1. Design Origins:
Transition periods sometimes require transition solutions. In the 1950s Douglas Douglas-6 and DC-7 piston aircraft and the Lockheed L-649/749 and -1040 Constellations were advancing to technological heights, but outside the pure jet engine. the unfortunate de Havilland DH.106 Comet I and those who power the new military aircraft has not yet reached the maturity of commercial aviation, he said. The compromise, at least in terms of speed, seemed to be the turboprop engine, which combines the elements of both and is already introduced by Vickers Viscount in the UK.
During this period, especially in 1954, American Airlines, which attracted Eastern & # 39; s interest, presented design specifications for what he saw as a new class of aircraft. These included a cruising speed of more than 400 mph, profitable operations in sectors ranging from 100 to 2,700 mph, a capacity of at least 65 passengers, and a short-range performance that could serve the country's 100,000 major buildings. airports.
In short, it was looking for more speed, comfort and economy than the current generation of quad motor vehicles, but would be able to perform multisectoral flights without the need to refuel and achieve profitability at a cost as low as 50 percent with load factors.
According to Robert J. Serling, entitled "The Electra Story: The Greatest Mystery of Aviation,“ “the American and the East wanted an equally well-versed aircraft in short and long-distance operations” (Bantam Books, 1963, p. 15). “This was mostly achieved by a thirteen and a half foot support that passes powerful airflow 9 feet from the wing area.”
To this end, Lockheed selected the US's first turboprop powered aircraft L-188, choosing the same type of C-130 Hercules design team and Allison T-56 engines that provide this type of power.
“Lockheed opened America's commercial jet era by hanging propellers on the jet engine, Jim according to Jim Upton in Lockheed L-188 Electra (Specialty Press Publishers and Wholesalers, 1999, p. 7). Araştırma Research separated from Lockheed convinced airlines that, even though their propeller-free jets are excellent in long-range fights, airlines will have an effective tool for segments that yield historically little or no profit (ie, yielding short-to-moderate results). . paths. "
The aircraft was the product of an almost-read equation: "Jet power + propeller efficiency = proper performance and economy."
In addition to the design team and the power unit, he shared another aspect of the manufacturer's lineage: his name. Its products borrow the designation of the double piston, as in the 1920s and 1930s, to identify a star, such as "Orion", "Vega", "Sirius" and "Altair". engine L-10 Electra, L-12 Electra Junior and L-14 Super Elektra.
Eastern and American, in 1955, respectively ordered 40 and 35 L-188 for the second generation Electras.
2. Design Features:
According to senior American Airlines Captain Arthur Weidman, who flies DC-3s, Convairliners, DC-6s, and DC-7s, "(Lockheed L-188 Electra) has a multi-purpose and strong profile. " "The nose is sharply inclined downward to provide good visibility on the ground and in the air. Then, the lines return straight across a perfect cylindrical body to provide a wider cross-section than the DC-7. gives a taut, smooth, sleek and streamlined appearance. Thin nacelles stand out like giant probes with minimal frontal resistance. "
With a length of 104.6-meters and a diameter of 11.4-meters, the Electra had large, square passenger windows.
One of the keys to his design was the wing. Mounted with significant dihedral and sporty square tips, which emerged in a very short time for the aircraft it supported, it was only 5.5 feet shorter than the fuselage, 99 feet long and offered both low drag and surveillance. The traction edge wings extended from the stem to the ailerons or just beyond the exhaust nozzles of the external engines, and almost 80 percent of the span was subjected to propeller washing to facilitate lift at low speeds.
Power was supplied by four 3,750-eshp (equivalent shaft horsepower) Allison 501-D13 turboprop; it has a 13.6-foot diameter, single rotation, hydraulically controlled, fixed speed, reversible pitch, four-blade propeller. Compared to the pure jet engine, the propeller jet has a reduction gear that drives both the propeller and additional gas turbine segment stages, resulting in a 90:10 thrust generation ratio or 90 percent of the propeller and 10 percent of the exhaust gases.
Ailerons, lifts and rudders are powered by push-pull, tube-connected hydraulic booster units, while the engine compressor bleeding air prevents icing of all control surfaces.
