Making metal

LDJones

LDJones

Touchdown! Greaser!
Gone West
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Twin Cities, MN
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Jonesy
One of our helicopters was about to lift off on a training flight when they heard a loud "ka-thunk", then some vibration so they shutdown. With our mechanic they started it and had virtually no oil pressure. They shutdown again and we pulled the filter. It was full of metal. When we pulled the oil plug and screen this is what we found.

We're guessing a broken piston based on the big chunks of metal.
 

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LDJones said:
One of our helicopters was about to lift off on a training flight when they heard a loud "ka-thunk", then some vibration so they shutdown. With our mechanic they started it and had virtually no oil pressure. They shutdown again and we pulled the filter. It was full of metal. When we pulled the oil plug and screen this is what we found.

We're guessing a broken piston based on the big chunks of metal.
Click to expand...
Just flush it out and change the filter she'll be OK. :)
 
Alternate Repair method, sure to be approved by the administrator:

1. Remove affected cylinder, remove rod, piston(parts) pushrods and lifters.
2. Fit a #3 nitrile rubber segment around the affected rod journal, attach with a dab of silicone over the oil hole in journal.
3. Clamp a #3 NAPA hose clamp over the rubber and journal. Tighten hose clamp screw to 4.5 Newton Meters(or so)
4. Reattach old cylinder and pushrod outer tubes with new seals and attach the rocker cover.
5. Derate engine a skosh.

:yikes:
 
docmirror said:
Alternate Repair method, sure to be approved by the administrator:

1. Remove affected cylinder, remove rod, piston(parts) pushrods and lifters.
2. Fit a #3 nitrile rubber segment around the affected rod journal, attach with a dab of silicone over the oil hole in journal.
3. Clamp a #3 NAPA hose clamp over the rubber and journal. Tighten hose clamp screw to 4.5 Newton Meters(or so)
4. Reattach old cylinder and pushrod outer tubes with new seals and attach the rocker cover.
5. Derate engine a skosh.

:yikes:
Click to expand...

Don't forget the W&B recalculation. :)

John
 
That's a lot of metal, I'm thinking the crank and cam should be inspected also for damage.
 
One less piston, better gas mileage! A blessing in disguise. :D
 
LDJones said:
One of our helicopters was about to lift off on a training flight when they heard a loud "ka-thunk", then some vibration so they shutdown. With our mechanic they started it and had virtually no oil pressure. They shutdown again and we pulled the filter. It was full of metal. When we pulled the oil plug and screen this is what we found.

We're guessing a broken piston based on the big chunks of metal.
Click to expand...

I bet that engine was within calendar and hourly TBOs, so how on earth could that possibly happen!?!

Edits

Apparently pistons aren't a 100% replacement item at TBO on Lycomings.

http://www.lycoming.com/Portals/0/t...Overhaul and During Repair or Maintenance.pdf


Continentals are tho.

http://www.tcmlink.com/pdf2/sb97-6b.pdf
 
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bnt83 said:
I bet that engine was within calendar and hourly TBOs, so how on earth could that possibly happen!?!
Click to expand...

They get a lot of hours, so definitely within calendar and TBO, but not sure by how much on the hours. I'll check.
 
I would sent an oil sample to Blackstone to see if you really have an issue. Until the results come back, don't stray too far from the pattern.
 
PilotRPI said:
I would sent an oil sample to Blackstone to see if you really have an issue. Until the results come back, don't stray too far from the pattern.
Click to expand...

We pulled the oil pan and got at least as much metal out of it again as the first haul. The engine had 1,700 hours on it since its overhaul five years ago. It was scheduled to go down for an overhaul this winter, so we're hopeful it can be resuscitated for a few more months with a replacement cylinder. The concern is how much metal went through the system. The filter was pretty full of the fine stuff.

Mechanic is pretty sure it's a result of a number of engine overspeeds which have occurred during autorotation practice when students haven't gotten off the throttle quick enough after unloading the rotor blades. He said he's heard the overspeeds on a number of occasions, and piston skirt failures are not uncommon in that situation.

That raises the concern that if that is the cause, the other three pistons have been subjected to the same overspeed conditions. :hairraise:
 
LDJones said:
That raises the concern that if that is the cause, the other three pistons have been subjected to the same overspeed conditions. :hairraise:
Click to expand...

The good news is that either the weakest or the highest stressed piston has been identified...
 
if there is that much metal floating around the only question is what can be saved during a overhaul.
bob
 
That motor needs a COMPLETE teardown to at least clean all the metal out....

No way would I just replace a cylinder and piston....:no::no::no::no:
 
N801BH said:
That motor needs a COMPLETE teardown to at least clean all the metal out....

No way would I just replace a cylinder and piston....:no::no::no::no:
Click to expand...

Nahhhh! According to many here , 1700 hours is nothing. Just drain it, fill it with MMO and squirt some graphite in there too. It should go 2500 hours easy!
 
N801BH said:
That motor needs a COMPLETE teardown to at least clean all the metal out....

No way would I just replace a cylinder and piston....:no::no::no::no:
Click to expand...
:yeah that:

Funny about the TBO thing.
 
