March 17, 1960, 3:15pm - 18,000 feet over Tell City, Indiana.

Lockheed L188 Electra
Northwest Airlines Flight 710

March 17, 1960, 3:15pm, Tell City, IN

Here is a video that simulates the final moments of Northwest Airlines Flight 710, as it flew over South Indiana on March 17, 1960. It was flying at approximately 18,000 feet, at about 330kts (375 mph) on a heading of 170 degrees. Using commercial flight simulation software, configured as closely as possible to the actual aircraft, time, location and weather conditions as observed, this 90 second video details the view of the plane from various angles, and from the cockpit before the breakup. Then the view from the cockpit window is shown, during and after the breakup, with the 3.5 mile fall to the ground, shown in real time; it is not graphic in any sense, but illustrates the time it took to fall.

I have also located the official Indiana State Police film they made about this this event, "Operation DISASTER":

At the end of WWII, the airline industry was awash with pre-war planes, all piston engine, some unpressurized (they could fly no higher than 10,000 feet) and even a few biplanes. As with the automotive industry, the post-war brought fantastic improvements in the technology and engineering, as evidenced by some of those "finned wonders" of mid to late 1950's design. One remarkable development for aviation was the jet engine, jointly developed by Great Britain and Germany in 1936. However, even by 1950, they were still unable to meet the equivalent power of the best piston engines, they were both noisy and belched thick smoke and could quickly gulp jet fuel in gallons per second! Taking the best of the propeller age and the best of the jet age brought the world the turboprop engine. This was developed in Hungary at the beginning of WWII, and was perfected by the British postwar. These generally make 90% of the thrust from the propeller, with the remainder via the jet blast. Turboprops offered the economy and relative quietness of the propeller, with the power and relative reliability of the jet engine. One of these, developed by General Motors' Allison Division, introduced in August, 1954, was the 501-D13. Variants of this design are currently still in production as the T56 (by Rolls Royce), this engine offered designers of both civilian and military aircraft an unprecedented amount of power, almost 4200 hp. Four of these engines, mounted unusually on the top of the wing for ground clearance, powered the Electra.

The Lockheed Aircraft Corporation took the early lead of another first by the British, the 4 engined turboprop airliner, and amazed many with a state-of-the-art design, the L-188 Electra. This design, using a some of the engineering work from its hugely successful C-130 Hercules transport airplane (using the same engines, mounted normally) had a maximum range of about 3000 miles, a maximum altitude of almost 30,000 feet, and a maximum speed of 448 mph (389 knots),while carrying from 65 to 90 passengers. 170 Electras were built, with production ending in 1961. Additionally, over 600 P-3 Orion variants of the Electra were built for the US Navy, as a successful anti-submarine warfare patrol aircraft.

The Electra first flew inDecember, 1957, and was placed into commercial service on January 12, 1959, with Eastern Air Lines. Sadly, on February 4, 1959 (coincidentally, "The Day the Music Died"; Buddy Holly, Richie Valens and The Big Bopper were killed in a small plane crash that day), just a month after its inaugural flight, an American Airlines Electra crashed at New York City's La Guardia Airport, killing 63. The cause of the crash was pilot error; improperly set altimeters compounded by inadequate familiarity with the new aircraft. Seven months later, on September 29, 1959, a Braniff Airlines Electra mysteriously broke up in mid air over Buffalo TX. Braniff flight 542 was flying at 15,000 feet and at 320 mph, a few minutes after 11:00pm, when witnesses heard a "shrill howl" followed by a bright flash of light. Then, all around, the sound of various sized pieces of airplane, luggage and people were heard fluttering to the ground. Investigators quickly found that the entire left wing had separated from the aircraft, and that the remainder of the aircraft broke up almost immediately afterward. However, they were baffled at how a nearly new airplane, delivered only 10 days before, could have suffered such a catastrophic failure without apparent bad weather, nearby aircraft traffic or emergency communications from the cockpit. Six months after this accident, the newly formed Federal Aviation Agency (renamed the Federal Aviation Administration in 1967) could still not find a definite cause. There was evidence indicating the number 1 engine assembly and propeller had been "wobbling"; the propeller was almost 35 degrees off center before the breakup.

Then, on March 17, 1960 (St. Patrick's Day), another Electra fell fromthe skies. This was Northwest Airlines Flight 710, United States Registration #N121US. It crashed in Millstone, IN, a few miles east of Cannelton, IN, carrying 57 passengers and 6 crew members. There were no survivors.

