ULPOWER UL390i User manual

UL39Oi
UL39OiS
UL39OiSA
Maintenance
Manual
MM 390A01 Revision No: 2 Date: 2014-09-15

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
MM 390A01 Revision No: 2 Date: 2014-09-15 Page: 1 of 18
Preface
Thank you for deciding to use a ULPower engine.
Before carrying out maintenance work on the engine, carefully read the Maintenance Manual.
If any passages of the manual are not completely understood or in case of questions, please contact
a ULPower authorised dealer.
Remarks
The figures in this manual show the typical construction. They may not represent in full detail or
the exact shape of the parts which have the same or similar function.
In addition to this Maintenance Manual, please also refer to the Operating Manual
Modifications
The information and components/system descriptions contained in this Installation Manual are
correct at the time of publication. ULPower, however, maintains a policy of continuous
improvement of its products without imposing upon itself any obligation to install them on its
products previously manufactured.
ULPower reserves the right at any time to discontinue or change specifications, designs, features,
models or equipment without incurring obligation.
Engine serial number
On all enquiries or spare parts orders, always indicate the engine serial number, as the
manufacturer makes modifications to the engine for further development.
The engine serial number is located on the left side of the crankcase (near the front of the engine).
Repeating symbols
This manual uses the following symbols to emphasize particular information. These indications are
important and must be respected.
WARNING : Identifies an instruction which, if not followed, may cause serious injury
including the possibility of death.
Attention : Denotes an instruction which, if not followed, may severely damage the engine
or other components.
Note : Indicates supplementary information which may be needed to fully complete or
understand an instruction.

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
MM 390A01 Revision No: 2 Date: 2014-09-15 Page: 2 of 18
Safety information
This manual has been prepared as a guide to correctly service and maintain the UL390 aircraft
engine.
Keep an engine log and respect engine and aircraft maintenance schedules. Keep the engine in
top operating condition at all times. Do not operate any aircraft which is not properly maintained
or has engine operating irregularities which have not been corrected.
Spare parts must meet with the requirements defined by the engine manufacturer. This is only
warranted by use of genuine ULPower spare parts and/or accessories. They are available at the
authorized ULPower distribution- and service partners.
The use of anything other than genuine ULPower spare parts and/or accessories will render any
warranty relating to this engine null and void.
Please use proper hand tools and/or special service tools.
Torque wrench tightening specifications must be strictly adhered to. Locking devices must be
installed or replaced with new ones, where specified. If the efficiency of a locking device is
impaired, it must be renewed.
It is your responsibility to be completely familiar with the safety instructions including warnings
and cautions described in this manual. These warnings and cautions advise of specific operating
and servicing methods that, if not observed, can cause a serious engine malfunction or cause the
engine to loose power in flight which can result in loss of life, injury or damage to equipment.
It is, however, important to understand that the warnings and cautions are not exhaustive.
ULPower could not possibly know, evaluate and advise the user of all conceivable ways in which
service might be done or if the possible hazardous consequences of each way. Consequently,
Although the mere reading of such information does not eliminate the hazard, your understanding
of the information will promote its correct use. Always use common shop safety practice.
This information relates to the preparation and use of ULPower aircraft engines and has been
utilized safely and effectively by ULPower. However, ULPower disclaims liability for all damage
and/or injuries resulting from the improper use of the contents. We strongly recommend that any
service be carried out and/or verified by a highly skilled professional mechanic.
The maintenance functions detailed in this manual are to be considered as average (light)
maintenance. Repairs beyond these levels are not recommended as maintenance functions and
should be done by authorized overhaul facilities.

