Turbo Commander: Engine Start Deep Dive

#turboprop #turbocommander #aircraft #engines

So you are probably wondering why my finger is on the HP limiter switch during the start sequence.  This is something you will not find in the operating manual.  By bumping or holding the HP LIMITER switch in the TEST position we can reduce the fuel supply to the engine thus controlling temps that may be trending to the hot side.  This is very useful during a quick turn when the engine is close to the maximum start temperature of 300 Celsius.

It is not uncommon for an already warm engine to want to exceed max start temperatures, this presents as a normally moving ITT gauge needle that just wants to keep going up the scale. To control this type of start the HP limiter can be blipped or held to manually stop fuel from entering the burn cans and halting the temperature increase until the compressor can spool up enough to supply adequate air flow to keep combustion temperatures within limits.