A look at how commercial aircraft fly in rain

How do planes fly in the rain? 5 things pilots do

It’s raining outside, and you wonder how in the world planes can fly in such conditions. Can commercial aircraft even land in heavy rain? As it turns out, landing a plane in the rain is not as dangerous as you may think. Pilot’s have a wealth of tools available to them, and modern commercial airliners are completely safe to fly in all rain conditions.

In this article, we will explore how pilots deal with bad weather and what measures are taken to ensure a safe landing. If you wonder what airline pilots do differently to fly in the rain, or even if planes have windscreen wipers? — you’re in the right place!

So next time you’re stuck at the airport watching planes come in during a storm, you’ll have a little better understanding of what’s going on behind the scenes!

How planes fly in the rain — 5 thing’s pilots do

Engine protections

Arguably at the top of any pilots list — having working engines! It is also a common question nervous flyers bring up, how safe are the engines in bad weather? The truth is, very!

Aircraft engines are tested to a hugely demanding schedule, and this includes simulating horrendous weather conditions. During initial testing, engines are run with damaged blades, have frozen chickens launched into them, and are pumped full of water to simulate tropical storms.

With modern commercial airliners, many engine protections are automatic — the engine management computer (known as a FADEC) reacts to the changing conditions. However, there is normally a manual backup methods airline pilots will also when flying through heavy rain, forcing the aircraft to use continuous ignition.

Engine Ignition
Once started, jet engines are self-sustaining. However, with extremely heavy rain, there is a concern that part of the combustion process could be interrupted. Pilots can manually switch the engine igniters on in-flight, to force the engine igniters to continually run, ensuring that the engines remain lit regardless of the water ingress.

Rain repellent

Many people will have experienced driving through heavy rain, and how difficult it can be to see out of a flooded windscreen.

When flying in an aircraft, this problem can be much worse as the speeds involved are much higher, and windscreen wipers aren’t capable of clearing the water. (Yes. Planes do have windscreen wipers — more on that later!)

Rain covered windshield

So, how do pilots see out of the window during heavy rain? One little known feature commercial aircraft have fitted is rain repellent systems!

Located in the cockpit and fitted with a quantity gauge, pilots will check there is sufficient liquid before flights where heavy rain is expected. This commercial grade liquid is hydrophobic, helping to repel water to keep the aircraft windscreen clear without using the wipers:

  • This liquid is separate to treatments applied to aircraft windshields before flight.
  • Each pilot has a small button to treat their side of the windshield.
  • Once pressed, a timed-release of hydrophobic rain repellent sprays onto the windscreen.
  • This ensures the optimum amount of rain repellent is dispensed, and will keep the windshield clear of rain for around 30–60s.
Airplane windscreen wiper controls alongside rain repellent button

Windscreen wipers

Do planes have windshield wipers? Yes. They can be useful during the takeoff and landing in heavy rain. However, they come with severe limitations!

  • Windscreen wipers are fitted on the captain and co-pilot’s windshields and are independently operated.
  • Unlike car windscreen wipers — with automatic sensors and multiple speed settings — aircraft windscreen wipers are heavy-duty and low tech!
  • Normally aircraft windscreen wipers have only a few settings, slow, fast and off.
  • Aircraft wipers cannot be used in light rain, as they may scratch the windscreen
  • Windscreen wipers can only be used during takeoff and landing, as they often have limits on the aircraft speed.
  • Normally, windscreen wipers can’t be operated above speeds of approximately 250 mph (ca. 402 km/h).
  • Due to the heavy-duty nature, and motors mounted immediately above the pilots heads, aircraft windscreen wipers are typically very noisy.
  • As a result of the noise, and because aircraft windows have hydrophobic coatings and rain repellent options, many pilots don’t use the windscreen wipers

Thrust reversers

Pilots will always calculate takeoff and landing performance based on the latest aircraft weight, and the prevailing weather conditions at the time. During takeoffs in heavy rain, the amount of water sitting on the runway, and additional safety margins for stopping distances are all factored into the pilot’s preflight calculations.

It’s a similar case when pilots land in heavy rain. One tool that helps planes stop safely is thrust reversers. Thrust reversers are fitted to virtually all commercial aircraft, and when used redirect some of the engine’s thrust forwards, helping to slow the aircraft and reduce the wear on the brakes.

While the use of thrust reversers during landing is normal practise, many airfields require pilots to only use these on the lowest settings, due to noise restrictions. Thrust reversers can be exceptionally loud!

This restriction on thrust reverser use is removed during bad weather, such as heavy rain. During more challenging conditions, stopping the aircraft as soon as possible is a higher priority than noise complaints. As a result, pilots landing in heavy rain will select maximum reverse thrust, hugely reducing stopping distances.

Interestingly — by using the full capabilities of the aircraft — aircraft frequently will stop in a much shorter distance during heavy rain landings, than on dry runways on clear days!

Delta aircraft landing in rain

Firm landing

Many frequent fliers will remember the last time they had a bumpy landing — it happens to the best of us! However, when landing the aircraft in heavy rain, pilots will deliberately target a slightly firmer touchdown.

The reason pilots aim for a heavier landing in rain is to stop aquaplaning.

  • On runways with standing water, there is a risk that by lightly touching down, the aircraft wheels will skid along the surface of the water.
  • Aquaplaning temporarily prevents the aircraft braking anti-skid systems from working correctly, as the coefficient of friction is much lower than wet tarmac
  • Very light touchdowns can also stop the aircraft spoilers and automatic breaking system from engaging promptly, as the trigger for their engagement is based on pressure
  • At normal landing speeds of around 150 mph (ca. 241 km/h), just a few seconds of aquaplaning can increase the landing distance required by several hundred meters or more
  • Pilots are taught to ensure a firm landing, to break the surface of the water, and ensure quick engagement of all the aircraft stopping devices

Flying in the rain: Summary

While many people have a fear of flying in heavy rain or bad weather, commercial aircraft are well-equipped and pilots well-trained to deal with this. The world’s largest aircraft manufacturer, Airbus, summarises flying in heavy rain neatly:

The ice and rain protection system allows unrestricted operation of the aircraft in icing conditions and heavy rain.

Airbus

However, while there are no restrictions on operating aircraft in heavy rain, pilots have numerous aircraft features to help minimise any risks. These include engine features, such as continuous ignition to ensure engines don’t flame out during heavy rain, and maximum reverse thrust to help slow down on slippery runways.

To help pilots takeoff or land in heavy rain, many commercial aircraft are fitted with windscreen wipers and rain repellent systems. Finally, the pilots will adjust performance calculations and even their flying technique, performing firmer landings to ensure the aircraft stopping systems engage promptly.

If you are reading this article simply because you are curious, or if you are a nervous flier, we hope this has demonstrated how aircraft are capable of flying in heavy rain. Passengers can take reassurance that while flying in the rain can be challenging, pilots are well-trained to deal with it. They have a variety of tools at their disposal, and, if there is a chance of storms or heavy rain showers, they will take extra precautions.

The bottom line: Can planes land in the rain? Yes, they can, and pilots have a wealth of experience and training to make this a routine event.

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Josh
Josh

Flyingbynumber’s Resident Airline Captain — Josh

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