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Altimeter settings

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Does the ATIS provide the current altimeter information?


CPDLC, ARINC, and ACRS are all digital formats for relay and dissemination of crucial flight information to include meteorological data. Altimeter settings are one such vital piece of information on which pilots rely for safe operations.
By Glenn Woodward
Contributing Writer

Consider this scenario: You are on final to land at your destination aerodrome. Let’s say it’s a small airport in Europe. It is IFR and you’re at minimums due to visibility. You are on final at 2042z talking to the control tower, having been instructed to switch by approach.

The ATIS for the airport recorded at 1945z is broadcasting an altimeter/QNH setting of 2989/1012. In the control tower, the TACMET/digital weather display shows a current altimeter/QNH of 2993/1014. You advise the tower you have the current ATIS code.

Quick survey: Show of hands from pilots who would prefer an altimeter setting for the aerodrome from ATC that is 45 min to an hour old? Or show of hands from pilots who would prefer the current altimeter setting for the aerodrome from ATC?

Let’s look at the definition of current. For the sake of context, we’ll use entry 1 in the Merriam-Webster online dictionary:

Current:
(1) Occurring in or existing at the present time.
(2) Presently elapsing.
(3) Most recent.

Current information in altimeter settings

I am an ATC instructor with 18 years of front-line military, FAA contract, and ICAO tower experience. I’ve worked in 10 very different and diverse facilities with multiple volume and complex combinations around the world, alongside controllers from 9 different countries. And while I’m no god of air traffic, I do have a few stories under my microphone.

One thing has remained constant during all my controlling adventures: I was trained to always keep pilots advised of all appropriate and current information necessary for the safe operation of their aircraft within our scope of authority and jurisdiction.

During a recent and exciting foray into the ICAO world of ATC services in Afghanistan, I was exposed to several perspectives from numerous non-FAA controllers from around the globe. One such brush with a veteran ICAO controller and certified assessor gave me reason to investigate the idea of what may be considered current information, and how that applies to altimeter settings.

Globally, air traffic control is accomplished in the English language (with exceptions) under exceptional circumstances and situations. All certified air traffic controllers are mandated to achieve and maintain, at an absolute minimum, level 4 English proficiency.

Flyers who operate in airspace outside of the US may have experienced occasions when they knew the controller was speaking – or at least trying to communicate – in English, but wasn’t quite there. In addition, some readers may have seen or read recent articles and postings on aviation publications that speak to the issue of “English” versus “aviation English” and having (or not) a strong grasp of the nuanced differences that exist in that arena.

Classes, courses, and articles abound to highlight the potential dangers of mimicking English words using minimum muscle memory with appropriate syntax, word accents, and dialects compared to understanding each word as uttered, along with the weight and value carried by its meaning and implications.

International flyers may also have experienced the thin line between hearing and understanding non-native English speaking controllers issuing ATC instructions in “English-ish.” As pointed out in the articles noted above, there is arguably a remarkable “otherness” to aviation English throughout the world such that it is worth continuing to discuss and address.

Air traffic control at AUH (Abu Dhabi, UAE). All certified controllers are mandated to achieve and maintain, at an absolute minimum, level 4 English.

Current ATIS vs current altimeter

ICAO Document Annex 11 and FAA JO Order 71110.65 both address the ATIS and altimeter setting as it is to be issued by Air Traffic Control Services (ATCS).
FAA JO 7110.65, 2–9–2, paragraph d says, ”Controllers must ensure that pilots receive the most current pertinent information.

Ask the pilot to confirm receipt of the current ATIS information if the pilot does not initially state the appropriate ATIS code. Controllers must ensure that changes to pertinent operational information are provided after the initial confirmation of ATIS information is established.”

ICAO Annex 11, chapter 4, addresses flight information service, and when and how it’s provided – the “how” being directly from meteorological sources via CPDLC, other digital means, ATIS (voice), or air traffic control officer (ATCO). “When” depends on the phase of flight, quickly changing weather conditions, or a request from the pilot.

