SAFA Skysailor Magazine

34 SKY SAILOR March | April 2022 However, at present you cannot buy a handheld airband VHF radio in Australia at all – there are not any in stock. Godfrey Wenness at Manilla is an Icom dealer, and he has told us in Ops that the Icom A16 will not be available until Autumn 2022. There may be stocks of the Icom A25 before then, but these cost about double that of the A16. Good luck if you can find one somewhere online – look at the price and make sure it is AU compliant. I leave it to you to you to determine how you can fly compliantly. How long will this situation be allowed to continue for? Well, watch this space. Our COO Brett Coupland, along with representatives of other affected Recreational Aviation Organisations, is in talks with senior CASA personnel who have been made aware of the situation on the ground and the real-world implications of this change. We will keep you up to date with developments. Altimetry and airspace Now back to the wording on altimeters. In the previous version of CAO 95.8 we could not fly, “at a height in excess of 300 feet above ground level unless a serviceable altimeter which meets the standards specified in Civil Aviation Order 103.3 and set to QNH is carried in a position so as to be easily read by the pilot at all times while in flight.” The relevant section in the new Order states, “a relevant aircraft must not be flown at a height in excess of 300 feet above ground level unless serviceable equipment for measuring and dis- playing pressure altitude, that: (i) is calibrated in feet; and (ii) is accurate to within 100 feet; and (iii) has an adjustable datum scale calibrated in millibars or hPa’; is carried in a position on the aircraft so as to be easily read by the pilot at all times while in flight.” A couple of points to be raised here. First, you should by now always be carrying a vario when flying at 300ft agl or more. This has been the case for years. Secondly, your vario must have the ability to be adjusted to an area QNH (Question Nil Height) pressure reading. The QNH pressure is the regional or airfield pressure with reference to altitude above mean sea level (amsl). It is different to GPS altitude and relies on the changes in atmospheric pressure to determine altitude using a standard atmospheric model. All sectors of aviation use atmospheric pres- sure as the means of measure of altitude. The atmosphere is a very dynamic environ- ment and is in a constant state of change. It is also subject to what is called diurnal variation. This means that as the day evolves, the atmo- sphere changes correspondingly. Air pressure is one of the attributes that is subject to this type of variation in combination with broad- scale influences such as approaching weather systems and air masses of differing pressures moving over the planet’s surface. Because of this, QNH values are updated on a regular basis during the day, usually at intervals of three hours. So, it is important to update your vario’s QNH value prior to taking to the air. An authoritative, primary source for finding QNH can be found under www.bom.gov.au There are any number of apps that you can download onto your mobile devices that will tell you the current QNH values at New CAOs: VHF, Airspace and Altimetry