Europa-List Digest Archive

Fri 10/22/21


Total Messages Posted: 4



Today's Message Index:
----------------------
 
     1. 01:42 AM - Flying In Rain (Area-51)
     2. 03:19 AM - Re: Flying In Rain (JonathanMilbank)
     3. 09:12 AM - Re: Flying In Rain (Bud Yerly)
     4. 10:54 AM - Re: Flying In Rain (Rick Moss)
 
 
 


Message 1


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    Time: 01:42:29 AM PST US
    Subject: Flying In Rain
    From: "Area-51" <goldsteinindustrial@gmail.com>
    Has anyone got an experience theyd like to share regarding flying the europa through either showers or very light rain and how these conditions may affect the aircrafts performance? For example a Schrieb Motorfalks stall speed is raised 5kt if water droplets collect across the wings surface during light rain... Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503590#503590


    Message 2


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    Time: 03:19:35 AM PST US
    Subject: Re: Flying In Rain
    From: "JonathanMilbank" <jdmilbank@yahoo.co.uk>
    One of my friends, who has a few hundred hours on my Europa, was a former chief gliding instructor examiner for the Northern UK and has come close to breaking a record or two, IIRC. So I've just phoned him to ask your question and his reply in essence was "It's not." The reason he gave is that while a Europa's wing is pretty darned efficient when compared with other powered light aircraft, it's nothing like as critical as wings on some glider types. We've both flown through light rain on several occasions, but of course the rain droplets blow off the wings almost instantaneously after passing through a shower. In such circumstances neither of us has ever noticed any change or deterioration in the aircraft's handling. FWIW we're both retired commercial pilots. Many years ago I was flying my Europa down the east coast of the Shetland Islands and got caught out by heavy rain which resulted in being almost IMC and flying at reduced speed 80 knots along the cliffs for about 20 minutes. My biggest fear was carburettor ice; not any worry about aerodynamics. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503591#503591


