1.    Introduction and Information


All the ground adjustable propellers manufactured by S-PROP are intended for operating with engines in power range from 30 to 130 hp, equipped with gearbox and/or dampener to absorb torsional oscillations.


The S-PROP Propeller Blades are made from composite on the basis of layered fiberglass and carbon fiber.

2. Design Description


The manufacture and design of our aircraft propellers represent a quality product consisting of blades and a two-piece hub with a cylindrical Center Insert. The blades are fixed between the two halves of the metal hub and tightened together by the

assembly hardware consisting of bolts, washers and locking nuts. It is then attached with six bolts. All required hardware is

included with each propeller order.

The pitch adjustment of each blade must be performed by qualified technicians prior to use. A small pitch indicator is attached to each blade.

3. Instructions for Assembly, Installation, Adjustment, Dismantling and Storage of S-Prop Propellers.


NOTE: Before beginning assembly, be sure that all blades have the same serial number.


Prop assembly must be on a flat, level, cleared surface. Make sure that the surfaces of the blade roots and area between the hub halves are clean with no dust or debris. Do not use cleaners that are corrosive (harmful to aluminum) or leave a slick or slippery surface.


a)  Lay down one half of the hub (which should be directed towards the engine) on the cleaned surface, with the inserted assembly bolts from below pointed upward. Place the root end of each blade into the machined groove of the hub half and then place the second hub half on top with the “0” marks aligned together.


IMPORTANT: The marks "0" on external surfaces of both halves must be aligned. Raise the bolts upward and install the washers and nuts. At this point, tighten just enough to pull the hub halves together. The blades must be free enough to twist and make pitch adjustments.


NOTE: Before installing the prop on the engine, please confirm the ignition circuits are in the OFF position!


b) Install the prop by centering on the gearbox prop flange and install at least 2 mounting bolts with washers and nuts. Tighten slightly enough to bring propeller assembly flush with the gearbox flange. Install the remaining bolts, washers and nuts with slight pressure to allow the twisting of blades inside the hub for pitch adjustment.


c) Rotate the propeller on the gearbox shaft to a convenient

position for pitch adjustment. Pull each blade outward of

the hub by hand to remove any possibilities of axial gap.

Adjust the pitch by aligning the desiredsetting, found on

Thepitch indicator (pictured). Slightly snug the two nuts,

allowingother blades to still turn by hand.

Adjust other blades the same way.


d)  Check the pitch on all blades again.

Any slight difference can cause a propto run

rough and vibrate.


e)  Tighten all nuts and fixing bolts in an incrementalcrisscross pattern.

Maximum Torque:8mm bolts = 25nm

6mm bolts = 10nm. (2-Blade UL propellers only)

NOTE: The gap between both half of hub must be equal all the way around. You should alsocheck propeller tracking.

IMPORTANT!!! Respect the recommended torque values. Use a properly calibrated torque wrench. Never over torque bolts, they will stretch and weaken.And too little torque will reduce clamping force and increase stresses on bolts.


f)  Refer to your engine manufacturer for recommended static RPM test. Secure aircraft, chock wheels and set parking brake before conducting the static rpm test (run-up). Tail Wheel aircraft should hold up elevator during rpm check. Start and warm up the engine. Slowly advance throttle to maximum static RPM’s.


RPM Reads Low:

Too much pitch. Reduce the pitch by one increment or less and test again.


RPM Reads High:

Not enough pitch. Advance the pitch by one half increment or more and test again.


Important:  Never exceed the maximum RPM’s of the engine manufacturer.


g)  Once satisfied with the final pitch adjustment, secure all bolts with safety wire (when locking holes are available) or jam nuts on bolts that thread into the propeller flange.


                                    Dismantling of assembled propeller can be carried out by reversal of assembly order.


Propeller Storage

The prop should be stored in a cool dry area.


The removed assembled prop should be storable in vertical position, hanging on a central hub hole, or be installed on the aircraft engine, far from places with probability of damage.

Blades of disassembled prop must be stored in horizontal position on an equal surface with a soft substrate or in covers.

After a rainfall, propellers on aircraft stored outside with protective covers should have them removed and set somewhere to dry.

                                                A dismantled propeller must be transported in dismantled condition.



4.  Frequency of visual inspections and a preflight and post-flight inspection must be carried out with a visual survey of the installedprop for detection of external damages.


1) Clean the prop when it is necessary.

2) Adjust the blades pitch when it is necessary, depending on weather conditions and flight tasks. 


Annual or 500-hour Inspection:

Make inspections of the prop by disassembling each year and recording in log book.


Annual inspection with disassembling includes:

- Visuallyinspectfor feather like cracks and any defects on the

root of each blade;

- Visuallyinspectthe hub for visible cracks, deformations and for corrosion damage;

- Visuallyinspectall bolts for deformations of threads, wear, bends and corrosion damage.


