Danger Below MDA?

Recently, an airline began to receive notices that crews flying the RNAV (GPS) RWY 36 approach into Birmingham, Alabama (BHM) were receiving GPWS alerts while descending from the MDA to the runway. Since it wasnt an isolated incident, the airline suspected that the approach was flawed and notified the FAA, who flight checked the approach. The results of that inspection are educational to instrument-flying pilots at all levels.

Editorial Staff

Friday, August 01, 2014 at 12:00 AM ET

Verified

Key Takeaways:

Vertical Descent Angles (VDAs) on non-precision approaches are advisory and intended for stabilized descents *to* the MDA, not continuously *below* it.
Unlike precision approaches, VDAs offer no guaranteed obstacle protection below the MDA, making continuous descent using them unsafe and prone to GPWS alerts or Controlled Flight Into Terrain (CFIT).
Pilots are ultimately responsible for visual obstacle avoidance below the MDA, as charted clues like VDPs and VGSIs provide limited or ambiguous information regarding the obstacle environment.

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Recently, an airline began to receive notices that crews flying the RNAV (GPS) RWY 36 approach into Birmingham, Alabama (BHM) were receiving GPWS alerts while descending from the MDA to the runway. Since it wasn’t an isolated incident, the airline suspected that the approach was flawed and notified the FAA, who flight checked the approach. The results of that inspection are educational to instrument-flying pilots at all levels.