ho-v 373()() -d()r-() - hoffmann propeller · hoffmann propeller manual no. e709 operation and ......

HOFFMANN PROPELLER MANUAL NO. E709

OPERATION AND MAINTENANCE MANUAL

for

VARIABLE PITCH AND REVERSING PROPELLER

HO-V 373()() -D()R-()

Hoffmann GmbH & Co. KG Küpferlingstraße 9

D-83022 Rosenheim Tel.: ++49/(0)8031/1878-0 Fax: ++49/(0)8031/1878-78

Revision A 61-11-01 Page I April 2008


Warning

People who fly, or are operating a propeller driven vessel, should recognize that different types of risks are involved, and they should take all possible precautions to reduce them, because they cannot be eliminated entirely. The propeller is a vital component of the aircraft or of the propeller driven vessel. A mechanical failure could cause a forced landing of the aircraft or create vibrations sufficiently severe to damage the aircraft or the propeller driven vessel and make it disabled.

All propellers are subject to constant vibration stresses from the engine and airstreams, which are added to high bending and centrifugal stresses.

Before a propeller is certified as being safe to operate on an airplane or a propeller driven vessel an adequate margin of safety must be demonstrated. Even though every precaution is taken in the design and manufacture of a propeller, history has revealed rare instances of failures, particularly of the fatigue type.

It is essential that the propeller is properly maintained according to the recommended service procedures and a close watch is exercised to detect impending problems before they become serious. Any grease or oil leakage, loss of oil pressure, unusual vibration or change in operation behaviour should be investigated and repaired very carefully 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 propeller.

The propeller is among the most reliable components of your airplane, or the propeller driven vessel. It is also among the most critical to flight safety. It therefore deserves the care and maintenance called for in this Manual. I kindly ask you please give it your attention, especially the section dealing with Inspections and checks.

I like to thank you very much for choosing Hoffmann Propeller. Properly maintained it will give you many years of reliable service.

Your Hoffmann Crew.

Revision A 61-11-01 Page I April 2008


For operator of non certified or experimental aircraft, or the propeller driven vessel, even a greater level of vigilance is required in the maintenance and inspection of the propeller. Experimental installation often uses propeller- engine combinations that have not been tested and approved. In these cases, the stress on the propeller and, therefore, safety margin is not known. Failures could be as severe as loss of propeller or propeller blades and cause loss of propeller control and / or loss of aircraft or the propeller driven vessel.

Hoffmann Propeller GmbH follows the EASA regulations for propeller certification on certified aircraft. Experimental aircraft may operate with unapproved engines or propellers or engine modifications to increase horsepower, such as unapproved crankshaft damper configurations or high compression pistons. These issues affect the vibration output of the engine and the stress levels on the propeller. Significant propeller life reduction and failure are real possibilities.

Frequent inspections are strongly recommended if operating with a non-certificated installation, however, these inspections may not guarantee propeller reliability, as a failing device may be hidden from the view of the inspector. Propeller overhaul is strongly recommended to accomplish periodic internal inspection.

Visually inspect the wooden propeller blades for cracks. Inspect the hubs, with particular emphasis on each blade arm for cracks. Eddy current equipment is recommended for hub inspection. Since cracks are usually nor apparent.

Hoffmann Propeller will not be responsible for any translation of this manual. In case of doubt only the original English version of this manual will be valid and accepted.

Revision A 61-11-01 Page II April 2008


AIRWORTHINESS LIMITATIONS

1) General

The Airworthiness Limitations Section is FAA approved and specifies maintenance required under Parts 43.16 and 91.403 of the Federal Aviation Regulations unless an alternative program has been FAA approved.

2) There are no life limited items in the propellers covered by this manual.

FAA APPROVED

by:

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Record of Revisions to this Manual

Rev. No.

Issue Date

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Issue Date

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Content

Chapter Page

1 General 1-1 2 Designation 2-1 3 Design Data 3-1 4 Construction 4-1 5 Reassembling the Propeller 5-1 6 Installation and removal of the Propeller 6-1 7 Operation 7-1 8 Inspection 8-1 9 Troubleshooting 9-1 10 Maintenance and Repair 10-1 11 List of Consumable Materials (CM) 11-1 12 Storage and Shipping 12-1 13 Cutaway Drawing and Special Tools 13-1

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List of Illustrations

Figure No.

