250c20b Chip Plugs

[Happyguy]

Can anyone tell me why there are 2 chip plugs on the engine so close together. What oil stream is the upper one in. The bottom is pretty obvious.

[wrench spinner]

Lower one is for gearbox, upper one is situated in the oil pump stream- all external bearings (turbine/compressor)

If you look at the backside of the gearbox, you will see the supply and scavenge lines going to/from the turbine (6/7/8 brngs)and the front side of the gearbox is the #1 oil line.

[Happyguy]

Thanks for that.

We got a chip light on the upper sensor and not the bottom.

Light came on at first start after sitting for 2 days.

There was no light during the previous flight....fortunately

Engineers will look at on Monday.

Just trying to inform myself and understand what is happening there.

Thanks again.

[wrench spinner]

......and #5 bearing (oops)

[Happyguy]

#5 bearing ?????

[wrench spinner]

The #5 bearing is in the turbine - supports the front of the power turbine rotor but is actually fed and scavenged through the gearbox, so it would show up on the lower plug as well

[Happyguy]

Whhhew.........thought it was something hideous expensive and not just really expensive to repair.

So from what you are syaing the chances are it is a bearing on the way out.

Why do these bearings fail?

Normal wear and tear or abuse ?

This machine has seen little "hard" service....basically just personal transport.

Thanks again

[RedRag]

My rule for all 250's is a chip on an upper plug is far worse than the lower. The lower one will catch any thing from the engine gearbox and there are lots of possibilities.

 

Upper one, is bearings. Can be real bad real fast. If the #1 bearing makes metal, it ususally comes apart pretty quick and there goes the compressor. IF the chips or chunks are bronze coloured on tne upper plug, look at #1 bearing.

 

Good thing about the upper one is that you can figure out where the metal is coming from pretty easily disconnecting the return lines and cranking the starter.

 

We only run one plug on the bottom, the ones that plugs in from the side, the bottom one that faces ths deck is a pain in the *** to get in and out.... both are in the same oil galley

 

Red

[Happyguy]

Thanks for that.

We are going to pull it (the plugs) this afternoon.

I'll let you know what we find.

If it is a bearing how long does it take to get it fixed and back.

Just curious......had a big trip booked for the end of the month.........

[skidkicker]

1/2 a day to get the engine out, 1-2 days shipping, 1 week in the overhaul shop depending on how busy they are. 1-2 days shipping, and a day to put it in. You could get a loaner engine but I think you should get the engine back in time for your trip. Personally, if it is just a small sliver or flake, keep flying the helicopter. I use the 3 chips your out rule for the C20b. Just record it in the log book.