Is it normal to significantly exceed 250kts under 10000ft in European airspace? Can somebody explain this? I was on a flight from Stockholm to Helsinki (and return) recently, and I have a question based on the flight data provided by Norwegian Air (I live in California, not used to flying in Scandinavia). The flight data seemed to indicate something surprising coming into Helsinki- perhaps it’s an IAS/ground speed issue, but it seemed unlikely- we were well over 300kts descending below 10,000 ft, and this continued well below that. We eventually came down to a normal approach speed, but the whole time I was thinking “violation!!”… Can anyone explain this? I can provide screenshots of the flight data they provided but I’m pretty sure air speed/ground speed can’t account for this. And no, it wasn’t a metric/imperial units issue.
Could u please provide a screenshot. U were most likely looking at the ground speed rather than the IAS
No doubt you’re right. I suppose I’ve never been clear on the issue of this discrepancy, I assume the only mitigating factor is wind speed? Screenshot here:
Also I guess I was incorrect about the destination, this was coming from lax to Stockholm, nothing to do with Helsinki. Anyway, could there have been winds that significant at 9800ft to account for this?
Most likely that was a grounspeed value, or you were just a few knots over. With winds calm and normal conditions 250 kts IAS usually is about 300 kts GS at 10k ft.
I believe you, but I have not heard the logic explained before. Is this a geometry issue? Arc lengths due to curvature of earth? That doesn’t make sense, that wouldn’t do it… I don’t understand, what accounts for this?
Are you asking why airspeed can be so different than ground speed?
What airline has that HUD type screen on its entertainment system?
They could’ve gotten permission from ATC to exceed 250kts ias under 10,000’ msl.
It’s showing ground speed
might be a delay since were not that far below 10 k
The explanation has to do with air density. As you go higher, there are progressively less and less air molecules occupying the same physical amount of space. I have no idea what the real figures are, but for the sake of example, let’s say at 0 ft MSL there are 3000 air molecules per cubic inch. Let’s also say that at 10000 ft MSL there are only 2000 air molecules per cubic inch. This also explains why it’s harder to breathe at high altitudes - with every breath you receive fewer oxygen molecules. Anyway, airspeed is the velocity of air molecules moving over the wing. At sea level, you have to go 250 kts to maintain 250 kts groundspeed. However, at higher altitudes, to maintain the same same rate of air passing over the wings where air is more scarce, you have to increase your speed relative to the ground, or ground speed. This is why 250 kts airspeed is roughly 300 kts groundspeed at 10k ft. Hope that makes sense 😂
Another thing, aircraft can get “free speed” instruction, which means They are allowed to exceed 250kts. However you were Looking at the GS, so that doesn’t matter. :P
I’ve heard somewhere that controllers can issue speeds over 250 below 10000ft, don’t quote me on that though.
I just wrote that in the comment right above yours… Lol
Oh haha, must have not read that properly. Sorry, maybe my comment can be a bit more simpler :)
Should this be moved to #real-world-aviation?
It will be provided by gps using ground speed. It would be too complicated to provide airspeed to the passengers
Normal limitation is 250kt below 10,000’.
However, quite often, ATC will give you ‘free speed’. Great for making up time but puts some co-pilots in a spin as they have to manage their own speed profile!!!
It really wouldn’t, but it wouldn’t give any sense to the passengers. Much cooler to see that you’re traveling in 800km/h