Teeterer

and the Wessex had the final low flying warning when you noticed the main wheel spinning furiously...........................:ok:

Baston

PABs (Precision Aneroid Barometers) are in every military tower I've ever worked at, though I left the mil in 2001.

They are about 10 inches across by 6 inches deep and very transportable... no need for a wooden banjo shaped object with glass!!

Anotherthing

Oh I am disappointed! No mahogany?

I am a bit biased against people who work in Control Towers as two of them nearly killed me! See threads on Mid Airs etc.......................:ok:

To get back to QFE/QNH - they both have their place properly applied by intelligent operators.

The good old PAB's are being replaced by a slightly more whizzier Vaisala jobby

As said above the British forces are very much in the minority using QFE however some parts of the opperation are very high workload such as IF approaches in a fast jet or SH. In these conditions I can see QFE being a distinct advantage, the rest of the airforce, army & navy follows the just to keep SOP at military airfields.

This may have to change as more modern aircraft come into service as QFE may well not be compatable with the aircraft systems. For this reason you cant use QFE on the Boeing 737NG as setting QFE feeds errors into the EGPWS.

The Halfway House
 

Well, I’m in for 2 penny-worth on this one:

I was an active controller (well, a SATCO anyway) during the QFE to QNH back to QFE debacle. The iteration that everyone seems to have forgotten about was that there was a period of ‘QNH for initial and intermediate approach’ and ‘QFE for the instrument final and circuit flying’, which – at that time – replicated civvie practise to a greater or lesser extent; I had to listen to Heathrow Director (the position, not the individual on these boards!) for many hrs responding to ‘localiser established’ with “x miles, QFE is XYZ millibars, contact tower, 118.2” - especially during CAT III operations.

From an ATC point of view the use of QNH simplified coordination greatly with the 2 very adjacent USAF units whose patterns integrated very closely with ours, and the scope for applying the QFE/QNH corrections in the wrong sense was obviated at a stroke; much ‘tidier’, simpler and therefore safer. Coordination with adjacent LARS units became a piece of cake and very quickly Airfield QNH (as opposed to RPS) became the usual datum for aircraft in transit below the transition altitude, which also helped with observance of the ‘set an airfield QNH when below or adjacent to a TMA’ rule.

However, even we ATCOs understood the desire of 'fast-jet' crews pointing towards the ground in East Anglian fog on a PAR or ILS to relate to their height above the threshold elevation – I’d want to do the same! Therefore, I always thought that the ‘halfway house’ was the most logical solution. However, the 2-winged master race didn’t! It was so obvious that a ‘meal’ was going to be made out of the new requirement to re-set the altimeter to QFE after establishing on the final approach track. This was so readily anticipated that I briefed my troops specifically to be circumspect on when to effect the change.

Perhaps the following undercurrents also mitigated against the policy:
As an aside, I don’t recognise what P3 Bellows is on about at all; transit or LARS tracks on the QFE just makes for more mental gymnastics (with the resulting potential for error) when coordinating with other units, whereas RPS and the SAS provided a common datum within a locale; you just wouldn’t DO it as it makes life harder! Unless the rules have changed, the only time that QFE was mandated for use with transit traffic was for MATZ crossings, in order to coordinate with circuit and final approach traffic; otherwise it was RPS or 1013.2, below or above TL, respectively.

exactly.

QFE is better for military pilots flying MIL aircrafts, as they have advanced equipment onboard and using only RAD ALT and are not using cheap pressure altimeters. again, just that simple.

Military stuff are always a step ahead, may it be aircrafts, software (they have military grade programming languages and MIL software standards), and onboard avionics equipments.

If all of us can just upgrade our pressure altimeters into rad alt then we can scrap this QNH thing altogether.

That is what I thought when I joined 5 decades ago. No longer. We go for the cheapest now or the best 25 years late.

Use rad alts and we can get rid of pressure instruments - well, ok, I see your point. But what about those operators who wish to be so very stealthly - wouldn't the emisions from a rad alt give the game away?:confused:

(sudden blinding flash - what about GPS?)

Some interesting perceptions here. Although I haven't done any military flying for three years or so, my recollection is that we used QNH for all instrument procedures, and QFE in the circuit or when it was necessary to deconflict with circuit traffic (leaving aside the MAOT on a mountain). QFE's just another usefult tool to heve in your golf bag - and I second the point about using it when you're learning to fly.