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Table of contents
Preface ..................................................................................................................1
Remarks...............................................................................................................1
Modifications.........................................................................................................1
Engine serial number ...............................................................................................1
Repeating symbols ..................................................................................................1
Safety information....................................................................................................2
Table of contents .....................................................................................................3
General..................................................................................................................4
Authorized Personnel...............................................................................................4
Procedure Notes.....................................................................................................4
Standard limited engine warranty & warranty conditions ...................................................5
Time Limits.............................................................................................................6
General note .........................................................................................................6
Time limits for engine operation.................................................................................6
Time limits for rubber parts ......................................................................................6
Annual inspection ...................................................................................................7
Scheduled maintenance checks ...................................................................................8
General note .........................................................................................................8
Maintenance schedule procedures ...............................................................................8
Inspection Sheet / Maintenance Schedule......................................................................9
Identification......................................................................................................9
Maintenance Schedule......................................................................................... 10
Engine back to operation ..................................................................................... 12
Maintenance tasks .................................................................................................. 13
General Note....................................................................................................... 13
Rocker Tappet Clearance ........................................................................................ 13
Cleaning air filter ................................................................................................. 13
Cylinder head bolts torque ...................................................................................... 14
Removal/change of spark plugs ................................................................................ 14
Idle speed adjustment ........................................................................................... 14
Compression test .................................................................................................. 17

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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General
Authorized Personnel
It is a requirement that every organization or individual possesses the required special tooling,
training or experience to perform all tasks outlined. Any task outlined herein may be performed if
the organization or individual has met the following conditions:
Requisite knowledge of the task through:
Experience in performing the task
Formal instruction from a ULPower authorized training facility or "on-the-job" instruction by
a ULPower or authorized ULPower distributor representative.
Suitable work environment to prevent contamination or damage to engine parts.
Suitable tools and fixtures as outlined in the Maintenance Manual.
Reasonable and prudent maintenance practices are utilized.
Requirements of the applicable regulatory authority regarding maintenance procedures are met.
Maintenance organizations and individuals are encouraged to contact ULPower throughout its
distribution network for information and guidance on any task outlined herein.
Procedure Notes
Prior to maintenance or service work, make absolutely sure to comply with the stated safety
instructions.
Principally ensure the following at each maintenance event:
Ignition "OFF"
Disconnect battery
Secure engine against unintentional operation.
At maintenance work which requires ignition "ON" and battery connected, take care of the
following:
Secure the propeller against unintentional turning by hand
Secure and observe propeller zone.
WARNING: These precautionary measures serve to avoid any injuries in case of an unintentional
start of the engine. Non-compliance can result in injuries or death.
At maintenance of lubricating and fuel system take care without fail that no contamination, metal
chips, foreign material and/or dirt enters the system.
WARNING: Always allow engine to cool down to outside air temperature before start of any
work. Severe burn and scalds may result if this is not respected.
Before re-using parts, clean, check and refit them as per instructions.
Before each re-assembly check units for any missing parts.
Attention:Strictly observe the tightening torques for screws and nuts. Over or under tightening
could cause severe engine damage.
If during disassembling/reassembling the removal of a safety item (e.g. Self-locking faster) should
be necessary, it must always be replaced by a new one.
Use clean screws and nuts only and inspect face of nuts and the thread for damage. If in doubt, use
new screws and nuts.
At reassembly of the engine, replace all sealing rings, gaskets, securing elements, o-rings and oil-
seals.
At disassembly of the engine, mark the components as necessary to avoid any mix-up. Take care of
the markings; do not remove them prior to re-assembly.

