MT-Propeller P-8S Series Specification sheet

ATA 61-08-54
(E-3854)
(Avia Manual No. E-1625)
OPERATION- AND INSTALLATION MANUAL
HYDRAULIC OVERSPEED GOVERNOR
P-8S( )-( ) SERIES
EASA DE.21G.0008
EASA.21J.020
Original Issue: 2021-08-13
The technical content of this document is approved under authority of DOA No.
EASA.21J.020.

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Warning
People who fly should recognize that various types of risks are involved; and they should
take all precautions to minimize them, since they cannot be eliminated entirely.
The governor is a vital component of the aircraft.
A mechanical failure could cause a forced landing.
Governors are subject to constant vibration stresses from the engine.
Before a governor is certified as being safe to operate on an airplane engine, an adequate
margin of safety must be demonstrated.
Even though every precaution is taken in the design and manufacture of a governor,
history has revealed rare instances of failures, particularly of the fatigue type.
It is essential that the governor be properly maintained according to the recommended
service procedures and a close watch be exercised to detect impending problems before
they become serious.
Unusual operation characteristics should be investigated and repaired as it could be a
warning that something serious is wrong.
As a fellow pilot, I urge you to read this Manual thoroughly. It contains a wealth of
information about your new governor.
The governor is among the most reliable components of your airplane. It therefore
deserves the care and maintenance called for in this Manual.
Please give it your attention, especially the section dealing with Inspections and Checks.
Thank you for choosing a MT-Propeller governor, manufactured by AVIA Propeller.
Properly maintained it will give you many years of reliable service.
Gerd R. Mühlbauer
President
MT-Propeller Entwicklung GmbH

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TABLE OF CONTENTS
Page
Table of Contents (Overview) 2
List of Revisions 3
List of Effective Pages 4
1. General 5
2. Model Application 6
3. Performance Data 7
4. Design and Operation Information 8
5. Installation and Operation Instruction 10
6. Inspections 11
7. Trouble Shooting 12
8. Shipping and Storage 13
9. Governor Installation Record 14

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LIST OF REVISIONS
Rev. No.
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Description
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LIST OF EFFECTIVE PAGES
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1. GENERAL
The P-8S( )-( ) hydraulic overspeed propeller governors are single acting governors developed for
hydraulically variable pitch propellers to protect propellers against overspeeding.
Statement of Purpose
This publication provides operation, installation and line maintenance information for the MT- Propeller
governors.
Installation, removal, operation and troubleshooting data is included in this publication. However, the
airplane manufacturer's manuals and applicable propeller manuals should be used in addition to this
information.
1.1 DEFINITION OF COMPONENT LIFE AND SERVICE
1.1.1 Overhaul
Overhaul is a periodic process and contains the following items:
•Disassembly
•Inspection of parts
•Reconditioning of parts
•Reassembly
The overhaul interval is based on hours of service (operating time) or on calendar time.
At such specified periods, the overspeed governors should be completely disassembled and inspected
for cracks, wear, corrosion and other unusual or abnormal conditions. As specified, certain parts
should be refinished, and certain other parts should be replaced.
For overhaul interval for the overspeed governors please refer to Service Bulletin 1.
1.1.2 Repair
Repair is correction of minor damage caused during normal operation. It is done on an irregular basis,
as required.
A repair does not include an overhaul.
Amount, degree and extent of damage determines whether or not a governor can be repaired
without overhaul.
1.1.3 Component Life
Component life is expressed in terms of total hours of service (TT, or Total Time) and in terms of hours
of service since overhaul (TSO, or Time Since Overhaul).
Both references are necessary in defining the life of the component. Occasionally a part may be "life
limited", which means that it must be replaced after a specified period of use.
Overhaul returns the component or assembly to zero hours TSO (Time Since Overhaul), but not to
zero hours TT (Total Time).
No life limit is established for the overspeed governors P-8S( )-( ).

