Cessna 177 Series Aeroplanes
AD/CESSNA 177/29
Amdt 1
Seat Adjustment Mechanism 9/88
Applicability: | Model | Serial Number |
| 177, 177A, 177B, 177RG | All |
| F177RG | All |
Requirement: | Part 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.
Overview
The Cessna 177 Series Aeroplanes AD/CESSNA 177/29 Amendment 1, introduced in 1988, addresses significant safety concerns associated with seat adjustment mechanisms in certain Cessna 177 series aircraft. These safety concerns included instances of seat adjustment failures that had resulted in accidents. The legislation was enacted by the Commonwealth of Australia under the Civil Aviation Regulations 1998, specifically targeting Part 39 - 105 of the Civil Aviation Safety Authority’s Schedule of Airworthiness Directives. The primary policy objective was to mitigate the risk of accidents by mandating rigorous inspections and, where necessary, modifications to the seat adjustment mechanisms to ensure continued airworthiness and safety of the aircraft. The directive requires both detailed inspections of various components, including seat tracks, rails, rollers, and springs, and specific modifications to seat travel limits, depending on the aircraft's service hours. Compliance with these requirements is crucial to prevent further incidents related to seat adjustment failures.
Scope and Application
This legislative instrument applies to the seat adjustment mechanisms of specific models of Cessna 177 Series Aeroplanes, namely the 177, 177A, 177B, and 177RG, across all serial numbers. The primary objective of the Airworthiness Directive (AD) is to ensure the safety and airworthiness of these aircraft by addressing potential defects in the seat adjustment mechanisms. The geographic and jurisdictional reach of this legislation is national, falling under the purview of the Commonwealth of Australia and enforced by the Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998. The AD mandates specific inspections and repairs to be performed on the seat tracks, pins, rollers, housing, and springs to prevent mechanical failures that could lead to accidents. Compliance with these requirements is mandatory for all aircraft fitting the specified models, with particular timelines for inspections based on the aircraft’s service hours as of a certain date. Temporary modifications to limit seat travel are also permitted under specific conditions until certain components are replaced or by a particular deadline.
Key Provisions
The legislation, identified as F2006B05023, pertains specifically to the Cessna 177 Series aeroplanes, and it is an amendment (AD/CESSNA 177/29Amdt 1) to the Airworthiness Directives. The primary focus of this directive is on the seat adjustment mechanism of these aircraft models, which include the 177, 177A, 177B, and 177RG. This directive is applicable to all serial numbers of the 177RG model. The main operative sections of this directive, as outlined in Part 1, require a thorough inspection and maintenance of the seat tracks, seat rails, rollers, washers, and associated mechanisms to ensure they meet specified wear and engagement criteria.
Section 1 of the directive mandates that each hole in the seat track(s) must be measured for excessive wear, with any wear dimension exceeding 10.67mm (0.42") but not more than 3.81mm (0.15") necessitating the replacement of the seat track before further flight. Additionally, the seat rail holes must be visually inspected for dirt and debris that could hinder the engagement of the seat pins, which must be removed before flight. The depth of engagement for each seat pin must be measured and, if less than 3.81mm (0.15"), the necessary components must be replaced or repaired to meet this engagement criterion. Seat rollers must be checked for flat spots, and any worn rollers or washers must be replaced. The wall thickness of the roller housing and the tang must be measured, with replacement of the roller housing required if the tang thickness is less than half the housing thickness. The springs that maintain the lock pins' position must also be inspected and replaced if they do not provide positive engagement. Lastly, the seat tracks must be visually inspected for cracks, with any cracks exceeding specified limits necessitating the replacement of the affected seat rails.
The obligations imposed by this directive require aircraft operators to comply with the specified inspection and maintenance procedures. These obligations include the replacement or repair of components as necessary to meet the criteria set out in the directive. Compliance with these obligations is critical to ensuring the continued airworthiness of the aircraft. The directive also stipulates specific timelines for compliance, requiring inspections and necessary actions to be completed before further flight, and outlines alternative compliance options pending the availability of replacement parts.
The consequences for non-compliance with this directive are severe, as the seat adjustment mechanism has been linked to a history of failures and accidents. While specific penalties are not detailed in the directive, non-compliance could result in serious safety risks, and operators could face regulatory actions, including grounding of the aircraft until compliance is achieved. The directive emphasizes the importance of adhering to the specified inspection and maintenance procedures to prevent accidents and ensure the safety of passengers and crew.