A propeller blade angle control circuit , comprising: a propeller pitch change mechanism ; an oil cooling line ; a fixed-displacement pump located upstream of the propeller pitch change mechanism and adapted to provide a supply of oil from an engine oil return system to the propeller pitch change mechanism ; and a valve (30; 130) disposed between the pump and the propeller pitch change mechanism , the valve (30; 130) having a valve body (31; 131) with a cavity (35; 135) therein, the valve body (31; 131) including an inlet port (32; 132) fluidly communicating with the pump , an outlet port (33; 133B) configured for fluid communication with the engine oil return system via the oil cooling line , and a single pitch port (34; 134) fluidly communicating with the propeller pitch change mechanism , the valve (30; 130) including a spool (36; 136) within the cavity (35; 135) displaceable between a first position and a second position within the valve body (31; 131), wherein in the first position, the spool (36; 136) permits communication through the outlet port (33; 133B) to the oil cooling line , in the second position the spool (36; 136) blocks the outlet port (33; 133B) to permit oil to flow through the single pitch port (34; 134) to the propeller pitch change mechanism , the spool (36; 136) is in the first position during steady-state operation of the propeller pitch change mechanism , the spool (36; 136) is in the second position during transient operation of the propeller pitch change mechanism , and the spool (36; 136) is displaceable within the cavity (35; 135) to always leave the single pitch port at least partially unblocked and always direct oil toward the propeller pitch change mechanism . a propeller pitch change mechanism ; an oil cooling line ; a fixed-displacement pump located upstream of the propeller pitch change mechanism and adapted to provide a supply of oil from an engine oil return system to the propeller pitch change mechanism ; and a valve (30; 130) disposed between the pump and the propeller pitch change mechanism , the valve (30; 130) having a valve body (31; 131) with a cavity (35; 135) therein, the valve body (31; 131) including an inlet port (32; 132) fluidly communicating with the pump , an outlet port (33; 133B) configured for fluid communication with the engine oil return system via the oil cooling line , and a single pitch port (34; 134) fluidly communicating with the propeller pitch change mechanism , the valve (30; 130) including a spool (36; 136) within the cavity (35; 135) displaceable between a first position and a second position within the valve body (31; 131), wherein in the first position, the spool (36; 136) permits communication through the outlet port (33; 133B) to the oil cooling line , in the second position the spool (36; 136) blocks the outlet port (33; 133B) to permit oil to flow through the single pitch port (34; 134) to the propeller pitch change mechanism , the spool (36; 136) is in the first position during steady-state operation of the propeller pitch change mechanism , the spool (36; 136) is in the second position during transient operation of the propeller pitch change mechanism , and the spool (36; 136) is displaceable within the cavity (35; 135) to always leave the single pitch port at least partially unblocked and always direct oil toward the propeller pitch change mechanism . <EOS>