B407/RR 250 C47B Bearing Failure

[EN48]

All,

Below is the essential text from an email I received from a friend heli skiing recently in BC.


The 407 that had the engine failure was three years old. (I have flown in it many times.) Its engine had about 600 hours on it. According to a pilot who was involved in the investigation of the incident, RR knows of 5 other similar bearing failures, for a total of 6 failures. The failure in BC that resulted in a very hard landing in Dec 2010 is the most serious. The other machines were able to land safely.

He said that RR has concluded that 407s <flown in BC heli skiing> and the military experience unusual stress due to many short lifts and many relatively high-g turns in flight, and that is what contributed to the failure of the bearing. He also said that to the best of his knowledge, RR has not put out any notices.


The writer is a skier, not a helicopter pilot, so perhaps some unintentional inaccuracies with the account.

I have not been able to locate info on the web re this accident/incident or the others referenced. Bearing in question said to be " main compressor bearing." Anyone have reliable info on what happend and what RR is doing about it? (I operate a B407 so this is of more than passing interest.)

[Fun Police]

just out of curiosity, where is the skier getting his/her information?

[Chris P Bacon]

This is news to me and I have spent the last 21 years working on the M250 engine, at a RR authorised facility.
I cannot recall many premature C47B engine removals due to the failure of the compressor # 1 or # 2 bearings, and none which caused an accident.

[EN48]

just out of curiosity, where is the skier getting his/her information?


From the email from skier:


According to a pilot who was involved in the investigation of the incident ...

[Fun Police]

EN48, like you i am perplexed by this as i fly the 407;
so is RR suggesting that the ski pilots are doing is something outside of the parameters outlined in the flight manual?
i might be corrected but i believe they also use arriel equiped astars in heli-skiing without this type of issue.
this seems suspect as i have a hard time believing that a pilot can cause his own engine to fail by performing a certain type of manouver. perhaps there is another problem?
hope this gets figured out soon,
fp

[EN48]

so is RR suggesting that the ski pilots are doing is something outside of the parameters outlined in the flight manual?



Dont know this for sure. I am pursuing several sources of clarification including RR. Will post any new info I can find.

[widgeon]

Surely this would have to be reported on Cadors ( site is not working right now )

[EN48]

Here is the Cadors info:

Record #1Cadors Number:2010P1907 Reporting Region:Pacific
Occurrence InformationOccurrence Type:Accident Occurrence Date:2010-12-15 Occurrence Time:1900 Z Day Or Night:day-time Fatalities:0 Injuries:2 Canadian Aerodrome ID:Aerodrome Name:Occurrence Location:8NM South East of Blue River (CYCP) Province:British Columbia Country:CANADA World Area:North America Reported By:TSB AOR Number:TSB Class Of Investigation:3 TSB Occurrence No:A10P0388
Aircraft InformationFlight #:Aircraft Category:Helicopter Country of Registration:CANADA Make:BELL TEXTRON - CAN Model:407 Year Built:2008 Amateur Built:No Engine Make:ALLISON Engine Model:250-C47B Engine Type:Turbo shaft Gear Type:Land Phase of Flight:Approach Damage:Unknown Owner:VIH HELICOPTERS LTD Operator:VIH HELICOPTERS LTD. (1255) Operator Type:Commercial
Event InformationHard landingLoss of power
Detail InformationUser Name:Matthews, Meghan Date:2010-12-17 Further Action Required:No O.P.I.:Maintenance & Manufacturing Narrative:A10P0388: VIH Helicopters Bell 407 (C-GNVI), VFR Blue River to Blue River. The Bell 407 helicopter, operated by Vancouver Island Helicopters for Mike Wigley Heliskiing, was on short final to drop off heliskiers 8 nm SE of Blue River, BC when the engine lost power. The helicopter landed hard and the main rotor blades struck the vertical fins on the horizontal stabilizer. The pilot and ski guide (seated in the front left) sustained back injuries but the five passengers were uninjured. User Name:Matthews, Meghan Date:2010-12-20 Further Action Required:No O.P.I.:Maintenance & Manufacturing Narrative:UPDATE from Maintenance & Manufacturing: The aircraft is being slung off the mountain and will be transported to a third party where it will be evaluated by the company and TSB. More details will follow after evaluation. User Name:Matthews, Meghan Date:2010-12-23 Further Action Required:Yes O.P.I.:System Safety Narrative:UPDATE: TSB had changed the class of invistigation to a 3. A MinObs has been assigned. Please note that for the most part, CADORS reports contain preliminary, unconfirmed data which can be subject to change.

