THE V-530 PROPELLER

by George S. Coy

The V-530 propeller that we find as original equipment on the M-14 powered yaks and Suhkoi’s is an outgrowth of a basic propeller design that dates back into the 1930’s. The M-14p version has a serrated flange drive that is unique. The earlier versions were a splined shaft drive. The basic design is the same. The propeller is currently manufactured by the VPERIOD MACHINERY CO. in Moscow. They have been producing them for many years. This factory used to employ thousands of people, but at present is down to a few hundred. They manufactured a line of commercial pumps, as well as aerial refueling pumps, helicopter tail rotors and other machinery. They also manufacture under license the Mulbauer MTV-9 three blade propeller. They supply parts for this propeller to the German Mulbauer facility. Its commercial director, Mr. Valintin Pinchuck, has been to the United States several times in the last few years trying to find more business for their facility. They have a lot of capability, and are one of the more “westernized “ companies that I have visited there. They plan to be at Oshkosh with a new blade design for the propeller.

The V-530 is a two bladed constant speed design with composite ( wood laminate ) blades. It uses engine oil pressure to coarsen the pitch, and counterweights to flatten the pitch. The internal moving parts are not lubricated with engine oil. This necessitates that the propeller be regularly disassembled and lubricated. We recommend that this be done every annual or every 100 hrs. of operation.

The propeller due to its wooden construction and its propensity to absorb moisture also needs balanced regularly.

PROPELLER DISASSEMBLY

The propeller is easily disassembled for lubrication while installed on the aircraft.

First, the spinner dome is removed by removing the large cotter pin on the front of the propeller and then the spinner retaining nut. The spinner is usually lined with felt.

Next remove the hydraulic piston and cylinder assembly. This is done by cutting the safety wire at the cylinder tab retainer screw and then removing the screw and cylinder retainer tab. The cylinder retainer tab is a piece of aluminum that keeps the cylinder assembly from rotating in the prop hub. After the tab is removed, rotate the cylinder until its teeth line up with the gaps in the hub assembly and pull the cylinder assembly out of the hub. At re-assembly, it does not matter which tab lines up, they are all the same. We have found that not all cylinder assemblies are interchangeable. There seems to be an older style from the early eighties that has smaller teeth.

At this point it is easy to feel if the propeller is binding. Grab the two counterweights and rotate the blades. They should rotate smoothly. Grab the tip of the blade while the prop in the flat pitch position and try and move the blade fore and aft. There should be no movement. If movement is observed, then the hub is a candidate for overhaul.

There are only three places that engine oil can leak from this propeller. They are the two rubber seals that are in the cylinder assembly and two paper gaskets behind the oil transfer snout. The cylinder assembly is disassembled by pulling the piston out of the cylinder. After cleaning in clean kerosene examine the cylinder internal bore for evidence of wear. Large scratches or wear beyond the alodine coating may cause oil leaks even with a new seal. It is sometimes possible to save these cylinders by polishing with scotch bright or fine crocus cloth. Examine the seals in the piston assembly. The large ( approx. 5 inch ) seal and the small ( approx. 1 inch ) seal should both be in good condition with the open part of the seal “V” pointing toward the front the cylinder. It is a little difficult to start the large seal in the cylinder bore, but start one edge and work it around. I usually pack both seal “v” surfaces with a little white lithium grease to pre lube them. The other place that you will experience oil leaks is the two gaskets that are sandwiched between either side of the oil transfer disc behind the oil transfer snout. The oil transfer snout is the device that screws into the propeller flange. It is copper plated except at the end of the snout, where it is ground and polished. The small seal in the piston in the cylinder assembly moves back and forth over the ground area of the snout. If you have an oil leak, or are changing propellers it will be necessary to remove the snout. This is easiest done with the propeller removed from the engine. We will cover this later.

If you are planning to lubricate the propeller mechanism, it is now necessary to remove the blades. Carefully examine the blades, counterweight assemblies, the blade retaining nuts and the locking tabs. They should all have a number 1 or 2 stamp. That is blade no.1 and all its parts will be stamped with a 1 and likewise for blade no. 2. If they are not so marked, mark them now. Also carefully examine the position of the blade in the hub. There are little graduation marks on the bearing retainer under the blade retaining nut that has a “ 0 “ mark and some graduations in each direction. The blade shank has a witness mark on it that should line up with one of the graduations. It would pay to also use a sharpie marker or similar to make a redundant line as a backup reference. Both blades should be at the same marks. This is how the fine pitch blade angle is set.

The blades are removed by removing the cotter key at the nut at the back of the counterweight / clamp assembly. Loosen the nut / bolt and thus the clamp. Grab the blade and unscrew it from the hub in the normal thread direction. (rightly tightly lefty loosey) Repeat for the other blade. You can now see in the hub and see if you can get away with packing a little grease in at this point, or if it will need further disassembly. There are three areas that need grease. The main collar that moves back and forth, this has an internal fiber bearing that you cannot see. Make sure that there is a good film of grease on the large diameter polished shaft that the collar slides on. This collar also has two ( one on each side ) curved cut outs that the blade retainer pin and shoe bearing ride in. These should also be packed with a little grease. Finally, put some grease just inside the blade bearing collar ( the part the blade screws into ) this will work out and hopefully lubricate the blade roller bearings.