The flight originated at Minneapolis, MN (MSP) and then headed to Chicago, IL (MDW). It departed MSP at 12:50pm, cruising at 15,000 feet and 340 knots (390 mph), and arrived at MDW at 1:55pm. After 30 minutes for refueling and passenger deplaning, it continued on to its final destination, Miami FL (MIA), departing MDW at 2:35pm. Flight time was estimated at about 3.5 hours to Miami. Indianapolis Air Traffic Control heard from the aircraft at 3:13pm as they reported passing over Scotland, IN at 18,000 feet, in preparation for the handoff to the Memphis, TN Air Traffic Control Center. This was the last transmission heard from the aircraft. A few minutes later, at about 3:15pm on the ground below, it was cold, with a few inches of snow on the ground. The weather was clear, with scattered clouds at about 4000 feet. Suddenly overhead, witnesses on the ground saw smoke puffs from the aircraft, then more steady smoke and the sound of two explosions. An engine and wing had fallen off, followed by other observable parts a few moments later. They then watched in horror as the remaining, intact fuselage, with one inboard engine still running on the stub of the left wing, arced over toward the ground. It was estimated that it was traveling nearly 600 mph upon impact.

At the main crash site, a crater about 20 feet deep and 40 feet in diameter held the crushed and compacted remains of the plane and the 33 men, 21 woman and 8 children and 1 infant. The approximate 100 foot long fuselage was reduced to a 30 foot mass at the bottom of the crater. The intact right wing was found about three miles away to the north, at German Ridge, and other parts were scattered about on the snowy ground. US Air Force pilots conducting a training mission nearby witnessed the crash. They, and other civilian aircraft in the vicinity had also recently reported some moderate to severe clear air turbulence between 15,000 to 25,000 feet. As with the previous crash in Texas, this was a nearly new airplane, with only about 1780 hours of total flight time, and only 74 flight hours had elapsed since its last major maintenance inspection. Lockheed, the FAA, and the flying public had now 3 Electra crashes in less than a year. Amazingly, a fourth happened near Boston, on October 4, 1960, but that was quickly traced to a massive flock of starlings that clogged 3 of the 4 engines on takeoff.

With the evidence from two similar crashes now in the hands of the FAA, NASA and the manufacturers of the aircraft and engines, it took only 2 months to uncover the hidden flaw that caused these crashes. After an intense evaluation of the remains, as well as a complete reevaluation of the original engineering designs, it was discovered that a few calculations of the wing structure had been slightly in error. This, along with a chance coupling of structural resonance and a phenomenon called "whirl mode", directly caused the failure of the outboard engine mounts, then the related wing structures, and eventually, the entire aircraft. Whirl mode can be demonstrated by using a spinning top that is suddenly hit. The gyroscopic forces that keep the top horizontal while spinning are now forced out of plane, while the laws of motion require that "For every action there is an equal and opposite reaction"; the top now wobbles on its axis. An airplane propeller will react in the same manner. Additionally, another factor was involved, resonance. Just as a rubber band will "twang" when stretched and plucked, offering a specific and exact resonant frequency as related to the tension, a mechanical structure can have a frequency of resonance, too. Normally, propeller deflections are dampened out by the structure of the engine mounts and wing, and any "twanging" is designed to be at a different resonance than that of the surrounding structure; any unwanted motion being quickly eliminated. But if some outside force such as turbulence, propeller component failures, improper maintenance, a hard landing, corrosion or other unplanned event deflect an outboard propeller with enough force to cause the engine to move forcefully against its mounts, it could begin to "whirl". Without any damping, the wobble continues, and the entire structure begins to fatigue. This could change the tension of these structures, thereby changing their resonant frequency. Given another deflection event, with this modified resonance, now quite possibly that of surrounding structures, (accessory brackets, cowlings, bulkheads, etc.) any oscillation will now be amplified. As with sound, or any other cyclic phenomena, this "harmonic resonance" (as a pipe from a pipe organ illustrates) continues "in harmony", weakening the structure further. If another event, or even just the relative wind of the moving aircraft is added to these now displaced, weakened and wobbling assemblies, there will quickly be an oscillation that exceeds any margins of design; the entire structure will fail. This is what destroyed the 2 Electras and killed almost one hundred innocent people.

