If I have a C150 and buy it for £16,000 fly it for 1,000 hours and put some cash to one side to cover a new engine, do I sell it for £16,000 and give them the engine fund?
No, but
you still have that cash, with most groups any cash belongs to the group, if you sold the aircraft and folded the group then the cash would be split amongst the group, selling a share though you do not normally get your share of any cash in the fund when you sell your share so you must also sell your share of that cash - if not you are
giving the new share owner
your cash!
The fund belongs to the aircraft not the shareholders.
And you are buying a share of the aircraft not the shareholder so if the fund goes with the aircraft you must also be buying a share of the fund!