Title Chapter Page

2 -1 Model Designation System 2 1 2-2 Blade Model 2 2 2-3 Blade Decal 2 3 4 -1 Leading edge erosion protection 4 2 5 -1 Needle cage installation - Wrong installation 5 2 8 -1 Normal Erosion 8 2 8 -2 Separation in the Silicone material 8 2 8 -3 Blade tipping type A 8 3 8-4 Blade tipping type B and type C 8 3 8-5 Transverse crack 8 4 8-6 Lengthwise cracks 8 4 10 -1 Repair of leading edge type B 10 2 10 -2 Damage in the erosion painting 10 2 13 -1 Cut away drawing 13 3

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1 Introduction

The Propeller HO-V 373 () is a 3-bladed variable pitch propeller with hydraulically controlled pitch change mechanism using a dual acting hydraulic system. This means the propeller is using oil pressure to increase and to decrease pitch.

Hydraulic pressure oil is supplied from an external source. Control is maintained by a "Beta-Valve" (Hoffmann). Each position of the "Beta-Valve" corresponds to one defined pitch angle. The travel of the propeller blades is limited by internal mechanical stops.

The position of the “Beta- Valve” will be adjusted by an actuator for the “Beta-Tube” which is an aircraft part.

In the event of an oil pressure failure the propeller blades automatically return to the zero thrust position. This means the propeller will not produce any thrust.

For special applications the propeller can be equipped with counterweights. In this case the counterweights will turn the propeller blades towards coarse pitch and the flight can be continued with reduced power.

Changes to the Instructions of Continous Airworthiness (ICA) according FAR 35, Appendix A, A35.1 (c) will be announced on Hoffmann Propeller GmbH Homepage (www.hoffmann-prop.com).

Revision A 61-11-01 Page 1-1 April 2008


2 Designation Designation Hub

HO- V 37 3 ( ) - ( ) () () / Blade Model 1 2 3 4 5 6 7 8

1 Hoffmann GmbH & Co. KG

2 Variable pitch propeller

3 Number of basic model

4 Number of blades

5 Designation of flange

Blank See H-flange

F ARP 502 Type 1 flange

H ARP 502 mod. ½” -20UNF studs, 4.75” bolt circle

K SAE No:2 mod.3/4” bushings ½”-20 UNF bolts

6 Number of hub extension from blade axis to flange

Blank 172 mm

7 Blank No counterweights, non feathering, oil pressure to increase pitch

D Dual acting oil pressure F Counterweights installed S Feathering R Reverse V Oil pressure to decrease pitch

8 Minor changes, not affecting interchangeability This model designation and the serial number of the hub are stamped into the hub. Additional model information: Application to a specific vessel can be marked on the blade decals. This number, if present, beginning with VP20 - (), defines all information on material, adjustment, detaching parts and so on, for the specific application.

Model Designation System (Example only) Figure 2-1



Designation Blade

D 270 FU - ( ) ± ( )

9 10 11 12 13

9 Sense of rotation: Blank: right-hand, tractor D: right-hand, pusher L: left-hand, tractor LD: left-hand, pusher

10 Basic diameter in cm

11 Key letters for blade design

12 Material of blade Blank: compreg / spruce P : compreg

13 Decrease (-) or increase (+) of basic diameter in cm

On a decal on each blade the designation of the hub assembly and serial number, as well as the designation of the blade and serial number are printed. The serial number of the blade is additionally stamped into the blade retention nut and the blade ferrule (not visible from outside).

The complete designation of a variable pitch propeller is a combination of the desig-nation of the hub assembly and the blade assembly. Both designations are separated by a slash mark.

Example: HO-V 373 () - D()R / D 270 FU

The serial number of the hub is considered to be the serial number of the complete propeller assembly.

Blade Model (example only)

Figure 2-2



Blade Decal (example only) Figure 2-3



Warnings, Cautions and Notes

Throughout the text in this manual, Warnings, Cautions and Notes pertaining to the procedures being accomplished are included. These adjuncts to the text are used to highlight or emphasis important points. Warnings and Cautions precede the text they pertain to, and Notes follow the text they pertain to.

Warning: Calls for attention to the use of materials, methods, processes, procedures or limits which must be followed precisely to avoid injury and / or death to persons.

