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On 3 March 1991, a Boeing 737 operating as United Airlines Flight 585 suddenly rolls into a dive and crashes within eight seconds, killing all 25 people on board. On 8 September 1994, USAir Flight 427 also rolls and crashes within thirty seconds, killing all 132 people on board. On 9 June 1996, Eastwind Airlines Flight 517 also rolls unexpectedly in similar circumstances, but the crew successfully regains control of the aircraft and lands safely. The cause of all three incidents was a design flaw with the rudder's control system which allowed the rudder to suddenly and unexpectedly go to full deflection and jam due to thermal shock of the hydraulic control valve.
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00:02The Boeing 737 is one of the most popular passenger jets in the world.
00:10Around the globe, the plane has carried more than 12 billion passengers.
00:15It's the backbone of the aviation industry.
00:23But in 1991, something happened on board a 737 that sent shutters through the world of aviation.
00:33A deadly crash has investigators scrambling.
00:41There was a time when I had doubts that we'd be able to solve it.
00:44It was like he was tracking a serial killer.
00:50The hunt for answers will take 10 long and gruelling years.
00:54The fate of the airline industry hangs in the balance.
00:58And the mystery isn't solved until more than 150 people are dead.
01:319.40am, March 3rd, 1991.
01:40After a short 17-minute trip from Denver, United Airlines Flight 585 is on final approach into Colorado Springs.
01:51It looks like a perfect day for flying.
01:54But there's trouble in the air.
02:01Nice looking day.
02:02Hard to believe the skies are unfriendly.
02:06There's been heavy turbulence during the flight.
02:09And violent gusts of wind are forecast over Colorado Springs.
02:16Never driven to Colorado Springs and not gotten sick.
02:23At the controls is 52-year-old Captain Harold Green.
02:27A pilot with 20 years experience and a sterling reputation.
02:31Green's co-pilot is Patricia Ideson.
02:34At 42, she's one of the first female flight officers in United's history.
02:41Flight attendants, prepare for landing.
02:53At Colorado Springs Municipal Airport, air traffic controller James Rayfield is ready to bring flight 585 in.
03:02United 585, report the airport in sight.
03:07Got it?
03:08Yep.
03:10Airport in sight, United 585.
03:12Lower landing gear.
03:14United 585 is cleared for a visual approach to runway 35.
03:19Weather conditions, wind 320 degrees at 16, gusting at 29.
03:26As its speed decreases, flight 585 becomes more vulnerable to the turbulence.
03:32Ideson wants to know what other planes have experienced on landing.
03:36Any reports lately of any loss or gain of airspeed?
03:39Yes, ma'am.
03:41500 feet at 50 knot loss.
03:44At 400 feet at 50 knot gain.
03:47And at 150 feet at gain of 20 knots.
03:51Sounds adventurous, thank you.
03:54Starting on down.
04:01Less than three kilometers from the airport, retired policeman Harold Darnell is on his way to a local flea market.
04:10A kilometer overhead, Green and Ideson focus on keeping their speed constant as they descend.
04:17Wait, a 10 knot change here.
04:20Yeah, I know.
04:21Awful lot of power to hold that airspeed.
04:25As United 585 approaches the runway, Darnell feels something strange.
04:31Whoa, what the heck was that?
04:32Out of nowhere, a powerful gust of wind strikes his vehicle, almost blowing him off the road.
04:40Another 10 knot gain?
04:42Three flaps.
04:47From the control tower, James Rayfield can now see flight 585's final approach.
04:56As the aircraft closes in on the airport, the ride gets even bumpier.
05:02Well, we're at a thousand feet.
05:11Then, without warning, the 737 starts to spin out of control.
05:15Oh God, seven.
05:16Ahhhh!
05:18Ahhhh!
05:20Ahhhh!
05:21Ahhhh!
05:2115 clups.
05:2215!
05:24Oh no.
05:25Oh my god!
05:26Ahhhh!
05:29Oh my god!
05:31Come on!
05:35Oh my god!
05:37Ahhhh!
05:38Oh my god!
05:39Ahhhh!
05:39Yeahhh!
05:42Oh my lord!
05:46Crash! Crash!
05:59Rescue workers arrive within minutes, but there's almost no sign of the 737.
06:06The shattered remains of the 38-ton jet lie buried in a fire-blackened impact crater.
06:14The plane didn't skate or bounce, you know, like when a plane comes in normally and lands.
06:19It just nosed right in, and where it hits, where it stays.
06:23And I came down here, and this is when I saw all of that. It was horrible.
06:29There are no survivors.
06:31All 20 passengers and five crew members are killed instantly by the high-speed impact and exploding jet fuel.
06:42In 10 violent seconds, Colorado Springs has become the site of one of the most mysterious air crashes in aviation
06:50history.
