I did once investigate such a project and my first guess had been a project cost of maybe 5000 Euro. I would only engage in this if there is a huge incentive. For example you live next to a place which only allows 1000kg MTOW planes or if your airport charges you 500 Euro per month less for the hangar if you are below 1000kg. Just for a few Euros in normal landing fees between 1 and 2 tons I do not think it makes sense. 2t is obviously another matter as the overall cost delta can be very substancial depending on where you operate.
Thanks @malibuflyer
Malibuflyer wrote:
For practical reasons I fully agree that changing the noise certificate (no idea if you finde somebody to issue a noise certificate with a different MTOW)
I think it’s in Spain & Germany where I paid my landing fee based on MTOM from the noise certificate for a G-reg DA40, I doubt I ever got asked for it elsewhere, I have seen all sort of weights in landing invoices from 1T to 1.7T, no idea where they get those numbers as I did not hand anything…
For N-reg, I generated one myself from engine & propeller (no point saying you don’t have it as get you the 10T ticket 
)
Peter wrote:
Somebody has to do it,
Sure – but as said before: For a type that is already below 2t and therefore just for “saving” some landing fees the cost is very likely much higher than what you realistically can save over time – plus the substantial reduction of utility in a 1t airplane if you loose >50kg useful load…
If you had to do the STC yourself: forget it!
Somebody has to do it, and e.g. the Seneca < 2000kg STC was done by one pilot by himself – the well known Charles Strasser. He never even made money out of it.
Ibra wrote:
You need to reduce it in noise certificate and aircraft database to pay less, the AFM ou AFMS and STC are irrelevant
The official MTOW is in the type certificate and AFM/AFMS. For practical reasons I fully agree that changing the noise certificate (no idea if you finde somebody to issue a noise certificate with a different MTOW) and the Eurocontrol database entry would safe you from fees as these are the only things that are checked when calculating fees, but this still does not change MTOW.
Snoopy wrote:
What is required? STC? DOA?
You need an STC and this STC will include updated AFM/AFMS pages. It is not only the numbers but also the pages with Va at max MTOW. It might also be that some placards and eventually even the airspeed indicator needs to be changed (as the Va used for markings is Va at MTOW and it is obviously reduced when you reduce MTOW).
All in: You need to save a lot of landing fees to compensate for the cost of getting this done. The <2t STCs are made for avoiding airway fees, not landing fees, and even there many people doubt that it is worth the hassle and the reduced use of the plane at lower payload…
If you had to do the STC yourself: forget it!
I think doing this for lower landing fees is short-sighted, unless you are never going far from base. Probably true for a school.
It is normally done to avoid Eurocontrol IFR route charges, which are quite significant.
Why not getting two seaters like C150s/152s? or DA20s?
I actually know a flying school based at a regional “international airport” that operates Cherokee 140’s rather than warriors/cadets to take advantage of the lower landing fee it brings.
Replace the strut bolts with weaker ones and let Eurocontrol know 
