General Electric CF6

DayAfter a écrit:Bonsoir à tous,

Merci à Maury d’avoir ouvert le sujet.
Merci Sevrien pour la remarque.

Concernant le CF6 l’histoire rejoint l’actualité.

On voit sur le 1^er AD proposé par Maury en lecture que des problèmes ont migré du CF6-50 au CF6-80C.

A mon avis, l’histoire reste l’histoire, qu'il s'agisse d'avions ou de moteurs, même si le rapport du NTSB cité est encore jeune.

Je propose de laisser Maury poursuivre ici même et je crois qu’il ne nous en voudra pas, au contraire, si nous piochons quelques parties des posts du sujet qu’il a ouvert pour alimenter l’actualité, hélas répétitive autant que variée des déboires du GE CF-6.

Pour faire court, mal fichu au départ (design flaw) mal fichu à l’arrivée : mais l’arrivée, c’est quand ? :|

Seulement mon opinion.

Maury a écrit:Development

......The NTSB issued warnings regarding the cracking of the high pressure compressor in 2000 and failure of the low pressure turbine rotor disks in 2010.

Maury a écrit:Variants

CF6-6
...........
A complete disintegration of a CF6-6 fan assembly resulted in the loss of [Vous devez être inscrit et connecté pour voir ce lien] of [Vous devez être inscrit et connecté pour voir ce lien] over [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] in [Vous devez être inscrit et connecté pour voir ce lien].The failure of a CF6-6 was the primary cause of the [Vous devez être inscrit et connecté pour voir ce lien] USA crash of [Vous devez être inscrit et connecté pour voir ce lien] in [Vous devez être inscrit et connecté pour voir ce lien] .

• (i) les écrits du NTSB (il y a des dizaines de pages, voire, parfois, des centaines, derrière une seule ligne ou paire de lignes de constatation et / ou de recommandation du NTSB ) montrent clairement tous les facteurs et incidents 'clé', qui l'ont conduit à attribuer un blâme grave à la FAA (avec les conséquences, ... méritées ..., que nous connaissons, y inclus, notamment la surveillance rapprochée de la FAA par le NTSB, qui a dû, directement et indirectement, par délégation vers la FAA, mêttre GE -- et d'autres 'gros bras' -- sous le même genre de surveillance) .
  
• (ii) les incidents - moteurs choisis et réféléchis dans le texte cité dans le post ci-dessus, montrent bien ce que nous avions souligné sur le plan du "reporting" des incidents : le silence des acteurs sur lesdits incidents, ou la minimisation de leur gravité, qui ne voulaient pas subir leur diffusion, ou, du moins, pas promptement, ... pas dans le sillage des événements ;
  
• (iii) cet ensemble démontre le fait que le NTSB "ne lâchent pas", et, au contraire, qu'il maintient la pressions sur tous concernés, y compris lui-même.
  

• incite, hélas, bon nombre d'acteurs à poursuivre la 'politique' / "policy" du silence, de minimisation de la gravité de certains incidents,
  
• et génère une créativité dans les euphémismes, dans le but de minimiser, de faire passer le temps avant l'annonce de l'incident, et de profiter de la tendance des uns et des autres à avoir la mémoire courte.
  

• "La lignée du CF-6 de General Electric racontée sur Wikipedia de langue anglaise. Thanks ! ( en français : rien)"....
  

§ 39.13 [Amended]


2. The FAA amends § 39.13 by removing airworthiness directive (AD) 2007-12-07, Amendment 39-15085 ([Vous devez être inscrit et connecté pour voir ce lien], June 6, 2007), and adding the following new AD:Show citation box

General Electric Company: Docket No. FAA-2006-25738; Directorate Identifier 2006-NE-27-AD.

This AD applies to General Electric Company (GE) CF6-80C2B1F,
CF6-80C2B1F1,
CF6-80C2B1F2,
CF6-80C2B2F,
CF6-80C2B3F,
CF6-80C2B4F,
CF6-80C2B5F,
CF6-80C2B6F,
CF6-80C2B6FA,
CF6-80C2B7F,
and CF6-80C2B8F
turbofan engines, including engines marked on the engine data plate as CF6-80C2B7F1.

Japan Airlines International (JAL) requests that we eliminate “at the next shop visit of the engine” in the compliance section. Doing this would:Show citation box

• Then allow operators to accomplish the retrofit program on Boeing 767 series airplanes more aggressively; andShow citation box
  
• Would facilitate completing the program in the proposed 5-year compliance period, without causing aircraft on the ground (AOG) situations, due to a shortage of spare ECUs.Show citation box
  

JAL is concerned that there might be a shortage of spare ECUs that could result in grounded aircraft.

