How low can a helicopter fly above a residence if the helicopter is an air ambulance landing?
Talk to a lawyer.
Disclaimer: I am not a lawyer, and this is not legal advice.
The fact of the matter is, regardless of whether or not they've got FAA clearance to operate the way they do, they're causing physical damage to your property. As such, I would recommend talking to a lawyer about what your legal options are. While suing them for damages would definitely be a step you could take, a lawyer would be able to advise you on how best to navigate the process leading up to that, potentially involving things like Cease and Desist letters or negotiated settlements with the company in question.
Since you're from America, it's also entirely possible that your state might simply seize your house with Eminent Domain and give you a token payment for its &quot;fair market value&quot;, since the construction and operation of a hospital with medical helicopters clearly falls within its remit. As a result, I would recommend to be prepared to start looking for a new house should you begin a dispute with them.