'Not above 500ft'

[check]

Unless I am misinformed QFE as from 1st September is no longer used for landing in the UK. Certainly on an instrument approach you are no longer given the QFE. On one of my last approaches in the UK I was given only QNH but was asked as it was early days , would I like the QFE.

I really don't have a problem with QNH as SASless says every one else uses it and like everything else you get used to it.

[Cyclically]

Thanks for everyone’s comments but perhaps I didn’t phrase the question(s) quite right.

Firstly let’s not turn this thread into an argument about pressure settings – that’s not the issue here (I’m sure there are many other threads where that can be done). Regardless of what pressure setting they use they are still asking you to be in the piece of airspace. i.e. 500ft AAL.

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). We have to follow a specific route so I can’t avoid over flying every object on the ground and it also takes us right to the airfield boundaries so I can’t avoid the ATZs without loosing some of the survey due to ‘ATC restrictions’

With regard to being prosecuted, I appreciate unlikely but, I am considering the instance where one is heard to be accepting the clearance and therefore 'must' be breaking the rules rather than simply being reported for low flying by someone on the ground. Therefore I don’t accept the clearance as I don’t want to put my licence on the line. If we have to miss a bit of the survey out it’s not my problem – ‘I’m just the pilot!’

So my questions are therefore:

Do others agree that it is (potentially) a contravention of rule 5?
Do others happily accept this clearance?
Would I do better using the expression 600ft MSD? (and would the military accept this from a civvy aircraft)

As this seems to be a military expression can someone confirm the exact definition of Minimum Separation Distance? Does it mean ‘I am flying no closer than 600ft from any object and am not authorised to fly any closer’? If so then perhaps this would be a better statement when making the initial RT call.

[Hummingfrog]

Why hasn't your company got an exemption from the CAA to:-

"fly closer than 500ft to any person, vessel,vehicle or structure whilst flying over Great Britain for the purpose of photographic or geophysical survey".

The company I work for has this and has to follow various restrictions such as informing the police and recording the times of such low flying along with CANP iaw the UK Air Pilot ENR 1.10 - Flight planning.

You wouldn't then have to worry about what clearance a Mil Unit gives you.

HF

[Bravo73]

Originally Posted by Hummingfrog

Why hasn't your company got an exemption from the CAA

Because I suspect that his company is carrying out surveys but without adhering to the various requirements if operating <500ft (ie helmets, TCAS, etc etc IIRC).

I could be wrong, of course...

[212man]

Crab, what maths are we talking about? You look at the approach plate, it says DA or MDA 430 ft (or whatever), and that's what you fly to. You don't add the DH/MDH to the airfield elevation to derive the DA/MDA.

[[email protected]]

212 - see HEDPs post. At cloudbreak on mimimas using QFE you know that a 150' DH on PAR means the runway centreline is 150' beneath you - with a QNH approach you have to subtract the elevation from the DH to know how much space below the cloud you have. It also means that METARS (based on airfield elevation) are directly relevant to your DH/MDH when looking for diversions.

Nick - I can't see how writing 3 pieces of information on a kneeboard is easier than adjusting one knob on an altimeter - I'm sure the Human Factors guys would have a field day with that one

Cyclically - don't bother asking for a MSD clearance, it doesn't exist. My question for you is - when outside the MATZ and operating on QNH are you using a rad alt to determine your height agl? If you are using altitude on QNH compared to ground elevations on the map then you are still very likely to go below 500' agl unless you add a healthy margin. My answer to your original question is still - look at the map and ask for a suitable clearance through the MATZ based on QFE that will keep you above your 500' agl. Alternatively give the unit a ring before you launch and tell them what you want to do to see if they can suggest a suitable clearance height.

[Jumbo Driver]

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) ...
...
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:

1. Yes, absolutely
2. 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

[Arm out the window]

Apologies if this doesn't apply in the UK, but the low flying regs in Australia have a clause saying something along the lines of, you're not illegally low flying if it's because of the inevitable stress of weather or compliance with an air traffic control clearance.
Our company have some low flying approvals but we don't do it willy nilly, only if it's required and doing things approved on the AOC. However, most of our flying around the local control zone is at 500 ft on QNH. That's usually the clearance, but I've been instructed sometimes to 'commence descent early to the pad' for example, and as long as I'm satisfied it's not a safety hazard, I'm happy to comply.
Do you guys not have a similar rule?

