Chip warnings
Iconoclast
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To: Sling load and coalface
It was my error in confusing the BV 107 with the BV 234. You can chalk the mistake up to my advanced age. After all I was only off by 127 which in dog years is only 18.143. What surprised me was that no one challenged my comment about a design defect in the transmission which precipitated the lock up.
It was my error in confusing the BV 107 with the BV 234. You can chalk the mistake up to my advanced age. After all I was only off by 127 which in dog years is only 18.143. What surprised me was that no one challenged my comment about a design defect in the transmission which precipitated the lock up.
Iconoclast
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To: Capn Notarious
Most engines and most helicopter transmissions and intermediate and tail rotor gearboxes are equipped with chip detectors. Some of these detectors are simple devices that magnetically attract a chip and if the chip bridges a gap a circuit will be made and a light will illuminate. Other more complex chip detectors work in the same way but an additional electrical circuit will allow the chip to be burned off. If the chip is too big to be burned off then there are impending problems in the gearbox. Even if the chip is of non-magnetic material it will if it bridges the gap cause the light to go on. Most chip detectors can be removed from the gearboxes with out losing any oil due to a spring-loaded valve built into the chip detector body.
There are some jet engines that do not employ chip lights. (Mainly Rolls Royce). The engine is protected with chip collectors who are nothing more than magnets. These detectors are removed on a periodic basis and the chips are collected on clear adhesive tape and this tape is transferred to an inspection card. This card is then sent to Rolls Royce or an assigned lab and the chips are analyzed. Records are kept and when any of the chips build up at a specified rate the engine is pulled and sent for sectional overhaul. On this type of chip collector it is imperative that the “O” rings be replaced prior to reinstallation. An Eastern Airlines L-1011 was almost lost due to oil starvation when the oil leaked out past the un “O” ringed chip collectors.
I do not believe the Apache intermediate or tail rotor gearboxes are protected by chip detectors because they are lubricated by very viscous grease, which would limit the migration of chips. (At least that is the way they were designed).
One other point is that chip detectors do not protect the unwhetted parts of an engine such as turbines and compressors. That is why they specify periodic bore scope inspections.
Chip detectors or chip collectors indicate that there is a problem in the system being monitored (not including spurious chip lights due to initial break-in of the transmission or engine). That is why during the first (X) hours the oil filters must be changed. A Spectrometric Analysis of the oil on a periodic basis will indicate premature wear long before the chips develop.
Most engines and most helicopter transmissions and intermediate and tail rotor gearboxes are equipped with chip detectors. Some of these detectors are simple devices that magnetically attract a chip and if the chip bridges a gap a circuit will be made and a light will illuminate. Other more complex chip detectors work in the same way but an additional electrical circuit will allow the chip to be burned off. If the chip is too big to be burned off then there are impending problems in the gearbox. Even if the chip is of non-magnetic material it will if it bridges the gap cause the light to go on. Most chip detectors can be removed from the gearboxes with out losing any oil due to a spring-loaded valve built into the chip detector body.
There are some jet engines that do not employ chip lights. (Mainly Rolls Royce). The engine is protected with chip collectors who are nothing more than magnets. These detectors are removed on a periodic basis and the chips are collected on clear adhesive tape and this tape is transferred to an inspection card. This card is then sent to Rolls Royce or an assigned lab and the chips are analyzed. Records are kept and when any of the chips build up at a specified rate the engine is pulled and sent for sectional overhaul. On this type of chip collector it is imperative that the “O” rings be replaced prior to reinstallation. An Eastern Airlines L-1011 was almost lost due to oil starvation when the oil leaked out past the un “O” ringed chip collectors.
I do not believe the Apache intermediate or tail rotor gearboxes are protected by chip detectors because they are lubricated by very viscous grease, which would limit the migration of chips. (At least that is the way they were designed).
One other point is that chip detectors do not protect the unwhetted parts of an engine such as turbines and compressors. That is why they specify periodic bore scope inspections.
Chip detectors or chip collectors indicate that there is a problem in the system being monitored (not including spurious chip lights due to initial break-in of the transmission or engine). That is why during the first (X) hours the oil filters must be changed. A Spectrometric Analysis of the oil on a periodic basis will indicate premature wear long before the chips develop.
In the air you cannot tell how serious the problem is, the ground is the place to be, if it can be achieved in safety.
Just to cheer everyone up, a number of moons ago,
I was invited to examine the internals of a Hughes 500 main gearbox that I had been flying.
