Summary

Aviation Weather Information is and has been critical for the advances in flight safety. However, there is room for improvement, not the least due to technological advances. This paper explores areas where measurement, forecasting and distribution of aviation weather information could be improved, and new policy is proposed.

Introduction

1.1 Aviation Weather Information and Products have contributed critically to the development of ever higher safety levels in aviation. This was realized mainly by supporting the decision-making process of flight crews and controllers, improving flight- and fuel planning and also enabling regulatory & procedural guidelines, e.g. for approach procedures.

1.2 Traditional products such as METAR, TAF & AIRMET/SIGMET are coded in a way that was technologically relevant during the growth of aviation. In the form of TELEX/AFTN style, highly compressed and coded text strings that save on storage space, processing power and network bandwidth, all of which was precious at the time.

1.3 Historically, there has always been a situation that the most encompassing weather briefing package was available to crews before departure and the crews then tried to update as well as they could through different technological means or flight information service while the flight progressed. ATS in that sense mostly played the role of relay station / flight information service provider.

1.4 As Developments in IFR Procedures and Equipment ever lowered the minimum weather requirements for flights and traffic density increased, the network/operations impact of weather became ever more the focus for ATS, not so much weather information for individual flights.

1.5 Technological advancements in general and ATM modernization programs like SESAR and NextGen in particular require a reevaluation of needs and technologies in regards to weather data. Also, setting the right priorities in meteorological research and progress in forecasting and nowcasting for the needs of the aviation community is required.

1.6 Due to several events and incidents in recent years, the topic of volcanic ash reports and forecasts has risen in importance. So has the question of associated liabilities and responsibilities.

Discussion

2.1 Aviation Weather Data and Reports

2.1.1 The European Cockpit Association (ECA) published their vision on aviation weather in April 2014, which provides excellent background and outlook on the subject. Although written from a pilot’s perspective, it largely applies to controllers and ATM as well.

2.1.2 In a nutshell, ECA is promoting the following key messages relevant to weather information:

• Deliver relevant aviation weather information into the pilots’ hands. Do not simply store or “hide” information in computers;
• Ensure that ATC/ATM works with relevant aviation weather information across borders in a coordinated way;
• Build an aviation meteorology portal for Europe such as www.aviationweather.gov;
• Halve the time between TAF from 6 hrs to 3 hrs in Europe.

2.1.3 As a starter, there should be a refocus by the MET community on the various end users needs. Transport Category Airplane Crews, ATCOs/Supervisors in ATM and pilots in light aviation all have slightly different needs. Over the years, the types of operation between Airliner types (commercial, IFR incl. LVP, two-man cockpit, highly equipped incl. weather radar and flight into known icing certification, but also under commercial pressures and regularly operating in and around adverse weather) and light airplane recreational flying (typically VFR, single pilot, limited performance and equipment, no anti-ice or weather radar) have further grown apart.

2.1.4 As more advanced technical channels are available nowadays while bandwidth and storage space have become a lot cheaper, the desire by pilots and controllers for more easily interpretable graphical weather products, should be easier to meet. Obviously, such uncodified graphical products are not suited for transmission via RT by ATS/FIS.

2.1.5 For ATS, MET in the past was mainly about flight information service and keeping all flights updated. As significant numbers of airspace users now use alternate means to get weather information and traffic has become ever more dense, the attention has mostly shifted to network and capacity effects, arrival rates, runway-in-use selection, operating concepts, etc.

2.1.6 For operational users like ATCOs, FIS personnel and pilots, it is often hard to track updates and the individual differences between successive reports. Automation may aid in comparing various versions of reports. Also, if update cycles become too short, they become impossible to be processed and grasped by humans. Also, the timing of provision of this information is critical, as it could interfere with phases of high workload and higher priorities during a flight, e.g. during an approach.

2.1.7 At the same time, the willingness, ability or even mandate of ATS to provide “free” basic MET Information may provide a disincentive for some operators to equip with modern means of retrieving weather information. In particular some no-frills airlines systematically use FIS to fulfill the requirement for a current weather report for destination and alternate airports before commencing an approach.

