Hello everyone.
I know that below 10,000 feet we cannot exceed 250 kts. But if I am above 10,000 above sea level but my AGL altitude is below 10000, should I maintain my limit of 250 knts?
Thank you!
FAR states 10,000 ft is MSL.
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10,000 feet ASL was made the standard many years ago after a mid-air collision in the 1960’s (and other incidents) involving aircraft separation challenges at high speed while at low altitudes.
The restriction was made relative to sea level so that everyone would have the same reference regardless of ground height.
There had been debate about pushing the limit higher, but apparently the airlines argued against the higher costs of maintaining slower flight to such higher altitudes.
The damage of bird strikes at higher speed is another issue frequently mentioned (birds more often fly closer to the ground).
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What is interesting here is that 10,000 ft MSL is only true for US airspace since transition level is at FL180. Meaning, you will be setting your altimeter to your destination’s QNH. In other airspaces, transition level may be below 10,000 ft and 10,000 ft is pressure altitude above 1013 hPa/29.92 inHg.
Also, you may also be cleared for high speed below 10,000 ft.
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I didn’t know, thank you.