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  • 5/26/2025

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00:00A plane crash in Georgia leaves 23 dead, including a NASA astronaut and a U.S. senator.
00:21Anytime there's a high-profile case, there's more stress and pressure on you.
00:26In search of the cause, investigator Tom Howter gambles on a risky hunch.
00:33When I first proposed doing the flight test, it was not well-received.
00:38He puts his reputation and the life of a skilled test pilot on the line.
00:43EMB-120, do you copy?
00:46Copy.
00:47This was, in my opinion, a very dangerous maneuver.
00:49What if this airplane crashes?
00:52What if we lose the airplane?
00:55The risks, of course, is part of the game.
01:24Atlantic Southeast Airlines Flight 2311 cruises at 15,000 feet.
01:30It's the brave's year.
01:34I feel it.
01:35Sorry, I don't want to get my hopes up.
01:38Last year.
01:39Still hurts.
01:41At the controls is Captain Mark Friedlein.
01:45The 34-year-old is an experienced pilot with almost 12,000 flight hours.
01:51We've got storm clouds ahead of us.
01:53Yep.
01:54What do you want to do?
01:56First officer Hank Johnston is 36.
01:59He's been flying with Atlantic Southeast Airlines for nearly three years.
02:04We're going to go around them.
02:07Tell center we'll go right.
02:10Center ASA 2311, we'd like to request a deviation for some weather.
02:16This was a normal day in the life of the crew.
02:19Nothing untoward had happened, and I doubt they were expecting any difficulties with
02:22the flight.
02:23ASA 2311, roger that.
02:24Weather deviation approved at your discretion.
02:25Maintain current altitude.
02:26OK, thanks.
02:27Center 2311.
02:28Let's go 20 degrees to the right.
02:40Today's flight is a short commuter route from Atlanta, Georgia to the city of Brunswick
02:45on the Atlantic coast.
02:50This is Captain Friedlein on the flat deck.
02:52We've got a bit of weather ahead of us, but we're going to go around it and give you a
02:55pretty smooth ride.
02:56Might hit a few bumps, but nothing to worry about.
02:59We do ask you to return to your seats, and please make sure your safety belts aren't
03:02fastened.
03:09The Embraer 120 banks gently as the pilots deviate around the storm.
03:16The Embraer EMB 120 is designed for commuter-type operations.
03:20It takes approximately 30 people on short-haul flights between city centers.
03:26The commuter airplane is powered by two turboprop engines.
03:31Turboprops differ from jet engines because instead of using the exhaust to power the
03:36aircraft, they use a propeller, which is more fuel-efficient and is more suited for
03:40these smaller aircraft.
03:44Today there are 20 passengers aboard, including NASA astronaut Sonny Carter.
03:51Thank you so much.
03:52You're a star.
03:54As part of the Space Shuttle Discoveries crew, Sonny Carter orbited the Earth for 120 hours,
04:01circling the planet 79 times.
04:06Frederick Gregory served with Carter on that mission.
04:10Sonny was not only an astronaut, he was a renaissance man.
04:13He was an engineer, he was a medical doctor, he was a Navy pilot.
04:18At a very young age, he had accomplished things that even one of which would have been an
04:24outstanding achievement for just any other person.
04:30Also on the flight is another high-profile figure, former Senator John Tower.
04:37Tower served four terms in the U.S. Senate.
04:40A leading Republican, he was an advisor to Presidents Ronald Reagan and George H.W. Bush.
04:47We're still running 20 minutes late.
04:51Yep.
04:52Well, couldn't be helped.
04:56Before takeoff, Flight 2311 was delayed due to a mechanical problem.
05:02The crew was forced to switch planes.
05:05There was a last-minute change in the aircraft, which, while uncommon, is not extraordinary,
05:12and it would not have thrown the crew.
05:14These small planes do keep you on your toes.
05:23The new plane is running smoothly as it leaves the storm clouds behind and nears its destination.
05:33Glynco Airport is a former airbase with just one runway.
05:38It's used by private planes and small commuter airlines flying to the Georgia coast.
