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C. AIRCRAFT SEEDING OPERATIONS AND MAINTENANCE The cloud base seeding and one cloud-top seeding aircraft type used in 1998 were: (1) 8-single-engine Piper Aircraft Comanches, P A24-250 , (2) I-twin engine turboprop Piper Cheyenne II All cloud base planes were equipped with Carley-type liquid fuel generators, one mounted to each wing tip. Each generator holds 6 gallons of a liquid seeding solution and bums AgI at two grams per minute of operation (two gallons ofliquid solution is burned per hour). Each full generator carries a total of 360 grams silver iodide and can bum continuously for 3 hours. In 1999 cloud base planes were stationed at Lakin, Johnson, Syracuse, Leoti and Scott City. Two planes were based at Colby and one in Goodland. The cloud top plane was based in Dodge City. All aircraft are equipped with Global Positioning System (GPS) units which allow pilots and meteorologists to precisely reference distance and direction from each radar site. A second GPS unit was placed on each aircraft in 1998 to record seeding events, flight track information and provide backup for the primary GPS. Also iIJcorporated into our operational radar systems are aircraft interrogator/transponder (IFF) flight tracking systems. From our radar base in Lakin, simultaneously we can track six discrete tran'sponder codes, whereas, in Colby just three codes can be tracked, The cloud base aircraft can use any of 8 codes assigned to us by the Federal Aviation Administration in a 1997 agreement with them. Cloud-top flights, which operate under Instrument Flight Rules (IFR) and are given a different code with each flight, can be tracked with the system as well. All eight cloud base planes were equipped with stainless steel wing racks and mounted to the trailing edges of the wings. Each rack has positions for 12 pyrotechnic devices (called flares), which hold them in place while they bum to a stub. The flares used in hail suppression this year were the same 120-gram units we used in 1997 and 1998 and are manufactured by the Weather Modification Group near Calgary. Hail suppression flares make possible the addition of significant quantities of ice nuclei to a cloud when they are needed such as when extremely vigorous cloud updrafts are encountered which would otherwise be beyond our capability to seed properly using only wing generators. Our reason for wanting to use flares has been to add greater capacity to combat severe storms in the early part of the season leading up through wheat harvest. That time period generally coincides with the greatest period of crop exposure to hail damage. By the conclusion of wheat harvest in early-to- mid-July, the next primary crops of concern are com and milo, both of which are generally a little more resilient to small hail damage by July. Although wheat and com are the two main crops grown in the region, milo, soybeans and sunflowers round out the main row crops in the region. 19