Bicester Aviation Services

FAQs on GPS Systems and Flight Recorders

1.   I have heard that the IGC Approval of my Cambridge Flight Recorder is shortly to be downgraded.   What impact is this likely to have on using it to validate Badge flights?

The first flight recorders were designed during the mid 1990's and conformed to the security standards then prevailing.   These recorders could be used to validate all IGC flights, including World records.   During the last five years, the security standards have been increased, predominantly by requiring a security system based on a RSA or asymmetrical algorithm.   While all the recorders designed and marketed during the last five years comply, certain early models have a symmetrical security algorithm and/or problems with the mechanical security micro switch.

The recorders specifically mentioned as likely to be downgraded include the Print Technik GR1000, Peschges VP8, early models of the Filser LX20, Zander 940, and the Cambridge GPS10, GPS20 and GPS25.   The proposal submitted to IGC by GFAC is that these recorders be downgraded by having their suitability as evidence for World Records removed, however they would remain fully acceptable for all other flights, which would include FAI Badge flights, Diplomas and National records.   As very few of us attempt World Records, this is likely to have little impact on the majority of the gliding movement.  

However, the IGC Bureau have announced that:

• The Cambridge GPS10, 20 and 25, and the Zander 940 recorders are downgraded from All Flights to the FAI Badges and Diplomas level on 1st October 2005.

• The early models of the LX20 and the Peschges VP8 are downgraded from All Flights to FAI Badges and Diplomas on 1st October 2004
• The Print Technik GR1000 is downgraded from All Flights to FAI Badges and Diplomas on 1st October 2004.   However, it is possible to have your existing GR1000 modified by the Manufacturer so that it can remain at the All Flights level.

2.  Why does my EW flight recorder not include the map datum setting in the IGC record?

The EW recorder is unique in that it uses data from an external GPS, adds a barometric height and writes the record into the IGC file.   IGC mandates that the GPS map datum setting must also be written into the IGC file.   Unlike recorders with integral GPS engines, the EW has to obtain this information from one of the NMEA sentences transmitted by the GPS.   The only GPS receivers that transmit this datum information are the later Garmin models and consequently, these are the only GPS receivers that can be used with the EW to produce a valid IGC file.

3.   I have a Garmin III Pilot but when looking at the Airspace, I cannot see any Airways.   Why?

The airspace data for all Garmins is provided for Garmin by Jeppesen.   Jeppesen do not recognize any airways in their airspace data and hence they are not shown.   I have never been able to get a satisfactory answer as to why not, but I suspect that it is because in continental Europe there are no airways below FL110 and therefore Jeppesen have assumed that UK follows the continental European pattern.

4.   Can you explain how UK airspace is entered and updated in Glide Navigator II, See You and See You Mobile?

Glide Navigator imports airspace from the Tim Newport-Peace .air files.   These are published each year by Tim and published on the BGA website.   They can also be found in John Leibacher's World Soaring Turn Point Exchange.  

See you and See You Mobile use TP files which are compiled specifically for the See You and LX Navigation products.   These files have a .cub extension (See You binary) and can be found on both the See You and LX Navigation web sites.   Alternatively, they can be compiled using a compiler, LX Airspace Browser.   This free program compiles airspace from a variety of formats including the Tim Newport Peace version and the  DAFIF format.   Both these formats are ASCI text formats and can, if required, be easily modified with a simple word processor before compilation.

5.   Why does my IGC approved flight recorder have two serial numbers?

When the International Gliding Commission (IGC) created the standards for approved flight recorders, they decreed that the serial numbers would be a trigraph consisting of three alpha numeric characters using the numbers 0 to 9 and the letters A to Z. These three character alpha numeric serial numbers are mathematically described as 'base 36' numbers, and use the digits 0 to 9, with 10 represented as 'A', 11 as 'B' etc to 35 represented as 'Z'. They can be converted to an equivalent base 10 number which only uses the characters 0 to 9, and which we all recognize. This means that every IGC approved flight recorder will have both an alpha numeric base 36 three character serial number, as well as an equivalent base 10 numeric serial number. Flight recorders manufactured by Cambridge and Volkslogger were all assigned a base 36 three character serial number when built. However, the early recorders made by Filser, EW and LX Navigation carried the base 10 serial number. This is converted to a base 36 number when the IGC file is downloaded. For example, a LX Colibri may be designated with a base 10 serial number of 15657. This is equivalent to a base 36 serial number C2X.  In the fullness of time, all base 10 serial numbers will be displayed as base 36 three character serial numbers.  In passing, it should be noted that a flight recorder can have a base 36 number comprised of all numeric characters.  For example a Cambridge recorder might carry the S/No 535.  This is a base 36 number and equates to a base 10 S/No of 6593.  Still confused?  

The .IGC files that are generated by an IGC approved flight recorder will always have a file name of xxxxxxxx.IGC where the 'x' are decoded as follows:

The first character represents the last digit of the year the flight was made.  For a flight made in 2005 (or 1995) this digit will be 5.

The second character represents the month of the flight.  1 to 9 denote Jan to Sep respectively, while Oct is denoted by 'A', Nov by 'B' and Dec by 'C'.

The third character represents the day of the month.  1 to 9 denote the first 9 days of the month, while the 10th is denoted by 'A', the 11th by 'B' and so on, until the 31st which is denoted by 'V'.

The fourth character is a single letter denoting the manufacturer of the flight recorder.  'A' denotes Garrecht (Volkslogger), 'C' Cambridge, 'E' EW Avionics, 'F' Filser, 'L' LX Navigation, 'P' Peschges and so on.

The fifth, sixth and seventh characters is the base 36 alpha numeric serial number of the flight recorder.

The eighth digit represents the number of the flight on any day