Thu, Dec 04, 2003
AWB 27-4 Issue 1, 5 December 2003: Cessna 172, 180 and 185
Primary Flight Control Yoke Inspection
Effectivity: Cessna
Aircraft Company and Reims Aviation (Cessna) 172, 180, and 185
series aircraft as listed in the current revision of Cessna Service
Bulletin SEB01-3.
Purpose: To alert operators and maintainers to
the potential failure of the welded steel tube yoke assembly, which
can result in loss of primary pitch control of the aircraft, and to
strongly recommend compliance with Cessna Service Bulletin SEB01-3.
This SB describes an inspection procedure to detect corrosion, and
determine the serviceability of a yoke that has suffered corrosion
pitting.
Background: CASA and the
FAA have received defect reports describing extensive internal
corrosion initiated by moisture collecting inside the lower section
of the welded tubular structure. Some control yokes have suffered
structural failure due to corrosion in this zone.
The design of the control yoke in the nominated aircraft did not
have any provision to drain moisture from the lower section of the
yoke. This allowed moisture to collect inside the vertical tube of
the assembly, and initiate corrosion. In some cases the corrosion
caused a significant reduction of wall thickness of the yoke, and
resulted in failure of the lower elevator control lug.
Cessna Aircraft Company has issued instructions for an insitu
inspection of the control yoke, which requires an ultrasonic
inspection of the lower section of the yoke assembly. Yokes that
are corroded beyond the limits prescribed in SEB01-3 should be
replaced.
In addition to this, CASA has
received a defect report describing internal corrosion deposits
outside the nominated area indicated in the Cessna SB, being
significantly higher up the vertical tube of the yoke than the
shaded area shown in Figure 1 of SEB01-3.
Recommendation: CASA strongly recommends
operators and maintainers carry out the requirements of the current
revision of Cessna Service Bulletin SEB01-3, extending the zone of
eddy current inspection to match the extent of surface corrosion
detected, and incorporate the annual inspection requirements of
SEB01-3 into the aircraft maintenance program.
More News
Option Approach An approach requested and conducted by a pilot which will result in either a touch-and-go, missed approach, low approach, stop-and-go, or full stop landing. Pilots >[...]
"Emirates is already the world's largest Boeing 777 operator, and we are expanding our commitment to the program today with additional orders for 65 Boeing 777-9s. This is a long-t>[...]
(Pilot) Reported That There Was A Sudden And Violent Vibration Throughout The Airplane That Lasted Several Seconds Analysis: The pilot was returning to his home airport at an altit>[...]
“This recognition was evident during the TBMOPA Annual Convention, where owners and operators clearly expressed their satisfaction with our focus on customer service, and enc>[...]
Overhead Maneuver A series of predetermined maneuvers prescribed for aircraft (often in formation) for entry into the visual flight rules (VFR) traffic pattern and to proceed to a >[...]
ANN's Daily Aero-Term (11.19.25): Option Approach
See All