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
MM 390A01 Revision No: 2 Date: 2014-09-15 Page: 5 of 18
Standard limited engine warranty & warranty conditions
PERIOD
ULPower Aero Engines, as manufacturer, warrants
every ULPower non-certified aircraft engine, sold as
new and delivered by an authorised ULPower
distributor/reseller, to be free from defects in
material and workmanship for a period of 24 months
from the date of shipment from the ULPower factory
facilities.
Replacement of any engine, accessory or part under
the warranties will not create a new warranty period
or extend the period of coverage. But any engine, part
or accessory so repaired or replaced will be warranted
for the remainder of the original warranty period
applicable to the engine, accessory or part repaired or
replaced.
WARRANTY CLAIM
Written notice of any warranty claim must be
submitted to ULPower within fifteen (15) days of a
suspected defect in material or workmanship and the
engine, accessory or part must be made available for
ULPower's inspection within thirty (30) days after the
claim has been made.
To evaluate a claim, following items must also be
made available:
invoice delivered to the customer as proof of date
of purchase/delivery.
engine log book showing engine time and all
maintenance performed
signed and dated inspection/maintenance sheets.
ULPower reserves the right not to accept any claim
not submitted in accordance with these requirements.
TERMS AND CONDITIONS
The LIMITED WARRANTIES cover all parts and labour on
engines and accessories subjected to normal use and
operated and maintained in strict accordance with the
corresponding Operating and Maintenance Manuals. All
maintenance must be immediately noted, dated and
signed in engine logbook when maintenance is
performed or the warranties are VOID.
Warranty service may be accomplished ONLY AFTER
PRIOR WRITTEN APPROVAL from ULPower. ULPower
retains the right to repair and/or replace any parts or
accessories required for warranty service. All parts
replaced under warranty become the property of
ULPower.
The warranties are VOID on any engine or accessory,
disassembled, opened, repaired or altered without the
prior written approval of ULPower.
The warranties are also VOID on any engine or
accessory which has been operated contrary to
corresponding Installation, Operating and Maintenance
procedures or which in
ULPower's sole opinion has been subjected to misuse,
neglect, improper installation, corrosion, foreign
material ingestion, accident, the use of improper oil,
fuel or non genuine ULPower replacement parts.
The warranties are also VOID on any engine or
accessory if a gear reduction or other power
transmission device (including propeller flange exten-
sions) not designed or approved in writing by ULPower
has been used.
The warranties do not include reimbursement for
normal maintenance expenses or for incidental
expenses such as but not limited to, mounting and
dismounting of the engine from the aircraft, loss of
use, transportation, towing, communication costs,
taxis, hotels, food or any other incidental or
consequential damage.
DISCLAIMER
ULPOWER'S EXPRESS WARRANTEES AND THE REMEDIES
THEREUNDER ARE EXCLUSIVE AND GIVEN IN PLACE OF (a)
ALL OTHER WARRANTIES, EXPRESS, IMPLIED, OR
STATUTORY, WHETHER WRITTEN OR ORAL, INCLUDING,
BUT NOT LIMITED TO, ANY WARRANTY OF
MERCHANTABILITY, FITNESS OR PARTICULAR PURPOSE,
OR IMPLIED WARRANTY ARRISING FROM PERFORMANCE,
COURSE OF DEALING OR USAGE OF TRADE AND (b) ALL
OTHER OBLIGATIONS, LIABILITIES, RIGHTS, CLAIMS OR
REMEDIES, EXPRESS OR IMPLIED, ARISING BY LAW OR
OTHERWISE, INCLUDING BUT NOT LIMITED TO ANY RIGHT
OR REMEDIES IN CONTRACT, TORT, STRICT LIABILITY OR
ARISING FROM ULPOWER'S NEGLIGENCE, ACTUAL OR
IMPUTTED.
ULPOWER'S OBLIGATIONS AND PURCHASER'S REMEDIES
UNDER ULPOWER'S EXPRESS WARRANTIES ARE LIMITED TO
ULPOWER'S CHOICE OF REFUND, REPAIR OR
REPLACEMENT ON AN EXCHANGE BASIS AND EXCLUDE
LIABILITY FOR INCIDENTAL, SPECIAL, CONSEQUENTIAL OR
ANY OTHER DAMAGES, INCLUDING WITHOUT LIMITATION,
ANY LIABILITY OF CUSTOMER TO A THIRD PARTY OR FOR
ECONOMIC LOSS, REPLACEMENT COST, COST OF CAPITAL,
LOST REVENUE, LOST PROFITS, OR LOSS OF USE OF OR
DAMAGE TO AN AIRCRAFT, ENGINE, COMPONENT OR
OTHER PROPERTY AND IN NO EVENT WILL ULPOWER'S
LIABILITY EXCEED THE ORIGINAL COST OF THE ENGINE OR
ACCESSORY.
These LIMITED WARRANTIES are the only warranties
offered by ULPower. No agreement varying these
warranties or ULPower's obligations under them will
be binding on ULPower unless made in writing by a
duly authorised representative of ULPower and
accepted in writing by ULPower.
ULPower will not process or honour warranty
claims on delinquent accounts.
Effective as of August 19th , 2013