2.1.8 Ideally, airspace users will have direct access to aviation weather products at any time both while on ground and inflight, thereby removing the need for controllers and pilots to spend time on an active control frequency relaying and checking reception of weather information.

2.1.9 ATS should be provided with the same information as is provided to pilots, as far as practicable, in order to share the same awareness regarding weather. Retrieval of this data from a common data pool would ensure commonality of information. 2.1.10 As MET data is being used extensively for flight planning, fuel planning and decision making on the airborne side and adverse weather is often the limiting factor on sector capacity, the topic and any change to it does have potential impacts on safety levels. There is safety research ongoing under the title of “resilience engineering”, trying to understand how today’s system copes with disturbances safely. Weather obviously is one of the prime disturbers and aviation weather information and associated rules and decisions are some primary means to cope with it.

2.1.10 “Nowcasting” will and should gain in priority. At least for commercial aviation, which is nowadays able to operate in almost any weather, the weather of interest happens mostly in the immediate future and during the flight. Nowcasting is defined by the World Meteorological Organization (WMO) as:

…Nowcasting comprises the detailed description of the current weather along with forecasts obtained by extrapolation for a period of 0 to 6 hours ahead. In this time range it is possible to forecast small features such as individual storms with reasonable accuracy. A forecaster using the latest radar, satellite and observational data is able to make analysis of the small-scale features present in a small area such as a city and make an accurate forecast for the following few hours…

…Extrapolating radar echoes is the mainstay of Nowcasting. This is because radar data is very detailed and picks out the size, shape, intensity, speed and direction of movement of individual storms on a practically continuous basis…

2.1.11 Related to this development, the use of ground based (Doppler) Weather Radar for situational awareness and anticipation, albeit with an inherently slight time-lag, has surged and spread among ATC units. Also, in some instances, this picture can be received through various channels either inflight or during ground breaks by pilots and is then used mainly for General Aviation/VFR operations but sometimes even by Airline pilots. Although in the latter category less so, since airliners normally have realtime onboard look-ahead doppler radar at the pilots’ disposal.

2.1.12 Yet, what these airborne radars are unable to provide to the crews is a global picture of the weather conditions further ahead of the aircraft and along the planned route, as most of these radars are based on reflectivity, thus allowing to detect only the part of humid phenomena that are immediately ahead of the aircraft (but not the parts that are behind this “first line” of weather) or to the left or right of the radar scanning range.

2.1.13 An issue that more recently has risen in attention is the forecast and reporting of volcanic ash. Along with ash clouds comes a host of other issues, from how to gain actual data, questions around thresholds for dangerous levels to concerns around unclear liabilities and responsibilities for operators, regulators and ANSP’s. Only partly a meteorological phenomenon, it is closely linked, as ash is distributed and dissipated by weather and the reporting and distribution share similar technology and channels. As seen in the wake of the eruption of Eyjafjallajökull in Iceland during spring of 2010, ash clouds can have a large scale impact on the overall air traffic system. At the same time, the safety threat and concern around responsibilities is real, as a more recent example highlights:

On February 14, 2014 an A320, operated by Jetstar Asia on the way from Perth to Jakarta, flew through ash thrown from Mt. Kelud, Indonesia. There had been a warning issued by VAAC Darwin about 2hrs before departure. The crew however did not receive any warning before getting airborne from its operations center or handling. Unfortunately, it subsequently also did not receive any warnings from either Australian or Indonesian ATC. Luckily, the aircraft was able to land in Jakarta without incident, however both engines had to be replaced.

2.1.14 MET research should specifically focus on improving operationally relevant forecasts/reports: – Fog has severe capacity impacts due to low visibility procedures. Significant capacity impacts may occur if a fog forecast is inaccurate. – Fog is a threat to less capable / equipped aircraft, which may have to hold and as a consequence may run short of fuel. Loss of alternate destination options to divert to may also occur if reports or forecasts turn out to be inaccurate. – Tailwind conditions are a significant factor in runway excursion incidents, yet wind forecasts are often low fidelity. According to an Article “Reducing Runway Landing Overruns” in “AERO 3/2012” (https://www.boeing.com/commercial/aeromagazine/articles/2012_q3/3/), a magazine published by Boeing, tailwind conditions >5kts were present in 42% of runway overruns between 2003 and 2010.

