plane crash in Lagos Nigeria
It also is hinted at that the problems with the left engine may have started on the prior leg. Note that the Captain delayed boarding and the FO reiterated not to board while the had a long private discussion. The first sign of this type of failure is slow acceleration of the engine. Note also the comment about getting the aircraft home.
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It appears that this report is written by the Accident Investigation Board(AIB) in a way that is meant to lead the reader to make certain assumptions and conclusions without actually making those conclusions itself because of the lack of incontrovertible evidence.
After reading through the report the following thoughts run through my mind…
1. The report attempts to make the PIC look as if he is a weak pilot by mentioning repeatedly his difficulties in training and his violation by the FAA. The circumstances and exact nature of the violation are not mentioned. However, much of the listed training difficulties were related simply to RT procedures. However, there was mention of checklist use as well.
“The Captain had previous regulatory issues with the U.S.A Federal Aviation Administration (FAA) which led to his suspension at that time.”
“The pilot was suspended in 2009 by the United States Federal Aviation Administration (FAA) for some misdemeanours related to a heavy landing and fixing of panels that were neither entered in the aircraft logbook nor reported.”
“The line trainings that preceded the captain’s checkout had a lot of adverse remarks made by the training captain.”
2. This was an airline that had poor maintenance practices and was a difficult airline to work for.
“Witness accounts, from former Dana Airlines pilots, suggested an undesirable maintenance culture and defects not being entered in aircraft log books. They also mentioned other unhealthy work practices bordering on restricted background checks and references. AIB investigated these interview accounts and confirmed some of the alleged practices for which safety recommendations were issued.”
“Other witness’s accounts were recorded, mostly from former pilots of the airline. They gave their various perceptions/opinions about Dana Airlines Nigeria Limited maintenance culture and other safety related issues e.g. the habit of not entering defects in the technical log book. Most of them left the airline either sacked or frustrated out of the company and are being owed various amounts of money.”
3. Pilots at Dana Airlines also had a tendency to knowingly operate the aircraft in a condition that was less than safe although the reasons for doing this were not mentioned.
“the Bureau discovered that some of the former pilots of the Airlines were involved in some of these malpractices. These pilots failed to report these non-entries into the technical log book to the appropriate authorities when they were in the service of the Airline.”
4. The report states that there was an issue with the Pratt & Whitney JT8D-200 engines in which the thermal expansion of the engine was causing stress on the secondary fuel manifold assemblies resulting in fracture of the manifold(each engine has a left and right manifold). Failure of one of the fuel lines will lead to a situation where the engine is still operating but will not respond to throttle movement due to the fuel in the fractured manifold leaking instead of powering the engine. P&W issued a service bulletin(SB) in 2003, a full nine years before the accident about this problem. Completing the SB involves installing a replacement secondary fuel manifold assembly fabricated with new tube material, which has a significantly greater fatigue life than the old tube material.
In addition to thermal engine expansion causing stress on the secondary manifold assembly, improper maintenance such as installation of distorted manifolds and incorrect shimming of the manifold during installation can have the same result. The manifold consists of two fuel lines and is located(at least partially) in the fan air discharge area of the engine. The two fuel lines are enclosed in fairings to provide protection from the fan air. If the fairing is improperly installed, fan air can impinge on the associated fuel lines leading to failure.
The AIB also stated that the P&W should have made the Service Bulletin an Alert Bulletin which would have placed a higher level of urgency about the issue and therefore resulted in more compliance. As well, if the installation were to “fit only in one direction, the issue of incorrect shimming during manifold installation would be eliminated”. The AIB has recommended that the FAA issue an AD about this problem.
5. Dana Air had three engines overhauled at Millenium Engine Associates in Florida(which subsequently changed its name after the accident) that were specifically discussed in the report. All three engines(two of which were on the accident aircraft) had poor maintenance work performed on them by Millenium. Two of the three overhauled engines did not have the SB done(one of which was on the accident aircraft). That being said, a Service Bulletin is not mandatory. There is no discussion for the reason why the SB was not done on two of the engines
6. On the accident flight, both engines appear to have had some sort of malfunction. The third engine overhauled Millenium also had a malfunction at some point after the accident and was examined for the report due to it’s malfunction being similar to the accident aircraft. The engine malfunctions that occurred were not a complete engine failure but instead, a loss of ability to increase the thrust from near idle similar to the previous malfunctions that led to the service bulletin.