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Time Limits
General note
These checks, related to limited periods of operation, are planned to help avoid engine troubles by
the use of preventive maintenance.
Time limits for engine operation
The time limits for engine operation will be specified by the TBO (Time Before Overhaul). After
reaching this time limit the engine should be shipped to an authorized ULPower overhaul facility.
For an overhaul, the engine must be removed from the aircraft, be cleaned, preserved and all
openings to be closed to prevent entering of contaminants.
Attention:A general overhaul is due after a defined period of operation or after a specified
calendar life since initial start of operation (whichever comes first).
Engine
Type description
Engines affected
engine S/N
TBO
Time Between Overhaul
UL390i / UL390iSA
all
1500 h or 8 years,
whichever comes first
UL390iSA
all
250 h or 4 years
whichever comes first *
* This do not mean that the engine needs a complete overhaul. However it
is necessary to do a complete check up in the ULPower factory. Because
of inverted flying, it is possible that certain components were not
temporally greased. Find out if there is some earlier “use” of components
is necessary.
The shipment to an authorized ULPower overhaul facility must include the following:
Engine log book
Maintenance records of the engine (i.e. all maintenance check lists, and reports of operation, of
maintenance, of findings and of oil analyses).
The engine and ECU.
Statement of total period of operation (TSN –Time Since New) and if applicable the period of
operation after a conducted general overhaul (TSO –Time Since Overhaul).
Data about the type of aircraft and propeller used
Useful remarks and observations concerning the engine.
Time limits for rubber parts
Every six years the following components must be renewed:
Venting and return hose between breather and oil/air separator
Engine mount rubbers
All fuel lines
Oil lines to/from oil cooler

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Annual inspection
Perform a 100hr. check at intervals of 100 hours of operation or once every 12 months, whichever
comes first. Every second year the 200 hour check should be performed.

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
MM 390A01 Revision No: 2 Date: 2014-09-15 Page: 8 of 18
Scheduled maintenance checks
General note
This chapter lists the periodic inspections which must be carried out after specified periods of
operation.
Periodic inspections are those that must be performed at 50, 100 and 200 hour intervals in
accordance with the maintenance schedule (see further). Additionally a 15 hr. inspection must be
performed at 15 hours of operation of a new or overhauled engine.
Maintenance schedule procedures
All stated checks are visual inspections for damage and wear, unless otherwise stated.
All listed work must be carried out within the specified period.
For all the maintenance work an allowance of ±10hr. or 30days will be granted but these
tolerances must not be exceeded. This means that if for instance after a 100hr. check actually
carried out at 110hr. the next check is due at 200hr. ±10hr. and not at 220hr. ±10hr.
If a maintenance check is performed before the prescribed interval, the next check is to be done
at the same interval (e.g. if first 100hr. check is done at 87 hours, the next 100hr. check has to be
done at 187 hours ±10hr. or 1 year later; whichever comes first).
Checks are carried out as per the maintenance schedule where type and volume of the
maintenance work is outlined in key words.
The Inspection Sheet/ Maintenance Schedule must be filled out at each maintenance event. For
copies please contact a ULPower representative.
All pages of the maintenance check list must be marked with the respective check (e.g. 100hr.
check) on the top of the list.
All of the maintenance carried out must be initialled in the "signature" area by the performing
aircraft mechanic.
After maintenance, checks must be entered in the maintenance records. The maintenance must
be confirmed in the log book.
All discrepancies and repairs must be recorded in a report of findings to be generated and
maintained by aircraft owners.
Replacement of equipment (e.g. fuel pump, filters, etc.) has to be entered into the engine log
book stating TSN and date.

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Inspection Sheet / Maintenance Schedule
Identification
AIRCRAFT
Registration number _______________________________
Aircraft Make _______________________________
Aircraft model and S/N _______________________________
TSN (Time Since New) _______________________________
Propeller make _______________________________
Propeller model and S/N _______________________________
ENGINE
Engine type _______________________________
Engine S/N _______________________________
TSN (Time Since New) _______________________________
TSO (Time Since Overhaul) _______________________________
Type of oil used _______________________________
Type of fuel used _______________________________
AIRCRAFT OERATOR
Name _______________________________
Contact _______________________________
Address _______________________________
_______________________________
_______________________________
Tel / Fax _______________________________
E-mail _______________________________
MAINTENANCE FACILITY
Maintenance work shop _______________________________
Address _______________________________
_______________________________
_______________________________
Tel / Fax _______________________________
E-mail _______________________________
This check is applicable (circle one) 5* 15h* 50h 100h 200h 600h
*Shaded column for first 5 and 15 hr. only (from new or overhauled engine)

