When a warning light flickers on in the cockpit instrument panel, what’s your first instinct?

Some pilots tend to disregard warning lights – but that mindset is problematic, according to Dave Brown, an ASPEQ Flight Examiner and A-cat instructor.

Dave says a student ignored an alternator warning light because, they said, “It happens all the time”.

“There was a fault with the left engine alternator that was assumed to be an indication fault,” Dave explains.

“The ‘L ALTN FAIL’ caution kept flicking on and off, along with the amber crew alert CAUTION message, and had been doing so for several days.

“The student neither checked the caution nor cleared the flashing alerter, so it continued to flash for the whole flight.

“Part way through the flight, while in IMC, the ‘R ALTN FAIL’ caution also came on.”

The aircraft flight manual and Quick Reference Handbook (QRH) have the following warning:

“So, ignoring these cautions could have left the student with a double engine failure in IMC. That’s not something anyone wants to gamble with,” Dave says.

Why do pilots ignore alerts?

“Ignoring alerts during training sets a dangerous precedent,” says Dave. “The law of primacy tells us that what students learn first, sticks. If they learn to dismiss warnings, they’ll carry that habit throughout their careers.”

Modern aircraft generate multiple alerts – for example, warnings, cautions, and advisories – and some faults are intermittent, or the fault is with a sensor.

When a warning light pops up every second or third flight and nothing bad happens, pilots start to normalise it. This is sometimes called ‘normalised deviance’ – or accepting abnormal conditions as normal – because they occur frequently, without immediate consequences.

“This habit of tuning out alerts is dangerous because it blurs the line between what’s routine and what’s critical,” Dave says.

He adds that to break that pattern, pilots need a clear understanding of the different alert levels and what each one demands.

“Checking the alerter whenever it flashes, and knowing the difference between a warning, a caution, and an advisory – and responding correctly every time – is essential for safe operations.”

Know your alerts

• Warnings: These are critical alerts that require immediate action. Audio and visual signals persist until the pilot acknowledges them.
• Cautions: These are less urgent, but the pilot still needs to acknowledge them.
• Advisories: These are informational, often listed in system pages. 

“Pilots must acknowledge and act, even if the alert seems routine,” says Dave.

“Use your QRH and action the checklist for Warnings and Cautions. For example, a terrain clearance warning requires either a visual confirmation and inhibition, or a climb.

“No response to an alert is not an option.”

What if it’s an ‘Acceptable Deferred Defect’?

Some defects and associated cautions are permitted under the Minimum Equipment List (MEL), Dave explains, and should be recorded in the tech log. The MEL sets out what equipment can be inoperative, and any conditions that may still allow a flight to proceed. Warnings cannot be deferred under an MEL.

‘Deferred’ does not mean ignored – it means managed under strict rules. Even if a caution is deferred, pilots must:

• acknowledge the alert and confirm awareness with crew
• check MEL compliance and apply any restrictions
• monitor the system closely during flight. 

What if it’s a false alarm?

“Pilots often can’t tell if a warning or caution is a false alarm,” Dave says.

“That’s why it’s important to have good technical knowledge of your aircraft, and it’s a good idea to keep the QRH and flight manual handy. Always follow procedures and, whether it’s a system fault or a real issue, treat every alert seriously.”

Key points

Never ignore a warning, caution, or message. Train yourself – and your students, if you’re an instructor – to respect alerts, acknowledge them, and follow the checklist actions.

Safety depends on breaking the cycle of normalised deviance.