Engine Overhaul Manual
Jabiru Aircraft
Pty Ltd
Jabiru 2200 & 3300 Aircraft Engines
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Dated : 28/10/2014
Issued By: AS
Page: 14 of 201
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2.6 Degree of Difficulty
In this manual we have used a “spanner scale” to help overhaulers approach a job. Anyone
considering undertaking a task in this manual must realistically assess themselves against this scale
and not attempt any task for which they lack knowledge or the required tools.
Table 2
– The Spanner Scale
The Spanner Scale
Translation
Simple, basic, straightforward. A careful layman, with guidance, can
achieve this.
Straightforward, but with some technical bits. Basic knowledge, care
and guidance needed.
Straightforward, but requires special tools, training and/or judgement.
Sound basic knowledge guidance and a careful approach are required.
A technical job. Take your time, double-check everything. Only for the
experienced overhauler.
A difficult job. Requires special tools, solid skills, good judgement.
Only for experts.
2.7 Manual layout
This Manual suggests that an engine overhaul will be conducted in three stages:
Disassembly
,
Inspection and assessment
, and
Assembly
. The intention is that an engine will initially be stripped and
the mandatory replacement parts will be discarded. The remaining parts will be inspected and assessed
for return to service and a single parts order will then be placed.
Final assembly can take place once all the required parts are present.
2.8 Engine life
Engine life is expressed here in cycles, with 1 cycle being nominally in the vicinity of 1,000 hours, the
actual number of hours achieved being heavily dependant on the use of correct operating and
maintenance procedures and, to a lesser degree, operating conditions.
The expected life (expressed as time between complete overhauls) of a correctly operated and
maintained Jabiru engine is 2 cycles, with a top end overhaul taking place at 1 cycle.
Various components of the engine have a service life which is determined “on condition” – that is the
overhauler must examin
e the part and make a judgement as to the part’s suitability for re-use. Other
parts are evaluated both on condition and by a fixed maximum life
– for example valves which are
replaced around 1,000 hours (See Sections 5.1, 5.2 and 5.3).
Engine life is measured via direct tachometer hour meters or “Hobbs” meters. Air switches or scaled
hour readings based on cumulative power output are not to be used to determine when overhauls or
services are due.
2.9 Complete overhaul, top end overhaul, wear tolerances
While the overall thrust of this Manual is complete overhaul, distinction must be made between a
complete overhaul and top end overhaul: the objective of a complete overhaul is to return the engine to
a condition where it can be reasonably expected to achieve 2 cycles, while the objective of a top end
overhaul is to return the top end of the engine (i.e. big ends, cylinders, pistons and cylinder heads) to a
condition where it can be reasonably expected to achieve 1 cycle to take the engine to the next
complete overhaul.
Consequentially the allowable wear tolerances for a top end overhaul, which is intended to achieve 1
cycle, will be different to the allowable wear tolerances for a complete overhaul, which is intended to
achieve 2 cycles.
