The Gimli Glider, July 23, 1983

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Today in 1983, Air Canada Flight 143, on its way from Montreal to Edmonton via Ottawa, ran out of fuel and lost both engine thrust and electrical power at 41,000 feet. The crew's amazing actions in the following minutes saved the lives of the plane’s passengers. The causes of the incident ensured that the story of the Gimli Glider will serve as a cautionary tale in aviation circles for generations to come.

Air Canada Flight 143 was a Boeing 767, an aircraft model that had only been in service for two years at that time. The particular plane in question had not yet been in service for four months by July, 1983. It was the first large aircraft flown by Air Canada that only required a pilot and co-pilot and eliminated the position of flight engineer, the person who would normally have been responsible for calculating the fuel load necessary for a given flight. This omission would become important during the post-incident investigation.

Earlier on the day of the incident, the aircraft had been flown from Edmonton to Montreal. A pre-flight inspection by a maintenance engineer showed that the plane’s Fuel Quantity Indicator System (FQIS) was malfunctioning. The FQIS had a built-in redundancy in which the plane’s remaining fuel was measured by two separate sensors and the results were compared to ensure accuracy. The pilot and co-pilot were shown only one amount however, assuming the two measurements agreed. The engineer in Edmonton noticed that the FQIS quit working entirely unless he pulled the fuse for one of the measuring sensors. He informed the pilot of this and the flight was made with the FQIS working with only one measurement sensor.

Once in Montreal, another Air Canada engineer looked at the FQIS and reconnected the second measuring sensor, which caused the system to stop working again entirely. The engineer was then called away to check another system and left the FQIS in non-working order. The new flight’s captain, Robert Pearson, and First Officer Maurice Quintal were told about the FQIS problem by the pilot who had flown the plane from Edmonton to Montreal earlier in the day. However, they were under the mistaken belief that the FQIS was not working at all on the earlier flight, so were not alarmed when the gauge was blank as they entered the cockpit. Instead of grounding the flight, the crew decided to measure the fuel via dripstick and track fuel consumption via the Flight Management Computer.

It was during this time that a critical error was made. In 1983, Canada was in the middle of a nation-wide conversion from Imperial units to the metric system. The 767s being put into service with Air Canada were the first to use the metric system; every other aircraft model in the fleet still used Imperial measurements. In the process of converting liters to kilograms to pounds to gallons, a wrong conversion factor was used and the aircraft ended up with less than half the necessary fuel on board for the trip. After the plane finished the first leg of the trip by landing in Ottawa, Captain Pearson had the fuel measured again via dripstick. He again made a conversion error and the aircraft took off with the 69 passengers and crew onboard, heading towards Edmonton with no chance of reaching there.

Air Canada Flight 143 was over Red Lake, Ontario when an alarmed sounded, notifying the crew that there was a fuel pressure problem on the plane’s left side. The pilots turned off the port side fuel pump, assuming it had failed. This was not a serious problem as gravity could still feed fuel to the aircraft’s engines. The alarm sounded again a few seconds later, this time accompanied by the failure of the left engine. Captain Pearson decided to divert to Winnipeg and land using the 767’s one running engine. As they talked to air traffic controllers, yet another alarm told the pilots that both engines had now failed. Most of the cockpit instrumentation went dark, leaving only a few battery-powered basic instruments. The plane’s ram air turbine, a small generator powered by the forward motion of the aircraft, quickly deployed and maintained power to the hydraulic system, which meant that the pilots could at least somewhat control the plane. Air Canada Flight 143, over six miles above the earth, was now a giant glider.

Fortunately for everyone present on the Air Canada flight that day, Captain Pearson was an experienced glider pilot. Up to that point in its short flight history, no one had made an unpowered landing in a Boeing 767. In fact, the aircraft’s emergency checklist had no section for such a contingency. Captain Pearson guessed that the best glide ratio speed for a 767 was 220 knots, or 250 miles per hour. Using the plane’s altimeter and information from air traffic controllers, the pilots determined that they were maintaining a glide ratio of 12:1; that is, 12 miles of forward travel for every one mile of descent. They were not going to make it to Winnipeg.

