'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?

You may be as well to request a clearance to operate 'not above' 1000ft QFE then you will have the freedom to change height as required.

Errrr......would it not be 600 AGL without any reference to an altimeter setting?


QFE (ancient and out of date quaint practice that is... would only be used for the single small spot/area on the aerodrome) would not be useful for determining true height above ground outside that location.


It would seem a QNH reference ( altitude requested providing the legal clearance required by the 500 foot rule) would be much more useful.


I assume ground elevation figures on UK charts/maps use height above Sea Level....thus a QNH altimeter setting would apply vice QFE.


The most immediate question is "how does one get nicked for violating the 500 foot rule in the situation described by the original post?"

In light of the F-15 crash following ATC providing an improper altitude clearance and the pointed criticism of the controller by the RAF review board....would not this clearance be improper?

SASless - You should fly on QFE within a MATZ because its dimensions are based on the airfield datum and all circuit traffic is using QFE. Regardless of ATC instructions the pilot is responsible for terrain clearance (as with F15s) not ATC.

Not quite sure why so much of the world has a problem with the concept that an altimeter reads zero when you land (using QFE) it's not quaint just because you don't like it.

Cyclically - most MATZ circuit traffic is at 1000' QFE so a standard clearance would be not above 500' QFE to give adequate separation from circuit traffic.

If you want 600' or more then ask for it in your initial call - ATC are not clairvoyant. ie - request MATZ penetration at whatever height on QFE that you think will keep you 500' agl or more inside the MATZ.

If you cannot get the height you need due to circuit traffic then either wait, go around the MATZ or accept that you are flying in compliance with ATC instructions and are unlikely to be reported or prosecuted for illegal low flying.

They don't: they have a problem with the fact that a) sometimes you won't be able to set QFE if the airfield elevation is too high, thereby requiring a location specific change in SOPs, which is generally considered a bad practice, and b) it's one more altimeter setting to make, with one more potential for error. CFIT being the biggest cause of accidents, tends to focus the attention on limiting altimetry errors.

An instrument approach is just to a number, it doesn't matter what datum you are using. The actual landing is done visually, so it doesn't matter what the altimeter says as you land (in a helicopter it will read negatively, while IGE, anyway, until you lower the collective after touchdown due to Pressure Error ;))

Sorry for thread creep :ok:

Whats the problem with 500 ft ? The rule is 500 ft away not above. Therefore if you are at 500 ft on the qfe then you are not breaking any aviation rule with the exception of 1000ft rule if flying over a built up area. The CAA will not go for you - how do the muppets prove it ?

Cyclically: I believe that in the military 500' is either a traditional or standard height preferred for airfield crossing which provides adequate separation from the standard 1000' fixed wing circuit operations. I seem to remember a NATO reference to it somewhere. However, using QFE as the datum is fine and I do not see an issue with using it and all military traffic in the ATZ will be using it. I think that if your intended crossing point were outside the ATZ but within the MATZ you would be asked to set the QNH for the field.

I can see a problem when you are asked to set the QFE and given a height to fly not above when you are transiting within the MATZ and ATZ but clear of the airfield. As you say, the ground may come up to meet you and you might think you need a shovel to comply with the cleared level.

I seem to remember a reference to ATZ/QFE, MATZ/QNH otherwise Regional below transition. No doubt I will be corrected.:E

i know the canadian air regs have an exemption for the 500' rule for the purposes of aerial inspection...do the JARs have a similar rule? if so would your low level survey fall under such an exemption?

212man - a) is not a problem in the UK and we fly around on RPS or QNH outside the MATZ just like everyone else so b) is irrelevant.

Maybe we should all use QNE for landing, that way you never have to reset your altimeter from 1013:)

The instrument approach on QFE is usually to the same numbers eg 150' for helicopters on a PAR or 200' for ILS so you don't have to do maths whilst flying - generally safer all round I would say.

As for pressure error - unless you are at the airfield datum your altimeter could be many feet positive or negative before you take-off - decision height or MDH are well outside ground effect anyway:)

Not sure this thread won't slide into a QFE vs QNH debate (that must be on this forum somewhere...)
The problem with QFE is that almost noone else in the world uses it, and if you've been brought up with it, it's difficult to transition to using QNH for instrument approaches anywhere else in the world.
I remember reading a horror story in the mid-80's about an UK helicopter crew that didn't remember they had to use QNH when doing a radar approach at a German airfield with an elevation of 250' or so.
If memory serves me right, Oxford Air Training School doesn't use QFE at all, as their students come from all over the world, as just one example.

A very interesting thread, as I have also have been cleared to transit within MATZ not above 500' QFE (within the ATZ) over terrain that was higher than that of the aerodrome.

