ATSB....Is this another dud report? Power Loss at night in NT
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read the same report when it came out with a similar feeling of.... is that it? Mind you some NTSB reports give the same aftertaste - or maybe I'm reading the wrong versions.
Last edited by Lumps; 25th Jan 2013 at 19:25.
Oil is a bit of a black art in Automotive circles, but even more so in Aviation. Recommended oil levels are rarely stated, simply sump capacity and minimum level. The sump capacity is determined by taking the minimum level, the endurance of the aircraft, the maximum permissible oil consumption of the engine and multiplying it out. There is no concern for clearance or windage losses or clearance to the crank. This is why so any aircraft spit oil out the breather at high levels and why most owners run the oil level more toward the minimum.
Engines will continue to run happily up to a point where the engine will suffer fluctuating oil pressure because the pump has trouble picking it up. The first casualty will probably be the top end ( valve gear) then the bearings due to heart stress. I suspect that an engine might happily run down to a coupe of litres.
I agree with an earlier post that running out of oil is more likely to be a ceased engine and large scale damage rather then dropping a big end cap and " putting a leg out of bed". Dropping a big end cap could have a number if causes, but I think they will all all into the general category of poor assembly.
I'm looking forward to reading the report now!
Engines will continue to run happily up to a point where the engine will suffer fluctuating oil pressure because the pump has trouble picking it up. The first casualty will probably be the top end ( valve gear) then the bearings due to heart stress. I suspect that an engine might happily run down to a coupe of litres.
I agree with an earlier post that running out of oil is more likely to be a ceased engine and large scale damage rather then dropping a big end cap and " putting a leg out of bed". Dropping a big end cap could have a number if causes, but I think they will all all into the general category of poor assembly.
I'm looking forward to reading the report now!
Last edited by Old Akro; 26th Jan 2013 at 04:53.
Has this report changed? I can't find the language that was complained of by the early posters.
I don't see much wrong with the report, other than it is so lightweight & scant on detail as to be useless.
The fist question that comes to mind is how many hours the aircraft & engine had on them. Was this engine straight out of rebuild? The numbers are written on the MR, I doubt that it would take the full resources of the ATSB to have found this out. Maybe a technique that I've used could be useful. You ring the guy up in the NT and ask him to fax you a copy. It's also probably more relevant than the PAL status of a private strip, yet they seemed to get excited about that.
The maintenance organisation is technically correct in that the engine failure was caused by the con rod cap failure. But anyone posessing more insight than the ATSB ( ie basically anyone) will ask why the con rod cap separated. Were the bolts intact, but missing? Were the bolts broken? Are there signs that the slipper bearings rotated? Are there signs of heat stress? Are the con rod cap bolts tight on the other 5? Are the main bearing cap bolts tight? Have the correct bolts been used? Do they all match, or has someone picked up bolts from the hangar floor?
One would hypothesise that the oil pressure was low at startup because the con rod cap was starting to get loose, making a larger gap for oil to flow out, thus dropping he pressure. This would have been accompanied by a change in engine sound. Did the pilots notice this? Did anyone ask?
This is an amateur report - its actually sub amateur standard. We deserve better from our statutory bodies.
The pilots did a pretty good job, but you'd probably like to be doing some sort of check ( in the interest of the safety of others) that there isn't a wider problem with engine parts or the shop that rebuilt the engine. Maybe I've missed something, but that's what I thought the ATSB was there for.
I don't see much wrong with the report, other than it is so lightweight & scant on detail as to be useless.
The fist question that comes to mind is how many hours the aircraft & engine had on them. Was this engine straight out of rebuild? The numbers are written on the MR, I doubt that it would take the full resources of the ATSB to have found this out. Maybe a technique that I've used could be useful. You ring the guy up in the NT and ask him to fax you a copy. It's also probably more relevant than the PAL status of a private strip, yet they seemed to get excited about that.
The maintenance organisation is technically correct in that the engine failure was caused by the con rod cap failure. But anyone posessing more insight than the ATSB ( ie basically anyone) will ask why the con rod cap separated. Were the bolts intact, but missing? Were the bolts broken? Are there signs that the slipper bearings rotated? Are there signs of heat stress? Are the con rod cap bolts tight on the other 5? Are the main bearing cap bolts tight? Have the correct bolts been used? Do they all match, or has someone picked up bolts from the hangar floor?
One would hypothesise that the oil pressure was low at startup because the con rod cap was starting to get loose, making a larger gap for oil to flow out, thus dropping he pressure. This would have been accompanied by a change in engine sound. Did the pilots notice this? Did anyone ask?
This is an amateur report - its actually sub amateur standard. We deserve better from our statutory bodies.
The pilots did a pretty good job, but you'd probably like to be doing some sort of check ( in the interest of the safety of others) that there isn't a wider problem with engine parts or the shop that rebuilt the engine. Maybe I've missed something, but that's what I thought the ATSB was there for.
