Boeing issues warning to B-737 operators, due to accident investigation findings

The following is the text of a memo issued by Boeing to operators of Boeing 737 airplanes. The information reflects preliminary findings by the Dutch Safety Board regarding their investigation of the crash of a Turkish Airlines Boeing 737-800 aircraft at Amsterdam on February 25, 2009:

FROM: THE BOEING COMPANY

TO: MOM [MESSAGE NUMBER:MOM-MOM-09-0063-01B] 04-Mar-2009 05:29:01 AM US PACIFIC TIME Multi Operator Message

This message is sent to all 737-100,-200,-300,-400,-500,-600,-700,-800,-900,-BBJ customers and to respective Boeing Field Service bases, Regional Directors, the Air Transport Association, International Air Transport Association, and Airline Resident Representatives.

SERVICE REQUEST ID: 1-1228079803 

ACCOUNT: Boeing Correspondence (MOM) DUE DATE: 10-Mar-2009 PRODUCT TYPE: Airplane

PRODUCT LINE: 737 PRODUCT: 737-100,-200,-300,-400,-500,-600,-700,-800,-900,-BBJ ATA: 3400-00

SUBJECT: 737-800 TC-JGE Accident at Schiphol Airport, Amsterdam - 25 February 2009

REFERENCES: /A/ 1-1222489391 Dated 25 February 2009

Reference /A/ provides Boeing's previous fleet communication on the subject event.

The US NTSB, FAA, Boeing, the Turkish DGCA, the operator, the UK AAIB, and the French BEA continue to actively support the Dutch Safety Board's (DSB) investigation of this accident. 

The DSB has released a statement on the progress of the investigation and has approved the release of the following information.

While the complex investigation is just beginning, certain facts have emerged from work completed thus far:

- To date, no evidence has been found of bird strike, engine or airframe icing, wake turbulence or windshear.

- There was adequate fuel on board the airplane during the entire flight.

- Both engines responded normally to throttle inputs during the entire flight.

- The airplane responded normally to flight control inputs throughout the flight.

The Digital Flight Data Recorder (DFDR) data indicates that the crew was using autopilot B and the autothrottle for an ILS (Instrument Landing System) approach to runway 18R at Amsterdam Schiphol airport.

During the approach, the right Low Range Radio Altimeter (LRRA) was providing accurate data and the left LRRA was providing an erroneous reading of -7 to -8 feet.

When descending through approximately 2000 feet the autothrottle, which uses the left radio altimeter data, transitioned to landing flare mode and retarded the throttles to the idle stop. The throttles remained at the idle stop for approximately 100 seconds during which time the airspeed decreased to approximately 40 knots below the selected approach speed.

The two LRRA systems provide height above ground readings to several aircraft systems including the instrument displays, autothrottle, autopilots and configuration/ground proximity warning. If one LRRA provides erroneous altitude readings, typical flight deck effects, which require flight crew intervention whether or not accompanied by an LRRA fault flag, include:

- Large differences between displayed radio altitudes, including radio altitude readings of -8 feet in flight.

- Inability to engage both autopilots in dual channel APP (Approach) mode

- Unexpected removal of the Flight Director Command Bars during approach

- Unexpected Configuration Warnings during approach, go-around and initial climb after takeoff

- Premature FMA (Flight Mode Annunciation) indicating autothrottle RETARD mode during approach phase with the airplane above 27 feet AGL. There will also be corresponding throttle movement towards the idle stop.  Additionally, the FMA will continue to indicate RETARD after the throttles have reached the idle stop

Boeing Recommended Action 

- Boeing recommends operators inform flight crews of the above investigation details and the DSB interim report when it is released. In addition, crews should be reminded to carefully monitor primary flight instruments (airspeed, attitude etc.) and the FMA for autoflight modes.

More information can be found in the Boeing 737 Flight Crew Training Manual and Flight Crew Operations Manual. Operators who experience any of the flight deck effects described above should consult the troubleshooting instructions contained in the 737 Airplane Maintenance Manual. Further, 737-NG operators may wish to review 737NG-FTD-34-09001 which provides information specific for the 737-NG installation.  Initial investigations suggest that a similar sequence of events and flight deck indications are theoretically possible on the 737-100/-200/-300/-400/-500. Consequently the above recommendations also apply to earlier 737 models.

Thanks to the reader who passed this memo along to me.

