Airspeed under 10,000 - again.

[flying dog]

Yes, a while back I asked and it was kind of ....... not answered.

 

To the best of my knowledge under 10,000 the top speed is 250 kts.

 

Yeah, when you are inbound they may let you go over and this is - I believe - because you are falling/going/coming down and so there is little/less engine noise.

When you are departing you are climbing and need thrust to climb and that equates to engine noise.

 

Yes, modern engines are quieter, but the rule still is.

 

So why is it that recently I have seen TWO "SUPERS" taking off in Sydney (34L) going up over 5-dock/Rhodes at 4-5000 and have an airspeed of 270?

 

They were low for their position which also is why I looked at them.

 

I don't want to get into an argument about what altitudes planes are at where....   I think it the term is GISS/JISS?    General Information Size and Shape or Just Is Size and Shape.

I know the usual track of planes over me.

These WERE lower than normal and sounding different.

 

Pulled out FlightRadar24.

Found them.

4-5000 270kts.

 

Someone?

Not to get anyone in trouble, but does anyone here work at YSSY tower and mind joining in on what's going on with them?

 

I'm not the cops or anything.

 

Just curious.

 

[cooperplace]

This is a constant concern when I'm flying the Jab.

[facthunter]

5000 feet used to be the level where you could accelerate when departing West. and be over Sydney VOR and track east of the extended runway centre (left turn) till then.  Nev 

[Bennyboy320]

250KIAS at 5000’ equals 270KTS TAS, Flightradar24 displays ground speed.

[facthunter]

There could also be a wind affecting that. Nev

[Roundsounds]

You’re quite correct regarding the limit of 250KIAS below 10,000’. A heavy jet on departure may need to exceed 250 to fly with flaps retracted and ATC can approve the exceedance.

ATC may also approve high speed ops below 10,000 if requested by the crew.

[KRviator]

23 hours ago, Bennyboy320 said:

250KIAS at 5000’ equals 270KTS TAS, Flightradar24 displays ground speed.

True if you don't have access to the ES downlink, but @flying dog specifically referenced KIAS, which suggests he can read the downlinked IAS. Here's a screegrab from my FlightAware SkyAware tracker showing what's being received from a Dreamliner coming into Sydney right now, so you can receive both KIAS, KTAS and GS if you have the right gear, but if you simply use the public sites, you probably won't see the rest of the ADS-B squit beyond just GS.


To answer the question, 250KIAS is the limit unless higher is operationally required. You'll find heavy jets, particularly 747, 777 & Airbus (what's the plural for a group of A380's? A problem? Airbii? 😕) have green-dot (minimum drag / best L/D) speeds above 250, and as such often "request high-speed climb" which ATC can, and routinely do, approve. For the A330, it's calculated at Weight(t) x 0.6 + 107Kts, so 230T = 245KIAS. That A340 that went 4WD'ing at Melbourne had an (incorrectly calculated) GDOT speed of 265KIAS, for example, so after retracting the flaps, that's what the crew would want to climb at.  In the absence of approval to exceed 250KIAS, then that remains the default limit to transition altitude.

I'll try to dig up an AIP reference later today.

Edited December 3, 2023 by KRviator

[flying dog]

Seems I owe people a huge apology.

 

FlightRadar does show GS and that is what I saw and somehow misread it as KIAS.

 

(Need to go to spec savers)  😉

 

Again sorry to all.

 

[facthunter]

 To err is human and to forgive, Divine.  To never make a mistake you just have to do, say or make, nothing. Nev