'Not above 500ft'
I fly a regular 'low level' survey in an SE helicopter in the UK which, due to its nature, takes us through many MATZs. We do not have any exemptions to fly below 500ft and so fly at 600ft AGL or above. I also make a point of stating on the radio that I am AT 600ft AGL (or sometimes just not above 1000ft). However the military have a habit (or perhaps a standard procedure, I’m not sure) of routinely responding with a clearance/request of "not above 500ft (QFE)". I always refuse this clearance (quite often to the disbelief of the controller!) and repeat that I need to remain AT 600ft (or not below). My reasoning is as follows…
If we assume that the ground I am over is at the same elevation as the airfield datum then if I comply with this clearance I am AT BEST only going to be 500ft above the ground. This therefore means that I will potentially be less than 500ft from any "person, vehicle, vessel or structure" as they are always closer to me than the actual ground. (and of course if the ground is higher then the problem is worse, and vice versa)
Yeah, ok, we are only talking about a few feet in many cases - e.g. I could now find myself at 450ft from a building or less than 400ft from power lines) but how would it stand up if someone were to be taken to court over it? I’m sure it wouldn’t be difficult for a lawyer to convince a jury that if one were to accept this clearance then contravention of rule 5(3)(b) (The 500 feet rule) would be inevitable.
I quite often hear this clearance accepted by other transiting aircraft (normally helicopters) so am I just being too pedantic? I would be grateful to hear other people’s views on this subject.
Oh, and finally, just to add further frustration, after being given this clearance and subsequently requesting a greater height I am quite often told something to the effect of "600ft is approved – there’s no traffic to effect"!! So why did they request it in the first place? Again, if there is anyone who is familiar with military ATC I would be grateful to know if this is a standard military procedure.
When speaking to the military would I do better saying that I am at 600ft MSD?