I think we have a P3 leak here.  Possible pressure bleed leak, maybe a bad valve, number-two engine.  I'm losing some Nf speed and some Ng, sir.  T5 is coming up a little. Ten feet over the flight engineer's head, a spring had broken, opening a valve wider than it was supposed to be.  It released bleed air supposed to recirculate within the turboshaft engine.  That reduced combustion in the engine, and was manifested in reduced Nf or free-power turbine speed, also in Ng power from the gas-producer turbine, and finally the loss of air volume resulted in increased tailpipe temperature, called T5.  Johns and Willis could see all this from their instruments, but they really depended on Sergeant Zimmer to tell them what the problem was.  The engines belonged to him?