Descend when ready

[Ozgrade3]

I'm just curious about the ATC instruction, "descend when ready to ..........". In some cases, this can be given up to 20 mins before top of descent. Some time later, the crew advise thay are leaving that level for the cleared level.

Wouldnt it help the the contoller for forward planning if the pilot gave a proposed top of descent if its some time off, either as a DME disatance or time.

Does the controller know already when jets will have TOD, turbo props, Lighties etc. Do different airlines have different TOD points for the same type etc.

[compressor stall]

Most controllers seem to be aware of the different prolfiles. Darwin 3 years ago was a bit different - not realising that 402's needed 500fpm descent rates with pax. You'd have to demand descent.

A descend when ready instruction is usually issued when ther eis no other traffic or in particular when the aircraft are all arriving via a STAR.

[Dan Kelly]

If one reads between the lines, one can duduct that ATC no longer have any CTA conflict, and don't have anything planned for the chunck of airspace one is in, or going to descend through, prior to going OCTA.

The AIP requires a report to ATC when leaving a level that has been maintained.

Most jet transport and pressurised aircraft descend more or less on a 3 times profile; eg, Fl300 into Alice, ~ 2000' AMSL, threfore 28000' to lose, therefore TOPD ~ 84nm, give or take wind, circuit, inst app allowances.

I wouldn't have thought I'd ever received such a clearance 20 minutes prior to requiring it though.

[SM4 Pirate]

Dan has summed it up well.

We have a good knowledge of our airspace and the user of that; B737's do range of X-Y, DHC8's do range of x-y; etc. the odd ones can be trickey; e.g. international operators or private guys...

But basically I'll only give a When ready, when he can't hit anything to that level; if it changes, I'll amend the when ready instruction level etc...

On one of the sectors I work; Every call is almost an instant reponce of 'When ready descend to...' As the pilots are looking for descent within a few minutes; or they've already requested descent on the previous sector.

If you've requested descent , my responce will be descend FLxxx; because if you've asked, you want. If you don't want it (within a minute), say approaching descent point or descnet point in x minutes. this will usually get a when ready descend response, unless there is a restriction.

Out of interest I'd be giving advice about when descent is available if a 'when ready' isn't practicable due restricting traffic, when I can.

Bottle of Rum

[Ozgrade3]

SM4, that was exactly what i was looking for, thanks for the info.

If I'm give a "descend when ready.......' clearence, but I want to stay high just a little bit llonger than normal, does it help you if I gave you an idea when I would be descending.

[BCF Breath]

Any info is good info.

20 min early though, I'd have forgotten the clearance by then. If I didn't write it down...:p

[Blastoid]

Agree with SM4 Pirate.

Many do it early (e.g. with STAR clearance) because you have to state a level anyway, and if there is nothing in the way then it cuts out a transmission later on. Personally I try to leave it until about 5 minutes prior to TOPD (on estimated profile) because by that stage the pilots a preparing for descent and they are less likely to forget the clearance. :hmm:

Any info is good info; just as pilots want to know if they are likely to be restricted on descent or when they can expect it, variations to descent profiles are also invaluable. Had several jets that have descended 200 NM Brisbane to absorb a delay in a shallow descent (read: glide!) rather than hold. So it definitely helps traffic planning.

ATCs are also aware that profiles will change, for example, when aircraft are given sequencing instructions that necessitate a go-fast or slow-down, and facilitate accordingly where possible.

[AirNoServicesAustralia]

20 minutes before top of descent???? I can't believe that. The only sector (in Southern District cos I haven't worked in the Nth) where 20 minutes prior to TOD you could get a when ready descend would be the Alice Springs sector, where going Sydney-Alice you may be on the frequency that issues the descent 20 mins before TOD, but with the possibility of nose to nose probs with that bit of airspace usually descent is given when asked for (well it was in the old paper strip days when I worked it). I am assuming you are a jet jockey, cos if you're a bug smasher then desregard all as you could be 50NM from Arbey and still be 20 minutes from top of descent.

I know this is isn't the question, but interested to know how QANTAS are flying the A330's as Emirates start their descent extremely early and as a result drop Ground speed alarmingly, especially when compared to the other half of their fleet the 777's that like to stay high and fast. Just interested how the QF A330's have fitted into the sequences over here.