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2. MODEL DESIGNATION
P - 8SX - X
1 -2 3 4
Legend:
1P = Propeller Governor / Overspeed Governor manufactured by AP
28S = Overspeed Governor
31 = Solenoid valve for resetting, AND 20010 drive pad modified (TP-100)
2 = Solenoid valve for resetting, AND 20010 drive pad
3 = Solenoid valve for resetting and feathering, AND 20010 drive pad
4 = reserved
4= Application Number, RPM setting, voltage, etc.
S/No = 09 S 003
a b c a = Year of Manufacture
b = Overspeed Governor
c = Consecutive Number

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3. PERFORMANCE DATA
Range of acceptable operation temperature from -16°C (+3.2°F) to +150°C(+302°F).
The break away torque with engine oil SAE No. 40 at 4.5°C (+40°F) is 40 Nm ( 30 ft lbs)
The torque required at 220 psi and 2700 rpm is 0,1 Nm ( 0,8 inch lbs)
3.1 DIMENSIONS
Fig. 1 –Weight = 1,15 kg (2,36 lbs) in basic configuration
MT-Propeller, Straubing made by Avia Propeller
P/N _________________ S/N ____________ ASSY____

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4. DESIGN AND OPERATION INFORMATION
The Avia Propeller aircraft overspeed governors P-8S( )-( ) are base mounted centrifugal overspeed
governors for use with single acting constant speed propeller control systems on turboprop engines.
The propeller overspeed governor is located on the reduction gearbox. It limits propeller RPM should
the primary propeller governor fail. Constructed in the same manner as the primary governor with
speeder spring, flyweight assembly, and pilot valve, and driven by gears from the propeller shaft, the
overspeed governor constantly monitors propeller RPM. Should the primary propeller governor fail and
the prop begin to overspeed, the overspeed
governor will ACTIVATE at given speed setting by detouring high pressure oil back to the reduction
gearbox. The overspeed governor should then govern the propeller at given speed. Ground test of the
overspeed governor is provided by a test valve actuated by a
28-VDC solenoid. A pushbutton, located on the TEST panel at the bottom of the instrument panel in
the cockpit, activates the solenoid and opens the test valve, allowing high pressure
oil to reset the normal overspeed setting to given percentage below normal. A properly functioning
overspeed governor is indicated during ground test by the propeller RPM stabilizing at adjusted lower
propeller speed. Releasing the TEST button resets the
overspeed governor to normal operation and the propeller RPM rises toward the normal governing
RPM.
UNDERSPEED
If the primary propeller governor works properly, the overspeed governor is in underspeed condition.
Propeller speed setting of the overspeed governor is over the primary propeller governor speed setting.
Underspeed condition means, that the force of the preloaded speeder spring (representing requested
speed) is higher than the force from rotating flyweights (representing actual speed) and thus the pilot
valve is forced down (see diagram) covering the control ports in the drive shaft. It avoids pressure oil
to flow from the pitch changing mechanism. The overspeed governor doesn´t enter in control loop of
the primary propeller governor.

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ON-SPEED
If the primary propeller governor is in failure mode or the overspeed governor is in reset condition, the
overspeed governor controls the propeller speed, if other circumstances (engine power, velocity, …)
enable propeller to reach speed setting. In this condition the forces action on the engine-overspeed
governor-propeller combination is in a state of balance. The propeller blades are at the correct pitch
to absorb the power developed by the engine. The centrifugal force of the rotating flyweights exactly
balances the force of the speeder spring. The pilot valve located in the drive-gear shaft is in such
position, that the control ports between the oil pump and the propeller pitch changing servo are covered
such a way, that propeller blades stay in appropriate position.
OVERSPEED
This condition occurs when engine rpm increases above the on-speed value - set by the speeder
spring preload. The rotating flyweights pivot outward as their increase centrifugal force overcomes
force exerted by the speeder spring.
The flyweight toes raise the pilot valve plunger, uncovering ports in the driver gear shaft that permit
pressure oil to flow from the propeller pitch changing mechanism. This allows propeller counterweights
to take the propeller blades toward a higher pitch. The load on the engine is increased and engine
speed is reduced.
Fig. 2 –Functional diagram

