A pilot is comparing the effect of wind on landing distance. Why do AFM performance charts typically apply only a 50% credit for headwind but a full (or greater) penalty for tailwind components?
- ABecause headwinds are always more accurately measured than tailwinds
- BBecause regulations require charts to ignore headwind effects entirely
- CBecause tailwind components increase lift, requiring longer distances only for that reason
- DBecause the relationship between wind and landing distance is conservative and nonlinear, so tailwinds are penalized more heavily than headwinds are credited to ensure a safety margin
Show answer & explanationAnswer & explanation
Correct answer: D. Because the relationship between wind and landing distance is conservative and nonlinear, so tailwinds are penalized more heavily than headwinds are credited to ensure a safety margin
To provide a conservative safety margin, AFM performance data typically credit only 50% of the reported headwind component but apply the full effect (or more) of any tailwind component, since a small tailwind produces a proportionally larger increase in landing distance than a headwind produces in decrease.
Why the other options are wrong
- A. Measurement accuracy is not the reason for the conservative wind credit rule.
- B. Headwind effects are used, just at reduced (50%) credit, not ignored.
- C. Tailwind does not increase aerodynamic lift; it increases ground speed at touchdown, requiring more distance.
Wind Component Crediting
Performance charts apply only 50% credit for headwind benefit but full or greater penalty for tailwind, since tailwind increases required distance disproportionately more due to higher touchdown ground speed.
- 50% headwind credit is standard for conservatism
- Tailwind penalty is often 100-150% of the actual component
- Reflects nonlinear relationship between ground speed and stopping distance
Memory trick: 'Half credit for help, full blame for hurt'