Wouldn't it be far easier for them to give you GPS co-ordinates and holding around that
Say you want to go into Jakarta, but bad weather prevails and you have to be put into a hold....
Now, a GPS coordinate and hold around that?
"Speedbird 999, maintain heading climb 7000, after reaching 7000, proceed to hold over S05 28.8 E106 54.3" (imagine hearing "South zero five, two-eight decimal eight, east one zero six five four decimal three")...
It's a mouthful... Then, put it into the FMS, U put in S0528.8E10654.3 which is 15 keys!
Now, how about using the radial and distance:
"Speedbird 999, maintain heading climb 7000, after reaching, proceed to hold over DKI
radial 344 at 30 DME
Now that takes about 1/2 the time to give the instruction. On the FMS, U just type in: DKI344/30 which is 9 keys, and probably 1 more key press as the FMC would ask you which "DKI
" would you like to hold over... the nearest, or the furthest? or elsewhere?
Or even better... the Fix actually is a standard waypoint and has a name...
"Speedbird 999, maintain heading climb 7000, after reaching 700, proceed direct and hold over NOKTA"
You'd only have to put in 5 keys to enter the name, and 1 more if there's multiple selection.
So, giving the GPS coordinates for a holding ISN
'T ideal! And in crowded airspace and bad weather, that's the last thing you want.
Furthermore, if that fix isn't ideal, ie, weather has moved into the fix, they can just say "how about 'FIX NAME'" or "How about DKI
radial 090 at 20dme?" It's also quicker for everyone who hears the transmission to make a mental picture on where it is... and also quicker to find that spot on the map and in real life... and also in the FMC...
Now, a hold requires:
1. A Holding Point
2. Heading inbound to holding fix,
3. Left or right hand racetrack pattern (if not a 1 minute standard, then time has to be put in as part of the instruction)
if we use the GPS coordinates, how do we know #2 ?
If we use the radial/dme method, it's only 2 guesses... 344 inbound to the fix, or 164 inbound to the fix, and most likely to be 164 inbound.
I hope this explains why...