I was wondering what kind of low pressure indication causes abnormal variations in the RPM of a Lockheed L188 Electra. I was told one of the engines was presenting low pressure readings at certain rotations. Would that be low engine oil pressure? I have read the Electra manual and only saw indication of low pressure for either hydraulics or engine oil. The call of low pressure was originally made by the FE, which makes me think it should be something that would show somewhere in the flight station. Thanks
In this link the only relevant low pressure indications I found were of engine oil and of hydraulics. https://publicapps.caa.co.uk/docs/33/SRG_ACP_L188_REV2_ALL.PDF . Presumably everything should be there, although I was subsequently told that it could also refer to manifold pressure.
Here, https://www.spruemaster.com/blog/wp-content/gallery/manual/Lockheed%20L-188%20Electra%20-%20%20Electra%20Flight%20Control%20S%20ystem%20Part%201.pdf , on page 30, fig.24, there is a picture of the flight station . I had originally only seen the four lights indicating low engine oil pressure (top left corner, listed as part of the "Ess Ac Inst Bus"), but upon closer examination, I found other things related to pressure as well. Perhaps I was biased because the first documents I read only mentioned hydraulics and engine oil.
So I guess my question should be: what kind of low pressure is the cause of (or is caused by - the Captain was not very clear) abnormal RPM readings. Thanks a lot
Ps: I tried to upload the flight station image here, but didn't manage. It sad it was too big. My apologies.