Aviation Incidents and Accidents

Posted by PITHOCRATES - March 12th, 2014

Technology 101

The Pilots of Aloha Airlines Flight 243 landed Safely after Fatigue Cracks caused Part of the Cabin to Disintegrate

The de Havilland Company introduced the jet airliner to the world.  The Comet.  A 4-engine jet airliner with a pressurized cabin that could carry 36 passengers.  It could fly at 40,000 feet at speeds close to 500 mph.  Just blowing the piston-engine competition away.  Until, that is, they started breaking up in flight.  A consequence of pressuring the cabin.  The inflating and deflating of the metal cabin fatiguing the metal of the cabin.  Until fatigue cracks appeared at stress points.  Cracks that extended from the cycles of pressurizing and depressurizing the cabin.  Until the cracks extended so much that the pressure inside the cabin blew through the cracks, disintegrating the plane in flight.

Japan is a nation of islands.  Connecting these islands together are airplanes.  They use jumbo jets like buses and commuter trains.  Packing them with 500+ passengers for short hops between the islands.  Putting far more pressurization cycles on these planes than typical long-haul 747 routes.  On August 12, 1985, Japan Airlines Flight 123 left Haneda Airport, Tokyo, for a routine flight to Osaka.  Shortly after takeoff as the cabin pressurized the rear pressure bulkhead failed (due to an improper repair splice of the pressure plate using a single row of rivets instead of a double row following a tail strike that damaged it).  The rapid force of the depressurization blew out through the tail section of the aircraft.  Causing great damage of the control surfaces.  And severing the lines in all four hydraulic systems.  Leaving the plane uncontrollable.  The crew switched their transponder to the emergency code 7700 and called in to declare an emergency.  But they could do little to save the plane.  The plane flew erratically and lost altitude until it crashed into a mountain.  Killing all but 4 of the 524 aboard.

Hawaii is similar to Japan.  They both have islands they interconnect with airplanes.  Putting a lot of pressurization cycles on these planes.  On April 28, 1988, Aloha Airlines Flight 243 left Hilo Airport bound for Honolulu.  Just as the Boeing 737 leveled off at 24,000 feet there was a loud explosive sound and a loud surge of air.  The pilots were thrown back in their seats in a violent and rapid decompression.  The flightdeck door was sucked away.  Looking behind them they could see the cabin ceiling in first class was no longer there (due to fatigue cracks radiating out from rivets that caused pressurized air to blow out, taking the ceiling and walls of the first class cabin with it).  They could see only blue sky.  They put on their oxygen masks and began an emergency descent.  The first officer switched the transponder to emergency code 7700.  The roar of air was so loud the pilots could barely hear each other as they shouted to each other or used the radio.  The flight controls were operable but not normal.  They even lost one of their two engines.  But the flight crew landed safely.  With the loss of only one life.  A flight attendant that was sucked out of the aircraft during the explosive decompression.

The Fact that 185 People survived the United Airlines 232 Crash is a Testament to the Extraordinary Skill of those Pilots

On June 12, 1972, American Airlines Flight 96 left Detroit Metropolitan Airport for Buffalo after arriving from Los Angeles.  The McDonnell Douglas DC-10 took on new living passengers in Detroit.  As well as one deceased passenger in a coffin.  Which was loaded in the rear cargo hold.  As the DC-10 approached 12,000 feet there was a loud explosive sound.  Then the flightdeck door was sucked away and the pilots were thrown back in their seats in an explosive decompression.  The aft cargo door (improperly latched—its design was later revised to prevent improperly latching in the future) had blown out as the cargo hold pressurized.  As it did the rapid decompression collapsed the floor above.  Into the control cabling.  The rudder was slammed fully left.  All three throttle levels slammed closed.  The elevator control was greatly inhibited.  The plane lost a lot of its flight controls but the pilots were able to bring the plane back to Detroit.  Using asymmetric thrust of the two wing-mounted engines and ailerons to compensate for the deflected rudder.  And both pilots pulling back hard on the yoke to move the elevator.  Due to the damage the approach was fast and low.  When they landed they applied reverse thrust to slow down the fast aircraft.  At that speed, though, the deflected rudder pulled them off the runway towards the terminal buildings.  By reapplying asymmetric thrust the pilot was able to straighten the aircraft out on the grass.  As the speed declined the rudder force decreased and the pilot was able to steer the plane back on the runway.  There was no loss of life.

