Tag Archives: Boeing 747-121

27 March 1977

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A recent photograph looking west-northwest (300° Magnetic) along Runway 30 at Los Rodeos Airport (TFN), Tenerife, Canary Islands. (© Claudio)

27 March 1977: The deadliest accident in the history of aviation occurred when two Boeing 747 airliners collided on the runway on the island of Tenerife in the Canary Islands. 583 people died.

A terrorist incident at Gran Canaria International Airport (LPA) on the island of Gran Canaria resulted in the airport being closed for flight operations. This forced many trans-Atlantic airliners to divert to the smaller Los Rodeos Airport (TFN) on Tenerife. The ramp and taxiways at Los Rodeos were congested and refuelers were overwhelmed by the increased traffic, which led to many delays.

A Pan American World Airways Boeing 747-121, N750PA, similar to N736PA. (Michael Gilliand via Wikipedia)

Los Rodeos Airport has only one runway, Runway 12/30, with a parallel taxiway and four short taxiways joining the two.

Pan American World Airways’ Flight 1736, a Boeing 747-121, FAA registration number N736PA, named Clipper Victor ¹ was ready for takeoff with 380 passengers and crew, but had to “back taxi” on Runway 12 (“One-Two”) because the parallel taxiway was jammed with airplanes. The airliner proceeded east-southeast, intending to exit the runway to the parallel taxiway after passing by the congestion around the terminal.

Also on the runway was Koninklijke Luchtvaart Maatschappij (KLM) Flight 4805, a Boeing 747-206B, PH-BUF, named Rijn (“Rhine”). The KLM jumbo jet had 248 passengers and crew members on board. Flight 4805 had back-taxied for the entire length of Runway 12, then made a 180° turn to align itself with Runway 30, the “active” runway.

KLM Royal Dutch Airways’ Boeing 747-206B PH-BUF, Rijn. (clipperarctic via Wikipedia)

Weather at the time of the accident was IFR, with low clouds and fog. Visibility on the runway was restricted to about 1,000 feet (305 meters). Takeoff rules required a minimum of 2,300 feet (701 meters). What happened next was a misunderstanding between the air traffic controllers and the crew of both airliners.

The control tower instructed KLM 4805 to taxi into position on Runway 30 (“Three-Zero”) for takeoff, and to hold there for release. The Pan Am airliner was told to taxi off the runway and to report when clear. The tower controllers could not see either airliner because of the fog, and their flight crews could not see each other.

The aircraft commander of the Dutch airliner, that company’s Chief Pilot and Chief Flight Instructor, Captain Jacob Veldhuyzen Van Zanten, apparently misunderstood what was occurring and radioed to the tower that he was taking off. He then accelerated.

The crew in the Pan Am airliner heard the KLM pilot report that he was taking off, immediately turned left and ran the engines up to full throttle in order to try to get off the runway. With the KLM 747 accelerating through the fog, its flight crew belatedly realized that the other airliner was still ahead of them. Too late to stop, they applied full power and pulled the nose up trying to takeoff. The tail of their airplane actually dragged over sixty feet (18 meters) on the runway because its extreme nose up angle.

Computer-generated illustration of the moment of impact as KLM Flight 4805 hits Pan Am Flight 1736 on the runway at Tenerife. (PBS Nova)

KLM 4805 lifted off about 300 feet (91 meters) from Pan Am 1736, and because of the high angle of attack, its nose wheel actually passed over American airliner’s fuselage, but the rest of the Dutch airplane hit at 140 knots (259 kilometers per hour). Clipper Victor was ripped in half, caught fire and exploded. Rijn crashed about 250 yards (229 meters) down the runway, and it also caught fire and exploded.

All 248 people aboard the Royal Dutch Airlines airplane were killed. Miraculously, there were 61 survivors from the Pan Am Clipper, including the co-pilot, but the remaining 335 died.

