Wing Centreline Splice Joint 6/2003
Applicability: Models AT-300, AT-301, AT-302, and AT-400A aircraft, all serial numbers, that
have aluminium spar caps; Models AT-400 aircraft, serial numbers 400-0244 through 400-0415, that have aluminium spar caps; Models AT-300 and AT-301 aircraft, all serial numbers, that have aluminium spar caps and are, or have been converted to turbine power.
Accomplish either the Requirement 1 spar lower cap replacement or the Requirement...
2 spar lower cap repetitive inspections.
Repetitively inspect the wing lower spar caps instead of replacement...
Replace the wing spar lower caps before further flight after whichever occurs first:
(i) The date of the scheduled replacement;
(ii) Cracks are found during any inspection allowed by Requirement 2 of this Directive; or,
(iii) Upon accumulating 600 hours time in service after the initial inspection
accomplished in accordance with Requirement 2.b. of this Directive.
This Amendment becomes effective on 7 May 2003.
Background: The FAA received a report of an in- flight separation of a wing from a Model AT-400A aircraft. Investigation revealed that fatigue caused the lower aluminium spar cap to fail across the 3/8- inch hole, 6.5 inches outboard of the fuselage centreline in the centre splice connection. The actions specified in this Directive are intended to detect and correct cracks in the centreline splice joint. Undetected cracks could eventually result in in- flight separation of the wing. Amendment 1 is issued in response to a new FAA AD which further reduces the mandatory wing spar lower cap replacement times; in response to inspection results from FAA AD 2002-13-02.
The original issue of this Airworthiness Directive became effective on 24 July 2002.

FMI: www.casa.gov.au/avreg/aircraft/ad/ADfiles/Under/at/at-022.pdf