The aircraft's 5,520-US gallon fuel capacity was stored in a two-wing integrated tank fitted with two, 1,100 gallons internal and two 1,660 gallons external. In-flight fuel crossfeeding was only required in sectors with a distance of more than 1,800 miles.
The L-188 was based on a two-wheel, hydraulically driven, retracting tricycle undercarriage with provision for gravity free fall extension in the event of hydraulic or electrical system failures.
The integrated, trunk expandable air ladders, among other self-contained features, supported low-floor, equipment-independent location, facilitating returns at transit stations where refueling is not required in as little as 12 minutes.
Electra was flown as standard by a three-person cockpit crew, with a double-gas bomb dial on the sides of the captain and the first officer, and a flight crew station at the domestic terminal and a fourth crew member, traveling internationally and in the rear, on the left, otherwise the observer's eating place. occupy.
Although the passenger compartment configurations and densities vary by operator, Lockheed initially offered a variety of options that were facilitated by the installation of seat rails. A 26-inch corridor and 66 four side-by-side, 20-inch seats in a 38-inch area, or 85 five-in-one, 18-inch-wide in a 17-inch corridor can be installed; It has a six-row, tail-mounted hall arranged in a semicircle. The stern assembly, as in the standard medium, reduced the capacity to 83, while reaching 99 five in a maximum of 20 rows. Alternatively, 127 passengers were available in a six-inch, 32-inch pitch configuration, but structural modifications and additional exits were required to meet the evacuation criteria.
Maximum 6.55 psi differential with two engine-driven superchargers, provided the cabin is pressurized and the temperature maintained by radiant heating.
Luggage, cargo and mail were moved from two places, with hands accessible to the starboard gate.
With a maximum take-off weight of 113,000 pounds, the first domestic L-188A version had a range of 2,200 miles and reached a maximum speed of 373 mph and 448 mph.
"For the US's domestic operations, the L-188A had two basic versions with a capacity of 5,520 US gallons of fuel, and the L-188C with 900 US gallons more fuel and higher gross 116,000 pounds …," from 1945 According to Michael Hardy in World Civilian Aircrafts (Charles Scribner's Sons 1979, p. 93).
Its range was 3,500 miles.
3. Test Flights:
Captain Herman "Fish" Salmon Pilot, First Officer Roy Wimmer, Flight Engineer Laurie Hallard and Flight Test Engineer Bill Spreurer, L-188 Electra, made their opening flight from Lockheed Air Terminal in Burbank, California on December 6, 1957. "The softness and quietness of the aircraft (it immediately caught the eye). The vibration level was very low and the engines were so quiet that you could hear the following plane."
Following a 655-hour flight test program with four planes, on August 12, 1958, the program was approved five weeks in advance and allowed the customer to start the first delivery of aircraft 1007 on October 8 with Eastern Airlines two months later.
Acquisition of Electra's design and performance capabilities, as announced by the Airline Pilots Association evaluation committee.
"The members were impressed by the possible rapid application of power and the sudden aircraft response in climbing performance," he said. "He certainly surpassed his landing and raffle.
"High speed stability is good … good control response at launch speeds … responds well to the descent jet … cross winds and descent characteristics are most normal …
"The stall characteristics of this aircraft were very good in all configurations. There was no drop in a wing or any other negative trend.
“This committee is confident that manufacturers, operators, pilots and the public will be pleased with the safety, efficiency and economy records that will be provided.”
American Airlines Captain Arthur Weidman expanded upon it after his first flight of this type.
“Electra is the plane of every inch pilot, Douglas wrote Douglas J. Ingells,“ The L-1011 Story of TriStar and Lockheed ”(Aero Publishers, Inc., 1973, p. 124.) The first impression was that the plane took off. "functional beauty"
Despite its powerful prop jet turbines, it found that it was quieter than similar pistons accelerating in the cockpit during taxiing and acceleration.
“Ind He rushed down and climbed quickly,” he said. “Obviously, there was a lot of force in the propulsion (and p. 127) of the propellers to be placed on the visually large, flat blades of the propellers (and).
