In all the years of doing my job I have never heard of "Crash Imminent" various categories apply where I work they are as follows.
1. Weather Standby; (weather conditions are such to render landing difficult or difficult to observe take off/ Landing
2. Local Standby;
When it is known that an aircraft has or is suspected to , developed some defect, but the trouble would normally not involve any serious difficulty in effecting a safe landing.
3. Full Emergency;
when it is known that an aircraft is or suspected to be in such trouble that there is danger of an accident
4. Aircraft Ground Incident;
When an aircraft on the ground is known to have an emergency situation, other than Aircraft accident.
5. Aircraft accident;
Aircraft accidents which have occurred on or are inevitable on, or in the Vicinity of the airport.
On Occaisions ATC or The Fire officer in charge have upgraded the incident to be safe rather than sorry.
