Aviation units and speed, distance, time — transcript

00:00:00.400 --> 00:00:04.150 Aviation units, conversions, and speed, distance and time:

00:00:04.150 --> 00:00:06.565 the numbers behind every flight plan.

00:00:07.400 --> 00:00:13.637 Aviation mixes its units. Distance from an aerodrome is in nautical miles.

00:00:13.637 --> 00:00:20.124 Altitude and elevation, in feet. Wind and aircraft speed, in knots. Pressure,

00:00:20.124 --> 00:00:24.615 in hectopascals. Visibility, in metres or kilometres.

00:00:25.400 --> 00:00:28.786 But your drone's manual and app often use metres per second.

00:00:28.786 --> 00:00:32.505 So converting is part of checking your limits before every flight.

00:00:33.300 --> 00:00:36.518 Remember one number: one point eight five two.

00:00:36.518 --> 00:00:41.995 A nautical mile is one point eight five two kilometres: one minute of latitude.

00:00:41.995 --> 00:00:44.597 A knot is one nautical mile per hour,

00:00:44.597 --> 00:00:48.294 so it's one point eight five two kilometres per hour.

00:00:49.100 --> 00:00:53.792 For metres per second, divide kilometres per hour by three point six.

00:00:53.792 --> 00:00:58.417 Fifteen knots is about twenty-seven point eight kilometres per hour,

00:00:58.417 --> 00:01:02.840 or seven point seven metres per second. Roughly, halve the knots.

00:01:03.700 --> 00:01:07.606 Three nautical miles is about five point five kilometres. For height,

00:01:07.606 --> 00:01:10.451 multiply feet by zero point three zero four eight.

00:01:10.451 --> 00:01:14.413 Four hundred feet is one hundred and twenty-one point nine two metres,

00:01:14.413 --> 00:01:16.422 not exactly one hundred and twenty.

00:01:17.300 --> 00:01:21.924 Quick check. The wind is ten knots. Roughly how many metres per second?

00:01:23.100 --> 00:01:25.033 About five. Halve the knots.

00:01:26.500 --> 00:01:30.937 The International Standard Atmosphere is the reference day. At sea level:

00:01:30.937 --> 00:01:35.554 fifteen degrees Celsius and ten thirteen point two five hectopascals. Climb,

00:01:35.554 --> 00:01:39.092 and temperature falls about two degrees per thousand feet,

00:01:39.092 --> 00:01:42.330 and pressure about one hectopascal every thirty feet.

00:01:43.100 --> 00:01:48.165 Real days rarely match it. A hot day or a high site means thinner air,

00:01:48.165 --> 00:01:50.519 less thrust and shorter flights.

00:01:51.400 --> 00:01:56.310 Speed, distance and time. Distance on top, speed and time below.

00:01:56.310 --> 00:02:02.580 Cover the one you want. Time is distance over speed. Distance is speed times time.

00:02:03.400 --> 00:02:07.757 A survey leg of four thousand two hundred and twenty-six metres,

00:02:07.757 --> 00:02:10.774 at eight metres per second. Divide by eight:

00:02:10.774 --> 00:02:16.069 about five hundred and twenty-eight seconds. That's eight minutes forty-eight.

00:02:16.900 --> 00:02:22.419 Now fifteen minutes thirty, at seven metres per second. Convert to seconds first:

00:02:22.419 --> 00:02:27.803 nine hundred and thirty. Times seven: six thousand five hundred and ten metres,

00:02:27.803 --> 00:02:30.092 or six point five one kilometres.

00:02:30.900 --> 00:02:35.656 Recap: the right unit for the job. One point eight five two.

00:02:35.656 --> 00:02:40.957 Divide by three point six for metres per second. And seconds first.

00:02:41.800 --> 00:02:44.987 Final check. Four hundred feet. How many metres, exactly?

00:02:46.400 --> 00:02:48.620 One hundred and twenty-one point nine two.