On July 19, 1989, United Airlines Flight 232 took off from Stapleton International Airport in Denver for Chicago.  About an hour into the flight there was a loud bang from the rear of the plane.  The aircraft shuddered.  The instruments showed that the tail-mounted engine had failed.  As the crew responded to that the second officer saw something more alarming.  Hydraulic pressure and fluid quantity in the three hydraulic systems were falling (a fan disc in the tail-mounted engine disintegrating and exploded like shrapnel from an undetected manufacturing flaw, taking out the 3 hydraulic systems).  The flight crew soon discovered that they had lost all control of the airplane.  The plane was making a slight turn when the engine failed.  And the flight control surfaces were locked in that position.  The captain reduced power on the left engine to stop the plane from turning.  The two remaining engines became the only means of control they had.  Another DC-10 pilot traveling as a passenger came forward and offered his assistance.  He knelt on the floor behind the throttle levels and adjusted them continuously to regain control of the plane.  He tried to dampen the rising and falling of the plane (moving like a ship rolling on the ocean).  As well as turn the aircraft onto a course that would take them to an emergency landing at Sioux City.  They almost made it.  Unfortunately that rolling motion tipped the left wing down just before touchdown.  It struck the ground.  And caused the plane to roll and crash.  Killing 111 of the 296 aboard.  It was a remarkable feat of flying, though.  Which couldn’t be duplicated in the simulator given the same system failures.  As flight control by engine thrust alone cannot provide reliable flight control.  The fact that 185 people survived this crash is a testament to the extraordinary skill of those pilots.

On July 17, 1996, TWA Flight 800 took off from JFK Airport bound for Rome.  About 12 minutes into the flight the crew acknowledged air traffic control (ATC) instructions to climb to 15,000 feet.  It was the last anyone heard from TWA 800.  About 38 seconds later another airplane in the sky reported seeing an explosion and a fire ball falling into the water.  About where TWA 800 was.  ATC then tried to contact TWA 800.  “TWA800, Center…TWA eight zero zero, if you can hear Center, ident…TWA800, Center…TWA800, if you can hear Center, ident…TWA800, Center.”  There was no response.  The plane was there one minute and gone the next.  There was no distress call.  Nothing.  The crash investigation determined that an air-fuel mixture in the center fuel tank was heated by air conditioner units mounted below the tank, creating a high-pressure, explosive vapor in the tank that was ignited by an electrical spark.  The explosion broke the plane apart in flight killing all 230 aboard.

The Greatest Danger in Flying Today may be Pilots Trusting their Computers more than their Piloting Skills

On December 29, 1972, Eastern Airlines Flight 401 left JFK bound for Miami.  Flight 401 was a brand new Lockheed L-1011 TriStar.  One of the new wide-body jets to enter service along with the Boeing 747 and the McDonnell Douglas DC-10.  Not only was it big but it had the latest in automatic flight control systems.  As Flight 401 turned on final approach they lowered their landing gear.  When the three landing gear are down and locked for landing there are three green indicating lights displayed on the flightdeck on the first officer’s side.  On this night there were only 2 green lights.  Indicating that the nose wheel was not down.  So they contacted ATC with their problem and proceeded to circle the airport until they resolved the problem.  ATC told them to climb to 2000 feet.  The 1st officer flew the aircraft on the course around the airport.  The captain then tried to reach the indicating light to see if it was a burnt out lamp.  Then the flight engineer got involved.  As did the first officer after turning on the automatic altitude hold control.  Then another person on the flightdeck joined in.  That indicating lamp got everyone’s full attention.  Unable to determine if the lamp was burnt out the pilot instructed the flight engineer to climb down into the avionics bay below the flightdeck to visually confirm the nose gear was down and locked.  He reported that he couldn’t see it.  So the other guy on the flightdeck joined him.  During all of this someone bumped the yoke with enough pressure to release the automatic altitude hold but no one noticed.  The airplane began a gradual descent.  When they approached the ground a ground proximity warming went off and they checked their altitude.  Their altimeters didn’t agree with the autopilot setting.  Just as they were asking each other what was going on the aircraft crashed into the everglades.  Killing 101 of the 176 on board.

