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Old 14th Jan 2023, 04:14
  #133 (permalink)  
donpizmeov
 
Join Date: Apr 2001
Location: overthere
Posts: 3,037
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Originally Posted by john_tullamarine
Not true re airline

In Oz, the rules for heavies have always been reasonably well prescribed. Except for benign terrain airports, it has always been a reasonably detailed exercise for the ops engineers to run the sums to keep the aircraft out of trouble. Some places require a bit more work than others, of course. The rules for lighties, on the other hand, are not of much practical use. In years gone by, when I played with lighties, I used to do a bit of a mix and match to improve my chances of seeing another day ... The use of GPS for track guidance gets a bit complex as there are various accuracy and reliability considerations which come into the melting pot. The older pilot flown mandraulic analyses included a fair bit of fat to account for reasonably likely stick and rudder problems.

ERSA gives terrain climb gradient for most airfields

I have a slightly secondhand bridge to sell you ..... generally, such splay data as may exist is too short to be of much interest or use.

And will give several for the same runway under supplemental take-off distance data.

STODAs can be of use as one can run some sums and infer discrete obstacle information to some extent. Most folks aren't aware of this - I can recall, in these pages, introducing Old Smokey to the technique, years ago. Given that no-one (as far as I am aware) does inclino surveys (one identifies and figures the discrete obstacle data from a traditional survey and then works backwards to get the surface data for ERSA - why ? Who knows). And then, those of us who do the backroom work ring the surveyor and get the discrete data for use.

However, STODAs are of little direct value to light aircraft operations as the takeoff is predicated on a relatively high AEO climb gradient capability. OEI and one wants to do a discrete obstacle analysis ? Pardon me, briefly, while I suck in my breath somewhat .... I've had a few robust discussions with CASA folk in years gone by regarding their published requirements for lighties but that's a whole different story.

Type A charts, for the major runways, are a lot more value but, even then, they often don't go out far enough or, for some runways, still need an escape path turn to avoid the rocky bits. Keep in mind that some Types go on forever before the net flight path gets to 1500 ft. The DC9, for instance, due to the lengthy third segment, takes a LOT of miles to do so ....


aerodromes feeding data to the airlines about survey details.

Not quite the case but such information as the aerodrome operator has can be obtained. Problem is that, oftentimes, that data is nowhere near enough to be fit for purpose. In such cases, the operator's ops engineers have to resort to this and that to get an adequate set of data. In general, Captain Speaking, out on the line, would have no way of achieving what is necessary to figure the RTOW. The sums are the easy bit, getting the obstruction profile data is where the workload lies.

I notice that all ERSA provides for this strip is a bland statement that there is "high terrain in the circuit area". That's pretty useful stuff is it not ?
In some places STODA is all you have John. Make sure you can make that gradient if a motor stops to circling, and get above 10nm safe before leaving the circling area. Degrade gradient for turns if you need to turn and depart from overhead. It's not perfect, but a bit better than TLAR (that looks about right).



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