F

foka4

Well Known Member
In a cursory review of past VAF posts, I see a lot of discussion on how to account for winter operations in our design and construction of pitot/static systems, engine preheaters, etc., but relatively little discussion on what to expect in the most important of winter ops discussions: an actual encounter with in-flight icing.

My first GA encounter with ice was on my first IFR lesson. It was also my first flight in IMC, my first flight as PIC in a nosedragger, and my first flight in a complex aircraft. That was quite a lesson. Later, as a licensed IFR pilot, my next icing encounter was in VMC! If there's one thing I've learned about icing, it's that you can't learn enough about icing.

Disclaimer: Flight in icing conditions is a bad idea. Flight into known icing conditions (unless appropriately equipped) is illegal. If you're contemplating an RV flight that may take you into icing conditions, take the airlines. The risks of flying personal aircraft (RVs et al) into icing conditions are well-documented elsewhere, and if you don't understand those risks, don't fly in air colder than 40 deg F. This posting is not intended to encourage RV operations in icing conditions, nor is it intended to be a place for pilots to pontificate about the dangers of icing.

With all of that out of the way, I'd like to explore the topic of icing and RVs in the same way we would discuss loss of oil pressure, smoke in the cockpit, and dead stick landings: not things you would intentionally subject yourself to, but things that may be more survivable with the right knowledge, preparation, and vigilance.

I'd like to get the insight of the VAF community on how our RVs handle ice, and what we can do to put the odds in our favor after an unintentional encounter with unknown icing conditions. How does the RV airfoil react to ice accumulation? How quickly does visibility diminish relative to performance? What are the first signs of ice accumulation on the airframe? On the instrument panel?

Obviously, mileage varies greatly from one situation to the next, but if we can share some insight here, we may be able to help a fellow RV'er turn a tense situation into an uneventful outcome.

Thanks,

M
 
foka4 said:
How does the RV airfoil react to ice accumulation? How quickly does visibility diminish relative to performance? What are the first signs of ice accumulation on the airframe? On the instrument panel?
M
Click to expand...

First indication will likely be a complete frosting over of the windscreen. The wing didn't seem affected by a slight amount of ice. The thing that concerned me the most is that the horizontal stabilizer, relatively speaking, is very thin could build accumulation to the point a tail stall would be a real possibility (I didn't have the time or the chance to look out the back and try to assess how much ice was there), so if you get some ice, don't use flaps for the landing. Not too much on the panel (at least mine) that can warn you in advance. If you live up north, including pitot heat in the build isn't a bad idea.

Don't get me wrong - I love this airplane, but it wouldn't be my first choice in icing conditions. Be sure to leave yourself a plan B.

YMMV.

Dan
 
RV9A in ice

I used my 9A to commute to my job in Seattle across the Cascade Mountains from my home in Eastern Washington for a couple of years. I normally filed IFR and the major concern I had was icing. I never picked up more than a quarter inch or so of rime, but that was enough to knock 300fpm off the climb and fifteen knots off the cruise until the ice sublimated off. The major effect I had was with the composite MT prop. The ice sheds unevenly and the prop vibrates in an unsettling manner. I don't fly IFR anymore unless I can stay out of the clouds when icing is possible. I commuted for several years previous to this in a Cessna 205 that would pretty much slog its way through anything but it was twice as heavy and had 100 more horsepower. RV's are great little airplanes but my advice is don't fly them in ice.
Bob House RV9A 462BD
 
I have got caught in it twice and rather lightly. The surprising part was that both times were in summer time and I had expected it the least. The first time, it scared the heck out of me and the first sign was the ice on the canopy which seemed like a trail of water then I realized it was ice. Requesting higher got me out of the cloud and short time later, it was all gone.

The second time it was in the mountains over Idaho, I couldn?t go higher due to temp and couldn?t go lower due to MEA. Both times ice formed on the wing root area and wind shield only.

I will do all I can to stay away from ice as it scares the heck out of me.
 
I maintain my normal flying activities throughout the winter, but more closely pick my spots in traveling from Illinois to New York. After all, it's not legal to fly a plane into known icing conditions without the appropriate equipment, i.e. heated windshield, heated or anti-iced prop, leading edge deicing boots, etc. The definition of known icing conditions is somewhat subjective as in "unless someone reports it in the location your flying, it's not known." At least that's how I've interpreted it over the past 40 years.