Two Boeing 747 airliners collided on the runway at Tenerife, 27 March 1977. (Unattributed)

The 747-100 series was the first version of the Boeing 747 to be built. It was operated by a flight crew of three and was designed to carry 366 to 452 passengers. It is 231 feet, 10.2 inches (70.668 meters) long with a wingspan of 195 feet, 8 inches (59.639 meters) and overall height of 63 feet, 5 inches (19.329 meters). The interior cabin width is 20 feet (6.096 meters), giving it the name “wide body.” Its empty weight is 370,816 pounds (168,199 kilograms) and the Maximum Takeoff Weight (MTOW) is 735,000 pounds (333,390 kilograms).

The 747-100 is powered by four Pratt & Whitney JT9D-7A high-bypass ratio turbofan engines. The JT9D is a two-spool, axial-flow turbofan engine with a single-stage fan section, 14-stage compressor (11 high- and 3 low-pressure stages) and 6-stage turbine (2 high- and 4 low-pressure stages). The engine is rated at 46,950 pounds of thrust (208.844 kilonewtons), or 48,570 pounds (216.050 kilonewtons) with water injection (2½-minute limit). This engine has a maximum diameter of 7 feet, 11.6 inches (2.428 meters), is 12 feet, 10.2 inches (3.917 meters) long and weighs 8,850 pounds (4,014 kilograms).

The 747-100 has a cruise speed of 0.84 Mach (555 miles per hour, 893 kilometers per hour) at 35,000 feet (10,668 meters). The maximum certificated operating speed is 0.92 Mach. The airliner’s maximum range is 6,100 miles (9,817 kilometers).

The Boeing 747 has been in production for 48 years. More than 1,520 have been delivered to date. 205 of these were the 747-100 series. The U.S. Air Force has selected the Boeing 747-8 as the next presidential transport aircraft.

¹ Pan American World Airways’ Boeing 747 Clipper Victor was the very first Boeing 747 in service. It made its first commercial passenger flight, New York to London, 22 January 1970. Another airliner, Clipper Young America, was scheduled to  make that flight but suffered mechanical problems shortly before departure. Clipper Victor was substituted, but Pan Am changed the airliner’s name to Clipper Young America. On 2 August 1970, N736PA was hijacked to Cuba, and afterwards, to avoid the negative publicity, the name of the 747 was changed back to Clipper Victor.

© 2019, Bryan R. Swopes

9 February 1969

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The prototype Boeing 747, N7470, City of Everett, takes off at Paine Field, 9 February 1969. (Boeing/The Museum of Flight)
The prototype Boeing 747, RA001, City of Everett, takes off at Paine Field, 9 February 1969. (The Museum of Flight)

9 February 1969: At 11:34 a.m., Boeing Chief Test Pilot Jack Wadell, with Engineering Test Pilots Brien Singleton Wygle, co-pilot, and Jesse Arthur Wallick, flight engineer, took off from Paine Field, Everett, Washington, aboard RA001, the prototype Boeing 747-121, and made a 1 hour, 15 minute test flight. The ship was named City of Everett after the home of the factory where it was built. It was originally registered N7470.

The test pilots who flew the first Boeing 747: Brien Wygle, Jack Waddell and Jess Wallick. (Seattle Times)
The test pilots who flew the first Boeing 747:  Left to right, Brien S. Wygle, Jack Waddell and Jesse A. Wallick. (Seattle Times)

The 747 was the first “wide body” airliner and was called a “jumbo jet.” It is one of the most widely used airliners and air freighters in service world-wide. The latest version is the 747-8, the “Dash Eight.” After 53 years, production ended with a total of 1,574 747s built.

Boeing 747-121 RA001, City of Everett, 9 February 1969. A Canadair CL-13B Sabre Mk.6, N8686F, is the chase plane, flown by test pilot Paul Bennett. (Boeing)
Boeing 747-121 RA001, City of Everett, 9 February 1969. A Canadair CL-13B Sabre Mk.6, N8686F, is the chase plane, flown by test pilot Paul Bennett. (Boeing/The Seattle Times)

The Boeing 747 is a very large swept wing, four engine commercial transport. The 747-100 series was the first version to be built. It was operated by a flight crew of three—pilot, co-pilot and flight engineer—and was designed to carry 366 to 452 passengers. The airplane is 231 feet, 10.2 inches (70.668 meters) long with a wingspan of 195 feet, 8 inches (59.639 meters) and overall height of 63 feet, 5 inches (19.329 meters). The wings are swept aft to 37° and have a total area of 5,500 square feet (511 square meters). The angle of incidence is 2°, and there are 7° of dihedral.

