Originally Posted by
Cyclically
The point I am trying to make is that if I were to accept this 500ft AAL clearance then (from a lawyer’s point of view in the unlikely event of being prosecuted) even if the ground is at the same elevation as the airfield then whilst I am going to be 500ft away from the ground I am NOT going to be 500ft away from the top of buildings, pylons etc that I have to fly over. Ignoring instrument errors and pilot accuracy then, albeit pedantic, this is fact and so if one flies directly over anything on the ground then this would be contravening rule 5. Once you then introduce elevation differences the separation may be even less (or more but that’s not the issue here) ...
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So my questions are therefore:
Do others agree that it is (potentially) a contravention of rule 5?
Do others happily accept this clearance?
As I see it, if you are not exempt from the 500ft Rule, then inevitably such a clearance as "not above 500ft" must put you in contravention of that Rule, unless the QFE datum on which it is based is on a significant plateau with respect to the area over which you are flying. I don't think it is pedantic to be concerned - put simply, in most circumstances this clearance would produce a prima facie breach of Rule 5(3)(b).
My answers to your two questions above are:
- Yes, absolutely
- I have not been put in this position (and I am not a rotary flyer) but if I were, the answer would be No, for the reasons given above.
Why do military controllers appear to be happy offering a clearance of "not above 500ft"? I had understood the military equivalent (in the relevant JSP) of the civilian low flying rule relates to 250ft rather than 500ft. Thus, such a clearance to the military would represent flying in a relatively "safe" band, i.e. between 1) above the absolute (JSP) minimum (unless specifically authorised) of 250ft and 2) below the civilian (Rules of the Air) minimum of 500ft. Now, I may have been misinformed, as the military rules contained in JSPs are not normally available to civilian pilots, (they certainly should be, but that is for another thread!) - but no doubt this belief can soon be confirmed - or corrected!
So, in summary, there could be several reasons for such a clearance being offered, viz
1) As you are on a survey, a military controller might assume you have an appropriate exemption from the relevant low flying rule,
2) They might be accustomed to basing their low-level clearances on a 250ft minimum rather than 500ft,
3) They might take the view that their responsibility within the clearance relates to other traffic in the area but the responsibility for terrain and obstacle clearance under VFR is yours.
Just a few thoughts ...
JD
