Check Of Compression - Rotax 912 Series Maintenance Manual

2.5)

Check of compression

See fig. 3.
WARNING: Ignition switch for both ignition circuit in „OFF" position.
Differential pressure test procedure equipment.
CAUTION: In add to standard practical for this you will need the following
PROCEDURE:
Bring engine to operating temperature. Remove respective spark plug and install
adaptor (1) in spark plug hole and connect line with the two pressure gauges and
intermediate orifice (2). Hold piston on TDC with propeller. Now put constant
pressure of approx. 6 bar (approx. 80 psi) on the line (3) and take readings on
pressure gauges (4) and (5). The maximum allowable pressure drop is 25 %, e.g.
from 6 to 4,5 bar (87 psi to 65 psi).
If compression is below the limit, the whole engine must be inspected, repaired
or overhauled in accordance with the ROTAX
thiness.
- Detailed inspection of affected engine components. In the course of fault-
1
Zyl. Kopf /
cyl. head
Successively take readings on all four cylinders and compare results. Individual
readings of the cylinders must not differ by more than 2 bar (29 psi).
If readings are below 6 bar (90 psi), the whole engine must be inspected,
repaired or overhauled in accordance with the ROTAX
ued airworthiness.
- Detailed inspection of affected engine components.
Effectivity: 912 Series
AIRCRAFT ENGINES
MAINTENANCE MANUAL
equipment: Compressed air supply of approx. 6 bar (87 psi), two
pressure gauges, an orifice (2) of 1 mm (.04 in) dia. and 3 mm (.12
in) length and an adaptor to connect line to tapped spark plug
hole.
5
bar bar
Ø 1mm (0,039 in.)
L = 3 mm (0,12 in.)
2
fig. 3
00156
instructions for continued airwor-
®
tracing a compression check may be per-
4
formed too:
A compression tester is required to check
compression. The compression should
be between 9 and 12 bar (130 and 174
psi).
PROCEDURE:
Bring engine to operation temperature
3
(engine oil temperature between 30 to
70°C (90 - 160°F)).
Remove top spark plug and press com-
pression tester against plug tap hole and
set engine with open throttle into rotation
by activating starter until maximum pres-
sure is reached.
instructions for contin-
®
12-00-00
page 9
Rev. 1, Jan. 01/2002