The interior cabin width is 20 feet (6.096 meters), giving it the name “wide body.” Its empty weight is 370,816 pounds (168,199 kilograms) and the Maximum Takeoff Weight (MTOW) is 735,000 pounds (333,390 kilograms).

Boeing flight crew (Image courtesy of Neil Corbett, Test and research Pilots, Flight Test Engineers)
Boeing 747 RA001 flight crew, left to right, Jack Wadell, Brien Wygle and Jess Wallick. (Image courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

The 747-100 is powered by four Pratt & Whitney JT9D-7A high-bypass ratio turbofan engines. The JT9D is a two-spool, axial-flow turbofan engine with a single-stage fan section, 14-stage compressor (11 high- and 3 low-pressure stages) and 6-stage turbine (2 high- and 4 low-pressure stages). The engine is rated at 46,950 pounds of thrust (208.844 kilonewtons), or 48,570 pounds (216.050 kilonewtons) with water injection (2½-minute limit). This engine has a maximum diameter of 7 feet, 11.6 inches (2.428 meters), is 12 feet, 10.2 inches (3.917 meters) long and weighs 8,850 pounds (4,014 kilograms).

The 747-100 has a cruise speed of 0.84 Mach (555 miles per hour, 893 kilometers per hour) at 35,000 feet (10,668 meters). The maximum certificated operating speed is 0.92 Mach. The airliner’s maximum range is 6,100 miles (9,817 kilometers).

The prototype Boeing 747 during its first flight. (Boeing)

City of Everett last flew in 1995. It is on static display at The Museum of Flight, Boeing Field, Seattle, Washington.

Boeing 747-121, City of Everett, on take off from Boeing Field. The prototype has been re-registered N1352B. RA001 carried this registration number from July 1970 to April 1975. (The Museum of Flight)

© 2021, Bryan R. Swopes

22 January 1970

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Boeing 747-121 N736PA, Pan American Clipper Young America, watercolor by John T. McCoy. (SFO Museum)

22 January 1970: Captain Robert M. Weeks, Captain John Noland and Flight Engineer August (“Mac”) McKinney flew the Pan American World Airways Boeing 747-121, N736PA, Clipper Young America, from New York to London on a 6 hour, 14 minute inaugural passenger-carrying flight of the new wide-body jet. Aboard were a cabin crew of 17 and 332 passengers.

Crew members of the first Pan Am Boeing 747 to arrive at Heathrow. (Rolls Press/Pepperfoto/Getty Images via The Guardian)

The Associated Press reported:

The 747 Age Is Here

     LONDON (AP)—A Boeing 747 jetliner arrived in London from New York today on the maiden transatlantic commercial jumbo jet flight.

     An overheated engine grounded the original aircraft and a substitute called Young America left New York at 1:52 a.m. EST, nearly seven hours after the scheduled departure time. The jet, carrying 332 passengers and 20 crew, touched down at London’s Heathrow Airport at 8:06 a.m. EST.

     London Airport services were geared to deal as quickly as possible with the passengers and 30,000 pounds of baggage and cargo aboard the Pan American World Airways jumbo.

     SOME PASSENGERS booked on the return flight to New York switched to other aircraft because of today’s delays, but a Pan Am spokesman said most of the passengers were waiting for the Jumbo.

     The [sic] included actress Raquel Welch, who has been making a television spectacular in London.

     The Boeing took 6 hours 15 minutes on the Atlantic flight. The pilot was Capt. Robert M. Weeks, 49, a veteran of 28 years with Pan Am who has logged more than 15,000 hours on Pan Am routes.

