Air France update

[Baradium]

To be honest, I don't think this stuff belongs in the missing link section, so I'm starting a new thread here.


There are two sections.   The first section is an NTSB advisory regarding two incidents involving Airbus A330 airliners.   The second section is from an e-mail purporting to tell the story of a crewmember of the NWA aircraft mentioned in the advisory.
 

************************************************************
NTSB ADVISORY
************************************************************
 
National Transportation Safety Board
Washington, DC 20594
 
June 25, 2009
 
************************************************************
 
NTSB INVESTIGATING TWO RECENT INCIDENTS INVOLVING
POSSIBLE A-330 SPEED AND ALTITUDE INDICATION ANOMALIES
 
 
************************************************************
 
 
The National Transportation Safety Board is investigating
two recent incidents in which airspeed and altitude
indications in the cockpits of Airbus A-330 aircraft may
have malfunctioned.
 
The first incident occurred May 21, 2009, when TAM Airlines
flight 8091 (Brazilian registration PT-MVB) flying from
Miami, Florida to Sao Paulo, Brazil, experienced a loss of
primary speed and altitude information while in cruise
flight. Initial reports indicate that the flight crew noted
an abrupt drop in indicated outside air temperature,
followed by the loss of the Air Data Reference System and
disconnections of the autopilot and autothrust, along with
the loss of speed and altitude information. The flight crew
used backup instruments and primary data was restored in
about 5 minutes. The flight landed at Sao Paulo with no
further incident and there were no injuries and damage.
 
The Safety Board has become aware of another possibly
similar incident that occurred on June 23 on a Northwest
Airlines A-330 (registration unknown) flying between Hong
Kong and Tokyo. The aircraft landed safely in Tokyo; no
injuries or damage was reported. Data recorder information,
Aircraft Condition Monitoring System messages, crew
statements and weather information are being collected by
NTSB investigators.
 
Further information on both incidents will be released when
it becomes available.
 
###
 
NTSB Public Affairs
(202) 314-6100
Ted Lopatkiewicz
lopatt@ntsb.gov
 

 
E-mail starts below:

From the Desk Of:
ARCCA
From a retired NWA buddy of mine
 
 
This from Brent Stratton, a friend and NWA pilot I flew the B-757 with out of our Tokyo base.........Now obviously on the A-330:
 
Well, I'm sure you have all heard of the Air France accident. I fly the same plane, the A330.
 
 
Yesterday while coming up from Hong Kong to Tokyo , a 1700nm 4hr. flight, we experienced the same problems Air France had while flying thru bad weather.
I have a link to the failures that occurred on AF 447. My list is almost the same.
http://www.eurocockpit.com/images/acars447.php
 
The problem I suspect is the pitot tubes ice over and you loose your airspeed indication along with the auto pilot, auto throttles and rudder limit protection. The rudder limit protection keeps you from over stressing the rudder at high speed.
 
Synopsis;
Tuesday 23, 2009 10am enroute HKG to NRT. Entering Nara Japan airspace.
 
FL390 mostly clear with occasional isolated areas of rain, clouds tops about FL410.
Outside air temperature was -50C TAT -21C (your not supposed to get liquid water at these temps). We did.
 
As we were following other aircraft along our route. We approached a large area of rain below us. Tilting the weather radar down we could see the heavy rain below, displayed in red. At our altitude the radar indicated green or light precipitation, most likely ice crystals we thought.
 
Entering the cloud tops we experienced just light to moderate turbulence. (The winds were around 30kts at altitude.) After about 15 sec. we encountered moderate rain. We thought it odd to have rain streaming up the windshield at this altitude and the sound of the plane getting pelted like an aluminum garage door. It got very warm and humid in the cockpit all of a sudden.
Five seconds later the Captains, First Officers, and standby airspeed indicators rolled back to 60kts. The auto pilot and auto throttles disengaged. The Master Warning and Master Caution flashed, and the sounds of chirps and clicks letting us know these things were happening.
Jerry Staab, the Capt. hand flew the plane on the shortest vector out of the rain. The airspeed indicators briefly came back but failed again. The failure lasted for THREE minutes. We flew the recommended 83%N1 power setting. When the airspeed indicators came back. we were within 5 knots of our desired speed. Everything returned to normal except for the computer logic controlling the plane. (We were in alternate law for the rest of the flight.)
 
