ARW

120-Day Re-Assessment Plan

Site Visits

Background

A team visited the Bert Mooney Field (BTM), located in Butte, MT, on May 7, 1997. BTM is a non-towered, Service Level D airport and is attended dawn to dusk. The ASOS was installed in October, 1993 and was scheduled to be commissioned in March, 1997 (the commissioning has not been re-scheduled). The FAA contract for weather observations will be canceled when the ASOS is commissioned.

Instrument flight rules traffic is controlled by the Salt Lake City Air Route Traffic Control Center which has a remote transmitter/receiver located on the field for clearance delivery and flight plan cancellation. Great Falls Automated Flight Service Station provides pre-flight weather briefings and Notices to Airmen issuance services.

The FAA Airport Master Record dated August 1, 1996 indicates that a total of 39 aircraft are based at the Butte airport. Operations for the 12 months ending August 1, 1996 totaled 21,120 including 4,530 air carrier, 7,700 air taxi, 2,400 general aviation local, 6,100 general aviation transit, and 390 military.

Mountains surround Butte on three sides. Within a few miles to the east and north, the height of the terrain increases more than 3,000 feet above field elevation. To the south, the increase is more gradual. A glacial valley extends west-northwest toward Missoula. Because of the rapid increase in elevation east of Butte, the VORTAC (CPN) serving the airport is located approximately 12 statute miles west of the airport. The CPN VORTAC forms part of V86, the major east-west low-level route in western Montana. V86 passes through the Homestake Pass, which is located about seven miles west of the airport. Decisions concerning VFR on this route are dependent on the Butte weather report.

The FAA Regional Office has received congressional correspondence regarding the inadequacy of the ASOS at the Bert Mooney Field. Specifically, the correspondence addresses the lack of freezing rain, thunderstorm or tornado reporting capabilities.

Participants

Airport manager, fixed base operator, Chairman of Montana Aeronautical Commission (Airport Director, Helena Regional Airport), Administrator Meteorological Institute (owner of contract weather observer company), contract weather observer, two Airport Authority Members, Butte Mayor, Board Chairman of Montana Power Company, 35-40 local pilots, and FAA/NWS team.

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.

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.

Several state, city and airport authority officials attended this meeting. An aide to Senator Baucus was present and stated that -

"The Senator would work hard to keep the contract weather observers (at the airport)."

The airport manager and contract weather observer personnel participating in this five-hour meeting displayed a fair level of ASOS functionality. Most users were not aware that the ASOS was transmitting in the test mode or the telephone number to reach the weather report. The contract weather observer is using the ASOS as a sensor array to assist in weather reporting.

The airport manager and the contract weather observer called the responsiveness of the ASOS into question. They stated -

"The ASOS took 10-12 minutes to effect changes to visibility and 30 minutes to effect changes in ceiling."

Specifics were cited about a March snowstorm and a snow squall earlier in the meeting day. The airport manager and the contract weather observer stated -

"The ASOS is too slow in reporting improving conditions to allow users to operate in rapidly changing conditions."

They emphasized the need for weather sensors at other than the landing threshold to facilitate other than an instrument landing system approach to the airport.

Users emphasized the need for augmented weather observations to increase the usability of their facility. The following specific comments were brought to the attention of the team -

"Information is needed on mountain passes to facilitate VFR (visual flight rules) operations."

"Great Falls (Flight Service Station) ASOS is frequently wrong and tower personnel will not override."

"Aviation is of critical, economic importance to Butte and Montana."

Another user supplied this information about the Butte airport -

"BTM has the steepest approach in the country, The ILS (Instrument Landing System) minimums are 1,000 feet and three miles for the high terrain approaches, and there is a 3 ½ degree glide path on ILS."

Pilots stated that -

"In this terrain you don’t want to have to do a missed approach. Having a human observer on site means they can be advised of these conditions; the ASOS does not look at these areas."

Pilots also feel they often have a short window of opportunity to land. Human observers can help aircraft get in when the ASOS takes too long to show improved weather conditions. A Missoula pilot claimed -

"He waited 18 minutes for approach because the ASOS was showing ¼ mile visibility when the tower visibility was 1 ½ miles."

Other problems stated by the users were that -

"The ASOS does not report distant remarks or information on passes and mountain obstructions."

The need for a definition of "Official Weather" was raised as an issue.

Users stated that -

"A local briefer relays good information on all areas of approach."

"Escape routes may be shut down by weather and pilots would have no way of knowing this if ASOS was stand alone. This is very important for circle to land approaches when the briefer can give information on which way to circle."

Another pilot stated -

"Air Carriers are not allowed to land when the ASOS says weather is below minimum even though pilots can see the runway. Alaska is allowed to vary from this plan, why can’t Montana?"

Another comment was that -

"Western Montana has unique weather much like Alaska, and Montana wants the same variations to procedures as those allowed Alaska." No specifics were provided.

During meeting discussions, it was noted that the contract weather observer receives payment from the airport to provide additional services previously provided by Flight Service Station personnel. This included providing "enhanced UNICOM" information for arrivals and departures, relaying weather over the FAA provided radio on 123.65, monitoring airport ground traffic, maintaining limited climatology data, initiating crash-fire-rescue actions, and operating airport lighting.

There was common concern about the response time for repairs and the availability of support personnel. Snow removal with a snow blower impacted ASOS visibility and ceiling reports to the extent that they were totally unreliable while the snow removal operations were being conducted. This resulted in ASOS reported ceilings and visibility that were lower than airport minimums. Snow removal was conducted at all hours during the winter season and took approximately three hours to complete a sweep of the entire airport.

After having been promised "equal to or better service" by the FAA after the closure of the Flight Service Station in July, 1995, there is a great deal of resentment over the potential termination of the contract weather observer upon ASOS commissioning.

Another attendee stated -

"The AAAE (American Association of Airport Executives) group was not invited to participate in developing the Service Standards."

The airport manager reported that -

Information Provided

Members of the team attempted to provide information on the ASOS Service Standards, operations, maintenance call back, and other associated issues. The airport manager attempted to block/quell any discussions on these issues.

Issues Identified

The human interface, with the flexibility provided by the human observer, appears to be the major issue at Butte. Slow response time to rapidly changing conditions was cited as a major flaw in using the ASOS as a stand-alone system. The lack of off-airport remarks for mountain passes and reporting of localized phenomena for other approaches to the airport and its runways was emphasized. Airport management and users feel the ASOS’s inability to provide this type of information will decrease the airport’s usability, create fiscal hardship, and create an unsafe flying environment by disrupting accepted practices used at the airport. Maintenance issues were the response time to ASOS outages, the availability of technicians, and the overall impact of equipment outages to the airport users.

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