A throttle advance to the "flight regimen" stage triggered the aircraft's acceleration cylinder engines at a speed of 13,820 rpm, causing the L-188 to perform its rotation before it took place in a Piper Cub. performance.
“The low noise and vibration level makes the takeoff easier and the plane leaves… ((p. 129). "The high vibration and long, slow climb of reciprocating engines are a thing of the past."
Unlike obstacles on other planes, Electra's controls the wing angle, not the rotation of the engine, which remained constant throughout all flight stages. Therefore, although the push changes were only due to changes in the slopes, they had to be combined with the elevator entrances.
Climbing equaled 2,200 to 2,500 fpm and speeds exceeded 400 mph.
Lifting and wing efficiency are significantly improved by support washing on the surface.
Iyor More than a sixty-ton aircraft, it responds to control actions like warriors ”(p. 129).
The plane's power reserve was almost astronomical: it could climb any two engines and raise altitude on any one.
The landing only requires a short roll of deceleration supported by the necessary ground contact and brake applications and the reversible steps of the propellers.
4. Airline Operations:
Eastern Airlines, the first and largest of 14 original operators with 34 L-188As and six L-188Cs, entered service scheduled for 66 single passengers on January 12, 1959, as well as the sixth stern. New York (Idlewild) -Atlanta-Tampa, Miami-New York-Montreal and Detroit-Cleveland-Miami on many dual-sector routes. Between 1965 and 1977, it was the first and second part of the air shuttle (DC-9), connecting La Guardia to Boston and Washington.
American, the second operator with 35 L-188A, started Electra service on the Chicago-Midway line on the same day as Eastern in New York-La Guardia.
Ordering 15 L-188A, National Airlines presented 72-passenger and six-seat lounge interior and connected New York (Idlewild) to Miami from April 23, 1959.
Offering a similar 75/6 arrangement, Braniff served Texas, Dallas, Houston and San Antonio from New York-Idlewild and Chicago-Midway airports.
According to John Proctor, Western Western Airlines, declared a completely new dimension in jet-jet travel, commenced Electra-jet service on August 1, 1959 between Los Angeles, San Francisco, Portland and the West Coast of Seattle ”, Mike Machat and Craig Kodera "Props Jets: Transition of Commercial Aviation to the Jet Age" (Specialty Press, 2010, p. 91). "Two months later, turboprop flights were added to Salt Lake City, Denver, and Minneapolis, and the fleet was opened to five class, first-class aircraft configurations of 66 people. Their layout was missing a hall."
On September 18, 1959, with the first of 18 L-188Cs, the Northwest served the battle base in Minneapolis and operated an intercontinental segment from New York-Idlewild to Seattle. .
12 KLM Royal Dutch Airlines, an international L-188C with a capacity of 67, became Electra's sole European operator and was launched on December 9, 1959 on Amsterdam-Düsseldorf-Vienna, Amsterdam-Frankfurt-Budapest and similar roads. entry. What happened to the Middle East. The plane has Hamilton Standard propellers with round ends and cockpit navigator stations.
This species was used in a remote region, such as Hong Kong, Indonesia and Australia, according to the likes of Cathay Pacific, Garuda and Qantas, respectively.
5. Braniff Flight 542:
The result of the Air Line Pilots' Association, Electra's "safety, efficiency and economy record," was predictive, while the first of the three principles did not materialize.
From Houston to New York, Braniff Flight 542, the airline N-9705C, is the fifth L-188A of transportation and was delivered just two days ago. It is planned to use 188A aircraft. Passengers on a warm and humid night on September 29, 1959. There was no clue about the fate of the plane. Or was he there?
First Officer Dan Hallowell, one of the six crew members on board, commented to an Allison representative before he left, "This plane is getting funny." Hallowell could not be elaborated and the representative could not understand his results. He stated that there were no abnormalities in the aircraft's logbook, maintenance and trim. Perhaps it was nothing more than an uneasy feeling.
Electra divorced himself from the runway in 2244, 13 minutes later he was assigned to a height of 15,000 feet, 2300 at a relatively short cut to Dallas at 275 knots speed.
Five minutes later, after reporting his position in Leona, Texas, he was instructed to "follow Fort Worth 120.8 as often" and was recorded as "Transmission complete, 2307" in the registry.
