China Airlines flight CI611, a Boeing 747-200, crashed into the sea following an in-flight breakup off the Penghu islands, Taiwan, killing all 225 occupants. Boeing 747-209B B-18255 was scheduled to fly flight CI611 Taipei-Hong Kong during its last day in service for China Airlines before being sold to Orient Thai Airlines. Weather conditions at Taipei that afternoon where fine: sunny weather, a temperature of 28deg C and easterly winds at a speed of 9 knots. At 14:38 Taipei Delivery cleared Flight 611 to Hong Kong: “Dynasty six one one cleared to Hong Kong Airport via Jessy one departure after Jessy direct to Chali Makung alpha one maintain flight level two six zero expect flight level three five zero at Makung squawk two six six one”. The gate closed around 14:50, ten minutes after the scheduled departure time and the crew requested ground start and pushback from stand B2. At 14:57 pushback was completed and the aircraft taxied to runway 06. Ten minutes later the aircraft had taxied into position and was cleared for take off. While climbing through 1600 feet the crew contacted Taipei Approach and received clearance to climb to and maintain FL260 and proceed direct to Chali. At 15.16, while climbing through FL187, Dynasty 611 contacted Taipei Control. The Flight was cleared to climb and maintain FL350 and proceed from Chali direct to Kadlo. Some 13 minutes later, while approaching 35,000 feet, the aircraft disappeared off radar screens. Wreckage and bodies were found at sea, about 45 km Northeast off the Penghu islands. The flight probably disintegrated at high altitude since other debris was found near Changhua, about 45 kilometers from the crash site. FINDINGS RELATED TO PROBABLE CAUSES: 1. Based on the recordings of CVR and FDR, radar data, the dado panel open-close positions, the wreckage distribution, and the wreckage examinations, the in-flight breakup of CI611, as it approached its cruising altitude, was highly likely due to the structural failure in the aft lower lobe section of the fuselage. 2. In February 7 1980, the accident aircraft suffered a tail strike occurrence in Hong Kong. The aircraft was ferried back to Taiwan on the same day un-pressurized and a temporary repair was conducted the day after. A permanent repair was conducted on May 23 through 26, 1980. 3. The permanent repair of the tail strike was not accomplished in accordance with the Boeing SRM, in that the area of damaged skin in Section 46 was not removed (trimmed) and the repair doubler did not extend sufficiently beyond the entire damaged area to restore the structural strength. 4. Evidence of fatigue damage was found in the lower aft fuselage centered about STA 2100, between stringers S-48L and S-49L, under the repair doubler near its edge and outside the outer row of securing rivets. Multiple Site Damage (MSD), including a 15.1-inch through thickness main fatigue crack and some small fatigue cracks were confirmed. The 15.1-inch crack and most of the MSD cracks initiated from the scratching damage associated with the 1980 tail strike incident. 5. Residual strength analysis indicated that the main fatigue crack in combination with the Multiple Site Damage (MSD) were of sufficient magnitude and distribution to facilitate the local linking of the fatigue cracks so as to produce a continuous crack within a two-bay region (40 inches). Analysis further indicated that during the application of normal operational loads the residual strength of the fuselage would be compromised with a continuous crack of 58 inches or longer length. Although the ASC could not determine the length of cracking prior to the accident flight, the ASC believes that the extent of hoop-wise fretting marks found on the doubler, and the regularly spaced marks and deformed cladding found on the fracture surface suggest that a continuous crack of at least 71 inches in length, a crack length considered long enough to cause structural separation of the fuselage, was present before the in-flight breakup of the aircraft. 6. Maintenance inspection of B-18255 did not detect the ineffective 1980 structural repair and the fatigue cracks that were developing under the repair doubler. However, the time that the fatigue cracks propagated through the skin thickness could not be determined.