We had good conditions for the failure; daylight, we were rested, relatively small area, and light turbulence. I think it could have been much worse.. Jerry did a great job fly and staying cool. We did our procedures called dispatch and maintenance on the SAT COM and landed in Narita. That's it.

[Rooster Cruiser]

Pitot icing is NEVER ANY FUN!!!     I had a PC-12 that would have the Pitots ice up every time I was in IMC and the temps were below -20C.  It turned out that that airplane had a bunch of dust contamination inside the Pitots beyond the heater, and it would ice up there.  There is nothing as disconcerting as watching BOTH airspeed indicators unwind from cruise down to zero while in clouds in the Flight Levels!  Fortunately for me, the PC-12 had no autothrottles or fly by wire so the auto pilot continued to do its job.  Also, my altimeters were unaffected.

The first time it happened I just sat there for a few seconds, and once I realized my problem was isolated to just the airspeed indicators I decided to let the autopilot do its job since I knew my destination was VMC.  I kept the power setting where it was, and went by memory for appropriate power settings for my descent profile.  Once I descended out of clouds and back into warmer air (about -10C) the ice would melt from within the pitot tubes and my airspeed indicators went back to normal.

To this day, I cannot describe the horror of watching an instrument I am accustomed to working flawlessly go Tango Uniform for no known reason!  I'd have hated to have to deal with that in the middle of a thunderstorm line in any airplane.  That's really getting the deck stacked against yerself, IMHO.

More reason to avoid Cb's if at all possible.  I have read elsewhere that other flights deviated 70NM west of track that night to avoid the ITCZ complex that AF447 flew through.  Food for thought.   

RC

[Ragwing]

RC,

What  I am watching for is information on the vertical stabilizer.
It was found 20-30 miles before the other debris.
And it was in one piece, not broken up very much

It makes some of us wonder if the stabilizer came off first.
Especially since the ac flew into high turbulence area.

If the aircraft had stalled out due to pitot tube freeze up, the aircraft would have slowed down and stalled out.
How would vertical stabilizer be so far away.

We have not found many detailed pictures of the debris.
Makes it frustrating for our failure analysis group.

[Baradium]

RC,

What  I am watching for is information on the vertical stabilizer.
It was found 20-30 miles before the other debris.
And it was in one piece, not broken up very much

It makes some of us wonder if the stabilizer came off first.
Especially since the ac flew into high turbulence area.

If the aircraft had stalled out due to pitot tube freeze up, the aircraft would have slowed down and stalled out.
How would vertical stabilizer be so far away.

We have not found many detailed pictures of the debris.
Makes it frustrating for our failure analysis group.

Ragwing:  the failure mode referenced in the first post of this thread could lead the flight crew to incorrectly perceive that the aircraft was going too slow.  In that case the breakup would be due to extreme overspeed, which could explain the vertical stab seperation.

Note that this is not the first time that such an accident has happened.  On accident involved a DC9 and high lift devices seperating from the aircraft because they deployed them thinking they were "slow" while they were actually overspeeding.  The high lift device seperation led to a loss of control and subsequent impact with terrain.

The two other A330 incidents involved flight crews that realized that they should not be going that slow given their power settings.  They used published power settings given for airspeed indication failure and thus were able to maintain control until accurate data was restored.

[Fabo]

I am not entirely sure how do AoA indicators work, but would they be operating in such conditions? Because I see them as quite a handy way of monitoring aircraft speed in comparison to actuall stall speed...

[Baradium]

I am not entirely sure how do AoA indicators work, but would they be operating in such conditions? Because I see them as quite a handy way of monitoring aircraft speed in comparison to actuall stall speed...

Depends on the aircraft.  On the CRJ the AOA indicator determines where our green line (1.3 Vs1)  and our lower red checkerboard (Vs1)  are.   (Vs1 is your stall speed in a given configuration)    The airbus is another class cockpit aircraft, so it would likely appear the same way. However, in cruise you are unlikely to be in an area where the lower checkerboard would normally appear.   The AOA range that gives your your checkerboard and green line values is adjusted as you change configuration, as you'll have a much higher AOA with full flaps before you stall vs a clean wing.   These indications, as well as rate of pitch change (trend monitoring) determine when various aspects of the stall protection system come into play.

