Definition
In instrument flight, a supporting power instrument is the cockpit instrument used to confirm and fine-tune the result of a power change after the primary power instrument has been set. During straight-and-level flight, the airspeed indicator typically serves as the supporting power instrument, verifying that the manifold pressure or RPM (the primary power instrument) is producing the intended performance.
Plain English
It is the second instrument the pilot looks at to check that a power setting is actually giving the speed or performance they wanted. The first instrument shows what power was set; the supporting one shows whether that power is doing its job.
Context Anchor
Seen in instrument flying when learning which instruments are primary and which are supporting during straight-and-level flight.
Derivation
‘Supporting’ comes from the Latin ‘supportare,’ meaning ‘to carry’ or ‘to bear up.’ In this context, the instrument supports the primary one by backing up its reading with confirming evidence — it does not lead, but it carries the check.
Why Pilots Care
Precise power management prevents unintended climbs, descents, or airspeed deviations when visual references are absent.
Intuition Check
Supporting does not mean unimportant here. It means the instrument is not the main reference for that part of the maneuver, but it helps confirm that the main reference is making sense. Power instrument does not mean an electrical instrument. It means an instrument used to judge engine power.
Example Sentence 1
After reducing manifold pressure to the cruise setting, the pilot glanced at the airspeed indicator as the supporting power instrument to confirm the airplane had settled at the planned cruise speed.
Example Sentence 2
In straight-and-level flight the airspeed indicator remained primary while the pilot used supporting power instruments to hold a constant RPM.