The best tool I've found for RV wintertime flying is an accurate OAT gauge. With a little more thorough detective work during a weather briefing, I've generally found an altitude or route that would work, IFR of course, that would keep the moisture in a liquid form. I've also found ATC to be very accomodating in responding to requests to exit conditions where the ice is actually accumulating. I've seen 1/4" to 1/2" buildup on the airfoil leading edges and found the plane handled it well. But, I made it a point to fly a 10 to 15 kt. faster approach speed.

I don't know why you wouldn't use flaps in the landing mode, It's just that once they're down, don't retract them inflight, something the American Eagle crew found out the hard way a decade ago south of Chicago

Of course, you need to have an out, but it's doable. The dead of winter usually isn't too bad, because any precip is already frozen and won't likely stick with temps below -5C or 25F.

One curious thing I noticed on the ramp on clear, frosty mornings away from home was that frost was only present on insulated or painted surfaces. My unpainted wings and stab accumulated no frost. The fibreglas parts all had frost along with the prop. The adjacent, fully painted, Cherokee 6 was loaded with frost.

I did make it a point to install a windshield defrost setup during my build which helps, but have yet to add pitot heat. My comfort level is different than others, so find yours and equip the plane to match.

Mike
 
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RV on ice.....Getting to be that time of year.:D

frozenRV-7.jpg
 
Icing Encounter in an RV- If You Have to Ask, Don't

Rather than encourage anyone by suggesting how or how much icing an RV can handle, I'd offer the following to anyone who thinks ice is a possibility on an RV flight:
1. Pitot Heat- Don't leave home without it. Test it during you preflight. Know when to turn it on (before you encounter ice).
2. OAT - Don't leave home without it. Pay attention to it whenever you're near moisture. Have a plan before you need to execute one.
3. Carb Heat - especially on an RV, it's NOT a de-ice device. Repeat this to yourself several times. If you're not sure-LEAVE IT ON.
4. Know that when you pull the carb heat knob, you're going to lose some percentage of power- this will make carrying airframe ice more problematic.

Finally, if you're not sure of the answers to the following, you need to do some more studying before flying anywhere where freezing conditions may exist:
1. What happens to your Airspeed indicator if the pitot inlet ices over?
2. What happens to AS if the pitot drain ices over as well?
Fly safe.
Terry, CFI
RV9A N323TP
 
Ice forecast tool

I'm now old enough to admit that I hate flying in ice. I avoid it like the plague in anything without a turbine engine (there's no magic to the turbine, but most have the performance and equipment I desire to get out of or through the ice).

Historically ice has been very difficult to forecast (except during freezing rain events, of course). Now there is a great tool on the ADDS weather system that I've found very useful and generally accurate....

http://www.aviationweather.gov/adds/icing/icing_nav.php

It does a great job of pulling together probability, severity, and PIREPs into one graphic. You can play around with the times and altitudes to help yourself avoid unpleasant encounters. Like any forecast, it isn't perfect, but this is the best I've found for icing info.
 
Icing Video

Hey, that is a young Rich Ranaudo flying the NASA icing test plane. He also built an RV-4 years ago.
 
Must see video

That video is great.

I didn't even know about Tail wing stall due to icing.

This video is excellent. Doug you should put this on the front page.

Its a must see for anyone that flies IFR.
 
ice

Below freezing level + visible moisture = Ice.
i.e. in cloud below the freezing mark and you'll get ice.
VRF conditions in light snow and you'll get ice.
Icing assocated with a warm front such as freezing rain or even drizzle would not leave you much time to get out of it. Catch rates are extremely high.
Your fuel drains can freeze up, air filters, pitot tube, anything that sticks out can get ice build ups. Once even had ice build up on the small prop governor bumps on the engine cowlings of a king air in freezing drizzle. Bolts that hold the windshield wiper blades had baseball sized chunks of ice on them after two approaches to localizer minimums (2 missed) and one NDB approach. Procedure turns were in the clear! Had to inflate the boots around every 2 or 3minutes to keep the ice off the leading edges.
Do all you can to completely avoid icing conditions by making the right decisions on the ground and in the air. Written regs defining "known ice" will not help you get out of it. In cloud below 32F or 0C you'll get ice. That's known ice to me.