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Maintenance Schedule
Perform the following inspection tasks at the intervals shown. Some tasks are explained under
chapter "Maintenance tasks" (see further).
Legend: X = do the task
Blank = no task required
Inspection Items
Check (hr.)
Signature
5
15
50
100
200
Visual inspection of the engine
a) General inspection of the engine for damage and
abnormalities, including obstructions, cracks, wear and
condition of cooling air ducts, baffling and cylinder
cooling. Take note of changes caused by temperature.
X
X
X
X
b) Thoroughly inspect engine for missing or loose bolts, nuts,
pins, etc. Replace as necessary.
X
X
X
X
c) Inspection of all temperature and pressure sensors.
X
X
X
X
d) Inspection of all oil lines for damage, including leakage,
hardening from heat, porosity, loose connections and
secure attachments. Verify routing for kinks and
restrictions like restricted elbows.
X
X
X
X
e) Inspect all fuel lines, filters, injectors and pressure
regulator for damage, including leakage, hardening from
heat, porosity, loose connections and secure attachments.
Verify routing for kinks and restrictions like restricted
elbows.
X
X
X
X
f) Verify the complete electrical wiring system including
tight fit of connectors, damage and wear.
X
X
X
X
g) Check exhaust system for cracks (especially when cabin
heating is taken from around the exhaust).
X
X
X
X
Verification of engine suspension
a) Inspect engine mounts, dampers and fasteners for secure
fit, including damage from heat, deformation, cracks.
Replace as necessary.
X
X
X
X
Engine external parts
a) Inspect attachment screws and nuts of all external parts
for security and fit. Inspect safety wiring. Replace as
necessary.
X
X
X
X
ECU
a) - disconnect connector from ECU
- check the contacts ECU-side and connector side
- be sure they are clean and there is no oxidation
- replace both if necessary
- connect the connector to the ECU
X
X
X
Propeller Flange
a) check the torque of the propeller flange bolt:
must be 300 Nm
X
X

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Inspection Items
Check (hr.)
Signature
5
15
50
100
200
Oil level
a) Remove drain plug from bottom of oil sump. Drain old oil
and inspect for foreign particles.
X
X
X
b) Replace copper sealing washers of drain plug and refit to
oil sump.
X
X
X
c) Refill oil sump with approx. 4 litres of oil. For correct type
of oil, refer to Operating Manual.
X
X
X
d) Inspect oil level and add oil as necessary to maximum
mark. For correct type of oil, refer to Operating Manual.
Quantity of oil added : ________ litres
X
X
X
X
Oil filter
a) Remove oil filter from engine and install new oil filter.
Lubricate mating sealing ring of new oil filter with engine
oil. Screw on new filter by hand.
X
X
X
X
Air filter
a) Inspection of the air filter. Clean/replace as necessary.
X
X
X
b) Replace air filter.
X
Fuel filters
a) Remove all fuel filters from aircraft and install new ones.
X
Cylinder heads
a) Check torque of cylinder head bolts. Re-torque as
necessary (36Nm) –Do not loosen first.
Cylinder heads to be re-torqued : 1 / 2 / 3 / 4 / 5 / 6
X
X
X
Rocker tappet
a) Check tappet-valve clearance and adjust as necessary
(0.15mm ±0.05mm cold inlet and exhaust)
(0.006in ±0.002in)
Circle tappet in need of adjustment + mark clearance
before adjustment:
IN1: _______ EX1: _______ IN2: _______ EX2: _______
IN3: _______ EX3: _______ IN4: _______ EX4: _______
IN5: _______ EX5: _______ IN6: _______ EX6: _______
X
X
X
X
Throttle valve
a) Inspect free movement of throttle lever.
Inspect that throttle cable allows full travel of throttle
lever.
X
X
X
X
a) Inspect throttle cable. Replace as necessary.
X
Spark plugs
a) Renewal of spark plugs.
X

