calculating entry to a takeoff chart with a density height

[glenb]

Interested on opinions on how you enter a takeoff chart at the planning stage when you dont have access to actual conditions at an enroute aerodrome when the chart has PH and temp only. Cheers.

[206greaser]

Hey Glen.
Aren't there declared density charts in the AIP? Long time since I've used them. Actually come to think of I've never used them except for examination purposes.

Cheers,
Greaser

[Cap'n Arrr]

If the chart doesn't allow you to use Density Height, then enter it using DH as your PH, and using the ISA temp at the DH altitude. e.g. if DH is 2000', then enter the chart at 2000' PH, and 11deg C (if i remember correctly, the lapse rate is 2deg/1000' , 15deg at sea level)

[glekichi]

And why the hell is it called Density Height in Australia, instead of Density Altitude?

[gadude]

just to be a lil different

[john_tullamarine]

Can you post a link to a scanned image of the particular chart ? .. might allow us to offer useful comment.

Graphical representations may have the Hp/OAT entry yield density height although that output is not usually identified as such.

Otherwise, for your enroute aerodrome, you know the elevation, can estimate the Hp on the basis of forecast QNH, and can use either the forecast OAT, or a sensible guess, to come up with a reasonable answer to the underlying question ....

[av8trflying]

Its actually in CAO's.

Part 20

Section 20.7.0

Appendix I, II, III

[equal]

And why the hell is it called Density Height in Australia, instead of Density Altitude?

because it's the corresponding height in ISA conditions?

[TwoTango]

because it's the corresponding height in ISA conditions?

No, it is the equivalent [bold]altitude[/bold] in ISA conditions. "Height" refers to distance above ground level, whereas "altitude" refers to distance above mean sea level (and for what it is worth, "elevation" refers to the altitude of the ground above sea level, i.e. Elevation + Height = Altitude)

So yes, Density Height is a misnomer technically, but somehow I don't see it going out of usage any time soon...

TT

[tio540]

You should carry a copy of the declared density chart for ops into non atis aerodromes. The CAO is quite specific here.

[equal]

"elevation" refers to the altitude of the ground above sea level, i.e. Elevation + Height = Altitude)

yea i understand all that. these charts are getting me confused tho. you have a 'declared' density altitude, add a field elevation then get a density altitude again?

shouldn't it be more like a declared density height, plus a field elevation gives you a density altitude?

or am i just running around in circles here!

[compressor stall]

Developmental Air Service -

I read in the definitions to the declared density charts linked above the following:

Developmental Air Service: An air service which due to the nature of operational and economic considerations, has been declared by CASA to be a developmental service.


What's this mean? Is it still relevant today or an old bit of leg from the ANO dinosaur days?

[john_tullamarine]

As I recall, back in the olden days, developmental air services basically meant PNG... hence modified standards better to match capability to need.