Jetranger Question...

[Jay Flight]

Is there a minimum amount of time to walk the blades for it to be effective? (once around, twice around, 30 seconds etc?)

 

Please answer this for all us who haven't started training

[cap]

Jay Flight -----by the time you get once around you'll feel and hear if you got a problem. DGP is also correct and don't confuse the two issues. If that engine is fresh or recent out of O/H, then you want to be doing things just like DGP said because that ain't normal and you want to be keeping that "mother" on terre firma to find the cause. There's no "be all and end all" to any of this and there could be a multitude of checks that some engineer needs to do. At some point, you can bet that he'll be on the phone to some Superior or the O/H shop that did the recent O/H if he can't find the cause. A short tip is in order here: Want to take a short-cut to learning about the engine in the a/c you fly?..........hang with the experienced engineers and ask questions........and there's no such thing as stupid questions either. You'll get more knowledge outta them and the M & O Manual than you ever will out of any FM concerning engines.

[Guest CHEVY II]

Once again, very interesting responses. Thanks!

 

I'm waiting for the trusty old engineer to return to provide his opinion.

 

Definitely one of the better aspects of this forum to be able to network like this in a matter of days.

[DGP]

Just remembered another one I encountered on an L...this one was locked up in the hangar...it was stone cold at the time....blades would not move at all...had Bob C come over...we loosened up the nuts holding the turbine onto the gearbox....just a small amount and presto she unlocked...a/c was bolted together again an everything was fine...for a while...about a year later that donkey blew the 6&7 oil seal right out the back end

[RTR]

Do a decel check. Even though it happens after the engine has cooled down, it does not rule out turbine rub.

 

Are you following the cool down period properly before shutting down?

 

It does sound like carbon build up to me as well, however get that decel check done. From 100% N2 roll the throttle to idle, and time how long it takes for N1 to

decel past 65%. It should take at least 3 or 4 seconds. If it is happening quicker than that (say 1 to 2 seconds), the wheel (or wheels) are rubbing, and it needs to be addressed as a snag.

 

What you describe IS NOT NORMAL.

 

Has this been happening since installation of the turbine?

 

Lots of good advice and ideas coming through here. Nice to see!

 

cheers,

RTR

[cap]

I often laugh at the staement, "but it just came outta the O/H shop". There were a whole pile of good O/H's that came outta Standard Aero over the years regarding 250's, BUT you had the odd "gaffe'.

 

I once had an engine timex and the new one was sitting right there that evening for installation. There was a big hurry-up involved and since many experienced engineers were present, everybody got involved. Everything went together "tickedee-boo" and real quick. THEN the final moment came when they tried to matchup the holes on the firewall with the holes on the compressor.........and NOT ONE lined up......so what the **** is going on here? Long story short and after much blue air in the hangar, a call is made to Standard Aero. The result? It was determined that the compressor had been installed 90 degrees off byStandard. At that time, engineers weren't allowed to split a compressor or remove any inserts holding it onto the engine in the field at least. Permission to do so was finally obtained and the job was completed. I doubt if there are many here who haven't go their own stories to tell in that regard either.

[DGP]

Had something similar...engine just had a o/h turbine installed...did a d/i and noticed the engine oil was very dark...now we were runnin 2389 oil...this stuff does not turn black like 560 does and I got a few guys lookin at it...we decide to do an oil flow on the turbine off the 6&7 sump can...like you normally would...oil flow is great...so we dump out the old oil..check the oil filters...I go flying for about 7-8 hours...get back to the hanger ....oil is friggin black as coal...everyone is scratching there heads...change oil again...later that day...the 6&7 oil seal goes by-by...as it turned out as I am changing the turbine outside at -40..the return line from the engine to the gearbox was almost completely blocked by carbine buildup...the line from the 6&7 sump back to the gearbox...now we all know the size of that line...that is a lot of carbine...when the new turbine was installed with the new seals the oil could not return to the gearbox as fast as the old one did...I suspect that the old seal was blowing oil out into the exhaust so the pressure didn't build up and blow the old seal....so if and when you are changing a turbine I would always check that return line for blockage....we all fly at lot of different a/c...at least I use to...going from one to the other is very hard to keep track of whats been done...sure they have great way of tracking things but not a blocked oil line...so when things don't add up...park it...my two cents worth

[darcor]

I have encountered this. Usually after overhaul. My opinion would be not to worry unless...

 

1. Is there smoking after shut down

 

2. is the oil jet you clean coking a large amount

 

3. is your flow check below the min 90cc

 

4. are the pilots power checks (if they do them) not consistant

 

5. is there any abnormal noise when you turn the blades

 

6. is there abnormal oil consumption

 

Hope this helps

 

Daren

Edited November 28, 2005 by darcor

[Bell Hell]

1) Convert to Mobil 254.

 

2) Do the blade backwards walk-around as soon as they stop. Wait longer and 'you're pissin' into the wind'........and ain't doing nothing. It's "coking" your after and trying to break-free and you're trying to get it before it hardens-up. Not ALL 206's will require it, but until you find out which ones don't.......do'em all. Mobil Jet II is the buggar in most cases, as Blackmac suggested and that's why the suggested conversion. It ain't a new problem and has been with us for eons.

 

Re: #1

 

Conversion to 254 can only be accomplished on a turbine fresh from overhaul, as it will loosen carbon deposit chunks in the hot end, which will follow Murphy's law and plug an oil jet. Avoid this.

 

That said, my (limited) experience with 254 has been that you'll get no accumulation of carbon at the 6-7 jet or strut/sump. Also, some older gearbox seals are not compatible with the 254 so you may get leakage from all the hard to reach areas. Make certain your overhaul has the correct seals before you switch.

[rotarywing]

If your a pilot put snag in log book and let engineer look after it. This will cover your butt.

As said above there can be many theroies which should be all ruled out.

They do quit in the air from coking or turbine rub. it is not normal.

You should have a nicad filter installed and change oil 100hrs or on a regular basis if you fly low hours. Very inportant to do oil flow every 100 hrs, turbine strut cleaning 300hrs faithfully or sooner. Get it fixed or in writing that this is ok.

 

my two cents

larry D.