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Inspection Items
Check (hr.)
Signature
5
15
50
100
200
Spark plug connectors
a) Verify security of connectors on both spark plug and
ignition coils.
X
X
X
X
Check of compression
a) Inspect compression by differential pressure method.
Test pressure = ______ bar (psi)
Pressure drop cyl.1 ________ cyl.2 ________
(% or fraction) cyl.3 ________ cyl.4 ________
cyl.3 ________ cyl.4 ________
X
Engine test run
X
X
X
X
a) Start the engine and run to operating temperature.
Smoothly apply throttle to full power.
Check temperatures and pressures are within limits
Record oil pressure: ________ bar
Record fuel pressure: ________ bar
Record engine speed: ________ rpm
Bring engine to idle speed.
Record engine speed: ________ rpm
X
X
X
X
b) After engine test run, if replaced, retighten oil-filter by
hand
X
X
X
X
c) After engine test run, inspect oil level and add oil as
necessary to maximum mark.
X
X
X
X
d) After engine test run, adjust idle speed lever position if
necessary
Record new engine idle speed: ________ rpm
X
X
X
X
General note
a) All service instructions and service bulletins are complied
with.
X
X
X
X
Engine back to operation
All the stated checks or listed work has been carried out as to the recommendations of the engine
manufacturer and was recorded in the engine log book.
Next check due at : ____________________ hr. (TS___) (engine hours)
or before date ____________________
Name Location Signature Date
________________ __________________ ___________________ _____________

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Maintenance tasks
General Note
This chapter serves solely for supplement and detailed explanation of some points from the
Maintenance Schedule.
Rocker Tappet Clearance
Unscrew all valve covers (1) with a 4mm Allen Key. Verify rocker tappets have had proper
lubrication. Look out for colour changes that could indicate bad lubrication or over heating.
Carefully turn propeller until both rocker arms from cylinder 2 are “tumbling”. In this situation,
rocker arms from cylinder 1 are in neutral position. ( neither pushed in ). Start with tappets from
cylinder 1.
Check tappet clearance by inserting a feeler gauge in
between the rocker tappet and valve stem (2). Both
cold inlet and exhaust tappet clearance should be
0.15±0.05mm (0.0059±0.0020inch).
To adjust tappet clearance, loosen nut (3) with a
13mm Spanner. Turn tappet adjusting screw (4) with
a 5mm Allen Key. Tighten nut (3) to 20 Nm (14.7 ft
lbs) whilst holding Allen Key in place to prevent
adjusting screw from turning.
Note: After tightening the nut (3), recheck the
tappet clearance to make sure adjustment is
ok.
After checking/adjusting tappet clearance cylinder 1, turn the propeller half a turn (180°)
anticlockwise (standing in front of propeller) until both rocker arms from cylinder 1 are tumbling
and adjust tappet clearance from cylinder 2. Do the same procedure for cylinder 3, 4, 5 and 6
Attention:Continued operation with incorrectly adjusted tappets can result in severe damage
to the engine.
Before closing valve covers beware the o-ring (5) is completely in it’s groove and in the correct
position. Tighten valve cover cap screws M5x10mm to 6 Nm (4.5 ft lbs).
Attention:When same tappets are in need of adjustment every time maintenance is
performed, complete valve train should be checked for abnormal wear. Also check
for proper lubrication and clogged oil lines.
Cleaning air filter
Inspect air filter according to maintenance schedule. Clean dirty filter as follows:
Lightly tap and brush off surface dirt.
Spray filter cleaner onto entire element and let soak for approx. 10 min.
Rince filter with low pressure water from inside to outside and let element dry naturally.
Note: Never use gasoline, steam, caustic liquids, detergents or high pressure cleaning.
Attention: A dirty air filter will not only reduce the engine performance but might also promote
premature wear to the engine. It can also result in an over-rich fuel mixture.
WARNING: When used in heavy dust conditions, clean air filter at 25 h intervals accordingly. If
filter mat is damaged, replace air filter.
4
3
1
2
5