07:15By nightfall, investigators from the National Transportation Safety Board
07:20descend on Colorado Springs.
07:26Known to insiders as tin kickers,
07:29NTSB investigators examine over 2,000 aviation accidents a year,
07:33at times by picking through the metal debris of fallen aircraft.
07:41While coroners mark the location of human remains in red,
07:46NTSB investigators mark scraps of metal in yellow,
07:50looking for clues to help them solve the mystery of Flight 585.
08:00Like investigating a mass murder, it's a tough job walking onto a crash site.
08:07Among the investigators assigned to the case is Malcolm Brenner,
08:11a specialist in human performance.
08:13His job will be to find out if the crash was caused by pilot error.
08:18The area was cordoned off by police and there were Salvation Army trucks.
08:23I got a cup of coffee, a cup of hot chocolate or something,
08:27and I thanked them for it and I said,
08:29no, no, thank you.
08:30And they had this look in their eyes like,
08:31my God, you have to go into this site.
08:35Clues to the fate of United 585 lie mangled in a deep black hole.
08:42The fuselage is crushed like an accordion in the impact crater.
08:46The rest of the plane is in pieces spread over an area smaller than a football field.
08:55There was a lot of fire damage, there had been a fire afterwards,
08:58and it was all contained in a relatively small area,
09:01which just initial impression, it can be a sign that the airplane was intact.
09:06If there was a mid-air explosion or something came off the airplane,
09:09you'd expect that to be a much larger site.
09:12My first sense that it was going to take some time to investigate the accident
09:16was the damage that we saw in the parts.
09:19When they're burnt and broken, the process always takes longer.
09:26But with their work just beginning,
09:28members of the NTSB have no clue that the case of United 585
09:33will become the longest crash investigation in aviation history.
09:44A clear late winter day in 1991 turned deadly in just 10 short seconds.
09:51Moments from landing in Colorado Springs,
09:54United Airlines Flight 585 fell out of the sky at 370 km per hour.
10:00Crash! Crash!
10:04All 20 passengers and five crew members died.
10:12The National Transportation Safety Board begins a painstaking investigation into the crash.
10:20Engine turbines, hydraulic pressure gauges, the cockpit voice recorder,
10:25and in-flight data recorder are all carefully extracted from the site,
10:29photographed and sent to the lab for analysis.
10:38An important first step in the investigation is the analysis of the cockpit voice recorder.
10:44With pilot error a factor in 70% of air disasters,
10:48Malcolm Brenner's job is to see what role pilots Green and Eidson played in the crash.
10:54This crew was, and I felt this at the time, was one of the more impressive crews I'd ever dealt
11:00with.
11:01There was a little bit of tension release, a little bit of humor.
11:04The captain said,
11:05Never driven to Colorado Springs and not gotten sick.
11:10The first officer suggested that they add extra speed as a safety margin.
11:15The captain agreed with it. It was good interaction.
11:17Got it?
11:19Yep.
11:20Airport in sight, United 585.
11:23Lower landing gear.
11:24This is a sense of an excellent crew caught randomly, if anything.
11:31So again, that was my first impression, is that this would be consistent more with a hardware situation.
11:40As more about Flight 585 becomes known,
11:44mechanical failure becomes a serious suspect.
11:49Just seconds before it crashed, the plane rolled onto its back and spun wildly out of control.
11:57Investigators wonder if the sudden motion was caused by the plane losing an engine,
12:01or a wing.
12:05From the state of the aircraft on site, it's clear that it was intact at the time of the crash.
12:11What investigators don't know, is if the engines were still working at impact.
12:23Technicians examined the engine turbines.
12:26They discovered dirt has been drawn deeply into every crevice.
12:30These blades were clearly spinning and sucking in air at the time of impact.
12:37The engines may have been running, but technicians aren't sure how well.
12:42The plane's hydraulic pressure dials are destroyed, their glass covers broken.
12:47The indicator needles have been snapped off by the force of the impact.
12:51But even these ravaged dials tell a tale.
12:5515 flaps!
12:5615!
13:01On close inspection, investigators find a critical mark.
13:05At the moment of impact, a dent was made on the faceplate by the jarred indicator needle.
13:11It proves that when United 585 crashed, its engines were running normally.
13:27With engine failure ruled out, there seems to be only one other mechanical explanation
13:32for why 585 suddenly rolled over and then fell out of the sky.
13:39It appears increasingly likely that the plane had suffered a catastrophic problem with its flight controls.
13:46Investigators quickly become suspicious of the rudder at the back of the tail.
13:50We focused in after eliminating other flight control surfaces that we thought could contribute to the role.
13:57We started looking at the rudder.
14:00Bring that up so I can take a look at it.
14:03Investigators begin their examination of the rudder on site.