05:45The flight attendant prepares the cabin for landing.
05:50Runway's in sight.
05:53The crew is just five minutes from touching down.
05:57ASA 2311, cleared direct to Jeff 1.
06:01Glynco, report the airport in sight.
06:03Expect a visual.
06:05We do have it in sight, 2311.
06:08Slowing for approach speed.
06:11The aircraft was normal.
06:13There was nothing unexpected.
06:15Gear down.
06:19Gear down.
06:22Three green.
06:26Then the captain notices an unusual sound.
06:31It's weird. Number one seems to be spinning faster.
06:36The left is pulling a bit more.
06:40Bringing power down to the left.
06:43Captain Friedlein tries to compensate for the plane's unexplained pull to the left.
06:50Flight 2311 is less than a thousand feet from the ground.
06:55And the plane is getting more and more difficult to control.
07:02What's going on?
07:04See anything?
07:06There's nothing.
07:07The crew were apparently caught completely by surprise by something.
07:11What's going on with this thing? I can't hold it.
07:13Get out of it!
07:15Come on!
07:18The plane is rolling to the left, and the crew doesn't know why.
07:24The crew would have instinctively applied opposite aileron, moving the stick to the right,
07:29to try and prevent the aircraft from rolling as it was.
07:35Come on, guys. Get us out of this.
07:39Come on!
07:41I can't.
07:43I think they would have been preoccupied with trying to stop the roll,
07:48maybe to the extent of not knowing just how much peril they were in.
07:54Do what I do. Grab your ankles, head down. Okay?
07:59Captain Friedlein fights desperately to save his plane.
08:04Come on! No! No!
08:07That's it. Oh, God.
08:09It's no use.
08:15The aircraft crashed in the middle of woods,
08:18which would have made the job of the first responders and firefighting teams quite difficult.
08:25Rescuers make their way through the dense brush.
08:29But when they reach the crash site, they find no one alive to rescue.
08:35All 20 passengers and three crew members are dead, killed at the moment of impact.
08:43It was a catastrophic crash. There was no chance for survival.
08:49With two high-profile passengers on board,
08:52the crash of Flight 2311 makes headlines around the world.
08:59In this particular accident, Senator Tao on board,
09:02who was a four-term senator, was killed,
09:05which raised the profile of the accident a great deal,
09:08both from the investigation point of view and the public and the media.
09:12And we are at this moment beginning the on-scene phases of the investigation.
09:18I was in Spain when the accident occurred.
09:23When I got on the plane to head back,
09:26the pilot told me that one of the astronauts had been killed
09:30and that his name was Carter.
09:33I was in shock because Sonny and I had had an amazing relationship for years.
09:40We were like brothers.
09:47Wreckage is still smoldering when Jim Ritter arrives at the crash site.
09:53Though an experienced investigator with the National Transportation Safety Board,
09:58Ritter is struck by what he sees.
10:01My God!
10:04There was a lot of fire damage in the wreckage
10:07and the airplane was basically totally destroyed.
10:12Ritter realizes he's facing one of the biggest challenges of his career.
10:17Any time there's a high-profile case, you're a little more nervous.
10:22There's more stress and pressure on you to come up with a cause for the accident.
10:28The pressure is on to figure out what happened aboard Flight 2311.
10:41In Glynn County, Georgia,
10:43investigators search for answers at the crash site of Flight 2311.
10:48Several people at a nearby trailer park saw the plane go down.
10:53It had come right over the top of the house and it got real loud.
10:57It was coming right over these trees here and then it got extra loud.
11:04The eyewitnesses saw an extreme left roll angle from the airplane
11:09and so we knew that it was some kind of catastrophic failure,
11:13a very abrupt failure that would have been difficult for the flight crew to overcome.
11:19Okay, let's start here and work backwards to first impact.
11:23I want a record of everything.
11:26You need to look at the crash site to collect the physical evidence.
11:29That's the most important aspect of any aircraft investigation.
11:36The investigators look at the wreckage to try and evaluate the sequence of events leading to the crash.
