How to Calculate Flight Enroute Time

Filed Under (Flight Operations) by steven on 05-12-2009

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Yes, we only just fly a simulation but it does no harm if we learn how to calculate the enroute time that are very useful when we gonna fill the flight plan. Okay, here we will discuss how do we calculate our Flight EET (Estimated Enroute Time) to our destination. Thanks to Danang Pariadji who gives the formula.

First, we must determine the aircraft’s True Air Speed or TAS. There’s several ways to calculate the TAS, but i will only use two formula.

  • Take a half of your altitude and add it to your Indicated air speed. For example: 280 Knot IAS at FL350. Then 350 / 2 = 175 –> 280 + 175 = 455 Knot TAS.
  • Divide Your altitude by 1,000 and multiply by 5. And Add the outcome to your indicated air speed. For Example: 35,000 / 1,000 = 35 * 5 = 175. Then 175 + 280 = 455 Knot TAS.

Voila! Now we have our True Air Speed. Now here is the formula to calculate our Estimated Enroute Time…

(Range / TAS) * 60 + 20. For Example: We take place from WIII (Soekarno-Hatta Int’l Airport – Jakarta) to WARR (Juanda Int’l Airport – Surabaya). The distance between these two airport is: 375 nm, Our TAS is 455 at FL350. Now we have all required data…. So the calculation is: (375 / 455) *60 +20 = 69.45 minutes or 1 hour 10 minutes.

This time estimation will be influenced by many factors such as wind factors, etc. And of course it depends what type of aircraft that you will use. Example above is using Boeing 737 classic. And it’s for Simulation use only :)

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How to Read METAR Information

Filed Under (ATC Operations, Flight Operations) by steven on 09-09-2009

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METAR or MÉTéorologique Aviation Régulière or Aviation Rutin Weather Report is format for weather reporting. METAR is used by the pilots to know the weather conditions, winds conditions at an aerodrome where they will conduct the flights. Raw METAR is a very known format in aviation for weather data transmision. It’s also an ICAO standard.

METAR reports typically come from airports or permanent weather observation stations. Usually METAR is generated once an hour if there is no significant weather changes.
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How to read it?

I’m gonna use several METAR report for example.

WSSS 090730Z 21009KT 170V260 9000 FEW020TCU BKN300 32/25 Q1008 NOSIG

Okay, WSSS, Changi airport – Singapore.

090730Z = METAR was made at 09 (date), 0730Z (time)

21009KT = Wind from 210 degree at 09 knots (wind’s speed)

170V260 = indicates the wind direction is varying from 170° through 210°  to 260°

9000 = indicates the visibility is 9000 meters

FEW020TCU = Few clouds at 2000 feet, TCU is Towering Cumulus (Cumulus cloud that have potential to become into a cumulonimbus within a short time period)

BKN300 = indicates broken cloud at 30,000 feet

32/25 = temperature is 32 degree and dewpoint is 25 degree

Q1008 = QNH or altimeter setting is 1008

NOSIG = No significant changes

Next is

LBBG 041600Z 12003MPS 310V290 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M04/M07 Q1020 NOSIG 9949//91

The rest is same as above, Let’s discuss the bold letters only.

12003 = wind from 120 degree with speed at 03 Meter per Second

R04/P1500N = Runway Visual Range (RVR) at Runway 04 is 1500 meters with no significant changes

R22/P1500U = Runway Visual Range (RVR) at Runway 22 is 1500 meters and rising

+SN = Snow falling at heavy intensity

OVC050 = Overcast at 5000 feet

M04/M07 = Temperature is -04°C and dewpoint is -07°C

9949//91 =

  • indicates either a specific runway (eg. “25″=Rwy 25 or “25R”; “75″=Rwy 25L – adding 50 will indicate Left Runway) or all the airport’s runways (”99″)
  • “4″ means the runway is coated with dry snow
  • “9″ means 51 to 100% of the runway are covered
  • // means the thickness of the coating was either not measurable or not affecting usage of the runway
  • “91″ means the braking index is bad, in other words the tires have bad grip on the runway.

Note: For North America use Altimeter or code “A” in their altimeter setting (eg. “A3006″)

Other METAR Codes:

  • CB = Cumulonimbus cloud
  • TSRA = Thunderstorm, Rain at the area
  • BECMG = Becoming
  • CAVOK = Ceiling And Visibility OK

Regard’s

Steven Airspace

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