Sitting on the main ring gear was a pile of swarf
which was the remains of the main input bearing.
The bearing had virtually no chrome on it and appeared to have been chewed by rats. Failure time dead soon.
No chip warnings had occurred. The engineer had noticed the metal in suspension in the oil sight glass. His comment was that if we had been using one of the darker Mobil oils and and not Shell 500 it would not have been seen.
Sometimes you just get lucky.
Just to cheer everyone up, a number of moons ago,
I was invited to examine the internals of a Hughes 500 main gearbox that I had been flying.
Sitting on the main ring gear was a pile of swarf
which was the remains of the main input bearing.
The bearing had virtually no chrome on it and appeared to have been chewed by rats. Failure time dead soon.
No chip warnings had occurred. The engineer had noticed the metal in suspension in the oil sight glass. His comment was that if we had been using one of the darker Mobil oils and and not Shell 500 it would not have been seen.
Sometimes you just get lucky.
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I am not sure that I can agree with coalface, when he says that chip lights do not give a useful warning. I can think of 2 events where chip lights on Allison engines in JetRangers caused me to land. In both cases, the subsequent engineering investigation grounded the aircraft until the engine was taken out. There was no guarantee that a catastrophic failure would have resulted, but the problems were certainly significant and could have caused an engine failure, and the engineers would not certify the A/C for further flight. In one case we were ferrying a JetRanger from Portugal to the UK, having just picked it up after a purchase. The light came on in Northern Spain, so as per AFM land ASAP. Steel nuggets all over the chip detector and aircraft completed the trip by road.
Another reason to obey the light:
A UH-1H landed near the staging field at Ft Rucker AL 3 miles short of the field with a transmission chip, and no secondaries. Who would have been tempted to continue to the field?
When he rolled the throttle off from the idle position after landing, there was a huge grinding noise and, in his estimation, the blades turned only turned a further 5 times or so before grinding to a halt and twisting the aircraft!! Transmission had siezed.
Flight manual does require land as soon as possible. As I said above, each system is different, and I would follow the flight manual unless there was a safer course of action.
A UH-1H landed near the staging field at Ft Rucker AL 3 miles short of the field with a transmission chip, and no secondaries. Who would have been tempted to continue to the field?
When he rolled the throttle off from the idle position after landing, there was a huge grinding noise and, in his estimation, the blades turned only turned a further 5 times or so before grinding to a halt and twisting the aircraft!! Transmission had siezed.
Flight manual does require land as soon as possible. As I said above, each system is different, and I would follow the flight manual unless there was a safer course of action.
So!
Is it - pan pan pan.....
or
pan pan pan pan pan pan
hmmm?
Additionally,
I consider the pressure guages to be a major indicator of the aircrafts condition. The last time I had a MGB go pear shaped, my only indication was decreasing oil pressure and a rise in temp. Once opened, we found pieces of broken gears and baffles. It was my lucky day because the oil feed system was common to the engine and the gearbox. Thus, I was thinking that I had an engine oil pump failure or an engine related problem rather than an impending catastrophic failure of the MGB.
Is it - pan pan pan.....
or
pan pan pan pan pan pan
hmmm?
Additionally,
I consider the pressure guages to be a major indicator of the aircrafts condition. The last time I had a MGB go pear shaped, my only indication was decreasing oil pressure and a rise in temp. Once opened, we found pieces of broken gears and baffles. It was my lucky day because the oil feed system was common to the engine and the gearbox. Thus, I was thinking that I had an engine oil pump failure or an engine related problem rather than an impending catastrophic failure of the MGB.
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I was told in my PPL training and in my previous hobby of yachting that it is Pan pan, pan pan, pan pan. One does feel somewhat self conscious coming out with this but I suppose the recipient either thinks "this guys in deep or a prat". Anyone know where it comes from?
Iconoclast
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One of the biggest precipitators of helicopter gearbox failures is the use of the same oil that is used to lubricate the gearboxes and bearings of gas turbine engines. The US Army wanted to standardize on the lubrication oils used in transmissions and engines and decided that it would cut down on operational and supply costs to go with a single oil and that oil was that used in the engines.
The problem was that the film strength relative to high point contact loading of gear meshes was at the ragged end of the spectrum when used in helicopter transmissions. These gearboxes were originally designed to operate using mineral-based oils as the lubricant and when the oil specs were changed they started to have problems. Later design transmissions were designed to use engine oils (synthetic) as the primary lubricant with a winter and summer grade the same as used in the engines. Even though the gearboxes were designed to use the synthetic oil, the problem of high point contact loading was not solved. And, under certain conditions the film strength will deteriorate and the gears and bearings will run metal-to-metal and that is when the wear and deterioration and subsequent failure will occur.