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
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Cylinder head bolts torque
As cylinder head bolts normally don't need re-torqueing, checking torque is only a precautionary
safety measure. Therefore it is sufficient to only check the torque of the 4 cylinder head bolts
which are easily accessible. If re-torqueing should be necessary, then all bolts need checking. Inlet
manifold, valve covers and plug ( n°6 parts catalogue ) shall have to be removed to access the 2
other bolts on the cylinder head.
Note: When checking torque, do not loosen first.
Removal/change of spark plugs
Unplug ignition leads and unscrew spark plugs with 16mm Plug Socket.
Note: As in any modern automobile, sparkplugs do normally not need cleaning.
Certainly do not use steel or brass brushes for cleaning and never
sand blast spark plugs! If you really want to clean spark plugs, use
a plastic brush in a solvent.
Spark plug consists of 3 electrodes round the core. Electrode gap cannot
be changed. Do not try to bend the electrodes!
Note: Operation with leaded fuels (e.g. AVGAS 100LL) can result in
increased wear of the spark plugs. Reduce renewal intervals accordingly.
At replacement only use spark plug type: Bosch FR 5 DTC
Attention:Use of incorrect spark plugs may result in ignition problems or electrical disturbance
and possible consequential engine damage.
Before inserting spark plugs back into cylinder head, apply appropriate anti-seize compound on
thread. Screw in spark plugs with fingers to seat; only then use Plug Socket to tighten to 21 Nm.
Place back ignition leads; make sure spark plug connectors are secure.
Idle speed adjustment
The throttle lever stop (1) is factory set to a position that should correspond to a warm engine idle
speed of approx. 800 rpm.
Attention:The idle speed of the engine should not be less than 700 rpm as rough turning could
cause damage to the engine. We recommend a minimum of at least 800 rpm.
With a cold engine, user should apply a little throttle so idle speed is at least 1000 rpm during
warm-up. Only when engine is at operating temperature, minimum idle speed can be tested/set.
WARNING: Adjusting idle speed should always be done while engine and master switch are
switched off.
WARNING: Take great care when adjusting throttle lever stop as the engine will be hot.
If the warm idle speed of the engine is unsatisfactory, adjust as follows:
If idle speed is too low: while engine is running
apply throttle to the desired engine rpm. Set
friction to keep throttle in position and turn off
engine. Loosen throttle lever stop screws (3) with a
2.5mm Allan Key and move throttle lever stop (1)
towards the left until it touches the throttle lever
(2). Tighten throttle lever stop screws (3) to
maximum 3 Nm (2.25 ft lbs).
If idle speed is too high, firstly verify if throttle
lever (2) is completely against the throttle lever
stop (1). If not, stops of aircraft throttle system are

Maintenance Manual ULPOWER UL390i UL390iSUL390iSA
MM 390A01 Revision No: 2 Date: 2014-09-15 Page: 15 of 18
not set correctly. Adjust according to aircraft manual or manufacturer. Otherwise loosen throttle
lever stop screws (3) with a 2.5mm Allan Key and move throttle lever stop (1) a few mm towards
the right. Tighten throttle lever screws (3) and test engine idle. Idle rpm will probably be too low;
readjust as described above.
Note: Do not leave throttle lever stop screws (3) loose while engine is running to test idle speed.
Propeller flange bolt torque check
1. Unscrew the M6 screw with an allen key
dimension 3.
2. Remove the locking plate. Use a M6-bolt to
pull out the plate.
3. Attach the propeller flange holder (T063002)
to the prop flange with M14 bolts.
4. Torque the bolt to 300 Nm while holding the
prop flange. ( right hand thread )

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5. Place the locking plate over the hex top of the
bolt. Find out if the existing M6 hole in the
locking plate correspond with the M6 hole
in the flange. If not, move the ring for 60°
on the bolt
6. Only when the M6 holes do not correspond:
- drill a hole ø5 through the locking plate
- cut M6 thread till the button of the hole
- replace the hexagon socket screw
M6x15 and fix with Loctite 243
- lock the screw again by punching 2
dimples
7. Attention!! It is possible that while running the engine the bolt loose the torque a little bit.
Therefore it’s necessary to re-torque the bolt after 10 hours and again after 20 hours.
Afterwards, follow maintenance manual.

