NATCA EASTERN REGION A.S.O.S. REPRESENTATIVE Andrew M. Chalot 4411 W. 12th St PO Box 68 Erie, PA 16505 Cranberry, PA 16319 (814) 833-0841 fax - 833-8416To: Mr Robert L. August, Executive Director, Erie International Airport, Erie, PA Subject: Automated Surface Observing System (ASOS) The National Air Traffic Controllers Association (NATCA) at Erie Tower would like to thank you for the opportunity to express our comments regarding the ASOS at Erie. We appreciate the fact that the Airport Executives have undertaken the effort to investigate this system. Since the first information on ASOS became available to the aviation world, it was praised by the National Weather Service (NWS) as having a 98% accuracy rate. This claim raised doubts, as experience has proven weather to be a very unpredictable and rapidly changing phenomena. Historically, the human weather observer reported weather phenomena existing in a 3-5 statute miles radius from the airport (and more distant phenomena, when visible). They would report weather systems moving toward the airport or visible in any direction from the airport. This hazardous weather would be disseminated to tower personnel and to local citizenry via the media. ASOS, which replaced the human weather observers at Erie, is a machine which reports on an extremely localized area (the ASOS ceilometer utilizes a laser beam that produces a cone-shaped beam that is 25 feet wide at 12,000 feet). It records only that weather which passes directly over the sensors located in an array on the airport proper. Any weather passing beyond this area is not recognized as existing. The ASOS weather report is historical in nature, that is, the weather passing over the sensors is averaged with the weather that had previously passed over the sensors before an averaged weather report is issued. This presents the situation of weather existing directly over the airport and on the final approach that is not yet being considered for weather evaluation. The result is weather reports that do not reflect the actual existing conditions. The Erie controllers were kept aware of the ongoing test results of the ASOS by NATCA National Safety and Technology department members and other aviation industry sources. Several FAA air traffic facilities participated in the ASOS Demonstration and Evaluation project in 1994-95. Reports of the results of this project differed. The NWS and FAA said they were very successful. Controllers who actually participated in the project testing advised the ASOS performed well when the weather was mild; however, when the weather became inclement, the ASOS weather report was constantly lagging behind the actual weather conditions and basically exhibited a substandard performance (non-representative weather report), not acceptable for the needs in a controlled aviation environment. The results of the tests were not very appealing to aviation safety individuals, due mainly to the ASOS performance criteria during changing weather conditions, normally when the air traffic demands on controllers become more complex. These reports created apprehension in the controller workforce with the impemding Erie NWS Station closure and the inevitable takeover of ASOS augmentation and editing duties. Timely and accurate weather information is vital to the safe, orderly and expeditious movement of our nations air traffic. It is the crux of many decisions made in and around airport terminals: the selection of runways, the instrument approach to be utilized, departure and arrival configurations, the release of Aids to Air Navigation (NAVAIDS) to maintenance status and the day to day staffing of air traffic control positions all hinge upon accurate weather information. Many National Transportation Safety Board (NTSB) accident investigations have revealed the need for more enhanced/accurate weather data and rapid dissemination of the same. The implementation of augmented automated weather systems to replace the qualified and experienced weather observers (whose only function is weather reporting) by air traffic personnel, with very little if any prior weather experience, is in direct contradiction to this recommendation. Aircraft must plan a go/no-go decision on executing an instrument approach on the reported visibility, therefore it is extremely important that a correct visibility is being reported in the official weather report. ASOS does not yield this needed accurate product during changing conditions. Erie Tower underwent a full facility evaluation from February 10-14, 1997 by the Washington FAA Air Traffic Evaluations and Investigation Staff (AAT-20). The team noted in their findings : "Rapidly changing conditions were not unusual: e.g., visibility could drop from 10 iles to a half mile with snow showers in a few minutes. This phenomenon occurred while the evaluation team was on site. The ASOS took 10 to 15 minutes to show a drop in visibility and then worked its way down in increments. It still showed visibility decreasing when, in actuality, the snow shower had passed and visibility was back to 10 miles." Another problem not addressed by the controller backed ASOS arrangement is: the visibility is now solely determined from the height of the tower level. With surface based weather observers, the tower visibility and the surface visibility will differ due to the height of the tower cab. In the past the lower of the two visibilities was the controlling visbility. This is no longer a consideration, as the tower level is the controlling factor. In numerous airports across the country, the responsibility of presenting the aviation community an accurate weather report has fallen onto the shoulders of an already overburdened air traffic controller. Inexperienced in weather observations, air traffic controllers now augment or edit (correct) the reports of this weather recording system. Air traffic controllers performed 8 hours of unsupervised computer based instruction, took a test and were qualified by the FAA and NWS to operate as Limited Aviation Weather Reporting Station observers providing vital aviation weather. When air traffic is busy, this augmenting and editing of the ASOS takes a very low priority to the actual job of separating traffic. Controllers primary duty is directed to the separation of air traffic, ground traffic and the asociated duties to accomplish this charge. Airport Managers are well aware of the attention necessary in the monitoring of the airport maintenance equipment (ie: snowplows/blowers, mowers and other vehicles). Attempting to monitor the entire area for weather phenomena that will affect aviation interests and input this data to the ASOS computer (a very slow process) provides an excessive amount of "heads down" time. This added burden presents the controllers with unwelcome distractions to the primary mission. Many non-representative weather reports are disseminated nationwide by this machine when the controllers are too busy with air traffic to issue a corrected report. A large concern to aviation safety oriented individuals, is the inability of ASOS to recognize or report on several of the more important adversities of aviation weather: 1. Activities such as convective thunderstorms, tornadoes, waterspouts and funnel clouds. 2. Damaging precipitation such as hail, ice crystals, snow grains, snow pellets, ice pellets, drizzle and freezing drizzle. 3. Volcanic ash, blowing obstructions (snow, sand, dust, spray), smoke, snowfall, clouds above 12,000 feet and virga (a known indicator of impending Low Level Windshear activities). 4. Operationally significant local variation in visibility or freezing rain. 5. It is very inaccurate in it's reporting of rainfall/snowfall amounts, snow depth and hourly accumulation. 6. Windshear and severe turbulence. It is impossible for controllers at ERI to detect and monitor some of these peripheral weather items because we possess neither the equipment, expertise nor experience to perform this task. These items were always monitored by experienced weather observers, who had undergone extensive training, a rigorous qualification process and possesed years of experience evaluating weather phenomena. They understood the idiosyncrasies of weather and even with their older weather radar systems were able to keep the tower and the general public appraised of impending weather that would effect the local environment. My three years of ASOS research, involvement in discussion groups (with numerous air traffic ASOS augmenters/editors, certified weather observers, contract weather observers and meteorologists) and a complete year of direct ASOS interaction as a air traffic LAWRS observer have lead me to believe a group of new, inexperienced "limited" weather reporters and a machine that consistently lags behind rapidly changing weather activities is not providing "protection" for the aviation communities and general public. Sincerely, Andrew M. Chalot Erie Tower Safety Representative NATCA Eastern Region ASOS Representative |