Mission Summary
20030819I Aircraft 43RF
inter-comparison and calibration flight
between NOAA43/NOAA 42

Scientific Crew (43RF)

Lead Project Scientist

Michael Black
Radar/Doppler Scientist Rob Rogers
Dropsonde Scientist Eric Uhlhorn
AXBT Scientist Eric Uhlhorn
SRA Scientist Ed Walsh
BAT Probe Jeff French
Aircraft Crew
PilotsCAPT Dave Tenneson
LCDR Randall TeBeest
LCDR Tom Strong
Flight Engineer Dewie Floyd
NavigatorLCDR John Adler
Flight DirectorA. Barry Damiano
Engineers Terry Lynch
Jeff Smith

Mission Briefing:

NOAA43 planned to perform a coordinated CBLAST test flight with NOAA42 with a proposed takeoff time of 1500 UTC and a duration of about 5.5 hours. The main objectives of the flight were to execute a simulated series of eyewall dropsonde and AXBT drops, perform two stepped descents from 2500 to 200 feet AGL, evaluate the coordination between P3 aircraft, and perform a series of pitch, yaw, and speed maneuvers for Bat probe calibrations. Buoy 42003, in the east-central Gulf of Mexico, was chosen to be the location of a simulated hurricane eye. NOAA43 would chose an IP 50 nmi north of the buoy at 5,000 ft to begin a north to south run over the buoy ending up 50 miles south of 42003. Starting at 30 miles out, 43 would simulate the deployment of 4 dropsondes (the last of which would be an actual drop) and deploy 2 AXBTS at the endpoints of the sonde drop locations. The aircraft would perform an octagonal pattern for about 10 minutes and within 10 miles of the buoy to simulate circling in the eye while a new series of sondes were initialized by the AOC crew. The series of 4 sondes and 2 AXBTS would be repeated on the outbound (south of 42003) leg, right after 42 released the last of their 8 (7 simulated and one real) dropsondes. After completing the buoy run, NOAA43 would link up with 42 at a position determined in flight to perform the first of 2 step descents beginning at 2500 ft, flying upwind and downwind for 20 nmi per leg at 2500, 1200, 900, 600, 400, and 200 ft AGL. NOAA42 would be flying at 8,000 ft in a trailing pattern during 43’s 2500 ft run. The stepped descent would then be repeated except the legs would be oriented crosswind in both directions.

Mission Synopsis:

Takeoff from MacDill was at 1509 UTC, only a few minutes past the scheduled time. After coordinating with 42, we reached the IP, 50 nmi north of Buoy 42003, at 1605 UTC, where we were at our planned altitude of 5,000 ft. After dropping 2 AXBTs and 1 dropsonde (plus 3 simulated drops), NOAA43 reached the buoy at 1618 UTC and began the octagonal, circling pattern. At 1633, the aircraft tracked southbound away from the buoy and awaited word from 42 that they had dropped their last sonde before releasing an AXBT and dropsonde, simulating 3 other dropsonde releases, followed by another AXBT. The southbound leg ended at 1639 UTC. A small convective line, SE of the Buoy, was chosen by the scientific crew of 43 during the pass by 42003 as an area to perform the step descents. We coordinated with NOAA42 and reached the beginning of the (simulated) downwind leg at an altitude of 2500 ft at 1701 UTC. The aircraft ascended to 2500 ft at 1744 UTC after completing the planned series of altitudes and headings upwind and downwind (along the convective line). The second series of step descents, flying perpendicular to the cloud line (simulated crosswind), began at 1745 UTC in the same area as the first one. We finished this pattern at 1838 UTC before climbing to 3000 ft and searching for clear air on the way back to Tampa to conduct the BAT probe maneuvers. Despite an abundance of convection that was widespread, we found an area of relatively undisturbed air to try the speed, pitch, and yaw maneuvers. The first of these (yaw) started at 1923 UTC and we ended at 2008 UTC, before finishing the second set of planned pitch maneuvers. We encountered an outflow boundary from a nearby thunderstorm on the approach to MacDill, diverted around it, and landed about 2020 UTC.


Overall, the test mission was a success: the coordination between aircraft was very good, the timing of the simulated drops apparently only had some minor glitches, and the step descents were performed by the AOC crew nearly flawlessly. Almost all of the BAT probe maneuvers were conducted despite finding only a limited area of clear air on the ferry back. The direction of the up, down, and crosswind legs in the step descents were chosen to be performed relative to the orientation of the convective line rather than according to the wind direction since the winds were light and variable and the vertical shear was much different than what would be expected in a tropical cyclone. This worked well, and we only had to adjust one of out 20 mi legs to avoid weather. We also decided to try a series of left hand turns at the end of each leg in future flights to avoid drifting toward the convection and to align better with the wind (or cloud line). The exact placement of the sequence of 12 simulated and real drops (8 from 43, 4 from 43) will not be known until the flight-level position data is evaluated and dropsonde locations plotted. Based on the log sheets, though, the timing was very good, and a new strategy for the subsequent test flight was planned to make the timing even better. The communication between the scientific crew and AOC flight personnel was excellent both within the plane and between aircraft. The remaining series of pitch maneuvers that were not completed on this flight were planned to be done on the next flight. The mission met the objectives in the planning and briefings and moved AOC, HRD, and CBLAST scientists a step closer to performing CBLAST flights into hurricanes.