Admissible Damages

a)  Small scratches, dents on leading edge protection, which does not causelifting of its edges from the blade structure, which are not deforming the border line between the edge material and blade structure and not leading to local damage along the border;


b)  Scratches and dents on the surface of blade without cracks and rough edges.

c) Longitudinal scratches up to 100 mm in length and depth of up to 0.4 mm at a distance of 200 mm or more from the place where the blade is attached.

d.) Transverse scratches of up to 30 mm in length and depth of up to 0.3 mm at a distance of 200 mm or more from the place where the blade is attached.

e.) Dents on the leading edge of a depth of 1 mm.

f.) Dents, depth up to 1.5 mm and length 4 mm, on polyurethane blade protection.


g.)  Dents on surface of a hub during operation or negligent maintenance with depth that not exceed 0,5 mm.

5.  Fault Detection


Fault detection for blades of "S-Prop" can be carried out only by a method of the visual inspection.

At fault detection for metal parts the base method is a visual survey. At detection of suspicious defects or damages on metal parts where level of danger cannot be defined visually, any other standard method of detection (ultrasonic, x-ray) can be applied.

A distinctive feature of a blades designed by "S-Prop" is that any damages which could bear a threat for the safety which have been not caused by external factors, do not develop instantly, but let know beforehand in change of operating characteristic of the prop and can be detected at daily visual survey.


Inadmissible Damages

- Dents and ruptures or cracks on protected edges which create a flaking on the edges from the blade structure;

- Dents and ruptures or cracks, on the blade surface, which have created a chip, thickening or hump in the field of blow or the warping of a border line between leading edge protection and blade;

- Scratches, dents and cracks with frayedand/or fluffed up edges, which indicates damage of the reinforced layers.

- Transverse cracks on surface in length over 30 mm in length and depth of up to 0.3 mm at a distance of 200 mm or more from the place where the blade is attached.

- Any longitudinal cracks on surface, in length over 100 mm in length and depth of up to 0.4 mm at a distance of 200 mm or more from the place where the blade is attached.

- Any cracks on a hub which are visible on mechanically processed surfaces inside and outside;

- Corrosion damage of a hub with depth more than 0.5 mm;

- Elongation or any other deformation of bolt body or thread and/or corrosion damage.


6.  Instructions on repair and replacement of parts and components of propellers


For damages described in section 4, items (a, b, c, d, e, f, g): repair is not required. Operation of the prop without repair is admissible.


At detection of damage described in section 4, item (g): mark by marker the edges of crack and observe its development during operation. At further growth or expansion of crack the prop operation must be stopped. Here consultation with manufacturer is necessary with giving of detailed description and photos of damaged place.


At detection of seat of corrosion on hub, please, make a deepening in this place with the ratio 1/10 of the depth to the width up to full removal of signs of corrosion with radius of deepening not less than 4 mm. Then cover this place by anti-corrosive primer. If depth of deepening will be more than 0.5 mm, please, address the manufacturer for consultation, giving the description and a photo of the damaged place.

Inadmissible Damage


All details and the components of the prop having damages, described in section 5, in the list of inadmissible damages are subject to replacement only, repairs are not allowed.


To replace the damaged components: remove and disassemble propeller in accordance to section 3 of this manual.



7. Recommendations and Preparations for Storage


-        Remove and dry the protective blade covers before storage.


-        Wash the blades and hub carefully with cleaners which do not contain abrasives, acids or alkalis.


For removal of difficult dirt and grime, gasoline can be used with cautionand only outdoors. Use of solvents is inadmissible.


Aircraft stored outside should have S-Prop blades protected from solar radiation with covers.


   DO NOT store or transport assembled propeller vertically (standing on blades) and in horizontal position, under weight of extraneous subjects.


8. Limitations of Airworthiness.


Manufacturer establishes limitation of calendar service life «on condition» - 6 years from initial date of service for all ground adjustable propellers "S-Prop" including a storage time.

Limitation of operating time is 2000 hours.

After ending of calendar service life or limitation of operating time manufacturer can make decision about its prolongation for a serviceable prop with giving of respective document, after giving by the owner of description and photos, confirming a good condition and preservation of all components and details of prop. Manufacturer establishes terms of prolongations on the own discretion in each separate case, in accordance to data of condition of concrete prop.


Period between inspections with full disassembling of the prop is 1 year.


Use of propellers manufactured by "S-Prop" with direct drive engines is RESTRICTED!


Maryland office:


5223 Bucktown Road

Driveway E, Hangar 1, Suite 2

Cambridge, MD 21613







Fax: available on request

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