[snotcicles]

Everything that has been said in this thread is pretty much what TSB said when they informally phoned us to tell us about the failure. We operate 407's so they gave us a courtesy call. It sounded like TSB and RR just had some theories as what could cause it to fail. They were speculating that with a #2 bearing that was built at the maximum acceptable "play" limit, that it could bind because of the significant centrifugal force from the compressor in hard turns. I also found it difficult to imagine that the pilot could induce his own engine failure with some aggresive flying but thats pretty much what they were guessing. RR had a new bearing in development prior to this failure and it should be available within a couple of weeks...so it sounds like they knew there was a potential problem. 407's have been skiing pretty much since they were first introduced and if this is the first failure, I would say its pretty rare. I'll bet the next time your C47 compressor is in the shop that you get a new bearing though:O

[EN48]

Had an opportunity to discuss this matter with Bell and RR reps at HeliExpo this week. Neither was particularly forthcoming, but what I think I heard from both is that there is an SB (possibly AD) in the works at RR which will require the replacement of the bearing in question with one of a new design at the next time access is available to the bearing in the course of other maintenence.

[HH60Pilot]

I had the number two engine bearing fail on a B407 (N912GX) that I was flying back in November 2009. The bird was two years old and had just less than 800TTSN. The pilot on the previous shift had an engine chip light come on at an outlying hospital. He checked the chip detectors and removed the small debris that was present and did the required ground run. There was no further debris found on the chip detectors and IAW applicable manuals the aircraft was cleared to fly. When he returned to base, the mechanic again pulled the chip plugs and found no problem.

I was dispatched to pick up a patient at an outlying hospital to bring to a trauma center in Denver. The flight out to Yuma, CO was uneventful...the return flight was another story. About 30 minutes after takeoff, the medic reported that he was hearing an unusual sound. We were flying at 1,200AGL and I immediately began a descent while I quizzed him about the noise as I could not yet hear it myself. Shortly thereafter, I began to hear the sound he was talking about and I did not like what I heard. At 700AGL the 'Engine Chip' light illuminated and I made a turn into the wind to set up for landing. At about 10' off the ground, the engine seized with a loud bang and a bright flash (especially with NVG's on). It seemed like half the lights on the MCP came on and it got quite loud with the FADEC 'bing-bong' and low rotor horn blaring. I remember saying to myself, "Hovering auto" and did what I could to save enough rotor to cushion the landing. We touched down just a bit firm, but didn't put a scratch on the bird. I did an emergency shutdown and left the battery on for light for the medcrew and patient. I quickly jumped out to check for a fire, and while there was no fire, the exhaust stack was glowing red hot and remained that way for a couple of minutes!

It was determined that the number two bearing had failed and disintegrated, which allowed the drive shaft to drop down and the noise that we were hearing was the impeller inside the compressor rubbing on the case. It appears what finally caused the engine to give up the ghost was the heat generated by the metal on metal friction got to the point where things just seized up.

I have heard, but have not been able to confirm that RR has redesigned the bearing after this happened. If anyone can confirm that for me, I'd greatly appreciate it.

Doug

[EN48]

I have heard, but have not been able to confirm that RR has redesigned the bearing after this happened. If anyone can confirm that for me, I'd greatly appreciate it.