14:06But the violence of the crash makes the job extremely difficult.
14:10Almost nothing left.
14:14Most of the plane's parts are too crushed or burned for testing.
14:18But a vital component is still reasonably intact.
14:22The power control unit, or PCU.
14:27Used constantly during flight, especially during landings, the PCU performs like a car's power steering.
14:35When the pilot pushes on a rudder pedal, the PCU uses hydraulic fluid to convert gentle movements of a pilot's
14:42foot into the pressure needed to move the 737's enormous rudder.
14:49The heart of the PCU is something called the dual servo valve.
14:55Shaped like a soda can, it has two slides which glide past one another, directing the flow of pressurized hydraulic
15:02fluid that moves the rudder.
15:06The servo valve is very unique, that it is in effect two valves in one, and that that creates a
15:16whole range of interactions that don't occur in a more conventional hydraulic valve.
15:25When a technician opens the power control unit, chips of metal are found floating in the hydraulic fluid.
15:33It's a disturbing find.
15:35These particles could cause the servo valve to jam, making it impossible to work the plane's rudder.
15:44It's a chilling prospect.
15:46Could a microscopic fault bring down a 38-ton jet?
15:51It's difficult for Philips to tell.
15:53While more intact than much of the wreck, the PCU and dual servo valve are both damaged.
15:59The airplane crashed and burnt in a pretty confined area, and there was a lot of damage to the flight
16:05control components and the things we were testing and needed to test and look at.
16:09The more damaged the components are, the harder it is to take measurements and do functional testing.
16:19To test what he does have, Philips travels to California, to the labs of Parker Hannafin, where the rudder control
16:27unit is made.
16:34The curious metal chips floating in the PCU's chambers are dismissed.
16:40Philips is told that filters keep them out of the delicate servo valve that directs fluid and moves the rudder.
16:49Nothing else is found that could explain any sudden movement of the rudder on Flight 585.
16:57We didn't have any absolute indication or information that we could point to that said the rudder power control unit,
17:04the servo valve or any part of that flight control system caused that accident.
17:10Philips still suspects a mechanical problem, but with no conclusive evidence that the PCU or servo valve caused the crash,
17:18he's forced to sign off on the tests.
17:21It's a pass.
17:27With Philips at a dead end, only bad mountain weather remains as a primary suspect.
17:35An expert on weather-related aviation accidents, Greg Salatolo is trying to determine if heavy winds on the day of
17:43the crash were a factor.
17:44There is a history of events where there have been airplane accidents attributed to mountain waves of rotors.
17:51In 1966, a BOAC 707 near Mount Fuji disintegrated in a mountain wave and rotor.
18:01High winds crashing over mountain peaks leave so-called wind rotors in the lee side.
18:07Invisible, highly turbulent downdrafts that come plunging down with devastating power and are extremely dangerous to aircraft.
18:15We found a great deal of evidence looking at the surface upper air data and talking to witnesses in the
18:24area that rotors were a possibility.
18:25An explosion, it was right over there.
18:28Salatolo hears several eyewitness reports of bizarre mountain weather on the day of the crash.
18:33One of the most intriguing is from Harold Darnell.
18:37Whoa, what the heck was that?
18:40Whose truck was struck by a powerful gust of wind just moments before 585 crashed.
18:47But as Greg Salatolo combs through his evidence, the theory that a wind rotor knocked the plane from the sky
18:53is getting less and less likely.
19:02Nice looking day. Hard to believe the skies are unfriendly.
19:05Wind rotors are areas of extremely low barometric pressure.
19:10So if flight 585 did pass through one, its altimeter reading would have spiked as the plane was blown suddenly
19:18upwards.
19:23There was no evidence that we saw that on the flight data recorder of 585.
19:29What the flight recorder did show was a fast and deadly drop in altitude as the plane fell to Earth.
19:51It's been 21 months since the investigation into the crash of United Flight 585 began.
19:58Almost two years in which the NTSB has studied the crew, the weather, the rudder and thousands of other pieces
20:06of evidence.
20:08They've come up empty handed.
20:11For only the fourth time in its history, the NTSB releases a report which doesn't reach a conclusion.
20:18The cause of the crash of flight 585 is undetermined.
20:23We had put a lot of time and effort into the investigation and we just weren't sure what had happened.
20:29It was like he was tracking a serial killer.
20:32He was frustrated that they had not solved 585.
20:36He did not want that to happen again.
20:42But almost two years after the report on 585 is released, the killer strikes again.
20:51At 7pm on a clear windless day, US Air Flight 427 is nearing Pittsburgh.
20:59Captain Peter Germano and First Officer Chuck Emmett are getting ready for their final approach.
21:06Folks from the flight deck.
21:08We should be on the ground in about 10 more minutes.