LDJones said:
We pulled the oil pan and got at least as much metal out of it again as the first haul. The engine had 1,700 hours on it since its overhaul five years ago. It was scheduled to go down for an overhaul this winter, so we're hopeful it can be resuscitated for a few more months with a replacement cylinder. The concern is how much metal went through the system. The filter was pretty full of the fine stuff.

Mechanic is pretty sure it's a result of a number of engine overspeeds which have occurred during autorotation practice when students haven't gotten off the throttle quick enough after unloading the rotor blades. He said he's heard the overspeeds on a number of occasions, and piston skirt failures are not uncommon in that situation.

That raises the concern that if that is the cause, the other three pistons have been subjected to the same overspeed conditions. :hairraise:
Click to expand...

I think autos are way over rated, and this is more proof. They are VERY hard on the equipment as the destruction of this engine points out. More helos are lost practicing auto rotations than are saved actually doing them. For students and private pilots the concept should be enough.

We don't crash land fixed wing aircraft to practice engine outs. :no:

We did away with manditory spin training in fixed wings when the FAA & NTSB finally figured out spins were killing more students and CFIs than the training was saving. Autos need to go away for students and PPLs.
 
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Just think, IF this metal generating failure got metal to the crank bearings, the damage is already done. If you still have good oil pressure, fly it, your not going to do it any more harm.

But don't believe you are going to ever overhaul that crank again. 0-200 crank I replaced 2 years ago, cost $4500.00 I'll bet the price has not come down any.
 
Geico266 said:
I think autos are way over rated, and this is more proof. They are VERY hard on the equipment as the destruction of this engine points out. More helos are lost practicing auto rotations than are saved actually doing them. For students and private pilots the concept should be enough.

We don't crash land fixed wing aircraft to practice engine outs. :no:

We did away with manditory spin training in fixed wings when the FAA & NTSB finally figured out spins were killing more students and CFIs than the training was saving. Autos need to go away for students and PPLs.
Click to expand...

Heck, there are a lot of fixed wing aircraft lost to training takeoff, landing, and go arounds too. It's a part of flying that has to be mastered, not avoided.

I'm not so sure about your assertion. Seems to me knowing the "concept" of an autorotation would be pretty worthless if faced with an engine failure.

Many years ago I received about 25 hours of dual turbine time before figuring out getting the ticket was going to cost way more money than I possessed and there was no real reason to have it. But I did get in a few practice autos at altitude, and my instructor hammered me on energy management and rotor RPM.

Not learning those skills makes for an undertrained pilot IMHO.

Here's an AC which has some statistics...

Helicopter Accidents. The U.S. Joint Helicopter Safety Analysis Team (U.S. JHSAT)
Compendium Report (2000, 2001, and 2006) shows that training continues to be one of the top operational categories of helicopter accidents in the United States, representing 17.9 percent of all accidents.

Of the 523 helicopter accidents reviewed, failures in autorotation training were noted in 68 accidents, or 13 percent. Furthermore, six accidents within the previous five years of issuance of this AC involved a National Transportation Safety Board (NTSB) probable cause as "180 degree autorotations."

Although this is less than 1 percent of accidents in this time period, this advanced maneuver requires attention in an effort to reduce all helicopter accidents.
Click to expand...

http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_61-140.pdf
 
3393RP said:
Heck, there are a lot of fixed wing aircraft lost to training takeoff, landing, and go arounds too. It's a part of flying that has to be mastered, not avoided.

I'm not so sure about your assertion. Seems to me knowing the "concept" of an autorotation would be pretty worthless if faced with an engine failure.

Many years ago I received about 25 hours of dual turbine time before figuring out getting the ticket was going to cost way more money than I possessed and there was no real reason to have it. But I did get in a few practice autos at altitude, and my instructor hammered me on energy management and rotor RPM.

Not learning those skills makes for an undertrained pilot IMHO.

Here's an AC which has some statistics...



http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_61-140.pdf
Click to expand...

A lot of fixed wing planes lost in training? Please post that link.

Did you own the helo you were training in?

Demonstrating autos is all that is needed, IMHO. Entry, stabilized approach, controlling air speed & rotor RPM, flair to hover. Done. No need to do hundreds of them. We don't crash land fixed wings in training for engine outs, we shouldn't crash helos either.
 
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Given the circumstances and time SMOH on that engine I would NOT sign it off for return to service without a tear-down inspection. Time to bite the bullet and overhaul NOW. It only take one bearing seizure to create a situation your lawyers have warned you about.
 
weilke said:
Very skewed statistics. If you spread the skids or cause a tailrotor strike during a auto-rotation, it wont make it to the NTSB unless someone gets hurt. You would have to include stats from the manufacturer to come up with all the training incidents where a helo got bent.
Click to expand...

Thank you. :yes:

I am certainly not advocating no auto rotation training. Demonstrate the student knows the components to autos, do one unassisted for the CFI, DONE! No different than the engine out training for fixed wing. It is not required to be demonstrated on the check ride for fixed wing.
 
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Clearly these things need another engine or a parachute
 
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