On June 1, 2009, Air France Flight 447 was en route from Rio de Janeiro to Paris.  This was a fly-by-wire Airbus A330 aircraft.  With side stick controllers (i.e., joysticks) instead of the traditional wheel and yoke controls.  The A330 had sophisticated automatic flight controls.  They practically flew the plane by themselves.  With pilots spending more of their time monitoring and inputting inputs to these systems than flying.  Flight 447 flew into some turbulence.  The autopilot disengaged.  The aircraft began to roll from the turbulence.  The pilot tried to null these out but over compensated.  At the same time he pitched the nose up abruptly, slowing the airplane and causing a stall warning as the excessive angle of attack slowed the plane from 274 knots to 52 knots.  The pilot got the rolling under control but due to the excessive angle of attack the plane was gaining a lot of altitude.  The pitot tube (a speed sensing device) began to ice up, reducing the size of the opening the air entered.  Changing the airflow into the tube.  Resulting in a speed indication that they were flying faster than they actually were.  The engines were running at 100% power but the nose was pitched up so much that the plane was losing speed and altitude.  There was no accurate air speed indication.  For pilot or autopilot.  The crew failed to follow appropriate procedures for problems with airspeed indication.  And did not understand how to recognize the approach of a stall.  Despite the high speed indicated the plane was actually stalling.   Which it did.  And fell from 38,000 feet in 3 and a half minutes.  Crashing into the ocean.  Killing all 228 on board.

It takes a lot to bring an airplane down from the sky.  And when it happens it is usually the last in a chain of events.  Where each individual event in the chain could not have brought the plane down.  But when taken together they can.  Most times pilots have a chance to save the aircraft.  Especially the stick and rudder pilots.  Who gained a lot of flying experience before the advanced autopilot systems of today.  And can feel what the airplane is doing through the touch of their hand on the yoke and through the seat of their pants.  They are tuned in to the engine noise and the environment around them.  Processing continuous sensations and sounds as well as studying their instruments and the airspace in front of them.  Because they flew the airplane.  Not the computers.  Allowing them to take immediate action instead of trying to figure out what was happening with the computers.  Losing precious time when additional seconds could trigger that last event in a chain of events that ends in the loss of the aircraft.  That’s why some of the best pilots come from this stick and rudder generation.  Such as Aloha Airlines Flight 243, American Airlines Flight 96 and United Airlines Flight 232.  Sometimes the event is so sudden or so catastrophic that there is nothing a pilot can do to save the aircraft.  Such as Japan Airlines Flight 123 and TWA Flight 800.  And sometimes pilots rely so much on automated systems that they let themselves get distracted from the business of flying.  Even the best stick and rudder pilots adjusting to new technology.  Such as Eastern Airlines Flight 401.  Or pilots brought up on the new technology.  Such as Air France Flight 447.  But these events are so rare that when a plane does fall out of the sky it is big news.  Because it rarely happens.  Planes have never been safer.  Which may now be the greatest danger in flying.  A false sense of security.  Which may allow a chain of events to end in a plane falling down from the sky.  As pilots rely more and more on computers to fly our airplanes they may step in too late to fix a problem.  Or not at all.  Trusting those computers more than their piloting skills.



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FT99: “We don’t need government to protect consumers because dead consumers can’t buy anything.” -Old Pithy

Posted by PITHOCRATES - January 6th, 2012

Fundamental Truth

Corporations Care for our Personal Well-Being because they Care about Profits

A lot of people feel that if it weren’t for government big corporations would kill consumers with faulty, defective and dangerous goods.   That the only thing that prevents these evil corporations from killing us wholesale to maximize their profits is a caring government.  Because the only things corporations care about are profits.  Which is true.  But because they do they also care for our personal well-being.  For to make profits you have to sell.  And if you kill the people that buy from you you’re not going to sell much.