21:11Sunny skies, a little hazy.
21:13Flight attendants, please prepare for landing.
21:15I ask you to check the security of your seatbelt. Thank you.
21:18US Air 309, descend and maintain 6,000.
21:23As they close in on the airport, the pilots are on the lookout for another flight about 10km ahead of
21:29them.
21:31Looking for the traffic.
21:35Turning 1-0-0.
21:39US Air 427.
21:44I see the jet stream.
21:48As they pass through the turbulence left behind by the other flight, their jet suddenly and alarmingly rolls left.
21:56Hold on, hold on.
21:59Hold on.
22:01Shoot!
22:02Nothing the pilots do seems to have any effect.
22:12What the hell is this?
22:16What the...
22:17Oh!
22:18Shoot!
22:23Oh God.
22:24Oh God.
22:26427! Emergency!
22:33Oh shoot.
22:35Oh!
22:36Oh God!
22:38Oh God, no!
22:40Oh!
22:44Oh!
22:45Oh!
22:57Rescue crews arrive quickly, but the fate of Flight 427 is tragically clear.
23:03There's no hope for the 132 passengers and crew.
23:08The human carnage is so bad, authorities declare the crash site a biohazard.
23:14The U.S. Air 427 accident was the first U.S. accident where biohazard suits were used.
23:20And it made it more difficult. They were uncomfortable, they were hot.
23:24And to this day, when I put on a pair of rubber gloves, for any reason, I'm instantly transformed back
23:30to the site in Pittsburgh.
23:33Captain John Cox, a 737 pilot and a flight system specialist with the Airline Pilots Association, is asked to join
23:41the team investigating the crash of Flight 427.
23:46As coroners attempt to collect human remains, NTSB lead investigator Tom Houter already knows his hunt for clues will be
23:56long and painstaking.
23:59When we first arrived at the crash site, well, first of all, there was no aircraft there.
24:04There were only bits and pieces of the airplane. It wasn't really recognizable as an airplane.
24:09With the help of eyewitnesses, information from the flight data recorder and the cockpit voice recorder,
24:17investigators begin to quickly see some striking similarities between 427 and the unsolved case of United 585.
24:27In fact, they seem to be mirror images of each other.
24:32On final approach, United 585 rolls right, while U.S. Air 427 rolls to the left.
24:41Both crews are caught by surprise, and after just a few terrifying seconds, both aircraft plummet straight into the ground.
24:50Certainly the whole team was aware of the previous accident with United 585 in Colorado Springs.
24:55We try to keep that in the back of our minds and take a look at this one as to
24:58what it presents to us.
25:01As the investigation continues, the list of similarities grows.
25:07427's engines were also attached and functioning at the time of impact.
25:12But for all the similarities, there's one important difference.
25:17Unlike United 585, as U.S. Air 427 approached Pittsburgh, weather conditions were dead calm.
25:27The folks from the flight deck, we should be on the ground about 10 more minutes.
25:32Sunny sky's a little hazy.
25:33Taking a look at the flight data recorder information, the aircraft's approaching Pittsburgh.
25:38It's an extremely smooth night.
25:40There's just no turbulence at all.
25:43The pilots are relaxed.
25:45They're talking about the landing.
25:46Flight attendants, please prepare for landing.
25:48I ask you to check the security of your seatbelts.
25:52As he did in the case of United 585, Greg Phillips will once again lead the investigation into the mechanical
25:59aspects of the crash.
26:02Almost immediately, he makes a promising discovery.
26:07Miraculously, much of U.S. Air 427's tail and rudder appear intact.
26:18The hydraulic devices inside the tail have also sustained very little damage.
26:25Phillips and Houta prepare to send the parts to the manufacturer, Parker Hannafin, for testing as soon as possible.
26:32They need answers.
26:34Pressure on the NTSB to solve the accident is growing quickly.
26:41Not only are the crashes of flights 585 and 427 disturbingly similar,
26:46both of them involve the same kind of airplane, a Boeing 737.
26:54But with serious questions being raised about the plane's safety,
26:58billions of dollars, and perhaps the airline industry itself, are at risk.
27:04We couldn't live with the fact, as investigators, of having two unsolved 737 accidents.
27:10The airplane is in too much use, too wide of use around the world.
27:13It carries too many people every day.
27:16Unsolved was not an acceptable answer.
27:19If 427 was an undetermined accident, we could not find the cause of this accident,
27:24there was a great chance that if there was a third accident with the 737 fleet under similar circumstances,
27:32that the 737 fleet would have been grounded.
27:38Careful with it.
27:41The investigation into the crash of Flight 427 may be the most important in the history of the NTSB.
27:49But it won't be easy.
27:51Answers are still years away.