First Officer Maurice Quintal, who had once served as a Royal Canadian Air Force pilot, remembered the Air Force Station at Gimli, Manitoba. It had been closed since 1971, but it still boasted two parallel runways nearly 7,000 feet long. If they could make it there, their chances of making a safe landing would improve dramatically. They would have to glide for 17 harrowing minutes over dense forest, maintaining a constant rate of descent the entire way.

As the airliner approached the old air force base, the pilots were faced with three problems: first, they were too high and going too fast to make a head-on approach landing as they had planned. They considered trying to fly a 360 degree turn in order to lose speed and altitude, but Captain Pearson was afraid they would not have enough momentum left for a safe landing. He decided to execute a forward slip, a maneuver in which an aircraft stays on track while slipping sideways. This causes an immediate loss of speed and increases the rate of descent.

This introduced the second problem. As the plane slowed, the ram air turbine began slow down, which meant the hydraulic system began to lose pressure. This made the aircraft more difficult to control and made use of the wing flaps impossible. This meant the plane would still land at a higher than normal speed.

The third and most harrowing problem presented itself as the plane lined up with one of the runways. What neither Pearson or Quintal knew was that while one of the runways of the old Air Force base could still be used, the other one had been converted into a drag strip complete with a guardrail running down the centerline. A Winnipeg auto club was, coincidentally, hosting a family day at the converted airfield that day, so the apron of the non-converted runway was being used as a parking space and was full of cars, trucks and trailers. The drag strip would have to do.

The pilots tried to lower the 767s landing gear using gravity, but the nose wheel failed to lock into position. As the plane made contact with the runway, Captain Pearson pushed the brakes as hard as he could, which caused two of the plane's landing gear tires to blow. The nose wheel collapsed and folded back up into its well, leaving nothing to hold the front of the aircraft up. The underside of the nose scraped along the runway until it came into contact with the guard rail, which raised the front of the plane a little and helped to slow it down more rapily.

As the Air Canada craft came to a halt, a small fire began in the nose area. People working at the drag strip, already standing by with fire extinguishers in case one of the cars caught on fire, quickly put out the blaze. None of the passengers and crew were hurt by the landing itself. Several passengers were injured while sliding down the rear emergency chutes, which were at too steep an angle due to the higher than normal height of the rear tail section. These injuries were treated by a doctor who happened to be on-scene at the time of the landing.

Investigators eventually found both the mechanics and pilots at fault in the Gimli glider incident. However, the pilots and crew were praised for handling the situation with professionalism and skill. Captain Pearson was demoted for six months and First Officer Quintal was suspended for two weeks. Quintal was promoted to Captain six years later and Pearson returned to his captaincy until his retirement in 1993. The Boeing 767, thereafter known as the Gimli Glider, remained in service with Air Canada for the next 25 years. In January, 2008, it was flown to the Mojave Airport and is slowly being dismantled for parts. On board for that final flight was the entire flight crew from that day in July, 1983.

Memorial Day, May 31, 2010

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“July 14, 1861
Camp Clark, Washington

My very dear Sarah:
The indications are very strong that we shall move in a few days—perhaps tomorrow. Lest I should not be able to write again, I feel impelled to write a few lines that may fall under your eye when I shall be no more.

Our movement may be one of a few days duration and full of pleasure - and it may be one of severe conflict and death to me. Not my will, but thine 0 God, be done. If it is necessary that I should fall on the battlefield for my country, I am ready. I have no misgivings about, or lack of confidence in the cause in which I am engaged, and my courage does not halt or falter. I know how strongly American Civilization now leans on the triumph of the Government and how great a debt we owe to those who went before us through the blood and sufferings of the Revolution. And I am willing—perfectly willing—to lay down all my joys in this life, to help maintain this Government, and to pay that debt.”

