Why are knots used in aviation over kph?
A nautical mile is equal to (about) one minute of latitude, which probably made calculations easier back in the day, with the tradition carrying forward.
Boeing 777 departing Dubai nearly had a major incident after takeoff
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Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#12Why are knots used in aviation over kph?
History is surely one thing, but another key point is that these speeds are always KIAS (indicated air speed). This is a measurement that doesn’t correspond to either true ground speed or true air speed (but is far more useful for flying than either of these).
Certainly I would find kph/mph slightly confusing as you might expect it to correspond to some actual velocity, rather than something to do with air pressure.
Maybe we should measure airspeed in mbar instead?
(ofc navigation is a different matter, and there just history prevails)
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#13Why are knots used in aviation over kph?
Other commenters say it's historical are, well, mostly right, but there is a distinct advantage to knots: a knot is 1 NM per hour, and 1 NM was historically defined as one arc minute latitude. So if you are looking at a chart and doing calculations by hand or in your head, NM and kts are very convenient. It lets you mostly do chart -> distance -> time and fuel measurements/calculations in your head.
Of course this is not perfectly accurate in several ways but given chart projections it's usually Close Enough.
The speeds given in the article are a little ambiguous in the details, the number given in the text is probably KIAS (but maybe not?) and the numbers from FlightAware will be ground speed.
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#14Why are knots used in aviation over kph?
When you translate maps with vast distances down to units, a nautical mile equals a minute of latitude. With long distances, you refer to lat/long over following a road.
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#1575 feets is 22.8 meters.
234 knots is 433km/h.
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#16The memo from Emirates about not setting altitude in system to airport altitude is so weird. I really hope that's not the actual message Emirates is putting out there.
It doesn't matter was in system. You run your checklists and configure for your own flight / your own departure etc. Memo should be to training / recruitment - where did you find these pilots to fly a 777?
So they obviously didn't pre-flight the flight. And they don't seem to have used their takeoff checklist either? That should get them through flap retract and 2,000 feet or so.
Takeoff checklist might have rotate at 160 or so. Then you get to positive climb and V2. You then clean up the plane (flaps / gear etc), maybe hit 2,000 feet / 210kts?
This is all checklist stuff. I've no idea what's Emirates has as checklists, but this is like 101 entry level flying stuff. What was pilot monitoring doing during all this?
They still on ground at 215 kts? 262 kts at 175 feet?!
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#17Why are knots used in aviation over kph?
From my understanding there are two advantages:
- So that when kph/mph is heard a pilot knows they're referencing ground speed, whereas knots is air speed.
- Pilots use latitude/longitude, and a knot is "exactly equal to 1/60th of a degree of latitude. A 1/60th of a degree of latitude is known as a minute of latitude. Therefore, a knot is equal to one minute of distance. There are 90 degrees from the equator to the pole."
But reality is that changing international standards is very hard, and nobody wants to have the battle when knots works "well enough." It likely started because existing nautical maps were used for over-ocean flight planning and stuck.
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#18TL;DR - Don't screw with the defaults (MCP) after landing, especially when it's unnecessary and when the next takeoff crew likely will not remember to set it to proper value before takeoff.
I wonder if this is not a detectable condition for the flight software - maybe in some cases you want the MCP to be set to low? Otherwise autopilot could either auto correct it or issue a warning?
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#19Why are knots used in aviation over kph?
Because the Earth is a non-Euclidean surface, and knots make more sense for navigating a sphere.
Re: Boeing 777 departing Dubai nearly had a major incident after takeoff
#20Why are knots used in aviation over kph?
Maritime navigation techniques were adapted to aviation.
For a similar reason airplanes have captains. A few decades ago they also had navigators. With a dedicated position in the cockpit.
It’s also customary to measure altitude in feet. Except in China (except Hong Kong), Kyrgyzstan, Kazakhstan, Tajikistan, Uzbekistan and Mongolia. Russia is actually moving to feet at some altitudes. Turkmenistan similarly uses feet or meters depending on altitude.
The units themselves are irrelevant as long as everyone uses the same ones. Switching costs are significant both in terms of training and equipment.