JAL B747 jumbo in sky for 7 months with engines on wrong side

[A-FLOOR]

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.http://www.crisscross.com/jp/news/359247

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? :confused:

[barit1]

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.

[Tom Sawyer]

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).

[greciangod]

Surely the point here is that a component or components have overrun an inspection by 200 flights.

[Tom Sawyer]

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.

[FBW390]

Anyway such a mistake is unacceptable from an approved maintenance station. And JAL should check really more!:\

[Sleep Deprivation Chamber]

How did they manage to fit the engines on the wrong "side"??

You would think four engines on the "inside" would have been fairly obvious after startup :}

[red 5]

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.

[Few Cloudy]

Do JAL do heavy Maintenance in Singapore, or is it done by Singapore Airlines?

[ballpoint]

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.

[yachtno1]

Who are "We" Tom Sawyer? :confused: Checking Pt/No Ser/No before fitting is a very elemental thing!

[Foreign Worker]

during maintenance in Singapore 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.

Hang the offenders, I say!

[Thermal Image]

Foreign Worker

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.

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[

[Milt]

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?

[barit1]

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.

[kenparry]

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.

[Cardinal]

The PT6 has counter-rotating spools! Not perhaps the GE90-esque powerplant you were thinking of, but commercial, nonetheless.

[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!

[glhcarl]

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!
Actually this happened quite often. The first sign of something being wrong would be delamination, followed by desintegration, of the lower trailing edge horiziontal stabilizer panels, the panels just forward of the elevator. I remember Delta having this problem once in Shannon. They requested permision to replace the fiberglass panels with sheet aluminum on a temporary basis until they could order new panels and get the the plane to Atlanta for repair. About a week later they asked if they could again use aluminum sheet because ones they installed a week earlier were cracked. They had forgot to correct the cascades.

[SMOC]

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