NOTAMs and the AFTN
Since my flight was canceled today because of the weather, I figured it would be a good time to talk about NOTAMs.
A NOTAM is a NOTice to AirMen and it lets pilots and controllers know of things that are different or out of the ordinary. Lets take a look at some of the currently active NOTAMs for Buttonville:
060015 CYKZ TORONTO/BUTTONVILLE MUNICIPAL
CYKZ PARAJUMPS 1 NM RADIUS 435230N 792730W (APRX 4 NM WNW AD)
SFC TO 6000 FT MSL 1600/2100 DLY
0602041600 TIL 0602052100
It’s pretty easy to decode this one. This NOTAM is to let pilots know that there are going to be Parajumpers jumping within a 1NM circle about 4NM west-north-west of the airport between the surface and 6000′ 4PM to 6PM Daily between Feb 4 4PM and Feb 5 6PM. Times are in UTC (so really 11am to 2pm ET).
There really is no limit to the length of a NOTAM, as seen in this one:
050351 CYKZ TORONTO/BUTTONVILLE MUNICIPAL
CYKZ TWY C CLSD NORTH OF TWY A TO THR 15 AND SOUTH OF RWY 03/21 TO
WEST SIDE OF RWY 15/33 TIL 0603312200
This one was created sometime last year, and wont expire until March 31, 2006. It says that Taxiway Charlie will be closed north of Taxiway Alpha to the threshold of runway 15. It is also closed south of runway 03/21 to the west side of runway 15/33. View image.
These are two examples of local NOTAMs. NOTAMs that are issued by the airport and affect only the airport. A recent NOTAM was issued for Edmunston telling pilots that there was a deer on the runway. A little while later, the canceling NOTAM was issued:
060028 NOTAMC 060027 CYCL BATHURST CZBF DEER IN FREEZER
I’m sure a few got a chuckle out of that one (I found that NOTAM at aviation.ca).
There are also regional NOTAMs that affect a wider area. These NOTAMs usually offer amendments to some of the publications (CFS, Maps, etc..) that haven’t been updated yet.
These notices (along with others like METARs and data between traffic controllers) are sent using the AFTN (Aeronautical Fixed Telecommunication Network). This crusty network is based on the old teletype network and as such some of the codes are cryptic (stolen from Wikipedia):
ZCZC DFA05 12032006 DD RCTPZQZX 1209 VTBBZQZX
The ZCZC stands for start of message and is geared towards torn-tape stations where the Z and C characters will punch all five holes on the tapes providing a quick check to the operator that the tape-puncher is working correctly. The NNNN similar is a familiar one hole consecutive sequence which can be quickly identified as end of message by operators.
Im sure those codes are redundant now as this information is displayed on computer screens instead of old teletype paper.
Uncfourtunately there isn’t a lot of (free) technical information about the AFTN. As far I understand the specs are located in ICAO’s Annex 10 Vol 3. This Annex is available for $291. Searching for AFTN on Google Images yielded a network diagram of an AFTN system in the Czech. This page talks more about the setup:
AFTN – two DEC Alpha 2100 computers with UNIX
The AFTN Unified Message Switch (UMS) is a Global Weather Dynamics Inc. (GWDI) product, which has been designed for two identical computers with the UNIX/V4.0D operating system. One computer works in the PRIMARY mode and the second in STANDBY mode. The computer in the PRIMARY (OPERATE) mode ensures operations, and in case of a failure of this computer, there is an automatic switchover to the standby computer.
What better way to spend a snowy/rainy day than doing research on how information is disseminated in the aeronautical world!