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ROTAX MANDATORY SERVICE BULLETINS
SB-912-032 (912A Series) and SB-912-032UL
"REPLACEMENT
OF OIL PUMP ASSY OR OIL PUMP SHAFT ASSY
The following MANDATORY service bulletins
required by Rotax to be incorporated at "at the next 100 hourly
inspection" but "at the latest by 1 Feb 2002" have been received
from Rotax. They affect certificated and Ultralight 912 Engines
and can be viewed by clicking the following links. These also give
serial numbers of engines affected.
SB-912-032 (912A Series)
SB-912-032UL (912UL Series)
To all Rotax 912 owners: Oil Pump Drive Pin
Following is the text of correspondence
forwarded to the AUF some time ago by Mr Carl Nilsson from
Tasmania.
Mr Nilsson's Correspondence:
In May 1999 my Skyfox CA22 reg. 55-0688
suffered an Rotax 912A engine failure and consequent forced
landing with no injuries, but some aircraft damage. This was
reported to the AUF and a brief summary of the accident appeared
on p 44 of the July 99 AU. What was noteworthy was that the
engine, No. 4076033 had only 26 hours since major overhaul. After
starting to lose power, the pilot continued to run the engine
until it seized. In fact, the crankshaft was destroyed and the
engine was a write-off. The cause was failure of the oil pump,
specifically the shearing of the dowel tube follower that drives
the oil pump. When this happened, the oil pressure would have been
lost and total engine failure followed.
Now, the message of this report is firstly, if
you are running an older Rotax 912 of serial number between
3792944 and 4076068, you should read the following story and check
that oil pump drive pin (follower). I purchased 55-0688 from **
Aviation in late 1998 with the engine having about 2140 hrs TTIS
and running well enough, but clearly needing an overhaul in the
near future. I flew the aircraft to Victoria with no trouble and
subsequently arranged an overhaul with a very competent Level 2
engineer.
The history of the engine was not fully
documented in the log book. It had been maintained for at least
the latter part of its life by a GA service organisation (Flinders
Aviation) and at some stage it had had a top end overhaul,
possibly when it was installed in 55-0688 with 935 hrs TTIS.
Someone had also honed the cylinders - a common practice with GA
engines, but a real no-no with the Rotax 912, which has Nikasil
coated cylinders. These things were apparent to the overhauling
AUF engineer. Now, owners of older 912's may note that certain
work had to be completed at 600 hrs to extend the TBO to 1000 hrs.
Rotax Technical Bulletin (TB) 912-05R2 refers for all 912A's
(Certificated) and earlier than N. 4076192 (and
Service Information 27 UL 94-E for non-certificated engines
which in return refers back to the bulletin for the certificated
engines). This is an important TB and central to the failure of
engine N. 4076033. (Downloadable from the links above in this HTML
version or available from the table from where you obtained this.
Note that they are large downloads of about 750KB).
Page 5 of this TB details oil pump amendment
nos. 17, 22 and 32-17. These say, essentially, inspect the oil
pump components for wear and, if necessary, renew. There is also a
Note, which says that after engine N. 3792944, the oil pump
capacity was increased by a change of components. It also says,
that after N. 4076068, the hollow drive pin was changed to a solid
notched pin. Thus, engines between N.3792944 and N. 4076068 were
delivered with larger oil pumps, but the original hollow drive
pin. With the wisdom of hindsight, a prudent reading of this
suggests that it would be a good idea for engines within this
range to have the hollow drive pin replaced with the later solid
one, however Rotax does not explicitly direct that this be done.
All they say is: "At a renewal of components change oil pump to
the version with the 16 mm long rotors" - ie. larger capacity. I
can also say that Bert Flood, for example, routinely changes to
the solid drive pin when he is doing a 1000 hrly on a 912.
Now the plot thickens a little: a perusal of
the log book for this engine shows an entry "TB 912-05 complied
with". A normal reading would suggest to an owner (as it did to
me) that these things had been taken care off. It might be, that
at the 600 hr inspection, no oil pump components were changed -
or, it might be that they were at some time, but (clearly) not the
oil pump drive pin. When we overhauled the engine in early 1999,
the hollow pin was looked at, deemed OK and left in situ. When it
failed, this pin had presumably driven the oil pump for about 2200
hrs. After this accident, other owners of 912's at the local
airfield inspected their oil pumps. One Gazelle, which had been
maintained as a GA aircraft, had the usual log book entry "TB
912-05 complied with", but still had the old hollow pin. Another
earlier engine, N. 4005313, which had previously had a 1000 hrly
by Bert Flood, had the solid drive pin as he had stated it should.
So the lesson is - if you have a Rotax 912
earlier than N. 4076068, check the oil pump drive pin and, if it's
hollow, replace it
Carl Nilsson AUF 009966.
Tech Manager Comments. A sad occurrence
stressing the need for vigilance in airworthiness management. The
information that would have prevented the occurrence had been
published as far back as 1995/96 in Rotax Service Data. However,
one having been caught out suggests that it should be brought to
the attention of all members.
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