I just started flying an aircraft with a pitot mast cover in the document bag. Among the aircraft I have been flying regularly, this is a first – it is not commonly used here. The plane’suser group is currently discussing whether the cover should be used per SOP. The general view is that the risk associated with forgetting to remove the cover before flight is greater than the risk of something – most likely an insect – entering the system and causing, actually similar, problems. It is not that any of us don’t do walkaround preflight checks, it is more that even with the best habits & intentions someone is bound to forget to remove it one day, or so we imagine.
I have heard both kind of stories, i.e. forgetting to remove the cover – AND the case with an insect appreciating the internal dimensions of the pitot-static system with instrument troubles as a consequence. But only one of each, so I would like to hear more. In both cases, there was a safe outcome, but an IMC departure would not have been fun.
And yes, the cover has a fine red REMOVE BEFORE FLIGHT tie, but we all know Murphy.
The school I currently rent from doesn’t have pitot/static covers on any of their aircraft, while the club I got my PPL used them rigorously. Tbh I think the likelihood of problems arising from not using one is probably smaller than the other way around.
I absolutely use them on both my planes if parked for more than an hour or so. Those bloody bugs will have a nest packed in the pitot tube in less than the day or overnight. I’ve cleaned out too many, so covers for me!
I use the covers, it saves anything getting in and clogging it up.
Fortunately I’ve never forgotten to remove it as it’s pretty obvious when I do my pre flight walk round. However I’d like to think that if somehow it did stay on I’d still be able to fly and land the aircraft without too much difficulty.
All covers and plugs if parked more than hour.
Had an interesting case at a flying school – usually they didn’t use a pitot cover as the a/c were used every day, and when not – the weather was too bad for insects to fly. But! The runway was closed for a week in a really good weather and it meant we’ve got precisely that problem – bugs in the pitot tube, hence the pitot covers.
For school I’d say it’s debateable, but for a private aircraft IMHO it’s needed more.
I am sure a PT cover with some special material will do a far better job: if someone forgot them and went to fly in IMC with PT heat ON it will melt away 
Aircraft parked on grass, well I prefer to put the PT cover ON (and switch PT heat OFF)
Aircraft parked on hard and dry day, it is debatable what you do with PT cover/heat?
Flight schools flying in tarmac & sunny days, will have their ways
I fly in grass & clouds, so I have my own ways
Is there any POH that doesn’t mandate use of a pitot cocer?
I can think of at least 3 spoiled trips when the pitot/static had become blocked on the Robin.
We could never understand how it so reliably failed if the covers were not in place. ( the norm would be to use them but we can all forget at times)
I don’t remember exactly but it goes along the lines of…
One day we left the aircraft on the apron, paid landing fees and were about to go off somewhere when the wife remembered the covers and the trouble we’d had in the past.
I returned to the aircraft to find some insects/flies on the fuselage and some near the static. Before I could do anything I actually saw one disappear inside!
Very rarely forgot after that.
First thing I do after exiting the airplane is to put the cover on. You have NO idea how quickly bugs can get in there !