     THE AIRCRAFT drew up at stand 1-29 on Heathrow’s Pier Five at 8:10 a.m., and passengers began disembarking four minutes later.

     One of the passengers, Mrs. Joe Tepera of Fort Worth Tex., told newsmen: “The flight was simply great. Flying in a beautiful plane like that was worth the delay.

     “All the passengers were good humored and when the plane finally took off they applauded. They did the same when it landed. I personally would not hesitate flying in a jumbo again.”

     Michael J. Flynn of Chicago said: “The delay didn’t bother me much. We were given a first class meal. It’s a good plane.”

     BUT ONE PASSENGER, who declined to be named, said he was annoyed at the service aboard the jumbo and the delay caused by switching planes in New York.

     “The plane is simply too big for anyone to be given proper service,” he said.

     Michael Brody, 21-year-old American who claims he wants to give away his multimillion-dollar fortune, was among the passengers.

     “I am here for a rest. I am not going to give away any more money in Britain,” he told newsmen.

     A Pan Am spokesman said the jumbo had been rechristened Young America in New York for the historic flight, but the aircraft carried the name Clipper Victor on its fuselage on arrival here.

     THE HUGE PLANE made most of the smooth flight at 33,000 feet.

     Richard Hobson, air correspondent of the British Press Association, who traveled on the jumbo, said: “From my position in one of the economy sections of the 747 where the seating is nine-abreast, divided by two aisles, was like being in a news theater. A film show—and the plane is equipped for them—would have completed the illusion.”

     Pan Am has received five of the 33 jumbos ordered. Trans World Airlines plans to start jumbo service in March and British Overseas Airways Corp. will receive the first of 12 jumbos early in April and hopes to get them in service in June.

     A British Airport Authority spokesman reported the first passenger cleared all baggage and airport formalities 34 minutes after the jet touched down.

     “IT DOESN’T LOOK bad at all,” he said.

     The spokesman gave this breakdown on times for clearing the jumbo’s passengers:

Time arrive 8:06 a.m. EST.
Doors open: 8:19.
First passenger off plane: 8:20
Last passenger off plane: 8:32.
First passenger into baggage hall: 8:34.
Last passenger into baggage hall: 8:57.
First passenger into immigration: 8: …
Last passenger out of immigration: 8:39.
First passenger into customs: 8:25.
Last passenger out of customs: 9:04.
First passenger to clear airport: 8:46.
Last passenger to clear airport: 9:05.

     Six Pan Am buses took the passengers into London.

—Honolulu Star-Bulletin, Vol. 59, No. 22, 22 Jan 1970, Page D-16, Columns 1–8

Pan American World Airways’ Boeng 747-121, N732PA, Clipper Storm King. (Aldo Bidini via Wikimedia)

The 747-100 series was the first version of the Boeing 747 to be built. It was operated by a flight crew of three and was designed to carry 366 to 452 passengers. It is 231 feet, 10.2 inches (70.668 meters) long with a wingspan of 195 feet, 8 inches (59.639 meters) and overall height of 63 feet, 5 inches (19.329 meters). The interior cabin width is 20 feet (6.096 meters), giving it the name “wide body.” Its empty weight is 370,816 pounds (168,199 kilograms) and the Maximum Takeoff Weight (MTOW) is 735,000 pounds (333,390 kilograms).

The 747-100 is powered by four Pratt & Whitney JT9D-7A high-bypass ratio turbofan engines. The JT9D is a two-spool, axial-flow turbofan engine with a single-stage fan section, 14-stage compressor (11 high- and 3 low-pressure stages) and 6-stage turbine (2 high- and 4 low-pressure stages). The engine is rated at 46,950 pounds of thrust (208.844 kilonewtons), or 48,570 pounds (216.050 kilonewtons) with water injection (2½-minute limit). This engine has a maximum diameter of 7 feet, 11.6 inches (2.428 meters), is 12 feet, 10.2 inches (3.917 meters) long and weighs 8,850 pounds (4,014 kilograms).