11:41They look for the two wingtips, the tip of the tail, the tip of the nose.
11:46A survey of the crash site soon confirms those key pieces are among the wreckage.
11:53That tells us that there was no in-flight breakup
11:56and that the airplane stayed intact until it collided with the ground.
12:02Get a shot of this wing for me, please.
12:05For expert investigators, the size and shape of the impact zone is also a clue.
12:13If an aircraft, particularly through trees, has a long swath cut through the trees,
12:18the investigators get an idea that the aircraft hit the ground approximately flat in a shallow descent.
12:24In this case, the wreckage was very concentrated,
12:26which indicated the aircraft hit the ground at a very steep angle.
12:31We need to get some measurements on these trees.
12:35Investigators hope the broken trees will shed light on witness statements about the way the plane was flying.
12:42I seen it fly overhead and it looked like it was making a wide right turn,
12:46but it was unusual because when it turned out, the nose started heading towards the ground
12:51and I was right up toward the entrance of the touchstone
12:54and I heard the explosion and seen the fire and the smoke.
12:58When the plane crashed, it sheared the tops off of many of the trees in the woods there
13:04and so one of the things that we did was we measured the heights of the trees where the tops were sheared off
13:10and that was able to give us a fairly good idea of the roll angle, which was a large left roll.
13:20In the plane, you would have felt light in your seat.
13:22In the plane, you would have felt light in your seat.
13:24You would have turned, obviously, to the left at almost 90 degrees.
13:31It would have been a traumatic experience.
13:43What could make it roll so far over?
13:46When the airplane rolled to the left, it could really only be due to two things.
13:51Perhaps the pilot wanted to roll to the left or there was a malfunction that the pilots couldn't counteract.
13:58What have you got for me?
14:00Ritter examines airport flight records.
14:03He's looking for anything that might have triggered the deadly roll.
14:08Clear skies on approach. Almost zero traffic.
14:12There were no other airplanes in the area to avoid.
14:16It was a nice clear day, so we didn't really have an explanation for why the airplane rolled so violently to the left.
14:25Ritter won't be getting an explanation from any onboard flight recorders.
14:29At the time of the crash, commuter planes aren't required to carry them.
14:34Investigators will have to solve the mystery of Flight 2311 without one of their most useful tools.
14:41Not having those made the physical evidence all the more important.
14:47What have you got for me?
14:50This is the third one.
14:52The engines have been badly damaged in the crash.
14:55The propeller blades have been torn off.
14:59Did Flight 2311 suffer some kind of engine failure?
15:03It's too soon to say.
15:07One thing Ritter does know is that the pressure he's feeling from the media is not about to let up.
15:14The deaths of Senator Tower and astronaut Sonny Carter are sure to keep the investigation in the spotlight.
15:22Ritter is determined not to let the pressure get to him.
15:27Sometimes we feel pressure to do an investigation quickly, but for the most part it's more important to get it right.
15:34And so I would rather take the time and have a good analysis of the evidence before they come out with a probable cause.
15:42We won't find our answers here.
15:46Let's get what we can back to the hangar.
15:48Wings, tail, engines, instruments.
15:52The question now, can he find enough evidence to ever solve the mystery of Flight 2311?
16:00Investigators begin the painstaking task of sorting through the wreckage of Flight 2311.
16:07They're searching for any evidence that might hint at why the Embraer 120 rolled sharply to the left and crashed, killing everyone on board.
16:18All right guys, let's start with the ailerons.
16:21They wonder if one of the plane's flight control systems is malfunctioning.
16:25Control surfaces are the movable flaps, typically at the back of the wings, the tail and the fin,
16:30which allow the pilot to roll the aircraft, to pitch the aircraft and to yaw the aircraft.
16:35The three motions an aircraft can do.
16:39They need to examine every component of the flight control system.
16:44What you're looking for is continuity of the controls.
16:47Are the hinges all intact?
16:49All the actuators are in their proper position?
16:52Were the control surfaces themselves in a reasonable position at the time of impact?
17:00Ailerons look good.