It was the latter.
The next event was heard before the small town of Buffalo was seen by Texas, since most of the residents had already retired for the night. It was an attack on the senses. The tremors in the changing curtains and the deafening whistle preceded a slight roar that peaked in a thunderous cacophony. Like an exploding bomb, he then visually revealed himself as hurricanes of heavy metal fragments, breaking pieces of some large-scale ships. Finally, the nostrils were looted as the rain of jet-propellant kerosene rain, at a time when all the remains of Braniff Flight 542 and almost 100 L-188 carry 20,000 passengers daily.
Although witnesses from the predominantly farmland area describe various pre-crash sounds, perhaps the most accurate is not from humans, but when a farmer observes, "When the sound comes, every koon dog begins howling for miles." Impressed?
Reflected to the ground, to some extent, is the image of what shows in the air what causes the plane to fall and fall apart. A seemingly squeezed crater contained the forward hull section and several arms separated from the rest of the hull, and the remnants of the back of the periodic feet and then the shafts in place: the central cabin at 225 feet; vertical tail, rudder, internal stabilizers and tail cone 230 feet; A large section on the right wing of 1,760 feet; starboard stabilizer 2,020 feet; port stabilizer 4,080 feet; Motorized hub with number four at 5,300 meters; the left wing includes the engine cover and propeller number two and the fourth engine at 8,640 feet; 9,600 feet number one propeller and gear box; and a 9.2-inch cross section of the hydraulic line of the two and a half fuel tank, 2.3 miles. Indeed, a 17-mile linear debris pattern was stretched from the crater to the LEONA VOR.
The elaborate restructuring revealed that Electra opened his left flank, the fire exploded at this point, and the limbless plane shattered from gravity-induced forces, wandering the ground.
Part of the investigation focused on the land witness and explained his claims before being aware of the origin of the high-pitched sound in the sky, and perhaps showed that the propellers had reached supersonic speeds for some reason. The physiological responses of the collective coon dogs were also not reduced, because they reacted as if their voice had pierced their ears. But how and why? And if anything, what does all of this have to do with the first officer's comment on the öncesi funny trim ın of the plane before takeoff? Could this be the result of an autopilot or balancer failure or even a fuel imbalance?
And what was the significance of the signs of damage that revealed that the propeller number 1 rotated at an angle of 35 degrees from the normal plane of rotation? Wouldn't it be the natural consequence of stress and pressure as the left wing wears out? Or was it the reason?
Nevertheless, detailed research and analysis revealed that there was no definitive answer – there was no possible cause and therefore no design changes could be proposed to correct the undetected error or error.
Until 17.03.1960, it was concluded that the possible failure of the Braniff Electra accident to precisely determine the cause of death and all the losses on the ship. And that's exactly what happened that day.
6. Northwest Flight 710:
The N-122US was the first L-188C ironically delivered to Northwest Airlines and entered less than 1,800 hours ago, but would not be in service for a long time. From March 17, 1960 to Minneapolis-Midway, which operates as Flight 710, the first of its two parts is a one-minute fur minute; However, it quickly took off again, now reaching Miami, 1438 local time, 105,000 pounds gross weight, 18,000 meters, and seven minutes later I learned that the Indianapolis Center was on Millford, Illinois.
In 1513, Indiana, next in Scotland, advised the radio checkpoint in Indiana to 18 protect 18,000 in 15,000 and predict Bowling Green ’.
Fifteen minutes later, he was asked to contact the Memphis Center over the frequency of 124.6, which he responded to Flight 710 as "Accepted". It was the last message received.
The weather was clear, but according to later events, apparently it was not very cooperative. Explosions in which the powerful, unpredictable phenomenon called "clear air turbulence" (CAT) pierces Electra's desperate victim, releases two bubbles of white smoke, and then destroys a large black as fate is seen as two witnesses.
The plane, which was reduced to an air amputee, threw its right wing and held a little more than the handle of its left wing. At first, the indifferent, limb body continued straight and straight, but when the ailerons could not lift and desperate to build or correct a bank without them, they could no longer manage one of the Wright Brothers' three flight axes. It was scientifically defined 57 years ago and resulted in the imbalance of the above air and the withdrawal of gravity.
