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Prop inspection

 
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tigeryak18t



Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

PostPosted: Wed Oct 07, 2009 2:12 pm    Post subject: Prop inspection Reply with quote

Hello to all,

sorry if this subject has already been discussed but I couldn't find anything about it. A friend of mine has a leak on his prop (yak52) . It appears as a thin oil leak on the propeller after half an hour of flight. I would like to inspect his prop hub, joins etc..
Do anyone knows where I can find a schematic of the prop, or a task card or anything that can help to find where does this oil going on the fins comes from.

Thanks a lot


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Didier Tiger YAK18T
Member of Commemorative Air Force
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viperdoc(at)mindspring.co
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PostPosted: Wed Oct 07, 2009 5:02 pm    Post subject: Prop inspection Reply with quote

Didier,
See attached.
Doc

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dsavarese0812(at)bellsout
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PostPosted: Wed Oct 07, 2009 5:21 pm    Post subject: Prop inspection Reply with quote

Didier,
The prop hub is quite simple to inspect. If you have a spinner, remove the spinner to expose the prop hub dome. If you do not have a spinner, remove the 30 mm nut and cotter pin. Then remove the small dome cap. Look inside the dome cap to see if the felt is oil soaked. Next, look for the lock tab with a screw through it on the edge of the hub directly above or below the center of the dome. Cut the safety wire, remove the screw and slide the locking tab out of the hub.

Now, rotate the hub dome to align the slots with the tabs and slide the dome out SLOWLY. There is oil inside this dome. So be sure to tilt the front of the dome downward as you pull it out of the hub. The oil tube will be dripping oil at this time. Make a plug from a paper towel and plug the end of the oil tube.

Next, while holding the dome in your hand, pull the piston out of the dome. Remember, there is oil inside the dome. So don't tip the dome over while pulling the piston out of the dome.

There are 2 seals in the prop hub piston. The outer seal, is large and if damaged will cause oil to leak out around the prop hub dome. Remember I said to look at the felt inside the dome cap? If there is oil on this felt, the outer seal of the piston is leaking. Oil will be evident on the outside of the hub and on the cooling louvers and disk.

There is also an inner seal in the hub piston. It is twice the size of the hole in the center of the piston and somewhat "fun" to replace. If this seal is bad, there will be oil inside the hub. Look inside the hub for oil. If oil is pooling inside the hub, the inner seal on the hub piston is leaking. The inner seal rides on the oil tube which you previously plugged with a paper towel or something similar.

Check the inside of the dome for scoring. If the scoring is bad, it will damage a new seal when you reassemble the piston and dome.

Purchase a prop hub seal kit and prepare to replace the two seals on the piston. Clean the dome and piston thoroughly before reassembling. Be absolutely certain you observe which way the seals are installed. Now remove and replace the seals. Carefully install the piston back into the dome. Do not damage the outer seal. If you put either seal in backwards, when you start the engine you will give your airplane an oil bath.

If there is oil inside the hub, soak the oil up with shop towels or something similar. You will need to remove the prop blades because oil has been diluting the grease around the hub bearings. You will need a large hook spanner wrench to do this. First remove the two lock tabs on either end of the hub. They have 2 slotted screws in them and the screws are safety wired together. Mark the slot in the castellated nut where the tab in the fits into the nut with a Sharpie pen. You will use this mark when you tighten the nut back up. Next, as you face the hub, using the hook spanner wrench, place the wrench in the large castellated nut just inside the counterweight and loose the nut. You may need to use a hammer at first to loosen the nut.

Unscrew the nut and the entire blade assembly will drop out. BE CAREFUL and don't drop the inner bearing which will be on the end of the blade hub. There is square slider (about 25 mm) on the inside of the hub fitted into a slot. It has a hole in it where the pin on the end of the blade fits in to. Remove this. CAREFULLY OBSERVE HOW THE INNER BEARING AND RACE ARE FITTED INTO THE HUB. The bearing has a flared inner edge. This edge goes toward the end of the blade. There is also another bearing that will remain on the blade just inside the threads of the large castellated nut. Clean all the parts, grease them with Aeroshell #5 or similar grease, place the loose race back in the hub then place the loose bearing in the hub flush up against the race. Now place the square slider in the slot and position the sliding mechanism at the bottom center of the hole.

Now reinstall the prop blade being care to align the pin on the end of the blade with the slider at the bottom center of the hub hole. Now thread the castellated nut back into the hub. DO NO TIGHTEN at this time. Now rotate the prop 180 degrees so the recently reinstalled blade is on the left. Now using the hook spanner wrench, tighten the castellated nut so the locking tab will line up when the nut is tight.

Repeat the above procedure for the other blade.

Now reinstall the hub dome and piston back into the front of the hub. Reinstall the hub dome locking tab and screw. Safety wire the screw to the hole in the locking tab.

Reinstall the dome cap or the spinner.

Dennis
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Rich Langer



Joined: 10 Apr 2007
Posts: 26
Location: Florida

PostPosted: Mon Oct 12, 2009 6:19 am    Post subject: Re: Prop inspection Reply with quote

Dennis:

Is the CJ's Housai prop inspection the same as the Yak-52?


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dsavarese0812(at)bellsout
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PostPosted: Mon Oct 12, 2009 6:27 am    Post subject: Prop inspection Reply with quote

Pretty much the same thing. FWIW, the seals in the CJ hub are identical to the seals in the Yak 52/Yak 18T prop hub (V530).
Dennis
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