Back at the crash site, on the farm of George Wagner, the smoke and snow mingled with clay, grass and aluminum. The Indiana State Police had mobilized almost immediately, and as the first mobile units arrived at the scene, I.S.P. aerial units pinpointed the location of other debris. The location in Millstone, IN was remote, and there was not even a paved road to the site. Units of the Indiana National Guard quickly arrived, and then, U.S. Army units from Fort Knox, KY. They conducted a comprehensive search for additional remains of both plane and passenger, but found only twisted metal fragments. Soon, agents from the FBI arrived, in the event that this was a crime scene, and for the time, it was presumed as such. As details emerged, that in the bottom of the crater there were the compacted remains of over 60 people; 6 thousand pounds of flesh and bone, it was recommended that the crater be bulldozed over; to entomb the victims in place forever. However, political, financial, legal and the other needs of our modern society demanded both an investigation and closure. Thus, a week after the crash, a 30 man contingent from the U.S. Army Graves Registration Department arrived and began the methodical and sometimes gruesome task of sorting, identifying and processing the human artifacts that were recovered in the excavation. By Wednesday, April 2, the bottom had been reached. The human remains were placed in caskets, while any excavated aircraft remains were sent off in sealed containers for technical examination. Seven of the identified victims were buried elsewhere, but ten identified victims, the 17 caskets of unidentified remains, and the four symbolic sealed brass coffins (symbolizing the religious faiths of the victims; Catholic, Protestant, Jewish and Buddhist) were buried in Greenwood Cemetery, in Tell City, Indiana, under a monument placed there by Northwest Airlines.

As the findings were being made, Lockheed began formulating the LEAP program; the Lockheed Electra Achievement Program. Immediately, all Electras were ordered to greatly limit their operating speed, and mandatory internal structural inspections were ordered by the FAA, effectively grounding the fleet. All existing Electras were carefully ferried to the main Lockheed plant in Burbank, CA and production of new aircraft was halted. Over 1300 pounds of reinforcements were added to the wings and engine mounts, the engine cowlings were redesigned, and new thicker aluminum "skin" was added to the upper and lower wings. This not only tremendously strengthened the structure, but changed its resonant frequency to one far away of anything possible from the engine assemblies. Lockheed employed many test pilots to take the first modified Electras out on extreme flights, diving them to excessive speeds, causing buffeting vibrations with plates temporarily attached to structures, and other dangerous tests to satisfy both the FAA and their own customers that these modified Electras were safe. Lockheed absorbed the entire cost of this program, approximately $25,000,000. By February 1961, all restrictions and warnings were lifted from the Electra; they were now safe to fly. But their time was over. The reputation of the Electra was permanently tarnished, and by this time the jet-age had truly arrived. More practical and efficient jets were now available, such as the Boeing 707 and the Douglas DC-8. The Electras were were retired to smaller airlines and then, to the scrapyards, while a few were converted to freighters or water tankers for wildfire fighting. A small few of these still fly today.

My personal interest in this event:
When I was young, my Dad told me about his interest in aviation, and to a typical kid, about some "crashes", too. One of those was about the Electra. He flew them constantly as a passenger between Philadelphia and Washington D.C. I also lived near Willow Grove NAS (Willow Grove, PA) and they flew P-3 Orions constantly then to monitor the Atlantic for Soviet threats. During those years, many Electras were still in commercial use, so I became very familiar with them and their unique, almost sullen, sound. One crash in particular he mentioned, was one in "South Indiana", an Electra that he was "sure he was on a few days before" because he remembered a hard landing. It was on Northwest Orient, he recalls. I can not verify that was the same plane (or even if NWO flew out of PHL then) but because of that, I kept this incident in my memory. Strangely (and unrelated to the incident), in 1995 I moved to Tell City. Having been an aviation enthusiast as well as a 1950's fan, and an avid reader, I was on the lookout for items related to that crash. A few years later, the then upcoming 50th Anniversary provided me with the incentive to research and to offer this story. While this was a sad event, I feel that keeping the information documented may assist in preventing further incidents like this, as well as to honor the engineers, craftsmen and crew that made and flew these aircraft, and most importantly, to memorialize the victims and their families.

Michael Kowalchuk, March 6, 2010

As a postscript, I have an interesting note about passenger Chiyoki Ikeda, from a book I bought for my Dad a few years ago, "The Book of Honor, Covert Lives and Classified Deaths at the CIA", by Ted Gup. Mr. Ikeda, a CIA Agent,was escorting Masami Nakamura, the Chief of Security of Japan's National Police. His cover story for this trip was that he was with the US Army. Due to worries about Communist activities in Japan in the Spring of 1960, Nakamura was in the USA researching intelligence techniques to assist in suppressing any demonstrations or other unwarranted activities.  Eventually, due to these fears, President Eisenhower was advised to cancel a trip to Tokyo, which was scheduled for June, 1960.

For the record, my Dad was one who helped win the Cold War.
He worked for over 35 years as an employee of a company providing
pioneering digital and analog communication systems for the US Military and Government.

Thanks, Dad.

Photographs of the actual aircraft, before the crash:

For a list of the individuals who lost their lives on this flight, click here.

For a few images from the 50th anniversary memorial, click here .

Finally, click here for the original references used for this project.

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Revised on January 17, 2021