Page:CAB Accident Report, TWA Flight 891.pdf/46

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Into the right sectlon of tank No. 7 are 1nstalled the follomng mam accessorles: electrlc level—mdlcator, vent valve, and 3—way selector crossefeed valve.

Therefore, unlike the other an: tanks, Wthh have only one vent valve each, tank No. 7 has two vent valves for the escape of gasoline vapors.

The two vents are syvmnetrlcal. Specﬁlcally, they begm at

the right and left bulkheads of tank No. 7 and end at two

vent outlets Sltuated one On the tralllng edge of the rlght

mng and the other on the tra111ng edge of the left mng,

behlnd englnes No. it and No. l, respectlvely. To these vent outlets are connected also the vent plpes of tanks Nos. 6, 3 and h (outlet to the right) and of tanks Nos. 5, 2 and 1 (outlet

to the left). The outlets are not equlpped mth antl-flame ware gauze.

From what 15 said 1n par. 11.2.3.1 and taklng 1nto account the structural features, descrlbed above, of tanks Nos. 7 and 6, 1t 15 deduced that:

(a) An explosion took place 1n the rlght sectlon of tank No. 7;

(b) The exp10510n cauSed the fuel mtake plpe (P.N. 1178301) of tank No. 7, Wthh runs through tank No. 6, to spllt.

(c) The spllttmg of thlS fuel 1ntake plpe (PJ‘I. hTBBOl)

lumedlately caused an overpressure, or another explosion, in tank No. 6.

Nature of the agglosion

The plane had taken off from the Malpensa alrport mth the follovnng fuel supply:

Tanks 1, 2, 3 and h 625 gallons each (capacity of eacl‘T'tank 1, 3143—1386 gallons)

Central tank No. 7 22 gallons, excluding the Hotel capaclty 1,6111; non-usable re51dual quantlty gallons) (11 gallons)

Tanks Nos. 5 and 6 0 gallons each, excludlng the icapac1ty 1, 570 gallons non-usable realdual quantzttyr

each) (5 gallons)

At the tlme of the crash the fuel-supply condltlons had changed as follows:

Tanks Nos. 1, 2, 3 and h 550 gallons each