2.1.15 There are also issues with the reporting itself. As already questioned by ECA, the 6hr TAF cycle is too long for most short haul flights. This is often evidenced by frequent TAF amendments. Already, regional specialties in this respect have been implemented, such as TTF (Trend Forecast) in Australia. An extension to a METAR/SPECI, they contain 3hr forecasts that supersede the regular TAFs. Similarly, one may question whether the strictly fixed 0:20 / 0:50 minutes METAR timing interval is still best suited for purpose.

2.1.16 Other issues with reporting concern the content itself. E.g. often enough, a valid TAF or even METAR may report wind variable 4kts, when actual conditions may be >10kts. Depending on direction, this may already e.g. make a takeoff already impossible. Another example may be visible snow being reported as rain if it (scientifically correct) hits the ground in fluid state… But for all intents and purposes, this is snow to aviation! Measurements and automation are all nice and fine, however need to be properly balanced with human checks and interpretation on the MET observer side.

2.1.17 A new safety critical application of weather data emerging is related to its use in trajectory prediction and conflict detection tools in next generation ATM systems, mostly for separation purposes in the enroute phase, but also to improve AMAN functionality. This will require a new level of integrity and quality of input data. Also, trajectory based operations may be affected e.g. due to crews opting for different cruising levels than were planned due to passenger comfort in turbulence.

2.1.18 As with most automatic processing no longer validated by humans, the term “garbage-in = garbage out” applies. Obviously this is very critical both e.g. to the more strategic flight planning systems as well as to such real-time tactical safety systems.

2.1.19 The world modern airliner fleet would essentially be a network of flying weather (and even WX radar!) stations if only the potential could be harnessed. Unfortunately, there is a lack of datalink protocols / interfaces to automatically process measured weather information from airborne sources. Of special interest are wind, temperature and pressure data to feed into various ground systems. And even in cases where protocols or capabilities exist, there is a disincentive as long as the provider of the data has to pay for transmission instead of getting rewarded.

2.1.20 Work in the area of meteorological datalink is ongoing, RTCA has a special committee SC-206 currently working on “Minimum Aviation System Performance Standards (MASPS) for Aaeronautical Information / Meteorological Data Link Services”. However some of that work is only in draft state and will take a while to reach operational reality (https://www.rtca.org/content.asp?pl=108&sl=33&contentid=86). Similarly, EUROCAE WG-76 is also currently about to be reactivated, with a view to write MASPS for AIS/MET Data Link Services from a European perspective. Coordination with SC-206 will be ensured to avoid any significant divergence or contradictions.

2.2 Technology and Distribution

2.2.1 The collecting and initial formatting of the met data is still done by humans, mostly by trained weather observers. Obviously they also do use technology like measuring equipment, but that would be out of the scope of this paper.

2.2.2 There are also many AWOS (Automated Weather Observing System, U.S. acronym) in use worldwide. These are a set of measuring devices that report standard data points such as temperature or visibility. However, they do suffer from various limitations, so are generally used to augment the weather picture or monitor remote locations and not as full replacements of human observation over a wide area.

2.2.3 As to dissemination, for years, the main distribution of preflight aviation weather briefings took either place through telephone briefings, telexed/teletyped pages, manually-drawn charts by MET personnel or a little later through low resolution fax copies. How times have changed…

2.2.4 Preflight briefings containing aviation weather information are nowadays almost exclusively delivered through IP-based networks (and partly or all of it through the internet at some point). This applies to all segments of aviation, light to heavy. Backup channels, if not abandoned, are certainly not exercised. Needless to say, a widespread internet outage would also affect aviation flight operations, not just the commercial/passenger side these days.

