 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
Area-51
Joined: 03 May 2021
Posts: 396
|
 Posted: Fri Oct 22, 2021 12:42 am Post subject: Flying In Rain |
 |
|
Has anyone got an experience they’d like to share regarding flying the europa through either showers or very light rain and how these conditions may affect the aircraft’s performance? For example a Schrieb Motorfalk’s stall speed is raised 5kt if water droplets collect across the wing’s surface during light rain...
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
 |
JonathanMilbank
Joined: 14 Apr 2012
Posts: 390
Location: Aberdeen area
|
| Posted: Fri Oct 22, 2021 2:18 am Post subject: Re: Flying In Rain |
|
|
One of my friends, who has a few hundred hours on my Europa, is 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 comparable." 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. In order to keep the engine temperature up at low speed, I put the flaps fully down to increase drag.
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
budyerly@msn.com
Joined: 05 Oct 2019
Posts: 288
Location: Florida USA
|
| Posted: Fri Oct 22, 2021 8:12 am Post 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" through 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 separation point during slow flight and the affect on stall speed is slight but noticeable. The drag is clearly increased. Air was smooth.
The cruise speed difference is about the same as flight with grime on the wings. (The splash of water hitting the wing tends to add a surface roughness affect and the waves of water disturbs the laminar flow leading to a standard roughness effect on the airfoil which normally increases cruise drag and decreases the stalling angle slightly. See "The Theory of Wing Sections" as an easy way to see the effect in a wind tunnel or the papers referenced below.)
For a well polished wing the rain creates a splash which is similar to standard roughness. That does increase the stall speed slightly in a high camber airfoil (Motor Glider) and is slight in a more symmetric airfoil (XS short wing). The stall warning characteristics clean or dirty in my brief encounters did not seem to change significantly. However, in heavy rain, research indicates that the stall is affected by the sheets of water over any wing. Stall characteristics in heavy rain would be difficult to flight evaluate in my opinion. Normal techniques for turbulence penetration should be considered, that is slow down to Va. Commercial aircraft equipped with boundary 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 air along with it downward creating a downdraft that in a rear tail (CG forward of the Center of Pressure) aircraft creates turbulence and pitch changes in some aircraft. The tail in a downdraft normally increases its downforce compensating for the loss of wing angle of attack and the pilot just feels the bumpy air. Canards are affected differently as the lifting canard loses 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 operations in rain by many different government and research agencies. Operationally in an aft tail aft aircraft like the Europa, in rain squalls, I add 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 windscreen, 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’t have the mass to penetrate and can’t climb or accelerate as well as higher performance aircraft. In flight, I have flown through heavy rain once as a demonstration for my wife to satisfy her query of why we don’t fly through small cumulous buildups that look pretty. It was great, clear smooth air approaching the vertical column and then, instant turbulence, blinding heavy rain, and poof clear air again. Her comment was “We don’t need to do that again”. I do not land in heavy rain as it is not worth the potential landing mishap in a GA aircraft due to squirrely winds, downdrafts and lateral gusts. I have plenty of divert strips in my area. Unfortunately, operationally in the military I had to land in heavy rain a couple of times. The F4 just plowed through it as it was not microburst 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 computer 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 912ULS may see slight engine performance differences and the extra moisture in 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 idea 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 aircraft" and read many of the fine papers done on the subject. Aerodynamicist's Hansma and Craig did a lot of work in the late 80s. If you recall, there 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 Chinese 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 in the 80s did a number of grants resulting in papers that are also quite good. See Airfoil Performance in Heavy Rain: Transportation Research Record No. 1428 - Public-Sector Aviation Issues Graduate Research Award Papers 1992-1993 (trb.org) 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 into the deep stall. However, the high camber laminar flow airfoils were affected more in drag and early transition of the laminar flow to turbulent flow was significant. (Note that turbulent boundary layer is not a separated or stalled flow.) Many of these papers show the results on the airfoil alone and I was disappointed in that the plain or simple Fowler flap lift curve changes were not discussed. I didn't see much in actual in-flight testing of different aircraft. Just accident results.
Just my observations,
Bud Yerly
--
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
Rick Moss
Joined: 21 Sep 2014
Posts: 96
|
| Posted: Fri Oct 22, 2021 9:53 am Post subject: Re: Flying In Rain |
|
|
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 can’t 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 CHT’s remain above 80C.
I do find that flight in rain erodes the paint on the backside of the prop blades requiring more regular repainting.
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
John Wighton
Joined: 18 May 2010
Posts: 241
|
| Posted: Fri Oct 22, 2021 11:27 pm Post subject: Re: Flying In Rain |
|
|
Very clean and polished aircraft + rain =no difference
Dirty aircraft + rain = flies a bit slower
Rick’s post is interesting, l have never repainted a prop. Current hrs is 600.
Europa is unlike a DA20 which, when powered by a Rotax, in the rain, will decend at full throttle under normal student type flying.
Flown with more understanding, ie enter cruise from a gentle decent, getting ahead of the drag bubble - the performance drop off is noticeable but not dire.
Based on my own experiences.
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
_________________
John Wighton
Europa XS trigear G-IPOD |
|
| Back to top |
|
|
Rick Moss
Joined: 21 Sep 2014
Posts: 96
|
| Posted: Sat Oct 23, 2021 12:05 am Post subject: Re: Flying In Rain |
|
|
I’ve also never previously had to repaint a prop. However, mine was repainted by Airmaster when it went back for overhaul; 12 months and 50hrs later, the paint is peeling on the backside of the blades. I don’t think that the paint job was that good tbh, but I’ve assumed it’s a consequence of flying in rain.
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
Duncan McFadyean
Joined: 18 Jan 2011
Posts: 220
|
| Posted: Sat Oct 23, 2021 3:35 am Post subject: Flying In Rain |
|
|
But 'dirty aircraft + rain = clean aircraft'!
Duncan mcf
do not archive
| Quote: | On 23 October 2021 at 08:27 John Wighton <john(at)wighton.net> wrote:
Very clean and polished aircraft + rain =no difference
Dirty aircraft + rain = flies a bit slower
Rick’s post is interesting, l have never repainted a prop. Current hrs is 600.
Europa is unlike a DA20 which, when powered by a Rotax, in the rain, will decend at full throttle under normal student type flying.
Flown with more understanding, ie enter cruise from a gentle decent, getting ahead of the drag bubble - the performance drop off is noticeable but not dire.
Based on my own experiences.
--------
John Wighton
Europa XS trigear G-IPOD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503597#503597
|
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
Duncan McFadyean
Joined: 18 Jan 2011
Posts: 220
|
| Posted: Sat Oct 23, 2021 3:38 am Post subject: Flying In Rain |
|
|
<<....the drag bubble ...>>
meaning beyond the bottom of hte J-curve? And does rain displace the position and form of the J-curve?
Duncan mcf.
| Quote: | On 23 October 2021 at 08:27 John Wighton <john(at)wighton.net> wrote:
Very clean and polished aircraft + rain =no difference
Dirty aircraft + rain = flies a bit slower
Rick’s post is interesting, l have never repainted a prop. Current hrs is 600.
Europa is unlike a DA20 which, when powered by a Rotax, in the rain, will decend at full throttle under normal student type flying.
Flown with more understanding, ie enter cruise from a gentle decent, getting ahead of the drag bubble - the performance drop off is noticeable but not dire.
Based on my own experiences.
--------
John Wighton
Europa XS trigear G-IPOD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503597#503597
|
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