So begins a letter from Major Sullivan Ballou of the 2nd Rhode Island Volunteers to his wife, written a week before the First Battle of Bull Run, the first major engagement of the US Civil War. The Major wrote prodigiously to Sarah and she received more upbeat letters written in the days before and following his July 14th update from Washington D.C. But this letter became his most famous, mainly because of its inclusion in Ken Burns' Civil War documentary series, first aired in 1990. As with many other mementos of wars past, it has come to represent not just a man and the war in which he fought, but a nation's desire to seek something honorable and just from the loss of so many in battle over the past 235 years.

Today, May 31st, is Memorial Day in the United States, the day on which we honor those who have given their lives while serving during wartime in our nation’s military. Over the more than 140 years of its existence, the Memorial Day weekend has also come to represent the beginning of the summer season.

Memorial Day began as Decoration Day in Waterloo, New York in 1866. A decoration day of sorts occurred in Charleston, South Carolina in May 1865 at the site of a former Confederate prison camp, but Waterloo is given most of the credit for creating the day as we now know it. The village was home to General John Murray, who was a friend of General John Logan, the head of a veterans’ organization called the Grand Army of the Republic. Logan pushed for a national observance on May 30th, a date in which no battles took place during the then-recent Civil War. The day was originally intended to honor those who died during that conflict, but was soon extended to include those who have paid the ultimate price in all the nation’s wars. The term Decoration Day was used because cemeteries were generally adorned with flags and flowers to honor the fallen. Although the term Memorial Day first appeared in print in 1882, it did not come into common use until the time of the Second World War in the 1940’s.

In 1968, the US Congress moved Memorial Day from May 30th to the last Monday in May. This created a three-day weekend, something that critics of the change point to as one of the reasons the holiday seems to have lost its meaning to so many Americans.

History is full of stories of men and women who showed unbelievable courage under fire even though they invited their own deaths in the process. While we rightly recognize these heroes, it is also important to remember those whose names have been lost to history but whose sacrifices were no less honorable. By the end of the Civil War in 1865, nearly every American had lost a family member, friend or co-worker. During two world wars, Americans again felt that ultimate sacrifice close at hand; as my father said of the neighborhood in which he grew up during the 1940's, “There were a lot of gold stars hanging in peoples’ windows by the end.”

The past 60 years have seen the general public in the United States become increasingly distant from the military. Even with combat taking place in Iraq and Afghanistan as I write this, many Americans personally know no one serving in the military. Our armed forces are smaller as a percentage of the population now than they have been since the end of the Revolutionary War and a draft has not existed for 37 years. Yet men and women from every walk of American life have their lives taken almost daily by war; some of their names will only be remembered by those who loved them. While we can debate the merits of any war, those who give their lives during it do so for us and for generations not yet born.

Lower Manhattan was still engulfed by smoke and dust in September, 2001 when National Public Radio's news program 'All Things Considered' aired a segment in which American college students were asked if they would consider joining the military to fight in what was not yet being called the War on Terror. One young man, apparently stunned by the question, responded that he would not because “I have plans for my life.” I thought of the hundreds of thousands of American men and women, many of them close to the respondent's age, who had their plans put on hold for all of eternity. Their journeys ended at places like Bunker Hill, New Orleans, Veracruz, Gettysburg, Belleau Wood, Normandy, Inchon and Khe Sahn. The first decade of the 21st century would add over 5,000 names to the list of those who have paid the ultimate price in the service of their nation. The true cost of these losses can never be measured. The best we can do is honor their sacrifice and keep it alive in our collective memory as a people.

In addition to the Americans who have died in service to our nation over the last 235 years, I ask that you also remember today those from around the world who have given all while fighting in common cause with our country. Most of the nations of Europe and many other countries around the globe have sacrificed not just to protect their own interests, but to ensure the continuance of our way of life. To them and their fallen go the thanks of a grateful nation.

