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Flying in the rain - a warning


norman
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I don't normally cut and paste posts from other places but here is a little missive that I am sure the author wouldn't mind being passed on as it is safety related.

Yahoo PPG Pilots Forum

I do not normally share embarrassing incidents but a few weeks ago i had

> a serious crash that could have been very nasty. The reason i am sharing

> this is i do not want any other pilots to make the same mistake i did.

> I am okay but my paramotor chassis was mangled.

>

> I have frequently flown in rain and until recently believed that

> reflexed wings were safe in wet weather. I am a comp pilot and have

> flown in some rather extreme conditions both in the UK, Czech Republic,

> Poland and Chile.

>

> After getting very frustrated with the typically crap UK weather, I took

> off in marginal weather and after 15 minutes flew right into a very

> heavy downpour . The rain was so heavy i decided to return to my

> airfield - on final approach i applied full slow landing trim and some

> moderate brake pressure - and promptly entered into a full parachutal

> stall from about 40 ft. I instantly released brakes and hit the bar

> hard in an attempt to get the wing flying - this action may have saved

> my bacon. With insufficient height to enable a full recovery i impacted

> pretty hard. After doing some research i have noted the following which

> might offer an explanation behind my stall:

>

> In heavy rain a thin water film forms on the upper canopy surface. This

> water comes from the residue of the raindrop that is not splashed back.

> The raindrops form small impact craters and surface waves in the water

> film, which roughens the aerofoil surface. This creates additional

> surface friction and disruption of the boundary layer.

>

> In addition the mass of the wing increases as they absorb water. If we

> assume the wieght of the wing plus the mass of air inside at 12kg in dry

> conditions, then cover it with water you massively increase its mass and

> increase your rate of descent (assuming constant RPM/Thrust). The wing

> also becomes heavy and sluggish.

>

> The net effect is a loss of lift, an increase in drag and a premature

> separation of the boundary layer, all of which have negative effects on

> a wings performance - stall territory.

>

> These are most pronounced in slow high-lift wings such as paramotor

> wings - and high lift set ups which we use when landing e.g with

> trimmers on slow and with the brakes applied. The effects are most

> severe at higher angles of attack, which is the paramotor pilots normal

> configuration while landing.

>

> Our wings can experience a decrease in maximum lift of up to 20

> percent, an increase in drag of up to 40 percent, and perhaps most

> importantly, a huge decrease in the stall angle of attack.

>

> An "average" aerofoil typically stalls around 17 degrees, thus one with

> a wet surface could stall at just nine degrees angle of attack.

>

> Be warned!

>

These are the observations and experience of an experienced parafoil wing flyer. The precise AOA numbers probably don't mean a lot when you are flying your wing, the message is clear though. If your wing gets wet be very aware that it may not fly at all like the one you are used to. It may be intolerant of brake application - stall easily/earlier than you expect and set up high rates of descent such as described. I will leave it to others to comment about technique. Observe - Anticipate - - Survive. :wink:

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Well spotted Norman.

We had damp wings whilst freeflying at Monte Carlo and were told we'd find re-inflation alot slower if collapses or tuck occured.

Another point that jumps out from the script is the frustration because of crap weather and flying whilst conditions were marginal. I read somewhere that these types of accidents happen to the more experienced when a little complacentcy sets in. Not so much a worry for students as they wont want to or be allowed to. 50 to 100 hours experience can be a risky time apparently.

Dave

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Don't fly when it's wet - -simple :roll:

Where there's a doubt there's no doubt, don't fly. It works for me, there is always another day.

OK it may be 4 weeks hence but I want to enjoy this pastime, maybe I'm not quite as desperate for airtime now.

Fly safe,

Alan

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Good of you to share your experience with us all it might help prevent another ....

self discipline is a Must in all aviation....never be tempted.....(easier said than done I know)

never fly in conditions you are not happy with wind or rain is a difficult one to predict but the signs are always there Ive been tempted many a time and when other people are flying its hard to walk away...(peer pressure and all that) I reckon its all about learning self preservation...

Hey ho :coptor:

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Good of you to share your experience with us all it might help prevent another ....

self discipline is a Must in all aviation....never be tempted.....(easier said than done I know)

never fly in conditions you are not happy with wind or rain is a difficult one to predict but the signs are always there Ive been tempted many a time and when other people are flying its hard to walk away...(peer pressure and all that) I reckon its all about learning self preservation...

Hey ho :coptor:

And good training :!:

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  • 4 weeks later...

How much rain, is it a shower that you can fly out of and avoid, is it frontal and continuous or light and intermittent? If frontal in nature perhaps your decision to fly might have anticipated landing when the rain started. If it is related to showers then it may be a convective day - you will have considered the development of showers before takeoff and should have a plan.

These are evaluations and decisions to be made by the aviator under the wing but if you believe that the performance/safety of your wing is, or may be compromised, then a precautionary landing sounds like a wise course of action to me.

Different wings are affected in different ways aren't they. A high performance/sport aerofoil section may be more vulnerable than a DHV1-2 wing - experts please comment. Having the 'right' pilot underneath the 'right' wing avoids the 'undesirable' scenario of a low experience pilot being caught in a heavy rain shower. Another reason why we accumulate our experience under wings that match our abilities, not the current fashion or mis-timed aspirations?

What do the Tip to Tip '08 team think, they flew in a bucketload of rain at times? :lol:

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its a ace place to fly I go there every year but never managed to get my paramotor over...so have only freeflown....one day I promise myself to paramotor there Ive got my eyes on the paraportator...for a way of doing it....without breaking the bank

http://paraportator.com/gallery/

Looks good, what price does it come out at, I couldn't find any price on the website?

Dave

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