AD/CESSNA 170/47 Amdt 1 - Crankcase Breather Tube and Oil Seal
CESSNA 170B · Airworthiness Directives
Overview
This document is an Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority of Australia, specifically addressing the Cessna 170, 172, and 175 series aeroplanes. The directive focuses on the crankcase breather tube and oil seal, aiming to mitigate the risk of rapid engine oil loss due to ice obstruction. It outlines inspection and modification requirements for affected aircraft models fitted with Lycoming O-320 or O-360 series engines. Compliance is mandated within a specified timeframe, ensuring that all relevant aircraft maintain airworthiness and operational safety.
- All Cessna 170, 172, and 175 series aircraft with Lycoming O-320 or O-360 engines are affected.
- Inspect the engine crankcase breather for an alternate air outlet as per Figure 1.
- If no alternate outlet exists, inspect and secure the crankcase to crankshaft seal.
- Drill the breather tube to include an alternate air outlet if necessary.
- Compliance is required within 100 hours of service after June 30, 1982.
Document
Source
Originally published by services.casa.gov.au. Sprinkle hosts a reference copy with an added summary, specifications and searchable full text.
Document details
- Type
- Airworthiness Directives
- Year
- 1986
- Pages
- 2
- File size
- 62 KB
- Publisher
- services.casa.gov.au
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In this document
Applicability
The directive applies to all models in the Cessna 170 and 172 series, as well as the Cessna 175 series, including variants 175A, 175B, and 175C, along with R172D and R172E models equipped with Lycoming O-320 or O-360 engines.
Requirement
To reduce the risk of engine oil loss due to ice obstruction, the directive requires a visual examination of the engine crankcase breather. If an alternate air outlet is not present, specific actions must be taken, including inspecting the crankcase to crankshaft seal and modifying the breather tube.
Compliance
Compliance with the directive is required within 100 hours of service after June 30, 1982, unless the actions have already been completed.
Background
The directive has been amended to address concerns regarding the proximity of the breather to the exhaust outlet. Changes in the exhaust system design necessitate modifications to the breather to prevent freezing, regardless of its current position.
Safety notes
- Failure to comply with this directive may result in rapid loss of engine oil, leading to engine failure.
Full document text
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes AD/CESSNA 170/47 Amdt 1 Crankcase Breather Tube and Oil Seal 4/86 Applicability: All models 170A, 170B, 172, 172A to 172P, 175, 175A, 175B, 175C, R172D and R172E fitted with Lycoming 0-320 series or 0-360 series engines. Requirement: To reduce the possibility of rapid loss of engine oil caused by ice obstruction of the engine crankcase breather, accomplish the following: 1. Visually examine the engine crankcase breather to determine if an alternate air outlet is drilled or cut in the tube as shown in Figure 1. If any of these provisions exist, make an appropriate entry in the aircraft maintenance records. No further action is necessary. 2. If the hole or cutout shown in Figure 1 is not in the engine crankcase breather tube: (a) Inspect the crankcase to crankshaft seal and ensure that the seal is secure. (This seal is located behind the starter ring gear in the forwardmost part of the crankcase). Reinstall or replace this seal if it is not flush with the forward face of the crankcase. (b) Drill the engine crankcase breather tube line to include an alternate air outlet as shown in Figure 1. Compliance: Unless already accomplished, within 100 hours time in service after 30 June 1982. Background: This AD has been amended to clarify the situation where the breather is still in close proximity to the exhaust outlet. Although this may currently prevent the breather from freezing, the exhaust system has been redesigned and the outlet moved to the opposite side. The original exhaust system is no longer available, and if a new exhaust is fitted the breather will then be unprotected. Therefore all breathers should be modified regardless of position. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES
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