XMSN coupled generators
S-70 AC Gen Drop Off Point
InTheWeeds,
The 67% value that I quoted arose from a discussion many moons ago re a non-SA accident wherein the test instrumentation dropped off due to this issue during the event.
At the time our electrical power guys gave us an analytical number which I recalled as 67%.
Turns out a test was done later on, with the following result:
Several years ago we performed a UH-60L experiment on the ground with full electrical load (including blade de-ice dummy load) with the WOW switches wedged to the flight mode. Bringing PCL’s back slowly, we demonstrated that generators remained on line below 70% Nr. At about 68%Nr the #1 and #2 converter circuit breakers popped causing loss of VIDS displays.
Looks like the Army folks down at Ft Rucker may be putting out some bad info. ( And I was wrong in thinking it was the GCU undervoltage rather than the converters which provided the drop off ).
In any case, one would not want the electrical system protection knocking off the AC power source in flight at Nr numbers in the 80's.
Thanks,
John Dixson
The 67% value that I quoted arose from a discussion many moons ago re a non-SA accident wherein the test instrumentation dropped off due to this issue during the event.
At the time our electrical power guys gave us an analytical number which I recalled as 67%.
Turns out a test was done later on, with the following result:
Several years ago we performed a UH-60L experiment on the ground with full electrical load (including blade de-ice dummy load) with the WOW switches wedged to the flight mode. Bringing PCL’s back slowly, we demonstrated that generators remained on line below 70% Nr. At about 68%Nr the #1 and #2 converter circuit breakers popped causing loss of VIDS displays.
Looks like the Army folks down at Ft Rucker may be putting out some bad info. ( And I was wrong in thinking it was the GCU undervoltage rather than the converters which provided the drop off ).
In any case, one would not want the electrical system protection knocking off the AC power source in flight at Nr numbers in the 80's.
Thanks,
John Dixson
Join Date: Nov 2010
Location: Canada
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214ST
214ST has two C-box mounted DC Generators. The C-box is a separate Bell component from the GE CT7 Engines. (Same engine design as Black Hawk)
The engines have separate electric starters.
The engines have separate electric starters.
