I was picking up my car from a service, and the man before me was an army helicopter pilot (who else would wear a green flight suit?), who went through every line on the invoice and made them justify why it had been charged. The receptionist was almost crying. I’m guessing he’d been caught in the past, and/or was making a point for some reason.
I’ve suffered mission creep from this garage, so understandable. One thing I’ve learnt from aviation is to keep a copy of the book which has service intervals, so when they tell you a time/distance limited part needs replacing at x hundred price, you can check if it really needs doing.
Probably due to complaints and awkward customers, the mechanics now take a video of the work that needs doing with the reasons why, and the office email it to me. This works well. Some things you have to take on trust, but some things are really obvious in the video.
In any environment the knowledge gap between supplier and customer is very profitable 
I quickly learned to mistrust most car maintenance places when I bought my first car, 6 year old, in 1960. I trusted the bank.
Now I trust my car service company, but NOT my banks.
Aircraft service, after our local guy retired, was an expensive disaster until we got on an LAA Permit. I’m happy with the new local facility, which I’ve used.
Does anyone have good experience with trying to force a stricter contract with the maintenance shop, like the article suggests? I’m active in a parachuting club which has eternally bad luck with maintenance shops. We’ve been let down by just about every maintenance center we can find within reasonable distance, this includes them doing things we haven’t asked for, them not doing things we have asked for, and most commonly, them being totally unresponsive as to how far they’ve progressed and giving any ETA for when we can have our poor Cessnas back. It just feels like if we went to them with a agreement of some sort that spells out demands like the article says, they would say that that’s not how they operate and refuse to work with us.
In my car repair business, we are VERY careful to extract specific authorisation for any work before it is carried out.
Disputes do no-one any good and can be virtually eliminated by careful management of customers’ expectations.
Even then you can still come unstuck because it is sometimes impossible not to expend time and effort evaluating a problem before you can give the customer and information and even doing that can cause disputes with unreasonable customers.
I’ve never left an aircraft to a maintenance outfit for repair as I do my own but you can be sure I would make it absolutely clear before I left that they were not, under any circumstances, to carry out any repairs without express authorisation from me.
It just feels like if we went to them with a agreement of some sort that spells out demands like the article says, they would say that that’s not how they operate and refuse to work with us.
I am sure a few would go along with what seems a perfectly reasonable suggestion, while others would just tell you to go elsewhere.
I think one of the issues, viewed from the firm’s side, is that they have to spend some time (money) establishing the full extent of a job, and if they had to seek consent for every chargeable event, they would get too many customers getting upset and taking the plane away. So, to some extent, the “fait accompli” method works better for them. Unfortunately some % of customers turn up with a plane which is a can of worms and they want to get something for nothing.
Equally unfortunately, as this and many other threads here show, the reputation of the business is hardly stellar, so building a relationship with somebody who is good is as important as it is difficult because – with certain cultural exceptions – most people will never again use a firm which did a bad job.