The 747’s cruise speed is 0.84 Mach (555 miles per hour, 893 kilometers per hour) at 35,000 feet (10,668 meters) and it’s maximum speed is 0.89 Mach (588 miles per hour/946 kilometers per hour). The maximum range at MTOW is 6,100 miles (9,817 kilometers).

The Boeing 747 was MUCH BIGGER than the Boeing 707 that it replaced. (CBS News/Boeing)

N736PA had initially been named Clipper Victor, but the name was changed to Clipper Young America for the inaugural New York to London flight when the 747 scheduled to make that flight—Clipper Young America—suffered mechanical problems. The 747 was hijacked on 2 August 1970 and flown to Cuba. After that incident, N736PA was renamed Clipper Victor — its original name. It was destroyed in a collision with another Boeing 747 at Tenerife, Canary Islands, 27 March, 1977.

Pan American Airways' Boeing 747-121 N736PA, Clipper Young America, at London Heathrow Airport, 22 January 1970. (Getty Images via BBC History)
Pan American Airways’ Boeing 747-121 N736PA, Clipper Young America, at London Heathrow Airport, 22 January 1970. (Getty Images via BBC History)

The 747 has been in production for 53 years. As of January 2022, 1,569 747s of all models had been built. 205 of these were 747-100 series aircraft. On 12 January 2021, Boeing announced that the final 747s, four Boeing 747-8F freighters, had been ordered by Atlas Air Worldwide Holdings, Inc. The final Boeing 747, N862GT, was rolled out of the factory on 3 October 2022. The production of the “jumbo jet” has come to a close.

The final Boeing 747, a 747-8F freighter, N862GT, is rolled out of the factory at Paine Field, 3 October 2022. (Image by PaineAirport.com via Twitter)

© 2023, Bryan R. Swopes

21 December 1988

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Clipper Maid of the Seas, Pan American World Airways' Boeing 747-121, at Los Angeles International Airport (LAX) 12 March 1987. (Ted Quackenbush via Wikipedia)
Clipper Maid of the Seas, Pan American World Airways’ Boeing 747-121 N739PA, takes off at Los Angeles International Airport (LAX) 12 March 1987. (Ted Quackenbush via Wikipedia)

21 December 1988: Pan American World Airways’ Flight 103 was a scheduled transatlantic passenger flight, originating at Flughafen Frankfurt am Main (FRA) with stopovers at London Heathrow Airport (LHR) and John F. Kennedy International Airport (JFK), with a final destination of Detroit Metropolitan Wayne County Airport (DTW).

The first leg from Frankfurt to London was flown with a Boeing 727. The transatlantic segment of Flight 103 was flown by a Boeing 747-121, N739PA, named Clipper Maid of the Seas. It departed Heathrow at 1825 hours UTC, with 16 crewmembers and 243 passengers. The 747 climbed to the north and leveled off at at 31,000 feet (9,449 meters) at 1856 hours.

At approximately 1903, a time bomb which had been placed inside luggage carried in the airliner’s cargo hold detonated. Explosive decompression magnified the effects of the bomb. The airliner broke into five large sections and fell to the ground at the town of Lockerbie, Scotland.

The impact crater of Boeing 747 N739PA at Sherwood Crescent, Lockerbie. The wings and fuselage center section struck here, 49.5 seconds after the explosion. 200,000 pounds (91,000 kilograms) of jet fuel ignited, destroying many homes. (Martin Cleaver/syracuse.com)
The impact crater of Boeing 747 N739PA at Sherwood Crescent, Lockerbie. The wings and fuselage center section struck here, 49.5 seconds after the explosion. 200,000 pounds (91,000 kilograms) of jet fuel ignited, destroying many homes. (Martin Cleaver/syracuse.com)

All 259 persons on board the 747 were killed, as were another 11 persons on the ground.