[Brain Potter]

crab,

I too am a UK military pilot that was brought up on QFE and I was undergoing flying training when we went over to QNH for a short time. I remember thinking that sense had prevailed when we reverted to QFE. However, after many years of flying around the world I am now strongly in favour of adoption of QNH for the following reasons:

1. Standardization. Just about everywhere else in the world uses QNH, including the majority of aviation in our own country. During the cold war we operated almost exclusively in UK mil environment, but nowadays deployed ops are our raison d'etre and virtually every fleet is undertaking QNH-based ops somewhere around the world. Interoperability is improved by adopting worldwide practices.

2. Training. As we have to adapt to QNH on ops - why even create a difficulty by having a different practice at home. Train as you fight?

3. Terrain awareness. Having QFE set whilst being vectored on an instrument approach removes a lot of terrain awareness from the cockpit. Yes, you know how high you are above the airfield, but its much harder to build awareness of separation from the surrounding terrain. In practice, this puts the onus for terrain avoidance totally on to the controller. The relationship between the approach minimum and height above the runway is quite easily read from the plate, but I suggest it is much harder to mentally calculate that 2000 feet QFE is safe separation from terrain which is higher than the airfield. I believe that use of QFE creates pilots who are culturally trained to place a great deal of trust in ATC not to fly them into a hill. Perhaps that's fine in RAF Lincolnshire, but what about in Kabul or even at Nellis? CFIT happens when aircraft fly into hillsides, not when they fly into runway thresholds. Which pressure setting is better near mountains?

4. Combined zone pressure settings. It is utter nonsense that aircraft land at Kinloss on the Lossiemouth QFE, whereas a zone QNH would be entirely reasonable.

I can see the logic of the arguments for QFE and historically, in the isolation of ops from our own airfields in UK/Germany, it worked. However, with smaller but more deployed forces I think it is time to wake-up and realise that we swimming against the tide. The transition will be painful for those fleets that don't deploy and for mil ATC - but an expeditionary force really should not be so parochial.

To address the original question. Most military aircraft can accept a 500 foot clearance as they are not subject to the ANO. The military controller is trained to apply military rules and may not have knowledge of regulations contained within the ANO.

[Gaseous]

inevitably such a clearance as "not above 500ft" must put you in contravention of that Rule

Surely it depends on the terrain. There are plenty of places where it is possible to fly at less than 500ftAGL without infringing rule 5. It is not inevitable rule 5 will be infringed by accepting such a clearance.

[Max_Chat]

As I understand it you don't need a clearance to transit a MATZ, therefor telling ATC that you intend to be at 600' agl should suffice as long as you are outside the ATZ, and they should be happy to accept what you are doing and deal with it.

Is the 500' rule negated if instructed, by ATC, to fly lower?

[Gaseous]

Is the 500' rule negated if instructed, by ATC, to fly lower?

No. The pilot must comply.
Your suggested method of crossing a matz wont make you popular if it is full of fast jets.

[HEDP]

Interestingly the Apache requires to operate on QNH for targetting but I still prefer to operate on QFE for landing and take-off.

One other thing that has been mentioned is the added requirement to change an altimeter pressure setting as a point of distraction; this is a slight red herring as you have to change from RPS to another setting anyway whether it be QFE or QNH.

As intimated earlier there is much more 'heads in' checking of altitudes to be flown under the QNH system as opposed to the ease of QFE practices. Again the terrain clearance issue is negated by procedure.

On deployed operations, most of the time, UK forces will be operating with UK military air traffic so issues are negated. That said it is not a problem to operate on QNH with other nationalities air traffic, just more heads in at the plates and detracting from lookout, IMHO.

The point about a common QFE at Kinloss/Lossie is another red herring as either way it would be a common QFE or QNH and height errors at the non manster airfield would still be evident for landing and take-off. The common QFE is to facilitate seperation between traffic on different frequencies in close proximity to each other. Incidentally the height errors are negligible as they are both near sea level.

