JAL B747 jumbo in sky for 7 months with engines on wrong side
Thread Starter
Join Date: Apr 2004
Location: The Attic
Posts: 228
Likes: 0
Received 0 Likes
on
0 Posts
JAL B747 jumbo in sky for 7 months with engines on wrong side
Wednesday, December 21, 2005 at 18:37 EST
TOKYO — Japan Airlines had been flying a Boeing jumbo jet for seven months without realizing the plane's left and right outer engines had been placed on the wrong sides during maintenance in Singapore in February, airline officials admitted Wednesday.
Some components of the engines are required to be inspected once every 650 flights, but as a result of the mistake, one of the engines completed about 850 flights without being examined.
The officials said there were no safety problems but the Land, Infrastructure and Transport Ministry instructed the airline to take measures to prevent any recurrence.
In February, JAL commissioned ST Aviation Services Co Pte Ltd in Singapore to conduct maintenance work on the four-engine Boeing 747. The plane resumed service after the overhaul was completed in April.
It was not until a regular maintenance checkup in November that the engines were discovered to have been attached wrongly.
Reversing the engine locations results in air flow toward the fuselage instead of away from it during reverse thrust. However, it does not create any difference during normal thrust and thus poses no safety problems during flights, the officials said.
They said JAL will revise in-house procedures to ensure that inspections on the planes are conducted after outsourced maintenance work. The current policy only calls for checking documents after the completion of maintenance work.
TOKYO — Japan Airlines had been flying a Boeing jumbo jet for seven months without realizing the plane's left and right outer engines had been placed on the wrong sides during maintenance in Singapore in February, airline officials admitted Wednesday.
Some components of the engines are required to be inspected once every 650 flights, but as a result of the mistake, one of the engines completed about 850 flights without being examined.
The officials said there were no safety problems but the Land, Infrastructure and Transport Ministry instructed the airline to take measures to prevent any recurrence.
In February, JAL commissioned ST Aviation Services Co Pte Ltd in Singapore to conduct maintenance work on the four-engine Boeing 747. The plane resumed service after the overhaul was completed in April.
It was not until a regular maintenance checkup in November that the engines were discovered to have been attached wrongly.
Reversing the engine locations results in air flow toward the fuselage instead of away from it during reverse thrust. However, it does not create any difference during normal thrust and thus poses no safety problems during flights, the officials said.
They said JAL will revise in-house procedures to ensure that inspections on the planes are conducted after outsourced maintenance work. The current policy only calls for checking documents after the completion of maintenance work.
A pretty silly mistake when you look at it, but the bit I don't understand is where the JAL official explains that the reverse thrust is normally directed away from the fuselage. Does that mean that somehow the flaps that reverse the bypass airflow in the engine through the sliding cascade on the 747's engines can be enabled/disabled independently on the left and right sides of the engine when in maintenance to improve pax comfort?
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
Not for pax comfort, but to minimize reingestion of exhaust into the engine inlet -
It's usually more an issue on the inboards, preventing cross-ingestion into the outboards.
As quoted, it's kind of a non-event, if there have been no operational problems.
It's usually more an issue on the inboards, preventing cross-ingestion into the outboards.
As quoted, it's kind of a non-event, if there have been no operational problems.
Join Date: Jul 2005
Location: Here and there....currently here.
Posts: 217
Likes: 0
Received 7 Likes
on
3 Posts
Slightly misleading really, an engine can be fitted in any position as long as it is dressed for that position. The cascade vanes are the bits that are in the wrong positions as they are the bits that direct the airflow in the correct direction when the reverser is operating, usually forward and slightly outboard in the case of 747s (as far as I can remember).
Join Date: Jul 2005
Location: Here and there....currently here.
Posts: 217
Likes: 0
Received 7 Likes
on
3 Posts
Having reread this now, I think what has happened is that the engines were removed for the maintenance check and then put back on in the wrong position, ie No1 came off posn 1 and back on No4 posn. This could have gone undetected for quite a while and was probably only found due to the low hours inspection cycle, after all its not everyday we go checking engine serial numbers.
Join Date: Mar 2001
Location: u.k
Age: 62
Posts: 82
Likes: 0
Received 0 Likes
on
0 Posts
I cant quite get to grips with why they are talking about reversers. The cascade vanes are fitted in the C ducts and during an engine change the C ducts remain attached to the pylon therefore fitting the wrong engine would'nt have any effect on reverser operation.
Join Date: Dec 2000
Location: Hilversum, the netherlands
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
Reversers
Red5 wrote:
I cant quite get to grips with why they are talking about reversers. The cascade vanes are fitted in the C ducts and during an engine change the C ducts remain attached to the pylon therefore fitting the wrong engine would'nt have any effect on reverser operation.
Must be a 747-200, with JT-9 engines in this topic.
The P&W JT-9 reverser comes with the engine itself.
Ballpoint.
I cant quite get to grips with why they are talking about reversers. The cascade vanes are fitted in the C ducts and during an engine change the C ducts remain attached to the pylon therefore fitting the wrong engine would'nt have any effect on reverser operation.
Must be a 747-200, with JT-9 engines in this topic.
The P&W JT-9 reverser comes with the engine itself.
Ballpoint.
Join Date: Mar 2003
Location: Between land masses
Posts: 159
Likes: 0
Received 0 Likes
on
0 Posts
during maintenance in Singapore
Hang the offenders, I say!
Join Date: May 2003
Location: Beijing
Posts: 228
Likes: 0
Received 0 Likes
on
0 Posts
Foreign Worker
Read the original article again.
Which part of "ST Aviation Services Co Pte Ltd" do you not understand?
Try to find if Singapore Airlines is their customer in this link:
http://www.staero.aero/customers.html[
As JAL don`t have their own maintenance base in Singapore, it would appear that the work was outsourced to that island`s national airline maintenance company.
