ARW
120-Day Re-Assessment Plan
Site Visits
2.3.7 Mission Field, Livingston, MT
Background
A team visited Mission Field (LVM), located 6 miles west of Livingston, MT, on May 8, 1997. LVM is a non-towered, Service Level D airport. The ASOS was scheduled to be commissioned in March, 1997 but has been delayed pending the outcome of the re-assessment. The FAA contract for the provision of weather observations for 16 hours a day, is to be canceled concurrent with the ASOS commissioning.
IFR traffic is controlled by the Salt Lake City Air Route Traffic Control Center that 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 Great Falls Automated Flight Service Station.
Data from the FAA Airport Master Record dated September 12, 1996 indicates that a total of 12 aircraft are based at the Livingston airport. Operations for the 12 months ending September 12, 1996 totaled 3,420 including 200 air taxi, 2,200 general aviation local, 1,000 general aviation transit, and 20 military.
Livingston is located approximately six miles west of the city on a butte. The Yellowstone River valley comes between two north-south mountain ranges and turns east at Livingston. One of the ranges ends at a 9,000-foot peak about seven miles south of the airport. The other range, the Bridgers Mountains, continues all the way to Canada. Adverse weather often builds on either side of the Bridgers for several days at a time, preventing VFR flight through the heavily flown mountain pass connecting Livingston to Bozeman. Livingston is also subject to very high winds from November to February.
The FAA Regional Office has received congressional inquiries expressing concern with the lack of freezing rain, thunderstorm, and tornado detection sensors. In addition, the ASOS ground-to-air transmitter was mentioned as a cause of frequency problems.
Participants
The State Aviation Director, airport manager, Field Director for Senator Baucus, two contract weather observers, five local pilots (four instrument rated), local newspaper reporter, and FAA/NWS team were in attendance.
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 users displayed a limited level of understanding of the ASOS capabilities and functionality.
As part of the re-assessment strategy to perform a "blind comparison" test, system access (i.e., access by the contract weather observers to the computer display of the weather observation generated by the ASOS) was turned off. The "blind comparison" test compared the ASOS observation with the human observation.
Most pilots and users were not aware the ASOS was operating and transmitting in the "test" mode and were not aware of the telephone number to dial-in to the ASOS to receive the weather report. The ground-to-air transmitter was shut down due to interference with local interphone/telephone/intercom systems. The NWS indicated this problem is due to the advanced age of the telephone/UNICOM equipment rather than the ASOS. Pilots stated they could not comment on the accuracy of the system because they were not able to monitor the ASOS while flying.
According to users -
"The siting of the ASOS at the east end of the runway often shows the approach of a system when the other end of the airport is VFR (visual flight rules)."
One of the contract weather observers stated -
"The system incorrectly reported wind direction and velocity (up to15 knots difference reported on peak winds)."
"Precipitation measurements were often inaccurate, showing accumulations as trace when more should have been reported."
"The sea level pressure is often missing."
Other comments by the contract weather observer were that -
"The system frequently reports low weather when the airport has 3 miles visibility, and the system does not have accurate height for clouds."
"Pilots report different ceilings than the ASOS, for example, there was an observed (pilot reported) ceiling at 6,500 feet and ASOS reported 5,000 feet."
Concern was expressed over frequent and extended power interruptions (usually November-February) that in conjunction with the 36 hour maximum response time to outages would result in loss of weather services creating the potential loss of revenue. It was stated that -
"The temperature/dew point was out of service for an extended period of time."
There was user anxiety about -
"Having only one NWS specialist responsible for maintaining all the ASOS sites in Montana!"
A major concerns to the local pilots is the pass from Livingston to Boseman. Their comments were -
"The FAA was made aware of the pass problem in 1994."
"How will pilots be able to get this weather when Livingston goes stand alone?"
"When will this problem be fixed?"
Other problems the users stated with the ASOS are that it does not report off-airport remarks (i.e., status of Bozeman Pass, clouds on ridges, CU building, etc.), visibility beyond ten miles, visibility values, and ceilings above 12,000 feet, which can be critical in an high terrain area (minimum enroute altitudes of 12,000 feet are common in Montana).
Users generally feel more comfortable with a human on site and stated -
"They feel the ASOS is a good tool to be used by the contract weather observers and someday may be "equal or better" than the human observer. They do not want to lose what they have now, weather observation 16 hours daily. ASOS at this site at this time as a stand alone would be premature."
Information Provided
The team provided information on sensor functionality and the sensors to be deployed in the future, such as the Automated Lightning Detection and Reporting System and the freezing precipitation sensor algorithms. Meeting attendees were briefed on the ASOS Service Standards.
Issues Identified
The primary issue at Livingston is the loss of off-airport remarks when the contract weather observer contract is terminated. The manual observers report on weather conditions observed at Bozeman Pass. The variability of the surface wind direction and velocity at different locations on the airport and the frequently missing sea level pressure reports were identified as ASOS sensor-reporting issues. Maintenance issues were the ASOS ground-to-air interference with the telephone system and the UNICOM frequency, the unreliable commercial power and ASOS backup power, and the maintenance response times.