Understanding Air France 447 (2 page)

01:45 The flight entered an area of weather and the crew discussed their desire to climb to FL370 to try and get above the weather, but that it was too warm to climb to that altitude.

01:46 First Officer Bonin dimmed the cockpit lights, and turned on the landing lights to see outside. He noted, “It looks like we’re entering the cloud cover. It would have been good to climb now, eh.”

01:49 AF447 exited radar coverage as it passed the SALPU waypoint.

1:51:20 First Officer Bonin remarked “I don’t have the impression there was... much... storm, not much.” The captain remarked, “It’s going to be turbulent for my rest.”

01:56:16 The captain asked First Officer Bonin if he would be doing the landing, and if he were qualified. Bonin replied “yeah.”

02:00 First Officer Robert returned from his rest break and Captain Dubois left for his. The captain did not provide any briefing to Robert other than to confirm HF frequencies ahead. First Officer Bonin was the pilot flying (PF) in the right seat, and the designated pilot in command in the captain’s absence. Robert took the captain’s seat but was second in command. Bonin informed Robert of the inability to climb and that there would be some turbulence ahead like they had recently encountered.

02:01 A third ADS logon attempt failed due to the erroneous registration information that was entered into the Eurocat system.

02:02-02:07 The airplane experienced light turbulence of between 1.1 and 1.25 g’s.

02:06 The two first officers informed the cabin crew that it was going to be turbulent two minutes ahead.

02:07-02:10 The turbulence was borderline moderate, up to 1.5 g’s. Even with the autopilot on the bank angle varied between about three degrees right and five degrees left.

02:08 First Officer Robert adjusted the radar gain setting to increase its sensitivity and suggested a deviation to the left of course. They turned the airplane 12° left of the planned track to avoid the worst of the weather.

02:09:46 The flight encountered an updraft. A sound typical of ice crystals hitting the fuselage was heard. Bonin reduced the cruise speed from Mach .82 to Mach .80, which is the recommended speed for turbulence penetration. The engine speed reduced from 100% N
₁
to 84%.

02:10:00 The updraft intensified as the airplane pitched down from 2° to 0° to maintain altitude; the autothrust system reduced thrust in order to maintain the speed.

02:10:05 The pitot tubes (the airspeed measurement probes) clogged with ice crystals and the left side indicated airspeed fell from 275 to 60 knots but remained displayed on the PFD (Primary Flight Display). The indicated airspeed
¹
on the standby instrument fell from 275 to 139 then rose to 223 knots. The right side displays are not recorded, but it is likely that they suffered similar degradations. The autopilot disconnected and the flight director bars disappeared. The airplane’s flight control law changed from Normal to Alternate 2, shutting down many of the built-in protections and increasing the sensitivity to roll inputs.

Due to the loss of indicated airspeed, internal altimeter corrections were automatically recalculated as if the airplane were flying at the lower speeds. This resulted in false indications of a decrease in altitude of about 300 feet and a downward vertical speed approaching 600 feet per minute.

02:10:07 Bonin said, “I have the controls.” The airplane rolled right and Bonin, the Pilot Flying (PF), began hand flying the airplane and made nose up and left roll inputs.

02:10:08 The autothrust disconnected and went into thrust-lock mode, freezing the power setting at 83% N
₁
until a pilot assumed manual control of the thrust levers.

02:10:10 The pitch attitude rose from 0° to 6° and the vertical speed increased through 1,800 feet per minute. The g load, due to the pull up, reached 1.6 g’s and the stall warning alerted briefly.

The PF struggled to regain control over the bank angle and overcontrolled the roll input with a series of ten alternating left and right banks. The control inputs were exactly out of phase with the roll motion. Peak bank angle and opposite lateral stick input each occurred at the same time. The roll gradually came under control over the next 30 seconds.

02:10:13 The airspeed on the standby instrument decayed again, and over the next four seconds fell from 270 to 73 knots.

02:10:17 The flight directors appeared for four seconds and directed a return to the cruise altitude.

02:10:20 The pitch continued to increase through 11°, and vertical speed increased through 6,000 feet per minute as the flight directors disappeared again. These pilot inputs were excessive and incompatible with the recommended airplane handling practices for high altitude flight.