Case in point, the big 1982 Tylenol scare in Chicago.  Seven people died from five tampered bottles of Tylenol.  They found three additional bottles still on store shelves.  Johnson & Johnson, the maker of Tylenol, moved swiftly.  Not to hide anything.  But to protect their customers.  They initiated a nationwide recall, pulling some 31 million bottles of Tylenol out of the market.  They placed national advertisements warning people not to consume any acetaminophen (the chemical compound that is Tylenol).  Fully cooperated with local and federal authorities.  And introduced tamper-resistant packaging.  The 1982 Tylenol scare cost Johnson and Johnson 77% of their market share.  But because of their prompt actions to protect their customers as well as the general public, they regained their market share.  And the people’s trust.

During the Seventies the DC-10 had a series of high-profile accidents.  A cargo door design caused a near crash over Windsor, Ontario.  And a crash in France.  Ground crews thought they closed the door properly.  They didn’t.  The doors blew out and damaged the hydraulic control systems when the sudden decompression collapsed the floor into those control lines.  A DC-10 taking off from Chicago O’Hare lost a wing-mounted engine, damaging the leading edge slats and hydraulic controls.  Mechanics had changed that engine without following proper maintenance procedures.  As a result they overstressed the pylon mounting flange which failed during their take-off roll.  The DC-10 got a reputation for being unsafe.  When McDonnell Douglas resolved these issues a lot of people were still wary about getting on a DC-10.  Which didn’t help orders from airlines.  They ceased production with the last delivery in 1989 after delivering only some 446 aircrafts.  Some of which are still flying today.

If Businesses Endanger their Customers their Customers will Take Notice and Stop being Customers

McDonnell Douglas designed the DC-10 to compete against the Boeing 747, the first wide-body jet.  It couldn’t carry as many people but it could take off from shorter runways.  And with one less engine it burned less fuel.  It was a successful economic model.  And competed well against the 747.  But the 747 had/has a better safety record.  And reputation.  They’re still building them today.  With over 1400 having been delivered through 2011.  A number the DC-10 may have approached if it wasn’t for that reputation earned in the Seventies.

If businesses endanger their customers their customers will take notice.  And stop being customers.  That’s why Johnson and Johnson acted quickly.  And recovered.  McDonnell Douglas did not.  With declining sales Boeing eventually bought them out.  And retired the MD-11 (the latest version the DC-10).

Paying Consumers provide Great Incentive for Business to try and Predict Every Possible Failure

Johnson and Johnson led the way during the Tylenol scare.  The FDA caught up to them.  The FAA forced design modifications to improve the safety of the DC-10.  After approving the original design that they subsequently deemed unsafe.  Aircraft are complex machines.  No one can predict every possible failure.  In business.  Or government.  But the paying consumers provide great incentive for business to try.  Because dead consumers can’t buy anything.



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LESSONS LEARNED #56: “It’s competition in the private sector that makes life better. Not government regulation.” -Old Pithy

Posted by PITHOCRATES - March 10th, 2011

Deregulation makes Air Travel Cheaper and Safer

A lot of people bitched about the deregulation of the airlines.  Mostly union people.  Because before they were deregulated it was very expensive to fly.  Ticket prices were out of the reach of most of middle class America.  But, with those high prices, the airlines made a lot of money.  And the unions got a lot of that money.  Union members warned about safety with deregulation.  If they lowered ticket prices so anyone could fly there wouldn’t be enough money to maintain the highly skilled personnel to fly and maintain the airplanes.  If you put profits before safety planes could start falling out of the sky.

Well, they deregulated the airlines in 1974.  Government no longer controlled the price of tickets, air traffic routes or the number of airlines allowed to operate.  Ticket prices fell.  More airlines began operations.  More cities built airports.  More people were flying than ever before.  All people.  Not just the rich.  Deregulation was a huge success.  Except for unions.  For them it wasn’t quite the gravy train it was before deregulation.  So did safety suffer?  No.  Quite the contrary.