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5. INSTALLATION AND OPERATION INSTRUCTION
a) If applicable: Remove old overspeed governor per aircraft service instructions.
Prepare new mounting gasket, P/N B-20024. Coat gasket with engine oil or equivalent before
installation.
b) Check that mounting studs project a minimum of 31,75 mm (1.250 inch) from face of engine pad.
c) Clean engine pad, studs and mounting hardware before installing new mounting gasket.
Insure overspeed governor drive spline mate correctly with engine accessory drive spline.
d) Attach mounting hardware and torque the (4) mounting nuts to 20-24 Nm (180-220 inlbs).
e) Reconnect cable connector.
f) Ground test check will verify proper RPM setting by pressing the test button. Record RPM. Tests
should be done in smooth air.
g) Also check for oil leaks –none permitted.
5.1 GOVERNOR REMOVAL
a) Disconnect electric cable from the overspeed governor.
b) Remove mounting nuts and washers.
c) Pat on the overspeed governor to release it and then remove governor from engine pad.
Governor drive and engine pad must be without impurities (metal chips, etc.).
d) If it is necessary clean governor drive and engine pad by appropriate means.
e) Apply the gasket and transport cover to governor base.
f) Record the removal in governor installation record.
g) Perform preservation in accordance with section 8. to prepare for long-term storage.
h) Storage in accordance with section 8.

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6. INSPECTIONS
Check for oil leakage.
Check oil leakage immediately after engine stop.
Check oil leakage at governor’s surface and at mounting pad.
If oil leakage is detected, check stop nuts at the governor housing and the mounting nuts.
Torque if necessary. If oil leakage is detected repeatedly, contact Service Center or governor’s
manufacturer.
WARNING:
NO OIL LEAKAGE IS PERMITTED.

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7. TROUBLESHOOTING
Propeller speed is not reduced by pressing TEST button –Possible Causes:
a) The solenoid is not energized
Check voltage on the connector after pressing the TEST button. If no voltage appears, check
aircraft electric circuits.
b) The solenoid burned.
Check solenoid resistance –if it is out range, replace the overspeed governor.
c) The overspeed governor doesn’t keep lowered speed.
The overspeed governor is failed –exchange it.

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8. SHIPPING AND STORAGE
Conservation
Inner conservation is automatically done by engine oil. Attach cover cap.
After installing the overspeed governor the conservation is done together with engine in accordance
with the instruction of the engine manufacturer.
Outside conservation isn’t required.
Pack the overspeed governor in two layers of wax cloth and put it in a plastic bag. The plastic bag
should be vacuumed and after that welded.
Make a note in the governor’s installation record.
De-conservation isn’t needed.
Storage
Overspeed governors have to be packed in carton box with accessory documentation.
Store governors in temperature from +10°C (+50°F) to +30°C (+86°F) and relative humidity from 40%
to 80%. Keep stock room free of gases with deleterious effect.

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9. OVERSPEED GOVERNOR INSTALLATION RECORD
Date
installed
Notes
Authorized
Signature
Date
removed

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WARRANTY REGISTRATION CARD
1) To be eligible for warranty, this registration card must be returned completely and signed by the
end user to the authorized Avia Propeller distributor of the area in which the governor is firstly
operated or to MT-Propeller itself within 30 days after date from starting operation.
2) No other warranties and/or guarantees than defined in the actual warranty conditions are made.
3) Overspeed Governor Type:
P
-
A
-
S/N:
Date of purchase (day/month/year):_/_/_
Date of De-conservation (day/month/year):_/_/_
Owner's name: ............................................................
Company: ....................................................................
Address: ....................................................................
City/State/Postal code ..................................................
Country: .......................................................................
Telephone: ......................... Telefax: .........................
E-mail: ........................................................
Sold by: .........................
I have read and understood the Operator’s Manual in its entirety and will observe the instructions
therein.
Date:................................. Signature:..................................