ARW
120-Day Re-Assessment Plan
Site Visits
2.3.9 Wausau Municipal Airport, Wausau, WI
Background
A team visited the Wausau Municipal Airport (AUW) located in Wausau, WI, on May 8, 1997. AUW is a non-towered, Service Level D airport with weather observations provided under a FAA contract. The ASOS was scheduled for commissioning on June 1, 1997, but it has been delayed pending the outcome of the re-assessment. The contract for weather observations is to be canceled concurrent with the ASOS commissioning.
The contract weather observer has a good, unobstructed view of the airfield. The Fixed Base Operator uses the Pan Am Weather Service/Weather Mation User Assistance for additional weather information.
Instrument flight rules arrival and departure traffic for the airport is controlled by the Minneapolis Air Route Traffic Control Center, which has a remote transmitter/receiver located on the field for clearance delivery and flight plan cancellation. Pilot pre-flight weather briefings and Notices to Airmen issuance services are provided by the Automated Flight Service Station located in Green Bay, WI.
Data from the FAA Airport Master Record as of July 16, 1996 indicates a total of 50 aircraft are based at the Wausau airport. Operations for the 12 months ending July 16, 1996 totaled 44,950 including 3,250 air taxi, 32,500 general aviation local, 9,150 general aviation transit, and 50 military.
The airport lies in the Wisconsin River Valley, adjacent to the river. Due to the high moisture level in the immediate vicinity of the airport, fog and low stratus clouds are the major weather problems. Fog may keep the airport in instrument flight rules conditions for extended periods of time during the summer and autumn seasons. In the winter months, freezing precipitation and ice are major concerns. Snow may accumulate and remain on the ground for extended periods of time.
According to the Green Bay Automated Flight Service Station, the river for all practical purposes, surrounds the airport and therefore, when the visibility is down at the ASOS site, the visibility on the entire airport is down. A need for reliable, accurate visibility reports is essential for operation into and out of this airport, especially in the lower ranges (less than one mile).
Participants
Airport manager, Airport Commission Chairman, local pilots, representative from Wausau Paper, Inc., and FAA/NWS team.
Synopsis of User Comments
This section of the report is a record of the comments received during the meetings, interviews and discussions that took place during the site visits. It is intended to present a summary of the input from the users on a particular subject. These comments may include technical inaccuracies and user perceptions that do not reflect actual conditions.
The main issue for discussion was the planned termination of the contract weather observer contract once the ASOS is commissioned. In general, ASOS was judged by the users to be a good idea, however it may not be sufficient for stand-alone use in its current state.
The airport manager of four years who is also an instrument rated pilot, flight instructor, and part-time contract weather observer was the primary spokesperson at this meeting.
The airport manager stated -
"Airport operations may suffer if ASOS data is inaccurate, for example, ASOS reporting IFR (instrument flight rules) conditions when weather is actually VFR (visual flight rules) conditions. This costs the airport and Wausau revenue dollars."
"At airports with no previous weather observations, the ASOS is an excellent addition, and he proposed assigning observers to augment/backup ASOS in other central Wisconsin locations."
The NWS meteorologist-in-charge for the area stated that -
"The Wausau area is difficult to forecast. The contract weather observer is an asset and is able to give good insight and provide additional information. Supplemental sensors would be good if the contract weather observer is terminated."
Representatives from the flight departments of BMB Incorporated, Wausau Finance, and Aqual Finance were not present, however, their concerns were conveyed by the airport manager.
The airport manager indicated that -
"The ASOS has good features, but the system should be fine tuned prior to being the primary weather information source for pilots. At times the ASOS is very accurate. The problem is when you need the ASOS the most, it’s inaccurate."
"The freezing rain sensor may interface with the ASOS. This year the area had a lot of freezing rain."
"The altimeter is off by 20 feet."
"During IFR (instrument flight rules) conditions the ASOS is very inaccurate. Parameters most influenced are ceiling, visibility, the type of precipitation, ambient temperature, and dew point temperature."
"Accuracy and reliability were voiced as issues with the ASOS."
"ASOS has a problem reporting cloud cover. ASOS is directional; ceiling and visibility are the most critical parameters."
"ASOS does not report thunderstorms."
"The ASOS has caused missed approaches."
"The wind sensor freezing up."
"Ceiling observations were unreliable. Local smoke sources often caused lower visibility to be reported by the ASOS when the airport, in general, was clear."
The airport manager indicated that there are 2,500 to 2,800 operations per month at Wausau Airport. There are 40 hangars, 54 based aircraft, 2 corporate flight departments, and 30 flight instructors/students.
The Airport Commission Chairman stated that -
"Improvements to the airport include a Six Year Plan and Part 135 operations. Wausau is planning to revitalize its downtown area under the "Century 2000" project. This would entail construction of a convention center, hotels, malls, and a corporate center that would increase corporate jet usage.
The airport was planning for the construction of an additional hanger. Since the Wausau municipal airport is closer to downtown than the more widely used Central Wisconsin Airport, the new convention center would make the municipal airport more attractive to users. Increased growth and use of the airport might warrant a reclassification of the service level in the future."
A local user proposed -
"It was proposed by the local users that the contract weather observer remains until a revalidation or reclassification of the service level could be accomplished."
Users stated that -
"The maintenance response times are inadequate."
A NWS representative stated that -
"A discontinuity sensor package is needed at the airport."
Another attendee said that -
"Another ASOS was needed at the other end of the other runway. Fog off the lake is a problem. The airport needs a wide weather viewpoint of the airport, ASOS only provides a narrow viewpoint."
The Wausau Paper representative stated that -
"Prior to power reduction (of the transmitter), the ASOS could be received at 110 mile range, but now it cannot be received at long distances. They need ASOS site observations from 110 miles out, (and the) ASOS is available only at 50 miles.".
The airport manager stated that -
"Wausau is the only airport in central Wisconsin with a weather observer. There are three justifications for keeping the contract weather observer:
To verify accuracy and augment ASOS
Weather observers could be dispatched to other local airports when needed
To provide NWS, pilots, and users with accurate weather
Without a human observer, high performance aircraft may use other marginal airports."
Pilots were concerned that the ASOS was off-line. As part of the re-assessment strategy, system access (i.e., access by the contract weather observers to the computer display of the weather observation generated by the ASOS) was shut off in order to conduct a "blind comparison" test. The "blind comparison" test compared the ASOS observation with the human observation. The pilots expressed interest in having the system turned back on as soon as possible even though it is operating in the test mode only.
Information Provided
The process to determine and to change service levels was described. The NWS representative described the ASOS commissioning process. He explained how his office performed quality control activities with regard to ASOS observations and the maintenance process.
The FAA representatives spoke about the Non-Federal Observer Program. The FAA representative agreed to send information on the Non-Federal Observer Program to the airport manager.
Issues Identified
The accuracy of ASOS reports, specifically visibility and ceiling measurements, primarily during IFR conditions, was the main issue at Wausau. The lack of a freezing precipitation sensor and lightning detection equipment is also an issue. The airport manager suggested the retention of the contract weather observers to augment/backup the ASOS until the ASOS is upgraded and additional sensors are installed.