FAA Flight Instructor Airplane (FIA)Performance, Weight and BalanceMedium
A pilot computes a loaded airplane weight of 2,650 lb and a moment index of 82.0 (moment/1000). When plotted on the CG moment envelope graph, this point falls outside the aft boundary of the utility category envelope but inside the normal category envelope. What should the pilot conclude?
- AThe graph must be misread since weight and moment values cannot fall between two envelopes
- BThe aircraft is safe for utility category maneuvers since the weight is below max gross weight
- CThe aircraft cannot legally be flown until weight is added forward regardless of category
- DThe aircraft may be flown in the normal category, but utility category maneuvers such as spins are not authorized at this loading
Show answer & explanationAnswer & explanation
Correct answer: D. The aircraft may be flown in the normal category, but utility category maneuvers such as spins are not authorized at this loading
Many airplanes have separate normal and utility category envelopes on the same graph; a loading within the normal envelope but outside the (typically more restrictive, forward-CG-limited) utility envelope permits normal category flight only, prohibiting maneuvers such as spins that require the utility category limits.
Why the other options are wrong
- A. Points between envelopes are a normal and expected result of overlapping envelope graphs.
- B. Weight alone does not determine category eligibility; CG position relative to the specific envelope matters.
- C. The airplane can be flown normally since it is within the normal category envelope.
CG Moment Envelope Graph
A graph plotting weight versus moment (or moment index) showing the boundaries within which the CG must fall; some aircraft have separate envelopes for normal and utility categories.
- X-axis is typically moment or moment index; Y-axis is weight
- Loaded point must fall within the envelope for the intended category
- Utility category envelope is often narrower, restricting CG range for aerobatic maneuvers
Memory trick: Inside the box, you're good to go — outside means one category's a no.