Dutch Safety Board's preliminary report on the Turkish Airlines crash at Amsterdam

The Dutch Safety Board has issued a preliminary report regarding the Turkish Airlines Boeing 737-800 accident at Amsterdam last month.  Turkish Airlines Flight TK 1951, which was arriving from Istanbul,  was on approach to runway 18R (AKA 'the Polderbaan') at Amsterdam's Schiphol Airport on February 25, 2009 when it crashed into a field short of the runway threshold. Four crew members and five passengers were killed in the accident. Twenty-eight of the 80 people who were injured remain hospitalized, according to the Dutch report.

The Dutch Safty Board's preliminary report states that the flight experienced no problems "until just before the approach." According to information obtained by investigators from the aircraft's cockpit voice recorder and flight data recorder, the aircraft was descending, with the auto-pilot engaged, when "an irregularity occurred" at 1950 feet.

Quoting from the English version of the Dutch Safety Board report posted on the Board's website:

At a height of 1950 feet the left radio altimeter suddenly indicated a change in altitude -- from 1950 feet to -8 feet -- and passed this onto the automatic pilot. This change had a particular impact upon the automatic throttle system which provides more or less engine power.

The radio altimeter normally measures the altitude of the plane above the ground very accurately and can start registering this from 2500 feet. As already mentioned, this radio altimeter is very significant for providing the appropriate power for an automatic landing.

A Boeing is fitted with two radio altimeters, a left one and a right one. The black box has shown that this deviation only occurred in the left radio altimeter.

The voice recorder has shown that the crew were notified that the left radio altimeter was not working correctly (via the warning signal “landing gear must go down”).

Provisional data indicates that this signal was not regarded to be a problem.

In practice, the plane responded to this sudden change as though it was at an altitude of just a few meters above the Polderbaan and engine power was reduced.

It seems that the automatic system -- with its engines at reduced power -- assumed it was in the final stages of the flight.

As a result, the aircraft lost speed.

Initially the crew did not react to the issues at hand.

As a result of the deceleration, the aircraft's speed was reduced to minimum flying speed (stalling situation) and warning signals (the steering column buzzes at an altitude of 150 metres) were given.

The black box shows that full power was then applied immediately. However, this was too late to recover the flight, the aircraft was too low and, consequently, the
Boeing crashed 1 kilometre short of the runway.

The black box -- which can register 25 hours of flying time and which, in this case, covered 8 flights -- showed that this problem had occurred twice previously in a similar situation, before landing.

The aircraft initially hit the ground with its tail and then the undercarriage followed.

The forward speed was about 175 km per hour upon impact. An aircraft of this weight should normally have a speed of 260 km per hour for landing.

The aircraft came to a rapid halt (after about 150 m) as a result of the arable land being made up of boggy clay.

The braking caused by the ground meant that the aircraft broke into two pieces; the tail broke off and the aircraft’s hull ruptured at business class.

The landing gear broke off, in accordance with its design.

This also applied to the two engines.

The full power and the sudden braking resulted in both engines continuing forwards for a further 250 meters.

The report goes on to note that the Board's investigation "will now focus fully on the workings of the radio altimeters and the connection to the automatic throttle (automatic steering system)."

Separately, the Dutch Safety Board announced that it has issued a warning to Boeing as a result of the initial findings of the Turkish Airlines accident investigation. Boeing, in turn, has given notice that a warning will be issued to all users of this type of plane to make them aware of this possible risk.

RELATED: Click here to view all posts about THY Flt 1951 on Aircrew Buzz.

Turkish Airlines identifies crew members who died in Flight TK 1951 accident

Three pilots and one flight attendant were among the nine fatalities in the crash of Turkish Airlines Flight TK 1951 at Amsterdam on February 25, 2009.  Turkish Airlines has officially identified the crew members who perished in the accident, as follows:

• Hasan Tahsin ARISAN - Pilot
• Olgay ÖZGÜR - Pilot
• Murat SEZER - Pilot
• Ulvi Murat ESKİN - Flight Attendant

Condolences to the families, flying partners, and friends of these Turkish Airlines crew members.

RELATED: Click here to view all posts about THY Flt 1951 on Aircrew Buzz.