Caution: Calls attention to methods and procedures which must be followed to avoid damage to equipment.

Note: Calls attention to methods which will make the job easier.



3 Design Data

Following data are standard values only. For installation purposes only the data given in the Type Certificate Data Sheet (TCDS) No. 32.130 / 96 of the German Luftfahrt - Bundesamt (LBA) are valid.

kW (HP) max. 149 (200)

RPM max. 1250

Number of blades 3

Diameter 2.70 m

Pitch change range About 70° (forw. + rev.)

Weight: (without counterweights) About 37 kg

Weight of the spinner: Aircraft part

Polar moment of inertia, approx. About 5,9 kgm2

Governor: Beta System



4 CONSTRUCTION

The HOFFMANN variable pitch propeller consists mainly of 5 sub assemblies:

- Hub assembly - Blade assembly - Counterweight assembly (If applicable) - Beta-valve assembly - Spinner assembly (if applicable)

The HO - V 373 () uses a beta-valve to control the oil flow to change the pitch.

4.1 Hub assembly and pitch change mechanism The material of the hub is forged aluminium alloy. One side of the hub has a flange which fits to the drive shaft flange. Bolts and self-locking nuts secure the hub to the propulsion shaft. The piston and pitch change assembly of the HO-V 373() propeller is installed on the opposite side of the hub. The axial movement of the piston is turning the blades by a fork and pitch change blocks which are engaged to eccentric blade actuating pins in the blade ferrules. The propeller has mechanical internal emergency stops for reverse and high pitch. The maximum pitch of the propeller has to be limited by the travel of the beta-tube. Oil pres-sure works in both directions and can be assisted by counterweights. In case of oil pressure loss, and the propeller running, the propeller blades will change pitch automatically towards the zero thrust position. After normal engine shut down the propeller blades remain in the position they had prior shut down.

4.2 Blade Assembly The HOFFMANN composite blade is a joint construction. It uses totally compressed hardwood (compreg) in the root part and spruce in the remaining part of the blade. Blades can also be manufactured of compressed wood only. The wooden core is covered with several layers of fibre reinforced epoxy resin, which adds torsional strength and offers resistance to impact of particles entering the propeller disc. For erosion protection the leading edge is covered by a metal (Type A or B) or polyurethane sheet (Type C), which is replaceable. Connection to the hub is possible by means of a metal ferrule, which is connected to the compressed blade shaft by specifically designed well proven lag screws.



The blades are fixed into the hub by blade retention nuts manufactured of aluminium alloy. Pre-load of the blade bearing is obtained by applying torque to the blade retention nuts in the hub. The blade retention nuts are sealed against water from outside with silicone rubber between the retention nut and the hub. A blade seal of neoprene rubber prevents grease leaks and penetration of moisture to the blade bearings. The blade root is sealed against the metal ferrule with silicone rubber, to prevent moisture penetration between the metal ferrule and the blade root. An axial needle bearing absorbs the centrifugal force of the blade. The bearing races are made of steel. The needle cage is split into two halves to allow replacement of the cage without removing the blade ferrule from the blade body. Fatigue failures due to vibration are unlikely with such blades because of the internal dampening of the material, which is considerably higher than that of aluminium alloy or plain fibreglass construction.

Fig. 4.1 Leading edge erosion protection Type A Type B or C

4.3 Spinner Assembly (Mainly manufactured by the craft-builder) The spinner assembly consists of a spinner bulkhead and a spinner dome, which are screwed together. The spinner assembly can be made of aluminium or FRP.



5 Re-assembling the Propeller

(when the blades have been removed for shipment) (Index numbers relate to the assembly drawing in chapter 13)

Caution

A propeller shipped with blades removed must be re-assembled in a facility approved by HOFFMANN

Propellers which have the blades removed for shipment will have identifying numbers on the blade decals. They indicate the appropriate hub socket.

Caution

Before performing the next step make sure all protective covers of the hub assy are removed

Note

Index numbers relate to the assembly drawing

Warning

MEK (Methyl Ethyl Ketone) weakens the paint of the Propeller Blade and the sealing

5.1 Clean the mating surface of the hub assembly (1.1) carefully using solvent and install it onto the assembling fixture or install it on the craft according chapter 6 of this manual.

