Can Passenger Jets Land in Heavy Rain?
Can passenger jets land in heavy rain?
Yes, generally speaking commercial passenger jets are capable of landing perfectly safely when it is raining heavily. The aircraft’s jet engines are designed to be able to operate flawlessly whilst ingesting huge amounts of water from rain. However, in some circumstances, the aircraft may not be able to land whilst it is raining very heavily. This isn’t because of the rain itself, rather cause and effect of the heavy rain. Very heavy rain can be an indicator of other weather phenomenon which pilots are trained to avoid. Such circumstances include:
Low Visibility Caused by Heavy Rain
For the vast majority of the flight, the pilots are using the aircrafts instruments to fly the plane and only revert to visual references shortly before landing (usually for about the final 500ft). Therefore, moderately reduced visibility due to heavy rain isn’t a problem. However, to land the aircraft manually, the pilots require a horizontal visibility of 550m. If the rain is extremely heavy, visibility may reduce to below this level. This then requires the pilots to carry out an ‘auto-land’ where the aircraft touches down with the autopilot engaged. Some aircraft and airports do not have the facilitates to support an ‘auto-land’ and therefore landing at the affected airport may not be possible.
Rain Caused by Thunderstorms / Cumulonimbus Clouds
Very heavy rain is often caused by a thunderstorm or cumulonimbus clouds. Whilst the heavy rain probably won’t stop the aircraft from landing safely, other hazards associated with a thunderstorm may well do.
Flying directly through or within the vicinity of a thunderstorm can result in windshear. Windshear is the sudden change in direction or velocity of the wind. If an aircraft encounters this, it can result in control difficulties and could even result in the aircraft stalling. Pilots will therefore avoid flying near thunderstorms where possible. This would include delaying the approach and landing phase if a thunderstorm was overhead the airport.
Thunderstorms also produce microbursts which can result in a very strong current of downward air which can push the aircraft towards the ground or result in a very rapid change in the aircraft’s airspeed. Microbursts can be associated with heavy rain showers. This is another reason why pilots avoid flying near thunderstorms.
Contaminated / Flooded Runway Caused by Heavy Rain
If the rain is very heavy and sustained, it can result in standing water building up on the runway. Whilst most aircraft can travel through water on the runway to a certain depth, it can get too deep. If it gets too deep, the aircraft is unable to brake sufficiently to stop the aircraft on landing. If necessary, the pilots would receive regular updates on the state of the runway and delay landing if needed.
Can Pilots Detect Heavy Rain?
Yes, all commercial passenger aircraft are fitted with a weather radar which detects the movement of water droplets. Pilots are therefore able to see exactly where the rain is located and how intense it is. They can therefore plan to avoid the area if they believe the cloud producing the rain is going to result in strong turbulence.
Is Heavy Rain Turbulent?
The rain itself doesn’t result in turbulence, but the cloud producing the heavy rain can produce strong turbulence. Pilots therefore seek to avoid clouds which are producing heavy rain showers. Clouds associated with short sharp showers (towering cumulous and cumulonimbus) tend to be much more turbulent than clouds associated with heavy, but sustained rain (nimbostratus).
What happens if the plane can’t land?
Pilots will be aware of the potential for heavy rain or thunderstorms to occur at the destination and may choose to take some extra fuel if they feel it is needed. Very heavy rain is typically associated with short lived showers and thunderstorms that usually pass through quickly. Extra fuel will allow the pilots to delay the approach and landing through taking up a holding pattern (sometimes referred to as a ‘stack’) away from bad weather such as thunderstorms. When the bad weather is clear they can then make the approach and landing.
If the weather doesn’t clear as quickly as hoped, the pilots may elect to divert the aircraft to another airport where the weather is better. The aircraft is always loaded with enough fuel to be able to fly to another airport in case it can’t land at the destination for whatever reason.
If you found this article of interest, check out our page on ‘Are thunderstorms dangerous?‘.