Once again I reiterate Spectrometric Oil Analysis will detect the impending breakdown of the oil as well as to detect the incipient wear of the lubricated parts.
The problem was that the film strength relative to high point contact loading of gear meshes was at the ragged end of the spectrum when used in helicopter transmissions. These gearboxes were originally designed to operate using mineral-based oils as the lubricant and when the oil specs were changed they started to have problems. Later design transmissions were designed to use engine oils (synthetic) as the primary lubricant with a winter and summer grade the same as used in the engines. Even though the gearboxes were designed to use the synthetic oil, the problem of high point contact loading was not solved. And, under certain conditions the film strength will deteriorate and the gears and bearings will run metal-to-metal and that is when the wear and deterioration and subsequent failure will occur.
Once again I reiterate Spectrometric Oil Analysis will detect the impending breakdown of the oil as well as to detect the incipient wear of the lubricated parts.
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Steve,
From the US Pilot-Controller's glossary:
PAN-PAN- The international radio-telephony urgency signal. When repeated three times, indicates uncertainty or alert followed by the nature of the urgency.
So, IAW it would be: "Pan Pan, Pan Pan, Pan Pan ... message."
Now, being realistic, on a congested freq, I'd go for "Mayday, Mayday, Mayday" - shorter syllables and gets off the toungue quicker eh?
[ 09 January 2002: Message edited by: RW-1 ]</p>
From the US Pilot-Controller's glossary:
PAN-PAN- The international radio-telephony urgency signal. When repeated three times, indicates uncertainty or alert followed by the nature of the urgency.
So, IAW it would be: "Pan Pan, Pan Pan, Pan Pan ... message."
Now, being realistic, on a congested freq, I'd go for "Mayday, Mayday, Mayday" - shorter syllables and gets off the toungue quicker eh?
[ 09 January 2002: Message edited by: RW-1 ]</p>
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Concerning the earlier question about chip lights preceeding a major failure, it would be hard to prove in many cases, but I'm aware of at least one case where the chip light probably did prevent a large bang.
I was FTE on an options development program using a brand new BK117-A3. We had one engine chip light at about 10 hours total airframe time. We found what we though was normal manufacturing fuzz on the magnetic plug. The plug was cleaned, and we pressed on. About 5 flying hours later, we had another light on the same engine.
This time we found some bigger chunks on the plug, and did a more thorough investigation of the helicopter. The first thing we found was slivers of turbine blade material imbedded in the tail rotor. The next thing we found was a crumbling bearing on the power turbine shaft, which was permitting enough radial slop on the shaft to allow the turbine to rub on the ID of its housing. The tips of the blades looked liked they had been chewed by rats.
This is exactly the failure mechanism that previously produced at least one fatal accident in an LTS 101 powered twin. The engine operated with the crumbling bearing long enough to cause the turbine to come apart completely, and chunks of it took out the other engine.
The only reason I'm able to tell you about this today is because our pilot was a "by the book" man, and he shut down the engine when the light came on (as per the FLM of that time).
I was FTE on an options development program using a brand new BK117-A3. We had one engine chip light at about 10 hours total airframe time. We found what we though was normal manufacturing fuzz on the magnetic plug. The plug was cleaned, and we pressed on. About 5 flying hours later, we had another light on the same engine.
This time we found some bigger chunks on the plug, and did a more thorough investigation of the helicopter. The first thing we found was slivers of turbine blade material imbedded in the tail rotor. The next thing we found was a crumbling bearing on the power turbine shaft, which was permitting enough radial slop on the shaft to allow the turbine to rub on the ID of its housing. The tips of the blades looked liked they had been chewed by rats.
This is exactly the failure mechanism that previously produced at least one fatal accident in an LTS 101 powered twin. The engine operated with the crumbling bearing long enough to cause the turbine to come apart completely, and chunks of it took out the other engine.
The only reason I'm able to tell you about this today is because our pilot was a "by the book" man, and he shut down the engine when the light came on (as per the FLM of that time).
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Hi guys,
After a few phone calls I have got hold of a copy of the BK117 Flight Manual Supplement titled "Alternate Proceedures - Eng Chip Light On". As mentioned earlier it does in fact allow the pilot to bring the effected engine back to idle and monitor the gauges accordingly. It then goes on to say that prior to landing you may bring the engine back up to the fly position and execute an AEO landing.