27:56In just three years, two Boeing 737s have crashed in the United States with no survivors.
28:05In both cases, the planes were moments from landing.
28:09And in both cases, the planes were under full power,
28:12but the pilots were unable to control their jets.
28:21In the crash of United Flight 585,
28:24NTSB investigators were unable to find a cause.
28:28Now they're searching for clues into the second crash,
28:32U.S. Air Flight 427.
28:34As the investigator in charge, I never allowed myself to think this investigation could go undetermined.
28:40We kept on pushing and kept on researching.
28:42As long as we had things to research, we kept on going.
28:46To find their killer, the NTSB can't afford to rule anything out.
28:51From the possibility that a collision with birds brought 427 down,
28:55to strange, even bizarre theories.
28:58They looked at electromagnetic interference.
29:01They got calls from people saying it might be Russian death rays.
29:04They considered everything.
29:06There were a couple of witnesses who gave reports of the aircraft suddenly descendant and hovering before it blew up.
29:12We discounted those.
29:14But the investigation's primary suspect is the dual-servo valve,
29:19part of the power control unit that moves the 737's rudder,
29:23and a suspect in the crash of United 585.
29:28Parker Hannafin made the valve.
29:30At its lab in California,
29:32investigators look inside the main cavity of the U.S. Air Power Control Unit.
29:38Just like in the earlier crash,
29:40they find tiny chips of metal floating in the hydraulic fluid.
29:45But once again, Parker and Boeing repeat their claim.
29:50Filters designed to stop any debris from interfering with the delicate metal slides have done their job.
29:59Investigator Greg Phillips wants to be absolutely sure.
30:02If the chips were blocking the slides,
30:05they would have left tiny scratch marks behind where they rubbed against the metal.
30:11But Phillips can't find any.
30:14Another pass.
30:16Okay.
30:19Phillips has technicians put the servo valve from flight 427
30:23through as many tests as he can think of,
30:26trying to find a weakness.
30:28If he can find one,
30:30it could explain why two planes were ripped from the sky.
30:35But he comes up empty.
30:38That unit passed all its operational tests.
30:41There wasn't any indication that it had failed,
30:43and it operated within the parameters we expected it to.
30:50Once again,
30:51the investigators are forced to shift their focus back to the pilots.
30:59By studying the plane's flight data recorder,
31:02investigators know that the jet's rudder was deployed fully to one side,
31:06what's called rudder hardover.
31:10We were definitely focused on rudder,
31:14on hardover rudder,
31:16full rudder input for about 20 seconds.
31:20It can be caused either by hardware,
31:22something unknown in the hardware,
31:24or it can be caused by pilot input.
31:28First officer Chuck Emmett,
31:30who was flying 427,
31:32did indeed step down hard on his rudder,
31:35and then held it there while the plane plummeted towards the earth.
31:39It raised a grisly question.
31:41Was he trying to fly the plane into the ground?
31:45And looking at this,
31:47and being a pilot myself,
31:49it's like,
31:50this doesn't seem like rational behavior.
31:53What the hell is this?
31:56Human performance specialist Malcolm Brenner
31:59listens closely for evidence on the cockpit voice recorder.
32:02What the fuck?
32:04Shoot!
32:05In this case,
32:06they had microphones right by their mouths,
32:08and you can hear,
32:09as well as in real life or better,
32:10you can hear breathing sounds.
32:13Yeah.
32:14I see the jet stream.
32:16The cockpit recordings indicate
32:18that Flight 427's troubles
32:19began at the moment it flew through the jet wake
32:22of a Delta Air Lines 727
32:24that had just passed in front of them.
32:27Both pilots are startled by the wake.
32:30I see the jet stream.
32:32The first officer breaks off at the end of a sentence.
32:34I see the jet stream.
32:37And there's no more discussion
32:38on the jet stream or anything else.
32:39They both focus.
32:39Something happened here.
32:40Captain says,
32:41jeez.
32:43It was such a smooth flight
32:45that it was a momentary jolt
32:48that they just hadn't anticipated.
32:50And with that,
32:51the pilots got on the controls
32:53and immediately, you know,
32:54put in a rudder input.
33:01The cockpit recorder
33:02even records the thumping sound
33:04of the jet stream turbulence
33:05as 427 flies through it.
33:07As Flight 427 encounters the turbulence,
33:11Brenner hears something unusual.
33:14First Officer Emmett begins to grunt.
33:23The grunting is unusual.
33:25The controls are designed
33:27so that pilots don't need to grunt.
33:29They're specially designed around human capabilities.
33:31So to have someone grunting
33:32is typically a sign of an emergency.
33:35By matching data from the flight recorder
33:38with the crew's voices,
33:39Brenner is able to confirm
33:40that Emmett's grunts begin a split second
33:43after he pushed down on the rudder pedal
33:45and three to four seconds
33:46after the wake turbulence
33:47affected Flight 427.