2.2.5 The problem with internet/IP networks is, that during flight, they are hard if not impossible to access. Some aircraft do carry satellite internet or have WIFI hotspots operating via a special radio backbone and ground relays, but equipage is not (yet) widespread and expensive to operate. For light aviation, chances for access via regular cellphone links are slightly better due to altitudes and speeds involved, but technical limitations, coverage and not the least legal twilight zones regarding airborne cellular use/access make it impractical and unstable. As a follow on constraint, the requirement for dependable access to critical for safety-of-flight data makes a spotty solution unbearable. It can be expected however that significant progress in airborne connectivity will be made and this channel may become more dependable/the channel of choice in the mid-term.

2.2.6 Also, for the past approximately three decades, airliners and the commercial segment of aviation have increasingly used ACARS (Aircraft Communications Addressing and Reporting System), which was originally intended for AOC (Airline Operations Control) messages only, to request and receive the standard coded telex format weather information, digital ATIS reports, enroute winds etc… Some of the advantages are worldwide coverage, given SATCOM even over the oceans, and easy selection of reporting stations.

2.2.7 But there are disadvantages with ACARS as well. One is cost, as each message is billed to the user. Cost model and terms differ from airline to airline, but a single METAR/TAF message can be roughly estimated at $1.50. So it is only used for selectively updating preflight met briefing data and serves as a disincentive for equipage to operators that try to economize every cent. Other disadvantages and limitations are inherent with the basic design of ACARS. The highly standardized messages were neither designed to carry nor is the display and output capable to handle graphical or vectorized data. Also, latency and continuous availability can be an issue.

2.2.8 Since the legal requirements for a PIC to familiarize with weather and pertinent info before commencing a given flight/route are quite generic and fortunately do not specify format, there is a lot of innovation in this area. Especially with the advent of powerful, light and high resolution tablets and smartphones, a whole segment of applications which integrate flight planning, MET and NOTAM briefings, charts etc… is experiencing rapid growth. Provided the IP network access issue as mentioned above can be solved, this kind of interface is likely the future.

2.2.9 In the U.S. and Canada, the use of “XM Weather”, mainly but not only in the General Aviation segment emerged over roughly the past 10 years. There exist technically two different satellite radio constellations over the continent that were developed by competing XM Radio and Sirius Satellite radio in the early two-thousands. The companies have since merged into one company now called “Sirius XM”. The original product and business case consists of subscription based high quality audio broadcasts without commercials. Both systems carry >150 channels each and newer receivers can play channels from both systems. Their mainstay is in-car entertainment, with roughly 60% of new cars sold in the U.S. being equipped and with a subscription base of >24 Million customers. So, as a “spin-off“ from this radio service and in search of new customers, XM developed a special weather channel/subscription which obviously runs on the XM infrastructure and currently sells between $35 and $100/month, depending on products and coverage. The XM system currently consists of 5 satellites that operate in the S-Band of 2332.50 through 2345.00 MHz.

2.2.10 Various data receivers for XM are available, normally in the form of an external antenna/”bug” that feed some kind of display/user interface system. Many avionics, from various panel-mounted electronic flight information systems and tablet applications to Garmin handheld aviation GPS units are able to display the data provided. In the maximum subscription, the following data is provided: High Resolution (Weather) Radar, Precipitation type at surface, City Forecasts, TFR (Temporary Flight Restrictions), METAR, TAF, County Warnings, Winds aloft, Lightning, AIRMET, SIGMET, Echo Tops, Freezing Level, Severe Weather Storm Tracks, Surface Analysis Maps, Satellite Mosaic, AIREPs, PIREPs, Special Aviation Weather Watches, Turbulence, Current Icing Products, Supercooled large droplets, Special Day one convective outlook, Special Mesoscale Discussions, Visibility, Hurrican Track. All data for the U.S. and some data including Canada.