Oh and the other whopping sector previously known as Sector 1, and particularly the part around Ayers Rock, is also a place where you could get when ready descent 20 minutes before TOD, but again being non radar that would be an unusual occurence, more likely to be descend now, requirement to be FL*** by time ****

[Capt Claret]

Agree with Dan and ANSA , I've not had a clearance to descend 20 minutes prior to requiring it. More likely about 5 mins 99% of the time, and occasionally, one needs to remind the friendly ATCO that it's time.

A colleague inbound to Darwin, in a former life, whistled over the top of Darwin at circa 10,000' in a bandit once. He was waiting to see when he'd get a descent clearance.



Hey :mad: you still up there? :p

[SM4 Pirate]

Nearly another wooden spoon hey...

I know this is isn't the question, but interested to know how QANTAS are flying the A330's as Emirates start their descent extremely early and as a result drop Ground speed alarmingly, especially when compared to the other half of their fleet the 777's that like to stay high and fast. Just interested how the QF A330's have fitted into the sequences over here.

Very similar story here, TOD at 130 miles (not track miles to run) out or a little further from mid FL300's; slow because they get low; but then around FL150 catch up normal jet profile and speeds. Don't really watch them in TMA but I suspect they are good till 10 miles then behave like most internationals, which is generally slower than most domestics.

Re: Melbourne sectors, BLA can be lazy with Descent and STAR together abeem CB, or 20 NE if early transfer... so I'd think they could reach 20 minutes before TOD; it would be close.

Bottle of Rum

[AirNoServicesAustralia]

One of the big reasons I went to the Middle East is my football team is rubbish (thanks to the AFL's unfair penaltys) and hopefully in 5 years I'll be able to come back to a good team.

Good to see the A330's don't just give us heartburn and make us choke on our coffee when you look up from the crossword to see your nice 11 NM in trail has become 8NM with a mile a minute closing. I spose its not their fault, one of the pilots explained its cos of the huge wings they have they have real trouble losing altitude cos they glide so well, so they need to start down earlier. Although he also said that if you point out to them you need them to stay high and fast if they are to stay No.1 they can be flown differently to achieve that if the pilot knows his stuff, not ideal for the aircraft but can be done.

Bottle of VB (if only I could get one!!??!!)

[TopperHarley]

Cleared to 7000.......

Getting a bit high on profile, "ABC Approaching 7000"

Does this gentle reminder give ATCOs the 5hits ??

[AirNoServicesAustralia]

It does if your 9,500 ft at the time you say you're approaching 7,000!!!! To give the pilots the 5hits back I ask them to verify there mode charlie as it seems to be 2,000ft out :E

[Capt Claret]

If calling "approaching" 2,500' above the level is considered excessive, what is considered acceptable?

I usually call about 1 min before reaching the level to allow time to get the call in and receive, hopefully, a clearance for continued descent, before the autopilot starts capturing the level. Thus with a vertical speed of -2,000 fpm, it'd be 2000' above the cleared level.

[SM4 Pirate]

Depends on strokes of the fokes; when you're doing 2000ft per minute, 1 mintues warning is more than acceptable, I'd have thought...

But if you were doing 500ft and called 2500 above, that's excessive...

I've had QFA 767's assigned FL290, leaving FL350 reporting approaching. I hate that... Or worse, 'expect lower in 15 miles due crossing xxx', 7 miles later 'approaching FLxxx'...

The airpace structure going into SY; has sector (vertical) boundaries in a few places. Abeam CB FL 285; 110 SY FL245; 90 SY FL205. So we can assign without coordination FL290 initially, FL250 and FL210 and A100 at those steps. Often this is tight with QF762, QF332 profiles; so we often get the approaching call; but can't give for another 30 seconds or so... Or coord, which may take 30 seconds to complete... This is often the major generator of 'in with a ground station, say again'; I'm doing coord to get you lower.

Bottle of Rum

[AirNoServicesAustralia]

I take your point when descending at 2000 ft a minute wanting to call 1 minute before having to level off, but if you consider that there are times I have 10 aircraft all converging at the arrival fix all assigned varying interim levels if they all call "approaching" their level 1 minute before they reach it, it has a snowball effect and I never get a chance to assign descent to anyone.

