To: Nick Lappos
Quote:
“As far as Lu's pronouncements, the score is about 1,257: 1 against Lu, since the Boeing 777 and Airbus systems were certified by very stringent governments as meeting the one in a billion chance of catastrophic failure. It is not worth debating Lu, I will not bother, but I'll wage the certificate of Airworthiness for the Boeing 777 can probably trump any post Lu types out”.
It seems that you are using your position of prominence on this forum to belittle any thing that I say. Well in this case you are totally wrong. You make a simple caustic statement about how many words I will use in responding to your comments above. I could use more if I addressed the explosion of a 737 in Manchester, England or the loss of three 737s due to a rudder malfunction. All of these crashes were due to inadequate testing and or analysis yet these aircraft had a systems failure requirement of 1 10 9.
The Boeing 777 as well as all of the Airbus aircraft were designed to have a system catastrophic failure rate of 1 10 9. This is not the catastrophic failure rate for the aircraft. Considering the total number of critical systems on a complex commercial aircraft and using Boolean Algebra it can be shown that most commercial aircraft have a potential for catastrophic loss of the aircraft somewhere around 10 7 or thereabouts. This also holds true for the 767 and the 737 and most other commercial aircraft. On the 767 they had two incidents where they lost all electrics and they had to navigate and land using the RAT. The total loss of electrics was I believe not to occur more frequently than 1 10 9. The FAA requires that the manufacturers prove their ability to meet this requirement by analysis or test. Since it is much cheaper to perform an analysis the manufacturer in some cases takes the easier route. A case in point. Boeing had to prove the low probability of a deployment in flight of a thrust reverser. On paper the frequency of occurrence of an uncommanded deployment was well below the 1 10-9 requirement so Boeing opted out of performing a test because it was too dangerous. So, they performed a computer analysis, which indicated that the uncommanded deployment was survivable. This satisfied the FAA however; Nikki Lauda proved them wrong.
On the A310 the flaps and slats are not grounded to the airframe and under certain conditions a lightning attachment could cause the wing to blow off. On the same aircraft they experienced during systems test that an internal crack in a power control unit could cause an uncommanded movement of the flaps or slats which were mandated to never occur more than one time in 10 9 flight hours. A change was made but the change will only delay the occurrence of uncommanded movement. Airbus Industrie was not notified of this problem although it was required in the design spec. The same was true for the ungrounded secondary control system. The flap system was inadequately tested on the A 310 and an FMECA was never performed on the flap slat computer. On the first revenue flight from Germany to Egypt an A 310 landed and could not retract the flaps. No amount of troubleshooting could discover the cause. The aircraft had to return to Frankfurt with the flaps fully deployed. Upon its’ return they could not isolate the problem because the flap slat computer could not recognize that a problem existed.
To sum it all up I challenge you to identify any commercial aircraft that has or could meet the 1 10 9 requirement based on the accident record for the fleet. Granted the 777 has not suffered a catastrophic failure but remember these words. Fate is the hunter.
You don’t have to look any further than your S 76. How many blades were lost due to a design error and what were the hours on the fleet at the time of the occurrences? The blades had the same requirement of one catastrophic failure in 10 9 flight hours for the fleet.
