It sounds innocuous doesn’t it? I mean the term, “Confirmation Bias” … a seemingly innocent combination of two ordinary words of the English language. Yet these words, put together in the environment of professional aviation have a potentially lethal outcome. Numerous analyses of aviation accidents have identified some key Crew Resource Management (CRM) failures which share common factors. One of these is Confirmation Bias. In fact, while operating commercial airliners, we are constantly aware of the presence of this highly dangerous phenomenon in our day to day working life. But why is it so dangerous? Well, to really understand the threat, you must consider that the safety and integrity of the operation relies heavily upon the operating crew maintaining good Situational Awareness.
This includes verifying all information which is received from outside sources. In fact, as individuals we professional aviators become a little bit difficult to live with at times in our home life. We never take anything at face value; we are constantly cross-checking the veracity of information received; we hate any reliance on any system which even hints at ‘single point failure’; we always have a Plan B, in short… we are often mistaken for being Obsessive and Compulsive in our private lives. I know for a fact that my own family hate it when I ask questions like, “What will you do if your first option is not available?” or “What will happen if your Plan fails?”
Here’s an example for you. When you are about to bring a boat into a dock which is fitted with fixed mooring lines, you know that you will not need to deploy your anchor. However, some of us ensure that we get the anchor ready for quick deployment anyway, just in case the engine quits and fails to restart. If this happens, the first thing you need to do is drop the anchor to give yourself time to fix the problem instead of being at the mercy of the wind and current. Call it contingency planning or healthy distrust of the mechanicals, but we pilots always have a Plan B…
Which brings us back to Confirmation Bias and why we are naturally suspicious of information which arrives in the flightdeck from any outside source. History has taught us that it is vitally important that we should be circumspect and cautious in order that we can protect ourselves from losing the plot. One way to describe it is in the words of an old aviation joke which ends with the punchline, “Don’t confuse me with the facts… my mind is MADE UP!”
Even in the earliest phase of learning to navigate aircraft with reference to ground features, we are warned that when uncertain of our position “Don’t try to make the ground fit the map”. It is essential to work with verifiable facts in a logical manner to prevent jumping to conclusions. When working as a crew, we use many techniques to ensure that our internal mental model of the world is an accurate representation of reality. We try not to use closed questions between us when flying aircraft and we ensure that the environment is conducive to any of the crew advocating their own suggestions in relation to our decision-making process.
For my own part I have a perfect example of Confirmation Bias from earlier in my career when I was working as a Line Training Captain for a scheduled airline which had only recently started flights. They say that hindsight is 20/20 vision and looking back, it is easy now to see how it happened. Although I cringe with embarrassment whenever I think of it, I am happy to share my mistakes with my colleagues so that they can learn from them. Bear in mind that the airline only had six aircraft, there were new routes being developed all the time and in fact most days at work seemed to be ‘organised chaos’! I reported for duty in the evening for a return flight to Athens from London Luton airport.
To complete the backstory, this was my fifth day on and all my previous days had been long ones. This was going to be a long night with an extended turnround planned once we arrived in Athens. This was in the late ‘90s and the old airport was still in operation with all of the noise limitations and performance restrictions. There was a night-jet ban which prevented us from taking-off before 6 am local time, hence the ultralong turnround.
On arrival in the crewroom I was asked to take a phone call from Operations. In that call, the Ops controller informed me that we would have “performance restrictions” taking off from Athens and if all the passengers and baggage were loaded as planned, then we would be unable to load enough fuel to get back to Luton. I was surprised I must say, because I thought that ‘tech-stopping’ for fuel was a thing of the past. However, this was in the early days of the airline and it seemed like everybody was learning… Of course, there was not much time for decision making and I was the Captain. “…so Skipper, what would you like to do?” I reviewed the options and looked at the figures carefully. Sure enough, we were about a metric tonne short of having enough gas to get back home in a one-er. I also consulted with the trainee First Officer and the Safety Pilot.
They had no better suggestions and we all accepted that our Operations people had looked at it. It seemed logical in many ways, the destination airport (Athens) was renowned for being tricky, high temperatures made for reduced engine thrust and longer take-off roll required etc. We were all aware of the dangers of engine failure on take-off when there was a published requirement for an emergency turn to avoid overflying the Acropolis. The Athens route from London had only just started and although I had previous experience for several years going there, that had been in the Boeing 757 which had much better performance margins than the B737-300. Whichever way we looked at it, there seemed no way out – using the maximum take-off power according to the performance tables, we could not lift the weight. But most importantly to us it seemed… the guys in Ops had told us “EXPECT to Techstop”. Not only that, but they also stated that we would have to change cockpit crew as we would be out of hours and unable to fly 3 sectors after our extended ground time.
As time was pressing now and I had to focus on the training of the new pilot and ensuring they were adequately prepared/briefed to fly, we decided to stop in Geneva enroute to Luton to change crew and refuel. From memory I think this was Operations’ preference because they knew they could get two pilots there easily from our London base. For sure, this flight was not going to make a profit… I shrugged my shoulders and we made our way out to the ramp. It goes without saying that the cabin crew were unhappy about the situation, but what could we do? The Flight Time Limitations (FTL) scheme clearly stated that they could work an hour longer than the pilots, so they were “in hours” to do the job.