The SRA did not function on the flight despite efforts from Ed Walsh to revive the instrument. The radar systems worked well except for an apparent low bias of about 15 dBZ on both the LF and tail radar systems . The radar tape was also defective as determined by AOC staff after the flight. The HRD workstation was installed but not yet operational. Minor timing and coordination issues needed (and were) to be worked out after the flight. Despite concerns about the data system’s reliability, it operated continuously. None of the problems encountered were enough to warrant a delay of the second planned flight or to prevent the aircraft from completing a mission.

Michael Black

Mission photos

Flight tracks

The coordination for the 12-sonde sequence was flown as was the 6-level stepped descent boundary layer flight on 43RF, coordinated with 42RF flying overhead. The 12-sonde sequence, consisting of 4 sondes from 43RF and 8 sondes from 42RF flying in tandem. They used NDBC buoy 42003 as the simulated eye center. A simulated eyewall of 10nm radius was assumed around the buoy. The inbound drop sequence was simulated with only one sonde actually being deployed from each aircraft. Two AXBT's were deployed from 43RF and one from 42RF, plus one sonobouy from 42RF. The signals from the AXBT's were received on both aircraft while the signal from the sonobuoys was received on 43RF. The inbound leg was initiated by 4 sondes from 43RF with 42RF following with eight sondes. Sonde spacing was 2 nm or about 30 sec of flight time at penetration indicated airspeeds of 210 kt for the 4 sondes from 43 and the first 4 sondes from 42, followed by the last 4 sondes from 42 at 1 nm or 15 s spacing across and inward from the simulated maximum wind radius. 43RF lead 42RF and their flight track was displace by 2-4 nm laterally in the simulated upwind direction. Following the inbound leg, the two aircraft flew across the simulated eye and turned upwind at the far edge of the simulated eye and began a polygon pattern to fly straight level legs just inside the simulated eyewall before turning outbound after the 12 sondes this leg were prepared and all the sondes from the inbound leg had splashed. The outbound leg was the executed with the 12 simulated sondes being deployed in reverse order from the inbound leg. The 12 sonde sequence required about 45 min of flight time to execute.

Following the 12-sonde sequence, the 6 level boundary layer stair-step pattern was flown parallel to a line of convective storms to simulate a hurricane rainband. Descents on 43RF from 2,500 ft to 200 ft were flown in the simulated upwind and downwind direction, deploying simulated sondes from 42RF flying at 8,000 ft every 5 nm. With 20 nm legs, the pattern required 45 min. It was repeated in the simulated cross wind direction. Following the stair-step, which required 45 minutes for each, the BAT probe cal maneuver was executed partially before weather closed in. The remainder will be flown on Thursday.

The BAT probe was operated by Jeff French, who arrived Sunday night from Idaho Falls. It worked fine as did the IRGA for fast response humidity. The wing pylon was not installed and the CIP probe for sea spray was not operated. However, the pylon was installed August 20. Chris Fairall arrived August 19 from Boulder and successfully ground tested the CIP system August 20. It will be test flown for the first time August 21. The new AOC SFMR was again flight tested August 19. It was removed August 20 and the HRD SFMR was installed for its flight test August 21. The installed Scripps instruments operated by Jim Lasswell, who arrived on the red-eye from San Diego Monday morning, all worked well; the MASS downward camera system, the laser altimeter and the sonobuoy receiver. The downward IR camera mounts were not ready and this instrument was not flown. The SRA system operated by Ed Walsh, who flew in from Bounder on Sunday, failed its ground test on Monday and did not operate on the cal flight despite repeated efforts. Work continues on this system August 20.

The AOC data system on 43RF was repaired on Monday as was the LF and TA Doppler radars on 43RF. Both worked fine except for a calibration problem. All systems on 42RF worked fine including the radars. The UMASS IWRAP system, with only the one GVA board limiting range-gating to 30 m intervals, operated flawlessly, as did the UMASS USFMR.

Debriefing was held this morning on the flight with AOC staff and crews together with HRD and CBLAST personnel. Minor scheduling and coordination problems were ironed out. A pre-brief with AOC flight directors and navigators was held in the afternoon to plan August 21's cal flight in which the inbound and outbound 12-sonde sequence will again be practiced as well as the 3-level version of the stair-step pattern. Once again, a pre-brief will be held with the flight directors to once again go over the sequence of events for the cal flight, followed by the pilot and nav brief. Takeoff is scheduled again for 11 am.

All in all it has been an incredible effort by the engineers, crews, flight directors and entire AOC organization to prepare the aircraft with the complex array of instruments that we have asked them to install. We planned for problems with instruments and procedures, but encountered only a few minor difficulties. We appear to be headed for CBLAST program readiness by the end of the week.

Peter G. Black
HRD Field Program Director

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