02:10:23 Thrust lock was deactivated with an autothrust disconnect button despite the ECAM instructions to do so by moving the thrust levers. The thrust levers remained in the climb detent. (The ECAM, Electronic Centralized Aircraft Monitor, displays the fault messages and procedures for dealing with them.) The engine speed increased to 104% within 12 seconds.

02:10:26 The aircraft’s vertical speed reached its maximum of 6,900 feet per minute, as the airplane passed 36,000 feet with a pitch attitude of 12°.

02:10:27 The flight directors reappeared. This time, they had switched from altitude hold mode to provide guidance for maintaining the current heading and vertical speed, which at the time was a 6,000 feet per minute climb.

First Officer Robert instructed Bonin to watch his speed. Bonin replied, “okay, okay, I’m going back down.”

Some nose down inputs were made, pitch reduced slightly and thrust was reduced. But the pitch attitude remained well above normal and the airplane continued to climb.

Robert said, “Go back down. According to that we’re going up. According to all three you're going up, so go back down.”

Bonin replied, “Okay,” and again Robert said, “You’re at...go back down.”

02:10:32 The pitch attitude was reduced to about 10° and the vertical speed decreased to 4,000 feet per minute as the airplane climbed through 37,000 feet. The angle of attack, typically at 2.5° for cruise, had so far remained below about 4°.

02:10:36 The flight director bars disappeared again. The airspeed on the left side displayed correctly, indicating 223 knots. Fifty knots of airspeed had been lost in the climb from the time the autopilot disconnected 31 seconds earlier. The standby instrument’s airspeed remained abnormally low (the right side display is unknown).

02:10:42 The flight directors reappeared for one second. They provided guidance to maintain a climb rate of 1,400 feet per minute, the current vertical speed.

02:10:47 The flight directors reappeared for 53 seconds (until 2:11:40), again the guidance was to maintain the climb rate of 1,400 feet per minute. The thrust levers were moved back to 2/3 between the idle and climb settings, and the N1 decreased to 85%.

02:10:50 Attempts were made to call the captain back by ringing a call chime that sounds in the crew rest area.

02:10:51 Bonin continued to make nose up inputs and the pitch attitude increased to 16°. The airplane no longer had sufficient energy to maintain the flight director target vertical speed. A series of small roll movements began. Bonin countered each with lateral stick input. The stall warning triggered again and remained on for the next 45 seconds.

02:10:57 The stall angle of attack was reached and the airplane began to shake due to the stall buffet. Thrust was advanced to TOGA (Take Off Go Around - full power). Bonin continued to make nose up inputs as the airplane continued a shallow climb. The engine speed increased to 103% N
₁
.

02:11:00 Robert said, “Above all, try to touch the lateral controls as little as possible, eh.”

02:11:04 The roll oscillations continued - 9° to the right, 16° to the left, and Bonin’s inputs increased, using up to full left and right stick input to counteract them.

02:11:07 The airspeed indication on the standby instrument increased from 129 to 183 knots. The last of the pitot icing had cleared and all three airspeed indications were then displaying correctly. (The normal indicated airspeed for Mach .81 at FL 380 is about 260 knots.)

02:11:10 A maximum altitude of 37,924 feet was reached. The airplane had gained 3,000 feet and lost 90 knots of indicated airspeed in the one minute and seven seconds since the autopilot disconnected.

02:11:20 The stall warning still sounding, Robert said, “But we’ve got the engines, what’s happening?”

02:11:22 Nose up inputs were maintained but the airplane began to descend. The airplane started to bank consistently to the right. Left stick inputs were made which slowed the rolling motion for a few seconds.

02:11:24 Robert again asked, “Do you understand what’s happening or not?”

02:11:30 The bank angle increased to the right. Bonin held full left stick with virtually no effect on the bank angle. The airplane began a right turn that would bring it around 225° before it hit the water three minutes later.

02:11:32 Bonin said, “I don’t have control of the airplane any more now. I don’t have control of the airplane at all.”

02:11:38 Robert said, “Controls to the left,” and made two brief full-left control inputs. Bonin continued to hold his sidestick full left and moved it full aft where it was held for almost 40 seconds. The descent rate increased to 10,000 feet per minute.

