Page:CAB Accident Report, TWA Flight 891.pdf/49

 -49- plane a speed of about 170 knots I.A.S. along its flight path and a climblng speed of about BOO-1,000 ft. /n.

The aforementioned study of the path of fall shows that its results are not completely in conflict With a possible disintegration of the aircraft at a height of 11,000 - 12,000 feet and a speed of about 170 knots I.A.S.

However, as 1t has already been pelnted out, other combinations of speed and height are Just as possflale (see par. 1.1.11.2).

Huh Hypotheses regarding the causes of the explosion

The possible causes of the igniting of the gasoline vapors in tank No. 7 and consequently of the exploding of tanks No. 7 and 6 1n the manner described in par. 111.0, paints a, b and 0, may be clas31f1ed into two mam groups, namely:

(a) Structural failure due to aerodynamic stresses of any klnd (turbulence, excesswe maneuver loads, etc.), ensuing explosmn of the fuel tanks and, finally, dialntegration of the aircraft;

(‘0) Explosmn of the fuel tanks, caused directly or indirectly by:

(l) faulty operation and fire 1n the engines; (a) fires of a different nature; (3) breakdowns and malfunctionmlg of the flight instruments and controls 1n enerals 04) foreign bodies of any kind striking the aircraft; %5) sabotage; (6) electric discharges from the atmOSpheI-e, and consequent chaintegratlon of the aircraft.

These hypotheses are discussed below

lh.h.1 gtmctural failures due to stresses, ensuing emlosion 1n the fuel tanks and fmal disintegration of the aircraft

0n the strength of the technical data mentioned in par. 11.3.6, a study was made of the various conditions which might substan- tiate the hypothesis of structural failure as the primary cause of the crash. The inquiry was limited to the wing because, as gathered from par. 11.2.3J4, the breaking away of the wing preceded all other ‘orealcages that took place as the plane crashed to the ground.

The con51derations and deductions set forth hereunder are valid only if we assume that, at the beginning of its last flight, the aircraft was 1n :1 normal condition as regards care and maintenance and that, in the courSe of previous operations; it had not been subjected to stresses or deterioration of such a nature as to constitute a substantial impairment of its sturdiness and structural soundness. Actually, the information assembled in this connection and the examination of the wreckage attest to the fact that, at the beginning of its last