7. The report states twice that prior to departure for this flight, the captain did not want passengers using the aft stairs although there is no reason given as to why this might be the case(such as a known fuel leak).
“On arrival of the aircraft in Abuja, the ground staff asserted that the Captain ordered that the rear passenger exit door should not be opened nor used for passenger disembarkation/embarkation.”
8. The report states that prior to departure of the accident flight, the pilots had an onboard meeting with all the other crewmembers which delayed boarding, which is a bit unusual. But there is no information available in the report as to what was said at the meeting. One is left to wonder if the AIB feels that perhaps the pilots of the accident flight were significantly concerned about something prior to departure on the accident flight such as a previously experienced engine malfunction and wanted to discuss it.
“At two separate times, the Station Manager and the Duty Ramp Officer requested permission from the Captain to board the passengers. This was refused first by the Captain and secondly by the First Officer as both stated that they were having a meeting with the crewmembers. Details of this meeting were not known to anyone. These were all confirmed by Dana Airlines Nigeria Limited ground personnel in Abuja.”
9. The report twice mentions that the flight requested to hold short of the runway for an undetermined but possibly longer than normal time period, perhaps suggesting that the pilots were concerned about something and possibly wanted to confirm engine operation prior to takeoff. However, the CVR was overwritten for the first portion of the flight, so there was no evidence of what the reason was for the delay prior to takeoff.
“According to the ATC ground recorder transcript, the aircraft was cleared to line-up on runway 04 and wait, but the crew requested for some time before lining-up.”
10. The report states that the captain was not properly using the normal checklists if using them at all. How this was determined is unknown as the CVR starts sixteen minutes after takeoff. According to the report, the proper non-normal checklists were not followed when the first engine malfunctioned with the engine still running but not responding to throttle movement. Whether using the checklist would have made any difference is unknown, except that the engine shutdown checklist does say to land at the nearest suitable airport. Whether reading that item would have prompted the captain to actually land at the nearest suitable airport is not known but somehow seems unlikely.
“The Cockpit Voice Recorder (CVR) retained about 30 minutes 53 seconds of the flight and started recording at 1513:44hrs by which time the Captain and First Officer (F/O) were in a discussion of a non-normal condition regarding the correlation between the engine throttle setting and an engine power indication.”
“From evidence available, there was never any call for the checklist both normal and non-normal/emergency throughout the entire flight and the use of the Quick Reference Hand Book (QRH) was never detected.”
11. The report makes it seem as if there is some antagonism between the captain and at least one of the maintenance crew(possibly the one who was on the aircraft) but no further discussion about details is made about it in the report.
“During further discussions, the First Officer asked if he can call in the Engineer who was repositioning to Lagos to help analyse the problem but the Captain refused. The Captain concluded, 'well I don’t need him here cause we can figure it out, he’s not going to be able to help us'. During the period that the flight crew were discussing and trying to manage the situation they were facing, the Captain also asked the First Officer if any Engineer had tampered with the panel by the rear exit door on ground Abuja and finally concluded that 'this is the guy that had an issue with us. uh he’s pissed off at us'; according to the CVR transcript."
12. The report states that the left engine was the first one to experience difficulties with thrust output not matching the thrust commanded by the throttle being discussed when the CVR starts with the aircraft at cruise altitude. As the flight was filed a FL330 but the report never mentions an altitude above FL 260, it is suspected that there was an issue during the climb. The left engine was operated at low power during a portion of cruise flight. During the descent, the left engine had no response to throttle input while the right engine was confirmed to still be operating.
“The Cockpit Voice Recorder (CVR) retained about 30 minutes 53 seconds of the flight and started recording at 1513:44hrs by which time the Captain and First Officer (F/O) were in a discussion of a non-normal condition regarding the correlation between the engine throttle setting and an engine power indication.”
“The flight however continued towards Lagos as the crew continuously discussed the problem with vague references to EPR and nonresponse from the throttle inputs, with the left engine operating at idle power or inoperative.”
“At 1531:12hrs, the crew confirmed that there was no throttle response on the left engine and subsequently the Captain took over control as Pilot Flying (PF) at 1531:27hrs. The flight was however continued towards Lagos with no declaration of any distress message. With the confirmation of throttle response on the right engine, the engine anti-ice, ignition and bleed-air were all switched off. At 1532:05hrs, the crew observed the loss of thrust in No.1 Engine of the aircraft.”
