Define service ceiling and absolute ceiling.

• A. Service ceiling is the altitude where the climb rate falls to a defined minimum.
• B. Absolute ceiling is the highest altitude with zero climb.
• C. Service ceiling is the altitude where the climb rate falls to a defined minimum.
• D. Absolute ceiling is the maximum altitude with zero drag.

Answer: (C)

The idea here is understanding how high an aircraft can effectively climb. The service ceiling is the altitude at which the aircraft’s rate of climb has dropped to a defined minimum that's still usable for regular operations (think a small, practical climb rate like about 100 feet per minute). It marks a practical upper limit for normal climbing performance, beyond which climbing becomes inefficient.

The absolute ceiling is a step further: it’s the altitude at which the rate of climb is zero. Above this point you can no longer gain altitude, even though you might still be able to maintain flight if you’re already there. It’s not about having zero drag—drag is still present—but about having no excess power to produce a climb.

So the statement that service ceiling is the altitude where climb rate falls to a defined minimum is the correct way to define service ceiling. The notion that absolute ceiling equals the maximum altitude with zero drag is incorrect because drag never disappears in flight; the zero-climb condition occurs when thrust just balances drag, not when drag is zero.