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Well, we can rule out bird strike.
There are only three pertinent things we can glean from this patronising, smug report. (a) The donkey quit, (b) the lights at the alternate didn't perform design function; and (c) the boys did a good job.
If you're operating a similar engine mark or model it may be handy to know why this donkey turned it's toes up. That's a fairly large hole in the thing and unless someone has developed armour piercing budgies, we can rule out bird strike.
So, we have not a scrap of useful report information, no crash comic to find the analysis in, and need to check the ATSB web site everyday to make sure that a safety recommendation has not been slipped in there.
There's probably enough engineering expertise here on Pprune to draft a report for the ATSB, maybe we should; just to show how to do it, 'cos they do seem to have forgotten how.
If you're operating a similar engine mark or model it may be handy to know why this donkey turned it's toes up. That's a fairly large hole in the thing and unless someone has developed armour piercing budgies, we can rule out bird strike.
So, we have not a scrap of useful report information, no crash comic to find the analysis in, and need to check the ATSB web site everyday to make sure that a safety recommendation has not been slipped in there.
There's probably enough engineering expertise here on Pprune to draft a report for the ATSB, maybe we should; just to show how to do it, 'cos they do seem to have forgotten how.
Last edited by Kharon; 26th Jan 2013 at 23:25. Reason: Ambles off into the rain, muttering dark curses.
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Here is a link to a UK AAIB report for comparison of content, style and depth. I think it states preliminary too.
Air Accidents Investigation: Download PDF document
A previous detailed ATSB report on aircraft VH-WRT
http://www.atsb.gov.au/media/1537651/ao2008072.pdf
Just randomly selected from google search.
Air Accidents Investigation: Download PDF document
A previous detailed ATSB report on aircraft VH-WRT
http://www.atsb.gov.au/media/1537651/ao2008072.pdf
Just randomly selected from google search.
NTSB v ATSB difference in methodology and regulator overkill!
Come across several articles/blogs on the latest controversy on a proposed FAA AD for continental engines in the States, which IMO is particularly relevant to this thread for a number of reasons. But first a quote from the Avweb site:
So the only significant point of similarity between the US and Oz is possible regulator overkill on the proposed AD and no CBA (apparently) on the knock on effect of bringing in the AD...boy does that sound familiar??
However that is where the similarities stop!
Firstly we have at least two reputable aviation associations, EAA and AOPA, who are not afraid to speak out about the potential ramifications of the FAA bringing in the proposed AD. Both of these organisations (amongst many others) are known to have significant political clout in the US and the FAA would ignore their concerns on the proposed AD at their peril.
Next we have a stark difference in the transport safety investigator's (ATSB with the thread incident and the NTSB SR) methodology and response to a significant safety issue. Here is part of the NTSB analysis and reason for issuing SR A-12-007 :
Get the picture?? {NB Feel free to read the entire SR}.
IMO this highlights more than anything else the significant importance of the long standing practice, by safety investigative agencies around the world, of issuing safety recommendations when a significant safety issue is brought to the attention of the investigators. Which, as we now know, is contrary to the current opinion/methodology adopted by ATSBeaker i.e. "a SR is definitely a last resort because we don't want to offend any directly interested parties"!
Hmm..perhaps this incident should be another that the TSB Canada do a comparitive difference in methodology and practice??
User Groups: Cylinder AD Proposal Risky, Costly
AOPA and EAA responded this week to the FAA's proposed airworthiness directive that would require thousands of GA aircraft owners to inspect and replace their ECi engine cylinders, saying the FAA's plan would impose a financial burden while also compromising safety. “Requiring the replacement of so many cylinders, in addition to repetitive inspections, goes well beyond the [NTSB] recommendations [PDF]," said Robert Hackman, AOPA's vice president of regulatory affairs. Hackman said he also is concerned that actual costs "could go well beyond the FAA’s estimate, and that the mass replacement of cylinders in the field would downgrade, rather than enhance safety." EAA noted that the proposed AD does not cite either specific failure rates or a total number of failures for the ECi cylinders.
The AD "does not point to a single accident or injury caused by the failure of any ECi cylinder," EAA said. Both groups said they are working on a written response to the proposal. AOPA also encouraged members to post comments to the FAA docket, highlighting their operating experience with the cylinders. The FAA has set a deadline of October 11 for comments. EAA said it will insist on a comment period extension, "given the very high cost of the proposed AD, and the almost impossibility of finding enough cylinders to replace the ECi units if the AD were to become law."
