A boring old CAO question on Landing performance.

[jpilotj]

G'day

Could I ask someone to please open up CAO 20.7.4 and read 5.1(B)

"an aeroplane must not land at a weight in excess of the least of the weights determined in accordance with sub paragraphs (a) and (b)"

"5.1 (B) a weight which will permit compliance with the landing climb requirements specified in section 9, taking into account the elevation of the aerodrome of landing instead of actual pressure height and temperature".

"Section 9" Refers to the 3.2% climb performance required in the landing climb.

Where 5.1(B) states aerodrome elevation "INSTEAD" of actual pressure height and temperature, can one now decide that a Pressure height of 1500' and a 45 degrees is now somewhat less favourable to an aerodrome elevation of 29' (YSBK) and simply "get away" with only considering aerodrome elevation which in an Australian summer would nearly always offer more favourable conditions than prevailing pressure height.

[MakeItHappenCaptain]

5 LANDING WEIGHT LIMITATIONS
5.1 Except in an emergency, an aeroplane must not land at a weight in excess of the least of the weights determined in accordance with subparagraphs (a) and (b):
(a) a weight at which the landing distance required in accordance with subsection 10 for the pressure height, temperature, runway slope (if in excess of 1%), and wind component along the runway at the time of landing, is equal to or less than the landing distance available in the direction of landing. Approved declared conditions may be used instead of actual pressure height and temperature;
(b) a weight which will permit compliance with the landing climb requirements specified in subsection 9, taking into account the elevation of the aerodrome of landing instead of actual pressure height and temperature.

Probably doesn't look so bad when you read the section in its entirity.

Considering you have to compare the figure for climb performance (5.1 (b)) against LDR (5.1 (a)) you aren't going to be that far out. The increased LDR, which does have to account for temp and pressure, will go some way toward reducing the discrepancy, but I have always pointed out to my students that the old CASA landing charts, while labelled "Pressure Altitude" on the climb performance box, could have a very different result than if you entered at the density altitude.

Go figure.:confused:

[MakeItHappenCaptain]

Drifting, but the same order also says
8 EN-ROUTE CLIMB PERFORMANCE
8.1 Multi-engined aeroplanes engaged in charter operations under the Instrument Flight Rules or aerial work operations under the Instrument Flight Rules must have the ability to climb with a critical engine inoperative at a gradient of 1% at all heights up to 5 000 feet in the standard atmosphere in the following configuration:
(a) propeller of inoperative engine stopped;
(b) undercarriage (if retractable) and flaps retracted;
(c) remaining engine(s) operating at maximum continuous power;
(d) airspeed not less than 1.2 VS.
8.2 Multi-engined aeroplanes (other than those specified in paragraph 8.1) must have the ability to maintain height at all heights up to 5 000 feet in the standard atmosphere in the configuration specified in subparagraphs 8.1 (a), (b), (c) and (d).

Note the use of the words "in the standard atmosphere".
PFFFTT!!!
How often do you see ISA conditions on Oz?
Not the easiest thing to overcome.:cool:

[Creampuff]

I'm guessing it's a consequence of the standard to which the aircraft the subject of the order are built.

If you had to be able to achieve the landing and en-route climb gradient based on actual density altitude, not many bugsmashers would go many places with much load in summer.

Just goes to show that meeting the requirements in 20.7.4 doesn't necessarily equal safe. Indeed, often it's far from it. I recall Gaunty being very outspoken on this issue.

[le Pingouin]

simply "get away" with only considering aerodrome elevation which in an Australian summer would nearly always offer more favourable conditions than prevailing pressure height.

Would you rather they could ping for landing over weight when the conditions at destination turned out to be warmer and lower pressure than you anticipated on departure and there was no way of obtaining an accurate reading before performing the landing? It gives you a fixed reference point.