Nose bleeding, trailing smoke and throwing structure act like a missile from air to ground at a soy field near Tell City, Indiana at 618 miles / hour. By measuring snow, dirt, mud, and vegetation, Newton's Law of Third Motion – "there is an equal and opposite reaction to every movement" – is 250 feet.
The rest was a 30-meter wide, 12-meter deep cigarette smoke crater, molecular fragmentation and obliteration of 63 passengers and crew;
Can outdoor turbulence be the culprit?
The only important piece of debris was later discovered in the crater itself.
Serling, “The Electra Story: Aviation's Greatest Mystery” (Ser. Cit., P. 49), "The big hull made it telescopic and compressed into a mass of molten metal that was only one third of its total length." "Of the 63 people, there was not enough time to identify more than seven bodies. The aluminum body with coffins was so hot that five days later, a steam shovel picked up the still-burning parts."
Right wing, 11,229 feet severed from impact point. His tips were strangely reminiscent of the Braniff accident near Buffalo, Texas. What was the partner between the two?
One aspect was different. Clear air turbulence and a jet stream of more than 100 millimeters at 18,000 feet, the altitude of the Northwest flight, stopped the flight path at a 90-degree angle, affecting other planes at that time. But he begged the question: why, if they were so violent, could they not bear a similar fate?
The open air turbulence for all its features suddenly began to be seen by the Federal Aviation Agency. Although it exceeded the structural expectations of L-188, it was somewhat different from other propeller airplanes because it represented some degree of transitional technology: combining traditional uprights with still unstable turbines, ensuring that the speed limits between them were kept. for example, DC-6 and the resulting military jets.
Like adolescents trying to grow very fast, perhaps Comet had entered an area where he was not ready enough because the body was in high altitude areas with insufficient thickness skin indicators. Along with CAT, maybe it was a disaster.
The FAA, which landed the plane but could not determine the exact cause, chose to keep the Electra combined with the initial speed limit of 275 knots, but with the deactivation of autopilots and the installation of impact-resistant facilities. flight recording equipment. When it was discovered that this was the speed of the Braniff plane, it was reduced to 225 knots.
What exactly happened? Ultimately, the aircraft had been pre-tested before certification.
“… (But) Electra projects nowhere, never left end to end, thousands of hours of ground and test flight reports can not spread forty miles away, calculations in 20,000 separate design work or 7,000 pages of mathematical work – known as a“ rush mode bilimsel from a scientific phenomenon Was there any promise? Ling Serling (Ibid, p. 19).
7. Mystery Solved:
Both laboratory (theoretical) and aerial (practical) research and investigation, part of the Lockheed Electra Achievement Program or LEAP, explored the mystery behind the Braniff and Northwest accidents and required a ten-hour flight in two days with various loads, parameters, and even red line fastening speeds were discovered. Initially, they only proved the design integrity of the L-188, and even an uninterpretable clue finally emerged.
Energy radiates and applies its effects at its final destination. In the case of Electra, it was found that heavy motion loads had a much greater impact on the engines of outboard motors than in the structural tests revealed during severe turbulence penetration, as evidenced during flight experiments, producing a wing bending force from there to the ends. The California mountains, which produce hurricane-strong superstructures, are called “Sierra waves.. The turbulence they created caused damage to the aircraft's flight controls and structure.
Increased damage to engines 1 and 4, respectively, of Braniff and Northwest aircraft, respectively, is the result of uncontrolled impacts. Diagonal, sawtooth fractures showed the presence of pre-structural failure – cyclic, repetitive and strong oscillations – but what was unanswered was why the lack of turbulence in Buffalo, Texas caused the same phenomenon. Tell me in town, Indiana. What exactly caused the same devastating flutter in an atmospheric-like setback?
Then focus on the corresponding Electrons, which opposed each other in the installation, the engine air spontaneously changed themselves.
Analysis of the remains of the eight propellers showed that the number one engine on the Braniff aircraft was shaken for a reason. An excessively fast catalyst or condition caused the ends to reach sonic velocities, and this difference illuminated the truth. Both accidents were caused by propeller swirl mode.