AOPA and EAA responded this week to the FAA's proposed airworthiness directive that would require thousands of GA aircraft owners to inspect and replace their ECi engine cylinders, saying the FAA's plan would impose a financial burden while also compromising safety. “Requiring the replacement of so many cylinders, in addition to repetitive inspections, goes well beyond the [NTSB] recommendations [PDF]," said Robert Hackman, AOPA's vice president of regulatory affairs. Hackman said he also is concerned that actual costs "could go well beyond the FAA’s estimate, and that the mass replacement of cylinders in the field would downgrade, rather than enhance safety." EAA noted that the proposed AD does not cite either specific failure rates or a total number of failures for the ECi cylinders.
The AD "does not point to a single accident or injury caused by the failure of any ECi cylinder," EAA said. Both groups said they are working on a written response to the proposal. AOPA also encouraged members to post comments to the FAA docket, highlighting their operating experience with the cylinders. The FAA has set a deadline of October 11 for comments. EAA said it will insist on a comment period extension, "given the very high cost of the proposed AD, and the almost impossibility of finding enough cylinders to replace the ECi units if the AD were to become law."
However that is where the similarities stop!
Firstly we have at least two reputable aviation associations, EAA and AOPA, who are not afraid to speak out about the potential ramifications of the FAA bringing in the proposed AD. Both of these organisations (amongst many others) are known to have significant political clout in the US and the FAA would ignore their concerns on the proposed AD at their peril.
Next we have a stark difference in the transport safety investigator's (ATSB with the thread incident and the NTSB SR) methodology and response to a significant safety issue. Here is part of the NTSB analysis and reason for issuing SR A-12-007 :
Reciprocating engine cylinder assemblies consist of two major parts, the cylinder barrel and the cylinder head. ECi cylinder heads are manufactured from an aluminum alloy casting, and house the intake and exhaust valves, with their respective seats, guides, and spark plugs. ECi cylinder barrels are typically manufactured from an alloy steel forging and have a smooth bore that houses the piston. The cylinder head and barrel are joined by heating the cylinder head to about 650° F then screwing it onto the cylinder barrel until specific surfaces make contact. As the cylinder head cools and shrinks onto the cylinder barrel, an interference fit is produced, locking the parts together at the threads and at an adjacent plain diameter, which is commonly referred to as a shrink band (shrink bands are features on the barrel and in the cylinder head; see figure 2). On new cylinder assemblies, the barrel mounting flange and cylinder mounting holes in the flange are machined after assembly to ensure the cylinder’s proper alignment on the engine case.
In most of the cases examined by the NTSB, the fatigue cracks in the cylinder heads initiated at the root of the thread that was engaged with the first (uppermost) thread on the cylinder barrels, as shown in figure 1 and indicated by the yellow line in figure 2. The fatigue cracks propagated outwards through the cylinder head wall to emerge between the third and fourth or the fourth and fifth cooling fin, depending on the engine model.
The fatigue cracks initiated at multiple locations, typically near the intake or exhaust valve side of the cylinder heads and, with engine use, propagated through the head thickness. Once the fatigue cracks propagated though the thickness of the cylinder wall, the cylinders lost compression, with a resulting reduction in or total loss of thrust. When the fatigue cracks reached a critical size, the cylinder heads fractured and separated at the fatigue location, with the lower portion remaining attached to the barrels, resulting in catastrophic engine failure.
Beginning in 2004, ECi and the FAA issued several bulletins and directives to address these fatigue failures. After 34 reported fatigue failures of ECi cylinders, the FAA issued AD 2004-08-10, effective May 2004, to require replacement of certain ECi cylinder assemblies on TCM model 520 and 550 series engines. The AD identified a manufacturing discrepancy that occurred between September 2002 and May 2003 (S/N 1044-7708), which resulted in an inadequate cylinder head wall thickness and an over-hardened condition that would reduce the fatigue strength of the aluminum cylinder head.
In August 2006, ECi issued Mandatory Service Bulletin (MSB) 06-2 instructing operators to perform repetitive inspections for leaks and cracks on cylinder assemblies between S/N 7709 and 33696 and to replace any discrepant cylinders. Affected assemblies were produced between September 2002 and November 2005 with inadequate cylinder head wall thickness on the exhaust side. At least 21 head separations have been reported for this group of cylinders, and the NTSB has investigated several of these, including those documented in NTSB case number ENG07SA033.
The fatigue initiated on the exhaust side of the cylinder head, between the 14th and 16th cooling fins, and propagated inwards toward the valve seat. The FAA issued Special Airworthiness Information Bulletin (SAIB) NE-07-09R1 in March 2007, detailing the importance of performing the inspections called for in ECi MSB 06-2, but did not require the inspections.
In most of the cases examined by the NTSB, the fatigue cracks in the cylinder heads initiated at the root of the thread that was engaged with the first (uppermost) thread on the cylinder barrels, as shown in figure 1 and indicated by the yellow line in figure 2. The fatigue cracks propagated outwards through the cylinder head wall to emerge between the third and fourth or the fourth and fifth cooling fin, depending on the engine model.