On steam guage aircraft, the AOA is used primarily for the stall protection system, although I believe many aircraft have an actual AOA indicator (we don't on the CRJ).

Useful information, but not as easy to just look at and be able to eyeball your speed.    As we get to high altitudes, stall speed actually increases (just as Vmo indicated decreases).  When dealing with highspeed aircraft this is referred to as "coffin corner" as your MMo (mach max operating) and Vs start to converge.    I remember reading that the U2 at it's high altitude cruise has a 10 knot margin for airspeed between stall and MMo.

Coffin corner is a dangerous place to operate in for a number of reasons.  First, as you turn your stall speed increases due to the increased aircraft loading.   So if you are far enough into this corner, you can turn and cause your stall speed to exceed your MMo quite easily.   This is only relevent because the increasing stall speed means that your "green line" ends up still being close to your indicated airspeed as you get to high altitudes.  Airliners do not tend to operate in ranges where the corner is nearly so "tight" although we do start restricting bank angle as we climb for this reason.   In our case at high altitudes our bank angle is restricted to 15 degrees, somewhat like we restrict our angle to 15 degrees when we are below ref +10 on approach or below V2+10 on climbout (only really relevent in single engine operations when we need to maintain V2 for obstacle clearance).

[Fabo]

Yep, I know about buffet margin and Mmo vs. Vmin et cetera et cetera. I thought about actual indicator gauges. Well anyway, after looking on the plane it have stroken me that they just would.

[Baradium]

Yep, I know about buffet margin and Mmo vs. Vmin et cetera et cetera. I thought about actual indicator gauges. Well anyway, after looking on the plane it have stroken me that they just would.

Fabo, I'm sorry.  I have no idea what you mean with your third sentence.

Also, my point was that even if you see the AOA, it varies with indicated airspeed by altitude, so it's not so easy to determine with that method.  It is noteworthy that airbus has a published procedure in case you aren't sure of your airspeed reliability.  This is the procedure that TAM and NWA used that resulted in nonevents from their malfunctions.


I've seen some radar picture preported to be from the time frame that they went through the storm.  If it's true, then the storm was MUCH larger than anything they had any buisiness being near, let alone going straight through.

[Rooster Cruiser]

They're finally giving up on ever finding the CVR and FDR at the bottom of th ocean.  It looks like we'll never know for sure exactly what was the sequence of events that brought down AF447.

RIO DE JANEIRO – Two ships using U.S. listening devices to search for the black boxes of Air France Flight 447 were ending their hunt Friday, an American commander said.

A French nuclear submarine, however, will continue to look.

U.S. Air Force Col. Willie Berges, the Brazil-based commander of American military forces supporting the effort, said one ship towing a U.S. Navy listening device had already stopped searching.

"The last ship will be departing the search area today," Berges said. He didn't know what time the final ship would leave the search area.

Flight 447 crashed into the Atlantic Ocean, more than 900 miles (1,450 kilometers) off Brazil's northeastern coast, on June 1. All 228 people aboard died. Investigators have said without the black boxes, it may be impossible to know with certainty what caused the crash.

Berges said the ships, which have been searching for the cockpit voice and flight data recorders since June 15, had "no success — nothing was tracked."

The commander said a French nuclear submarine would continue trying to pick up emergency signals from the black boxes, but he didn't know for how long.

The black boxes are built to emit emergency "pings" for about 30 days, and then slowly fade away.

Two teams of American personnel were operating the U.S. Navy pinger locators that were towed by French-contracted ships. A French nuclear submarine is still scouring a search area with a radius of 50 miles (80 kilometers) in the area where the plane is thought to have crashed.

French investigators say 640 parts of the plane — including a nearly intact tail, an engine cover, uninflated life jackets, seats and kitchen items — have been plucked from the Atlantic Ocean, some of them huge pieces that had to be handled by cranes.

The debris was initially held in the Brazilian city of Recife, but the material is aboard a ship en route to France, where investigators will search for clues.

French crash investigators last week issued a preliminary report into the crash, finding that problems with the plane's speed sensors were one of several factors in the crash. It said the plane hit the ocean intact and belly first at a high rate of speed.