5.2 Prior installing the blades clean the inside of the hub very carefully using a clean cloth and solvent. Also clean the inside of the three (3) canals of the fork (1.22).

5.3 Prepare the blades for installation. Mark the position and amount of the balance weights (1.39) (if applicable) relative to the blade retention nut (2.1.2) and remove the weights. Remove the protective cover from the blade root. Clean the threads of the blade retention nut (2.1.2), the bearings (1.33, 1.35) and the needle cage (2.3) using solvent. Apply new grease to the split bearing cages (2.3) using CM 1 (or equivalent) and install them between the two thin races. Apply a very thin film of grease to the inside of the canals of the forks (1.22) and on the threads of the blade retention nut (2.1.2).



5.4 Turn the hub that the No. 1 (stamped into the hub socket) blade socket is in the 12:00 o'clock position and prevent the hub from turning. The blade No. 1 has to be installed vertically. Apply new grease using CM 1 (or equivalent) to the bearing cages (1.34) and put one thin race (1.33) on each side of the lower needle bearing cage (1.34) and install it. Slide the marked pitch change block (1.21) into the canal of the fork (1.22). On the outer side of the pitch change blocks (1.21) is an arrow and a number. The No. corresponds to the blade number and the arrow has to point in direction of movement of the craft. Position the block so that the pitch change pin (2.1.6) in the blade can engage the hole of the pitch change block (1.21).

Caution

Make sure the lip of the lip seal does NOT touch the groove of the counterweights.

Warning

Make sure the split needle cage (2.3) is in the correct position. Do not damage the threats

of the hub and the blade retention rings.

5.5 Install blade No. 1 (marked on the blade decal in front of the blade serial number), vertical into the hub. During installation hold the blade retention nut (2.1.2) away from the bearing (2.3). Make sure the blade rests against the lower thrust bearing (1.34) and the pitch change pin (2.1.6) engages the hole in the pitch change block (1.21).

Fig. 5.1 Wrong installation of needle cage



5.6 Turn the blade retention nut (2.1.2) by hand, clockwise (facing the blade retention

nut), into the hub for the first turns. Continue using the wrench PV-855. Be careful and avoid any seizing. The nut is in the correct position when the upper surface is flush with the bottom surface of the slots in the hub socket for the lock plates. Torque the blade retention nut (2.1.2) to 40 Nm (354 inlbs). Grease and trapped air sometimes indicate high friction. If the blade retention nut cannot be screwed into its final position easily, remove the whole blade and check the position of the cage halves (2.3) (Fig. 5.1). Install the remaining blades in the same way (step 5.5 and 5.6). Check the blade angles at the reference station (yellow line on the thrust face). The blade angles must be within ±10 minutes.

5.7 After all blades have been installed, recheck the torque of the blade retention nuts (2.1.2). Very carefully clean the outside of the blade retention nut, and the hub socket using solvent. Make sure no grease or dust is left. Trim the lock plates (1.32) by drilling 2 holes, if not yet done, to screw the plates onto the blade retention nut. But do not install the lock plates yet. Put a self-adhesive tape on the blade retention nut (2.1.2) around the blade ferrule (2.1.1), about 2 cms away from the hub socket and fill the gap (joint) between the hub socket and the blade retention nut using CM 2 (or equivalent) until the tape is reached. Install the lock plates (1.32) as long as the sealant is soft using the screws (1.31) and washers (1.15) and torque them to 3 Nm (26.5 inlbs) to the corresponding blade retention nuts (2.1.2), and wire lock them.



6 Installation and removal of the propeller

6.1 Installation

(Index numbers relate to drawing in chapter 13)

Warning

MEK (Methyl Ethyl Ketone) weakens the paint of the Propeller Blade and the sealing

6.1.1 Clean the flange of the propeller shaft and the propeller flange from oil and dirt with solvent. Remove sharp corners.

Note

The engine torque is mainly transferred by friction, therefore the flange has to be dry and clean .

6.1.2 Check if the O-ring (1.4) is installed and undamaged in the centre ring. Make sure the centre ring (1.3) is in the correct position.

Warning

Do not install an additional O- ring on the propeller shaft. Make sure the dowel pins engage the correct holes.

