What do the red radial lines on the face of an engine oil pressure gauge indicate?

The red radial lines on the face of an engine oil pressure gauge serve as indicators for minimum and/or maximum safe operating limits. These lines provide vital information to the pilot about the acceptable range of oil pressure for safe engine operation. When the oil pressure falls below the lower limit marked by the red radial line, it signifies a potentially dangerous condition that could lead to engine failure due to inadequate lubrication. Conversely, if the pressure exceeds the upper limit, it could indicate excessive pressure that might cause oil leaks or system failure.

In essence, the presence of these red markings allows pilots to quickly assess the oil pressure status at a glance, promoting immediate corrective action if the parameters are not within the safe range. This visual cue is crucial for maintaining engine health and safety during flight operations.