Slower than the speed of sound

[Copper]

I have seen that heading East over the North Atlantic in winter.

I remember one British Airways pilot making an announcement to let us know we were travelling faster than the speed of sound (kind of) in a 747. He woke everyone up at about 2 AM to let us know. We arrived in London over an hour early.

[89th]

You know, how does an airplane even know it’s ground speed?

[Aqua Letifer]

@89th said in Slower than the speed of sound:

You know, how does an airplane even know it’s ground speed?

Science is neat.

[Horace]

@89th said in Slower than the speed of sound:

You know, how does an airplane even know it’s ground speed?

There's a gage in the cockpit which shows the speed.

[Copper]

@89th said in Slower than the speed of sound:

You know, how does an airplane even know it’s ground speed?

Especially when there is no ground, over the ocean.

[bachophile]

https://cdn.boldmethod.com/images/blog/lists/2016/12/the-4-types-of-airspeed/tas.jpg

[taiwan_girl]

How about those Taiwanese? 555

[89th]

So I asked our resident expert, the internet. After an exhausting 12 second search, it seems the groundspeed was NOT know before satellites (GPS). Further, one cool explanation of pre-GPS was:

Simply put, the pilot notes the time they passed over a landmark on their route. Some time later they would do the same again. Knowing the distance between the two points, and the time taken, a pilot can calculate ground speed…speed = distance/time…either mentally, if the numbers are relatively easy, or by using a computer like this…

[George K]

"Computer," LOL.

[Copper]

@89th said in Slower than the speed of sound:

before satellites

Google has let you down.

There was a system known as LORAN. I used it when I first started flying. It was decommissioned in 2010. There were ground-based broadcast stations that were used kind of like GPS. This was widely used in general aviation.

There was also inertial navigation, but that was mostly used by astronauts.

And sadly, I doubt if the younger generation can deal with an E6B.

[Jolly]

Couldn't WW2 navigators do celestial observations? Could they plot ground speed by that?

[Copper]

Yes, 2 positions and a clock should do it, your accuracy may vary.

[LuFins Dad]

Virgin Atlantic flight from Dulles to London just did the same thing. Apparently the Gulf Stream is NUTS right now.

https://www.flightaware.com/live/flight/VIR22/history/20240218/0410Z/KIAD/EGLL/tracklog

https://www.washingtonpost.com/weather/2024/02/18/record-jet-stream-winds-dc-flights/