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Bell 407


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In the last year i can think of 3 407's that where grounded for and extended period of time waiting for a new engine after a chip light. Is there a problem? Or is it that the aircraft land safely and the incident is only reported to accounting and quietly dealt with in house.....

 

 

2011-08-09 Further Action Required:No O.P.I.:System Safety Narrative:UPDATE TSB reported that the Northern Air Support Bell 407 helicopter C-FNAK was moving personnel in support of mining operations in the area of the Hackett River Camp, Nunavut. Approximately 20 miles south of Hackett River while at low level an engine chip light came on. The pilot landed the helicopter and was following the normal engine cool down procedure when a loud bang was heard followed by debris being flung forward of the helicopter. The pilot immediately activated the fuel shutoff and turned off the battery master. The pilot and four passengers exited the helicopter and fire was observed in the engine area. The pilot returned to the helicopter and attempted to put out the fire with the handheld cockpit fire extinguisher. The fire continued to burn and pilot turned on the ELT and grabbed their handheld radio. The helicopter was completely consumed by a post-crash fire. The pilot contacted the camp and was picked up a short time later. A cursory examination of the wreckage indicated an uncontained failure of the Allison 250 C47B engine. The engine was removed from the site and is being shipped to the TSB Engineering Branch in Ottawa for further examination.

 

 

 

 

 

 

 

 

 

 

 

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If and that's a big if, I recall correctly there have been some issues with the number 2 bearing failing

 

 

It's enough of a problem that there is an updated #2 bearing. I do not know if there is any intention to make the upgrade mandatory, or if they've ceased distribution of the old style bearing.

 

 

Nothing is unbreakable.

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As mentioned the 407 engine has 3 problem areas:1- the torquemeter gear,2-the #2 bearing,3- the #4 bearing...all of these have been addressed with new parts...it should be mentined that the chip detectors on the 407 engine will collect a larger amount of metal before the light will come on in the cockpit..if you are seeing any kind of metal at all on the chip plugs you had better keep an eye on it...we had metal on the lower plug everytime that the chip plug was suppose to be checked..which I did not like ... I was told to keep an eye on it...so I started to pull the chip plug after every flight...this went on for at least 6 months...sometimes there was nothing for a lot of hours...sometimes it had a little every time I looked at it....never had the light come on...finally I was 5 minutes from the hangar and the chip light came on..it was springtime..the lakes around here were unsafe to land on and lots of trees and no roads to park on so I took it up another 1000 feet and flew to the hangar which took a few minutes...landed at the hangar...rolled power back...2 min cool down...shut down...pulled the lower chip plug...had a 1 inch tail of metal on the plug...when I pulled the engine apart with the help of a friend from standard aero..the #4 bearing had broken right in 2 pieces...would not have run for much longer....we replaced the #4 bearing with the new and inproved one...ran it for about a year and 6 months before it started making metal again...and as it did before...no chip lights,just small amounts of metal ...went through this for a couple of months and we sent the engine to standard areo in wpg who pulled it all apart...they could see nothing wrong...we had them pull the #4 bearing apart which meant destroying it to get it apart...the ball bearings in it looked like marbles that had been through a rock crusher...so if you keep an eye on your chip plugs,any kind of metal means trouble is a brewing in there... :unsure: :shock:

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Thanks for that DGP! A good informed, hands-on post with genuine experience. That info is now locked in my vault for any future 407 driving! Cheers!

 

 

 

As mentioned the 407 engine has 3 problem areas:1- the torquemeter gear,2-the #2 bearing,3- the #4 bearing...all of these have been addressed with new parts...it should be mentined that the chip detectors on the 407 engine will collect a larger amount of metal before the light will come on in the cockpit..if you are seeing any kind of metal at all on the chip plugs you had better keep an eye on it...we had metal on the lower plug everytime that the chip plug was suppose to be checked..which I did not like ... I was told to keep an eye on it...so I started to pull the chip plug after every flight...this went on for at least 6 months...sometimes there was nothing for a lot of hours...sometimes it had a little every time I looked at it....never had the light come on...finally I was 5 minutes from the hangar and the chip light came on..it was springtime..the lakes around here were unsafe to land on and lots of trees and no roads to park on so I took it up another 1000 feet and flew to the hangar which took a few minutes...landed at the hangar...rolled power back...2 min cool down...shut down...pulled the lower chip plug...had a 1 inch tail of metal on the plug...when I pulled the engine apart with the help of a friend from standard aero..the #4 bearing had broken right in 2 pieces...would not have run for much longer....we replaced the #4 bearing with the new and inproved one...ran it for about a year and 6 months before it started making metal again...and as it did before...no chip lights,just small amounts of metal ...went through this for a couple of months and we sent the engine to standard areo in wpg who pulled it all apart...they could see nothing wrong...we had them pull the #4 bearing apart which meant destroying it to get it apart...the ball bearings in it looked like marbles that had been through a rock crusher...so if you keep an eye on your chip plugs,any kind of metal means trouble is a brewing in there... :unsure: :shock:

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Guest 47yrLowTimer

Any thoughts on why the bearings are packing it in?

 

Lack of lubrication to keep them cool?

 

DGP as already mentioned thank for the heads up. It's this kind of info that its invaluable and could truly be a life saver

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Any thoughts on why the bearings are packing it in?

 

Lack of lubrication to keep them cool?

 

DGP as already mentioned thank for the heads up. It's this kind of info that its invaluable and could truly be a life saver

 

 

#2 bearing failure was basically poor design. It could not handle the load imposed by the gyroscopic rigidity of the large® compressor. However, it could only fail catastrophically (or so they say) providing it happened to be one of a very small percentile of bearings (manufactured with the tolerances on both ends of the scale respective to both races or the balls) and if the aircraft was frequently being 'aggressively' maneuvered. Their definition of such maneuvers fell basically within the scope of normal flying in a utility environment; so with enough utility machines it was bound to eventually produce an abrupt failure. However, generally the failure is slow and will produce flakes for a while before it goes.

 

In short, pull your chip detectors/plugs frequently, even if it is not required. ALF/Daily is a good practice of any aircraft with quick disconnect chip detectors.

 

I believe the #4 bearings were on death row also because of poor design. I don't have any knowledge of what exactly Rolls Royce has to say regarding the subject.

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