17:02When we examined the control surfaces, we didn't find anything unusual at all.
17:06Everything checked out normally.
17:09Ailerons look good.
17:11When we examined the control surfaces, we didn't find anything unusual at all.
17:15Everything checked out normally.
17:20So if the control systems were all working, why would a plane do this?
17:26Left bank, almost 90 degrees, then almost straight down.
17:32Maybe the engine?
17:34Without the black boxes, it's basically a process of elimination.
17:38We analyze all of the physical evidence and come up with the most compelling scenario that matches that evidence.
17:46All right, let's see what we can find in here.
17:50If one of the plane's two turboprop engines failed,
17:53it might explain why the plane went into such a steep turn.
17:57We wanted to look for any indications of an engine problem,
18:01so we retrieved both the left and the right engine and their propeller systems
18:06and took those back to the laboratory for further examination.
18:11Investigators soon find some tell-tale evidence.
18:15Leaves and branches inside the engines.
18:19When we find vegetation in the ground,
18:22Leaves and branches inside the engines.
18:26When we find vegetation in the engines, that tells us that the engine is operating
18:30because it's sucking in air and it's pulling in the leaves and the vegetation
18:35and that's an indication that it's making power.
18:38This one was spinning to the very end, no doubt about it.
18:42We confirmed that both engines were operating right up until the moment of impact.
18:49That's it!
18:52No!
18:59With engine failure ruled out,
19:01Ritter turns his attention to the other main part of the plane's propulsion system.
19:07Let's take a look at these propellers.
19:11Tom Howter is an NTSB investigator.
19:14When we started doing testing of the propeller system,
19:17we didn't know where it was going to lead us,
19:18but it was something we had to eliminate, if nothing else.
19:23Deep inside the propeller unit, investigators uncover an important clue.
19:29Aha!
19:31There you are.
19:33We have a witness mark. Take a look.
19:36There's a small mark where two parts of the propeller mechanism slammed together on impact.
19:43The witness mark might be enough to tell investigators how the propellers were operating.
19:49You can literally match up the scratch marks between both pieces
19:54and you'll know what the angle of the propeller blade was from that measurement.
20:00Mark this one.
20:0322 degrees.
20:07The Embraer 120 has what's called a constant speed propeller.
20:13The blades spin at a steady rate in flight.
20:17When the pilots need more power, the blades twist,
20:21changing their angle to take a bigger bite out of the air and provide more thrust.
20:28Slow in for approach speed.
20:31And in flight, it acts like the automatic transmission in a car.
20:36It's as if it's changing gears to match the engine load, the speed,
20:40whether the plane is climbing or descending,
20:42and it does so constantly and automatically without intervention by the crew.
20:49There are witness marks inside both propellers.
20:54Now, this one looks like three degrees.
21:01The marks tell Ritter the exact angle of the blades when the plane slammed into the ground.
21:07We immediately noticed a difference between some of the blade angle measurements
21:12for the left engine versus the right engine.
21:16These guys had a big problem with their left propeller.
21:23The blades were almost flat.
21:27The left side propeller blades are at a dangerously low angle,
21:31one that is never used during flight.
21:33At three degrees, the blades are so flat, they would act like a wall,
21:37blocking the flow of air the plane needs to maintain lift.
21:42At certain speeds and certain regimes of flight, if the propeller goes flat enough,
21:46you can have a situation where you can't control the airplane.
21:54Investigators study the mechanism used to control the left propeller.
21:58Look at this.
22:01They make a disturbing discovery.
22:04It's completely worn down.
22:06The teeth on a key piece of the gear mechanism, known as the quill,
22:10are almost entirely worn away.
22:14Investigators may finally have the lead they've been looking for.
22:17This is what it's supposed to look like.
22:19With its teeth worn away, the quill can't lock onto the gear system
22:23that controls the angle of the propeller blades.
22:27The discovery might explain why the propeller blades slipped
22:31to such a dangerously low angle.
22:36Once we noticed that the quill teeth were severely worn,
22:40we started theorizing what was going on.
