1. Initial Concept: Project Hailswath - Rapid City, 1966 - NSF sponsored - Paul MacCready (MRI) participation Impetus:Hail suppression activities in USSR Cloud seeding activities in Dakotas, elsewhere

3. Implementation Hailstorm Models Project 1967 NSF grant to SD School of Mines PIs – Schleusener and Dennis Subaward to MRI - Work assigned to Robin Williamson

4. Challenges Armoring for hail protection Tested for 3-inch hail at 100 m/s - “Hail cannon”: wing section, windscreen Wings 0.090 inch; cowling 0.125 inch - Heat treated aluminum - Approx. 700 lb. Canopy: cage (lightning), 0.75 inch stressed acrylic Icing Deicing – except prop – not practical One-inch accumulation tolerable in summer

5. Configurations Initial (1969):Two-seater 1200 HP engine NARF modifications(1970):Wing spar (1971):General airframe 1425 HP engine Propeller

7. T-28 Operations First deployment:1972, NHRE Last deployment:2003, Oklahoma and Colorado Science:Storm structure - Microphysics - Updrafts - Transport (via tracers) Precipitation evolution – esp. hail Storm electrification Lightning chemistry Evaluation of remote sensing inferences

8. T-28 Operations (cont.) Project Locations: West:Dakotas, Montana, Colorado, Kansas, Oklahoma, New Mexico, Texas East:Illinois, Alabama, Florida International:Alberta, Switzerland

9. Lessons Learned Safe penetration of hailstorms possible – but avoid highest reflectivities Aircraft can carry ice load in summer work Positioning with respect to storm essential –Radar, GPS, telemetry –Safety, data interpretation Stairstep flight profiles confuse space and time variations Audio, video valuable adjuncts to quantitative measurements

10. T-28 Limitations Altitude:About 7 km (23,000 ft.) Endurance:1.5 hours on station Payload:500 lb. Ferry Range:500 mi. Over-water Capability:Restricted

11. ©Warner Images

12. Idea goes back to 1985 (and 1987 and 1992) workshops concerning aircraft needs “…more capable storm penetrating aircraft for replacement of the T-28 within five years.”

13. A Next-Generation SPA? (2) Revisited in 1999 SPA Workshop Possibilities examined in 2002 FTA engineering study What’s needed? Ability to get there faster, reach higher altitudes, stay longer, carry more stuff Global reach desirable

14. Desired SPA Performance Capabilities (ca. 1999) Table 3: Desired SPA Performance Capabilities Altitude: To reach at least –40  C, with useful rate of climb through at least 30,000 ft (9.1 km) Crew:Observer desirable; Pilot only preferred, for safety and instrument payload considerations Deicing / Anti-icingSustained flight in known icing conditions Electrical "hardening":Isolation of fuel cells causing buildup of static charge Endurance:3-5 hours on station Hail resistance:Withstand 3 in (7.6 cm) hailstones in flight Lightning resistance Payload:200 kg or more for instrumentation Power:2 kW or more for instrumentation Space:For instrumentation, data systems, and possibly observers

15. A Next-Generation SPA? (3) Requires a jet aircraft – probably military, to withstand storm environments Best candidate: The A-10

19. A Next-Generation SPA? (4) Improvements with the A-10: A-10T-28 Altitude38,000 ft 23,000 ft On-station time3 hours+ 1.5 hours Payload5,000 lb internal 500 lb 15,000 lb external Ferry range (one way)2,500 mi 500 mi Potential new capabilities: A-10 designed for low and slow flight Gun bay has room for downward-looking sensors Dropsondes or towed devices

20. Limitation Pilot only!  Instruments must operate autonomously, or with only remote input

21. A-10 Challenges Assessment of science potential How to get access to one? Technical:Armoring Protection of engines Ballast Icing

22. Inertial Separator