On December 31, 1972, a DC-7 cargo aircraft crashed in Carolina, Puerto Rico, killing all five people on board, including baseball legend Roberto Clemente. As a result of inadequate maintenance, the aircraft's No. 2 engine failed after takeoff. After initiating a turn to return to the airport, the aircraft eventually descended into, or attempted to ditch into the ocean a mile offshore. The crash site was listed on the US National Register of Historic Places in 2022.
Background Roberto Clemente was a baseball star for the Pittsburgh Pirates, with whom he had won two World Series championships. On September 30, 1972, in his final at-bat, he had become only the 11th player in Major League Baseball history to collect 3,000 hits.
In October 1972, Clemente traveled to Managua, Nicaragua to coach the Puerto Rico national baseball team at the 1972 Amateur World Series. Weeks later, on December 23, a 6.3-magnitude earthquake struck the country near Managua, devastating the city and killing approximately 5,000 people. Many countries sent aid to Nicaragua, inspiring Clemente to contribute to the relief effort with his own money and to personally supervise the delivery of goods. Clemente had also been convinced to become involved by local television show host, reporter and celebrity Luis Vigoreaux.
Clemente had previously sent three cargo planes and a ship to help the Nicaraguans, but heard reports that the military had seized the goods intended for the earthquake victims. Suspecting profiteering by the military, he chartered a fourth plane so that he could visit Nicaragua and directly confront the military leader, believing that as a celebrity he could not be harmed.Rob Ruck "Sandlot Seasons: Sport in Black Pittsburgh," University of Illinois Press, 1987
Aircraft The accident aircraft was a Douglas DC-7CF, a freighter conversion of the DC-7 (cn/msn 45130/823), registered in the United States as N500AE. The aircraft first flew in 1957.
Accident
+ VictimsNameAgeRoleNotes38Passenger47PilotOnly body recoveredUnknownPassengerAssociate of ClementeSat in engineer's seat27Co-pilotAlso owner of the airline The accident caused the deaths of all five people on board, including Clemente. The airplane crashed immediately after takeoff from Isla Verde International Airport, flying into the ocean at the adjacent area known as Piñones.
Cargo carrier Clemente and a relief committee had leased the aircraft for $4,000 from a local airline, American Air Express Leasing Company,NTSB Report: F.A.A. accident report dated February 22, 1973, Factual Report of Investigation NYC-73-A-N094 and Briefs of Accidents File 3-3757 which was owned by a 27-year-old Puerto Rican named Arthur S. Rivera.
Unknown to Clemente or to the pilot, the four-engine Douglas DC-7 had suffered a non-fatal taxiway accident just 29 days before the fateful flight took place. This accident damaged the No. 2 and No. 3 propeller blades and the No. 3 engine cooler scoop. Advised to replace one of the engines, Rivera pressed his mechanics to do what they could to inspect the engine and keep it in service, but after inspecting the engines, the mechanics could not find a reason to justify replacing one. The standard procedure after the sudden stop of a piston engine is to disassemble the engine to magnaflux its parts for cracks, but this was not done. An FAA maintenance inspector inspected the propeller shaft limits after the sudden stoppage repairs and found them within tolerances, though a later report said that he merely witnessed the inspection.
The post-war era in which cargo carriers operated surplus piston-driven prop planes was at its end, as high maintenance costs restricted the ability to keep up with newer aircraft technology. Rivera had just regained his FAA clearance to operate a cargo plane, claiming that it was his only livelihood. Struggling to keep American Air Express Leasing afloat against a tide of change in the airline industry, he began to cut corners.
Crew After volunteers spent most of the afternoon loading the aircraft, pilot Jerry Hill boarded the plane as the sole member of the flight crew. Owner Rivera sat in the co-pilot's seat, though he was only certified to fly the twin-engine Douglas DC-3, which had Pratt & Whitney Twin Wasp engines. Rivera may not have understood the added complexity of the DC-7's Wright R-3350 Duplex-Cyclone engine, which was nearly twice the size and power. Francisco Matias, a fill-in mechanic employed by another airline who was moonlighting with several other mechanics for cargo carriers at the same airport, sat in the flight engineer's seat because Rivera and Hill had made several unsuccessful attempts to secure a flight engineer.
Hill, a well-qualified, seasoned pilot, was in command. He had been found by chance several days earlier while watching the plane being loaded. After another pilot had failed to show from a waitlist of itinerant pilots, Hill flew back from Miami on short notice. He sat in the plane for the first time the previous morning of the flight, and slept all day in a crew bunk to rest for the flight.
This was the aircraft's first flight since Rivera had purchased it several months earlier, and it was the first time that the pilot had flown with either Rivera or Matias. Clemente boarded with associate Angel Lozano around the same time as the aircraft's crew.