22:43Once we noticed that the quill teeth were severely worn,
22:47we started theorizing what would happen in that type of situation.
22:52And it was pretty clear that control of the propeller blade angles could be lost.
22:58That really was a eureka moment for us because now we had
23:02a serious malfunction that we could examine.
23:07This could definitely be it.
23:10Ritter digs into manufacturing reports,
23:12trying to find out how such a vital part could have failed.
23:17But what he finds only adds to the mystery.
23:21The quill teeth are made of an extremely durable, case-hardened metal.
23:26They were definitely made to last.
23:28It's hard to imagine what could have caused such rugged teeth to wear down so badly.
23:34Something didn't work as planned.
23:36Let's find out everything we can about every one of these pieces.
23:40Ritter is certain he's found the critical clue.
23:43Worn down teeth on the quill that could have allowed
23:46the propeller blades to slip to a dangerous angle.
23:50But he soon learns there's a big problem with his theory.
23:55The manufacturer says it's impossible.
23:59Engineers at Hamilton Standard included a fail-safe feature
24:03when they designed the propeller.
24:05It should be impossible for the blades to go flat during flight.
24:11Manufacturers have to demonstrate,
24:13through a number of means, that their systems are fail-safe.
24:18All the tests and research that had been done before this said
24:21even if you have a disconnect, that will not result in an accident.
24:28If there's ever a problem with the mechanism controlling the angle,
24:31the blades are designed to move on their own to what's called the feathered position.
24:38The feathered propeller blade, the leading edge of the blade,
24:41is directly into the wind.
24:43So that's the most minimal drag, no thrust, but very little drag.
24:48A feathered propeller can't endanger the safety of the flight.
24:53If this rod disengaged because of any cause,
24:55the propeller should go to feather,
24:57which would result in the loss of the engine,
24:59and the crew would be able to cope with that
25:01and land on one engine as they are trained to do.
25:04Runways inside.
25:09This has got to be it.
25:12This has to be connected somehow.
25:15But Ritter isn't convinced by the manufacturer's assurances.
25:19His gut tells him the worn quill did allow the propeller blades
25:23to move to a dangerous angle.
25:25But without flight data, his investigation has hit a wall.
25:29He has no way to prove the quill brought down Flight 2311.
25:34What's going on?
25:36You see anything?
25:38There's nothing.
25:46Tom, welcome to the team.
25:48No problem, Jim. Glad to help.
25:51With the investigation stalled,
25:53Tom Howter joins Jim Ritter to hunt for answers
25:56in the crash of Atlantic Southeast Flight 2311.
26:01I was a little nervous about this one in that
26:03when I first jumped into it,
26:05I didn't really know what was going on,
26:07other than it was basically at a standstill
26:10and they were looking for me to get it moving.
26:13What do we have?
26:14I think everything we need to know is right here on this table.
26:18You have a part of the propeller control assembly
26:21and the teeth on the gear are essentially gone.
26:25That's very unusual.
26:27Could that have been a part of the accident?
26:29We didn't know.
26:32Howter and Ritter study the design of the propeller mechanism.
26:37Tom, look at this.
26:39We don't see anything obviously wrong with the crew,
26:42we don't see anything wrong with the structure of the aircraft,
26:45we don't see anything wrong with the engines
26:47and the flight control system,
26:49but we do have a severely worn transfer tube and quill arrangement.
26:54Is it possible that this could have resulted in the loss of control?
27:00They discover that shortly before the accident,
27:03Hamilton Standards started using a harder,
27:06more abrasive coating on a key part known as the transfer tube.
27:11Its grooves mesh, like clockwork, into the teeth of the quill.
27:15The change had an unexpected consequence.
27:18It turned into a giant file.
27:21So the splines on the transfer tube
27:23were much harder and rougher than the quill teeth
27:26and it was almost like sandpaper,
27:28so the tube was actually wearing down the teeth on the quill.
27:33The discovery explains the worn teeth on the quill.
27:37But it still doesn't explain the crash.
27:40The design of the propeller shouldn't have changed.
