Currently, last minute aeronautical information update means “NOTAM”. Created 60 years ago, it is based on text messages, which are intended to convey to pilots and other “airman” information that is critical for the safety of the flight. Yet today the NOTAM system is increasingly used for information that is not safety critical, but which could affect the efficiency of the flight.
It is clear that the current NOTAM messages and similar text messages, containing safety critical information, cannot satisfy the future ATM system. The NOTAM system is constrained by a number of aspects that are related to its history, as visible in the NOTAM samples included beside.
Human Interpretation required
The ATM system is increasingly relying on automated systems at all levels, which depend on correct and up-to-date information in order to perform their functions. However, the content of a database, be it on-board, at the airport or in an ATC system, may be ‘superseded by NOTAM’. The task of remembering which information is overridden becomes the pilot’s or controller’s burden. There is a risk that safety critical, last minute information remains outside the automated data processing chains and in consequence missed by some or all the actors involved.
The current system is driven by manual processes to ensure NOTAM accuracy and provide a way for humans to correct NOTAM entry errors. The system relies heavily on post-submission quality control.
Although supposed to be human readable, there are frequent complains from pilots, especially from general aviation, that NOTAM text is frequently hard if not impossible to decipher for the non-expert. The recent Airspace Infringement Workshop held in EUROCONTROL refers.
The current concept of issuing safety critical information as free text is also inefficient, as it requires human reading and interpretation before being fed into the automated systems. It’s the same piece of text that is read by many recipients, who all do the same: read it, interpret it and input it in the database. This can significantly slow down the information flow. It can also trigger misunderstandings, as shown by frequent discussions on AIS Agora (the on-line forum for AIS professionals), that ask for clarification with regard to the exact meaning of the words used in NOTAM.
Information is becoming more dynamic and the number of NOTAM published is increasing. According to statistical information 2000 and 2006 from the European AIS Database (EAD), the number of NOTAM issued have increased by 70% in Europe and by 65% world-wide, as presented in the table at the right.
Today 20,000 NOTAM (on average) are currently in force world-wide. Many of these are given to flight crews for pre-flight briefing resulting in Pre-flight Information Bulletin (PIB) in the range of 10-50 pages for an internal European flight.
Due to the current limited information filtering capabilities of the text NOTAM format, between 40% and sometimes up to 90% of the information given in PIB has no direct impact on the flight for which it was provided giving rise to the statement:
"...most information given in flight paperwork is user hostile.",
Captain “Rocky” Stone, Chief Technical Pilot, United Airlines, AIM Congress 2007
Yet the probability of pilots not being aware of important and pertinent NOTAM is increasing. Due to the complexity of airspace, databases, and publishing errors, there is a tendency to use the NOTAM system as a correctional medium overwhelming the users with data which actually degrades safety.
Geographical and temporal inaccuracies
By its nature, aeronautical information is geographically related and even of geometrical expression (airport surfaces, routes, airspace, etc.). The part of the NOTAM message that can today be interpreted automatically is limited to “position and radius of influence”. This seriously undermines the efforts to present the NOTAM information graphically.
Knowing the information filtering limitations and to be on the safe side, the NOTAM originators tend to overestimate the radius of influence, which causes the NOTAM to be included in briefings for flights that are totally outside the really impacted area.
NOTAM can also contain applicability schedules such as TSA active “APR 14 1200-1250 1300-1350 2000-2050, 15 1200-1250 2000-2150, 16 0800-0850 0900-0950 1200-1250…”. Hard to read and sometimes even ambiguous, such schedules require human reading skills which are not within the capabilities of automated systems. Even more, the temporal information is not always presented in the NOTAM D field. Sometimes, supplementary applicability information is provided in the free text description, which makes the interpretation even more difficult.