The dangers in Expectation Bias – A real life story from member Aaron Benjamin

Some thoughts about expectation bias and how insidious it can be, the morning after my first approach in actual IMC at night, which was down to 640 ft, approximately 440 ft above DA on the ILS 11 at KMSY (Louis Armstrong New Orleans International).

This was the end of a long 540 nm night cross country with beautiful VMC until about 10 nm from New Orleans.  There were two large convective cells around New Orleans but as I approached from the NE, the cells were around 40 nm NW and 50 nm SE of the airport.  There was light to moderate precip just north of the airport so I asked for vectors east direct Harvey VOR then direct KMSY.  New Orleans Approach vectored me southwest to the ILS 11 through a break in between two clouds groups and the ATIS advised several scattered layers, the lowest at 1100 ft. 

This is the first approach I’ve flown with clouds/mist lower than 1000 ft and it was dicey.  I was vectored around to intercept the localizer about 3 nm from the FAF and at first I over-corrected to try and center the needle and accidentally allowed a descent a little bit before passing the FAF.  The tower asked me to confirm I was established and I responded affirmative since I was less than one dot off the localizer and recapturing my altitude. 

I got the glideslope back before the FAF and focused on holding that  glideslope while the localizer strayed a little. I forgot how sensitive that needle gets as you progress towards the runway.  

I realized I had been mentally unprepared for actual IMC down to minimums but 440 ft above DA the bright ALSF-2 lighting system on the 150 ft wide runway 11 at MSY filled my windshield and I only had to make a slight correction to the right to get aligned with the rabbit as I followed the glideslope down to an uneventful landing. 

The lesson I take from this is the same lesson Gary “GPS” Reeves teaches in his advanced IFR course at ALWAYS EXPECT to not see the runway, always expect to go missed, always expect to have to divert.  Expectation bias is a real pilot killer and although I try to keep this in mind, every approach I’ve flown in IMC in the short time I’ve had my instrument rating has ended with a breakout somewhere above 1000 ft AGL (usually way above).   So without even thinking, I flew onto that localizer course fully excepting to see the runway pretty shortly after starting my descent on the glideslope.  Having subconsciously formed that expectation it was a REAL SHOCK when I had to call out 900 for 204 still in the clouds. 

I will be mindful to never do that again and to maintain safer expectations such that, no matter what the ATIS says, I will from now on expect to fly every approach down to minimums and to have to go missed.  Every breakout and landing will be a pleasant surprise.

Aaron Benjamin 

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One thought on “The dangers in Expectation Bias – A real life story from member Aaron Benjamin

  1. A good reminder to expect to go miss. My personal minimums are double the actual minimum but still conditions can change quickly. Expect to miss and enjoy the pleasant surprise when you break out to see runway!!!

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