27:43The design of the propeller should ensure it snaps to a safe position,
27:47even with the worn part.
27:51The propeller manufacturer believed that they had a fail-safe condition
27:56so that even if they had this problem,
27:58the propeller blades would be slowly driven to the feather position.
28:05In spite of what all their data says,
28:07the investigators want to see for themselves.
28:14They set up a test at the manufacturer's facility.
28:20We had an engine and a propeller combination
28:23mounted in a test cell.
28:28In order to determine that something is fail-safe,
28:31the engineers use a combination of mathematical analysis,
28:34very structured analysis,
28:36testing in a laboratory, as you can imagine,
28:38and by these methods,
28:40Hamilton Standard convinced themselves that this propeller
28:43would fail in a safe direction, i.e. towards feather.
28:52Jim Ritter's doubts about the fail-safe design
28:55may be confirmed in just a few seconds.
29:00The technician flips a switch
29:02to free the transfer tube from the teeth on the quill.
29:07But as the test unfolds,
29:09instead of moving to flat,
29:11the propeller blades move to the safe feathered position.
29:15The fail-safe system performs exactly as it was designed to.
29:22It suddenly seems that investigators are on the wrong path altogether.
29:29So when we tested the quill with the worn teeth
29:32at the manufacturer's facility,
29:34we found that the propeller blades went to feather.
29:37So at that point, we were basically stumped.
29:42Can you play it again?
29:47The test results leave Ritter and Howter wondering,
29:50could there be some other factor that they've overlooked?
29:55Hold on.
29:57That's it.
29:59It's bolted to the ground.
30:01The question I raise, well, in flight,
30:04the aircraft is in turbulence, it's bouncing around,
30:07there's different vibrations.
30:09With the aircraft on the ground
30:11or an engine mounted solidly to the ground,
30:13the airplane doesn't behave the same.
30:15There's different vibration modes.
30:17Is it possible that could change the outcome of the analysis?
30:22I think we need to see it in the air.
30:24Definitely.
30:26One of the problems of doing testing in a laboratory environment,
30:30which is very controlled,
30:32is that you can't always anticipate what will happen
30:35when you go out into the real world.
30:40These small planes do keep you on your toes.
30:43Imagine, for example, an orchestra
30:45that rehearses in an acoustically perfect concert hall
30:49and then performs outside with random noises,
30:53without the sound control.
30:55You can see how one might miss important factors about the sound.
31:00We've got to see what happens in the air.
31:02I said, well, the only way to really know
31:05is let's do a flight test and find out.
31:07Let's do something to absolutely determine this is the case,
31:10because we are at a point in the investigation
31:13we need to start eliminating things.
31:23The investigation into the crash of Flight 2311
31:26moves to Embraer headquarters in Brazil.
31:31We really wanted to look at what would happen in flight,
31:34in an actual flight, with this same malfunction.
31:39Tom Howter meets with representatives from Embraer
31:42and propeller manufacturer Hamilton Standard.
31:45The team immediately starts preparing for the test flight.
31:49Thank you for doing this.
31:52When I first proposed doing the flight test,
31:55it was not well received by almost everybody.
31:58People saw no need.
32:00Why are we spending the time, the money?
32:02Why are we doing this?
32:07But I pushed hard. I thought, well, we need to really prove this.
32:12Embraer's chief test pilot, Gilberto Schettini,
32:16has agreed to put the investigators' theory to the test.
32:20The risks, of course, is part of the game,
32:23so you always have to reduce the risk as much as possible,
32:27but you cannot avoid it, so you just accept it.
32:33The mindset of a test pilot is one, not perhaps of heroic bravery,
32:38but certainly one wants to be unflappable
32:41in the face of danger and unusual situations,
32:45because you're not very productive
32:47if you're terrified by the goings-on in the cockpit.
32:53Schettini will fly an Embraer 120
32:55that has been modified to recreate the failure on Flight 2311.
33:01So we've modified the quill.
33:03The teeth have been worn down, just like Flight 2311.
33:07A worn quill will be placed inside the propeller unit.