Sullivan Ballou, the author of the letter which I quoted at the beginning of this episode, died two weeks after writing it from wounds received during the First Battle of Bull Run. It was never mailed, but was instead turned over to his family when his remains and a few belongings were returned to Rhode Island. Sarah Ballou, 24 years old and the mother of two sons in 1861, never remarried; she died in 1917 and is buried with her husband in Providence.

Khrushchev Demands an Apology, May 16, 1960

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Today in 1960, Soviet Premier Nikita Khrushchev demanded an apology from US President Dwight Eisenhower for an incident in which a CIA U-2 aircraft was shot down over the Urals region of the Soviet Union. It was the latest shot in a battle of wills between two nations who had been at direct odds for most of the previous 15 years and would continue to fight the Cold War for another 30.

In early 1945, American and Soviet forces met at the Elbe River in Germany, each force having fought their was across Europe, but from opposite directions. These two nations had been, along with the other Allied powers, united in their goal of destroying the Nazi war machine. Hugs and handshakes were exchanged that day, but the euphoria of an Allied victory in Europe soon turned to distrust. Two years later, East and West would face off over the fate of West Berlin, an island of democracy in the middle of the Soviet-controlled eastern half of Germany. A shooting war was avoided, but a new type of conflict, soon to be called the Cold War, had begun. It would shape the world for the rest of the 20th century and beyond.

By 1960, 15 years after the end of the Second World War, most of the world was divided into two camps: one dominated by the United States and the other by the Soviet Union. Both nations had extensive stockpiles of nuclear weapons ready for use. It was a deadly stalemate, with neither side willing to force the ultimate issue for fear of bringing an end to civilization. Both sides spent billions of dollars on different war-fighting technologies, but in the United States the general assumption was that at least technologically, superiority lay on the side of democracy.

That assumption was shaken to its core on October 4th, 1957 when the Soviets launched Sputnik-1, the world's first artificial satellite. It was crude compared to what would come just a few years later, but to the Western imagination it was a giant leap forward in technology. The 185 pound sphere transmitted a regular pattern of signals at frequencies easily picked up by amateur radio enthusiasts all over the world. For 22 days, until Sputnik's batteries failed, the world could plainly hear the sound of Soviet achievement.

Today, we remember the launch of Sputnik-1 as the beginning of the Space Race. It also lent credibility to those in the US government who believed that a “missile gap” existed between the United States and the Soviet Union, with Moscow having a larger missile arsenal than Washington. Soviet Premier Nikita Khrushchev, never one to let a good panic go to waste, played on Americans' fears by claiming that Soviet intercontinental ballistic missiles (or ICBMs) were numerous and advanced. This was not the case, but the launch of Sputnik on top of an ICBM argued otherwise. The order from the Eisenhower White House was clear: more had to be known about the USSR's missile program and other advanced military weaponry.

Enter the Lockheed U-2, nicknamed the Dragon Lady. This incredible spy plane was the brainchild of Kelly Johnson, who headed Lockheed's secret Skunk Works facility in Burbank, California. It was an ungainly creature with the adapted fuselage of a fighter married to the giant wings of a glider. Johnson guided the creation of the U-2 from paper to flying prototype in less than a year; it first flew from Groom Lake (now called Area 51) in August 1955. By summer, 1956, U-2s flown by CIA pilots were taking pictures of the Soviet Union from 70,000 feet, an altitude too high for the Red Air Force's fighters or, it was thought, their surface-to-air missiles.

Soviet officials were made aware of the U-2 flights conducted in 1956 from the surprised reports of their nation's radar operators. Official complaints were made to Washington and Eisenhower put a stop to flights over the nation, although flights over other Eastern Bloc countries were still allowed. The President's rationale was two-fold: first, he did not want Khrushchev to believe the flights were being used to create target lists for a preemptive nuclear strike, although the Air Force certainly gleaned much targeting date from them. Second, he feared the loss of a U-2 to a missile or mechanical problem while on a mission. Such a loss would be highly embarrassing to the United States and could increase already-high Cold War tensions.

