AD/CESSNA 177/29 Amdt 1 - Seat Adjustment Mechanism

Cessna 177 Series Aeroplanes

AD/CESSNA 177/29

Amdt 1

Seat Adjustment Mechanism 9/88

1. Measure each hole in the seat track(s) for excessive wear. If the wear dimension across any hole exceeds 10.67mm (0.42") to a maximum depth of 3.81mm (0.15"), replace the seat track prior to further flight.

Figure 1 - SECTION OF SEAT TRACK SHOWING HOLE WEAR

b.    Visually inspect the seat rail holes for dirt and any debris which may preclude engagement of the seat pin(s). Remove any such material prior to further flight.

c.    Lift up on the forward edge of each seat to eliminate all vertical play. With the seat in this position, measure the depth of engagement of each seat pin. If the engagement of any pin is less than 3.81mm (0.15") (see Figure 2), replace or repair necessary components to achieve a seat pin engagement of 3.81mm (0.15") or greater prior to further flight.

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

FIGURE 2

d.    Visually inspect seat rollers for flat spots. Ensure all rollers and washers turn freely on their axle bolts (or bushings if installed) and move freely on the seat rails. Replace rollers having flat spots and any worn washers prior to further flight. If there is any binding between the bores of the rollers, washers, and axle bolts (or bushings if installed), remove, clean, and reinstall these parts prior to further flight.

Note: Do not lubricate rollers, washers, axle bolts or bushings as the lubrication will attract dust and other particles which can cause binding.

e.    Measure the wall thickness of the roller housing and the tang (see Figure 2). If the tang thickness has worn to less than 1/2 the housing thickness, replace the roller housing prior to further flight.

f.     Check the spring(s) that keep the lock pin(s) in position in the track holes for positive engagement action. Replace any spring which does not provide positive engagement prior to further flight.

g.    Visually inspect the seat tracks for cracks in accordance with Cessna SIL SE83-6, dated 11 March 1983. Any limitation imposed as a result of seat track cracking shall be endorsed on the Maintenance Release. Replace any seat rail exceeding the crack criteria as specified in SE83-6 with a serviceable rail prior to further flight.

Part 2:

In accordance with temporary schemes approved by the Secretary, modify seat adjustment mechanisms to permanently limit seat travel to 255mm (10") or to 153mm (6") as applicable, aft of the forward stop.

Note: FAA AD 87-20-03 R1 refers.

Compliance: A. i.  For aircraft with less than 1000 hours time in service as at 28 January 1988, prior to attaining 1100 hours time in service; or

ii.        For aircraft with more than 1000 hours time in service as at 28 January 1988, at the next inspection for Maintenance Release issue after 28 January 1988; and

iii.      Thereafter at each inspection for Maintenance Release issue.

B. Pending any component replacement necessary to fully comply with Requirement: Part 1, compliance with Requirement: Part 2 is an acceptable alternative until

30 June 1989.

Background: There has been a history of seat adjustment mechanism failure that has resulted in accidents. As there will probably be a high demand for replacement items, Part 2 of the Requirement enables continued flight. Schemes acceptable to the Secretary are available from Regional Offices.