Project Thunderstorm: Storm Chasing with P-61 Black Widows

P-61 crew with their hail damaged aircraft
(NOAA History)

In the immediate postwar period the Civil Aeronautics Authority (CAA, the predecessor organization in the United States to the current FAA) began to gear up several research efforts in order to establish guidelines for the regulation of the anticipated boom in civilian flying. One of the areas that the CAA placed emphasis on was understanding the dynamics of severe thunderstorms which were all too common across many of the trunk routes of the United States. In 1945, the U.S. Congress authorized $250,000 to the U.S. Weather Bureau (which would become the National Weather Service in 1970) to study severe thunderstorms with specially-instrumented Northrop P-61 Black Widow fighters. Cooperating with the U.S. Weather Bureau were a number of organizations- the U.S. Army Air Forces, the Naval Research Laboratory of the U.S. Navy, the National Advisory Committee for Aeronautics (NACA, the predecessor organization of NASA), the Meteorology Department of the University of Chicago, the Physics Department of the University of New Mexico, the Electronics Department of the Massachusetts Institute of Technology, and the Soaring Society of America. With the U.S. Weather Bureau as the coordinating agency, University of Chicago meteorologist Dr. Horace Byers was appointed director of the Project Thunderstorm. 

The P-61's SCR-720 radar
(Wikipedia)

With the Second World War having ended just weeks prior to the Dr. Byers' appointment, there was a ready surplus of aircraft, pilots, and personnel to undertake the project. In addition, the CAA anticipated a rapid increase in postwar civilian flying. A spate of weather related accidents in the summer of 1945 also provided additional impetus to the endeavor. While other aircraft would be used in the study, the main storm penetration flights would use the P-61 Black Widows that once belonged to an Alaska-based USAAF weather reconnaissance unit. The aircraft were large with good range for multiple storm penetrations and were known to be tough. Pilots and crews were all volunteer and briefed in advance of the hazardous nature of the flights. The Black Widow in addition carried an onboard radar, the SCR-720. The radar was a joint development between Bell Laboratories and MIT as an improvement over previous airborne intercept radars which had a limited range of only five miles. Compared to previous AI units, the SCR-720 had a longer range (twenty miles in good conditions) and would be the primary AI night fighter radar of the Allies during the Second World War. One of the early problems of AI units in those days was attenuation and blocking of the radar beams by heavy precipitation- for Project Thunderstorm, though, this limitation was useful as it allowed the P-61's radar operator to get radar images of the thunderstorms at multiple levels. 

The pilots were selected from the Air Materiel Command's All-Weather Flying Division and were scrutinized closely for their skills and aptitude for the missions. The radar operators were all highly-trained and experienced individuals from the Navy and USAAF and the third member of the P-61 crew was a weather observer would would be responsible for collecting a variety of measurements during the storm penetration flights. 

The Soaring Society of America provided three Pratt-Read TG-32 two-seat gliders and pilots. The gliders were used to gather data on cumulus clouds before they had developed into thunderstorms as well as to make study flights on the storm periphery. Approximately 141 glider flights were made for the US Weather Bureau- one pilot, Paul Tuntland, got caught inside a thunderstorm updraft and was carried from 4,000 feet to 22,000 feet, setting a new national altitude record for gliders!

P-61s and a single F-15 Reporter getting ready to sortie
(NOAA History)

The first phase of Operation Thunderstorm took place over a sixty-square mile instrumented range near Orlando, Florida. Aircraft were based at Pinecastle Army Air Field, Florida (today's Orlando International Airport) using Black Widows fitted out with data recorders and weather instruments. Two seat glider aircraft were also used to gather data on the periphery of the storms as they entered the test range area. Microwave radar stations were set up around the Orlando area for early warning- as a storm was detected, the P-61s sortied and would penetrate the storm cell five aircraft at a time at 5,000-foot intervals from 5,000 feet to 25,000 feet. The same radar stations would also vector the P-61s into and around the the storms on their missions. Fifty ground based stations also were used to collect atmospheric data at ground level. Three radiosonde stations were also used to release multiple weather balloons into the storms in the test range. The test flights took place between 29 June and 18 September of 1946. The second phase took place at Clinton Army Air Field near Wilmington, Ohio (today's DHL Airborne Airpark), only this time there were 13 of the specially-instrumented Black Widows used plus four Northrop F-15s (the reconnaissance version of the Black Widow) owned by Northrop and single P-61 that was being used by Trans World Airlines for its own weather research. Starting on 1 May 1947, the aircraft would make storm cell penetrations every time a severe weather front passed through the area. 