Afterwards this led made me think that maybe I should not have accepted this clearance as this meant I had to fly slightly below 500' agl although the aerodrome circuit was very busy with multiple FJs all at 1000' QFE. After consulting the Rules of the Air Regulations it does state that 500' in reference to Rule 5 RoA is measured in all directions and not just the vertical. This leads me to believe that unless your landing or taking off from a Goverment or licensed aerodromes in the UK then regardless of an ATC clearance you should not fly below 1000' of the height of the heighest obstacle within 600m of the aircraft when over a congested area or within 500' of persons, vehicles, vessels or structures which practically speaking means that you should not fly below 500' agl in the UK surely? unless your over a remote area.

Going back to the original question, IMHO no I don't think your being pedantic Cyclically, it shows an awareness that military controllers are not always familiar with the civilian regulations and a clearance offered by them does not necessarily have to be accepted as offered.

:ok:

500 ft QFE
 

Cyclically

I consider this a very good post as I have had a similar clearance issued to me.

The various replies are interesting but some do not really answer your question.

I believe that the clearance is issued because of the use of QFE at Military airfields. Once the controller has it in his head that you are low level, then it is easier for him to keep you in that band for other traffic purposes.

You rightly say that rising ground away from the airfield will force you to break the 500ft rule. This is your responsibility alone and I am almost certain a military controller does not have the authority to absolve a civilian aircraft from the ANO rule unless you have a CAA exemption.

When entering a MATZ I make it clear my position and the hieght band I wish to operate. This may not give ATC an easy time but as a MATZ is not controlled airspace then he cannot get too prescriptive unless you approach the ATZ.

Having said that, I have found, in the main, military controllers to be of the very highest standard in the operation of the airfield and MATZ.
If they no that you are operating in a particular height band then they do not have to bother you or other aircraft with unnecessary traffic information and I think that may be one of the main reasons.

As far as whether QFE/QHN/QNE is the best setting to use then our company uses QNH only for IFR operations which I do not have a problem with and does offer certain advantages as pointed out in an earlier post.

However having recently operated IFR into a military airfield on QFE then that did not seem to be a great problem either providing on the go around you remember, once he has finished with you, to set QNH for terrain clearance and making sure you do not bust into other controlled airspace above.

Regards

P

Crab....I assume you meant why does the UK cling to this practice and the entire rest of the world does not. You are now part of Europe (by means of the railroad and political convention) thus perhaps ya'll might want to change your ways to conform....it really is a simpler method than that practiced now.

Does the altimeter really...really....read "0" when one alights upon the airfield?

Leave it to the nitpickers to search for a way to be at 500.00 feet and not, heaven forbid 498.33 feet above the ground.

The rule is "not less than 500", the rule is not "precisely 500".

Try flying at 600 feet away, and if you are wrong, you have margin.

The altimeter is not more accurate than about 70 feet in any case, considering its own imprecision and inaccuracy. So if you set your altimeter to station pressure, and read 500 feet, you could be as close as 430 feet. Deal with it.

Despite the bugs in summer, and cold in winter, I'm sure glad I fly in Canada...

5ft, 50ft, 500ft, or 5000ft. Doesn't really matter much, pretty much do what we want, when we want. I think the rules in Europe would kill me.

RH

Watertight proof of infringement of 500 ft rule is not easy to come by. Prosecution is rare and successful prosecution rarer(Have there been any?). With normal instruments even the pilot cannot be sure of his exact height, let alone those on the ground. Fly sensibly (it sounds like you do) and dont worry about it. The path of least resistance is to accept the clearance and nail it at 500ft.
edit:
Even if you are at 300 ft AGL the complainer has to prove your track was within 400ft of his property, and what your height was, to get anywhere near a rule 5 infringement. (remember 3,4,5 triangles!)

Hear hear, QFE is a waste of time if you ask me. As soon as you leave the airfield it's useless. Even when on the airfield it rarely reads correct. Much more sense to stick to the QNH all the time, like they do in the USA.

I must admit that having flown both QFE and QNH airfield procedures I do prefer QFE.

Recently in the States I flew at three airfields in close proximity but with different elevations. I have to admit that having specified downwind, crosswind and baseleg altitudes as well as differing joining and departure altiiitudes all combined to ensure that I spent a good part of the circuit in busy traffic having to refer to a kneeboard to remind me of what height I should be at.

At least with QFE and a set of standard operating procedures you are eyes out at the important phases of approach and departure.

Oh and if 500 feet and below is unaceptable then perhaps it would be deemed safer for all to go round that piece of busy airspace..........

IMHO

Shawn, the horror story was possibly the one about one of our squadron aircraft, RAF based in West Germany. If so, it was at Buckeburg and I know the pilot well. They very narrowly missed the trees, which were infesting the clouds.

Thirty seconds to jot down three airfield elevations on a Mars bar wrapper beats fiddling with knobs....and in most locations the elevation difference is a moot point. Now if you are in an area where there is a really huge elevation difference one would not be able to set a QFE setting anyway. The Mark I Eyeball can work wonders in determining height and in theory should trump the altimeter unless one is truly addicted to "numbers on the clock".