Concerns over the missile gap caused Eisenhower to reconsider his ban. In early April, 1960, the first deep penetration flight over the Soviet Union in almost four years began in Pakistan and ended in Iran, both nations having consented to allow the U-2 flights to begin and/or end at air bases within their borders. The second flight, originally scheduled for April 29th but delayed due to bad weather over the flight path, took off from Pakistan on May 1st, 1960. The pilot was CIA employee and former Air Force Captain Francis Gary Powers. His flight was supposed to be a lengthy one that flew over several sites of interest before landing in Norway.

What no one in the United States or Pakistan knew was that the Soviet Air Defense Forces were on high alert and waiting. The April flight had been tracked and intercepts attempted with fighter aircraft to no avail. The word had been passed from Moscow to the commanders of the various air defense commands in the Soviet Union: the next flight would not be allowed to leave the USSR's airspace once it entered. Every fighter within range of the plane's course was to attempt an intercept and ram the U-2 if necessary.

What made the difference on that May 1st were not the fighters that zoomed underneath the U-2 as it flew on its mission, but a surface-to-air missile known to Western observers as the SA-2 Guideline. The SA-2 was first deployed in 1957 in the Soviet Union but it was not believed it could reach the 70,000 foot altitude at which Powers' plane flew. At least three of the missiles were fired at the U-2, although this number varies to as high as 14 depending on the source. What is known for certain is that Francis Gary Powers' aircraft was shot down, along with a MiG-19 trailing him, by an SA-2 over Degtyarsk, a small town east of the Ural Mountains in Russia.

Within hours, President Eisenhower knew he had a problem on his hands. Over the next four days, a cover story was conceived. NASA released a press memo stating that one of the organization's aircraft was missing somewhere north of Turkey and that the pilot had reported problems with his oxygen equipment before losing contact with ground controllers. The American press was then shown a U-2 sporting the NASA agency logo and colors.

The next day, Soviet Premier Nikita Khrushchev announced that a spyplane had been shot down over his country, but gave no further details. The White House took this to mean that the pilot of the craft was dead and the plane heavily damaged. With these assumptions in mind, the Eisenhower Administration released a reiteration of its cover story stating that the spyplane in question was actually a weather research aircraft that must have strayed into Soviet airspace after the pilot lost consciousness due to the problem with his oxygen system. The story claimed there was never any intention to violate the airspace of the USSR.

On May 7th, 1960, Khrushchev played his trump card when he said: “When I made my first report I deliberately did not say that the pilot was alive and well… and now just look how many silly things [the Americans] have said.” Gary Powers, along with a CIA-issued suicide pin to be used in case of imminent capture, was in Soviet custody. His plane was recovered almost intact, its self-destruct charge never having been armed. The United States government had been caught in a gigantic lie.

According to several of his biographers, Khrushchev believed he had developed a strong personal relationship with President Eisenhower. When word of the U-2 shoot-down reached him, the Soviet Premier assumed the overflights must have been resumed by the CIA without Eisenhower's knowledge. However, the President was quick to admit he had ordered the flights, lest the American public and US allies fear that rogue elements in the intelligence establishment were acting on their own. The flights were, he said, “a distasteful necessity.”

