FAA Airline Transport Pilot (ATM)Aircraft Performance and Weight and BalanceHard
Per 14 CFR Part 25 certification standards, the net takeoff flight path for a two-engine airplane is derived from the gross takeoff flight path by applying what fixed gradient decrement to provide a margin for obstacle clearance?
- A0.8%
- B1.1%
- C0.9%
- D1.0%
Show answer & explanationAnswer & explanation
Correct answer: A. 0.8%
For certification purposes, the net takeoff flight path is the gross (demonstrated) flight path reduced by a fixed decrement: 0.8% for two-engine airplanes, 0.9% for three-engine airplanes, and 1.0% for four-engine airplanes. This margin accounts for variations in pilot technique and atmospheric conditions and is what must clear obstacles by a specified margin.
Why the other options are wrong
- B. 1.1% is not a certification decrement used in Part 25.
- C. 0.9% applies to three-engine airplanes, not twins.
- D. 1.0% applies to four-engine airplanes, not twins.
Net Takeoff Flight Path
The gross (demonstrated) climb flight path reduced by a fixed gradient decrement to build in a safety margin for obstacle clearance.
- Twin-engine: 0.8% decrement
- Three-engine: 0.9% decrement
- Four-engine: 1.0% decrement
- Net flight path must clear obstacles by 35 ft (or specified margin)
Memory trick: Two engines, 0.8 — count the engines then subtract a decimal less one.