    Message 3


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    Time: 09:12:28 AM PST US
    From: Bud Yerly <budyerly@msn.com>
    Subject: Flying In Rain
    Short answer: Yes, I have flown through light rain fairly often in the Europa. I flew with a client with a dusty dirty aircraft to do a "jiffy wash" throu gh the local stable air rain showers to clean off the grime. Vis was a bit below 3 miles so heavier than we should have flown through. In slow flight, one can see quite clearly (because of the dirty water) the laminar to turbulent transition and then as the stall is approached the sep aration point during slow flight and the affect on stall speed is slight bu t noticeable. The drag is clearly increased. Air was smooth. The cruise speed difference is about the same as flight with grime on the w ings. (The splash of water hitting the wing tends to add a surface roughne ss affect and the waves of water disturbs the laminar flow leading to a sta ndard roughness effect on the airfoil which normally increases cruise drag and decreases the stalling angle slightly. See "The Theory of Wing Section s" as an easy way to see the effect in a wind tunnel or the papers referenc ed below.) For a well polished wing the rain creates a splash which is similar to stan dard roughness. That does increase the stall speed slightly in a high camb er airfoil (Motor Glider) and is slight in a more symmetric airfoil (XS sho rt wing). The stall warning characteristics clean or dirty in my brief enc ounters did not seem to change significantly. However, in heavy rain, rese arch indicates that the stall is affected by the sheets of water over any w ing. Stall characteristics in heavy rain would be difficult to flight eval uate in my opinion. Normal techniques for turbulence penetration should be considered, that is slow down to Va. Commercial aircraft equipped with bo undary layer control, slats, flaps and other high lift devices are affected differently by rain than say a GA aircraft. What is noticeable is the down draft under a rain cloud as the rain drags a ir along with it downward creating a downdraft that in a rear tail (CG forw ard of the Center of Pressure) aircraft creates turbulence and pitch change s in some aircraft. The tail in a downdraft normally increases its downfor ce compensating for the loss of wing angle of attack and the pilot just fee ls the bumpy air. Canards are affected differently as the lifting canard l oses lift along with the wing and a noticeable nose down pitch occurs. Longer Answers: There was much work done in the late 80's on downdrafts, microburst, and op erations in rain by many different government and research agencies. Opera tionally in an aft tail aft aircraft like the Europa, in rain squalls, I ad d 5 knots (65 vs 60 or half the gust factor) for simple rain from cumulous clouds which normally occurs with shifty winds of anywhere from 5-10 knots anyway. Vis is not a major problem in the Europa with a polished windscree n, it is the downdraft and turbulence issue I'm concerned about as a pilot. I have always avoided heavy rain in approach and landings in GA aircraft as they don=92t have the mass to penetrate and can=92t climb or accelerate as well as higher performance aircraft. In flight, I have flown through he avy rain once as a demonstration for my wife to satisfy her query of why we don=92t fly through small cumulous buildups that look pretty. It was grea t, clear smooth air approaching the vertical column and then, instant turbu lence, blinding heavy rain, and poof clear air again. Her comment was =93W e don=92t need to do that again=94. I do not land in heavy rain as it is n ot worth the potential landing mishap in a GA aircraft due to squirrely win ds, downdrafts and lateral gusts. I have plenty of divert strips in my are a. Unfortunately, operationally in the military I had to land in heavy rai n a couple of times. The F4 just plowed through it as it was not microburs t rain. I lost a good friend who was caught approaching the final approach fix at night in his F106 when he hit a microburst. The central air data c omputer went out, and the rate of sink was greater than full afterburner. He hit the trees on a hilltop just beyond the final approach fix in a full nose up attitude. Since I have a turbo, rain ingestion is not an issue for me. However, a 91 2ULS may see slight engine performance differences and the extra moisture i n the area of carb icing conditions, should be considered. (Not to spark a new thread, carb heat for the 912ULS in the stock Europa XS is not a bad i dea and should be considered seriously.) For those who care to research: I suggest a simple google search on "Effects of rain on stall speeds of air craft" and read many of the fine papers done on the subject. Aerodynamicis t's Hansma and Craig did a lot of work in the late 80s. If you recall, ther e were a number of accidents due to microburst rain downpours and interest peaked in that time frame. Recently, I read a paper done in 2016 by a Chin ese student (Wu?) on his Doctorate out of Beijing University of Aeronautics . A very good research paper summarizing the issues and affects of rain on an airfoil with many references. Also, the US Transportation Department i n the 80s did a number of grants resulting in papers that are also quite go od. See Airfoil Performance in Heavy Rain: Transportation Research Record No. 1428 - Public-Sector Aviation Issues Graduate Research Award Papers 199 2-1993 (trb.org)<https://onlinepubs.trb.org/Onlinepubs/trr/1994/1428/1428-0 04.pdf> for one example. One thing I was surprised at was the low camber laminar flow airfoil normally has a sharp stall break but in rain actually smoothed the stall break allowing a smoother transition to the stall and in to the deep stall. However, the high camber laminar flow airfoils were aff ected more in drag and early transition of the laminar flow to turbulent fl ow was significant. (Note that turbulent boundary layer is not a separated or stalled flow.) Many of these papers show the results on the airfoil al one and I was disappointed in that the plain or simple Fowler flap lift cur ve changes were not discussed. I didn't see much in actual in-flight testi ng of different aircraft. Just accident results. Just my observations, Bud Yerly -----Original Message----- From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr onics.com> On Behalf Of Area-51 Sent: Friday, October 22, 2021 4:42 AM Subject: Europa-List: Flying In Rain <mailto:goldsteinindustrial@gmail.com>> Has anyone got an experience they=99d like to share regarding flying the europa through either showers or very light rain and how these conditio ns may affect the aircraft=99s performance? For example a Schrieb Mot orfalk=99s stall speed is raised 5kt if water droplets collect across the wing=99s surface during light rain... Read this topic online here: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fforums.ma tronics.com%2Fviewtopic.php%3Fp%3D503590%23503590&amp;data=04%7C01%7C%7Cf 7f215571e5d4ae0634908d995387bab%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0% 7C637704892147660069%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2 luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=kcOXVRVuu3zIw0VTd0A Eb3Y07ZegxpVT9ETpmx6banY%3D&amp;reserved=0 %2Fwww.matronics.com%2FNavigator%3FEuropa-List&amp;data=04%7C01%7C%7Cf7f2 15571e5d4ae0634908d995387bab%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C6 37704892147660069%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luM zIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=leB%2B6RB0ncFg8XkGP39f %2BMIbQxBV1SBL34GukP%2BlBpU%3D&amp;reserved=0 %2Fforums.matronics.com%2F&amp;data=04%7C01%7C%7Cf7f215571e5d4ae0634908d9 95387bab%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637704892147660069%7C Unknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiL CJXVCI6Mn0%3D%7C1000&amp;sdata=QUvexUrRdD27Zd0CwNaSnRx4rECTMA3YNiT3Zrl6MU 4%3D&amp;reserved=0 %2Fwiki.matronics.com%2F&amp;data=04%7C01%7C%7Cf7f215571e5d4ae0634908d995 387bab%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637704892147660069%7CUn known%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJ XVCI6Mn0%3D%7C1000&amp;sdata=ie7ZyramVTVX7s7uU3gUiGX2i1wmJcrp4xuAPJTA%2B7 8%3D&amp;reserved=0 %2Fwww.matronics.com%2Fcontribution&amp;data=04%7C01%7C%7Cf7f215571e5d4ae 0634908d995387bab%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637704892147 660069%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6 Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=y2E2ffODhkAH2WvcPv79URjypBWRDTuCR ZfRZJPF58M%3D&amp;reserved=0


    Message 4


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    Time: 10:54:28 AM PST US
    Subject: Re: Flying In Rain
    From: "Rick Moss" <Rkwmoss@gmail.com>
    I often fly through rain (I live in Britain!); I find that the engine temps drop, presumably due to the rain on the radiator and oil cooler, but notice no major difference in cruise speed. I have not explored the stall in such conditions, so cant say anything much about that aspect. On Sunday just gone, I spent over 30 minutes in moderate rain; no engine issues but I am wary about icing with the reduced coolant temps on the skydrive carb heaters, and I tend to work the engine a little harder to ensure CHTs remain above 80C. I do find that flight in rain erodes the paint on the backside of the prop blades requiring more regular repainting. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=503595#503595




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