6.1.3 Apply a small amount of oil to the O- ring (1.4) and slide the propeller carefully onto the propeller shaft. Take care not to damage the O- ring in the centre ring (1.3)

6.1.4 Install washers (1.26) and the stop nuts (1.27) and torque them cross wise (running torque) to 80 - 90 Nm (765 - 780 inlbs.) dry threads.

6.1.5 Check the track of the propeller blades on the trailing edge about 10 cm inboard of the blade tip. Maximum permissible track is 3 mm.



Warning

Do not install an additional O- ring on any position of the Beta- Tube

6.1.6 Check if the O-ring is installed in the beta-tube support housing (not a Hoffmann part) and apply a small amount of oil to the o- ring.

Caution

Take care not do damage the o-ring in the beta-tube support.

6.1.7 Prepare the beta-tube (6.()) for installation. Remove the cover from the beta-tube and clean it very carefully (inside and outside). Apply a thin film of oil on the whole length of the beta-tube.

6.1.8 Prior installing the beta- tube turn the propeller blades several times by hand from the reverse stop to the high pitch stop position, to make sure the blades will turn free. (Using a turning bar very close to the blade root.)

Caution

Be extremely careful while installing the Beta-Tube not to damage or scratch it.

6.1.9 Carefully install the beta tube (6.()) and connect it to the linkage (not a Hoffmann part).

Warning

Take care not to bend the Beta-Tube while performing the hydraulic connections.

6.1.10 Make all necessary hydraulic connections.

Warning

Make sure the pre-set hydraulic pressure is at the correct level.



6.2 Removal of the propeller

Caution

The following work may be performed by HOFFMANN trained personnel only!

Caution

Take adequate precautions to protect the propeller assembly from damage when it is removed from the craft

and when it is transported or stored.

Note

Prepare a suitable container or bucket to drain the oil.

Caution

Be extremely careful while removing the Beta- Tube not to damage or scratch it!

6.2.1 Disconnect the linkage to the beta-tube.

Warning

Take care not to bend the Beta- Tube while disconnecting the hydraulic pressure hose

6.2.2 Disconnect the hydraulic pressure hose from the beta-tube (6.() ) and drain the oil into a suitable container.

6.2.3 Pull the beta-tube (6.() ) very carefully out of the propeller and drain the oil in suitable container.

6.2.4 Cover the beta-tube with wax-paper or equivalent and store it in a suitable container.

6.2.5 Remove the six nuts (1.27), washers (1.26 ) and discard them.

6.2.6 Pull the propeller off the shaft and allow the oil to drain into the prepared container.

6.2.7 When the oil flow stops remove the propeller from the drive shaft.

6.2.8 Turn the propeller up side down to drain the remaining oil.

6.2.9 Protect the propeller for reuse, storage or shipment.

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Revision A 61-11-01 Page 6.2-4 April 2008


7 Operation

Warning

During normal operation the propeller must not reach the internal hard stops. the maximum pitch has to be limited by the maximum travel of

the Beta-Tube

Warning

Make sure the pre-set hydraulic pressure is at the correct level.

Warning

Prior operating the propeller, make sure every screw, bolt or stop nut has the correct torque and everything

in front of the Propeller is clean and secured. Take precautions according the craft's manual.

Pitch control is selected and maintained by the "Beta - Valve" in the whole pitch change range. The dependence of the blade angle and the beta valve position can be described by the following equation:

ß = arc sin X / 36.5

ß = blade angle at 0.75 R

x = motion of beta valve from position which corresponds to 0° blade angle (mm)

Warning

Move the power - and propeller levers smoothly! Do not operate the levers abruptly!

Carefully follow the instructions given in the aircrafts manual

7.1 Place the propeller lever in the cockpit in the "NEUTRAL" position. Start the engine according the crafts manual and warm it up. Slowly increase the power to get a propeller rpm increase of about 200 rpm. Move the propeller lever slowly towards full forward pitch and back to full reverse. Pay attention not to stall the engine. Cycle the propeller at least three times to remove the air from the hydraulic system.



7.2 Increase the power (be careful not to over speed the engine) in steps and cycle the propeller in steps until reaching full power. The crafts manual may contain additional information.

7.3 After the static run up inspect the propeller and the hydraulic system for oil leaks and possible damage and the blade retention system for grease leaks or any other abnormalities.

7.4 Re-torque the stop nuts (1.27) of the propeller bolts (1.1.2) by applying the correct torque only. Do not release the torque before.