The time bomb is believed to have been placed aboard the airliner by agents of the Great Socialist People’s Libyan Arab Jamahiriya, acting on orders of the Brotherly Leader and Guide to the Revolution of Libya, Muammar al-Gaddafi. One of these, Abdelbaset Ali Mohmed al-Megrahi, was convicted of 270 counts of murder in a Scottish criminal court seated in The Netherlands. The defense twice appealed the case, but prior to a decision in the second appeal, al-Megrahi dropped his appeal and asked to be released from jail because it was believed that he would very soon die of cancer. The Scottish court did release him and he returned to Libya on 14 August 2009, on board Colonel Gadaffi’s personal aircraft. He reportedly died 20 May 2012.

Another suspect, Abu Agila Mohammad Mas’ud Kheir Al-Marimi, believed to have been the bomb maker, was recently taken into custody by the United States.

Boeing delivered N739PA to Pan American 15 February 1970. The airliner was originally named Clipper Morning Light. At the time of the bombing, it had accumulated 72,464 total flight hours.

The forward section of Clipper Maid of the Seas, near the village of Tundergarth, Scotland.
The forward section of Clipper Maid of the Seas, near the village of Tundergarth, Scotland.

The 747-100 series was the first version of the Boeing 747 to be built. It was operated by a flight crew of three and was designed to carry 366 to 452 passengers. It is 231 feet, 10.2 inches (70.668 meters) long with a wingspan of 195 feet, 8 inches (59.639 meters) and overall height of 63 feet, 5 inches (19.329 meters). The interior cabin width is 20 feet (6.096 meters), giving it the name “wide body.” Its empty weight is 370,816 pounds (168,199 kilograms) and the Maximum Takeoff Weight (MTOW) is 735,000 pounds (333,390 kilograms).

The 747-100 is powered by four Pratt & Whitney JT9D-7A high-bypass ratio turbofan engines. The JT9D is a two-spool, axial-flow turbofan engine with a single-stage fan section, 14-stage compressor (11 high- and 3 low-pressure stages) and 6-stage turbine (2 high- and 4 low-pressure stages). The engine is rated at 46,950 pounds of thrust (208.844 kilonewtons), or 48,570 pounds (216.050 kilonewtons) with water injection (2½-minute limit). This engine has a maximum diameter of 7 feet, 11.6 inches (2.428 meters), is 12 feet, 10.2 inches (3.917 meters) long and weighs 8,850 pounds (4,014 kilograms).

The 747-100 has a cruise speed of 0.84 Mach (555 miles per hour, 893 kilometers per hour) at 35,000 feet (10,668 meters). The maximum certificated operating speed is 0.92 Mach. The airliner’s maximum range is 6,100 miles (9,817 kilometers).

The Boeing 747 has been in production for 51 years. 1,568 have been delivered as of 7 December 2021. 205 of these were the 747-100 series. The U.S. Air Force has selected the Boeing 747-8 as the next presidential transport aircraft.

The Names. (StaraBlazkova/Wikipedia)

© 2022, Bryan R. Swopes

12 December 1991: In which a Boeing 747 goes supersonic.

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Evergreen International Airlines’ Boeing 747-121, N475EV, photographed at Hellinikon International Airport, Athens, Greece, 1 January 1991. The airliner has just been converted to a freighter. (Savvas Garozis)

12 December 1991: A Boeing 747 freighter operated by Evergreen International Airlines was en route from New York’s John F. Kennedy International Airport (JFK) to Tokyo, Japan, with an intermediate stop at Anchorage International Airport (ANC), Alaska, U.S.A. The 747 had a flight crew of six and no passengers.

At about 5:20 a.m., Central Standard Time (11:15 UTC), the 747 was cruising at Flight Level 310 (31,000 feet/9,449 meters) near Nakina, a small village approximately 150 nautical miles (173 statute miles/278 kilometers) northeast of Thunder Bay, Ontario, Canada.

The flight crew observed that the airplane’s Inertial Navigation System (INS) FAIL warning lights were on. Checking their instruments, they found that the 747 had entered a 90° right bank and was in a 30°–35° descent. It was rapidly losing altitude and gaining speed.

Before the crew could recover, N475EV had lost over 10,000 feet (3,048 meters) and reportedly reached 0.98 Mach in its dive. After regaining control of the 747, the crew made an emergency landing at Duluth, Minnesota, at 5:43 a.m., Central Standard Time.