13. During the initial descent, the captain seemed satisfied that the right engine was operating normally. No distress call was made. However, the F/O did suggest switching from runway 18L to the much longer 18R which was requested and approved by ATC.
“With the confirmation of throttle response on the right engine, the engine anti-ice, ignition and bleed-air were all switched off. At 1534:33hrs the Captain confirmed that “okay this one is good for us so far”.
14. There were some discussions between the pilots about the profile to be flown and that was being flown during the descent. Initially it was decided “that they should start a gradual descent”. During the initial descent, the captain wanted a higher descent rate while the F/O preferred to remain on a higher profile. Later on, however, the F/O stated that the aircraft was high at which point it was decided to start extending flaps. At this point one engine was believed to be operating normally.
“During the initial descent, the Captain wanted the F/O who was then the Pilot Flying (PF) to increase the rate of descent but the F/O stated that he would prefer a gradual descent in order to have enough height over Lagos.”
“At the same time, the crew also carried out some of the pre-landing tasks that included the extension of slats at 1537:07hrs and the speed-brakes were deployed at 1537:10hrs. The First Officer indicated that they were slightly high and the Captain replied that he was correcting and then requested for flaps eleven. At 1537:53hrs the Captain further requested for flaps one-five (flaps fifteen)."
15. The report states that the engine-out profile was not flown, however, the report does not say what this profile is or provide a copy of the manufacturer’s engine-out profile. The aircraft appears to have ended up on a 3 to 1 profile but with high drag items deployed while still quite far from the airport. Subsequently, they descended below the 3 to 1 path with further deployment of high drag items. The gear was selected down at around 20 miles from the airport.
“At 1537:53hrs the Captain further requested for flaps one-five (flaps fifteen). At 1538:35hrs, both crew indicated that they were 21 miles on the localizer. At 1538:54hrs, there was EGPWS automated voice warning of “landing gear” which the Captain responded to at 1539:10hrs by requesting for the landing gear to be selected down.”
“1540:42hrs, he confirmed to the Captain that they were five thousand, fifteen miles, which the Captain acknowledged with an increase in the rate of descent.”
16. After increasing the drag significantly with gear and partial flap extension, there was a requirement to add thrust on the remaining engine. It was around this time that it was discovered that the second engine was not increasing power in response to throttle input, although it was still operating. An emergency was declared after this was discovered but no checklist was called for.
“According to the CVR transcript at 1541:46hrs the First Officer inquired if “both engines come up” and the Captain replied “negative” at 1541:48hrs. The two engines finally did not respond to throttle inputs as both engines failed to produce the commanded thrust.”
17. After the second engine malfunction, the captain asked initially for more flap, then decided to retract the gear and flaps. The timing of his calls for flap/gear retraction differ in two sections of the final report.
“At 1542:10hrs, DANACO 0992 radioed an emergency distress call indicating "dual engine failure . . . negative response from throttle."
“At 1542:35hrs the Captain requested for flaps twenty eight which the First Officer selected. This was after the crew had declared an Emergency of dual engine failure.”
“At 1542:35hrs, the flight crew lowered the flaps further and continued with the approach and discussed landing alternatively on runway 18L. At 1542:45hrs, the Captain reported the runway in sight and instructed the F/O to retract the flaps and four seconds later to retract the landing gears.”
“At 1543:30hrs there was an automated voice of “altitude” followed by the Captain’s indication of sighting the runway at 1543:45hrs. He then instructed the First Officer to select the flaps up at 1543:49hrs followed by another instruction to select the landing gears up at 1543:50hrs."
18. Both the engines on the accident aircraft exhibited damage patterns that were similar to other engines that had suffered from a lack of response to throttle input. This included the third engine on the aircraft that later on had to make an air return. However, in the report created by the powerplants group, there was no conclusion as to the timing of the damage which perhaps is the reason that the manifold damage is not mention as a probable cause but is instead only hinted at in the report.
“Both engines’ fuel system components exhibited the same types of damage which was consistent with others that suffered lack of response to the throttles.”
“The Fuel Manifold segment from Engine #1 of Pratt & Whitney JT8D-217C revealed, during examination using stereo microscope, that the fracture was consistent with overstress separations and bending load. According to the test report, it was asserted that there was no evidence that the fracture was pre-impact. However, on the air return aircraft, the fracture was at the same position.”