33:55On their own,
33:56the cockpit voice recordings
33:57prove very little.
33:59But it seems clear
34:00that the crew weren't trying
34:01to crash their plane.
34:03Something happened
34:04which took them by surprise.
34:06They reacted as quickly as they could,
34:08but nothing they did seemed to help.
34:10What the hell is this?
34:15It's been almost two years
34:16since the crash of Flight 427
34:18and the investigation has stalled.
34:21Now two 737s have gone down
34:24in startlingly similar ways
34:26and investigators still don't know why.
34:29We were all frustrated
34:30as months wore into years.
34:34What were we missing?
34:36It definitely took a toll
34:37in their personal lives.
34:38They worked incredibly long hours.
34:40They never stopped thinking about it.
34:43We were going up against an aircraft
34:44that had an incredible safety history.
34:47It was really everything you could see.
34:50For 30 years,
34:51this has been a great airplane.
34:53We were trying to prove
34:56that there was something wrong
34:57with a straight-A student.
34:58It clearly was on his mind.
35:01He at one point had a nightmare about it
35:04where he dreamed that he was in front
35:06of a congressional committee
35:08that was grilling him.
35:11Now there had been a third 737 crash
35:14and in Tom's dream,
35:16all of the cameras were pointing to him
35:18and a congressman asked,
35:20why didn't you ground the fleet?
35:29Unsure of where to look next
35:30and with the trail of evidence getting colder,
35:33investigators need a break in the case
35:35and fast.
35:39East Wing 517,
35:41you're clear for landing.
35:46On June the 9th, 1996,
35:49they finally get the break
35:50they've been looking for.
35:53Captain Brian Bishop
35:54is on final approach
35:55to Richmond, Virginia,
35:56when, without warning,
35:58his East Wing jet
35:59rolls sharply to the right.
36:07We didn't know to what extent,
36:09but we knew we had a problem
36:10with the rudder.
36:11I turned the yoke
36:13the opposite direction
36:14and stood on the opposite rudder pedal.
36:16The pedal didn't move for me.
36:19For over 30 seconds,
36:21the 737 flies in a precarious right bank
36:24as Bishop fights
36:26to keep it from rolling over.
36:30Then suddenly,
36:31the unknown forces
36:32holding the jet let go,
36:37snapping the wings back to horizontal.
36:43In a matter of seconds,
36:45it released itself
36:47and went back to normal.
36:49We had started the checklist
36:52almost before I could
36:53finish the sentence.
36:54All of a sudden,
36:55there was just a wham.
37:02For a second time,
37:04the 737 is pushed
37:05onto its side.
37:07For 30 harrowing seconds,
37:09the 737 takes on
37:11a life of its own.
37:14Then, once again,
37:16as quickly as it began,
37:18the rollover stops.
37:22After the second time,
37:23I looked at the first officer
37:24and I said,
37:25declare an emergency.
37:26Tell the controller
37:27we have flight control problems.
37:36As they slow down to land,
37:38the risks increase.
37:44If a third rollover occurs,
37:46they won't have enough
37:47airspeed to recover.
37:48I did at some point
37:50tell my first officer
37:51to look out the window
37:52and find a dark spot.
37:54It was night time
37:55and we were looking
37:56to avoid a neighborhood
37:57or a populated area.
37:59And he very calmly responded
38:01that, hey,
38:02here's a spot over here.
38:11But there is no third rollover.
38:14Bishop brings flight 517
38:16in high and fast
38:17and lands safely.
38:22Taxing in is when I realized
38:24my legs were shaking.
38:26We got the aircraft
38:27to the gate
38:28and I did pick up the PA
38:30to make an announcement
38:31to try to explain
38:32what had just happened
38:33to these people.
38:36Picking up the microphone,
38:37I realized
38:38there was nothing I could say
38:39to make this any better.
38:43And probably for the first time
38:45in a long time,
38:45I was at a loss of words.
38:47So I simply put the microphone down
38:49and let it go with that.
38:53But Bishop won't remain
38:54speechless for long.
38:56By the next day,
38:57the investigation team
38:58has arrived in Richmond.
39:04Flight data recorded
39:05it was undamaged,
39:06an airplane undamaged.
39:07We launched to the scene.
39:09The airplane literally
39:11didn't move.
39:12It stayed at its location
39:13in the airport
39:13until we got down there.
39:15There were a lot of FAA,
39:17a lot of NTSB,
39:17and they all wanted
39:18to talk to us very badly.
39:20It gave the NTSB
39:22a tremendous break
39:23because suddenly they had
39:25a 737 that had had
39:26a rudder incident
39:27that was intact
39:29and they had a pilot
39:30who was alive
39:31and who could talk about it.
