Question

Which of the following statements about absolute ceiling and service ceiling for a piston–propeller aircraft is/are correct?

• A. The altitude corresponding to absolute ceiling is higher than that for service ceiling
• B. At the absolute ceiling, the power required for cruise equals the maximum power available
• C. The altitude corresponding to absolute ceiling is lower than that for service ceiling
• D. At the service ceiling, the maximum rate of climb is 50 ft/min

Hint:

Remember: service ceiling (piston) \(\to\) \( \dot h_{\max}=100\ \mathrm{ft/min}\); absolute ceiling \(\to\) \( \dot h_{\max}=0\) and \(P_{\text{req}}=P_{\text{avail}}\).

Answer 1

The Correct Option is A, B

Step 1: Definitions (piston–prop aircraft).
Absolute ceiling: altitude where excess power \(P_{\text{ex}}=P_{\text{avail}}-P_{\text{req}}\) becomes zero. Hence \(P_{\text{avail}}=P_{\text{req}}\) and the maximum rate of climb \(\dot h_{\max}=P_{\text{ex}}/W=0\).
Service ceiling: altitude where the maximum rate of climb reduces to a small prescribed value; for piston aircraft this is \(\dot h_{\max}=100\ \text{ft/min}\) (not \(50\ \text{ft/min}\); the latter is sometimes used for certain jets). 

Step 2: Evaluate the options.
(A) Absolute ceiling corresponds to a higher altitude than service ceiling. \(\Rightarrow\) True.
(B) At absolute ceiling, \(P_{\text{req}}=P_{\text{avail}}\) (no excess power). \(\Rightarrow\) True.
(C) Says absolute ceiling is lower; contradicts (A). \(\Rightarrow\) False.
(D) States \(50\ \text{ft/min}\) for service ceiling; for piston props it is \(100\ \text{ft/min}\). \(\Rightarrow\) False.
\[ \boxed{\text{Correct: (A), (B).}} \]