8 Inspection

Warning

Do not use the propeller as a handle to move the aircraft!

Warning

Before performing any work on the propeller follow the safety precautions given in the flight manual

Note

There are no life limited items in the propellers covered by this manual

8.1 Daily inspection Check blade installation. No blade shake is allowed. Blade angle play up to 1° is permitted. Check the propeller for loose screws and safety wires, the blades and the propeller spinner for cracks and damage. Turn blades by hand to check for smooth pitch change. Check the correct position of counterweights, if installed.

8.2 100 hour inspection To be carried out every 100 hours until "TBO" is reached.

8.2.1 Remove spinner dome. Perform daily inspection. Check flange bolts for correct torque by applying the required torque only. (Do not loosen the bolts before.) Check for oil and grease leakage. Check the sealing of the blade retention nuts. If damaged, repair with silicone rubber.

8.2.2 Inspection of the blades. Clean the blades. The Inspection of wooden composite blades is easy and gives reliable results. Critical conditions will show up early as surface cracks in the paint. Therefore correct judgement of such cracks is very important.



8.2.2.1 Erosion on the leading edge of the blades is normal and not critical. Metal

propellers erode too. On a composite propeller the erosion sheet (Type A and B) becomes visible under the paint.

Fig. 8.1 Normal erosion, no matter for concern

8.2.2.2 The area around the blade root between blade body and metal ferrule is sealed with silicone rubber. No cracks in the silicone rubber and No separation from the metal ferrule or the blade body is permitted. A crack might indicate that the blade got loose in the ferrule. The propeller has to be removed from service immediately!

Fig. 8-2 No separation permitted. Contact HOFFMANN



8.2.2.3 The erosion tipping (Type A)of the propeller blades ends in the inner third of the

blade. Fine cracks in the paint along the tipping are no reason for concern.

Fig 8-3 Blade tipping type A

8.2.2.4 The erosion tipping (Type Band C) ends in the inner third of the blade. Fine cracks in the paint along the metal tipping (Type B) are no reason for concern. Cracks in the metal perpendicular to the blade axis are not dangerous as long as the metal does not lift off from the blade body. Slide your fingernail along the leading edge from the hub to the tip. If the metal lifts off from a crack, remove propeller for repair.

Fig. 8-4 blade tipping type b and type C



8.2.2.5 Fine cracks in the paint or the tipping across the blade axis, especially in the outer third of the blade, are indications of bending vibration. In an advanced stage the tipping may break or come off piece by piece. Notches in the metal support this procedure. If such cracks occur, contact the factory or an authorised service station.

Fig. 8-5 Transverse crack. Contact HOFFMANN

8.2.2.6 Cracks in the paint or in the blade, starting from the blade tip and extending parallel or at any angle to the blade axis, are indications for torsional vibrations. Such cracks occur very seldom. If such cracks occur, contact the factory or an authorised service station.

Fig. 8-6 Lengthwise cracks



8.2.2.7 Damaged fibre cover

Normal stone nicks are unimportant as long as the wooden core is protected. Air bubbles, or any other bubbles, with a maximum diameter of 1.5 cm (0.6 inch) are unimportant, if the size does not increase during operation. Scratches and nicks should be protected with water resistant paint during routine maintenance.

8.3 Additional periodic inspections New propeller-engine-aircraft combinations may require additional periodic inspections between overhaul, such as partial disassembling and inspection of the thrust bearings. These inspections have to be carried out in the factory or an authorised service station

8.4 Overhaul The "TBO" (time between overhaul) is normally the same as for the engine, but should not exceed the figures of HOFFMANN Service Bulletin No. E 1(), latest edition. Overhaul must be carried out in the factory or an authorised service station.

8.5 Special inspections

8.5.1 Special inspection is required if the max. rated propeller speed according the "TCDS" (LBA - Kennblatt) has been exceeded by more than 10%. If the over - speed was above 20% of the max rated propeller - speed, the propeller has to be removed from service. Repair is not possible. These propellers have to be marked as rejected.

8.5.2 Special instructions may be necessary for unconventional installations. A conventional installation is a tractor installation on a single engine aircraft.



9 Troubleshooting

TROUBLE PROBABLE CAUSE REMEDY

Blade shake Blade bearing loose Tighten retention nut to 40 Nm (354 inlbs.).

