Bicester Aviation Services
IGC Approved Secure Flight Recorders - Part 3
In this part I am continuing a review of the available flight recorders with an evaluation of the the Garrecht Volkslogger and the Cambridge GPS/NAV system.
SFR 1 - Introduction to SFRs
This Page - SFR 3 - Volkslogger and Cambridge GPS/NAV
This Page - SFR 3 - Volkslogger and Cambridge GPS/NAV
The Volkslogger is a solid unit housed in a rectangular robust, metal case some 100 x 50 x 54mm (4" x 2" x 2 1/4") and weighs approximately 320 gms (11 1/4 ozs). A 2 line, 16 character LCD is mounted flush with the 100 x 50mm face, together with 3 unmarked buttons. There is a circular electrical connector on one end (later models have a 8 way RJ12 connector), while a flat plate GPS antenna is mounted on the top. An alternative model is available which has a remote antenna coupled by a co-axial cable to a BNC socket on the box. Provision for mounting the box to the glider is by three threaded 5mm bushings similar to, but not compatible with, a camera mounting screw. It has no internal power capability and relies for its operation on being connected to an external battery between 9.5 and 24 volts which is connected via the 5 pin connector. Electrical consumption is some 125 mA. There is no fuse fitted or supplied although it is recommended that an external 500mA fuse is fitted. No On/Off switch is fitted, the FR powering up immediately it is connected to the external power supply. A pressure altitude sensor is fitted which is specified as capable of recording up 20000m (64,000ft), although the supplied calibration certificate only goes to 11000m (36,000 ft).
Once power is connected, the FR initialises itself and will lock on to satellites and start recording without any pilot input. The number of satellites in the received constellation is shown on the LCD together with an indication that the recorder is operating. In this mode, it can operate as a blind' FR but as there is neither means to connect a remote indicator or LED showing correct operation nor a remote operated PEV or fast fix button, the unit is best mounted accessible to the pilot with the LCD screen in his view.
The FR is capable of holding some 500 turn points in its data base and an electronic task declaration can be made. The turn point observation zone (OZ) can be set to a cylinder or the FAI photo sector. These functions, together with the navigation feature, are programmed by means of the three buttons. The buttons are unlabelled and have different functions in different screens. Once the pilot becomes used to their varied functions, there is no problem although the system does not lend itself to club environment where many pilots use the unit without necessarily having the time to become familiar with its operation.
The navigation display, which is clear and very readable, is comprehensive bearing in mind that it is only capable of displaying 2 lines of 16 alpha/numeric characters and symbols. The normal recording rate can be programmed between 1 and 60 secs. A fast fixing rate is pre-set at 1 sec and is activated when within the designated OZ or when the event marker is operated. Although the fast fix rate cannot be altered, the number of fixes recorded when it is activated can be programmed. An audio tone can be set to sound when fast fixing is operated or when the glider enters the OZ. The total memory capacity is some 20 hours at a 10 sec interval and this is reduced if fast fixing is frequently activated. The amount of free memory can be displayed and it is important that this is managed correctly as when the available memory is full, the unit stops recording; there is no automatic memory roll over to delete previous flights. This feature could be a problem in a club environment where pilots are likely to be less familiar with the unit's features.
A programmable NMEA output is available from the 5 way connector to operate a vario system or PDA. A PC cable, power supply and software are supplied to transfer the data to a PC at the end of the flight.
Early models did not have any engine operation recording capability but later models are fitted with a microphone to record engine noise level (ENL) when used in a turbo or motor glider.
The Volkslogger is a well engineered IGC FR. The memory must be managed correctly as it stops recording when its memory is full and does not roll over giving auto deletion of previous flights. The three unmarked buttons have many diverse functions requiring that the pilot is familiar with its operation if all its features are to be operated easily during flight. The lack of a remote event/fast fixing button together with no remote indication of correct logging mean that the unit has to be mounted both within the pilots visual and tactile range. On the plus side, it is robust unit which works well with a clear, bright, readable display.
The Cambridge GPS/NAVThe Cambridge system had the disadvantage of being the first in the field and while it has tended to set the standard for the design of later units, it was unable to benefit from later cost cutting features. The first Cambridge unit, the GPS/NAV Model 10 was a large, heavy unit with an integral battery which is coupled to a small, lightweight, well engineered flight data display. The Model 10 was introduced in 1994 and was used exclusively in the 1995 World Gliding Championships in Omarama, New Zealand. It is no longer in production having been replaced by the Model 20 and 25. These later models are rectangular boxes about the size of a miniature camera and measure some 113 x 67 x 50mm (4 1/2" x 2 5/8" x 2") with a weight of 330 gms (11 ozs). The Model 20 has an integral antenna on the top while the Model 25 is configured for a remote antenna. Both models require external power between 11 and 16 volts and have a consumption of 135 mA. On one end there are 3 RJ11 telephone type connectors which supply the power, connect to the display unit and feed data to the variometer system. While it is optimised to feed nav data to the Cambridge SNAV and LNAV, other variometer systems requiring standard NMEA data, icluding a PDA, can be connected. Adjacent to these connectors is a standard 9 pin D' plug which is the dataport for connecting the unit to a PC. A green LED on the top of the unit flashes when the unit is locked onto the satellites and is recording. Both units have a two standard camera mount threaded sockets to assist in mounting in the cockpit.
A small, thin, 57mm (2 1/4") cockpit LCD navigational indicator is available which is coupled by data cable to the FR. This unit is light and is easily mounted on the coaming or canopy rail. The custom LCD is very readable in all lights and is optimised to provide a GPS navigational display for gliding use. Around the display are 6 labelled buttons that provide a logical interface to the FR allowing all the features to be accessed and programmed from the LCD unit.
All models will hold 250 pre-programmed turn points and 10 tasks. The turn points and tasks can be programmed from either the display unit or the supplied PC programme, while any one of the 10 tasks may be selected and electronically declared. When a task has been declared, then the fixing rate increases within a specified radius from the turnpoint and an audio indication is given that the OZ has been penetrated. However, the OZ can only be selected to a cylinder of programmable radius; a FAI photo sector is not an option. The FR memory will store 25 hours of recording at a 10 second logging interval and when full, overwrites earlier flights as necessary. A pilot event marker (PEV) and fast fixing has recently been introduced and allows for 20 fixes at a programmable rate.
All Cambridge units contain a microphone based engine noise recorder that operates automatically. The resultant trace can be analysed on the supplied software to show a noise signature trace from which it is easy to identify whether the engine has been operated. The barogram operates to 11,000m (36,000 ft) and a calibration certificate is supplied with each unit
The Cambridge units are capable of being used without the display as a stand alone 'blind' recorder. While a fast logging and PEV push button can be connected in place of the display unit, a flight cannot be declared and therefore there is no audio or other indication that the OZ has been penetrated. A further disadvantage of using the basic recorder without the display is that a 'GOTO' waypoint cannot be selected. This is only a problem when interfaced to an LNAV.
In summary, the Cambridge GPS/NAV units when used with the optional LC navigational display, presents a well engineered, practical FR that is rich in desirable features. The noise operated engine running detection feature is one of the best available. It is also the only FR which is supplied with an effective PC analysis programme. The only criticism is that it cannot cope with a FAI photo sector OZ; there only being provision for a cylindrical OZ.
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