Microlighters

Hi Guys,

Recently I notice that when setting my altimeter before take-off, the indicated QNH is much higher than expected (typicall > 1035).

Other than this the altimeter seems to function ok. Any advice?

Tjoek

I would cross check with other aircraft operating from your field. Simple radio call. I see in Jhb a typical high QNH is around 1035 and in winter you guys get a big high that settles over the interior that keeps maritime air away, so you would be experiencing high QNH in winter. Although today its 1020-1022 at Jhb Int...

So would imagine that you would see a seasonal change in your QNH...
but check with other aircraft, wouldn't want to be flying around at the wrong altitude, 1 hPa is equal 10m (or 100 hPa per kilometer)so 15hPa error is 150m, not bad, atleast you won't be in the wrong FL. Another trick is cross refernce your altidude with the GPS altitude. Errors might not be linear and you may be way out at higher altitude if there is a problem with the altimeter.

Disclaimer:
Or I could be talking out my arse.

Hi,

If you are airborne in Gauteng, tune into the FAJS ATIS, freq. 126.2 gives you updated weather every 30 mins. In Durban and Capetown the freq. is 127.0.

Regards,
Arnulf

Tjoek - as the others said, get a cross ref with another alti from another plane. could be that your alt is out of calibration. Easy to fix.
CAREFULLY unscrew the little screw on the alit, normally at the "7 or 8 "O'clock position. set the QNH to the correct 10xx, and then pull the knob out, and set the altitude. then push the dial in, and tighten the screw. Do it carefully, don't force it, but to get the knob out, you might need to jiggle it abit

My alti WAS out, but now all wekking 110%

(OK, before some wise arse come's up aith a quirky comment, that was the best I could describe it.)