If the prop was tight ( i.e. the blades did not rotate freely by grasping the counterweights and rotating them after the cylinder assembly was removed ) you will need to disassemble the hub further. First remove the counterweight clamp assemblies by completely removing the nut and bolt. Spread them with a screw driver or cold chisel just enough to slide them off the blade bearing assembly. Next remove the two blade retaining nut locks. These are held with two safety wired screws. They are labeled 1 and 2 for their respective blade. Now remove the blade retaining nuts. These are the large toothed units on the hub. Here I made a special spanner by torch cutting a piece of ¼ inch steel plate into a half circle the same diameter as the blade retaining nut about 8 inches in diameter. I left a tab at one end of the half circle and welded a 4 foot section of 2 inch pipe on the other end. This produced with a little grinding for a good fit of the tooth and radius, spanner type wrench that removed the nuts. They are usually quite tight. It also allowed tightening them at reassembly back to where it allowed the retaining nut safety clamp to fit properly. After the nuts are removed, remove the blade bearing assembly. Note how the pin and shoe bearing fit together and engage the sliding collar. Disassemble and clean the thrust bearings. Note at assembly that one side of the race has a bevel on it that should face away from the roller bearing. This allows the races to seat in the castings freely. You will see also that there is a blade “ v” type seal that is supposed to retain the grease. I have found that these are not very effective, and that for the first 5 to 10 hours after lubricating the prop, grease will run out these shank seals and leave streaks on the prop. That is just the way it is. Lubricate the roller thrust bearings with a good grade of grease. I usually use a molibinum base high temperature wheel bearing grease.

As they say in all the manuals simply reverse the disassembly procedure, and voila’ you are done. Caution, make sure that when tightening the blade clamp / counterweight assembly that you slide it out radially on the blade bearing assembly until it butts up to the retaining lip on the blade bearing assembly. You will have balance problems if they are not set up against the lip. When putting the blades back, simply screw them in as far as they will go and back out until you align your witness marks.

Blade inspection should be performed at every preflight and when the propeller is being serviced. Small cracks between the protective metal leading edge and wooden blade are normal, so long as the wood does not appear to be puffing out. This cracking is due to the wood and metal expanding and contracting at different rates due to temperature and the moisture content of the wood. Moisture is bad for these propellers, therefore do everything in your power the keep the propeller dry when not in flight. It is beneficial to the propeller to keep the propeller horizontal and covered if the aircraft is to be tied down outside. If puffing is observed then the blade must be evaluated by someone knowledgeable to determine its airworthiness and repair. Cracking around the base of the blade where the wood meets the metal hub is ok so long as there appears to be no pulling out of the wooden blade from its metal hub. If any pulling out is observed then the propeller must be evaluated before the engine is run-up. We have observed cracking in the wood laminate at the transition between the airfoil section of the blade and the metal hub. These cracks look like small curves on the surface of the blade, about 2 to 3 inches long, where the fabric covering has been stretched. If you observe anything that looks like this on your blades then it must be evaluated before the next engine is run-up. If the crack is due to delamination then the blade is unairworthy and must be replaced.

SOME OTHER NOTES:

To remove the hub, straighten the tabs at the six nuts at the back of the flange. Remove the nuts and pull the hub off. It has a short alignment pin so it will only go back on in one position. To remove the snout, simply unscrew it. It is best to use the special Yak tool as it is important not to bend the snout. There is an aluminum oil transfer washer behind the snout and two sealing gaskets. To remove the transfer washer, thread a bolt partially in the larger hole and pull it out. ( Usually an AN-6 bolt will turn in a thread or two and let you pull the washer. Clean the surfaces well and reassemble with new gaskets. This is a prime spot for oil leaks. If you are fitting a new propeller or have had the oil snout out, you will likely have to the snout retainer in the prop hub. Remove the snap ring in the hub bore and remove the snout retaining washer. Install the propeller. Next tighten the snout until the retaining washer will lock into the hub. Reinstall the snap ring.

GESOCO INDUSTRIES INC. has all the parts if you need any, as well as static balancing services. They also offer free advice if you have any difficulties. Call them at 802-868-5633. ( I had to get a plug in here somewhere)

These propellers do not balance well on the single axes electronic balancing machines. The blades are wide enough that they need balanced on a second axis. We have found that a good vertical and horizontal static balance will remove almost all propeller vibration. If you see that pitot tube shaking out there, it is time to balance the prop.

You can repaint the blades. Be cautious stripping any old paint, as there is a fabric protective covering over the wood blade. We have found that most paint thinners will attack the resin used to glue the fabric covering. However, mineral spirits will not attack the paint or resin and is used in our shop to clean and prep the blades. Any good two part paint seems to work well. If the surface is not well prepared, the first rain storm you encounter will selectively strip your nice new paint job. It pays to weigh the blades after paint and try and add more paint to the lighter blade so that they are close to equal weight. Sometimes we have used a high build primer on the back of a blade and then sanded it down near the tip or hub as necessary to balance a set of blades. This works well and seems to last. It is much better than adding all kinds of weight at the hub to balance a light blade. What we have found it work best is to paint the prop on a balancing stand for the successful results.