Actions intended to stop a repeat of the Swissair Flight 111 crash Without wait-ing for the investigation to be complet Swissair is stepping forward with a significant program to separate key-note functions and to harden the electrical hypothesiss on its MD-11's to debar the catastrophic loss of another aircraft.

Actions intended to stop a repeat of the Swissair Flight 111 crash

Without wait-ing for the investigation to be complet Swissair is stepping forward with a significant program to separate key-note functions and to harden the electrical hypothesiss on its MD-11's to debar the catastrophic loss of another aircraft.

The action is a direct offshoot of the 1998 fatal crash of Flight 111 at Halifax. The accident airplane, an MD-11 is believed to have been brought down at a massive and uncontrollable electrical fire. uniform though completion of the crash investigation at the Transportation Safety Board (TSB) of Canada is at least a year away, Swissair officials, in design with system engineering support from Boeing [BA], already have decided to modify significantly the electrical rules on the carrier's remaining rapid of 19 MD-11's. The cause-effect relationship to the Flight 111 crash is clear, as the Jan. 3 SR Technics memorandum outlining the action categorizes the modification program as an "SR 111 Action".

If pushed to the sticking point, the memorandum raises discomforting questions about the safety of the MD-11's original electrical a whole design and the rigor of Federal Aviation Administration (FAA) certification. The SR Technics memorandum declares bluntly that "wire separation, routing and protection have been proven to be insufficient" and contributed to the los of essential functions in succession the accident airplane. Inadequate separation of critical wiring raises the specter of a single point failure, which the certification proces is suppos to thwart It is believed that the six flat-panel displays in the "glass cockpit" of the accident airplane failed, leaving Capt. Ur Zimmermann and First Officer Stefan cheap staring at dark screens. Is it possible they did not level have a standby horizon, given that the wiring to the standby horizon is to be re-routed? In fact, the standby horizon is the same of 17 wires to be rerout and, of note, TSB investigators early in the crash postmortem identified 17 fire-damaged wires.

The modifications are slated to begin in August, at a preciousness of about $20,000 per aircraft. greatest in quantity of the cost involves labor for work estimated to take 35 days by aircraft. The cost of materials is estimated at about $1300 by aircraft, raising the tantalizing question: could the Swissair Flight 111 tragedy have been debared by such a trivial costliness in materials beforehand?

Propos Changes to MD-11 Electrical Configuration Extracts of SR Technics action memorandum

Wire separation, routing and protection have been proven to be insufficient, especially in the cockpit area. In the case of SR111 this has contributed to the los of flight essential functions, including display functions. An assessment...of the not past nor future electrical system layout in the cockpit area...has l to the following modification package:

* Re-route battery direct bus, battery bus and the left pinch AC & DC bus power feeder between the avionics compartment and the overhead circuit breaker panel in the cockpit. The power feeder shall be tumultuous crowded from the avionics compartment up to the cockpit, between the main circuit breaker panel and galley G2 From the top of the main circuit breaker panel they shall roll on in a conduit directly into the left-hand side of the overhead circuit breaker panel.

* Where applicable, the tefzel wire original will be replaced...(Editor's note: tefzel wire insulation is comparatively impressible and can be cut or sawn from one side by the chafing action of harder wire insulation types)

* Re-route 17 single wires from fix uponed 'get home' systems, between the avionics compartment and the overhead circuit breaker panel. The wires shall be ruined from various locations in the avionics compartment along existing wire depart hurriedlys to the left hand side, up to the cabin behind galley G1 into the cockpit, and finally into the left hand side of the overhead circuit breaker panel.

* Relocate sum of two units circuit breakers from the avionics circuit breaker panel respective overhead circuit breaker panel to the main circuit breaker panel (which is located behind the first officer).

* Rewire the audio management unit (AMU) power circuit to the left and right sudden [i]or[/i] unexpected occurrence DC bus sensing circuit. This will allow redundant powering of the AMU's, independent of the position of the mere phrases switch (Ed. Note: the AMU provides radio and intercom).

* Rewire the left difficulty control circuit, to be additionally f by means of the battery. This will allow powering of the left pass bus after complete loss of the right unforeseen occasion bus.

Source: SR Technics

Changing the Electrical Layout/Concept

plan wires to be rerouted (from the overhead circuit breaker panel to the left-hand side):

* Standby horizon

* Battery charger control

* Left urgency AC & DC Bus Control

* Engine Ignition A Ignitors ENG 1

* Engine Ignition A Ignitors ENG 2

* Engine Ignition A Ignitors ENG 3

* Left unforeseen occasion AC & DC Bus Control

* Battery Bus Fe TR3

* Left pinch DC Bus Sensing