Air France

The following findings were reported:
(1) Human Factor:
Physiological Aspect - The crewmembers physical conditions (fatigue) might have contributed to their delay in perceiving the engine failure and to the inadequate reactions during the emergency.
(2) Material Factor:
a) The hydraulic pump ripple of the CF6-50E engine caused considerable vibration on the pulley support region, which worked as a dynamic source to produce cable oscillation and relative movement between cable and pulley.
b) Pulley bracket design deficiency, possibly related to the reduced contact area between cable and pulley, allowing for the wearing of these components in the presence of abrasive agents, in association with the vibration on that area, knowing that there is localized contact between both (at the same points) in an almost permanent way (93% of the engine operating time in cruise range).
c) The tests performed by the Manufacturer confirmed the existing relative movement between cable and pulley, even after the introduction of modifications.
(3) Maintenance Deficiency:
a) The use of an aluminum pulley, not authorized by the manufacturer as a substitution to the recommended phenolic pulley, made possible the formation of the abrasive agent (alumina).
b) The inadequate fixation of the pulley bracket due to the use, by the operator, of a screw of insufficient length for an additional washer, left loose the support side brace, allowing for the increase of the relative movement. already existing at that region, between cable and pulley.
(4) Flight Manual Deficiency:
a) The B747 AFM instructions allow the pilot flying to apply reverse thrust before knowing the effective transit of reversers.
b) The B747 AFM has no instruction regarding a failure of reverser deployment associated with an engine runaway forward thrust. The lack of instructions on this specific kind of abnormality, contributed to the crew not noticing that the failure had occurred.
(5) Training Requirement Deficiency:
a) The lack of simulator training requirement for this type of emergency contributed to the control loss.
(6) Crewmember Factor due to Operational Error:
a) The captain did not observe the AFM instructions about the reverse levers and manual brake use.
b) The FIE did not observe the AFM instructions about the correct engine instrument monitoring during the reverse operation.

The accident directly resulted from the uncontained explosion of a first stage high pressure turbine disk of the right hand engine. The propagation of a low cycle fatigue crack on one of the embossments of the disk rim was at the origin of the disk fracture. This cracks, which existed before, had not been detected during the inspection conducted in the operator's workshops, according to the method defined by the manufacturer and in accordance with the requirements of the airworthiness authority. The investigations showed that it was necessary, not only to reduce the intervals between the inspections of these disks and conduct two independent sequential inspections, but also to modify the design and make sure they were progressively replaced by the new type. It seems obvious that the limit life validation methods used at the time of the accident, were still insufficient, as far as the probability of non-detection of cracks was concerned.

Explosion of two grenades in the cabin after the aircraft has been hijacked.

It was determined that tires n°11 & 12 located on the right main gear burst while the aircraft was completing a 180 turn on the runway, causing the wheel to struck the ground. Initial delay in shutting down the engines and an improper deployment of fire services caused the fire to spread.

The accident was the consequence of the combination of the following factors:
- Poor crew coordination,
- The crew failed to follow the published approach procedures,
- Lack of visibility,
- High obstructions.

The exact cause of the accident could not be determined. It was suspected that the loss of control was the consequence of a spatial disorientation on part of the pilot-in-command. No official investigation report was published either by the Venezuelan Authorities or by the French Government. All official documents referring to this tragedy are classified 'secret-defense' by the French Authorities until 2029. Nevertheless, in a classified document dated August 7, 1970, the French Bureau of Investigations (BEA-Bureau Enquêtes-Accidents) asked the French government to make a contact through the diplomatic way with the Venezuelan Authorities, to establish any evidence relating to suspicious traces found on clothes and some debris, some of them coming from the left main gear. On 17 November 1970, the Central Armament Laboratory of Paris confirmed that acetone washes were carried out on certain parts such as the fuselage, the bottom floor of the landing hatch and the landing gear. On the neighboring parts of the left main gear, it has been possible to demonstrate the presence of nitrocellulose, nitroglycerine and a nitro derivative in the form of traces that could come from the decomposition of dinitrotoluene or possibly trinitrotoluene. Consequently, in a letter dated November 27, 1970, the Chief of the General Inspectorate of the French Civil Aviation confirms in an official letter that the technical analysis carried out by the various laboratories highlighted a high probability that the destruction in flight of the aircraft should be attributable to an act of malicious intent. Indeed, the chemical and metallurgical analysis showed that a powerful explosive device may have been placed in the well zone of the left main gear.

The loss of control was the consequence of an engine malfunction due to an error on part of the flight engineer who placed the main fuel selectors in a 'half-on' position which corresponded with the 'On' position in five of the DC-4 aircraft of the company.