August 12, 2022

France’s Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) has just released its preliminary report about an incident that happened in late May, and it’s kind of terrifying. As noted by @AirlineFlyer, a plane with 172 passengers onboard was within six feet of crashing.

Incorrect altimeter setting leads to near disaster

This incident involves a flight on May 23, 2022, from Stockholm (ARN) to Paris (CDG). The flight was operated by a 23-year-old Malta-based Airhub Airbus A320 with the registration code 9H-EMU. The plane was operating under a wet lease agreement for Norwegian Air, and was carrying 178 people, including six crew members and 172 passengers.

The flight operated totally as scheduled until the approach. The weather wasn’t great in Paris, and the crew claims that they were in the clouds for the entire approach, and experienced moderate turbulence. That shouldn’t be an issue, since the pilots performed an RNP approach, which is highly automated and follows the glidepath. That’s the beauty of modern aviation.

The issue is that executing this kind of landing requires computers being programmed correctly, and this is where the issues started. Pilots need to set the correct altimeter, which is a measure of altitude based on air pressure.

Air traffic controllers will often remind pilots of the altimeter, but in this case the air traffic controller gave the pilots the wrong altimeter multiple times — rather than providing an altimeter of 1001, the controller provided an altimeter of 1011. The difference of 10 hPa would lead to an approach being carried out 280 feet too low.

Here’s the transcript of the ATC audio (“Red Nose” is the Norwegian callsign):

Controller: “Red Nose 4311, descend… descend 6,000 feet, 1011.”
Pilot: “6,000 feet, 1011… 1011, Red Nose 4311”
Controller: “Red Nose 4311, descend 5,000 feet, 1011, cleared full RNP 27R.”
Pilot: “Descend 5,000 feet, QNH 1011, cleared full RNP approach 27R, Red Nose 4311.”

Now, it’s worth noting that while there are other sources for getting the altimeter (like a METAR or ATIS), the company’s manual didn’t require that to be cross checked, since you’d expect the controller to give you the correct information. After all, an air traffic controller’s primary job is providing accurate information to pilots.

It’s worth noting that an EasyJet plane landing around the same time had the following interaction:

Controller: “Easy 75 Mike Alpha direct Papa Golf 650, and descend 5,000 feet, 1011, cleared RNP approach 27R.”
Pilot: “Direct to Papa Golf 650, descend 5,000 feet, QNH 1001, Easy 75.”

Funny enough, the EasyJet pilots read back the correct altimeter, without acknowledging it with the controller. Presumably they thought the controller was just making an obvious mistake. Meanwhile in another interaction, the controller gave Air France pilots the correct value, but that was in French and not English.

Anyway, back to the flight in question. On the final approach, the Minimum Safe Altitude Warning (MSAW) was triggered in the cockpit, and shortly thereafter the air traffic controllers received a ground proximity alert, so checked on the pilots.

Finally 0.8 nautical miles from the end of the runway, and at a recorded altitude of six feet above the ground, the pilots finally performed a go around. That’s right, the plane was six feet from the ground, and there was still a road between the plane and the runway, so imagine how that could have ended. You can see this all in the diagram below.

With the plane having been six feet off the ground, it’s safe to say they were literally one second from disaster.

Then there was a second approach…

The pilots attempted a second approach after performing a go around. The issue is that they still didn’t realize that they had the wrong altimeter, so they once again started their approach 280 feet too low.

As the pilots were on approach, they asked the controller if the approach lights were on (since they couldn’t see them), and the controller confirmed that they were. The Minimum Safe Altitude Warning (MSAW) was once again triggered on this approach. The controllers also got a terrain alert again, and informed the pilots.

The only thing that was different this time around is that the cloud coverage wasn’t quite as bad, so the pilots could perform a visual approach, and could correct that they were too low.

Bottom line

Aviation is incredibly safe, and is actually the safest form of transportation. For every disaster that actually happens, there are a countless number of near disasters. In this case an Airbus A320 was just six feet from crashing into the ground due to having the incorrect altimeter — I don’t think it gets much closer than that.

This incident happened because the air traffic controller in Paris repeatedly gave pilots the incorrect altimeter, making the pilots believe they were 280 feet higher than they actually were. With limited visibility, that can be the difference between life and death. Whether or not pilots have any responsibility here is above my pay grade…

What do you make of this incident?

(Featured image courtesy of Anna Zvereva)

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