It worries me greatly that anyone one would advocate disregarding either the MATZ in toto or indeed ATC request/direction within a MATZ. A height allocated by mutual consent is far better than to insist that you will do things at your height and air traffic 'be damned'. Military traffic can be of a vast variety of types and in the event that the airfield in question was dealing with an emergency for example, how would you as an aircraft captain feel if you were instructed to go around with an emergency because another aircraft insisted they were going to erode the seperation criteria required for a safe approach?

As for the below 500 feet rule, would the same question be valid for the Heathrow routes that require you to be not above 800 feet when over what I would assess to be a congested area? Does the same principle apply?

The same rules apply to a military helo that has not been authorised to low fly in any event, the question does not lie entirely in the civil arena. If not authorised to low fly would I comply with the instruction, sure I would if my risk assesment led me to believe that it was safer to comply with the air traffic instruction. This doesn't however answer the underlying question of whether it is legal or not, that I dont profess to know............

[Brain Potter]

HEDP,

I speak as a pilot of large jets, so please forgive my perspective as I very rarely operate VFR.

I don't understand what you mean by saying that there is more heads-in checking of plates when operating on QNH. The cleared altitudes are flown and the procedure followed until visual or at DA. The only extra work is to make a mental note of the airfield elevation at briefing stage - so that correct height for range judgement can be made once visual. In return for that one calculation you can have a warm feeling of knowing exactly how high you are above the terrain whilst IMC. Having experienced some appalling ATC around the world I am glad that they were not using QFE - which would have left me with a much more difficult task of trying to maintain awareness of "I'm that high above the airfield, so where does that put me relative to the mountain". Hence I am not quite so trusting of terrain clearance being left to correct procedural interpretation by a person on the ground. Perhaps your different view comes from VFR ops, where you are usually in sight of the ground?

In my experience UK deployed ops take place on QNH in accordance with host nation AIP. Even where we provide the ATC we usually share the airfield with the Americans and our own charter flights, both of which will operate on QNH. Traffic on different pressure settings always seems like a bad idea.

I disagree that Kinloss/Lossie is a red herring. There are many TMAs/CTZs in the world that serve multiple airports in close proximity and operate a common altimeter/QNH. The barometric pressure in the zone will be the same, and the precise pressure at each TDZ is not required and the differences in elevation are taken care of by having discrete DAs. There are no height errors as everybody is using altitude. Take the case of parallel runways - either you have a seperate QFE for each runway or operate on the same QNH with different DAs - each of which give the required OCH. Kinloss clutch procedures are based on Lossiemouth QFE, so an aircraft at DH at Kinloss is referencing the precise pressure at a TDZ several miles away! Yes, these procedures are workable, but the degree of reverse-engineering required highlights the anachronistic nature of QFE ops - why not just use QNH like the rest of the world?

The UK military operates several ATC procedures that are at odds with worldwide practice. Each can be justified on an individual basis, but net consequence is an unnecessary lack-of-commonality which, in my view, actually reduces the safety margins. As we concentrate our remaining forces on fewer bases the number of MATZ has been reduced, but traffic around those that remain has increased. Perhaps it's time to make a case for giving the bigger bases proper Class D CTZs? Transiting civilian traffic could not then ignore the airspace. In return the military could offer to standardize it's practices with ICAO/JAR to allow civilian traffic to use these zones more comfortably.

[HEDP]

Brian,

My 1st post was certainly refering to VFR operations where on three close airfields with differing elevations you had to be aware of different altitudes for crosswind, base leg and downwind as well as arrival and departure altitudes. This meant at least 8 different altitudes had to be at hand to fly in three different circuits. Most certainly more reference required to heads down info rather than eyes out in the circuit. A difference to IFR operations I admit.

It seems we have differing experience of deployed ops, for example an AT location may adhere to host nation procedures but Tac ATC in more austere locations work on QFE. A difference in requirement and situations guess.

You miss my point about the Kinloss/Lossie red herring. Whether QFE or QNH it will be the pressure reference of the master airfield therefore regardless of setting, it will be from an airfield some distance from the other. In this instance whatever is used there may be an innacurracy by virtue of the distance and therefore pressure differential whether common QFE or QNH. It was your comment that it utter nonsense to have a common QFE but your subsequent post counteracts that line by stating that a common QNH would be better. The same innacuracy would be present in either.

