FAR Part 150 Noise Compatibility Study is a plan initiated by airports to develop and recommend actions to help reduce the impact of aircraft noise in neighborhoods surrounding airports. Although airports are not required to conduct FAR Part 150 Studies, voluntary participation in the Study entitles Milwaukee County’s GMIA to receive federal funding to implement FAA-approved airport noise programs.
What is a Noise Abatement Procedure?
A noise abatement procedure is a recommended flight path aircraft follow to minimize noise over a populated area. Because this is a recommended procedure, pilots may decline to follow it due to safety concerns or operating limitations. For some noise abatement procedures, a pilot must be able to see specific visual cues. If the visual cues are not visible, the pilot will not be able to safely follow the noise abatement procedure. Other procedures rely on navigational equipment capabilities.
What determines which direction aircraft will fly in and out of the airport and use of runway?
Aircraft generally take off and land into the wind. Therefore, wind direction and other weather factors determine runway utilization.
Can the GMIA Noise Office change flight paths?
No. The Federal Aviation Administration (FAA) controls and regulates the airspace. Any change in departure or arrival flight paths must be approved and implemented by the FAA. The GMIA Noise Management Office is here, in large part, to help communicate between the airport, airlines, FAA and the local community.
Who tells the pilots where and when to turn?
Commercial pilots fly prescribed routes and general aviation pilots also fly prescribed routes as well as visual flight procedures (VFR) to and from GMIA as instructed by air traffic controllers. The FAA is responsible for managing Milwaukee’s airspace and for ensuring the safe and expeditious flow of traffic. Airport Operations is responsible for operating and maintaining airport facilities and for ensuring that runways (and taxiways and other facilities) are in good working conditions, meet FAA regulations and are available for use.
Why do flight paths change?
There are many reasons, sometimes beyond the airline's control, why an aircraft may fly out of its typical flight path. These include air traffic conflicts, weather, air traffic control directives, safety considerations, aircraft performance, runway work and pilot technique.
Why do aircraft sound louder at night than they do during the day?
Nighttime noise events seem louder because the ambient noise is lower. More noise events may be noticed at night compared to daytime hours when there exists a higher ambient noise level.
Why do some aircraft seem louder than others?
Aircraft operating at GMIA have a diverse range of noise levels. These noise levels primarily depend on the type of engine used by the aircraft, the size of the aircraft and whether the aircraft is taxiing on the airfield, landing or taking off. The newest so called "full Stage 3" aircraft tend to be the quietest aircraft in the fleet. Aircraft that were originally Stage 2 compliant but retrofitted to meet Stage 3 regulations tend to be the loudest.
Which is quieter - an arriving or departing aircraft?
Arriving aircraft at low altitudes are generally quieter than departures of the same aircraft type because this mode of flight requires much less engine power. However, close to the airport, the relative quietness of an arrival may be offset by the fact that they are typically lower in altitude than departures over the same location.
Who should I contact about low-flying planes?
Please contact the FAA’s Flight Standards District Office (FSDO) at 414-486-2920.
What happens when I submit a noise complaint?
The GMIA Noise Management Office investigates all out of the ordinary noise events and aircraft activity. When appropriate, staff will follow up with aircraft operators and/or the FAA to investigate what action can be taken to minimize noise in the future.
Does GMIA or Milwaukee County have curfews or restrictions similar to those at other Airports?
The airport and County have put into place many cooperative measures for noise abatement procedures, including use of the ground run-up enclosure for engine maintenance runups and noise abatement departure and arrival procedures between 11 p.m. and 6 a.m. Monday through Friday and 10 p.m. and 7 a.m. on weekends and holidays. These procedures are voluntary on the part of the pilot and the FAA tower, subject to weather and traffic volume. Aircraft arrivals and departures are permitted 24 hours a day.