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EWCG formula for nosewheel airplane

Aviation Mechanic General (AMG) practice question 25 of 25 on Weight and Balance. ACS element AM.I.C.R1 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA nosewheel airplane has its datum forward of the main wheels. The main-wheel weighing points are 100 inches aft of the datum, the nosewheel net weight is 300 lb, the distance between the main wheels and the nosewheel is 80 inches, and the total net weight is 2,400 lb. Where is the CG?

  1. A110 inches aft of the datum
  2. B10 inches aft of the datum
  3. C90 inches aft of the datum
Show the answer and explanation

Correct answer: C. 90 inches aft of the datum

  • A — incorrect Adding the nosewheel moment term instead of subtracting it is the formula for a datum aft of the main wheels; with the datum forward, the term is subtracted.
  • B — incorrect 10 inches is only the nosewheel correction (F x L / W); it must be subtracted from the 100-inch main-wheel distance D.
  • C — correct For a nosewheel airplane with the datum forward of the main wheels, CG = D - (F x L / W) = 100 - (300 x 80 / 2,400) = 100 - 10 = 90 inches aft of the datum.

BACKGROUND

The EWCG can be calculated quickly with one of four formulas, depending on gear type and datum location. Each formula first finds the moment of the nosewheel (F x L) or tail wheel (R x L), divides it by the total weight W, and then adds that result to or subtracts it from the distance D between the main wheels and the datum. For a nosewheel airplane with the datum forward of the main wheels, CG = D - (F x L / W). In the handbook's example with D of 128 inches, F of 340 lb, L of 78 inches, and W of 2,006 lb, the CG works out to 114.8 inches aft of the datum, 13.2 inches forward of the main wheels.

STUDY TIP

For a nosewheel airplane the CG is always forward of the main wheels, so with the datum ahead of the mains the correction must reduce D.

KEY POINTS

  • Nosewheel, datum forward of mains: CG = D - (F x L / W).
  • Nosewheel moment 300 x 80 / 2,400 = 10 inches.
  • CG = 100 - 10 = 90 inches aft of the datum.

SOURCES

  • FAA-H-8083-30B ch06 "EWCG Formulas"
  • FAA-H-8083-30B ch06 "Datum Forward of the Airplane - Nosewheel Landing Gear"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.