33:12This was potentially very high risk,
33:15because once we disconnected the transfer tube in flight,
33:18the pilots would have no way to control the propeller.
33:21We put a pitch lock here.
33:24It won't go past 22 degrees.
33:27A mechanical lock has also been added
33:29to stop the propeller from going flatter than 22 degrees.
33:34It would be too dangerous in the flight test
33:37to have the propeller blade go all the way to flat pitch.
33:40You'd lose control of the airplane. That was almost guaranteed.
33:43If the blades moved to 22 degrees,
33:45then we'd know they would have gone flat. All good?
33:49The propeller blades don't need to go completely flat
33:52to prove that Haute is on the right track.
33:56It was a high risk test.
33:58We had to take extra precautions
34:01in order not to repeat the accident.
34:05Real-time data will tell the team on the ground
34:08whether the propeller blades are going safely towards feather
34:11or moving dangerously flat.
34:14Everything says that if you have a disconnect,
34:16the normal frictional drag within the system
34:19will cause the components to rotate towards the feather position.
34:24But will that really happen in flight the same way?
34:30They're about to find out.
34:33We're comfortable that this test could be safely accomplished.
34:37But there's a difference between
34:39believing it can be safely accomplished and knowing.
34:45As the test plane climbs,
34:47Schettini takes it over an unpopulated area, just in case.
34:52There was a potential for a severe controllability problem
34:57such that the pilots might have to abandon the aircraft
35:00and parachute to the ground.
35:03The propellers have been set to a normal angle for flight,
35:06around 30 degrees.
35:09EMB 120, do you copy?
35:12There was a lot on the line in terms of the fact that
35:15what if this airplane crashes?
35:17What if we lose the airplane?
35:20Certainly, I'm the investigator in charge.
35:22I'm the one, you know, who's basically running this test.
35:25This could be all my responsibility.
35:28Copy. We are ready to disengage the prop.
35:33Basically, they would pull the lever
35:35that would disconnect the propeller control system from the propeller
35:40and see what happens.
35:43The most dangerous part of the test flight is now underway.
35:49I just thought that, well, it's happening.
35:52Let's do what we have to do and get this airplane on the ground.
35:57This was, in my opinion, a very dangerous maneuver
36:00because, after all, they didn't know what the outcome was going to be
36:04and they already knew the aircraft wasn't controllable
36:07under certain circumstances.
36:09Propeller blade angles causing no problems.
36:12No control issues.
36:15We were thinking about the test to do and nothing else.
36:19You have to focus on the job that you have to do ahead.
36:23And once you focus, you forget about everything else.
36:28As soon as the propeller quill is disengaged,
36:31the blades begin doing what they were designed to do,
36:34moving towards the feathered position.
36:38As it starts drifting towards feather,
36:40we thought, OK, well, this test is going to be a bust.
36:43It's just going to prove what everybody said it would do.
36:46You could see it in their faces.
36:48They didn't say anything, but you could just hear the relief.
36:52The propeller blades keep moving towards the fail-safe position.
36:57For Tom Howter, Brazil is a long way to come for failure.
37:02It seems like the test that he hoped would solve
37:05the mystery of Flight 2311
37:07is going to leave the investigation back at square one.
37:16With the cause of the Atlantic Southeast crash still unknown
37:20and the entire investigation on the line,
37:23the Brazilian test flight takes a dramatic turn.
37:28We saw that the RPM was increasing slowly, but it was increasing.
37:32So we knew that the propeller was going in the wrong direction.
37:39As the flight continues,
37:41the blades begin drifting in the opposite direction
37:44towards the dangerous flat position.
37:53Here we go.
37:57The aerodynamics, the vibration,
37:59the actual in-flight loads on the propeller
38:02are something that you just can't predict in a test.
38:06It's something that actually had to be flown.
38:11Schettini remains smooth and precise on the controls.
38:15Do you see speed?
38:18Yes, he does it.
38:24We started feeling a rolling moment to the left,
38:27and a yaw moment to the left.
38:31The blades go as flat as this test will allow.
38:3522 degrees.
