Even though the ILS is still the gold standard for instrument approaches, it has an Achilles heel that catches even the professionals off guard. Don’t let it happen to you.
Handling ILS anomalies
Our CRJ-200 was sliding down through an overcast layer, following the glideslope to Runway 28 at Chicago OHare. Everything was normal, just like it always is. My airline job means I make this approach a couple of times a week.
Key Takeaways:
- ILS glideslope signals are susceptible to sudden, severe fluctuations caused by ground interference (e.g., vehicles in critical areas), posing a risk to coupled approaches and potentially leading to control issues.
- ATC protection of ILS critical areas is limited to specific low-visibility conditions and aircraft position, leaving many situations where ground traffic can cause interference, especially at uncontrolled airports or when the tower is closed.
- Pilots must be prepared for glideslope fluctuations by being ready to disengage autopilots, maintaining manual control (e.g., using a known vertical speed), and considering a localizer-only approach or missed approach if signal integrity is compromised.
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