Specific Excess Power

If all excess power is used for climbing (no acceleration), then rate of climb = Ps × g / V. If Ps = 100 ft/s at sea level, max climb rate ≈ 100 × 32.2 / 300 ≈ 10.7 ft/s (6,400 ft/min). At higher speeds, climb rate is lower for the same Ps.

Available thrust decreases with altitude (unless using high-altitude engines); drag decreases slightly (lower dynamic pressure). Typically, Ps decreases with increasing altitude above sea level. However, at high altitudes with low density, the relationship becomes complex; engines optimized for high altitude may show peak Ps at 30,000+ feet.

Yes. If drag exceeds thrust, Ps is negative, meaning the aircraft is losing energy. It must descend (converting potential energy to kinetic) or decelerate to sustain level flight. In combat, being in negative Ps is a disadvantage; the pilot must trade altitude for speed to avoid stall.

Pilots compare Ps with adversaries at each flight condition. Higher Ps means superior energy state. Tactics involve maneuvering to a regime where your Ps is high and the opponent's is low, then exploiting the advantage (climb, accelerate, or turn). Classic tactic: lure opponent into sustained turn (negative Ps) while you maintain positive Ps.