Sorry but I have a radar and can see what level you are at and if I'm busy last thing I need when trying to assign someone descent or turn them is you overtransmitting telling me what I already know but have put to the back of the priority queue. If the frequency is quiet fill your boots and tell me you are approaching.

One thing I would like to thank Aussie pilots for is that they always advise there level maintaining, or assigned level on first contact. I've been amazed overseas to find at least half of the pilots flying through the middle east have an initial call with just the calsign and nothing else, meaning you have to make an extra transmission (and so do they) to get their level out of them.

[CODIE]

Often this is tight with QF762,

Shouldn't have a problem anymore. Descent profile has now changed to same as 763

rgds

[o1genesis]

SM4

Please keep contributing!

Your information is precise, succinct and invaluable.

Keep it up, it helps us all.:ok:

[SM4 Pirate]

Codie and interesting point; what is a profile?

QF762s at 320Kts used to be closer to QF763s than they are at 300Kts due to the (bypass issues, I think that was it) different engines...

The latest management/saftey experts wanted everything flying same; so now 300Kts all around... effect 762s are slow and low, like the good old days.

To achieve a landing rate with like types, (jets) 744's, 734's and 763's and 738's (at 290kts, if they stay high) very similar profiles at 300Kts, (speed over the ground) (excluding internationals) 737's, 738's (virgin), 712's similar, but 712's can be a little slippery and require extra watching...

As for the other jets, Inter 744's (who knows how they will go, usually Singapore are slippery, MAS also, but Thia, United, BA, Cathay are all slower, sometimes crazilly so... but then every now and then you get a fast one that really stuffs everything up...

Giving speeds is only one aspect; a 340Kts Thia that is low, goes slower over the ground (because of the height factor) than a QF738 at 290kts, generally speaking.

Then you throw in a mix of others like Ba146s, which everyone thinks are slow, they are till they point the nose down; then gravity takes care of it... high descent profile + less IAS, equals more Ground Speed than many give them credit for or in some cases plan for...

Then business jets etc... other internationals 772s, 773s, DC10s, MD11s, A342's, B763's, B743's, B742's etc... None of you do the same thing... Eventhough most of you are flying 300IAS...

Approach want you to be nicely spaced, 250Kts below 10; this evens things out remarkedly... You are all very similar below 10... but how you get there keeps me employed...

MAESTRO only knows what the engineers told it; most jets all do the same time from 120 miles... all jets... awsure! This is why we get you all slowing down and then turning etc... Because MAESTRO picked the wrong number one... MAESTRO is Strategic time based flow; the ATC's are the tactical element.

As for giving the 'times at a fix'; which we call the feeder fix (FF); WELSH, RIVET etc. two times 3 minutes apart might have two aircraft at 120SY at the same time; because of different FMS settings, crew input etc. Aircraft A chooses min mach, 300kts on the drop; Aircraft B chooses normal mach, 250kts on the drop. both at 120SY together, aircraft A will get to the Feeder fix first, but not with a sep standard. Also times are constant... landing rate might be 2.5 minutes, how do you issue that...? Crew can be +/- a minutes of the time issued etc.

If it were as easy as giving out times; we'd all get a lot more done... but in practice that just doesn't work. When people try, it gets really ugly, fast...

I've been caught with turbo props the most; number one on an FF; I'll slow everything else to 210Kts and space them; 10 miles apart; then number one is doing 180 but doesn't speed up at the FF; all of a sudden, the trail is gobbling him up at 60kts G/S... ugly... number one, report speed, 180kts, not speeding up until descent... well that won't work... speed from the FF means just that... even if it does take effort.

Jets at 250 and t/p's at 210 from 45 SY is almost the same time from 45 SY to the threashold, due different circuits, turning times etc. hence why these were chosen. BN and ML are also using these, to keep things consistent...

Bottle of Rum.

[Blastoid]

Brisbane has only just begun to experience the wonders of MAESTRO, looking forward to the "surprise" element that it predictably delivered during the training. I guess a computer just can't make decisions like a human :hmm:

As for descent clearances, North of Brisbane, the STAR-issuing sector has the aircraft for about 150-200NM to top of descent.

We could give it nearly 30 minutes early if they wanted it!!! :}

[topdrop]

The slipperiest have to be the ANG F28's - I've seen them 6 miles to run, grounding 270 descending thru 5000ft and still get in no problems - wonderful things those barn doors.