The shoot-down of Gary Powers and the ensuing exchange of words between Washington and Moscow all occurred during the first two weeks of May, 1960. As it happened, there was a scheduled meeting, called the Four Powers Paris Summit, scheduled to begin on May 16th. In attendance would be President Eisenhower, Premier Khrushchev, British Prime Minister Harold Macmillan, and French President Charles DeGaulle. It was an important summit and one that Khrushchev was not quick to abandon. He did, however, believe that he needed to confront the American President. The two men had not spoken directly since the May 1st incident, so neither knew what to expect from the other in Paris. Upon his arrival on May 16th, Khrushchev gave a statement in which he demanded an apology for the overflights and a promise they would be halted. President Eisenhower released his own statement which contained no apology but offered to begin negotiations for what would become the Open Skies initiative, by which both nations would have monitored and scheduled use of each others' airspace for basic monitoring purposes.

Khrushchev had already decided to leave the summit, which he did on the same day. His statement was released to the public shortly thereafter and before Eisenhower's statement had been read, an act seized upon by the three other nations present as a sign that the Soviet Premier intended to wreck the summit regardless of Eisenhower's actions. Whether this was poor timing or a deliberate act of subterfuge remains unknown.

Eisenhower, who had scheduled a visit to the Soviet Union for later in 1960 but had his plans cancelled by the Kremlin, never met with Khrushchev again. His two terms in office ended in January, 1961 with the inauguration of John F. Kennedy, who would have his own showdowns with Khrushchev over the Bay of Pigs invasion, the building of the Berlin Wall and the Cuban Missile Crisis.

The Soviet Premier remained in power until 1964, when he was removed by a group of younger leaders who accused Khrushchev of numerous policy failures and erratic leadership. He was allowed to retire and received a pension, something that had never happened to a former Soviet leader. He had led his nation after years of terror imposed by Josef Stalin; even though he was in Stalin's inner circle for years, he was considered a reformer by his contemporaries.

Francis Gary Powers languished in a Soviet prison for almost two years until he was exchanged for spy Rudolf Abel in February, 1962. He did not receive a hero's welcome and his dismissal from CIA service was almost a given. He flew as a test pilot for Lockheed from 1963 to 1970, but was terminated from the position when he wrote a book about the U-2 Incident which received a great deal of negative publicity. He died in 1977 while flying a news helicopter for Los Angeles TV station KNBC. He is buried in Arlington National Cemetery.

The remains of the U-2 aircraft Powers flew can be viewed today at the Central Museum of Armed Forces in Moscow. The display also includes his survival pack and other related items. A small piece of the plane was returned to the United States and is on display at the National Cryptologic Museum at Fort Meade, Maryland.

The US Air Force continues to fly the U-2, although the equipment it carries has changed dramatically. It has been used extensively in Afghanistan for consistent real-time monitoring of enemy forces, a service that satellites can only provide for brief periods of time.

The Changes, May 15, 2010

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Thoughts on Direction, April 26, 2010

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Sorry, no transcript tonight.

The USS Thresher Lost, April 10, 1963

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Today in 1963, the USS Thresher, an American nuclear-powered attack submarine, sank in the Atlantic Ocean 220 miles east of Cape Cod, Massachusetts. Everyone on board-129 officers, enlisted men and civilian technicians-went down with the ship. The disaster shocked the world and changed the way the US Navy operates and maintains its submarine fleet.

The Thresher was the lead ship in what was planned to be a 14-ship class when she was commissioned in August, 1961. She used a proven nuclear reactor design (the S5W built by Westinghouse) and carried four torpedo tubes amidships to make way for new and powerful bow-mounted sonar equipment. Her normal crew compliment was 16 officers and 96 enlisted men. Thresher could dive to 1,300 feet and run at over 30 knots (or 35 miles per hour) submerged. She was designed to hunt and kill Soviet submarines and surface warships and was the finest war machine her country could produce for that task.

In the spring of 1963, the Thresher was coming out of her first refit period and was made ready for post-overhaul trials. On April 9, the sub and her escort, the submarine rescue ship USS Skylark, headed for open ocean off the coast of Massachusetts. The next morning, she began deep-diving tests, staying in contact with the Skylark via underwater telephone.