Loaded aircraft weight National Transportation Safety Board (NTSB) investigators later estimated that the aircraft's gross weight at takeoff was , based on a fuel receipt and customs declaration. The plane had been loaded by a ground crew led by a qualified loadmaster. The calculation was based on the following estimates and measurements:
Plane: Fuel: (round-trip) Cargo: (from flight plan) Crew: Five members, ( per person) Fuel reserve (one hour):
At its takeoff weight, the aircraft was three percent () over the maximum takeoff weight for a DC-7C. The crew submitted a flight plan with a cargo weight of (including crew and reserve fuel); without fuel, that resulted in a takeoff weight of , which was under the 144,750-pound limit. At a minimum, the one-way flight would need of fuel, which would mean a takeoff weight of , again under the limit. With a one-way fuel load, the pilot would have to divert to somewhere such as San José, Costa Rica or Panama City to refuel for the return leg. It is possible that the flight's fuel was donated, and there would be a challenge finding fuel in the devastated city of Managua. This left the investigators to guess how much fuel was actually on board, stating that "The actual weight and balance computation made by the crew was not found." Secondary documents indicated that enough fuel for a round trip was purchased and presumably loaded onto the plane.
Weight calculations
The commercial airline industry of the 1970s used general factors in calculating takeoff weight and maximum weight limits. However, applying more current scientific knowledge may lead to a more accurate estimate of the aircraft's takeoff weight.
The aircraft's fuel weight was a focus of conjecture. The investigation found evidence that the aircraft was fueled for a round trip. The investigators calculated the weight of that fuel and pushed the aircraft weight to . The distance to Nicaragua was less than half the range of a fully loaded DC-7C,Greg Goebel "The Douglas DC-4, DC-6, & DC-7." Airvectors, June 01, 2018. Accessed 1/4/2019. https://www.airvectors.net/avdc4.html which holds of fuel."Douglas DC-7C Technical Specifications." www.prop-liners.com. Accessed 1/2/2019. http://www.prop-liners.com/dc7ctech.htm At takeoff, the plane was filled to 60% of fuel capacity. However, the 1972 investigation was limited, because at the time, the effect of temperature on fuel density and weight was not well understood by the airline industry."Fuel Density Flight Engineering." Accessed 1/2/2019. http://code7700.com/fuel_density.htm Depending on temperature, gasoline ranges from under at . The fuel needed for the four-hour flight to Nicaragua and four-hour return to Puerto Rico was somewhere between , a difference. Puerto Rico has a hot climate, with the December temperature usually above , so the fuel would have actually weighed on the low side. The estimated by which the flight was overweight is equivalent to of fuel, 9% of a DC-7's fuel capacity, sufficient for an hour of flight.
Another concept introduced after the 1970s is zero-fuel weight, the total weight of the airplane and all its contents minus the total weight of the usable fuel on board. The weight of fuel in the wings has less of a structural effect than that of the fuselage—modern planes have a zero-fuel weight that allows for increasing the maximum takeoff weight when that weight is in fuel.
Air density affects the maximum takeoff weight. Colder air provides more buoyancy, more engine performance and a wider safe engine operating band. The later takeoff time meant the air temperature was , 10 °F (6 °C) cooler than daytime evening air. The cooler, denser air provided both better buoyancy and increased engine performance, which at sea level provides a considerable increase to the aircraft's weight capacity (a DC-7C could see a change with a 10° drop in air temperature)."Does temperature affect takeoff performance?" Accessed 1/3/2019. https://aviation.stackexchange.com/questions/1531/does-temperature-affect-takeoff-performance"Given aircraft and runway characteristics, how do you compute the maximum temperature for take-off?" Accessed 1/3/2019. https://aviation.stackexchange.com/questions/45488/given-aircraft-and-runway-characteristics-how-do-you-compute-the-maximum-temper
The flight might not have been overloaded after all. Regardless, Hill would not have known the concepts of fuel density, zero-fuel weight or air buoyancy adjustment, though by experience he should have become familiar with the engine performance change. The NTSB investigators found that while weight was a factor in the accident, it was not the cause.
A more interesting calculation is that the plane could not have landed with both a full cargo load and enough fuel for a return trip; if at takeoff the aircraft was , then in Nicaragua it would have landed after burning of fuel and would weigh , which is over the landing-weight limit. To land at a specified weight and have return fuel would limit the cargo to .
The takeoff and landing limits are commercial peacetime limits, but war emergency load limits may be up to 20% higher. The war emergency takeoff limit would be and the landing limit would be ; the DC-7C was within those limits, which are set for new military aircraft receiving military maintenance. Hill would have been aware of these emergency cargo limits from his time as a U.S. Air Force major flying the Douglas C-124 Globemaster II on a transpacific route (possibly the Douglas C-74 Globemaster). Whether the Nicaraguan earthquake relief was an event allowing for emergency cargo limits is an open question.
Clemente's wife said she was concerned that the plane seemed old and overloaded.
Safety oversight As air traffic control is merely responsible for directing traffic and cannot be expected to determine if a flight should take off, a lawsuit was brought charging that the FAA should have prohibited the takeoff. The FAA argued that the aircraft was overloaded rather than mechanically unsound. The court ruled that because the FAA had not inspected planes at that airport previously, it was not liable, despite its knowledge of the aircraft's condition and its failure to act. The court stated that the takeoff decision is ultimately the pilot's responsibility, though it did not find Hill at fault.William B. Cassel "Federal Tort Claims Act: FAA Warnings to Private Aircraft Passengers: Clemente v. United States, 567 F.2d 1140 (1st Cir. 1977), cert. denied, 435 U.S. 1006 (1978)." Nebraska Law Review Volume 58 | Issue 1 Article 10. Accessed 1/2/2019.