This supplement came about due to the fact that the engine manufacturer's proceedure's state that you may bring the donk back to idle and monitor the instruments, and execute an emergency shut down if secondary indications are apparent. It seems that it is only in BK Flight Manual that you must shut down the engine, hence it wasn't too difficult for the CAR 35 guys to get the supplement put through.
Cheers
After a few phone calls I have got hold of a copy of the BK117 Flight Manual Supplement titled "Alternate Proceedures - Eng Chip Light On". As mentioned earlier it does in fact allow the pilot to bring the effected engine back to idle and monitor the gauges accordingly. It then goes on to say that prior to landing you may bring the engine back up to the fly position and execute an AEO landing.
This supplement came about due to the fact that the engine manufacturer's proceedure's state that you may bring the donk back to idle and monitor the instruments, and execute an emergency shut down if secondary indications are apparent. It seems that it is only in BK Flight Manual that you must shut down the engine, hence it wasn't too difficult for the CAR 35 guys to get the supplement put through.
Cheers
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Steve 76 hope this helps
CAP 413 (Admittedly an old one) states:-
Urgency signal:-
PAN PAN Preferably spoken 3 times
An urgency message should, as far as the time and circumstances permit, consist of the urgency signal and the following information which, if possible should be passed in the following order
The name of the station addressed (when appropriate)
The callsign and type of aircraft
Nature of the urgency condition
Intention of person in command
Present position, flight level / altitude and heading
Pilot qualification
Any other useful information
If I've overlooked anything I'm sure that I'll be corrected by my colleagues. And if the CAA want me for breach of copyright I'll be hiding in the shed.
CAP 413 (Admittedly an old one) states:-
Urgency signal:-
PAN PAN Preferably spoken 3 times
An urgency message should, as far as the time and circumstances permit, consist of the urgency signal and the following information which, if possible should be passed in the following order
The name of the station addressed (when appropriate)
The callsign and type of aircraft
Nature of the urgency condition
Intention of person in command
Present position, flight level / altitude and heading
Pilot qualification
Any other useful information
If I've overlooked anything I'm sure that I'll be corrected by my colleagues. And if the CAA want me for breach of copyright I'll be hiding in the shed.
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Just further to my previous comments about FMS that allow pilots to decide if they want to shut down or retard and engine(on the BK 117).....The SA 365C1 I am flying has the option written into the emrgencies section of the flight manual itself.
For the C models with overspeed protection fitted, the Flight Manual states "For engine not fitted with OVERSPEED LIMITERS-shut down relevant engine immediately".
It doesn't actually state why, but having just spoke to the engineer he informs me that OLDER Arriel engines had a penchant for the intermediate pinion in the Module 5 letting go. This happened on a Squirrel in Tasmania some years ago. This would cause the NTL or free turbine to overspeed as it stops driving the fan. The Overspeed protector shuts down the engine immediately this occurs. Don't know if its a good thing or not letting it get that far if you have preliminary warnings that the free turbine is about to s**t itself via the chip light coming on. Don't need it letting go and taking out the good one. But, it is fitted and gives the pilot the option.
For the C models with overspeed protection fitted, the Flight Manual states "For engine not fitted with OVERSPEED LIMITERS-shut down relevant engine immediately".
It doesn't actually state why, but having just spoke to the engineer he informs me that OLDER Arriel engines had a penchant for the intermediate pinion in the Module 5 letting go. This happened on a Squirrel in Tasmania some years ago. This would cause the NTL or free turbine to overspeed as it stops driving the fan. The Overspeed protector shuts down the engine immediately this occurs. Don't know if its a good thing or not letting it get that far if you have preliminary warnings that the free turbine is about to s**t itself via the chip light coming on. Don't need it letting go and taking out the good one. But, it is fitted and gives the pilot the option.
Quite right about the 5 module on the Arriel fitted to the 365c. The problem was that the chip in the 5 was non-indicating (the N is the same). The failure could occur before enough material had got as far as the chip adjacent to the oil filter.
We had a 365n on approach to a rig, the first indication the pilot had of trouble was when the fire crews turned out on the helideck. Smoke from the dying engine was clearly visible.
After touchdown the engine seized solid. The labyrinth seals for the turbine tore through the casing and were visible in the exhaust.
Then the chip light came on!!!!!!!!!!!!!
We had a 365n on approach to a rig, the first indication the pilot had of trouble was when the fire crews turned out on the helideck. Smoke from the dying engine was clearly visible.