19. Sixteen months after the accident, the third engine that Dana Airlines had overhauled by Millenium had a malfunction that was similar to what was experienced on the accident aircraft. The aircraft was able to return for a landing and was not damaged. It was discovered that this third engine did not have the applicable SB performed on it and that faulty work had been performed on the fuel manifold assembly.
“….improper installation of the right hand fuel manifold inlet fairing. Installation of distorted manifolds and incorrect shimming of the manifold which are capable of aggravating the condition as stated in SB 6452. There was lack of engagement of the front and rear sections of the manifold fairings on the inboard side. The engine suffered thermal stress and fractured secondary manifold feeder line resulting in loss of power and failure to respond to throttle movement.”
20. While the two engines in the accident aircraft had experienced a sudden impact of a crash potentially causing further damage, the third engine which was on a different aircraft did not suffer through an accident, yet all three had similar damage patterns signifying that the damage to the engine fuel lines happened prior to impact. There were no other engine faults aside from the fuel manifold line problems making it likely that the improper maintenance done by Millenium was the reason for the dual engine failure and accident of Danaco 992.
“All engines had primary and secondary fuel manifold assemblies fractured, cracked, bent, twisted or pinched which led to fuel leaks, fuel discharge to bypass duct, loss of engine thrust and obvious failure of engine responding to throttle movement.”
“The engines teardown were successfully carried out without any core engine anomalies detected apart from the fuel manifold issues that would have made the aircraft mechanically unsafe. However, the observed damage to the engines was consistent with low-to no rotation speed at impact but no indications of core engine hardware pre- impact malfunction was revealed at the engines teardown.”
21. The engines on the accident aircraft were sent to Millenium who appear to have had custody and control of them. A teardown examination was done by representatives from several interested parties. The engines were found to not have any evidence of damage that would have caused a failure however, both engines had fuel manifolds exhibiting signs of damage similar to the aircraft that had to make the air return due to damaged fuel manifolds. Some of the components of the second engine that failed(engine #2) that were suspected of being installed improperly were not returned by Millenium for further examination(metallurgical test by the NTSB which revealed that the manifold fractures on the left engine were consistent with overstress separations and bending load).
“The right-hand primary and secondary manifold supply tubes were bent at the No. 5 fittings. Similar damage was noted on the left-hand primary and secondary manifold supply tube at the No. 6 fittings. Neither of these bends completely obstructed flow. The left hand primary manifold also had a circumferential crack just outboard of the fan duct pass through.”
“The engine teardown was performed at Global Engine Maintenance facility (formerly Millenium Engine Associates) in the USA. The organization is also responsible for securing and ensuring that all the parts examined are returned to the engine owners with the permission of the investigating body. However, certain components such as the right fuel manifold were not available for subsequent examination.”
"Examination and disassembly of the No. 1 engine did not identify any mechanical condition which would have prevented normal operation of the engine at the time of impact."
"The lack of fuel system components still attached to the engine prevented any detailed examination and overall assessment of the condition of the fuel system pre- and post-impact."
“During the engine teardown in the USA, the organization that performed the teardown examination was supposed to have shipped the engines back to the Dana Airlines in Lagos. However, the engines were shipped without the right engine fuel manifold assembly.”
“Fuel manifold segment test from #1 Engine was performed at the NTSB laboratory in the USA. The fuel manifold from Engine #2 was not provided by the operator who had custody of the accident engines.”
22. The AIB feels that the maintenance work done by Millenium on the three engines was improper. Millenium subsequently changed its name to Global Engine Maintenance.
“The work processes, ethics and culture in Global Engine Maintenance LLC formerly known as Millenium Engine Associates Inc. are subject of concern to Nigerian Civil Aviation Authority and AIB. This concern was as a result from the discovery made in the cause of investigation in the Air Return aircraft 5N-SAI, which shows the improper installation of the right hand fuel manifold inlet fairing. Installation of distorted manifolds and incorrect shimming of the manifold which are capable of aggravating the condition as stated in SB 6452. There was lack of engagement of the front and rear sections of the manifold fairings on the inboard side.”
After reading through the report the following thoughts run through my mind…
1. The report attempts to make the PIC look as if he is a weak pilot by mentioning repeatedly his difficulties in training and his violation by the FAA. The circumstances and exact nature of the violation are not mentioned. However, much of the listed training difficulties were related simply to RT procedures. However, there was mention of checklist use as well.