On inspection, a large hole, approximately 3 feet × 15 feet (0.9 × 4.5 meters), was found in the leading edge of the right wing, inboard of the Number 3 engine. Three sheet metal panels had torn off, then struck the right horizontal stabilizer, denting its leading edge. On landing, a flap on the left wing fell off.

According to an article in the Seattle Times, an investigator for the National Transportation Safety Board confirmed that the 747 had exceeded its design speed of 0.92 Mach, but as the Flight Data Recorder had not yet been analyzed, “. . . he could not confirm reports that it reached Mach 1.25. . . .”

The Seattle Times reported the incident:

Dive! 747 In Unexplained Incident — Canada Investigating Automatic Pilot Controls After Near-Supersonic Scare

By Byron Acohido

Canadian authorities are scrutinizing the automatic flight controls of a Boeing 747-100 jumbo jet after the plane inexplicably rolled 90 degrees to its right and dove two miles at near-supersonic speed.

The incident occurred last Thursday as the plane, a passenger jetliner converted to a freighter, was cruising at 31,000 feet above Nakina, Ont., on a New York-to-Anchorage flight. The jet is owned and operated by Evergreen International Airlines, based in McMinnville, Ore.

The pilots righted the craft at 22,500 feet, then made a safe emergency landing at Duluth, Minn.

None of the six Evergreen employees on board, including the three-member flight crew, was injured, according to Dave McNair, investigator for the Transporation Safety Board of Canada.

McNair said the jumbo jet’s four turbofan engines functioned properly. He said a broad investigation would take several months and will include an examination of the sophisticated computers designed to fly the plane automatically for most of the flight.

“What we’ll be doing is looking at the entire autopilot logic and any associated logic,” he said.

At some point during the incident, three large panels beneath the leading edge of the right wing tore off, leaving a 3-by-15-foot hole on the forward, inboard section of the right wing.

The panels damaged the right flap (located on the trailing edge of the wing) and dented the right-side forward edge of the horizontal tail section, according to McNair and Boeing spokesman Chris Villiers. Upon landing, part of the left flap came off, as well, Villiers said.

Authorities said it was unclear whether the panels from the right wing came loose first and, thus, precipitated the roll and dive, or if the parts shook loose as the plane careened at a 30- to 35-degree angle of descent – more than three times a normal rate of descent. McNair said age of the 21-year-old aircraft is not believed to be a factor.

The 747-100 is designed to withstand a top speed of Mach 0.92 – nine-tenths the speed of sound, or more than 500 miles per hour at that altitude. McNair said the plane reached speeds faster than that during the dive, but he could not confirm reports that it reached Mach 1.25, because precise information from the flight-data recorder was not immediately available.

Tacoma aviation safety expert John Nance, a former 747 pilot, said it is plausible that the plane would begin to disintegrate once the speed surpassed its so-called “design limit.”

Nance described modern jetliners as “metallic eggshells, very strong when used exactly as they are designed to be used; very weak when not.”

The Evergreen incident occurred on the same day that whistleblower Darrell Smith, a former Boeing 747 computer analyst, made public an internal Boeing audit outlining major flaws in a software program used by a computer that senses the position of key moving parts on the Boeing 747-400, an advanced version of the 747-100.

Boeing officials said the computer Smith reviewed on the 747-400 doesn’t exist on the 747-100. The Evergreen plane was one of the first delivered from Boeing’s Everett plant in July 1970 to Pan Am.

Even so, Smith’s allegations and the Evergreen roll-and-dive add to a string of instances over the past two years in which alleged or apparent flaws in Boeing technology have become part of a heated air-safety debate:

— Last May, an electronically controlled engine-braking device, called a thrust reverser, inexplicably deployed as a Lauda Air 767-300ER jetliner climbed away from Bangkok, instantly flipping the plane into a supersonic crash dive. All 223 on board were killed.