39:33I think they were much happier
39:34to have the airplane than me.
39:36I think the airplane
39:38probably gave them more
39:40to research than I ever could.
39:45NTSB investigators
39:46quickly determined
39:47that what happened
39:48on board Eastwind
39:49Flight 517
39:50is alarmingly similar
39:51to events on flights
39:53427 and 585.
39:55If they can discover
39:56why Bishop's 737 rolled over,
39:59they may be able
40:00to crack two mysterious
40:01and fatal accidents.
40:03And when we said,
40:04well, what happened?
40:05They said,
40:05there was something wrong
40:06with the rudder pedal.
40:07The pedal wouldn't go down.
40:09I was standing
40:10on the rudder pedal
40:11and I couldn't get it
40:12to go down.
40:15My God.
40:19With Bishop's
40:20first-person testimony,
40:22investigators immediately
40:23zero in on
40:24Eastwind's rudder controls.
40:29The power control unit
40:31is removed,
40:32inspected,
40:33and then tested
40:33again and again.
40:37To the frustration
40:38of everyone,
40:39the unit performs perfectly.
40:41We tested that aircraft
40:43as is.
40:44It was intact.
40:44We went through
40:45a complete lead.
40:46We did flight tests
40:47with it.
40:49And it passed all tests.
40:52After a five-year
40:54hunt for clues,
40:55a third mysterious
40:56rudder event
40:57on a 737,
40:58and a live pilot
41:00as a witness,
41:01Tom Houter
41:02still lacks the evidence
41:03he needs
41:04to crack his case.
41:06He decides
41:07to push
41:07his chief suspect,
41:09Flight 427's
41:10rudder controls,
41:11a little harder.
41:17One fellow
41:18mentioned a test
41:19they had done
41:20in the military
41:20of a thermal shock,
41:24where if you had
41:25the actuator
41:26being very cold
41:27and put in
41:28very hot
41:28hydraulic fluid,
41:29it would cause it
41:31to react
41:31in strange ways.
41:35So we put together
41:36a thermal shock test,
41:37and this test
41:39was extreme
41:39to say the least.
41:43On August the 26th,
41:451996,
41:46in Valencia,
41:47California,
41:48NTSB investigators
41:50gather to watch
41:51the torture test
41:52of US Air 427's
41:54PCU.
41:56After soaking it
41:58in dry ice,
41:59the PCU
42:00is blasted
42:00with nitrogen gas
42:01to simulate
42:02the minus 40 degree
42:03temperatures
42:04at 10,000 meters.
42:09Then it's quickly
42:10injected with
42:11superheated
42:12hydraulic fluid
42:13and given the command
42:14to start working.
42:17As we were standing
42:19there listening
42:19to the actuator move
42:21left and right,
42:23left and right,
42:26it stopped.
42:28And it was not
42:29commanded to stop.
42:30It just jammed.
42:32It stopped working
42:33completely.
42:34Take a look.
42:40Systems investigator
42:41Greg Phillips
42:42now asks that the valve
42:44be taken apart
42:45and scanned
42:46for scratches.
42:51they find none.
42:53Look at that.
42:55Doesn't leave a trace.
42:57It's a crucial breakthrough
42:59to solving an almost
43:00perfect crime.
43:01Not only have they
43:03proven that the valve
43:04which controls the rudders
43:05can jam,
43:06no evidence
43:07is left behind.
43:11Tom Houter
43:12and his team
43:13have now found
43:14that a small hydraulic valve
43:15that controls the rudder
43:16of the world's
43:17most popular
43:18commercial jetliner
43:19can jam in the
43:20right circumstances.
43:23It's an ominous discovery.
43:26But incredibly,
43:27there's another
43:28shocking surprise
43:29in store
43:30for the investigators.
43:35October the 15th, 1996.
43:37For the last five years,
43:40the National Transportation
43:41Safety Board
43:42has been struggling
43:43to crack its toughest case.
43:46Two completely separate
43:48but seemingly linked accidents.
43:52The crash of United 585
43:54killed 25 passengers and crew.
44:01Three years later,
44:03the U.S. Air Flight 427 disaster
44:05took another 132 lives.
44:14Now, after examining
44:15hundreds of clues,
44:17investigators have made
44:18a surprising discovery.
44:22A new test has revealed
44:24that under the right circumstances,
44:26the hydraulic valve
44:27that moves the 737's rudder
44:29can jam.
44:31It just jammed.
44:33But the surprises
44:35aren't over.
44:36The most important
44:37breakthrough
44:38came when a Boeing engineer
44:41examining the data
44:43from that test
44:45discovered some numbers
44:47that indicated
44:48the valve
44:49at that point
44:50had actually reversed.
