On the Flightdeck during Aviation Disasters

Posted by PITHOCRATES - March 19th, 2014

Technology 101

USAir Flight 427 on Approach to Pittsburgh flew through Wake Vortex and Lost Control

Malaysian Airlines Flight 370 search is still ongoing.  We’re seemingly no closer to understanding what happened than before.  There has been a lot of speculation.  And rebuttals to that speculation.  With many people saying things like why didn’t the crew radio?  Why didn’t they report a problem?  While others are saying that it is proof for their speculative theory.  That they were either under duress, had no time or were in on it and, therefore, went silent.  So what is it like on the flightdeck when something happens to an aircraft?  Well, because of past CVR (cockpit voice recorder) transcripts from previous accidents, we can get an idea.

On September 8, 1994, USAir Flight 427 flew into the wake vortex (little tornados trailing from a large plane’s wingtip) of a Delta Airlines Boeing 727 ahead of it.  This sideways tornado disrupted the airflow over the control surfaces of the USAir 737.  Disrupting it from level flight, causing it to roll left.  The autopilot tried to correct the roll as the 737 passed through the wake vortex core.  Causing more disruption of the airflow over the control surfaces.  The first officer then tried to stabilize the plane.  Control of the aircraft continued to deteriorate.  We pick up the CVR transcript just before this event (see 8 September 1994 – USAir 427).  CAUTION: The following recounts the final moments of Flight 427 and some may find it disturbing.

CAM-1 = Captain
CAM-2 = First Officer
CAM-3 = Cockpit Area Mike (cabin sounds and flight attendants)
RDO-1 = Radio Communications (Captain)
APP: Pittsburgh Approach

APP: USAir 427, turn left heading one zero zero. Traffic will be one to two o’clock, six miles, northbound Jetstream climbing out of thirty-three for five thousand.
RDO-1: We’re looking for the traffic, turning to one zero zero, USAir 427.
CAM-3: [Sound in engines increasing rpms]
CAM-2: Oh, yeah. I see the Jetstream.
CAM-1: Sheez…
CAM-2: zuh?
CAM-3: [Sound of thump; sound like ‘clickety-click’; again the thumping sound, but quieter than before]
CAM-1: Whoa … hang on.
CAM-3: [Sound of increasing rpms in engines; sound of clickety-click; sound of trim wheel turning at autopilot trim speed; sound similar to pilot grunting; sound of wailing horn similar to autopilot disconnect warning]
CAM-1: Hang on.
CAM-2: Oh, Shit.
CAM-1: Hang on. What the hell is this?
CAM-3: [Sound of stick shaker; sound of altitude alert]
CAM-3: Traffic. Traffic.
CAM-1: What the…
CAM-2: Oh…
CAM-1: Oh God, Oh God…
RDO-1: 427, emergency!
CAM-2: [Sound of scream]
CAM-1: Pull…
CAM-2: Oh…
CAM-1: Pull… pull…
CAM-2: God…
CAM-1: [Sound of screaming]

At 19:03:01 in the flight there was a full left rudder deflection.  The plane yawed (twisted like a weathervane) to the left.  A second later it rolled 30 degrees left.  This caused the aircraft to pitch down.  Where it continued to roll.  The plane rolled upside down and pitched further nose-down.  The pilots never recovered.  The plane flew nearly straight into the ground at 261kts.  The crash investigated focused on the rudder.  Boeing redesigned it.  Pilots since have received more training on rudder inputs.  And flight data recorders now record additional rudder data.  This incident shows how fast a plane can go from normal flight to a crash.  The captain had time to radio one warning.  But within seconds from the beginning of the event the plane crashed.  Illustrating how little time pilots have to identify problems and correct them.

An In-Flight Deployment of a Thrust Reverser breaks up Lauda Air Flight 004

A plane wants to fly.  It is inherently stable.  As long as enough air flows over its wings.  Jet engines provide thrust that push an airplane’s wings through the air.  The curved surfaces of the wings interacting with the air passing over it creates lift.  As long as a plane’s jet engines push the wing through the air a plane will fly.  On May 26, 1991, something happened to Lauda Air Flight 004 to disrupt the smooth flow of air over the Boeing 767’s wings.  Something that isn’t supposed to happen during flight.  But only when a plane lands.  Reverse thrust.  As a plane lands the pilot reverses the thrust on the jet engines to slow the airplane.  Unfortunately for Flight 004, one of its jet engines deployed its thrust reverser while the plane was at about 31,000 feet.  We pick up the CVR transcript just as they receive a warning indication that the reverse thruster could deploy (see 26 May 1991 – Lauda 004).  CAUTION: The following recounts the final moments of Flight 004 and some may find it disturbing.