At more and more locations, the ATIS system draws immediately and directly from meteorological sources and provides the most current data. Pre-flight briefings or pilot familiarity will determine the availability of real-time data from the destination airport ATIS, and can be trusted as appropriate.

ICAO Annex 11, 4.1.1, says, “Flight information service shall be provided to all aircraft which are likely to be affected by the information and which are:
a) provided with air traffic control service; or

b) otherwise known to the relevant air traffic services units.”

In other words, if ATCS has the information, and the aircraft is likely to be affected by the information, then it shall be communicated appropriately to that/those aircraft. One item of said information is an altimeter setting (QNH/QFE).

ICAO Annex 11, 4.3.6, provides for the situation in which the aircraft shall acknowledge receipt of the ATIS. The ATC facility shall reply, as prescribed by the ATS authority, and “provide the aircraft with the current altimeter setting.”

It goes on to say that the meteorological information shall be extracted from the local meteorological routine or special report (4.3.6.1, g).
However, just 2 paragraphs later (4.3.6.3), Annex 11 reiterates the necessity of issuing a current altimeter setting (QNH/QFE).

The runway is the reference plane for altimeter settings at airports. As barometric pressures fluctuate, pilots must be kept advised of all altimeter setting changes for safe arrival and departure operations.

What “current” actually means

Let me clarify that. ICAO Annex 11 states that ATS will provide the current altimeter setting (QNH/QFE), notwithstanding what the ATIS is broadcasting (even though it, in and of itself, is a current ATIS).

In other words, when the pilot has reported in with the correct (current) ATIS code with an altimeter setting, the responding controller must issue the current altimeter setting (QNH/QFE) from the weather display, as displayed in the facility from direct weather sensors (if it is different from what is being broadcast). That is what “current” altimeter setting means – not the altimeter setting broadcast from the current ATIS.

The problem with my former ICAO associate was that he insisted that the altimeter setting issued to aerodrome arriving aircraft be the same setting that is broadcast on the current ATIS, even though the control tower cab had a duplicate weather display tied directly to the same sensors meteo had, and it showed the same real-time data that meteo was shown.

His position was that all aircraft should have the same altimeter setting to keep them vertically separated in the class D airspace. Huh? If we were to extend his logic, then we should also have been issuing the winds from the “current” ATIS as well, and that would not work at all.

His ATC experience was predominantly area and approach control, where altimeter settings at altitude are crucial because aircraft have to have a reference point (single altimeter setting) to ensure proper vertical separation. This is where it’s very important to distinguish between English and aviation English.

What I tried to impress upon him was the fact that the aerodrome already provides a solid reference point for vertical separation – the runway – which, in most places, is fixed and is not going to fluctuate vertically, except in the event of severe earthquakes.

He had associated “current” with the “current ATIS,” ignoring the need for a “current altimeter setting” (QNH/QFE) that is available in real time.

Conclusion

It is possible that I am the one misreading the words and misinterpreting them, thus misapplying them as well. However, having asked thousands of pilots over the years, I firmly believe that the current altimeter at the airport of intended landing is the one pilots prefer as they approach the airfield. It is the correct setting, which gives them altitude information in reference to the landing runway.

Granted, many – if not most – pilots that close to terra firma will most likely be using a radar-altimeter, although the back-up barometric pressure altimeter should be at an appropriately calibrated setting.

My suggestion is this. When flying in the international arena or any unfamiliar airspace environment, ask/insist on the current altimeter setting from the sensor as it reads right then. This is especially crucial during very-low-temperature flight operations. Do not rely on the ATIS broadcast to always provide the most current information, as it pertains to the current altimeter setting that is indicative of the affecting weather.


Glenn Woodward is an air traffic controller with 18 years of tower experience in the US, UK, and Afghanistan. He is an FAA-licensed flight dispatcher as well as a veteran flightcrew member on Boeing B-52s.

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