Airspeed limits

With the last update a few weeks back, I get airspeed limitations to 350 above 10k, and sometimes 300 @FL120, anybody know why?

That’s the new overspeed warning feature that was added in the 787 summer update. Read more about it here for an in depth explanation:

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Because it’s like that in real life.

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Not sure its true or not.

Because I traveled from Malaysia to Singapore and vice versa always, the plane flew over 28k altitude with airspeed 500 knots as always…

The 500 knots is in ground speed

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Ground speed would have been about 500kts, but airspeed would have been about 240-260 KTs / M0.81 or so depending on the aircraft. If it had been IAS of 500kts, unless it was a F22, it would have broken up as commercial aircraft are not designed to go that fast as they would break up! Latest update put the overspend warnings ( little red dots on the air speed indicator) to further replicate relal life.

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Hey @adrianyujs -

Those nifty in-flight displays you see in the passenger cabin often show ground speed, or also can be displaying true airspeed (Infinite Flight uses indicated airspeed as opposed to true airspeed.) Check out this wiki on true airspeed (TAS is going to be a higher number than IAS, especially at higher altitudes).

Happy landings!

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Another way to look at it @adrianyujs -

  1. Airspeed = the speed your aircraft is moving through a certain amount of air. Like water, air has mass.

  2. As altitude increases, the air is thinner - meaning the same amount of air at 30,000 ft is going to take up more physical space than at sea level. (Try this example next flight you take in real life - blow up a balloon on the ground a little bit, like the size of a grapefruit. As the aircraft climbs, your balloon will increase in size because of the lower pressure. This is also why yogurt packages sometimes blow up on your shirt when you get your breakfast tray on the plane!)

  3. Therefore you have to move a lot faster at 30,000 ft to make 250 knots, because the air is much thinner. Indicated airspeed only tells you how much air is moving past the aircraft. If you’re up high enough, it will eventually show ZERO because there’s no air. (And our airliner balloon would totally just pop at that altitude. And water would boil at room temperature. But that’s a whole other discussion.)

An extreme example: The Space Shuttle in orbit flies around the earth with a ground speed of roughly 25,000 mph. Indicated airspeed, at orbit altitude, would be 0 KIAS because there’s no air.

Hopefully this makes sense. Overspeed seems to happen “more quickly” at altitude because of the growing spread between actual ground speed and IAS. (Mach number solves this problem neatly at high altitude.) Also, G-forces come into play - pulling into a 20-degree bank at 500 kts ground speed will stress the airframe way more. Infinite Flight does a nice job creating models where we can discover relationships between airspeed, ground speed, and G-forces, and experiment with the efficiency of jet engines at different altitudes.

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personally i think the speed limit should only be in use bellow 10,000 feet. I’m a pilot in training and my dad is a commercial pilot. He says above 10,000 feet the speed limit is the speed of sound. (but there are certain spots in the world where airliners made to go supersonic can fly)

At high altitude Mach Numbers are flown, not airspeeds. Obviously airliners want to make best use of Jetstreams and hence will climb and descend to get the highest tail wind or lowest headwind.

500Kt’s IAS is a touch beyond most airliners!!! 500Kts TAS taking into account lower air density at altitude is quite achievable!

Posted before but I snapped this from my ND over Newfoundland:

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Realistic or not the limits are there because there are just too many planes in a small region. It causes issues for the ATC to try to manage an inbound plane at 10,500 going 480kts to fit into the flow.

unless its a concode

how many supersonic airliners are currently flying?

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Answer = None

correct! :-)

none im saying when they where flying and they where retired when i was only 3 years old

Concorde cruised at 50-60k feet… not 28k.

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Yes concord retired a few years ago now, however you did mention ‘other supersonic airliners’, so was not sure if ther was any that I was not aware of in service? AFIK Concord was the only commercial Supersonic airliner in history. :-)

You’re not going to be pushing the speed of sound in any commercial airliner. When flying we go for efficiency, which sets the sweet spot right around M0.80 for current airliners. If you go faster, expect to burn a lot more fuel which is not something you want. Even if fuel costs didn’t mean anything, the structural limits are normally around .85-.9 for most airframes as the drag rises in an exponential fashion as you near the speed of sound.

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there was the tupolev 144 and Boeing 2707 the 2707 never went into production