A question to HKG ATC . . . . dudes

[oicur12]

The STAR charts indicate to PLAN to cross melon at 130/150 etc. A recent note to crew at dragginair states that if you are REQUIRED to cross melon at a partiular height, ATC will make such a requirment.

Therefore, what does it mean to plan for 130 at melon. We give it a shot but if we cross melon 20000' high its ok cos did our best?

What does PLAN mean if we havnt been given a REQUIRMENT.

[badairsucker]

Our ntc states that if cleared to 130/150 at melon if the next controller clears you below the 130/150 ie 110 at TD you don't have to comply to the 130/150 restriction. Anyone care to clear this one up as well.


While we are at it.

What about the speed restriction at porpa. 220 till on track TD, if cleared high speed before propa can you increase speed or wait till porpa then increase.


I know what I think, but many different thoughts on the flight deck.

[oicur12]

I have never understood why there are speed limits at waypoints such as porpa when the dep is rnav. The aircraft will turn to intercept the next track from porpa so speed is irrelevent.

I agree, does no speed mean wave the 220 at porpa. Does "high speed" on descent mean no req for 250 knots below trans.

HKG is so open to interpretation according to who you are flying with on the day.

[Hole in Two]

Yes ATC will make such requirement, but sometimes it can all change in a flash. Don't yell at area radar though. The Melon requirement is given to area radar by the Flow controller. If pilots are told late, that's because the Flow is not efficient.

Some weird Flow controllers impose a 280kts restriction with a 10nm spacing:uhoh:. What's that all about? Why 280kts?

[Lowkoon]

Because airbuses opperated by certain local operators plan to descend at 280! :) The pace cars of the sky...

[willnotcomply]

High speed clearance means keep your speed until told otherwise. It would be courteous to inform ATC when you are reducing, if you have been left to plan your own reduction.

[bekolblockage]

The 220 kts at PORPA is a PANS-OPS procedure design requirement to reduce the radius of turn and contain the flight path for terrain considerations. Don't overestimate the ability of your FMS to exactly fly the track just coz you're on an RNAV SID. No RF legs in our procedures yet. Controllers shouldn't be cancelling the speed restriction on first contact - unless they want to take responsibility for your terrain clearance. Some smart ones will say "No ATC speed restrictions" or "No speed restriction once you're established southbound". If you want to go faster, then you need to understand the implications.
The recent change in interpretation by ICAO has followed the UK philosophy that once you change frequency and are issued a new descent clearance, all previous requirements/restrictions are automatically cancelled and need reiterating by the next controller if still valid. Personally I think its a crock, made up by people who seem to find ambiguity in anything. It probably doesn't make much difference at MELON if you're already aiming for 130/150 and change frequencies but the 260 requirement at ROBIN can be fairly critical to miss northbound overflight traffic. If you plan to be clever by leveling off higher just because the next guy didn't reiterate the requirement, I suggest you keep a sharp lookout to the right.

[oicur12]

Willnotcomply,

Thanks for the info.

Bekolblockage,

When cleared high speed on dep I usually select 280 knots, a good compromise. The turn remains the same at porpa. We only fly at light weights compared to cx so terrain is not an issue by the time you are in the turn.

The issue of speed reduction is one that bugs me bigtime. Few folks understand descent profiles and rational speed reduction stuff so the most common thing I see is slowing down way early, being low and dragging it in. when ATC turn you onto heading 265 from west of TD and nothing on TCAS, we should keep the foot to the floor until at least 20 miles to run.

[KABOY]

If you overfly PORPA and initiate a turn at 220 kts your radius of turn is far smaller than overflying at 280 kts.

The FMS will overfly Porpa regardless of speed, that is why the EOSID has a max speed. Is noise abatement a factor in this?

[Lowkoon]

220kts at porpa rover, just to clarify, if you hit porpa/rover at a speed greater than 220kts, you will exceed the splay that has been calculated for obstacle clearance based on that SID. However, if you are at a height greater than the obstacle clearance height for that point, then you are in no mans land, until you reach a specified obstacle clearance altitude, or established on a defined track, or above radar lsalt or MSA etc . Because there is no gradient specified, the 220 knots gauarantees you obstacle clearance at a gradient of 3.3% or less, and at an altitude of 120m (394')minimum. (Hence the 440/220kts in the MCDU).

Obviously a normal departure, with no performance degradation, you will exceed these figures, so once you have gauranteed obstacle clearance, either visually (Brave call in HKG), or once above Radar lsalt or sector MSA, do whatever speed you want. To remain "legal", maintain 220kts to MSA,or established on track after porpa/rover then accelerate.Obstacle clearance will be no longer and issue, and splays etc are no longer an issue. Clear as mud? See your jepps, ATC SIDs, turning departures.

[Bedder believeit]

OICUR 12
The issue of speed control may well be one that bugs you. I suggest operations into an airport with no other traffic will fit your bill. It's quite simple really, ATC are just trying to get one landing aircraft after another over the given landing runway threshold a certain distance apart. There are many variables that can detirmine how this is achieved and how the result pans out, it's not always perfect, but 95% of the time it's pretty much on the money. Whilst the world of aviation is very much 3 dimensional - some would now say 4 - the radar screen is really a 2 dimensional display, and it's just a matter of juggling all the different variables to try and achieve an efficient flow rate, one aircraft followed in turn by the next.
Re your second post, having watched many hundreds of thousands of aircraft departing towards PORPA/PRAWN, I think I could honestly say that very few would be needing/wanting a lot more than 220/230KIAS before those positions anyway, and re your "when the dep is RNAV", well there are quite a few departures that are not RNAV, so I guess the lowest link in the chain has to be satisfied. Another issue is separation on departures. With the terrain that we have here, if aircraft were departing with little or no ability for the Aerodrome controller to assume what your speed will be in comparison to the preceding, then we would end up with lot's of departures milling around PORPA/PRAWN basically together. Nothing much can happen until you are above the min Radar vector altitude (4100'). As airspace gets busier, then the procedures become more formated/rigid/less flexible.