[purge98]

If you are worried about a foot or two then at what point in the aircraft the actual static pressure is detected by the altimeter is important.
Is it at the entrance to the static vent on the side of the fuselage or at the actual instrument?
You may find that you are even lower than you think you are if the instrument is 5 feet above the bottom of the fuselage and the pressure is detected at the instrument
I'll get my coat...

[Brain Potter]

As you say, different perspectives relative to IFR or VFR ops - although I suspect if you'd been taught to fly anywhere else but the UK then you would find QNH more natural. I see your point about the differing altitudes at 3 close airfields. However, remembering varying VFR pattern altitudes is another one of those airmanship-type things that the UK QFE system does not equip people for. Instead it engenders a "visual circuit = 1000 feet" (or whatever) pavlovian reponse. Which is all very well in the UK but, like it or not, the rest of the world aren't going to change and we are not doing ourselves any favours by training obscure practices into our youngsters - even if the underlying logic is sound.

You are not convincing me about clutch pressures.

A QFE is relevant to a specific runway - so that the altimeter reads zero at touchdown on that runway. A different runway, even at the same field, will have a different QFE unless the TDZE is identical. Some countries allow QFE inside the final approach fix - for example Paris De Gaulle offers 4 QFEs for the parallel runways.

Conversely, QNH is relevant to the whole airfield and the differences in runway elevations are accounted for by publishing different DAs and TDZEs for each runway. The pattern, approaches and missed approaches to the different runways are all flown on the same pressure setting and are thus coherent. A zone QNH is equally valid at all airfields in the zone, provided that barometric pressure does not change markedly over a few miles (not likely) and if it did the zone would adopt the lower QNH.

A zone QFE is not really a valid because, the altimeter only reads height above the TDZ of one particular runway within the zone. Aircraft flying to other fields/runways are not landing on QFE, they are landing on a pressure setting that gives neither height nor altitude. The special procedures that are published for Kinloss/Lossie are a case of bending conventional procedures and definitions to fit in with the Brit Mil QFE policy. I have not seen this practice anywhere else in the world.

Perhaps I should get back to plank forums?

[Presstransdown]

Cyclically

Yes you will be in contravention of rule 5
You do not accept the clearance.

You certainly do not need to accept the clearance in a MATZ

Do not let yourself be talked into illegaly flying. You are the Pilot in command, not under command.

As an aside we have a dispensation to rule 5 (and a few others) but I never use it unless I need to.

If a young person gets tipped off a horse and gets paralysed(Ive been to one or two) and daddy has a few horses and a lot of money then he will screw you to the wall in a civil court if he thinks you are responsible.

Your feet wont touch the ground.

The CAA or anybody else do not have to become involved at all.

You will have to hire a lawyer.

Regards

P

[[email protected]]

Max Chat - I think I see what you are getting at in that non-mil aircraft theoretically only have to recognise the standard 2nm/2000' ATZ part of a MATZ - however you will look v stupid flying inside the MATZ boundary without clearance if you have an airprox and anyway it's just bad airmanship to ignore airspace restrictions.

One of the reasons Mil controllers use the not above 500' QFE is that if we (the mil) are operating in accordance with ATC instructions, we are not illegally low flying - a similar dispensation does not appear to exist in the ANO for civ traffic.

Clutch QFEs are for deconflicting circuit and transit traffic, not for giving neat zeros on the altimeter for touchdown.

Strangely enough the military can manage to use QFE at mil airfields and then magically switch to use QNH at civvy airfields without disaster or confusion - most of us do it all the time so we are hardly unversed in the ways of the world outside. Many of us just prefer QFE to QNH as it does give standard heights for standard procedures and is one thing less to think about.

The NATO standard helicopter join used to be 500' QFE at right angles to the active runway so it wasn't just UK being difficult....people will be moaning about why the US still uses inches of mercury for pressure settings instead of millibars or hectopascals next.

[Bertie Thruster]

Presstransdown. I didn't know UK CIV SAR had a 5. 2. b. permission!

The CAA will not issue any UK HEMS operator with a written permission to not follow the "500ft rule".