18th August 2023

Pitot cover left on

Initial Report

A fellow group member and I had gone out for a lunch away on a fine flying day, with light winds and fluffy scattered Cu.  He took the outbound leg, and I brought us back to base.  We parked on the Visitors Line because I had arranged with an instructor that I’d go back out with him in a couple of hours’ time to do my biennial.  There was plenty of fuel aboard, and I didn’t bother with any “putting to bed” things like pitot cover, exhaust bungs, canopy cover, etc.

Time came for the biennial flight and, after a briefing in the club house, we walked out to the aircraft, parked with its tail to us on the Visitors Line, climbed inside, and went through normal start-up procedures, taxi, checks, and take-off. All was normal until lift-off, when glancing at the ASI, I saw implausibly low figures. First disbelief, then confusion, then acceptance that I had no air speed indication. I guessed that the pitot cover might still be on, although I hadn’t put it on when leaving the aircraft earlier.

Next, fly the aeroplane. Pitch and power and control pressure and sound, orchestrated to provide me reasonably good guidance on air speed. The instructor, to my right, gave me readouts on ground speed, as displayed on SkyDemon. We made one circuit and landed without drama. Shut down at the hold, and the instructor leapt out, went around to the port wing, and brought the pitot cover back to me. We took off again, with a good ASI, and had a very pleasant flight.

Afterwards I surmised, and later confirmed, that after our earlier lunch-away flight, my friend had installed the pitot cover while I was doing post-flight paperwork and I hadn’t noticed. So when I walked out with the instructor for the later flight, I assumed the aeroplane was ready to fly. Long ago, a wizened old instructor informed me that “ASSUME” has no place in aviation, as it makes an ASS out of U and ME. This incident taught me that I should remember that maxim, and never skip a walk around after leaving and later returning to an aeroplane, assuming it will be as I left it.

CHIRP Comment

As the reporter infers, the pre-flight walk-round is an essential activity that must not be skipped; anything could have happened to the aircraft after it has been parked, ranging from a helpful person putting covers on as in this case to someone driving or taxying into it and causing damage. Given that the subsequent flight was a biennial check, one of the things that an instructor could usefully do is to accompany pilots when conducting their walk-rounds so that they can not only confirm that the right things are being looked at but also offer thoughts on other aspects of ground operations and aircraft readiness to fly.

As an aside, although the reporter coped well with the situation once airborne, don’t forget the value of checking that the airspeed is registering early in the take-off run. Had the reporter done so then they would likely have noticed that the ASI was not indicating and could have aborted the take-off prior to getting airborne. Although it’s not a formal rule, many use the rule-of-thumb that the aircraft must achieve 2/3 of the take-off speed within 1/3 of the calculated take-off distance.  It’s always a good idea to have a marker in your mind at the side of the runway if possible for this distance where you will check the airspeed has increased as expected. In doing so, you’ll not only detect things like pitot covers being left on, but will also detect things like an engine that isn’t operating correctly or the aircraft isn’t at the all-up weight you think it is. If you don’t achieve the 2/3, 1/3 rule then abort the take-off and investigate.

Key Issues relating to this report

Dirty Dozen Human Factors

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.

Awareness – the pitot cover was there to be seen but wasn’t checked

Teamwork – the instructor should have confirmed that walk-round checks had been completed

Complacency – assumption that the aircraft was in the same state as it was left; not checking airspeed early in take-off run

Deviation – walk-round checks not carried out

  • Awareness
  • Complacency
  • Deviation
  • Teamwork