PPRuNe Forums - View Single Post - If your aircraft has wheels don't for get to check the brakes are off before landing
Old 23rd Aug 2009, 19:51
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IGh
 
Join Date: May 2007
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Various ways to x-wire sensors for Anti-skid

Two slots above "onetrack" offers an observation that relates to earlier exemplars, on other models, where mechanics had x-wired Anti-Skid sensors/control:
"... appears that the only the left main gear was fully locked, but the right main gear tyres were shredded ... the left main wheels appear ... destroyed ... locked, but the right main wheels appear to have been rotating freely?..."
There are several examples of x-wired Anti-Skid connectors, but the results differ, depending on gear design.

I recall once during B767 testing (with multiple changes of wheel/brakes/tires), that a routine Wheel/Brake change resulted in the LEFT Twin-Tandem MLG, Fwd Wheels RELEASED, while AFT Tires were both failed, only discovered during the next landing roll-out. Simple err, the Left MLG ELECTRICAL cannon plugs were REVERSED (Fore/Aft).

For the A320, the similar errs result in a different effect (failing Anti-Skid to differing Wheel-Brakes):
... CHI08IA026 ... October 09, 2007 in Chicago, IL
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20071023X01635&key=1

... DCA08IA044 ... February 25, 2008 ... Jackson, WY
http://www.ntsb.gov/ntsb/brief.asp?ev_id=20080312X00305&key=1
Here's the description of failures and cause for the 9Oct07 case:
CHI08IA026
 ... UNITED ... October 09, 2007 in Chicago... A320-232 ... N431UA ...
... left main landing gear inboard and outboard anti skid tachometers wiring were reversed during scheduled maintenance at a vendor. During landing, the inboard left main landing gear's wheels went to a high braking level and the outboard wheel did not apply braking. ... the built in test equipment test ... not check for cross-wired tachometers. ...

... the probable cause(s)...:
The misrouted and reversed antiskid wiring by vendor maintenance personnel leading to the runway excursion. Contributing ... vendor's maintenance personnel not understand ... procedures in the dual tachometer replacement, and the operator's maintenance procedures being unclear to the maintenance personnel.
Interesting that the mx-err (CONTRACT Mx x-wire) remained a passive, hidden failure, during the following 68 airline flights:
"... released from TIMCO on September 23 and subsequently flew 68 cycles...."
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