2.2.11 A new channel and threat to the XM channel mentioned above, again limited to the U.S. only is “ADS-B-in”. As an incentive to equip with ADS-B and more effectively use the vast ADS-B ground network, the so called “ADS-B in” broadcast run by the FAA operates in a very similar manner to XM, providing a lot of the same data (but not as much as XM) with one compelling argument: it’s free! The data is uplinked on the frequency of 978MHz from the ground network to UATs (universal access transceivers). There are additional limitations to e.g. the range covered by the transmitted data such as radar but otherwise, the use of the data is very much comparable to XM Weather. Ironically, “ADS-B-in” has not helped foster ADS-B equipage at all since transmission of own-ship position requires a certified GPS source, yet the thirst for ADS-B-in weather and traffic data (being retransmitted on 978) have led to a market of various portable receiver antennas feeding mainly tablet applications and again some EFIS systems. Other than initial equipage for the UAT listening device and software, there are no additional costs. Although the system handles TFR’s (Temporary Flight Restrictions / “RAreas”), it looks like further opportunities with global appeal, e.g. to broadcast nonpermanent airspace status were missed. The same applies to the lack of any aircraft-toaircraft datalink provisions or standards other than the default squitter output and content.

2.3 ICAO

2.3.1 ICAO created a Meteorological Aeronautical Requirements and Information Exchange Project Team (MARIE-PT) back in December 2011. Information has been somewhat hard to come by and from what is publicly available, the main work has been on an “ICAO manual on the digital exchange of aeronautical meteorological information”, provisionally numbered 10003. The document does not cover much new ground other than trying to specify how “old” legacy data can be formatted and transposed into the days of XML. (Extensible Markup Language), e.g. how to code geographical information etc.

2.3.2 ICAO held a large Meteorology Divisional Meeting in Montreal during July of 2014. As part of the ongoing restructuring within ICAO, it has been decided to form a MET Panel, where MARIE-PT will be integrated and which is bound to be the meteorological focal point within ICAO. Some of the tasks of the panel will be to work on evolutions of ICAO Annex 3, and writing of a new PANS-MET document (similar to the PANS-ATM or PANS-OPS documents). IFATCA should strive to place a representative on the MET Panel in this process.

2.4 WMO

2.4.1 The World Meteorological Organization also plays a role, e.g. in publishing data formats. Despite being specified already back in 2003, institutions around the world are still in the process of transitioning from GRIB 1 to GRIB 2 format, specified as GRIB FM 92-IX, described in the WMO Manual, Code 306. GRIdded Binary is the universal format for large scale historical and predicted weather data to be distributed in machine readable form. (e.g. upper wind forecasts to be fed into flight planning systems).

2.5 Existing IFATCA Policy

2.5.1 At the Bali conference, policies regarding the sources for flight information service and associated responsibilities were accepted by directors, which directly apply to the weather information tasks by ATS.

The policy remains fully valid and applicable.

Conclusions

3.1 Accurate and up-to-date aviation weather information is essential for safety of flight and ATS operations.

3.2 Shorter term, but more precise and higher quality forecasts, especially regarding fog and its dispersal, local weather phenomena, wind and thunderstorms are on the wishlist of ATS.

3.3 Information channels carrying aviation weather information for pilots become more diverse and independent of ATS. This should be supported but only with associated relief from duties and liabilities for Air Traffic Services.

3.4 More graphical and easily human interpretable products are in demand.

3.5 Quality of data fed into next generation systems is paramount, as the core separation provision and assurance function is increasingly being influenced by MET data.

3.6 Use of real-time, aircraft-derived data is valuable and underdeveloped in the current operational environment.

Recommendations

4.1  It is recommended that IFATCA policy is:

IFATCA encourages the development and use of aircraft-derived meteorological data to improve aviation weather products.

4.2  It is recommended that IFATCA policy is:

IFATCA encourages the development and distribution of graphical and easily human interpretable aviation weather products.

4.3  It is recommended that IFATCA policy is:

IFATCA encourages the evolution of the aviation weather reporting and distribution system to allow direct access to aviation weather products for airspace users.

References

ECA Pilots Vision on Weather (2014, European Cockpit Association).

Garmin GXM40 Owners Manual

MARIE-PT Website https://www.icao.int/safety/meteorology/MARIE-PT/

https://www.xmwxweather.com

https://www.wmo.int/pages/prog/amp/pwsp/Nowcasting.htm

https://www.aopa.org/-/media/Files/AOPA/Home/Flight%20Planning/flyq/0214adsb_primer.pdf