Communications between the two ships soon became garbled. From what could be made out, Skylark reported that the Thresher had experienced some sort of difficulty and was still diving. Finally, a short message was understood clearly “...minor difficulties, have positive up-angle, attempting to blow.” It was the last message the submarine would ever send. Two days later, the Navy announced to the world that Thresher and aboard her were lost.

The water in the area of the sinking is 8,400 feet deep, far deeper than any normal submarine could go. The Navy used the deep-diving bathyscaphe Trieste and oceanographic surface ships to find the wreckage. Eventually, the ship was found to be in six major sections; smaller debris was found in an area of about 134,000 square meters. 

A Naval Court of Inquiry determined that the ship probably sank due to a failure in the saltwater intake and piping system on the ship, which was not welded but used silver brazing to hold pipe joints together. Post-overhaul tests using ultrasound equipment found that 14% of the Thresher's brazed joints were problematic, but this was not considered a large enough risk at the time to warrant repair. The failure of one or more brazing joints at test depth could have caused the submarine to take on more water than the ship's ballast tanks, which create buoyancy, could have compensated for.

Later tests also showed that moisture in the sub's high pressure air flasks, which are used to blow seawater from the ballast tanks, could have caused ice to form inside the piping to the ballast tanks, leading to the flasks' inability to clear seawater from the ballast tanks. This would have made it impossible for the Thresher to surface.

Another problem, this one operational, could have contributed to the loss of Thresher. The officers and enlisted men tasked with running the ship's nuclear reactor received two years of intensive training in the Navy's Nuclear Power Program. At that time, the thinking was that in the event the reactor was shut down due to an electrical short or manually, it was imperative to keep the reactor warm so it could be restarted quickly. This means the secondary side of the reactor plant, which produces the steam which ultimately drives the vessel, would need to be cut off, leaving the submarine with no propulsion. Thresher's Reactor Control Officer was not on the boat the day of the loss---he was home with his wife who was recovering from an accident. Thus, the reactor plant was supervised that day by an officer only recently graduated from Nuclear Power School. Although we have no way of knowing if the rules were followed, it would have been drilled into every Power School officer to close the main steam valves leading to the ship's twin turbines if the reactor SCRAMed, meaning shut down. This likely occurred as seawater entering the aft of the boat shorted out electrical panels. Once shut, those valves had to be opened by hand. With Thresher sinking tail-first past her crush depth, it would not have been humanly possible to open those valves before pressure from the ocean outside crushed the sub. Would a more experienced Reactor Control Office have saved the ship by using all the steam at his disposal to drive the ship to the surface? We'll never know.

As a result of the loss of the Thresher, the Navy instituted the SUBSAFE program designed to ensure proper construction and maintenance of any component of a submarine which comes into contact with seawater. No SUBSAFE-certified ship has ever been lost.

The US Navy continues to monitor the area of the Thresher sinking to ensure that harmful levels of radiation are not released into the area. To this day, the nuclear fuel remains intact in the reactor and radiation remains typical of worldwide background levels.

The loss of the USS Thresher resulted in design changes to the other 13 ships of the class. The second ship of the class, the USS Permit, assumed the role of class leader after loss of Thresher. The last Permit-class submarine was retired from the US Navy in 1994.

IBM System 360 Introduced, April 7, 1964

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Today in 1964, the International Business Machines Corporation, more commonly known as IBM, announced its System 360 line of computers.  The System 360 represented a milestone in computer history that helped IBM to become the largest computer company in the world. The “360” in the name indicated the 360 degrees of a circle, meaning that the System 360 was designed to be a single computer  family for all types of computer work. In the 1960s, this mainly meant doing both business administration-type tasks and computation-intensive engineering tasks. Previously, computers had been designed to do one or the other pretty much to the exclusion of anything else.

For those unfamiliar with the computers of the 1960s, it is worth pointing out how the System 360 machines looked. They were large refrigerator-like boxes, located in special computer centers with air conditioning and powerful power supplies, and tended to by specialists in white coats.  A single computer could occupy several cabinets, and have many tape drives, disk drives, printers, and punched card readers attached.

