4.7 Altitude Evidence and Control

4.7.1 Altitude evidence

Altitude data requirements may be fulfilled by any of the following measuring methods:

a. A barogram,

b. Optical measurement from the ground (e.g. a suitable height frame or theodolite),

c. Radar measurement from the ground,

d. For continuity of flight purposes only, the GNSS altitude output of a flight recorder.

4.7.2 Altitude control methods

For altitude recording other than by external measurement, a barograph or flight recorder must be carried in the glider. Any marking of the barogram during flight shall be done by remote control, not by direct access to the barograph itself. The barograph shall be placed in the glider in such a way that no part of the barograph is accessible to the pilot or passenger during the flight.

The pressure altitude recording system in a flight recorder is a barograph and must comply with other rules in the Code for barographs and their calibration. Altitude control methods for flight recorders are the same as those used for position evidence (see 4.6.4).

a. BEFORE TAKEOFF

(i) Mechanical barographs

The OO shall make an identification mark on the barogram paper/foil and then seal the barograph.

(ii) Electronic barographs

The OO shall seal the barograph and then enter a secret multi-character code into the barograph memory before flight (a second entry of this code shall be required to retrieve the stored data). This step is not required if the barograph stores continuous date and time data which cannot be altered without the fact of such alteration being automatically reported on all data printouts from
its memory after such alteration, and the OO is able to verify the date and time of the takeoff and landing of the glider on the flight concerned.

b. DURING THE FLIGHT

As soon as possible after release, the pilot of the glider should ensure that a low point is indicated on the barogram to clearly indicate the start of the soaring performance.

c. AFTER THE FLIGHT

(i) The OO shall take control of the barograph, and ensure that its seal is secure and that the barogram has the identification mark placed on it prior to takeoff. The information required in paragraph
6.1 may then be added to the chart.

(ii) For electronic barographs, an OO must either supervise the transfer or printing of data from the barograph while it is in the glider, or supervise the removal of the electronic barograph from
the glider and shall then take charge of it until the flight data is printed out. The OO then confirms that the date and time on the printout is correct and that the date and times of the altitudes and
other flight data recorded and printed out correspond to the date and times of the flight concerned, and correspond with other relevant aspects of the claimed performance.