Speed Restrictions

[Tailwinds]

I don't know if it's the same for all large airports in the UK, but I always thought there was a speed restriction of 250KT below FL100. I'm noticing aircraft on the radar arriving at Heathrow on the downwind leg (not using network flights), at speeds of 270KT or more when at FL700. What about the big heavies?, Can they get the speed restriction lifted when departing because of it's weight?

[AirNav Development]

Speed restrictions (<250kt below FL100) always exist unless otherwise authorized by the controller in low traffic conditions.

[DaveReid]

I don't know if it's the same for all large airports in the UK, but I always thought there was a speed restriction of 250KT below FL100. I'm noticing aircraft on the radar arriving at Heathrow on the downwind leg (not using network flights), at speeds of 270KT or more when at FL700. What about the big heavies?, Can they get the speed restriction lifted when departing because of it's weight?

There is a perfectly simple explanation for this.

The speed restriction is 250kt IAS (Indicated Air Speed) below FL100.

Once you have made the corrections for TAS (True Air Speed), which are significant at altitude, and then added on any tailwind component to get groundspeed (which is what RadarBox displays), the result can easily be 300kt or more.

Coincidentally, I'm working on an add-on for the "other" Mode S receiver which will allow both IAS and TAS to be displayed in addition to groundspeed (plus a few other parameters such as selected altitude, etc).  I don't know yet whether that will be also possible with RadarBox.

[Tailwinds]

Thanks for the explanation.

[Protzenalp]

...at speeds of 270KT or more when at FL700. What about the big heavies

At levels like FL700 are you tracking the space shuttle???  :)

[Tailwinds]

A typo error. Didn't notice at the time so thanks.

I do track the Orbiter (during a mission), and the ISS along with countless other Satellites using an excellent satellite tracking program.

[CoastGuardJon]

Re. Shuttle and ISS, I've just started another thread for those who are interested

http://www.airnavsystems.com/forum/index.php?topic=1642.msg12846#msg12846

Hmmmmm, I obviously started it in the wrong category, it's moved to General/Aviation...!