I must confess that two of the most frustrating things of recent times has been either following a QF 767 into a terminal area or any AN aircraft (any type) enroute. In both cases you will be vectored and slowed all over the place.
Why AN used to go slow enroute (to make $$$$) and yet were seemingly very efficient in the terminal area and QF 767’s are the complete opposite just goes to show there are many ways to skin a cat.
But seriously, 340 knots to 20NM in BN would not and DOES NOT require speed brake. The CTA steps from the south allow you down to 4000 at JCW (that’s 26NM from touch) therefore you would be well and truly level at 4000 by 20DME (almost exactly 20NM to touch given the location of the BN DME) therefore maintaining altitude and bleeding off speed, take gear at about 240kts, take the first couple of stages of flap on schedule as you start descending at about 500fpm, take the rest of the flaps as required, increasing the ROD as the flaps start coming out. If flown correctly you will drift a little above the desired 3 degree slope initially but will be right back on track by about 2000 feet, and easily stable by 1000.
There are two things about this that QF 767 pilots would be horrified about:
1) Taking gear before flaps!!! Shock OH Horror!!!
2) Bleeding off speed whilst level – Not efficient they say! Well, It means about an extra 2 to 3 miles at cruising altitude (i.e. later descent) BIG DEAL, but if you rely so heavily on VNAV you will still descend at the same point and it will be more inefficient. Besides ATC didn’t ask for efficiency they asked for a HIGH SPEED DESCENT.
Now I’m not recommending to fly every approach like this, but if a company aircraft behind you doesn’t have to get vectored all over the shop, then from a BIG PICTURE perspective (and longhaul love talking about this large picture, but rarely actually look at it) it is an efficient way to fly. Remember ATC don’t give you a high speed descent for fun they are asking you to help following traffic, and these days, more often than not, it will be company aircraft.
And whilst high speed descents don't seem to make a big diffence to you (maybe a minute or two) going just a little faster for just a little longer in the lower levels makes a VERY BIG diffence to the distance between you and someone behind who is flying a profile descent.