Authorities still do not fully understand how a stray electrical signal, vibration or some other phenomena could have deployed the reverser. Meanwhile, Boeing has steadfastly declined to answer a call by the National Transportation Safety Board to upgrade pilot instructions on what to do if a reverser warning light illuminates in the cockpit during flight. Electronic reversers are used on all Boeing jetliners delivered in the past few years – nearly 1,700 planes all told.

— Last February, Hoot Gibson, a former Trans World Airlines pilot revealed nine complaints from pilots citing major control problems on Boeing 727 jets apparently related to a random, mysterious malfunction of the autopilot computer.

Gibson has waged a 12-year battle with the NTSB and Boeing to clear his name of allegations that he caused a TWA 727 to careen dangerously from a high altitude by attempting to improperly manipulate the controls to enhance the plane’s performance. Gibson, who wrestled back control of the plane at the last minute, maintains that a flaw in the autopilot triggered the dive.

— In April 1990, the NTSB, relying on Boeing technical data and analysis, ruled that the pilots of USAir Flight 5050 made the wrong decision to abort the takeoff of a 737-400 from New York’s LaGuardia airport on Sept. 20, 1989. The pilot decided to abort takeoff when the plane lurched left because the rudder was stuck full left. (The rudder, the upright section of the tail, is supposed to be in neutral for takeoff.)

The NTSB ruled that the pilots should have noticed the stuck rudder and, in any case, should have followed through with the takeoff, even with the stuck rudder. Two passengers were killed as the plane ditched into Bowery Bay.

The ruling upset pilots who felt little credence was given to scores of reports of problems with a new type “rudder trim.” Reports from pilots said it was moving the rudder without being commanded to do so.

—The Seattle Times, 19 December 1991

A year later, the Chicago Tribune reported,

Tom Cole, a spokesman at Boeing Commercial Airplane Co., said original flight tests of 747s conducted in 1969 and 1970 took 747-100 models to speeds of Mach 0.99.

In addition, Boeing knows one case in which a 747 operated by Evergreen International made an emergency descent at speeds that exceeded Mach 1, he said.

—Chicago Tribune, 20 December 1992

Following the December 1991 incident, N475EV was repaired and returned to service.

This was not the first time that 19638 had been damaged:

Boeing 747 19638 (RA003) with a nose boom during flight testing, 1969. (Jeff Ohlston/Boeing)

Boeing 747-121, serial number 19638, line number RA003, had made its first flight on 11 July 1969. Boeing used the aircraft for flight and certification testing. On completion of these tests, it was to be flown to Boeing’s Renton plant to be modified to production standards, refurbished, and then delivered to the new owner, Pan American World Airways.

While landing on Runway 15 at Renton Airport, at 11:11 a.m., 13 December 1969, 19638 struck an embankment about 20 feet (6 meters) short of the runway. None the 11 Boeing employees on board were injured. The Number 3 and 4 engines were damaged and caught fire. The right landing gear was pulled backward, but held to the wing by linkages and actuators. The flaps on the right wing were damaged. The right wing’s lower surface was punctured. The fires were quickly extinguished.

A video clip of the accident is available on YouTube:

N732PA was repaired and finally delivered to Pan American on 13 July 1970. The 747 was christened Clipper Storm King. (It was later renamed Ocean Telegraph.)

Pan American World Airways’ Boeing 747-121, N732PA, Clipper Storm King, photographed at London Heathrow, 30 August 1971. © Stephen Rendle (Image used with permission.)

Pan Am operated the airliner for nearly 21 years. It was sold to Evergreen International Airlines, 1 July 1991, and converted to an air freighter at Evergreen’s maintenance depot at Marana, Arizona. It was re-registered N475EV.

Evergreen flew N475EV until it was sold to Tower Air, 13 September 1994. Under new ownership, the Boeing 747 was again re-registered, to N615FF.

Tower Air Boeing 747 N615FF, photographed at Kai Tak Airport, Hong Kong. © Andrew Hunt (Image used with permission)

The FAA registered the 747 to Kalitta Equipment LLC, 3 August 2000. The N-number did not change. The airplane’s registration was canceled 30 June 2017.

© 2020, Bryan R. Swopes