“The Captain had previous regulatory issues with the U.S.A Federal Aviation Administration (FAA) which led to his suspension at that time.”
“The pilot was suspended in 2009 by the United States Federal Aviation Administration (FAA) for some misdemeanours related to a heavy landing and fixing of panels that were neither entered in the aircraft logbook nor reported.”
“The line trainings that preceded the captain’s checkout had a lot of adverse remarks made by the training captain.”
2. This was an airline that had poor maintenance practices and was a difficult airline to work for.
“Witness accounts, from former Dana Airlines pilots, suggested an undesirable maintenance culture and defects not being entered in aircraft log books. They also mentioned other unhealthy work practices bordering on restricted background checks and references. AIB investigated these interview accounts and confirmed some of the alleged practices for which safety recommendations were issued.”
“Other witness’s accounts were recorded, mostly from former pilots of the airline. They gave their various perceptions/opinions about Dana Airlines Nigeria Limited maintenance culture and other safety related issues e.g. the habit of not entering defects in the technical log book. Most of them left the airline either sacked or frustrated out of the company and are being owed various amounts of money.”
3. Pilots at Dana Airlines also had a tendency to knowingly operate the aircraft in a condition that was less than safe although the reasons for doing this were not mentioned.
“the Bureau discovered that some of the former pilots of the Airlines were involved in some of these malpractices. These pilots failed to report these non-entries into the technical log book to the appropriate authorities when they were in the service of the Airline.”
4. The report states that there was an issue with the Pratt & Whitney JT8D-200 engines in which the thermal expansion of the engine was causing stress on the secondary fuel manifold assemblies resulting in fracture of the manifold(each engine has a left and right manifold). Failure of one of the fuel lines will lead to a situation where the engine is still operating but will not respond to throttle movement due to the fuel in the fractured manifold leaking instead of powering the engine. P&W issued a service bulletin(SB) in 2003, a full nine years before the accident about this problem. Completing the SB involves installing a replacement secondary fuel manifold assembly fabricated with new tube material, which has a significantly greater fatigue life than the old tube material.
In addition to thermal engine expansion causing stress on the secondary manifold assembly, improper maintenance such as installation of distorted manifolds and incorrect shimming of the manifold during installation can have the same result. The manifold consists of two fuel lines and is located(at least partially) in the fan air discharge area of the engine. The two fuel lines are enclosed in fairings to provide protection from the fan air. If the fairing is improperly installed, fan air can impinge on the associated fuel lines leading to failure.
The AIB also stated that the P&W should have made the Service Bulletin an Alert Bulletin which would have placed a higher level of urgency about the issue and therefore resulted in more compliance. As well, if the installation were to “fit only in one direction, the issue of incorrect shimming during manifold installation would be eliminated”. The AIB has recommended that the FAA issue an AD about this problem.
5. Dana Air had three engines overhauled at Millenium Engine Associates in Florida(which subsequently changed its name after the accident) that were specifically discussed in the report. All three engines(two of which were on the accident aircraft) had poor maintenance work performed on them by Millenium. Two of the three overhauled engines did not have the SB done(one of which was on the accident aircraft). That being said, a Service Bulletin is not mandatory. There is no discussion for the reason why the SB was not done on two of the engines
6. On the accident flight, both engines appear to have had some sort of malfunction. The third engine overhauled Millenium also had a malfunction at some point after the accident and was examined for the report due to it’s malfunction being similar to the accident aircraft. The engine malfunctions that occurred were not a complete engine failure but instead, a loss of ability to increase the thrust from near idle similar to the previous malfunctions that led to the service bulletin.
7. The report states twice that prior to departure for this flight, the captain did not want passengers using the aft stairs although there is no reason given as to why this might be the case(such as a known fuel leak).
“On arrival of the aircraft in Abuja, the ground staff asserted that the Captain ordered that the rear passenger exit door should not be opened nor used for passenger disembarkation/embarkation.”
8. The report states that prior to departure of the accident flight, the pilots had an onboard meeting with all the other crewmembers which delayed boarding, which is a bit unusual. But there is no information available in the report as to what was said at the meeting. One is left to wonder if the AIB feels that perhaps the pilots of the accident flight were significantly concerned about something prior to departure on the accident flight such as a previously experienced engine malfunction and wanted to discuss it.