Sluggish pitch change 1. Excessive friction 2. Oil pressure and / or - flow

too low

1. Inspect the blade retention system

2. Check the oil supply and / or oil transfer openings and tubes

Surging pitch change 1. Trapped air in the propeller piston

2. Excessive friction 3. Abrupt movement of propeller

or throttle control 4. Oscillating tachometer 5. Sludge deposit

1. Cycle the propeller at least 3 times from full forward to full reverse

2. Proceed as described above

3. Move the controls carefully and slowly

4. Check tachometer and drive

5. Clean propeller, beta valve, cylinder and oil pipes

Oil leakage Worn O-rings Replace defect O-rings



10 Maintenance and Repair

10.1 All moving parts of this propeller are inside the propeller hub and normally not affected by environmental influences. No relubricating is necessary between the overhaul periods. During the periodic inspections, the surface of the hub and all metal parts should be free of corrosion and any kind of damage and should be protected.

10.2 The paint on HOFFMANN composite blades is resistant against fuel, oil and nearly all solvents. The propeller should periodically be cleaned with any gentle detergent or equivalent and protected with car polish, that doesn't contain silicone. The surface protection (lacquer and epoxy fibre glass) should be completely sealed to prevent penetration of moisture into the wooden core. In special case contact an inspector with appropriate license to assure safe operation.

10.3 Minor damage (small scratches etc.) can easily be repaired. Prior to repair check that the fibre glass covering and the wooden core are not damaged. The materials required for repair can be obtained from HOFFMANN. Proceed as follows:

10.3.1 Clean damaged area with solvent and polish with emery cloth # 220.

10.3.2 If required, apply filler of epoxy resin to fill the bulges. Do not apply too much filler.

10.3.3 Allow filler to dry. Polish the surface with emery cloth # 220 again.

10.3.4 Apply paint (white, grey, black or yellow). It is recommended to use original paint, because resistance and bonding of other paints cannot be guaranteed. Observe the drying times if several coats are applied.

10.4 Presently repair of HOFFMANN composite blades can only be carried out in the factory. Blade tips can be repaired if 90% of the blade remains free of cracks. Trailing edges can be repaired, the fibre reinforced epoxy covering and the erosion tipping can be replaced.



10.5 Sharp nicks in the leading edge of Type B have to be blended out similar to the method used for metal propellers.

Fig. 10-1 DON’T FILE TOO DEEP (Attention: The erosion protection is only 2 to 3 mm thick.)

10.6 Any damage in the lacquer in the area behind the metal blade tipping has to be repainted immediately after occurrence. There must not be a joint between metal leading edge and blade body

Fig 10 – 2 Damage in the erosion painting shall be repaired immediately.



11 List of Consumable Materials (CM)

CM 1 Calypsol H - 443 Bearing lubrication CM 2 RTV 109 Sealing compound



12 Storage and Shipping 12.1 Shipping

Careful packing is the best protection against damage during shipment. Therefore the propeller will be shipped to the client with the blades removed in a few special wooden containers. The blades and the hub are fixed to the containers The blade tips and trailing edges need special protection.

121.2 Storage No propeller shall be stored standing on the tips. If storage is required, the best is the use of the original packing. Avoid extreme temperature changes.

Normally the propeller is not protected for a storage period of more than 6 months in dry rooms with normal temperature.

The aluminium parts are protected with chromatic acid anodising. The steel parts are cadmium plated or made from stainless steel. The blades are painted with polyurethane

No preservation is required for the blades. The metal parts can be protected with standard preservation mediums, if long term storage is required.

In cold weather condition, the propeller shall not be stored in rooms with large temperature changes or near to heating systems.



13 Cutaway Drawing and Special Tools

13.1 Cutaway Drawings

Propeller model HO-V 373 ()-()()()

13.2 Special Tools

For propeller blade installation the following special tools are required.

Propeller model:

HO-V 373 ()-()()()

Special Tools: PV - 855 Wrench for blade retention nut

13.3 Any equivalent, multipurpose, none synthetic aircraft grease may be used instead of Calypsol. The grease should be water resistant and corrosion protective.





Fig. 13.1 Cut away drawing


ho-v 373()() -d()r-() - hoffmann propeller · hoffmann propeller manual no. e709 operation and ......

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