SCR-720 radar image of a thunderstorm
(YouTube)

Pilots made their penetration flights with the trim set for straight and level flight. Once in the storm, they were to do their best to minimize control inputs as sensors would record not just the pilot's instrument panel, but also the power settings, control surface movements as well as the aircraft's motion as it was buffeted by the storm. Aircraft routinely landed after their missions with damage from hail and lightning strikes. Despite the punishment of the storms and the hazardous nature of the penetration flights, over the course of 1,362 missions, not a single aircraft or crew member was lost. In recognition of their skill and bravery, all the crews were awarded the Distinguished Flying Cross. 

By 1949, the study ended and the meteorology department of the University of Chicago was given responsibility for analyzing the data from both phases. One of the most prominent severe weather researchers came from the University of Chicago's department having had his start with the Operation Thunderstorm data- Theodore Fujita, who would later become one of the world's foremost experts on mesoscale systems and tornadoes- and who developed the Fujita Scale for tornadoes used today as the Enhanced Fujita (EF) Scale. 

Operation Thunderstorm contributed a large body of data that not only increased the safety of civil aviation, but also set the stage for improvements in severe weather forecasting. The use of the Black Widow's SCR-720 radar also led to the development of airborne weather avoidance radar by commercial aircraft. 

Further reading: 

Irving Langmuir and Project Cirrus

Project Stormfury 1962-1983

Weather Reconnaissance Squadron FOUR (VW-4): The Navy Atlantic Hurricane Hunters

The 1952 Carswell AFB Tornado

Sources: Wings of Fame, Volume 15. AIRtime Publishing, 1999, "Northrop P-16 Black Widow" by Warren E. Thompson, p91. "Thunderstorm Research Project" from In the Breeze Vol. 2, No. 12, January 10, 1946, pp1-2, accessed via NOAA History. "Project Thunderstorm" by Steve Zuger, Aviation History, July 2015, pp30-33.

27 Years Before the Eagle Was the First F-15

The Northrop P-61 Black Widow, despite having a wingspan of 66 feet and being the size of most medium bombers, possessed a high speed and maneuverability that made it a candidate for further development into a very-long range day fighter. With the war in the Pacific now on the front door step of the Home Islands, there arose a need for a fighter with a very long range to escort the Boeing B-29 Superfortress bombers from their bases in the Marianas and China to Japan and back. The development of the Lockheed XP-58 Chain Lightning was hobbled by troublesome powerplant issues and innumerable deficiencies uncovered in the flight test program for the Fisher XP-75 Eagle meant that the USAAF had to fall back on a long range version of the Thunderbolt, the Repubic P-47N. Not feeling that this was the optimum solution, the USAAF authorized development of twin-seat, twin-engine escort fighter designs to meet the need for a long-range B-29 escort. North American was issued a contract to develop the P-51 Mustang into the P-82 Twin Mustang while Northrop was given a contract to develop a day fighter version of the P-61 Black Widow. 

To save time given the pressing needs of the Pacific War, two P-16B Black Widow airframes were pulled from the production line (the aircraft were 42-39549 and 42-39557) to be modified into the XP-61E prototypes. The primary modification was the replacement of the center crew nacelle with a new nacelle that had only 50% of the cross-section of that of the Black Widow. Instead of housing three crew members, the new nacelle sat two pilots in tandem under what was a the time the world's largest single-piece bubble canopy. The air intercept radar in the nose of the Black Widow was replaced with four 50-caliber machine guns which would form the new fighter's main armament. The four 20mm cannon in the belly of the nacelle were retained on the XP-61E. Extra fuel tanks in the new crew nacelle aft of the cockpit gave the aircraft a 1,158-gallon fuel load, nearly double the 640-gallon capacity of the Black Widow. In addition, the XP-61E could carry four 310-gallon external fuel tanks as opposed to the just two external tanks of the Black Widow. 

