An instrument student is practicing an ILS approach. The approach chart indicates a published decision altitude (DA) of 250 feet AGL. The student's altimeter reads 1,250 feet MSL at DA. Assuming the airport elevation is 1,000 feet MSL, what is the required visual reference at DA for the student to continue the approach to a landing?
- AThe runway threshold, threshold markings, or threshold lights must be visible.
- BThe approach lights or runway environment must be distinctly visible.
- CAny portion of the approach lighting system is visible, and the aircraft is in a position to make a normal landing.
- DAt least 500 feet of the approach lighting system must be visible.
Show answer & explanationAnswer & explanation
Correct answer: B. The approach lights or runway environment must be distinctly visible.
According to 14 CFR 91.175, to descend below DA or MDA, a pilot must have the runway environment in sight and be in a position to make a normal landing. The runway environment includes the approach lighting system, threshold, threshold markings, threshold lights, runway or runway markings, runway lights, visual glideslope indicator, touchdown zone, or touchdown zone markings/lights.
Why the other options are wrong
- A. While these are part of the runway environment, the requirement is broader; it's *any* of the specified visual references, provided the aircraft is in a position to make a normal landing.
- C. This option is close but 'any portion of the approach lighting system' is too vague. The pilot must see the runway environment, and if only the approach lights are visible, they cannot descend below 100 feet above the touchdown zone elevation unless they can see the red terminating bars or red side row bars.
- D. There is no specific minimum footage requirement for the approach lighting system to be visible to descend below DA/MDA, other than the specific 100-foot rule if only the approach lights are visible and you can't see the red terminating bars or side row bars.
91.175 Visual Reference Requirements
To descend below the Decision Altitude (DA) or Minimum Descent Altitude (MDA) during an instrument approach, 14 CFR 91.175 requires the pilot to have the runway environment in sight and be in a position to make a normal landing. The 'runway environment' includes a list of specific visual references.
- Runway environment in sight.
- Aircraft in position for normal landing.
- Runway environment includes approach lights, threshold, runway, etc.
- Specific rules apply for descending below 100 feet AGL if only approach lights are visible.
Memory trick: See the Runway, Land it Right.