[Ref. Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B Page 5-2]
Steady flight, the sum of the 4 forces is always zero – not mean the 4 forces are equal.
No unbalanced forces in steady, straight flight based upon newton’s 3rd law.
Steady (unaccelerated) flight –The sum of all upward components of forces (not just lift) equals the sum of all downward components of forces (not just weight)The sum of all forward components of forces (not just thrust) equals the sum of all backward components of forces (not just drag)
1.sum of all upward components = downward
2. sum of all forward components = backward
Any time the flight path of the aircraft is not horizontal, lift, weight, thrust, and drag vectors must each be broken down
Concept of steady flight is suitable for various maneuvers (NOT limited to straight and level)