It was agreed that we would call back to base after landing in Athens to make sure that nothing had changed regarding the expected traffic load and when we had the actual Met. conditions. Bear in mind, when planning we are always working with the forecast weather which is sometimes better or worse than the actual. The departure and outbound flight were uneventful, albeit that the flight time was the best part of three and a half hours. After landing, we confirmed with the handling agent what the expected (booked) load would be and sure enough we could easily see the performance deficit. The call to Ops was made and they assured that the relief crew would be waiting in Geneva for the time of our arrival.
As we settled down to wait in the aircraft for the next 3 hours, I mulled it over in my mind. There was something which just didn’t quite add up… We had all looked at the problem, reviewed the performance tables carefully and even taking every possible advantage into account, the aircraft was still short on performance. Oh, how I missed the beautiful 757 with all its abundant power from those RB211 engines…….
The hours ticked slowly by and we got more and more tired, of course we tried to snooze and rest before our next flight, but it was unsettling knowing that we would have to inform the passengers that sadly they would be seeing Geneva enroute to Luton. Not only that, but the weather forecast for GVA was heavy rain and low cloud with associated poor visibility - Yuk! Finally, the passenger boarding commenced with about 35 minutes to departure. We started to gear ourselves up in the cockpit and worked on the performance calculations. Not an easy task – it was now the early hours of the morning and we were all suffering the effects of being at our circadian low. Again we ran the numbers and there it was 1000 kilogrammes too heavy if we put on enough fuel for Luton – “well it’s not relevant now anyway” I recall saying to my two much less experienced colleagues, “we’re planned for the techstop and crew change…” Then it hit me like a train. “Hang on a minute! Where’s the performance tables for a Bleeds-Off Take-off…?”
Two minutes later, we located the big folder with the RTOW* performance for take-off without the bleed air pressurising the cabin. In this case of course, we would leave the APU running to provide the necessary air pressurisation. The engines, relieved of their load to provide cabin air, would have significantly more power. And now here it was in black and white, another 1400 kgs would be available, we could do it! But there was not much time to make all the changes. After all, we had refuelled a couple of hours ago and now we had passengers onboard – a call to the ATC Tower confirmed that we would need Fire Crew cover to refuel with pax onboard. “You will have to have the big Fire Extinguisher and there will be an extra charge…” that didn’t sound good. There would also be an extra delay to get it here and what if the Cabin Crew went out of hours in that time? A new flightplan would be needed – that would take time to file and send through for the handling agent to print off – would it arrive in time?
On balance there were too many variables now and although I cursed myself for not thinking of it earlier, we had to accept the situation for what it was. We were going to have to fly to Geneva. And in fact, all the above is what I said in the interview with the airline’s Chief Pilot a few days later when I was asked to explain why we flew home via Switzerland from Greece. To his credit he was very understanding about it and we used the whole episode to provide some very useful training feedback to the inexperienced controllers in Operations. In reality, the airline management was “fire-fighting” on a daily basis and this had just been another minor crisis**.
For me (a supposedly experienced Training Pilot at that time) it was a salutary lesson in the dangers of Confirmation Bias.
*RTOW Tables – Regulated Take-Off Weight Tables of performance figures. A very much outdated method of assessing airliner performance. In most airlines it has been replaced by electronic systems giving better accuracy, safety and overall enhanced SA.
**Those early Athens flights were often very challenging, not least because of the length of the turnround. There were several instances of exhausted crews being the subject to Prolonged Loss Of Communication (with ATC) on the return flights and subsequent airborne interceptions.
Captain James McBride started his military flying career in 1983 with the Royal Naval Fleet Air Arm where he flew Harrier and Seaking Helicopters. He has been flying airliners commercially since 1989 - operating as First Officer, Captain and then Training Captain (Check Airman) all over the world. He qualified as a UK CAA Type Rating Instructor (TRI) on B737 in 1999 and Type Rating Examiner (TRE) the following year. Additionally, he has been a TRI/TRE on B757 and B767 fleets for several airlines. Besides his airline flying, James flew historic aircraft in Air Displays for 7 years authorised for low level aerobatics to 50 feet AGL. While working part-time as a Flying Officer in the RAFVR, he was part of the Royal Air Force, Air Experience Flight for Air Cadets in the early 90s – simultaneously flying charter B757s as the ‘Day-Job’. In the larger Boeings, he considers himself fortunate to have had the chance to fly Long-haul operations for National Flag Carriers (both passenger and cargo). He flew for Low-Cost 737 airlines and even VIP Airliner (737 & 757) flying for a specialised operator carrying Heads of State, Royalty and Rock-Stars. He has shared his experiences in several books published on Amazon. In 2014 he wrote the first in the series called “The Flightdeck Survival Manual” – How to survive a career, flying aeroplanes for a living. He is still current on B737 and 757 types flying in Europe and lives in Athens, Greece.