JAL provided information and data on their planned retrofit for their fleet of Boeing 767 and 747 series airplanes.Show citation box

We partially agree.

Eliminating the proposed wording would result in a less aggressive replacement program for the total population of engines.

JAL did not provide any supporting data of how this change would result in a more aggressive compliance program for engines installed on the Boeing 767 airplanes.

Our risk assessment indicates that the risk presented by this unsafe condition can be successfully managed within the current and expected parts availability. Therefore, we did not change the AD.Show citation box

In reviewing JAL's comment, we noted that our intent could be clarified.

We changed the AD to clarify that ECUs installed with previous versions of software can be installed on an engine for a period of time.Show citation box

The added paragraph in the AD discusses two possible conditions:

(1) Reverting to previous versions of software in an ECU, and

(2) versions of software installed in ECUs that are installed on an engine.

Our risk assessment indicates this change to the AD is acceptable and manages the unsafe condition.

DDtrace a écrit:Ce problème de software est à l'origine de

2 "engine flame out " en vol

4 "engine flame out" au sol

8 IFSD

Du moins, ceux rapportés.

Registration:	C-FTCA
C/n / msn:	24307/259
First flight:	1989-04-11 (8 years 5 months)
Total airframe hrs:	35672
Engines:	2 General Electric CF6-80C2B6F
Crew:	Fatalities: 0 / Occupants: 10
Passengers:	Fatalities: 0 / Occupants: 199
Total:	Fatalities: 0 / Occupants: 209
Airplane damage:	Substantial

Narrative:

Shortly after the commencement of the take-off roll from runway 18L, at about 20 knots, as the engines were close to 40-degree Celsius rated take-off thrust, there was a loud explosion and then the aircraft vibrated and yawed sharply to the left.

The take-off was rejected immediately, and within a few seconds there was a fire warning on the left engine.

The augmenting first officer, who had been sitting in the cockpit jump seat, quickly went to the aircraft cabin and visually confirmed that there was a fire in the left engine.

Meanwhile, the captain and the operating first officer carried out the emergency procedures to deal with the fire
indication.

After use of the second fire bottle, the fire warning ceased, and there was visual confirmation by the augmenting first
officer that the fire had been extinguished.

The emergency response services personnel confirmed that the fire was extinguished.

The passengers deplaned using the normal exits after the aircraft was towed to the terminal.

After the aircraft was shut down, it was noted that parts from the high-pressure compressor (HPC) had detached from the engine.

CAUSES:

"An uncontained failure of the third stage of the 3-9 HPC spool was due to the presence of an oxygen-rich segregate produced in the batch of titanium used to construct the 3-5 stages of the spool.

The segregate caused locally degraded resistance to fatigue crack initiation in the dove-tail slot bottom, an area of the spool that is subject to some of the higher design hoop stresses.

Contributing to the occurrence were the quality control decisions made at the time of manufacture of the titanium, the inability of existing in-service inspection techniques to detect crack zones, and the intolerance of the spool design for slightly degraded material."

Follow-up / safety actions:

The NTSB, based on the accident/incident and inspection record of the CF6 series of engines and also based on information gathered during this investigation, made seven recommendations.

On 06 March 1998, the NTSB issued recommendations A-98-27/-33.

Engines:	2 General Electric CF6-80C2B2
Crew:	Fatalities: 0 / Occupants: 13
Passengers:	Fatalities: 0 / Occupants: 178
Total:	Fatalities: 0 / Occupants: 191
Airplane damage:	Substantial

Narrative:

Varig Flight 886 to Lima experienced an uncontained failure of the HPC stage 3-9 spool in the No. 2 (right) General Electric CF6-80C2B2 engine during takeoff.

The flight crew reported that at a speed of about 60 knots, they heard a loud bang.

They rejected the takeoff and stopped the airplane on the runway.

The copilot opened the right-side cockpit window to look out and advised the pilot that there was a fire around the
right main landing gear.

The flight crew reported that they then attempted to taxi clear of the fire but stopped the airplane on the runway again when they realized it was the engine that was on fire and ordered an evacuation.

Although the flight crew discharged both fire bottles into the No. 2 engine nacelle, the fire continued until it was
extinguished by airport fire department personnel.


Follow-up / safety actions:

On August 9, 2000 the NTSB issued safety recommendation A-00-104:

"Immediately issue an airworthiness directive (AD) to require the expeditious removal from service of CF6-50 and -80 series engines with high pressure compressor stage 3-9 spools that are most at risk of rupturing and inspect those spools in accordance with AD 99-24-15 and engine manual instructions. (Class 1, Urgent Action)."

On August 21, the FAA then published Airworthiness Directive AD 2000-16-12, requiring "...initial ultrasonic and eddy current inspections of certain HPCR stage 3-9 spools for cracks."