The fatigue cracks initiated at multiple locations, typically near the intake or exhaust valve side of the cylinder heads and, with engine use, propagated through the head thickness. Once the fatigue cracks propagated though the thickness of the cylinder wall, the cylinders lost compression, with a resulting reduction in or total loss of thrust. When the fatigue cracks reached a critical size, the cylinder heads fractured and separated at the fatigue location, with the lower portion remaining attached to the barrels, resulting in catastrophic engine failure.
Beginning in 2004, ECi and the FAA issued several bulletins and directives to address these fatigue failures. After 34 reported fatigue failures of ECi cylinders, the FAA issued AD 2004-08-10, effective May 2004, to require replacement of certain ECi cylinder assemblies on TCM model 520 and 550 series engines. The AD identified a manufacturing discrepancy that occurred between September 2002 and May 2003 (S/N 1044-7708), which resulted in an inadequate cylinder head wall thickness and an over-hardened condition that would reduce the fatigue strength of the aluminum cylinder head.
In August 2006, ECi issued Mandatory Service Bulletin (MSB) 06-2 instructing operators to perform repetitive inspections for leaks and cracks on cylinder assemblies between S/N 7709 and 33696 and to replace any discrepant cylinders. Affected assemblies were produced between September 2002 and November 2005 with inadequate cylinder head wall thickness on the exhaust side. At least 21 head separations have been reported for this group of cylinders, and the NTSB has investigated several of these, including those documented in NTSB case number ENG07SA033.
The fatigue initiated on the exhaust side of the cylinder head, between the 14th and 16th cooling fins, and propagated inwards toward the valve seat. The FAA issued Special Airworthiness Information Bulletin (SAIB) NE-07-09R1 in March 2007, detailing the importance of performing the inspections called for in ECi MSB 06-2, but did not require the inspections.
IMO this highlights more than anything else the significant importance of the long standing practice, by safety investigative agencies around the world, of issuing safety recommendations when a significant safety issue is brought to the attention of the investigators. Which, as we now know, is contrary to the current opinion/methodology adopted by ATSBeaker i.e. "a SR is definitely a last resort because we don't want to offend any directly interested parties"!
Hmm..perhaps this incident should be another that the TSB Canada do a comparitive difference in methodology and practice??
Last edited by Sarcs; 15th Aug 2013 at 02:34. Reason: Beaker's 'beyond all reason' world's best practice..I don't think so!
I think my over fifty years in aviation, many hours as a Flight Engineer as well as a background in ground engineering in the engine trade taught me a fair bit. One of the lessons learned is that decreasing oil quantity leads to increased oil temperature which in turn leads to loss of oil pressure. No Old Wives Tale Jabba, just experience.
On two occasions in 737-200 with Pratt & Whitney JT8D -17 engines I have seen severe loss of oil contents.
One at 31,000 ft in cruise due to an O-Ring problem and the other an incorrectly fitted oil filler cap. Oil levels fell from full to 10% full or 90% empty if you like. There was no rise in oil temperature and no loss of oil pressure. On my flight I shut down the engine as a precaution. The second occasion I was a passenger and the pilot elected not to shut it down and flew for a further three hours to destination. No Old Wives tale- just experience
Last edited by Centaurus; 15th Aug 2013 at 14:19.
I think my over fifty years in aviation, many hours as a Flight Engineer as well as a background in ground engineering in the engine trade taught me a fair bit. One of the lessons learned is that decreasing oil quantity leads to increased oil temperature which in turn leads to loss of oil pressure.
It could depend on whether or not it was a dry or wet sump system, how efficient the oil cooling system was and probably most importantly where the oil temp sensor is located.
In the case of the position of the temp sensor the oil temp may well be increasing but the sensor isn't measuring that increase. To give an example I had a car that once the water level had dropped a bit in the radiator the temperature sensor was no longer on contact with the water and was then only measuring the ambient temperature of the radiator.
Remember also many modern oils are multi grade and retain their viscosity over a wide range of temperatures so there may not be a noticeable change in oil pressure.
Ah, the history of GA writ large …
A million engines run for a billion hours, and still an argument starts about whether oil temperature will increase when oil is lost from an engine.
Doesn’t it depend on the kind of engine and lubrication system, the reason for the oil loss, the location and operation of the sensors driving the cockpit indications, the phase of the moon and the pilot’s star sign?
(PS: The ATSB report the subject of this thread was crap.)
A million engines run for a billion hours, and still an argument starts about whether oil temperature will increase when oil is lost from an engine.
Doesn’t it depend on the kind of engine and lubrication system, the reason for the oil loss, the location and operation of the sensors driving the cockpit indications, the phase of the moon and the pilot’s star sign?
(PS: The ATSB report the subject of this thread was crap.)
