Clearly within a Sim this is not the most important thing. However I shall explain still the concept and how you can prepare yourself in real life and how you could do basically the same within the Sim.
A small word of warning
While there is a general rule set for aviation, there is also smallish (or not so smallish) difference between countries. Therefore in real life you should control the rules of the countries where you will fly (like the different airspaces / altitudes). Being myself from Switzerland, the rules described here are from my country or countries nearby. I took also the US rules for airspace & cloud separation.
IFR vs VFR
IFR means Instrument Flight Rules, meaning you can’t really fly where and how you want, it’s the ATC which will coordinate your flight and you will rely mostly on the instruments to follow the instructions. In this case visibility is not as important, while you must have visibility for taking off and landing (as nearly none of the GA plane can auto-land currently).
VFR on the other side means Visual Flight Rules and this is what most private pilots do use. VFR means you must always have visibility, be out of the clouds and ideally be able to know where you are based on what you see around you. You are not allowed to cross clouds and need to have a separation between clouds and the aircraft. In this kind of flight you may actually never need to use the radio (while it’s certainly good practice even in non-controlled airfields).
Due to the difference of the 2 kind of flight I will talk only about VFR and what is called VMC (Visual Meteo Conditions).
Main issues for VFR
There is basically 2 main issues for any VFR flight: wind and visibility.
Wind is relevant for a couple of reasons:
- Each aircraft have a defined limit of the crosswind component allowed, meaning if you have side wind (cross wind) which exceed the specified maximum, you may not be able to take-off / land safely as your tail will not be able to compensate for the cross wind component. Honestly even at 1/2 of the max cross wind, most pilots will have troubles in real life. Why? Simply because wind is hardly laminar (constant and without turbulences) meaning you will need to fight all the time to compensate the wind and turbulences.
- Turbulences can be an issue too, and you will have those even with a constant wind as soon as the ground is not flat. Even a building near the runway will produce turbulences which may make your life as pilot harder. Turbulences are also what makes you passengers (pax) sick. Having sick people on board (vomiting or even just complaining), and having to fight to fly / land / take off, is certainly not fun.
- Finally there is a speed / G force issue. Each aircraft have a max G force they can sustain without having damages. With turbulences the G forces will increase. As G forces do increase with speed, you will have to fly under a given speed (VA) to ensure you don’t over-stress your aircraft.
While wind cannot be checked all the time (in flight you will feel the turbulences but not so much the wind itself besides if you compare your indicated airspeed and the ground speed on your GPS) what you will certainly spot is the visibility issues.
Visibility can be reduced to:
- Clouds (low level clouds for example)
- Precipitations (snow, rain, hail, …)
A lower visibility means you will hardly see in front of you if there is other aircrafts or some obstacles (mountains, cables, antennas and more). For VMC bellow 10,000 ft you must have 3sm or 5km of visibility. Less than that is now allowed. Within a CTR (controlled traffic region) you may have a much smaller visibility distance if you get a SVFR (Special VFR) clearance, however you would still need the normal VMC conditions outside of the CTR. US Min visibility and clound clearance can be found here.
While you would be allowed to fly above clouds (for example you find holes in clouds and you climb above), you would not be allowed to cross them even in case of engine failure. Therefore VFR pilots tends to not fly above cloud layers. In some countries like UK you may have spots where you are allowed to cross cloud layers as VFR pilot under some circonstances with the appropriate training.
Why you are not allowed to cross clouds in VMC? There is two reasons for it, first within a cloud you may have strong thermic wind and without visibility you could get totally disoriented and lose the control of the aircraft. The second reason is also the reason why you must keep a separation (a distance vertically and horizontally) with the clouds: as VFR aircrafts are not even required to have a radio on board, you cannot really ensure separation without other aircrafts (being VFR or IFR), therefore you must have a given distance to allow yourself and others to avoid in air collisions.
Therefore to resume the visibility issue, which is actually the usual point which would make your VFR flight cancelled: you must have enough vertical space between the lowest cloud layer, and the ground, and a good enough visibility (no fog).
Now that we know what are the two main issues while flying VFR (there is a couple of others like air pressure and temperature but we shall discuss those in a weight an balance article), we now need to check how we can get the information if we shall start and if we can land safely.
Each countries have their own official meteo reporting. Usually those can be reached on internet, but many countries do require a fee to have access to it. However with today technologies nearly everyone has a smartphone (being Android or iOS) and with this we can grab most if not all the information needed for free.
- Windy (on web: https://www.windy.com/ as App: Android or iOS)
- Aviation weather (on web: https://www.aviationweather.gov/)
- AeroWeather (Android or iOS)
- Meteoblue (on web: https://www.meteoblue.com/en/weather/webmap/beta)
What to check
- Check if there is some fronts (cold, warm, occlusions) passing by as those will be like walls you will not be able to cross
- Check the wind intensity and directions
- Check the precipitations (radar views for example)
- Check the ceilings
METAR and TAF
Those are what pilots (privates and non) are trained to decode and rely on. Each relatively bigger airport usually offer METARs which are the current situation at and around the airport. TAF are the previsions for the coming hours.
Tools like https://www.skystef.be/metar-decoder.htm may help you decode those.
Special meteo situation
Special events like tornado, hail, snow storm, or simply a storm are all a no-go for and specially VFR. Therefore I will not spend much more time on those beside saying if you get warnings of special meteo events then don’t fly!
What can be legally requested
In real life, a meteo briefing is mandatory. Therefore you must be able to show that you checked the meteo before starting. Screenshots, print out, self written summaries are all good to have with you.
- Make yourself a picture of the actual situation on the departure airfield / airport.
- Check out your en-route meteo, to ensure you are able to reach your destination
- Check out your arrival airfield / airport and prepare yourself an alternate which is a second airfield / airport where you could land in case of troubles on the first one.
- If there is clouds (which on my side of the world it’s nearly always), ensure you have enough separation between the ground and the lowest ceiling of clouds.
- Check the trend (is it improving? is it becoming worse? or is it stable?)
- If the weather is unsure… you are not convinced, then avoid to fly