“At two separate times, the Station Manager and the Duty Ramp Officer requested permission from the Captain to board the passengers. This was refused first by the Captain and secondly by the First Officer as both stated that they were having a meeting with the crewmembers. Details of this meeting were not known to anyone. These were all confirmed by Dana Airlines Nigeria Limited ground personnel in Abuja.”
9. The report twice mentions that the flight requested to hold short of the runway for an undetermined but possibly longer than normal time period, perhaps suggesting that the pilots were concerned about something and possibly wanted to confirm engine operation prior to takeoff. However, the CVR was overwritten for the first portion of the flight, so there was no evidence of what the reason was for the delay prior to takeoff.
“According to the ATC ground recorder transcript, the aircraft was cleared to line-up on runway 04 and wait, but the crew requested for some time before lining-up.”
10. The report states that the captain was not properly using the normal checklists if using them at all. How this was determined is unknown as the CVR starts sixteen minutes after takeoff. According to the report, the proper non-normal checklists were not followed when the first engine malfunctioned with the engine still running but not responding to throttle movement. Whether using the checklist would have made any difference is unknown, except that the engine shutdown checklist does say to land at the nearest suitable airport. Whether reading that item would have prompted the captain to actually land at the nearest suitable airport is not known but somehow seems unlikely.
“The Cockpit Voice Recorder (CVR) retained about 30 minutes 53 seconds of the flight and started recording at 1513:44hrs by which time the Captain and First Officer (F/O) were in a discussion of a non-normal condition regarding the correlation between the engine throttle setting and an engine power indication.”
“From evidence available, there was never any call for the checklist both normal and non-normal/emergency throughout the entire flight and the use of the Quick Reference Hand Book (QRH) was never detected.”
11. The report makes it seem as if there is some antagonism between the captain and at least one of the maintenance crew(possibly the one who was on the aircraft) but no further discussion about details is made about it in the report.
“During further discussions, the First Officer asked if he can call in the Engineer who was repositioning to Lagos to help analyse the problem but the Captain refused. The Captain concluded, 'well I don’t need him here cause we can figure it out, he’s not going to be able to help us'. During the period that the flight crew were discussing and trying to manage the situation they were facing, the Captain also asked the First Officer if any Engineer had tampered with the panel by the rear exit door on ground Abuja and finally concluded that 'this is the guy that had an issue with us. uh he’s pissed off at us'; according to the CVR transcript."
12. The report states that the left engine was the first one to experience difficulties with thrust output not matching the thrust commanded by the throttle being discussed when the CVR starts with the aircraft at cruise altitude. As the flight was filed a FL330 but the report never mentions an altitude above FL 260, it is suspected that there was an issue during the climb. The left engine was operated at low power during a portion of cruise flight. During the descent, the left engine had no response to throttle input while the right engine was confirmed to still be operating.
“The Cockpit Voice Recorder (CVR) retained about 30 minutes 53 seconds of the flight and started recording at 1513:44hrs by which time the Captain and First Officer (F/O) were in a discussion of a non-normal condition regarding the correlation between the engine throttle setting and an engine power indication.”
“The flight however continued towards Lagos as the crew continuously discussed the problem with vague references to EPR and nonresponse from the throttle inputs, with the left engine operating at idle power or inoperative.”
“At 1531:12hrs, the crew confirmed that there was no throttle response on the left engine and subsequently the Captain took over control as Pilot Flying (PF) at 1531:27hrs. The flight was however continued towards Lagos with no declaration of any distress message. With the confirmation of throttle response on the right engine, the engine anti-ice, ignition and bleed-air were all switched off. At 1532:05hrs, the crew observed the loss of thrust in No.1 Engine of the aircraft.”
13. During the initial descent, the captain seemed satisfied that the right engine was operating normally. No distress call was made. However, the F/O did suggest switching from runway 18L to the much longer 18R which was requested and approved by ATC.
“With the confirmation of throttle response on the right engine, the engine anti-ice, ignition and bleed-air were all switched off. At 1534:33hrs the Captain confirmed that “okay this one is good for us so far”.
14. There were some discussions between the pilots about the profile to be flown and that was being flown during the descent. Initially it was decided “that they should start a gradual descent”. During the initial descent, the captain wanted a higher descent rate while the F/O preferred to remain on a higher profile. Later on, however, the F/O stated that the aircraft was high at which point it was decided to start extending flaps. At this point one engine was believed to be operating normally.