Have just received RR Commercial Engine Bulletin: Engine, Compressor Assembly - Replacement of No. 2 Bearing, dated April 11, 2011. From the CEB:

Effectivity: All RR C30R/1, C30R/3, C30R/3M, C40B, C47B, C47M

Reason: To provide an improved No. 2 Bearing with increased moment load capability due to a limited number of occurrences that resulted in damage due to maneuvers.

Compliane Code 3: To be complied with the next time the engine , module, or component is sent to an authorized repair/overhaul facility for any reason.

[Shawn Coyle]

Doug:
Nice work! Good headwork on putting all the symptoms together.
I assume a report was sent on this??

[Chris P Bacon]

The CEB is published and distributed to replace the bearing, but there is a very limited number of bearings available. Check you can get one before pulling the engine.

[HH60Pilot]

Doug:
Nice work! Good headwork on putting all the symptoms together.
I assume a report was sent on this??

I think that every report that could have been done was done, including a statement from Med-Trans. I know that I spend a good part of the following day writing both an internal report and a report for the FAA (not how I wanted to be spending my birthday).
Copy of the statement from Med-Trans:
Date: 11/9/09 17:50

Program: North Colorado Med Evac 2

Type: Bell 407
Tail #: N912GX
Operator/Vendor: Med-Trans Corp

Weather: Clear. Not a factor

Team: No injuries reported. Patient on board.

Description:
North Colorado Med Evac 2 was on a patient transport from Yuma, CO, en
route to Denver, CO. At approximately 1750 hours, the aircraft was
westbound at approximately 1200 feet AGL when the medical crew heard
an unusual whining noise emanating from the engine area and
immediately notified the pilot. The pilot, in consultation with the
medical crew, made a decision to make a Precautionary Landing (PL) and
initiated a descent. After initial reduction of the collective, the
engine chip light illuminated and the crew selected an appropriate PL
site in a field adjacent to a road.

The pilot executed a descending 90 degree turn into the wind and set
up for a final approach into the selected landing area. During the
descent, the pilot instructed the medical crewmembers to activate the
ISAT emergency switch on the satellite phone and to contact Dispatch
and advise them of the situation.

While on short final, at approximately 10 feet above the intended
landing point, the crew saw a flash and the engine failed. The engine
failure was accompanied by a yaw and the associated aircraft
warning/segment lights and audio alarms. The pilot executed an
autorotation to the intended landing point with no damage to the
aircraft or injury to the patient or medical crewmembers.

The patient was transported by another helicopter service and the
pilot and medical crewmembers were transported by aircraft back to
their home base. The FAA and NTSB were notified. The Denver Accident
Investigation Supervisor conducted an on-site investigation and
released the undamaged aircraft. The aircraft was subsequently
recovered to an MTC facility and is being evaluated in conjunction
with the OEM regarding the cause of the engine failure.

The immediate and decisive action on the part of the pilot and medical
crewmembers, the application of sound CRM practices/principles, and
application of hands-on emergency procedures training played an
integral role in the safe outcome of this occurrence.


Additional Info:
Additional information will be provided pending the results of an
internal investigation.

Source: Larry Bugg, VP Flight Operations & Safety  Med-Trans Corp.

Due to the fact that there was no damage to the aircraft (other than an engine that seized inflight), the NTSB opted not to even bother listing it the database on their website. Which kind of makes me scratch my head as we had a patient onboard and were operating Part 135.

Doug

[HH60Pilot]

Have just received RR Commercial Engine Bulletin: Engine, Compressor Assembly - Replacement of No. 2 Bearing, dated April 11, 2011. From the CEB:

Effectivity: All RR C30R/1, C30R/3, C30R/3M, C40B, C47B, C47M

Reason: To provide an improved No. 2 Bearing with increased moment load capability due to a limited number of occurrences that resulted in damage due to maneuvers.

Compliane Code 3: To be complied with the next time the engine , module, or component is sent to an authorized repair/overhaul facility for any reason.


