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-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-1: Oh God, Oh God…
RDO-1: 427, emergency!
CAM-2: [Sound of scream]
CAM-1: Pull… pull…
CAM-1: [Sound of screaming]
CAM-2: No… END OF TAPE.
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.