38:37For Haute, it's a victory.
38:40The risky test flight has paid off.
38:43Their theory about the crash is back on solid ground.
38:46The Hamilton Standard and the FAA people just went white.
38:50I mean, they were just shocked.
38:52You could tell that everything they believed
38:54had just been thrown out the window.
38:58That's as flat as they're going to get.
39:03Do you have what you need?
39:05Affirmative.
39:06We have everything we need.
39:10Okay, going back.
39:17Once the test flight is finished, it is finished.
39:21Don't stay around looking for trouble.
39:23Go back home.
39:26Good work.
39:27Thanks, man.
39:29Seeing the data right then, it took a load off.
39:31I said, wow, I mean, we now know what happened.
39:34It was obvious.
39:36Looks like you have some work to do.
39:46Hello.
39:48The team has just one more question to answer
39:51before they can explain the crash.
39:54What happens when blades go completely flat?
39:58In the flight test, they were only able to go
40:00to a blade angle of about 22 degrees for safety reasons.
40:04Start it.
40:06But during my flight simulations,
40:09I went down to flight angles as low as 3 degrees.
40:13Any time.
40:16In a flight simulator,
40:18Jim Ritter recreates the fatal propeller malfunction
40:21aboard Atlantic Southeast Airlines Flight 2311.
40:26As the blade angle got to very low values,
40:29the airplane was essentially uncontrollable.
40:33The simulation allows him to experience
40:36what the test pilot couldn't.
40:41Flight test proved we could have a blade go to flat pitch.
40:44Simulator proved you'd lose control if it did.
40:47Thanks.
40:49That was helpful.
40:51You could say that the simulator testing
40:54was kind of like the final piece of the puzzle.
40:59Investigators finally understand
41:01the full story behind the deadly crash.
41:05When the flight crew began preparations for landing,
41:08the teeth on the quill were worn down.
41:10Still operational.
41:12Slowing for approach speed.
41:16Preparing for landing put renewed pressure
41:19on the already worn teeth in the quill.
41:22They could no longer hold.
41:24Once the teeth gave way,
41:27the propeller blades were free to drift to a different angle.
41:32As the turbulence of flight
41:34and mechanical vibrations from the engine shook the propeller,
41:38the blades moved to a dangerously flat position.
41:43The fail safe failed.
41:47The propeller's design couldn't hold the blades at a safe angle,
41:51and the plane became less and less controllable.
41:57What's going on?
41:59See anything?
42:01There's nothing.
42:03What's going on with this thing? I can't hold it.
42:08Get out of it!
42:10Come on! Come on!
42:12For a while, you can kind of fight this,
42:14putting in control movements with the wheels, the rudder,
42:17but unfortunately, they were in a situation
42:20where it didn't matter if you were the best pilot on the planet,
42:24you were not going to be able to control that airplane.
42:27It's going to roll over, it's going to dive towards the ground.
42:31Ironically, human error is almost always
42:34underneath the causes of an accident,
42:36even if it wasn't the pilot or a mechanic.
42:39In this particular case, an engineering change was made,
42:42which, well-intentioned actually, did not work out.
42:45No!
42:47Oh, God!
42:49No!
42:55The Warren Quilt East was a time bomb waiting to go off.
43:00There was nothing they could have done to save that plane.
43:03What I really felt was, OK, now that we know it,
43:06we've got to tell the rest of the world
43:08and get operators to start changing their equipment,
43:11like, right now.
43:13The fail-safe system doesn't work.
43:15After the accident, additional safeguards were added
43:19to prevent this type of failure,
43:21a change that affected not only the Embraer,
43:24but several other turboprop aircraft.
43:27The FAA also ordered more frequent inspections
43:30of propeller quills.
43:32The most important thing we have learned
43:35from the accident at Brunswick is assumptions.
43:39You cannot rely on assumptions.
43:41It was assumed that ground tests were as good as flight tests.
43:45That one assumption, unfortunately,
43:47turned out to be fatal for some people.
43:50Unfortunately, it turned out to be fatal for some people.