To clarify GunChleoc's point a little...
When you say SCOTTISH AIR AMBULANCE, are you really saying is SCOTTISH AIR AMBULANCE SERVICE, but dropping the word "service"? Or SCOTTISH AIR AMBULANCE CREW, but dropping the word "crew" or similar?
Notice that in English you have a "toothbrush", even though you use it on multiple "teeth", not just one "tooth".
In English we don't "count" our first noun the same as we do our second -- so an "estate manager" and an "estate agent" both have the same "estate", even thought the estate manager manages one
estate and the estate agent sells multiple
The difficulty in tr*nsl*t**n is that two different meanings may share a form in language A, but not in language B, so it's impossible to tr*nsl*t* a short phrase without quite extensive explanation of the intended meaning.
Now because the air ambulances aren't a separate "service", but part of the normal Scottish Ambulance Service, I'm kind of unsure what the correct interpretation would be. I'm feeling more the plural interpretation, with an unspecified "team/dept/service/division/[whatever]" implied. What does it feel like to you?
The second problem is that GunChleoc's version of "air ambulance" matches the dictionary, but it literally means "medical-care plane", and you're in a helicopter, and half the air ambulance fleet is helicopters (actually more than half if you count the SCAA!)
This doesn't mean it's wrong -- the origin of a word is not necessarily its current meaning.
You probably know that the word "ambulance" originally meant "walking" as in "walking wounded", and no-one cares that an air ambulance doesn't have feet, so it's not necessarily a problem that the Gaelic for "air ambulance" technically refers to planes.
However, the problem is that words get fixed meanings through frequent use, and people don't talk about air ambulances all that much, so a lot of people might still hear "plèana-eiridinn" as "plane ambulance" rather than "air ambulance".
Certainly I've seen "heileacoptar-eiridinn" used on the series about Inverness airport.
So yeah... sorry that's so long and complicated, but tr*nsl*t**n on the whole is long and complicated