23.21:21 – [Warning light indicated]

23.21:21 FO: Shit.

23.21:24 CA: That keeps, that’s come on.

23.22:28 FO: So we passed transition altitude one-zero-one-three

23.22:30 CA: OK.

23.23:57 CA: What’s it say in there about that, just ah…

23.24:00 FO: (reading from quick reference handbook) Additional system failures may cause in-flight deployment. Expect normal reverse operation after landing.

23.24:11 CA: OK.

23.24:12 CA: Just, ah, let’s see.

23.24:36 CA: OK.

23.25:19 FO: Shall I ask the ground staff?

23.25:22 CA: What’s that?

23.25:23 FO: Shall I ask the technical men?

23.25:26 CA: Ah, you can tell ’em it, just it’s, it’s, it’s, just ah, no, ah, it’s probably ah wa… ah moisture or something ’cause it’s not just, oh, it’s coming on and off.

23.25:39 FO: Yeah.

23.25:40 CA: But, ah, you know it’s a … it doesn’t really, it’s just an advisory thing, I don’t ah …

23.25:55 CA: Could be some moisture in there or somethin’.

23.26:03 FO: Think you need a little bit of rudder trim to the left.

23.26:06 CA: What’s that?

23.26:08 FO: You need a little bit of rudder trim to the left.

23.26:10 CA: OK.

23.26:12 CA: OK.

23.26:50 FO: (starts adding up figures in German)

23.30:09 FO: (stops adding figures)

23.30:37 FO: Ah, reverser’s deployed.

23.30:39 – [sound of snap]

23.30:41 CA: Jesus Christ!

23.30:44 – [sound of four caution tones]

23.30:47 – [sound of siren warning starts]

23.30:48 – [sound of siren warning stops]

23.30:52 – [sound of siren warning starts and continues until the recording ends]

23.30:53 CA: Here, wait a minute!

23.30:58 CA: Damn it!

23.31:05 – [sound of bang]

[End of Recording]

The 767 Emergency/Malfunction Checklist stated that upon receiving the warning indicator ADDITIONAL system faults MAY cause an in-flight deployment of the thrust reverser.  But that one warning indication was NOT expected to cause any problem with the thrust reversers in stopping the plane after landing.  At that point it was not an emergency.  So they radioed no emergency.  About 10 minutes later the thrust reverser on the left engine deployed in flight.  When it did the left engine pulled the left wing back as the right engine pushed the right wing forward.  Disrupting the airflow over the left wing.  Causing it to stall.  And the twisting force around the yaw axis created such great stresses on the airframe that the aircraft broke up in the air.  The event happened so fast from thrust reverser deployment to the crash (less than 30 seconds) the crew had no time to radio an emergency before crashing.

Fire in the Cargo Hold brought down ValuJet Flight 592

One of the most dangerous things in aviation is fire.  Fire can fill the plane with smoke.  It can incapacitate the crew.  It can burn through electric wiring.  It can burn through control cables.  And it can burn through structural components.  A plane flying at altitude must land immediately on the detection of fire/smoke.  Because they can’t pull over and get out of the plane.  They have to get the plane on the ground.  And the longer it takes to do that the more damage the fire can do.  On May 11, 1996, ValuJet Flight 592 took off from Miami International Airport.  Shortly into the flight they detected smoke inside the McDonnell Douglas DC-9.  We pick up the CVR transcript just before they detected fire aboard (see 11 May 1996 – ValuJet 591).  CAUTION: The following recounts the final moments of Flight 592 and some may find it disturbing.

CAM — Cockpit area microphone voice or sound source
RDO — Radio transmissions from Critter 592
ALL — Sound source heard on all channels
INT — Transmissions over aircraft interphone system
Tower — Radio transmission from Miami tower or approach
UNK — Radio transmission received from unidentified source
PA — Transmission made over aircraft public address system
-1 — Voice identified as Pilot-in-Command (PIC)
-2 — Voice identified as Co-Pilot
-3 — Voice identified as senior female flight attendant
-? — Voice unidentified
* — Unintelligible word
@ — Non pertinent word
# — Expletive
% — Break in continuity
( ) — Questionable insertion
[ ] — Editorial insertion
… — Pause

14:09:36 PA-2 flight attendants, departure check please.

14:09:44 CAM-1 we’re *** turbulence

14:09:02 CAM [sound of click]

14:10:03 CAM [sound of chirp heard on cockpit area microphone channel with simultaneous beep on public address/interphone channel]

14:10:07 CAM-1 what was that?

14:10:08 CAM-2 I don’t know.

14:10:12 CAM-1 *** (’bout to lose a bus?)

14:10:15 CAM-1 we got some electrical problem.

14:10:17 CAM-2 yeah.