“During the initial descent, the Captain wanted the F/O who was then the Pilot Flying (PF) to increase the rate of descent but the F/O stated that he would prefer a gradual descent in order to have enough height over Lagos.”
“At the same time, the crew also carried out some of the pre-landing tasks that included the extension of slats at 1537:07hrs and the speed-brakes were deployed at 1537:10hrs. The First Officer indicated that they were slightly high and the Captain replied that he was correcting and then requested for flaps eleven. At 1537:53hrs the Captain further requested for flaps one-five (flaps fifteen)."
15. The report states that the engine-out profile was not flown, however, the report does not say what this profile is or provide a copy of the manufacturer’s engine-out profile. The aircraft appears to have ended up on a 3 to 1 profile but with high drag items deployed while still quite far from the airport. Subsequently, they descended below the 3 to 1 path with further deployment of high drag items. The gear was selected down at around 20 miles from the airport.
“At 1537:53hrs the Captain further requested for flaps one-five (flaps fifteen). At 1538:35hrs, both crew indicated that they were 21 miles on the localizer. At 1538:54hrs, there was EGPWS automated voice warning of “landing gear” which the Captain responded to at 1539:10hrs by requesting for the landing gear to be selected down.”
“1540:42hrs, he confirmed to the Captain that they were five thousand, fifteen miles, which the Captain acknowledged with an increase in the rate of descent.”
16. After increasing the drag significantly with gear and partial flap extension, there was a requirement to add thrust on the remaining engine. It was around this time that it was discovered that the second engine was not increasing power in response to throttle input, although it was still operating. An emergency was declared after this was discovered but no checklist was called for.
“According to the CVR transcript at 1541:46hrs the First Officer inquired if “both engines come up” and the Captain replied “negative” at 1541:48hrs. The two engines finally did not respond to throttle inputs as both engines failed to produce the commanded thrust.”
17. After the second engine malfunction, the captain asked initially for more flap, then decided to retract the gear and flaps. The timing of his calls for flap/gear retraction differ in two sections of the final report.
“At 1542:10hrs, DANACO 0992 radioed an emergency distress call indicating "dual engine failure . . . negative response from throttle."
“At 1542:35hrs the Captain requested for flaps twenty eight which the First Officer selected. This was after the crew had declared an Emergency of dual engine failure.”
“At 1542:35hrs, the flight crew lowered the flaps further and continued with the approach and discussed landing alternatively on runway 18L. At 1542:45hrs, the Captain reported the runway in sight and instructed the F/O to retract the flaps and four seconds later to retract the landing gears.”
“At 1543:30hrs there was an automated voice of “altitude” followed by the Captain’s indication of sighting the runway at 1543:45hrs. He then instructed the First Officer to select the flaps up at 1543:49hrs followed by another instruction to select the landing gears up at 1543:50hrs."
18. Both the engines on the accident aircraft exhibited damage patterns that were similar to other engines that had suffered from a lack of response to throttle input. This included the third engine on the aircraft that later on had to make an air return. However, in the report created by the powerplants group, there was no conclusion as to the timing of the damage which perhaps is the reason that the manifold damage is not mention as a probable cause but is instead only hinted at in the report.
“Both engines’ fuel system components exhibited the same types of damage which was consistent with others that suffered lack of response to the throttles.”
“The Fuel Manifold segment from Engine #1 of Pratt & Whitney JT8D-217C revealed, during examination using stereo microscope, that the fracture was consistent with overstress separations and bending load. According to the test report, it was asserted that there was no evidence that the fracture was pre-impact. However, on the air return aircraft, the fracture was at the same position.”
19. Sixteen months after the accident, the third engine that Dana Airlines had overhauled by Millenium had a malfunction that was similar to what was experienced on the accident aircraft. The aircraft was able to return for a landing and was not damaged. It was discovered that this third engine did not have the applicable SB performed on it and that faulty work had been performed on the fuel manifold assembly.
“….improper installation of the right hand fuel manifold inlet fairing. Installation of distorted manifolds and incorrect shimming of the manifold which are capable of aggravating the condition as stated in SB 6452. There was lack of engagement of the front and rear sections of the manifold fairings on the inboard side. The engine suffered thermal stress and fractured secondary manifold feeder line resulting in loss of power and failure to respond to throttle movement.”