The pitch attitude fluctuated between about 10° and 16° nose up, while the angle of attack steadily climbed to 40°.

02:11:42 The captain entered the cockpit. The indicated airspeeds fell below 60 knots which rendered the angle of attack sensors invalid. The stall warning silenced. As the speeds fell below 30 knots the airspeed indication was replaced by a red SPD flag. The airplane was right wing low with varying bank angles up to 45°, even though Bonin’s sidestick was full left in an attempt to control it.

The captain asked, “What are you doing?”

Robert replied, “What’s happening? I don’t know, I don’t know what’s happening.”

Bonin said, “We’re losing control of the airplane there.”

Robert added, “We lost all control of the airplane, we don’t understand anything, we’ve tried everything.”

02:11:47 The pitch attitude porpoised from 8° to 15° nose up. The thrust levers were moved to idle and the nose pitched down to about 11° below the horizon. The vertical speed increased to 15,000 feet per minute. The engine speed decreased to 58% over the next 20 seconds.

02:11:55 The stall warning triggered briefly.

02:12:04 Bonin said, “I have the impression that we have some crazy speed, no, what do you think?” He then deployed the speedbrakes and the nose pitched up level with the horizon. Robert told him not to extend the speedbrakes and then they were retracted. The nose returned to 8° below the horizon, then pitched up again.

The airplane continued to descended with vertical speeds between 10,000 and 15,000 feet per minute as the pitch attitude oscillated between -8° and +15°.

Each time the nose pitched down the angle of attack reduced slightly (though remaining above 30°), the airspeed indication reappeared with speeds between 60 and 80 knots, and the stall warning reactivated.

The bank angle rocked between 20° and 40° to the right, accompanied by corresponding yawing motions and back and forth lateral accelerations. Both pilots and the automatic yaw damper function fought to keep the airplane upright.

02:12:10 The thrust levers were positioned to the CLB (climb power) detent and the N
₁
increased from 58% to 105% in 10 seconds.

02:12:30 For the first time in a minute, the bank angle passed through wings level as it oscillated left and right, the PF made large sidestick deflections to counter every roll action.

02:12:33 The thrust levers were moved from the climb detent to TOGA.

02:12:44 The airplane descended through 20,000 feet.

02:12:45 The airplane began to roll right again, and the bank angle exceeded 40° within a few seconds. Full left sidestick was again applied and held steady for 20 seconds.

02:13:18 The airplane descended through 10,000 feet. Bonin said, “We’re there, we’re there, we’re passing level one hundred” (10,000 feet). They had already descended 28,000 feet.

Robert said, “Wait, me, I have, I have the controls, eh.” He made a left input for about seven seconds, but Bonin never released his sidestick, and a synthetic voice announced “DUAL INPUT.”

Bonin expressed his shared confusion again, “What is… how come we’re continuing to go down now?”

Robert instructed the captain to see if a reset of the flight control computers could help. The captain remarked that it would not do anything, but he reset primary and secondary flight control computers, PRIM 1 and SEC 1, anyway.

02:13:36 Bonin called out “Nine thousand feet.” His sidestick was still about half way back, the elevator and stabilizer were full nose up (trying to comply with Bonin’s pitch-up order) and the thrust levers remained at TOGA.

Robert said, “Climb climb climb climb!”

Bonin replied, “But I’ve been at max nose up for a while.”

Robert pushed his sidestick all the way forward for a five seconds, “DUAL INPUT” sounded, and the captain said, “No no no, don’t climb!”

Robert said, “So, go down” and pushed his own stick forward again while the thrust levers were pulled back to climb power. Bonin, however, continued to pull back, and “DUAL INPUT” sounded again.

02:13:45 Robert said, “So give me the controls, the controls to me, controls to me.”

Bonin acknowledged, “Go ahead, you have the controls, we are still in TOGA, eh.”

Robert lowered the nose to 7° below the horizon, the airspeeds displayed once more, along with the stall warning.

02:13:52 Seven seconds later, despite Robert saying he had the controls, Bonin began to pull back on the sidestick again. “DUAL INPUT” was announced, and the airplane started to pitch up.

02:14:05 The captain warned, “Watch out, you’re pitching up there.”