Boeing employees among casualties in Turkish Airlines accident at Amsterdam

A short time ago, Boeing released the following statement to the media:

Boeing today received confirmation from the U.S. State Department that two Boeing employees have been identified as among the fatalities from this week's Turkish Airlines Flight 1951 accident in Amsterdam. Boeing extends its deepest condolences to their families, friends and colleagues. A third Boeing employee on Flight 1951 sustained injuries and remains hospitalized. The company is awaiting official notification about the condition of the fourth employee on the flight. Boeing remains committed to supporting the families of our employees through this very difficult time. Given the pending information, and at the request of some of the affected families, the specific condition of each employee on the airplane isn't being released by Boeing at this time.

"This is a very sad day for our company," Chairman, President and CEO Jim McNerney said. "Our thoughts and prayers are with our colleagues' families, friends and co-workers and with the families of everyone who was on the flight."

UPDATE Feb. 27, 2009: Today Boeing confirmed that a third employee who was a passenger on Flight TK 1951 has died. The company also named all four Boeing employees who were on board the accident aircraft:

...With the consent of the affected families, Boeing confirms the names and conditions of the four Boeing employees on Flight 1951. Three employees - Ronald A. Richey of Duvall, Wash., John Salman of Kent, Wash., and Ricky E. Wilson of Clinton, Wash. - died in the crash. One employee - Michael T. Hemmer of Federal Way, Wash. - was among the injured and remains hospitalized.

Condolences to the families, colleagues and friends of those who lost their lives in the accident. Best wishes to Mr. Hemmer for a speedy and complete recovery from his injuries.

Related:  Turkish Airlines Boeing 737-800 accident near Schiphol Airport, Amsterdam - AircrewBuzz.com, Feb. 25, 2009

Turkish Airlines Boeing 737-800 accident near Schiphol Airport, Amsterdam

A Turkish Airlines (THY) Boeing 737-800 aircraft (registration T-CJGE) crashed while on approach to Amsterdam's Schiphol Airport this morning, February 25, 2009. THY Flight TK 1951 was arriving at Amsterdam on a scheduled passenger flight from Istanbul at the time of the accident. According to information provided by the airline, there were seven crew members and 127 passengers on board at the time of the accident.

Turkish Airlines confirms nine fatalities and 50 injured, although several news reports, quoting Dutch officials, have said approximately 80 were injured. Three crew members are said to be among the fatalities.

At the time of the accident, the aircraft was on final approach to runway 18R at Schiphol. It impacted an agricultural field approximately a mile short of the runway threshold. Eyewitnesses claimed that the aircraft hit tail first, but this has not been officially confirmed. News photos of the accident scene do, however, show very significant damage to the empennage. The fuselage of the aircraft reportedly split into three sections. There was no fire.

The Dutch Safety Board has confirmed that both the Cockpit Voice Recorder and the Flight Data Recorder have been recovered from the accident aircraft.

A list of the names of the crew and passengers on Flight TK 1951 has been made available on the Turkish Airlines website.

More information about this accident will be posted on Aircrew Buzz as it becomes available.

[Photo Source]

UPDATE Feb. 26, 2009: Aviation news website FlightGlobal.com, quoting investigators from the Dutch Safety Board, is reporting that "none of the three cockpit personnel survived the accident." They were described as two pilots and an 'apprentice'.

Also reported: that approximately 10 minutes before impact, Dutch controllers instructed the 737 to proceed to the SPY navaid, around 12nm (22km) northeast of the runway and descend to 4,000ft ahead of an instrument landing system approach."

Approximately three minutes before the crash, "controllers told the crew to make a left turn, heading 210°, and cleared the flight for the approach to 18R, before instructing the pilots to contact the Schiphol tower frequency."

...the investigators have noted the apparent "very low forward speed" of the aircraft, and the fact that there are "hardly any tracks" in the field where the jet came to rest. The aircraft appears to have "hit with the tail" and left a "very short trail" of debris.

The number of those injured now stands at 86, with six of those in critical condition.

Related:

• Boeing employees among casualties in Turkish Airlines accident at Amsterdam - Feb. 26, 2009
• Turkish Airlines identifies crew members who died in Flight TK 1951 accident - Feb. 27, 2009
• Dutch Safety Board's preliminary report on the Turkish Airlines crash at Amsterdam - Mar. 4, 2009
• Boeing issues warning to B-737 operators, due to accident investigation findings - Mar. 4, 2009

Click here to view all posts about THY Flt 1951 on Aircrew Buzz.