Which part of "ST Aviation Services Co Pte Ltd" do you not understand?
Try to find if Singapore Airlines is their customer in this link:
http://www.staero.aero/customers.html[
Join Date: Oct 2003
Location: Canberra Australia
Posts: 1,300
Likes: 0
Received 0 Likes
on
0 Posts
Whils we are talking engines do any of you engineers know if there are any twin spool engines made having contra rotating spools.? If not why not?
And how is the end thrust taken out of the spool bearings?
And how is the end thrust taken out of the spool bearings?
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
No commercial counter-rotating engines in the field yet, but there have been a few in the military world.
Lycoming's T53-1 had counter-rotating HP & LP turbines. It took advantage of the gas swirl leaving the HP stage to drive the LP stage, eliminating the need for a nozzle stator between the two.
This is the primary attraction of a counterrotating system - it saves weight & cost, with improved performance too.
I'm not really sure why the later T53 abandoned it, but I suspect there was a differential bearing in the shafting that Lycoming didn't have the requisite technology to be successful. When the inner race (ring) turns at xx000 rpm one way and the outer race yy000 rpm the other way, it's a real challenge.
In the early 90s some prototype military engines were using counterrotation with good success, and I worked on a NASA proposal for such an engine. I suspect it won't be long before we see them on airliners.
Whether counterrotating or not, the end thrust of each rotor is reduced by a system of air pressure chambers ("balance pistons") and the residual load taken out by a conventional ball bearing. It's desirable to keep some end load on the ball bearing to keep it from chattering, but by reducing the peak load, the ball bearing can be made lighter.
Lycoming's T53-1 had counter-rotating HP & LP turbines. It took advantage of the gas swirl leaving the HP stage to drive the LP stage, eliminating the need for a nozzle stator between the two.
This is the primary attraction of a counterrotating system - it saves weight & cost, with improved performance too.
I'm not really sure why the later T53 abandoned it, but I suspect there was a differential bearing in the shafting that Lycoming didn't have the requisite technology to be successful. When the inner race (ring) turns at xx000 rpm one way and the outer race yy000 rpm the other way, it's a real challenge.
In the early 90s some prototype military engines were using counterrotation with good success, and I worked on a NASA proposal for such an engine. I suspect it won't be long before we see them on airliners.
Whether counterrotating or not, the end thrust of each rotor is reduced by a system of air pressure chambers ("balance pistons") and the residual load taken out by a conventional ball bearing. It's desirable to keep some end load on the ball bearing to keep it from chattering, but by reducing the peak load, the ball bearing can be made lighter.
Milt,
The Harrier engine (RR Pegasus) has contra rotating spools. The early engines did not - but flight test found that the gyroscopic effects were unacceptable, I think when using high rates of yaw in the hover. If John Farley gets to this thread he will doubtless provide much more detail.
The Harrier engine (RR Pegasus) has contra rotating spools. The early engines did not - but flight test found that the gyroscopic effects were unacceptable, I think when using high rates of yaw in the hover. If John Farley gets to this thread he will doubtless provide much more detail.
Many years ago in my company we had a rogue L-1011 which occasionally had directional control problems on landing. After many write-ups it was eventually discovered that the No 2 Eng had the wrong part number reverser cascade vanes.
The normal configuration was for the No 1 and No 3 wing engines cascade vanes to be asymmetric handed (but mirror image) while the No 2 centre engine reverser cascade vanes were symmetric.
However the incident aircraft had a wing engine configuration fitted to the centre position but with the wing cascade vane part numbers incorrectly marked as centre vanes.
Now that took a little forensic science!
The normal configuration was for the No 1 and No 3 wing engines cascade vanes to be asymmetric handed (but mirror image) while the No 2 centre engine reverser cascade vanes were symmetric.
However the incident aircraft had a wing engine configuration fitted to the centre position but with the wing cascade vane part numbers incorrectly marked as centre vanes.
Now that took a little forensic science!
Join Date: Jan 2006
Location: Georgia, USA
Posts: 454
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by FlexibleResponse
Many years ago in my company we had a rogue L-1011 which occasionally had directional control problems on landing. After many write-ups it was eventually discovered that the No 2 Eng had the wrong part number reverser cascade vanes.
The normal configuration was for the No 1 and No 3 wing engines cascade vanes to be asymmetric handed (but mirror image) while the No 2 centre engine reverser cascade vanes were symmetric.
However the incident aircraft had a wing engine configuration fitted to the centre position but with the wing cascade vane part numbers incorrectly marked as centre vanes.
Now that took a little forensic science!
The normal configuration was for the No 1 and No 3 wing engines cascade vanes to be asymmetric handed (but mirror image) while the No 2 centre engine reverser cascade vanes were symmetric.
However the incident aircraft had a wing engine configuration fitted to the centre position but with the wing cascade vane part numbers incorrectly marked as centre vanes.
Now that took a little forensic science!
Join Date: Jul 2000
Location: Smogsville
Posts: 1,424
Likes: 0
Received 0 Likes
on
0 Posts
Trent 900 on the A380 uses contra-rotating spools.
For the first time in a Rolls-Royce civil engine programme, the Trent 900 will include a contra-rotating high pressure compressor system. The feature, which is used in some modern combat engine programmes, straightens the airflow through the engine's core, producing significant efficiency gains.
http://www.rolls-royce.com/media/showPR.jsp?PR_ID=1379
For the first time in a Rolls-Royce civil engine programme, the Trent 900 will include a contra-rotating high pressure compressor system. The feature, which is used in some modern combat engine programmes, straightens the airflow through the engine's core, producing significant efficiency gains.
http://www.rolls-royce.com/media/showPR.jsp?PR_ID=1379