In 1959 there were 40 fatal accidents per million departures (at the beginning of the jet age).  That number fell to about 10 in 1960.  During the Sixties it was at or below 5.  The number fell by approximately half during the Seventies.  It fell to about 1 after the Seventies with a spike of about 1.5 in 1988.

At the beginning of the jet age, few in the government bureaucracy knew anything about jets.  So it was mostly the manufacturers and the airlines policing themselves as they developed jetliner travel.  And they did a pretty good job.  After deregulation air travel exploded with the new jets.  They were safe enough that people weren’t afraid to fly on them.  And they did.

Boeing and Douglas lead the way in the Jet Age

Competition drove early jet travel.  Air travel was growing and the airlines needed planes that could carry more people, fly farther and faster.  If they had the planes they could fly the people.  Two of America’s manufacturers stood up in a big way.  Boeing built the 707.  And Douglas built the DC-8.  This competition produced two jetliners that were safe to fly and they moved more people farther than any propeller plane.  There were some accidents in the beginning but they were less compared to the propeller planes they replaced. 

Air travel continued to grow.  There was a demand for bigger airplanes.  A bigger plane could move more people at a lower cost per person.  This meant even lower ticket prices.  And made air travel more affordable to the less rich.  Boeing rolled out the 747.  McDonnell Douglas (the merger of Douglas with McDonnell Aircraft Corporation) rolled out the DC-10.  The first of the wide-bodies.  The Boeing 747 went on to become a huge success with an incredible safety record.  It still flies today.  Few airplanes make people feel safer.  The DC-10, on the other hand, did not make people feel as safe.  For a period of time.  And that marked the beginning of the end of McDonnell Douglas.

McDonnell Douglas was a very successful company.  They built thousands of DC-9s and MD-80/90s.  Over 2,000.  These are very reliable and safe aircrafts.  The DC-9 had only 0.76 fatal accidents per million departures (PMD).  The MD-80/90s had only 0.31 fatal accidents PMD.  You’ll still see a lot of these flying today.  It has proven to be a very reliable airframe.  The DC-10, though, had a bumpier road with less than 500 built.  It, too, was a good airplane.  But it was involved with some very high-profile accidents.  And it got a reputation as an unsafe design.

A Close Call with the Cargo Hold Door of a DC-10

The cargo hold door on the DC-10 opened outward.  This allowed room for more cargo.  Doors that open in take up cargo space.  Which reduces revenue.  The more cargo you can carry, the more revenue you make and the lower ticket prices can be.  It’s just one in many ways to reduce the cost of air travel.  And it was yet another thing that made the DC-10 profitable to fly.

Airlines bought the DC-10 and put it into service.  It performed well.  But that cargo door would become an issue.  Doors on an airplane typically open inward.  For a good reason.  Once a plane reaches an altitude of 10,000 feet, it has to be pressurized so people can breathe normally.  That places a lot of pressure inside the passenger and cargo compartments.  The only ‘holes’ in the aircraft have doors that seal tighter at these higher interior pressures.  Because they open inward.  The cargo door on the DC-10, though, needed a special latching mechanism to withstand those pressures without opening in flight.  Because it opened outward.

Closed properly there was no problem.  But sometimes it wasn’t.  In 1972, a DC-10 departing from Detroit suffered an explosive decompression as it climbed above 10,000 feet.  The cargo door failed.  The sudden decompression collapsed the passenger floor and damaged the aircraft’s control cables and hydraulics.  The rudder was deflected full left.  The engines throttle levels slammed back to idle.  The tail-mounted engine control cables were severed completely.  The elevator provided little control.  The pilots varied the thrust on the wing-mounted engines to maneuver the aircraft back to the airport.  They compensated for the deflected rudder with asymmetric thrust on the wing engines.  Without a functioning elevator the nose dropped at lower speeds.  So they landed at a higher speed than normal.  As they slowed the force of the rudder declined and the asymmetric thrust took over, pulling the aircraft off the runway.  It was a tremendous piece of flying by the crew that brought that plane back without loss of life.

