Wet Weather Considerations

For local flying near home base there is less concern as a landing is only minutes away but that is assuming that the cloud base, the visibility and the cross-wind are acceptable. Going cross country? If the destination forecast indicates weather at the minimums, then having holding fuel or enough to divert to an acceptable location is that plan B. 

One usually associates rain with lower cloud bases. In the cockpit rain can be a real concern to visibility as few GA aircraft have windscreen wipers. Trying to make a decent landing can be hard with rain belting down and the runway centre line hard to see. Even the taxiway can be hard to see with water on it. 

Thunderstorms are something to avoid. Cloud and the turbulence that they create has the potential to create spatial disorientation and loss of control or even break up an aircraft in flight. Avoid a thunder storm by at least 20 nautical miles. 

Wind gust turbulence could well dictate a higher climb out or landing speed. Nothing worse than being on final and finding that falling rain is accompanied with a down draught that makes the aircraft start to descend below its approach path. 

The average pilot would prefer to not fly in wet conditions. The weather doesn’t read the forecast and work to it. Adverse weather could well roll in before or after the Bureau of Meteorology forecast says it is due.

A VFR pilot should treat wet weather conditions with caution 

For those pilots flying cross country in wet weather that is the time to have an acceptable alternate pre-planned and not too far away. If there is only an inter of light rain then it may be possible to fly through it. If a pilot flies up to an inter and can see countryside on the other side then they would be able to fly through it. 

If the down burst is denser then that is the time to fly around it or divert. A wall of water coming your way is not good to fly through. Visibility considerations aside you have no idea how far it is to the other side. 

Rain is associated with clouds and for a VFR pilot to fly in clouds is a no-no. Too much chance of becoming disorientated and falling out of the clouds and flying into the ground or the aircraft to break up. Beware of flying forward when the ground and the clouds join. A pilot needs to have a good idea of the various cloud types and how they might affect flying. 

For a pilot landing an aircraft on a wet runway, things can get interesting. Less stopping ability with hard braking due to aquaplaning is a possibility. Runway and taxiway guidelines become hard to see. The chance of going off the edge of a taxiway is increased. A wet grass runway or gravel surface will mean a longer take-off run as the wet surface slows the aircraft down. Grass strips can be slippery when brakes are applied in a landing. 

For the pilot, a wet jacket could see the inside of the cabin windows will mist up. A hurry to get inside the shelter of the cockpit can well mean forgetting to remove the pitot cover or remove chocks. 

Wet weather can also increase the possibility of water getting into the tanks, particularly of an aircraft that has been static in rainy weather. Double check all drain points. Get a full measure of a drain cup or tube. 

We can usually associate driving rain with strong winds. What is the demonstrated cross wind limit for the aircraft? Taxiing a low wing aircraft in winds is safer than a high wing aircraft. 

How will rain affect an aircraft in the air? Water on the wing will help slow the machine down particularly a laminar flow wing plus add weight. And what of the engine? In the UK a Piper turbo Saratoga had an engine failure when the paper air intake filter got so wet from heavy rain that it collapsed and blocked the intake. Application of alternate air was left too late to get an engine restart. Moisture in the air and low temperatures are a recipe for carby ice in a carburettor engined aircraft. If cold enough, snow and icing may develop. 

Another problem with flying in rain is water potentially getting into your avionics. Time to seal up some leaks. Rain water getting into a pitot tube will give erratic readings on the ASI. The main thing with heavy rain is to maintain adequate visibility both horizontally and vertically. 

When flying in wet weather conditions there is a saying: ‘Sometimes it can be wise to be on the ground drinking coffee and talking about flying than being in the air and wishing that you were on the ground drinking coffee.’

Instructor Tip of the Month

Ever forgotten to cancel a SARtime? Lots have. There must be a dozen ways to try and remind oneself to cancel the SARtime. One way is to put a dab of blue tack on the instrument panel and fix a small piece of paper to it with the words ‘SAR 4pm’ or whatever the time is to cancel it by. A good visual reminder. Simple but it works.