Most importantly, the System 360 was not a single computer, but rather a whole range of computers with different price points and performance levels. Initially, IBM announced six different models and, over the coming years, many more were introduced. These computers would all run the same software programs, and let customers upgrade to bigger machines as their businesses grew. In today’s computer market, this is something we take for granted. For example, we can buy a 300 dollar netbook which essentially can run the same software as a 30000 dollar server, albeit slower. In 1964, this similarity was considered revolutionary. Many people within IBM doubted that it could be done at all. But it was done, and at its launch, the fastest System 360 machine was about 25 times faster than the slowest. In 1970, the System 360 models offered by IBM spanned a performance factor of 200.

The key to the System 360 design was the idea of using common instruction set architecture across a range of computers. For those less familiar with how computers work, the instruction set of a computer determines which programs it can run. Programs written to use one instruction set cannot run on a computer using a different instruction set. For example, programs for Apple’s iPhone do not work directly on Apple desktop machines, as they use different instruction sets.

Prior to the System 360, there had been ad-hoc efforts at making new computer systems run the same software as older computer systems. The System 360 made this an explicit promise, and machines were marketed as part of the family with a guarantee that existing software would work on the new machines.

Looking back at this decision from 2010, it can be seen to signify a maturing of the information technology field. Today, the common wisdom in the computer industry is that software is more important than hardware. People and businesses buy computers to run certain software on them, and the hardware is of secondary importance. We make the choice between Windows, Linux, or MacOS when buying a new computer. In the early days of the computer, the hardware was primary and the software was created after the hardware, and it was normal to rewrite all software when a new computer was acquired. As business usage of computers increased, more and more effort was invested in software, and the value of the software began to overtake the value of the computers on which it was run.

The System 360 proved very popular with customers and IBM's sales doubled from 1965 to 1970. In the mid-70s, IBM as a company was as big as the rest of the US computer industry combined. The success of the System 360 drove other firms to create compatible machines, creating for the first time a computer market in which different vendors sold machines that would compete on performance and price, but run the same software.

The System 360 was also copied by the Soviet Union and Eastern Bloc nations. In the 1970s, the Soviet Union decided to clone the System 360 architecture instead of using a homegrown design. The machines were called “ES EVM”, and more than 15000 were manufactured up until 1998. Thus, the IBM System 360 ended running the most important business computer systems on both sides of the iron curtain. When the Cold War ended, this turned out to be a blessing for IBM, as the old East provided a large pool of programmers skilled in the System 360 architecture, while Western computer science students had long moved on to newer technology like PCs and client-server computing.

Over the years, the architecture of the System 360 has been upgraded and developed. The first major upgrade was the System 370 announced in 1970, and in 1990, another redesign gave it the new name System 390. In 2000, the name was changed to “zSeries” following another major redesign to extend the amount of memory the computers could use. The “z” indicates “zero downtime”, the main selling point of mainframe computers today. The most recent generation of the System 360 lineage is the the “z10”. The z10 can essentially still run all the software written since 1964, as well as newer software which can take advantage of the new features of the System 370, System390, and zSeries. To an outsider, it can be quite surprising to realize just how much decades-old software is still in active use in many businesses, for the simple reason that there is no point in fixing what is not broken.

IBM “mainframe” computers, offered referred to as 'big iron' by IT workers, still run many of the most critical computer functions of our modern society, in particular in the financial system. The IBM mainframes have a reputation for outstanding stability and reliability, as well as services and support that -- while costly -- ensure that the computers never go down and that business never stops. IBM’s mainframe computers are not the dominant force in the computer industry that they once were, but they are still a major business, even if it is far out of the public eye. It is quite possible that the descendants of the System 360 will continue to be around for many decades to come. So far, all predictions about the death of the mainframe have proven to be false.