Thank you for the information. I must say that I'm not sure what maneuvering we would be doing in HEMS that could lead to a bearing failure. Maybe it's all that landing on rooftop helipads at trauma centers, or those slow, controlled approaches to landing on roads between the powerlines at 3AM to pick up a drunk driver that crashed on the way home from the bar that could be considered exteme maneuvers?!?

I think that RR is trying to blow some smoke up someone's skirt with that explanation!

Doug

[EN48]

I think that RR is trying to blow some smoke up someone's skirt with that explanation!



It seems to have that ring to it! I am especially concerned that some of these events happened on helicopters only 2-3 years old with well under 1000 hours TT. That RR is not recommending bearing replacement until some other maint. event causes the engine to be removed and returned to a repair facility make me nervous. This could be a thousand or more hours depending on engine time. What if the bearing fails first? :uhoh:

[HH60Pilot]

It seems to have that ring to it! I am especially concerned that some of these events happened on helicopters only 2-3 years old with well under 1000 hours TT. That RR is not recommending bearing replacement until some other maint. event causes the engine to be removed and returned to a repair facility make me nervous. This could be a thousand or more hours depending on engine time. What if the bearing fails first?

Why is RR not calling for an immediate replacement of the bearing given the fact that it has a tendency to fail? If I were the owner or operator of an aircraft with one of the engines covered by this bulletin, I would not wait to replace the faulty bearing. We were lucky the night that ours failed as the outcome would have been totally different if the engine had seized while we were on approach and in the middle of the deadman's curve!

Doug

P.S. Rolls Royce, if you are listening, do what is right and call for the immediate replacement of this bearing in all affected engines!

[Chris P Bacon]

You also get the opportunity to contribute to Rolls Royce's profits as there is no financial contribution from them for either the new bearing or the labour to replace it.
How come every time a bad part is manufactured, the engine owner get to cover all the new part cost. (cracking stage 1 nozzle shield, too thin #8 oil sump nut, snapping gas rotor tie bolts to name just a few)

[HH60Pilot]

You also get the opportunity to contribute to Rolls Royce's profits as there is no financial contribution from them for either the new bearing or the labour to replace it.
How come every time a bad part is manufactured, the engine owner get to cover all the new part cost. (cracking stage 1 nozzle shield, too thin #8 oil sump nut, snapping gas rotor tie bolts to name just a few)

It's time for this insanity to end and for RR to cover the costs. Especially considering that in the process of getting the engine certified, they state that the engine will last for a certain number of flight hours without failure. Sounds like they didn't exactly speak the truth on that!

If they are worried about the costs, think about what it will cost them if a bird full of people are killed when one of these bearings fail. Oh, but wait, they are probably thinking that this is what we have insurance for. If they pay to replace the bearings, it costs RR money. If someone dies when the bearing fails, it costs their insurance company money. That kind of thinking makes me sick. RR, if that is what you are thinking...shame on you!

[EN48]

It's time for this insanity to end and for RR to cover the costs.


Happy thought (sort of) but not likely to happen. There are more than 1000 C47B engines flying in B407's and this CEB applies to several other engine types as well. Imagine the cost to remove all these engines, send them to a repair facility, break them down, replace the bearing, reassemble, ship back, reinstall, etc. And, what if more problems are found beyond the bearing? The logistics of this would be a nightmare and would likely take several years to do every engine. A 55 gal barrel of worms at the very least!

My guess is that RR wont do this even for engines under warranty unless the bearing fails while still under warranty, and will rely on their insurance coverage as others have suggested.

[victor papa]

So we all hate Turbomeca and slant them every change we have but then at least once a possible problem was identified I can replace my Arrius 2F nozzles for free every 400hrs(except for labour which is not much) and I get credit on my Arriel 1 T2 blades for hours not used-still expensive but it looks good when the invoice have a credit note?

[bellsux]

Rolls Royce are probably more worried about paying the bills for the failure of their Trent 900 in the Qantas A380.