ARW
120-Day Re-Assessment Plan
Site Visits
2.3.11 Ketchikan International Airport, Ketchikan, AK
Background
A team visited the Ketchikan International Airport (KTN) located in Ketchikan, AK, on May 23, 1997. KTN is a non-towered airport with a fully commissioned ASOS and an operational Flight Service Station on the airport. The ASOS was commissioned on December 9, 1996. The airport is designated Service Level C.
The Flight Service Station is responsible for the augmentation, backup and dissemination of the weather report for the KTN airport, including the preparation of the Automatic Terminal Information Service (ATIS) broadcast for the airport. The airport is served by precision and non-precision approaches. The Flight Service Station augments the ASOS with harbor wind information from wind sensors located in the harbor area for arriving and departing seaplane/floatplane operations. These harbor operations account for approximately 85 percent of aircraft operations.
Data from the FAA Airport Master Record as of January 24, 1996 indicates a total of 20 aircraft are based at the Ketchikan airport. Operations for the 12 months ending January 24, 1996 totaled 16,208 including 5,290 air carrier, 9,789 air taxi, 410 general aviation local, 575 general aviation transit, and 144 military.
There are approximately 700-900 operations per day during the summer season, but considerably less during the winter season. This includes communications with aircraft that are flying over the area and not landing at Ketchikan. There is no radar coverage in the area. KTN issues between 2,000 to 2,500 special visual flight rules clearances per year.
Ketchikan lies in the Maritime Climatic zone that includes the Aleutian chain, the Southeast, and the South Central regions of the state. Surrounding mountains and proximity to the ocean are the two factors influencing local aviation weather conditions. Precipitation is heavy (50 to 200 inches per year) and fall and winter bring frequent storms with accompanying high winds. Turbulence is also a common hazard due to orographic and convective influences; the terrain causes turbulence on arrival and departure routes. The coastal areas experience more frequent frontal activity. The chief aviation hazards in the summer are water droplet fog, and in the winter, ice fog, blowing snow, and turbulence. In the spring and fall, icing and frontal zone turbulence are the major aviation hazards. The advection fog during this time may precipitate and cause icing conditions that can be quite severe.
Participants
FAA Air Traffic Manager, representative from Taquan Air Service, representative from Promech, 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 general feeling of all attendees was that the ASOS is an added value for the aviation community. The ASOS location is good and basically provides representative weather. ASOS provides additional capability for the locations.
There is no ground-to-air transmitter associated with the ASOS, and some pilots in the area did not know KTN had an ASOS. The majorities of pilots monitor the Automatic Terminal Information Service or call the Flight Service Station for weather.
The team met the NWS technician at KTN. The technician is based in Juneau and performs preventative maintenance every 90 days on nine sites. The technician reported the following problems with the ASOS -
"Randomly reports rain, is affected by terrain, and reports clear skies even though five inches of rain fell."
"A freezing rain sensor has been installed and appears to be tracking well."
The Air Traffic Manager at Ketchikan said -
"The NWS technician does well at keeping the ASOS maintained and resolves problems within a couple of days of notification."
"He manually augments ASOS during rapid weather changes, MVFR (marginal visual flight rules) to IFR (instrument flight rules) conditions, otherwise the ASOS performs independently very well. In marginal weather, he would prefer to stay in the manual mode and not go back to auto mode because of creating special observations. Currently, the system automatically converts back to the auto mode after three minutes in the manual mode."
Comments solicited on other ASOS sites used by pilots -
"The ASOS is slow to respond to rapidly changing weather and tends to be pessimistic and reports weather conditions lower than defined by humans."
"Hourly observations are seldom accurate due to changing weather. Higher resolution data (one minute observations) would overcome some of this problem."
"In marginal weather, prevailing visibility is usually not correct. For example, ASOS reported 1-1.5 miles visibility when it was actually 5 miles."
The air taxi pilots in attendance said that they fly from Ketchikan to Craig Harbor several times per day in the tourist and fishing season. Craig Harbor is located on a point where it receives all the wind and weather. The closest ASOS location to Craig Harbor is Klawock, but it is about 8 miles away. They stated that -
"ASOS was representative at the site, but they needed the weather at locations 5-15 miles away."
"When they fly through Harris River Pass to get to Craig Harbor, they do not know what weather is occurring in the pass and would like to have an ASOS sensor in the pass."
Other comments received were -
"ASOS allows only three levels of clouds below 12,000 feet, which restricts the human input. Ceilings up to 25k would be beneficial."
"The area has unusual weather conditions. At the same location weather (wind, cloud, and visibility) can be different. At the approach end of the runway, there is a wind shift problem."
"Weather observers can see visibility points at 65 miles while ASOS only reports 10 miles."
"Occasionally thunderstorm/lightning capability is required."
Information Provided
The team provided a basic discussion on ASOS features, abilities, and limitations. A representative from the FAA spoke about digital cameras being used at some locations. After learning that the Flight Service Station manager was unfamiliar with the Service Standards, a copy was provided to him for review. After his review of the standards, the manager stated the KTN Flight Service Station was providing Level A service. Information was provided on the process of establishing the different service levels.
Issues Identified
The main issue identified at the KTN Flight Service Station was the increased workload created by the ASOS generating too many Aviation Selected Special Weather Reports (SPECIs) and not staying in the manual mode. User issues were the ASOS was slow to respond to rapidly changing weather and tended to report weather conditions lower than a human observer would have reported them.