Thursday, 22 June

T-28 Flight 757

Project Flight 12

Take Off ~ 23:25 GMT

Return to Base: 01:10 GMT

Pilot: Charles Summers

At the time of launch there was a storm northwest of CHILL producing mostly positive CGs and another to the southwest producing mostly negative CGs. The initial target was the storm to the northwest about 41 nmi, producing mostly positive CGs and 1 inch hail. The T-28 made several passes north-south through this storm at 18000 ft MSL (6 km), encountering severe turbulence, icing, hard hail up to one inch and frequent lightning (as frequently as one every 3 to 5 sec). A weak funnel was observed under this storm for a few moments around 00:03. The storm was producing hail as it went over Spol, causing the Spol operators to stow the antenna for the duration of the hailfall at the site.

The aircraft encountered high concentrations of small hail. (The hail on the ground was reported to be about the nickel size.) Two electric field sounding balloons were launched into the storm. The storm penetrations were at ~6km altitude. The Ez component polarity frequently switched sign due to lightning flashes, and the peak magnitude was 50 kV/m.

Out of many thousands of particles going through the HVPS instrument, 2295 particles passed the selection criteria for acceptable charge measurement with detectable charge values greater than 5 pC in magnitude. Of the 2295 particles, 1282 were positively charged having a total charge of 30 nC and 1013 particles were negatively charged having a total of -17nC. There were two regions (See charge and electric field plots, between points a and b) that showed more particles with large positive charges than particles with large negative charges. After 23:54 UTC time, the HVPS quit working, and had to be rebooted, frequently.

One interesting E-field data segment is the landing part. The Ez field component was negative below 4 km altitude and then become positive due to a lightning flash. After that it changed from positive to negative, as the aircraft descended down to 2km altitude. From this point it became positive again until the airplane reached the ground.

The aircraft instrumentation took a beating on this flight. No data were obtained from the DMT liquid water instrument. The FSSP was in good working order, but a preliminary look at the data suggests that it iced over at several points in the flight. Data were obtained from the HVPS but there were periods when, inexplicably, no images were recorded. The 2D-C data were good. There frequently were unfrozen drops in updrafts within the -5 to -9oC layer. The hail spectrometer images were often corrupted, but the one-dimensional sizing/counting functions appeared to work well. Images to 1 inch were obtained.

The aircraft itself suffered minor damage. Cooling fins on #2 cylinder were bent, one push rod seal was leaking, some oil and hydraulic fluid were pushed out of their reservoirs by strong downward accelerations, and the left wing tip and FSSP forward dome showed large distinct new dents.

There was an electrical balloon sounding into the back side of this weather complex near the end of the T-28 flight (00:38 UTC). Maximum Ez was ~80 kV m-1. There was a second launch at around 03:00 UTC into the backside of the anvil of the storm as it headed eastward from Kansas Rt. 27 at a location 15 mi north of Goodland.