Since a propeller has gyroscopic tendencies, it remains in the plane of rotation until dislodged by an external source and causes Newton to comply with "equal and opposite reaction" laws. In this case, while the propeller continued to rotate in one direction, the induced vortex mode disengaged it from its uniform rotation and caused it to vibrate differently.
If it is not humidified, dismantled or turned down, it develops a crazy trembling gyroscope, transmits its energy to the energy it is mounted on, in this case it spreads everything in its path and becomes infected with the wing or more precisely. The outer wing was the left, in the Braniff crash. Northwest accident, that's right.
A strut body failure on the second Electra's engine number four caused abnormal, multi-directional loads, eliminating the restriction that restricts the engine from moving up and to the left, causing the engine to experience large revolutions. They eventually broke the propeller reduction gearbox.
As shown in the NASA Langley wind tunnel with the eighth scale L-188 model, the result is expressed as follows.
"In the Nacelle region, the impeller automatic clamping process, involving the connection of simulated damage, gyroscopic and aerodynamic forces, occurred in a continuous, wobble movement of the spinning propeller itself."
The design flaw of the aircraft did not necessarily require insufficient strength of the nasal structure, but did not include sufficient rigidity. Influenced by previous damage, he reacted to the chain of destruction. After shaking the engine, he had a propeller, and while his motion was transmitted to the outer channel, the flexed, flapped and broken, gripping the limbless body to gravity.
Although open-air turbulence is an open spark that ignites the chain reaction in the Northwest accident, it can be presumed that only a hard landing not specified in the registry serves as a similar ignition in the Branch. Couldn't it have been the reason behind this early, yet catastrophic wobble, that the first officer's plane was "funny cut"?
And dogs don't lie, raccoons or otherwise. The supersonic speed of the propeller tips reacted to a collective howl, as it emitted painful sounds that almost pierced the hypersensitive ears.
A Lockheed-funded replacement program of $ 25 million, applied to both in-service and assembly line planes, was installed in the engine's reduction gearbox, which required structural improvements and installation of the upper and lower supports, referred to as "vibration isolators", resulting in a seven percent increase in rigidity. The air intake was relocated and new, more powerful engine mounts prevented lateral movements and all added 1,400 pounds of structural weight.
The aircraft were FAA-certified on December 30, 1960 and were redesigned as Elect Electra II's ve and Süper Super Elections ları to replace airlines that were understandably misidentified as a result of accidents.
8. Sunset Program:
The last three of the 170 L-188A and -C & apos;, registered PK-GLA, -GLB and -GLC were purchased by Garuda Indonesian Airways, and their type was rented for the second time as Central and South American aircraft. kargo gömlekleri, yangın bombardıman uçakları ve yasaklanmış P-3C Orion antisubmarine devriye uçağının platformu olarak. Alaska merkezli Reeve Aleutian Airways, yüzyılın başlarına kadar planlanan hizmetlerle üç saf yolcu ve kombi örneği işletti ve bu da türün sağlamlığını ve güvenilirliğini gösterdi.
Ancak, piston ve saf jet dönemleri arasındaki ana hat köprüsü olarak, geçişi kısa sürdü ve hemen yerini Sud-Aviation SE.210 Caravelle, Boeing 727-100 ve Douglas DC-9'un beğenisine aldı. 1960'lı yılların ortalarında -10 ve -30.
Hardy, Michael. "1945'ten beri Dünya Sivil Uçakları." New York: Charles Scribner'ın Oğulları, 1979.
Ingells, Douglas J. "L-1011 TriStar ve Lockheed Hikayesi." Fallbrook, California: Aero Yayınevi, Inc., 1973.
Proctor, John; Machat, Mike; ve Kodera, Craig. "Sahne'den Jetlere: Ticari Havacılığın Jet Çağına Geçişi, 1952-1962." North Branch, Minnesota: Özel Basın, 2010.
Serling, Robert J. "Electra Hikayesi: Havacılığın En Büyük Gizemi" New York: Bantam Kitapları, 1963.
Upton, Jim. "Lockheed L-188 Electra." North Branch, Minnesota: Özel Basın Yayıncıları ve Toptancıları, 1999.