Trent 700 step aside gearboxes

Date:         10 Jun 97 00:35:01 
From:         Exiled Expat <lutsch@emirates.net.ae>
Organization: Etisalat Emirates Internet Service
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The following is a Quote of an Airbus Industrie Operators information
telex sent 06 June 97
Extra information has been added for extra info to the unfamiliar.

"Subject: Information Regarding A330 Trent 700

Further to recent events regarding Rolls Royce Trent 700 powered A330
aircraft Airbus industrie have received many requests for detailed
information regarding both the cause and the progress of the
investigation.
The following is a brief summary of the events which led to Cathay
Pacific and Dragonair to suspend operation of their A330 aircraft.   A
review of the investigation and a desciption of the resultant
modification.

Summary of events:

On Saturday the 24th of May, Cathay Pacific Airways and Dragonair
suspended the operation of their A330-300 fleets.  The decision was
taken, by the airlines, further to an in flight engine shutdown caused
by the failure of a bearing in the step aside gearbox fitted to the
Rolls Royce (RR) Trent 700 engines.  The step aside gearbox is
manufactured by Hispano-Suiza.  ( This gearbox transmits and redirects
at an angle, rotation of a shaft coming out of the engine core to a
radial driveshaft which goes to the accesory gearbox.  This accessory
gearbox drives all of the engines supporting components like generators,
fuel pump, hydraulic pump, and air/oil seperator. )  This event was the
fourth in flight shutdown involving RR Trent 700 powered A330 aircraft.
 The first being recorded 11 Nov 96, thereafter 06 May 97, 09 May 97 and
22 May 97.
It should be noted that after the third event ETOPS operations on The RR
Trent Powered A330 Had been formaly suspended. ( ETOPS stands for
extended twin operations which is a program under which a twin engined
aircraft is allowed to fly further from a suitable landing site than was
previously allowed prior to 1985 if its systems and reliability can be
proven over a given time. )

Background information

There are a total of 57 A330 aircraft in service of which 21 are powered
by RR Trent 700 engines ( CPA 11 A/C, HDA 4 A/C and GIA 6 A/C ( Guaruda
) ).  As an exclusively engine related issue there was no implication
for A330 powred by P&W of GE engines, Nor any other Airbus aircraft
type.

Investigation

Investigations have revealed that, in each case, a failure of the
driving bevel ball bearing occurred.  This failure permitted axial
movement of the gear shaft resulting in loss of drive and a subsequent
loss of fuel supply leading to engine run down.  The in service and
laboratory findings confirmed that the bearing failures were the result
of insufficient lubrication.  This was further supported by the fact
that strip examination of Trent 800 Step aside gearboxes, on which a
more positive lubrication is supplied to this bearing, showed no signs
of this anomaly.
( The Trent 800 is a greater powered engine used on The Boeing 777 which
is very similar in design to the Trent 700 .  It should be noted that
the Trent 800 step aside gearbox has not been without its own problems
after a number of gearboxes developed cracks causing oil leaks.  It was
found that oil puddling inside the radial drive shaft was causing an
unbalanced condition which led to excessive shaft vibration.  This shaft
vibration caused cracking in both the step aside gearbox, the lower
bevel gearbox and excessive fetting wear on the radial driveshaft
shroud.  RR has now come out with a mod to drill holes in the shaft
circumference to allow the puddled oil to be centrifuged out of the
shaft eliminating the shaft oscilations.  Half of our engines have now
been modified and hopefully it will be the final fix, eliminating the
need to inspect the gearboxes on every intransit stop through our Base.)

Modification

RR and Hispano-Suiza developed a modification that ensures satisfactory
lubrication to the affected bearing.  The modification has been fully
tested and qualified.  A retrofit campaign for all RR Trent 700 Powered
A330 aircraft is well advanced and the first of the modified step aside
gear boxes have been subjected to high power engine runs and flight test
all of which have been sucessful.

The affected A330 aircraft are now returning to revenue service.

Issued by JP Grother
A330/A340 Program Director
Engineering and Technical Support
Customer Services Directorate
Airbus Industrie

End Quote

Just thought a few of you out there might like some accurate info on the
subject.
Exiled Expat