What I'm really a bit concerned about though, is that there seem to be a few people on here who don't know the difference between QNH and RPS....

Funny how fast jet pilots of all other NATO countries manage just fine on QNH.

Oh and C-N,

if you're advocating use of a radalt instead of a baralt for routing and instrument approaches I get the feeling you haven't really used a radalt. What radalt height would you put on the chart for the airways from Germany to Italy over the Alps for example?

Green Flash

Knowing the accuracy of the GPS height channel, I'd actually much rather that I and the guy coming the other way were deconflicted by cheap barometric instruments with known and bounded errors!

M609,

RAF pilots using QNH for approaches too actually.

My problem with QFE is one of traffic awareness. At the numerous mil airfields where there are adjacent civvy airfields (eg Brize/Oxford), having QNH set reduces a lot of the ballache about "if he's at 2000ft, what's he got set on his altimeter?". Clutch QFE is not a solution to this: the solution, as far as I'm concerned, is for everyone to use QNH and just realise that the ground isn't necessarily when the altimeter says 0ft.

The only exception to this is for a PAR. Even for ILSs, the rest of the world seem to manage very adequately with QNH approaches.

Flying on aerodrome QNH greatly reduces workload when it comes to coordination, situational awareness and can significantly help airspace infringements. All it requires is for people to realise that the ground isn't going to be at 0ft.

And, when one considers that most military pilot, when below 5000ft AGL can tell their height to +/-100ft just by looking at the ground features (isn't that part of the training?), I really can't understand why the RAF went back to using QFE after coming into line with the rest of the world.

Wholigan makes the best argument IMHO- QFE is a useful tool, but setting 763 mb for Addis requires a more expensive altimeter! As for QNE... it is giving me a headache sitting in a comfy chair with a cup of coffee, the thought of trying to use it while dodging thunderstorms, figuring out the circling approach (I've only ever flown it in the dark, in daylight it would probably scare me) makes me quite uncomfortable...

Mmmm, so if I instruct one pilot to maintain 5000' on his radalt, and the other 6000' on his, are they going to enjoy the constant changing of the aircrafts attitude to follow the contours of the terrain beneath ?

And when the guy at 5000' is flying 1000' below them and triggers the radalt, are they going to do a zoom climb to ensure the 6000' based on the radalt is complied with ?

QNH is primarily used for terrain clearance, but there is also a secondary and important use in providing separation from other aircraft as part of an airspace system.

Er,

Excuse me Gentlemen.

How many radalts go above 2500 ft?

GPS?

That gives the "height" above the WGS84 ellipsoid......

...and there's me thinking this stuff was always being flogged by the lowest bidder or anyone who could spell "Warton".

Haven't used one, honestly. Yet the word itself, radalt, sounds advanced and promising. Just confined to alts using aneroid at the moment.

errm, you're right, not that advanced yet. looks like only a few reaches 10,000ft for civil use. yet i've heard AN/APN133 of C130 and AN/APN232 used by F16 and C141 are hi altitude radalts covering upto 50,000'.

I know, I controlled a few of them over the last few years, so I still cannot figure why the need to be different. (But then airspace policy, procedures, following international standards and UK MOD will not feature in the same sentence too often ;) )

Put simply, a radar altimeter measures the vertical distance between an aircraft and whatever ground happens to be below the aircraft at the time. When flying over the sea or a relatively flat terrain, it is a very useful tool. However, what it generally doesn't do is (for example) tell you that there is a fekk-off great big lump of granite just in front of you that is somewhat higher than the height you happen to be right now. Although you can partially get round that problem, it still doesn't solve how you can try to maintain a constant altitude (above MSL for example) using the radalt. Early radalts also had the problem that they only measured in a plane perpendicularly below the aircraft. You can guess what happened when you put bank on or changed attitude significantly.

Just imagine flying over markedly undulating terrain and ATC want you to maintain a specific altitude so they can arrange vertical separation between you and other aircraft in the vicinity. The radar altimeter indications are going to be rushing up and down like the drawers of a lady I once knew at RAF Valley, but even faster (if that were possible). Under these circumstances a basically barometric altimeter is going to indicate pretty much steady state altitude. (Yes I know that's not entirely true, but it's good enough to illustrate this situation and explain why you wouldn't want to use radalt.)