14:10:18 CAM-2 that battery charger’s kickin’ in. ooh, we gotta.

14:10:20 CAM-1 we’re losing everything.

14:10:21 Tower Critter five-nine-two, contact Miami center on one-thirty-two-forty-five, so long.

14:10:22 CAM-1 we need, we need to go back to Miami.

14:10:23 CAM [sounds of shouting from passenger cabin]

14:10:25 CAM-? fire, fire, fire, fire [from female voices in cabin]

14:10:27 CAM-? we’re on fire, we’re on fire. [from male voice]

14:10:28 CAM [sound of tone similar to landing gear warning horn for three seconds]

14:10:29 Tower Critter five-ninety-two contact Miami center, one-thirty-two-forty-five.

14:10:30 CAM-1 ** to Miami.

14:10:32 RDO-2 Uh, five-ninety-two needs immediate return to Miami.

14:10:35 Tower Critter five-ninety-two, uh, roger, turn left heading two-seven-zero.  Descend and maintain seven-thousand.

14:10:36 CAM [sounds of shouting from passenger cabin subsides]

14:10:39 RDO-2 Two-seven-zero, seven-thousand, five-ninety-two.

14:10:41 Tower What kind of problem are you havin’?

14:10:42 CAM [sound of horn]

14:10:44 CAM-1 fire

14:10:46 RDO-2 Uh, smoke in the cockp … smoke in the cabin.

14:10:47 Tower Roger.

14:10:49 CAM-1 what altitude?

14:10:49 CAM-2 seven thousand.

14:10:52 CAM [sound similar to cockpit door moving]

14:10:57 CAM [sound of six chimes similar to cabin service interphone]

14:10:58 CAM-3 OK, we need oxygen, we can’t get oxygen back here.

14:11:00 INT [sound similar to microphone being keyed only on Interphone channel]

14:11:02 CAM-3 *ba*, is there a way we could test them? [sound of clearing her voice]

14:11:07 Tower Critter five-ninety-two, when able to turn left heading two-five-zero.  Descend and maintain five-thousand.

14:11:08 CAM [sound of chimes similar to cabin service interphone]

14:11:10 CAM [sounds of shouting from passenger cabin]

14:11:11 RDO-2 Two-five-zero seven-thousand.

14:11:12 CAM-3 completely on fire.

14:11:14 CAM [sounds of shouting from passenger cabin subsides]

14:11:19 CAM-2 outta nine.

14:11:19 CAM [sound of intermittant horn]

14:11:21 CAM [sound similar to loud rushing air]

14:11:38 CAM-2 Critter five-ninety-two, we need the, uh, closest airport available …

14:11:42 Tower Critter five-ninety-two, they’re going to be standing by for you. You can plan runway one two to dolpin now.

14:11:45 one minute and twelve second interruption in CVR recording]

14:11:46 RDO-? Need radar vectors.

14:11:49 Tower critter five ninety two turn left heading one four zero 14:11:52

RDO-? one four zero

14:12:57 CAM [sound of tone similar to power interruption to CVR]

14:12:57 CAM [sound similar to loud rushing air]

14:12:57 ALL [sound of repeating tones similar to CVR self test signal start and continue]

14:12:58 Tower critter five ninety two contact miami approach on corrections no you you just keep my frequency

14:13:11 CAM [interruption of unknown duration in CVR recording]

14:13:15 CAM [sounds of repeating tones similar to recorder self-test signal starts and continues, rushing air.]

14:13:18 Tower critter five ninety two you can uh turn left heading one zero zero and join the runway one two localizer at miami

14:13:25: End of CVR recording.

14:13:27 Tower critter five ninety two descend and maintain three thousand

14:13:43 Tower critter five ninety two opa locka airports aout ah twelve o’clock at fifteen miles

[End of Recording]

The cargo hold of this DC-9 was airtight.  This was its fire protection.  Because any fire would quickly consume any oxygen in the hold and burn itself out.  But also loaded in Flight 592’s hold were some oxygen generators.  The things that produce oxygen for passengers to breathe through masks that fall down during a loss of pressurization.  These produce oxygen through a chemical reaction that produces an enormous amount of heat.  These were hazardous equipment that were forbidden to be transported on the DC-9.  Some confusion in labeling led some to believe they were ’empty’ canisters when they were actually ‘expired’.  The crash investigation concluded that one of these were jostled on the ground and activated.  It produced an oxygen rich environment in the cargo hold.  And enough heat to start a smoldering fire.  Which soon turned into a raging inferno that burned through the cabin floor.  And through the flightdeck floor.  Either burning through all flight controls.  Or incapacitating the crew.  Sending the plane into a nose dive into the everglades in less than 4 minutes from the first sign of trouble.



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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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