Derived Decision Altitude (Height) – DDA (H):

When a go-around is initiated at the Minimum Descent Altitude (MDA) while descending, the aircraft might momentarily descend below the MDA during the missed approach maneuver, which is not permissible.

To prevent this, operators must add a margin of at least 50 feet to the MDA and designate it as the Derived Decision Altitude (DDA) or Height (DDH).

• This ensures that initiating a missed approach at the DDA (H) allows the aircraft to remain above the MDA at all times, maintaining safety and regulatory compliance.
• The DDA (H) provides a practical buffer, ensuring adherence to altitude restrictions during critical phases of flight.