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Leak test
The best practice for testing the compression in a
cylinder of an internal combustion engine, is the
"differential compression" test. It requires the use of a
tester consisting of two separate pressure gauges, a
pressure regulator, a calibrated restrictor orifice, and
an on/off valve (see schematic drawing). A source of
compressed air (a compressor with a storage tank
capable of a minimum of 100psi [7 bar]) is required to
perform the test. Be sure that the restrictor orifice of
the tester is 0.040" [1mm]
The leak test should be done after the engine has run
to operating temperature. It is important to use
exactly the same procedure with each cylinder and
each time you check your compression, if your test is
to give meaningful and accurate results. It is very
important that accurate records are kept of which
compression reading was for which cylinder!
WARNING: Make sure master switch and ignition
are OFF when performing work on the
engine.
Remove all valve covers, one sparkplug from each
cylinder and, for safety, remove each ignition lead
from all plugs. Rotate the prop by hand (anti-
clockwise when standing in front of propeller) until
cylinder 2 is exactly on top position while both rocker
arms are tumbling. Now cylinder No.1 will be on compression. You can verify this by moving the
prop back a quarter turn and then placing your thumb over the spark plug hole and feeling the
pressure build-up while bringing the prop back to TDC. Now install the 14mm threaded adaptor
(normally supplied with the compression tester) in the spark plug hole of the cylinder to be tested
(Cyl.1).
WARNING: Be certain that the air shutoff valve is closed and that you have a firm grip on the
tip of one blade of the prop before connecting the system to your source of
compressed air.
Move the prop slightly away from TDC by turning clockwise. Adjust the pressure regulator to about
20 psi and slowly open the air shutoff valve. Carefully rotate the prop in the turning direction (anti-
clockwise) against the 20 psi pressure towards TDC until you feel a "flat spot" or rapid loss of turning
resistance. If you go too fast, back up beyond top dead center and try again. It is critical that you
reach TDC with the prop turning in the normal direction of rotation, not while backing the prop up
since this would unseat the piston rings. The piston rings must be at the bottom of their lands in the
piston with the piston at the top of its travel. Now make sure you have the prop tip securely held.
This is a good time to have a second person help you. The air shutoff valve should be open and
slowly adjust the pressure regulator to show exactly 80 psi on the pressure regulator gauge.
WARNING: Use caution because if you let the prop move in either direction beyond TDC, it will
rapidly begin to rotate and hit and severely injure the person who should have been
holding it securely.
Now gently move the prop tip back and forth, just a tiny amount. Watch the cylinder pressure gauge
and take a reading from it at its peak steady pressure. Again, this will be while moving the prop in
the normal direction of rotation. Be certain that the regulator pressure gauge is holding precisely 80
psi. You should have a differential pressure reading of between 60 and 78 over 80.
Lower pressure regulator and close off air shutoff valve. Disconnect system from cylinder. Turn prop
in normal direction half a turn and repeat test with next cylinder in following order (1-4-5-2-3-6).

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You should now have a series of numbers something like this, depending on the condition of the
engine: 76/80, 74/80, 73/80 and 75/80. These numbers, hopefully, will be fairly close to each other
in magnitude. What are the limits? What constitutes a bad (too low) cylinder? It is generally
accepted that a cylinder reading below 60/80 would require removal from service.
A single leak test does not necessarily mean anything. No single diagnostic test should ever be used
to decide the health of your engine. The key is to do these tests regularly and keep good records of
what you see. Compare each test and make your decision based on several tests conducted over a
reasonable period of time.
If you have an abnormally low cylinder, you should start the engine and run it on the ground or even
fly around the pattern once. Test it again. If it is still low, use a length of garden hose as a
"stethoscope" and listen at the exhaust of the ailing cylinder. If you hear a hissing escape of
compressed air here, you have an exhaust valve that is not seating. Similarly, listen carefully with
the "stethoscope" at the intake, throttle/air box. A hissing sound here would indicate leakage under
the intake valve. If neither of these areas is leaking significantly, listen at the breather or oil
dipstick/filler tube. A leak in this area is indicative of ring blow-by. This could be ring wear, barrel
wear or scoring, or all the ring gaps may be lined up. Hissing between cylinder cooling fins is bad
news, possibly a cracked cylinder. Valve leakage is the most commonly found cause of a low
cylinder.