After touchdown the engine seized solid. The labyrinth seals for the turbine tore through the casing and were visible in the exhaust.
Then the chip light came on!!!!!!!!!!!!!
Hi all,
For me it's a "Pan" call no questions. I do think though that part of the reluctance to issue a call, stems from the .... "everything's OK / don't scare the passengers" culture.
Rotorque: Let's be honest ...was part of the thought process in your actions directed to what the (fare paying) pax would think of sliding down the runway OEI??
For me it's a "Pan" call no questions. I do think though that part of the reluctance to issue a call, stems from the .... "everything's OK / don't scare the passengers" culture.
Rotorque: Let's be honest ...was part of the thought process in your actions directed to what the (fare paying) pax would think of sliding down the runway OEI??
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Scattercat,
It's a good point, and a good question. It could well be a factor in the decision making process of some pilots.
As to my situation, the 'big red light' was a bit of a give away to the pax that something was up, not only that but they ended up being diverted to a different destination due to the chip light. The answer to your question then has to be "not really", they were already scared <img src="tongue.gif" border="0">
Seriously though, it is a personal and company policy to inform the pax of any problems that we may have. It's a better PR ploy, to inform passengers 'prior', than it is to let them find out (in no uncertain terms) as they watch sparks fly from the skid tubes. I personaly would rather have the pilot tell me what was going on and what to expect at the end if the situation was reversed.
Could your question be better directed to companies that have a high public profile, or companies driven by competition?
It's a good point, and a good question. It could well be a factor in the decision making process of some pilots.
As to my situation, the 'big red light' was a bit of a give away to the pax that something was up, not only that but they ended up being diverted to a different destination due to the chip light. The answer to your question then has to be "not really", they were already scared <img src="tongue.gif" border="0">
Seriously though, it is a personal and company policy to inform the pax of any problems that we may have. It's a better PR ploy, to inform passengers 'prior', than it is to let them find out (in no uncertain terms) as they watch sparks fly from the skid tubes. I personaly would rather have the pilot tell me what was going on and what to expect at the end if the situation was reversed.
Could your question be better directed to companies that have a high public profile, or companies driven by competition?
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if either gearbox seizes in a robbie the rotors would come to a stop just as quick.
is the one way clutch always between the engine and gearbox's or do some have them between the gearbox and main rotor blades??
is the one way clutch always between the engine and gearbox's or do some have them between the gearbox and main rotor blades??
Iconoclast
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To: vorticey
The “one way clutch” (freewheeling unit) is always between the engine and the transmission. There are design differences in the physical location but the installation is as indicated above.
The EH-101 has a fracture point on the main rotor shaft so if there is a transmission seizure the fracture point will break and the main rotor will keep turning to effect an autorotation. The tail rotor drive is above the fracture point so the tail rotor will continue to rotate at the same speed.
There is one negative point in this design in that in order to break the fracture point the kinetic energy of the rotor system must be used to effect the fracture and in doing so the dampers will most likely be severely damaged. This will result in loads that were not designed for in the elastomeric bearings in the rotorhead causing them to possibly fail resulting in a crash.
The “one way clutch” (freewheeling unit) is always between the engine and the transmission. There are design differences in the physical location but the installation is as indicated above.
The EH-101 has a fracture point on the main rotor shaft so if there is a transmission seizure the fracture point will break and the main rotor will keep turning to effect an autorotation. The tail rotor drive is above the fracture point so the tail rotor will continue to rotate at the same speed.
There is one negative point in this design in that in order to break the fracture point the kinetic energy of the rotor system must be used to effect the fracture and in doing so the dampers will most likely be severely damaged. This will result in loads that were not designed for in the elastomeric bearings in the rotorhead causing them to possibly fail resulting in a crash.
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Lu
This is a small point and it might be wrong, but I believe that the chip light and a spectrometric oil analysis serve two different purposes.
The selection of gears is based on their strength and on their durability. A chip light will detect a 'piece' of a gear, due to a lack of strength. The spectrometric oil analysis detects excessive wear, due to a lack of durability. The former being much more dangerous than the latter.
If this is wrong, I would appreciate being corrected.
This is a small point and it might be wrong, but I believe that the chip light and a spectrometric oil analysis serve two different purposes.
The selection of gears is based on their strength and on their durability. A chip light will detect a 'piece' of a gear, due to a lack of strength. The spectrometric oil analysis detects excessive wear, due to a lack of durability. The former being much more dangerous than the latter.
If this is wrong, I would appreciate being corrected.