Oil indication vertical red Lines
As
earlier described on the page, here a summary of this indicating problem which
is not “in the books” but a Boeing identified “system glitch” with a
recommendation.
It
concerns vertical red line indications on the OIL TEMP, together with an OIL
PRESS indication and the engine shut down.
These indications appear not to be parameter exceedances, as in that case the white digital readout box would be red as an exceedance memory box with the engine not operating. It also is close to impossible for both oil exceedance indications to be present at the same time as a high oil temp would result in a low press and vv. When either of these exceedances occur on an operating engine, the oil TEMP or PRESS is higher than the redline limit and the digital readout and the box around the digital readout turn red.
These indications appear not to be parameter exceedances, as in that case the white digital readout box would be red as an exceedance memory box with the engine not operating. It also is close to impossible for both oil exceedance indications to be present at the same time as a high oil temp would result in a low press and vv. When either of these exceedances occur on an operating engine, the oil TEMP or PRESS is higher than the redline limit and the digital readout and the box around the digital readout turn red.
Obviously
Boeing confirmed that these indications together are caused when the DEU loses
engine limit data input from the EEC. Normally the DEU responses on that EEC
data to identify an overtemp or overpress within the engine’s oil system.
Boeing suggests to reset the data received from the DEU to the EEC by means of
selecting the START SWITCH to CONT for >10 seconds before starting the
engine, that is when its respective AC XFR bus 1 or 2 is energized. This will
allow a correct engine limit data information flow between the EEC and DEU
where after the indications should return to normal.
Thanks
to the contributors of info on this subject, special thanks to Jorge and Craig
of whom I’ve used their valuable inputs.