Sources:
» NTSB Safety Recommendation A-00-104

Total airframe hrs:	68007
Cycles:	20390
Engines:	2 General Electric CF6-80A
Crew:	Fatalities: 0 / Occupants: 10
Passengers:	Fatalities: 0 / Occupants: 190
Total:	Fatalities: 0 / Occupants: 200
Airplane damage:	Substantial

Narrative:

While climbing through FL110, the crew heard a loud 'bang' and felt the aircraft move to the right, followed by a progressive yaw to the left.

After checking instrumentation, the failure of the left (number-one) engine was confirmed and the engine was shut down.

An emergency was declared and the aircraft returned to Brisbane.

An initial engineering examination of the left engine revealed a large rupture of the outboard core cowl and severe gouging and scoring of the outboard side of the engine strut above the cowl damage.

The leading edge flap panel above the strut was extensively damaged over approximately 40cm and the no. 2 canoe fairing behind the engine sustained debris impact and puncture damage.

Inspection of the engine core beneath the ruptured cowl revealed that the first-stage high-pressure turbine disk had failed and released a large segment of the disk rim and outer web.

The engine casing around the disk had been completely severed and the central shaft fractured between the stage-one and stage-two high-pressure turbine disks.

FINDINGS:

- The technical investigation of the failed CF6-80A stage-1 high-pressure turbine disk (s/n. MPOP-8478) found that the disk failed as a result of the initiation and growth of fatigue cracking from the rear bottom corner of a turbine blade fir tree slot.

- The disk had developed a total of three slot bottom fatigue cracks at the time of ultimate failure.

- None of the cracks were attributable to any identified erroneous tool or handling damage to the slot bottoms.

- The disk had undergone a repair operation in August-October 1998. The repair was conducted to remove fir tree slot edge nicks and other damage and included blending of the damage followed by shot-peening of the rear slot edges and other areas.

- All of the cracked fir tree slots and several other uncracked slots showed surface microstructural flow and damage that was attributable to the shot peening operation following the 1998 repair.

- The type of surface damage produced (specifically the formation of stress-raising defects known as ‘peened surface extrusion folds’) has been shown to be detrimental to the fatigue life of the affected component.

- The disk had operated for 7,838 hours and through 2,793 cycles following return to service after the August 1998 overhaul.

- The previous CF6-80C2 stage-1 HPT disk failure (September 2000) occurred 1,675 cycles after a similar blending and shot peening repair of disk slots and rear corners.

- The corrective action implemented after the September 2000 disk failure did not encompass the CF6-80A stage-1 HPT disks.

Follow-up / safety actions:

As a result of the findings of the investigation, the engine manufacturer has implemented several changes to the manufacturing and repair shot peening processes, to avoid the surface damage found on the failed disk.

Other safety action taken included revising the inspection requirements for the CF6-80A disks to include the more
thorough examination of the slot bottom and rear break-edge areas, as required for the CF6-80C series engines.

The US Federal Aviation Administration (FAA) and the Australian Civil Aviation Safety Authority (CASA) have subsequently mandated the revised requirements.

The aircraft operator, as part of its own investigation into the occurrence, has developed a series of recommendations aimed at addressing the crew communication deficiencies experienced during the return to Brisbane after the engine
failure.

Registration:	N654US
C/n / msn:	25225/375
First flight:	1991-06-05 (9 years 4 months)
Engines:	2 General Electric CF6-80C2B2
Crew:	Fatalities: 0 / Occupants: 3
Passengers:	Fatalities: 0 / Occupants: 0
Total:	Fatalities: 0 / Occupants: 3
Airplane damage:	Written off
Airplane fate:	Written off (damaged beyond repair)

Narrative:

The aircraft experienced an uncontained failure of the high pressure turbine stage 1 disk in the No. 1 engine during a high-power ground run for maintenance.

Because of a report of an in-flight loss of oil, US Airways mechanics had replaced a seal on the No. 1 engine’s integral drive generator and were performing the high-power engine run to check for any oil leakage.

For the maintenance check, the mechanics had taxied the airplane to a remote taxiway on the airport and had performed three runups for which no anomalies were noted. During the fourth excursion to high power, at around 93 percent N1 rpm, there was a loud explosion followed by a fire under the left wing of the airplane.

The mechanics shut down the engines, discharged both fire bottles into the No. 1 engine nacelle, and evacuated the airplane.

Although both fire bottles were discharged, the fire continued until it was extinguished by airport fire department personnel. The aircraft was damaged beyond repair.


Follow-up / safety actions:

The NTSB issued 4 safety recommendations regarding maintenance and inspection of the General Electric CF6-80C2 engine’s high pressure turbine stage 1 disk.