44:56It's a stunning revelation.
44:59Not only can the servo valve jam,
45:02but it can then function
45:03in reverse.
45:04It means that
45:05any time a pilot
45:06tries to correct a rollover
45:07by pushing on the rudder,
45:09the rudder might turn
45:10in the opposite direction,
45:12causing a fatal accident.
45:14And the reversal
45:15is like driving your car.
45:17You turn to the right,
45:18it goes left.
45:19You're not going to figure out
45:21this failure mode
45:22until you go off the road.
45:23And in these cases,
45:25that's the pilots
45:25we're faced with,
45:26something so unusual
45:28that they didn't understand
45:30what was happening.
45:31What the hell is this?
45:34They had evidence now
45:36that the valve was unique,
45:38that the valve
45:39not only could jam,
45:41but would reverse.
45:43427, emergency!
45:47That would explain
45:49why the first officer,
45:51Chuck Emmett,
45:52would keep his foot
45:53on the rudder pedal,
45:55because he's thinking,
45:57why isn't the plane going right?
45:59And he's feeling
46:00the plane go to the left.
46:04To the very end,
46:05Chuck Emmett pushes hard,
46:07hoping his rudder
46:08will help him pull out
46:10of his deadly spiral.
46:12Tragically,
46:13he has no way of knowing
46:14that he's steering
46:15the aircraft
46:16straight into the ground.
46:22Never driven
46:22to Colorado Springs
46:24and not gotten sick.
46:30Flight attendants,
46:31prepare for landing.
46:33Satisfied that they've determined
46:35the cause of the crash
46:36of U.S. Air 427,
46:38the NTSB turns its attention
46:40to the unsolved case
46:41of United 585.
46:47Another 10-0 game.
46:48Going back to Colorado Springs,
46:50you could follow a progression
46:51of what the captain was doing.
46:53He's close to the ground,
46:55and suddenly,
46:56under rudder reversal,
46:57he puts in a little bit
46:58of pedal.
46:58The pedal violently
47:00pushes his leg back.
47:01Oh, God!
47:02Flip!
47:0315, flop!
47:0415!
47:07Rudder reversal certainly fits
47:09what I know about this crew
47:10and how it fits.
47:11We were able to show
47:13the failure mode.
47:14It matched the flight
47:15data recorder
47:15from each aircraft.
47:17It felt like a glove.
47:19So we now had
47:20a lot more information
47:22we could apply
47:22to United 585,
47:24and based on that,
47:25we redid the accident report.
47:27Oh, my God!
47:28Oh, no!
47:28From rudder reversal
47:30to impact
47:30took less than 10 seconds.
47:33585's flight crew
47:34had no chance
47:35to save their plane
47:36or passengers.
47:40In the aftermath
47:41of the investigation,
47:42sweeping changes
47:43were made
47:44to improve the safety
47:45of the 737
47:46and the entire
47:47aviation industry.
47:50New training protocols
47:51were designed
47:52to help pilots react
47:53to unusual
47:54in-flight events.
47:56In the 737 fleet,
47:58pilots are now trained
47:59on how to react
48:00to both rudder hardovers
48:01and reversals.
48:04The scenario
48:05of the U.S. Air 427 accident,
48:07if the crew
48:08had the information
48:09that we have today,
48:11I believe they would have
48:12landed safely
48:13in Pittsburgh that evening.
48:17The FAA
48:18also directed Boeing
48:19to redesign
48:20the rudder's
48:21dual-servo valve
48:22to eliminate
48:23the potential
48:24for reversal.
48:26Boeing spent
48:27hundreds of millions
48:27billions of dollars
48:28to replace the valves
48:29on thousands
48:30of 737s
48:31around the world.
48:33One thing we don't like
48:34of the safety board
48:35is to have
48:36an undetermined accident
48:37because then we can't
48:38make a change
48:39to improve safety.
48:41So out of
48:41U.S. Air 427,
48:43United 585,
48:44we have a much safer
48:46737 fleet.
48:54It took NTSB
48:56tin kickers
48:5610 years
48:57to solve
48:58the mysterious crashes
48:59of flights 585
49:00and 427,
49:02the longest investigation
49:04in aviation history.
49:07There are still
49:08some people
49:09in aviation
49:09who don't think
49:10the NTSB
49:11got it right.
49:12But I became convinced
49:13after talking
49:14to many,
49:15many,
49:15many people,
49:16pilots,
49:16engineers,
49:17people at Boeing,
49:19and spending
49:20a lot of time
49:21with the investigators
49:22that they did
49:23get it right.
49:28Since the replacement
49:29of the 737 servo valves,
49:32there hasn't been
49:33a similar crash
49:34of the most popular,
49:35most profitable plane
49:36in the world.
49:45Now,
49:58the building