20. While the two engines in the accident aircraft had experienced a sudden impact of a crash potentially causing further damage, the third engine which was on a different aircraft did not suffer through an accident, yet all three had similar damage patterns signifying that the damage to the engine fuel lines happened prior to impact. There were no other engine faults aside from the fuel manifold line problems making it likely that the improper maintenance done by Millenium was the reason for the dual engine failure and accident of Danaco 992.
“All engines had primary and secondary fuel manifold assemblies fractured, cracked, bent, twisted or pinched which led to fuel leaks, fuel discharge to bypass duct, loss of engine thrust and obvious failure of engine responding to throttle movement.”
“The engines teardown were successfully carried out without any core engine anomalies detected apart from the fuel manifold issues that would have made the aircraft mechanically unsafe. However, the observed damage to the engines was consistent with low-to no rotation speed at impact but no indications of core engine hardware pre- impact malfunction was revealed at the engines teardown.”
21. The engines on the accident aircraft were sent to Millenium who appear to have had custody and control of them. A teardown examination was done by representatives from several interested parties. The engines were found to not have any evidence of damage that would have caused a failure however, both engines had fuel manifolds exhibiting signs of damage similar to the aircraft that had to make the air return due to damaged fuel manifolds. Some of the components of the second engine that failed(engine #2) that were suspected of being installed improperly were not returned by Millenium for further examination(metallurgical test by the NTSB which revealed that the manifold fractures on the left engine were consistent with overstress separations and bending load).
“The right-hand primary and secondary manifold supply tubes were bent at the No. 5 fittings. Similar damage was noted on the left-hand primary and secondary manifold supply tube at the No. 6 fittings. Neither of these bends completely obstructed flow. The left hand primary manifold also had a circumferential crack just outboard of the fan duct pass through.”
“The engine teardown was performed at Global Engine Maintenance facility (formerly Millenium Engine Associates) in the USA. The organization is also responsible for securing and ensuring that all the parts examined are returned to the engine owners with the permission of the investigating body. However, certain components such as the right fuel manifold were not available for subsequent examination.”
"Examination and disassembly of the No. 1 engine did not identify any mechanical condition which would have prevented normal operation of the engine at the time of impact."
"The lack of fuel system components still attached to the engine prevented any detailed examination and overall assessment of the condition of the fuel system pre- and post-impact."
“During the engine teardown in the USA, the organization that performed the teardown examination was supposed to have shipped the engines back to the Dana Airlines in Lagos. However, the engines were shipped without the right engine fuel manifold assembly.”
“Fuel manifold segment test from #1 Engine was performed at the NTSB laboratory in the USA. The fuel manifold from Engine #2 was not provided by the operator who had custody of the accident engines.”
22. The AIB feels that the maintenance work done by Millenium on the three engines was improper. Millenium subsequently changed its name to Global Engine Maintenance.
“The work processes, ethics and culture in Global Engine Maintenance LLC formerly known as Millenium Engine Associates Inc. are subject of concern to Nigerian Civil Aviation Authority and AIB. This concern was as a result from the discovery made in the cause of investigation in the Air Return aircraft 5N-SAI, which shows the improper installation of the right hand fuel manifold inlet fairing. Installation of distorted manifolds and incorrect shimming of the manifold which are capable of aggravating the condition as stated in SB 6452. There was lack of engagement of the front and rear sections of the manifold fairings on the inboard side.”
Last edited by JammedStab; 13th Aug 2017 at 20:34.
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Thanks, I made some modifications to the main body of numbers 18 and 21. It took a lot of analysis to re-arrange the information put everything together in a way which finally seems to make a plausible scenario.
A few days ago, an Arik 737-800 declared a Mayday on final approach to Lagos when it lost an engine:
Nigeria: Arik Faces Maintenance Challenges Over Paucity of Funds - allAfrica.com
Probably all of those points made by JammedStab would apply to Arik today...
I watched and listened to an Arik 737 at Enugu about four months ago having to repeatedly shut down and restart its engines in an attempt to "clear" an unidentified fault. It got going eventually....
Nigeria: Arik Faces Maintenance Challenges Over Paucity of Funds - allAfrica.com
Probably all of those points made by JammedStab would apply to Arik today...
I watched and listened to an Arik 737 at Enugu about four months ago having to repeatedly shut down and restart its engines in an attempt to "clear" an unidentified fault. It got going eventually....
