15th May 2024

Distraction from the task

Initial Report

This was a pleasure flight. Prior to the flight I did a thorough risk/threat analysis so as to be prepared for any eventualities. The destination airfield has no instrument approach and was in busy airspace right beside [Regional Airport]. I anticipated that traffic for/from Heathrow, Farnborough, Southampton, and Gatwick would be a factor as I approached my destination, and I anticipated that, as before, I would be using an approach to nearby [Regional Airport] and would be vectored from there to my destination. I have done this trip several times before and the same approach has always been used so I had that plate ready and I had self-briefed the approach with the fixes and altitudes so as to be fully prepared.

So it was to be a leisurely and relaxed flight. Initially I was with East Midlands on a Traffic Service at 4000ft and then East Midlands cleared me to join controlled airspace with a heading and an instruction to climb to FL200. Then I was given a new heading and was told the approach I was to use for [Regional Airport]. This was not the one I have prepared for but a different one. As I received this information just after I had set FL200 on my altitude capture autopilot I went to retrieve the correct plate for the arrival and at the same time set the new heading. The plate was in my trip bag on the P2 seat and it took me a very short time to retrieve it and then I was looking at it to see what differences there were from the approach that I had studied earlier. Whilst I did this I kept an eye on the altimeter and verified that the aircraft had captured ALT at FL200.

Then radar asked me to check my altimeter settings because I was 400 ft above my assigned level. I did this and immediately realised that when I was given the new approach I had set FL200 on the altimeter but had not yet changed from QNH to 1013. I immediately corrected this and adjusted to FL200. Lessons learned:

  1. I had noted the new approach on my kneepad and the plate would not be needed for at least another 10mins. So instead of reacting straight away and going for the new plate I should have continued my existing task which should have been to set the new flight level and set the altimeter setting without being distracted by getting out the new plate.
  2. On capture of FL200 I should have done what I usually do which is to verify the level with the other two altimeters and also with the transponder.

I was at the time too relaxed in thinking that I had been thoroughly prepared and so when the new approach was advised I thought that I should check it at once, since this approach would take me closer to Heathrow and Farnborough airspace. So I allowed myself to be distracted and did not properly complete that task I had started.

CHIRP Comment

We’re grateful to the reporter for this frank and open report that describes a trap that any of us could easily fall into; there are not many aviators who haven’t forgotten or been late in changing pressure settings at some point – that this resulted in a level bust in this incident is unfortunate. The reporter has covered many of the lessons to be learned, with the key one being the need to complete one task before moving on to the next (or go back a couple of steps in the process if interrupted or distracted whilst conducting a task) using the overriding priorities of ‘Aviate, Navigate, Communicate’.

Arriving at FL200 without noticing that they hadn’t set 1013 on passing through the Transition Altitude perhaps hints at either some distraction well before the levelling-off stage or maybe a degree of complacency in that the reporter may have been in a state of low attention given that they had flown this route many times before and could have been subject to habituation: the aircraft type the reporter was flying required a type-rating and considerable experience, and so it was possible that their full attention might not have been applied during what was likely a routine and simple ‘milk run’. It’s a well-known hypothesis in aviation that sometimes the most dangerous time in your flying career is when you’ve become so experienced and familiar with the aircraft and flying that you cease to pay full attention to the basics or the task in hand (setting the altimeter at Transition Altitude in this case) and are not properly prepared for a change from the expected normal routine (such as the change in approach from that planned). This is something we all need to guard against if we ever feel that we’re absolutely on top of things and can just relax as it all ‘runs on rails’.

Key Issues relating to this report

The following ‘Dirty Dozen’ Human Factors elements were a key part of the CHIRP discussions about this report and are intended to provide food for thought when considering aspects that might be pertinent in similar circumstances.

  • Distraction – changed focus during level-off instead of completing the task in hand.
  • Complacency – reduced attention to the task due to habituation.
  • Deviation – did not complete the usual level-off checks.
  • Complacency
  • Deviation
  • Distraction