747 Speed

[andyjohnston.net 617]

I saw someone recently state that the 747 wasn't limited to 250 kts below 10,000.  Is this correct?  I though it applied to all aircraft, and I haven't been able to find anything saying it was permitted.

[Alpine Scenery 1,609]

Check this thread out:

https://aviation.stackexchange.com/questions/34480/what-aircraft-fly-faster-than-250-knots-indicated-airspeed-under-10-000-feet-for

It appears to only apply if a 747 is loaded down and the minimum safe speed is affected enough to where you might have to exceed this under certain conditions. I doubt it's exceeded by much, probably 10-20 at most, so doesn't make much difference.

a 747-200 with JT9D-7Q engines that gives the flaps up holding speed at 800,000 lbs as 259 kts at 5,000 feet

 

Edited May 23, 2021 by Alpine Scenery

[Chock 17,769]

It's something which is understood by air traffic controllers, who would never restrict a 747 to a speed on climb which they couldn't fly at, and even if they did, as the skipper of the aeroplane you could and should ignore a stupid instruction and say 'unable'.

To be honest, the speed wouldn't be that much past 250 knots, so it's pretty negligible anyway. ATC people have to know a fair bit about the traits of various airliners, for example, they all know that the 757 has a massive wake turbulence, so they give it the same spacing behind that is normally only applied to much bigger aeroplanes such as the 747 and the A380. So of course they also know that at MTOW, the 747 could drop out of the sky if it was told to climb at 200 knots.

If you spend enough time around airports listening to ATC, you will almost certainly hear many aeroplanes being given their instructions followed by the controller saying 'no speed restriction', so it's actually not that uncommon for quite a few airliners to be allowed to go faster than 250 knots below 10,000, as it is an ATC controller's job to try to expedite stuff so long as it is safe to do so.

[SAS443 1,716]

3 hours ago, Chock said:

so it's actually not that uncommon for quite a few airliners to be allowed to go faster than 250 knots below 10,000, as it is an ATC controller's job to try to expedite stuff so long as it is safe to do so

Apparantly EASA and FAA treats this little differently.

FAA has a hard 250 kt limit or minimum clean speed, which controllers can't waive. You will not get free speed in class B airspace. ATC simply hasn't the authority to issue such clearance in the U.S.

Meanwhile, flying in Stockholm TMA I hear "free-speed approved" / "no speed restriction" issued to other planes quite often.

 

[JETPETER2 166]

in other parts of the world, 250 below 10,000 may not exist... a 747 at heavy weight may fully clean up at 265 and request 280 IAS until above 10,000 to be drag free..... but don't forget a nearly empty or light 747 stall speed is around 90k 

[Doug47 574]

On 5/22/2021 at 7:14 PM, andyjohnston.net said:

I saw someone recently state that the 747 wasn't limited to 250 kts below 10,000.  Is this correct?  I though it applied to all aircraft, and I haven't been able to find anything saying it was permitted.

The 777_ 300ER , 747-400 and even the A340 have a minimum clean speed at MTOW of around 270-280 KIAS. And in most cases around the world, that’s what they fly at on departure. I think even the 767-300 has a minimum clean speed over 250 kts. And not unusual for ‘speed restrictions’ to be canceled as well.