Light plane crash south west of Sydney 24 Jan 2024.

[turboplanner]

In transit, I’ll give you an answer later. What QNH  do you enter at your local airfield?

[Roundsounds]

6 minutes ago, turboplanner said:

In transit, I’ll give you an answer later. What QNH  do you enter at your local airfield?

The local QNH from ATIS or AWIS. 

[facthunter]

Less than 4 mins from being given a TO clearance to crashing turning base. That's not overly large. Nev

[BrendAn]

14 minutes ago, Roundsounds said:

The local QNH from ATIS or AWIS. 

Exactly. Turbo has lost me.?

[kgwilson]

The instructor got the ATIS and would have set the altimeter. On first contact with the tower you must specify being in receipt the latest ATIS code (A,B,C,D etc). The pilot is assumed to have set the altimeter to the QNH for that code. This process has been around forever, is unambiguous and works.

[facthunter]

 Setting the Kollsman scale for the alt to read aerodrome height is for when the other info is not available or to do  the altimeter check against actual ONH from the tower.  For circuits the most accuracy is by setting the runway end height. which is shown on the aerodrome charts  Nev

Edited March 15 by facthunter
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[IanR]

Are some people confusing QNH and QFE in this discussion ?

[facthunter]

QFE has zero reading on the ground. Different philosophy altogether. . Reduces mental gymnastics but not widely used here.  If you want to determine your altimeter  error to  check it is within limits you need to use the elevation of where you ARE at some stage. There's an aerodrome reference point and the ends of most runways available.   Nev

[Roundsounds]

1 hour ago, IanR said:

Are some people confusing QNH and QFE in this discussion ?

Ian, most pilots trained over the past 30 years probably couldn’t spell QFE, let alone define it and T hey’d need an APP to work it out.

[BrendAn]

36 minutes ago, Roundsounds said:

Ian, most pilots trained over the past 30 years probably couldn’t spell QFE, let alone define it and T hey’d need an APP to work it out.

Cuueffe

[BrendAn]

1 hour ago, facthunter said:

QFE has zero reading on the ground. Different philosophy altogether. . Reduces mental gymnastics but not widely used here.  If you want to determine your altimeter  error to  check it is within limits you need to use the elevation of where you ARE at some stage. There's an aerodrome reference point and the ends of most runways available.   Nev

When training we adjust the qnh to what atis says and then compare Efis alt against steam altimeter. It would be rare for bothe to fail at the same time.

[turboplanner]

6 hours ago, BrendAn said:

When training we adjust the qnh to what atis says and then compare Efis alt against steam altimeter. It would be rare for bothe to fail at the same time.

When you listen out for the ATIS  QNH and dial it in and I’m cross-country inbound and listen out for the ATIS QNH and dial it in we will both be flying the same altitude in the circuit. In this case I was looking at the height above ground level.

 

In this case, ATSB reported:

 

1.     The ADS-B showed 1400’ on the downwind leg; ADS-B output is AMSL (Above Mean Sea Level). I incorrectly picked up on this so we can disregard it because I was talking about AGL (Above Ground Level).

2.     On the graph 1300’ AGL on the downwind leg is shown and notated “Height above ground”.

 

Camden Airport elevation is 230’ + 1000’ciruit height AGL = 1230’ AGL

Camden report Circuit Height in ERSA as 1300’ – 70’ out.

We can disregard the discrepancy in this case, because the pilot was on 1300’ on the downwind leg, so not above Camden’s ERSA circuit height.

[Garfly]

 

 

https://discussions.flightaware.com/t/general-confusion-about-aircraft-ads-b-altitude/79557

 

 

"ADS-B and Mode S (and for that matter Mode C) transmit uncorrected pressure altitude as the primary altitude value. That is, it’s directly related to static air pressure. That’s not necessarily a true altitude, and it needs to be adjusted to produce a correct height above AMSL or height AGL, but it has the large advantage that every aircraft is doing exactly the same thing, which is very important when used for resolving conflicts"