Experts have found no signs of an explosion or terrorist act.

[Rooster Cruiser]

AP is finally reporting on the stuff we discussed in here over a month ago.  Expect to see more stories on it soon:

http://news.yahoo.com/s/ap/20090807/ap_on_go_ot/us_planes_speed_malfunction

APNewsBreak: Airspeed systems failed on US planes
         
By JOAN LOWY, Associated Press Writer Joan Lowy, Associated Press Writer – 7 mins ago
WASHINGTON – On at least a dozen recent flights by U.S. jetliners, malfunctioning equipment made it impossible for pilots to know how fast they were flying, federal investigators have discovered. A similar breakdown is believed to have played a role in the Air France crash into the Atlantic that killed all 228 people aboard in June.

The discovery suggests the equipment problems are more widespread than previously believed. And it gives new urgency to airlines already scrambling to replace air sensors and figure out how the errors went undetected despite safety systems.

The equipment failures, all involving Northwest Airlines Airbus A330s, were brief and were noticed only after safety officials began investigating the Air France crash — on a Rio de Janeiro to Paris flight — and two other recent in-flight malfunctions. The failures were described by people familiar with the investigation who spoke only on condition of anonymity because they were not authorized to comment publicly.

While a car's speedometer uses tire rotation to calculate speed, an airplane relies on sensors known as Pitot tubes to measure changing air pressure. Computers interpret that information as speed. And while a car with a broken speedometer might be little more than an inconvenience, many airplane control systems rely on accurate speed information to work properly.

Like the fatal Air France flight, the newly discovered Northwest incidents and the two other malfunctions under investigation all involved planes with sensors made by the European electronics giant Thales Corp. The Air France crash called into question the reliability of the sensors and touched off a rush to replace them.

Many companies, however, simply replaced them with another Thales model. As it became clear the problem was more widespread, Airbus and European regulators told companies to replace at least two of the three sensors on each plane with models made by North Carolina-based Goodrich Corp. The planes are allowed to continue flying while the switch is made.

Thales officials declined to comment. The company has previously said its sensors were made to Airbus specifications.

The Northwest incidents were discovered when Delta Air Lines, which merged with Northwest last year, reviewed archived flight data for its fleet of 32 Airbus A330s, the people close to the inquiry said. All the planes involved landed safely.

Aviation experts said the discovery could provide clues to what caused Air France Flight 447 to crash into the Atlantic en route from Brazil to France on June 1, and what might be done to prevent future tragedies.

French investigators have focused on the possibility that Flight 447's sensors iced over and sent false speed information to the computers as the plane ran into a thunderstorm at about 35,000 feet.

An important part of the investigation focuses on 24 automatic messages the plane sent during its final minutes. They show the autopilot was not working, but it is unclear whether the pilots shut it off or whether it shut down because of the conflicting airspeed readings.

Three weeks after the Air France crash, the U.S. National Transportation Safety Board announced it was investigating two other A330 flights that experienced a loss of airspeed data.

The most recent was on June 23, when a Northwest flight hit rain and turbulence while on autopilot outside of Kagoshima, Japan. According to an NTSB report, speed data began to fluctuate. The plane alerted pilots it was going too fast. Autopilot and other systems began shutting down, putting nearly all the plane's control in the hands of the pilot, something that usually happens only in emergencies.

In May, a plane belonging to Brazilian company TAM Airlines lost airspeed and altitude data while flying from Miami to Sao Paulo, Brazil. Autopilot and automatic power also shut down and the pilot took over, according to an NTSB report. The computer systems came back about five minutes later.

"These two cases we know were dealt with effectively by the crew, and we think this happened in Air France and maybe wasn't dealt with effectively," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Va., an aviation safety think tank.

Morgan Durrant, a spokesman for the only other U.S. airline that operates A330s, US Airways, said it had not seen similar problems in its 11-plane fleet of the jetliners.

Delta/Northwest and US Airways recently completed replacing older Thales tubes with new Thales tubes. The companies say they are now replacing them with Goodrich tubes.

In June, the Air France pilots' unions urged its members to refuse to fly Airbus A330s and A340s unless their Thales sensors had been replaced.

The Federal Aviation Administration hasn't issued a safety directive, but spokeswoman Laura Brown said the agency hopes to have one soon.