By the time of the XP-61E's first flight on 20 November 1944 from Northrop's facility in Hawthorne, California, the war in the Pacific had progressed rapidly and the landings on Iwo Jima in February 1945 gave the USAAF an airfield that was halfway between its main B-29 bases in the Marianas and Japan. Basing of P-51 Mustangs on Iwo Jima now made the need for an escort fighter with the same range as the B-29 superfluous. However, with the planning underway for the Allied landings on the home island of Kyushu on October 1945 (Operation Olympic) and the landings on the main island of Honshu (Operation Coronet) set for the spring of 1946, a need arose for fast, agile reconnaissance aircraft to map the planned invasion zones and associated targets. While realizing that the reconnaissance need would ultimately be met by the Hughes XF-11 and the Republic XF-12 then under development, the USAAF wanted an interim design based on the XP-61E designated the F-15A Reporter. With an estimated eventual need for 320 F-15As, the USAAF ordered the first batch of 175 Reporters in June 1945 as Northrop's design would be ready much sooner than either Hughes or Republic's custom-tailored versions. 

Given that all that was needed was removal of the four 20mm cannon in the belly of the central crew nacelle and replacement of the 50-caliber machine guns in the nose with camera equipment, Northrop had the first XF-15 Reporter ready in only five weeks. The six camera stations in the nose could accommodate 17 different types of cameras in 24 combinations. With the armament removed, the F-15A would have a range of over 4,000 miles with 1,330 gallons (increased over that of the XP-61E thanks to the removal of the underbelly cannons) internally and another 1,240 gallons in the four external tanks. Despite such promising performance, the second XF-15A prototype was not completed until 10 August 1945 due to the need to fit turbosuperchargers to the Pratt & Whitney R-2800 radial engines, the day after the second atomic bomb was dropped on Nagasaki. 

With the Japanese unconditional surrender on 15 August 1945, the need for reconnaissance coverage for the invasion of Japan evaporated, but the USAAF recognized the need for detailed mapping of Japan and its occupied territories to support the postwar occupation and reconstruction of the country. As a result, the original purchase contract for 175 F-15A Reporters escaped the wholesale cancellations that swept the US aircraft industry following the end of the war. However, the contract was amended from 175 examples to just 36 aircraft on 21 May 1946. The first production F-15A Reporter was delivered to the USAAF on 4 September 1946. The planned penultimate reconnaissance aircraft of the war, the Hughes XF-11 and the Republic XF-12 Rainbow, made their first flights in 1946 on 7 July and 7 February, respectively. Tail number 45-59302 was the first operational F-15A accepted into service and was named "Klondike Kodak" and photomapping operations were started in July 1946 with the 8th Photo Reconnaissance Squadron based at Johnson AB in Japan. Over the next 30 months the 8th PRS's fleet of Reporters mapped Japan, South Korea, and the Philippines. Only two aircraft were lost in those 30 months, an impressively low-loss rate given the long range nature of the photomapping missions. In addition, the 7th PRS and the 63rd PRS operated clandestine reconnaissance missions from Yokota and Johnson AB in Japan, presumably over Communist-held areas in China, Korea, and possibly over the Soviet Union. 

In June 1948, following the establishment of the US Air Force as independent branch of the military the year prior, the F-for-foto designation was changed to the R-for-reconnaissance prefix and the F-15A become the RF-61C (with F now standing for fighter). The 8th PRS, the main unit that operated the small group of Reporters, was redesignated the 8th Tactical Reconnaissance Squadron as a result of the designation change, but by this point Reporter operations were being drawn down with the first aircraft going into storage. The last RF-61C Reporter was stricken from active duty on 14 March 1950, only three months before the Korean War broke out. 

The non-operational history of the F-15A/RF-61C Reporter included the use of a single aircraft (45-59318) in Operation Thunderstorm from 1946 to 1947 along with several other P-61B Black Widows. This particular Reporter was disposed of by the USAF in November 1949. The first Reporter prototype (45-95300) was used for another 17 months by the USAF and Northrop on a variety of test programs before it was passed onto the National Advisory Committee on Aeronautics (NACA, the predecessor organization of NASA), where it was operated from Moffett Field, California between 1948 and 1950 to carry aloft various test shapes and scale flying models to be dropped from high altitudes. By 1951 when all other Reporters had been scrapped, this first Reporter went on the US civil register as N5093V and even did a short stint in Mexico as XB-FUJ, both times in an aerial spray role. In returned to the United States in the operation of the US Forestry Service as N9768Z where it was modified with a large fire retardant tank under the central crew nacelle. Operated by Aero Enterprises of Fresno, California, on behalf of the USFS, it was nicknamed the "Pregnant Widow" and was lost when it crashed near Hollister, California during a retardant drop on 6 September 1968. 

Source: Air Fan International, September 1996, Volume 1, Number 6. "Northrop Reporter- The first F-15 was no Eagle" by Alain Pelletier, p54-62.