A Pair of Crashes Threaten the DC-10 and McDonnell Douglas

The rear cargo door was studied and some changes were made.  Issues with floor strength in the new wide-bodies were questioned.  They just started flying.  This was new territory for everyone.   No significant change was made.  Other DC-10s were flying safely.  This may have just been an isolated incident of human error (closing the cargo door incorrectly).  Then, in 1974, it happened again.  In a series of human errors that doomed a Turkish Airlines plane leaving Paris for London.  A different seat configuration put more people over the floor that collapsed on the Detroit flight.  The explosive decompression tore through the cabin floor, causing greater damage to the control cables and hydraulics than on the Detroit flight.  There was nothing the flight crew could do.  The plane was uncontrollable.  It crashed, killing all 346 aboard.  The largest loss of life to date.  And the first crash of a new wide body.

The subsequent investigation painted the DC-10 as unsafe.  Then in 1979 another catastrophic accident at Chicago’s O’Hare airport.  During takeoff.  After passing V1 (the speed the aircraft could no longer abort and stop safely on the runway) the left wing-mounted engine and pylon tore away from the wing.  The pilots had no idea what had happened other that an engine had lost all thrust.  They couldn’t see the wing from the flight deck.  So they followed procedures for a two-engine takeoff.  But the damage to the leading edge of the left wing was severe.  The leading edge slats retracted with the severing of the hydraulic lines.  The left wing now had a slower stall speed than the right wing.  But they didn’t know.  And they had no indication in the cockpit.  The plane was flying.  They climbed out per procedure.  They powered back from take-off power.  And when they did, the left wing started to dip.  In the few seconds they had to understand what was happening it was too late.  The wing stalled.  The plane rolled left and pitched down.  And crashed.  Killing all 271 aboard.

Was this a design flaw?  No.  Again, it was human error.  The maintenance crew did not follow published maintenance procedures.  The left engine and pylon was replaced after routine maintenance.  The maintenance manual called for the engine removal first.  Then the engine pylon.  Some airlines were replacing the engine and pylon as an assembly.  This saved maintenance hours (and cut costs).  And was safer because it reduced the number of fuel, hydraulic and electrical wiring that had to be disconnected and reconnected.  Or so they thought.  Lifting the engine and pylon assembly to the underside of the wing attachment point was a delicate procedure, though.  That’s a lot of mass pressed against the mounting flange.  And in this case, they pushed the assembly up too high into the flange, deforming it and causing a fracture.  No one knew this as they accelerated down that O’Hare runway.  As they approached take off speed the flange broke completely, sending that engine up and over the wing.

Plane Crashes don’t help Sell Planes or Tickets

With these high-profile accidents the DC-10 got a reputation for being unsafe.  Orders fell.  While orders for the Boeing 747 remained strong.  Even though they had similar safety records.  The early 747s had 1.41 fatal accidents per PMD (the later 747-400 had 0.19 fatal accidents per PMD).  The DC-10 had 1.36 fatal accidents per PMD.  It was as safe if not safer as the 747s that were flying during the same time.  But the public relations damage was done.  Boeing sales grew.  McDonnell Douglas sales fell.  The business founded by Donald Douglas in 1921 is no more.  Unable to compete with Boeing (or Airbus) any longer, McDonnell Douglas merged with Boeing.

McDonnell Douglas had a very successful run.  But the Boeing 747 went on to dominate the wide-body market.  And one wide-body paid a lot more bills than a bunch of narrow-bodies.  Commercial planes have only gotten bigger.  The Airbus 380 is a double decker that can carry over 800 passengers.  And is giving the Boeing 747 a run for its money.  Who knows what might have happened if not for these high-profile accidents.  McDonnell Douglas had even floated the idea of a double decker airplane.  By that time, though, it was too late.

Competition between Boeing and Douglas introduced the jet age.  Their continued competition gave us wide-body jetliners.  Average people could fly anywhere in the world.  And air travel got safer through the years.  Government regulation didn’t make this happen.  Yes, the government made some planes safer.  But not until after a crash.  And they were few and far between.  The vast majority of commercial aviation flew safely.  Because manufacturers and airlines have a vested interest in being safe.  For a very good reason.  Plane crashes don’t help you sell planes.  Or tickets.  But they can put you out of business.  Even if they aren’t your fault.  Something McDonnell Douglas knows only too well.



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