250c20b Chip Plugs

[Happyguy]

OK...couple of small silver slivers. Cleared them then ground engine for 155 minute with no light. Flight tested for 10 minutes with no light.

So we are going to put it back in the air and watch it.

If we get 3 more chip events the engine comes out.

Looks like one of the balls are spalling.

To Be Continued........

[nutmix]

OK...couple of small silver slivers. Cleared them then ground engine for 155 minute with no light. Flight tested for 10 minutes with no light.

So we are going to put it back in the air and watch it.

If we get 3 more chip events the engine comes out.

Looks like one of the balls are spalling.

To Be Continued........

 

From memory the book says no more lights within 8 hrs, and no more than 4 lights in 50 hrs. Shiney flakes on the top plug are usually #1, 6 or 7 bearing.

 

 

Hope all goes well with no more lights, plan your trip along vehicle access for the first few hours incase you get another light. Nothing worse than being stranded in the middle of nowhere.......

[bushman]

OK...couple of small silver slivers. Cleared them then ground engine for 155 minute with no light. Flight tested for 10 minutes with no light.

So we are going to put it back in the air and watch it.

If we get 3 more chip events the engine comes out.

Looks like one of the balls are spalling.

To Be Continued........

 

 

Happy, if you are sure it is actually silver that you found, it is most likely coming from the carrier on one of the bearings, # 8 being the hottest and under most stress. the balls spalling would not be a sliver but some kind of small chunk as they are stainless steel and it is not likely to form a sliver. Balls spalling anywhere would mean a very short life remaining on any of those bearing as the rpm on the turbine group is somewhere around 33,000 rpm, more for the compressor of course. I am assuming you did a mag test on the sliver, therefore your take that it is silver. Slivers per se could come from other areas around the bearings, I am not that versed on the 250 but say on an Ariel, we troubleshot one back to the large nut that hold the torque meter gear in the gear box. As it got torqued and met with the face of the gear, it tore a small thin but fairly long sliver out of the face of the nut and that of course fell to the bottom of the gear box at some point during operation, erdo, instant cheap light... Now where did it come from, not so obvious at first... This might have been prevented by running a wet oiled finger on the mating surfaces of the to-be-torqued assembly before assembly. Maybe it was done, it is hard to say after the engine has been put back together, sent to the operator and then flown for 25 to 50 hours or so. Then again it might just be the luck of the draw.

 

If you happen to speak to a 250 builder from an O/H shop, ask them if any silber seals are used in the oil pipes of the oil system. That could be the source also. I am not familiar enough with the 250 , again just from memory, i think there is one on the bottom of the small oil scavenge pan that drains your #7 and #6 brgs. Doubt it could somehow put any silver in the oil flow, but you never know, typically these things would be a result of some kind of installation foul up. Anyway hopes that help a bit.

 

 

[z1milhouse]

Hmmm. The Allison manual is very clear on the procedures for chip lights. Now I don't have one in front of me but from memory it’s something like this.

 

1. First Light pull BOTH plugs and the gearbox filter check for chips clean filter.

Run aircraft on ground for 20-30min if no chip lights

PULL THE PLUGS AGAIN and check for chips no chip your good to go

IF you have chips Drain oil change, external filter, clean gearbox filter run again

IF you have chips do above and flush oil system run again

IF you have chips get a crate and ship the Engine or Component out for repair.

 

IF you are operating a commercial helicopter you require elementary training to pull even a quick disconnect plug which are rare now on 250s. If they are screw in type your company has to get approval for pilots to do it and you still require training.

 

At the risk of being rude all the tips here are great but it’s pretty clear you are not qualified to remove or assess the chips on the plug. These machines have crashed due to total inexperience and incompetence checking chips detectors at the very least get a copy of the maintenance instructions and an engineer to walk you through it.