While you're on the subject, another point worth mentioning is not to ride the brakes (not that you should any time) while taxiing on snow. Hot brakes can melt snow that gets thrown up into the brakes while taxiing and can freeze up your brakes.
Fly Safe.
 
One very general rule of thumb is, the thicker the airfoil, the better the performance of the wing in ice. Thin, laminer flow wings don't carry ice well. Thick wings like a Piper Apache are better.

When a young copilot on a Metroliner at a regional airline, I had a captain decide to fly through a "small" thunderstorm to save some time. Argh! We were at about 17,500' and climbing when we flew through a supercooled rainshaft. Within several seconds we suddenly had over an inch of ice on the wings and belly of the plane, several hundred pounds, I would guess. Climb rate dropped to zero. We asked for and got FL 180 as a final. I tried to never fly with that captain again.

I remember one approach I made into Roanoke as a captain, we had been picking up ice during the approach and blowing it off with the boots, a fair amount, too. Because you are slower on an approach, like in a a climb, the angle of attack is higher and the belly (as well as the bottom leading edge of the wing behind the boot) of the plane is prone to accumulate ice. When I put the props into beta after landing all that ice fell off and went sliding down the runway in front of me. Very dramatic.
 
Ice Alley

Great Thread.:) Very interesting. Ice is not something to take lightly. Has ended many aviators thrill of flight unexpectedly. Really helpful NASA video about tail stall-thank you for sharing! Would have never realized flaps had that effect.

I recently had an encounter with in-flight icing while IMC in my trusty RV8 and it was NOT fun. No bad aerodynamic things happened, it just surprised me how stinking fast it all happened and how helpless it felt. I'm no wimp but when the window starts to get buildup and the leading edge gets a bit of frosty white stuff and the AS drops off in a matter of seconds, I'm otta there!:eek:

Fortunately, before it happened, I had a plan :D and was standing by if ice was encountered enroute. A few miles earlier I had gone off freq with approach and picked up PIREPs for the area, asked FSS what the wx was at my alternate(s) along the way and asked where VFR was relative to ME and my route. Gathering information along the way from FSS or XM or ATC is useful for, as they say on those adds; "when the mood strikes."

So, cruising along IMC with ATC on my side (very helpful folks most of the time) they immediately cleared me to known VFR conditions (90 deg of original course). After an eternity... two long minutes... I broke out VFR... the ice sublimated and AS returned. BTW, the one button press for a simulated AS off the GPS was quite useful-good to know the fancy equipment.

Will continue flying IFR and will be vigilent to avoid icing conditions in the future. Can only imagine what those early flyers went through to deliver "snail mail."

Again, thanks for sharing & fly smart.
 
Rotorheadrob said:
Again, thanks for sharing & fly smart.
Click to expand...

Welcome to VAF, Rob! Great first post; ice stories like yours scare the pucker into me, but nice to see your professional reaction. Super group of folks here--builders and flyers--and you'll make a nice addition with your experience. See ya around!

--
Stephen
 
Inflight Icing

I posted a couple years ago on this, but can't find the post right now.

I was fortunate several years ago flying over the Cascades VMC on top of a layer at 15K MSL (on an IFR flightplan) at night. Forecast icing 14k and below. Slight waves in the stratus layer below me had me just topping the waves at 15k for a minute or so every 10 minutes. Not picking anything up and just enjoying the gorgeous view on the full moon night. XM WX radar shot showed me about 10 - 20 miles from leaving all the wx behind.

Popped into what I was assuming was the last "wave" and picked up 3 - 4 inches of ice in the period of about 30 seconds. Here's where it got fun.

Pitot iced up, leaving me with GPS groundspeed for a reference.

Engine continued to run fine, but I *think* at reduced power due to probable intake icing.

Unable to maintain altitude due to the weight of the ice and/or the reduced power.

Trim was frozen solid.

THE ELEVATOR WAS ALSO FROZEN SOLID!!! I was completed unable to move the stick fore and aft.

The plane was in about a .8 or .9G pushover. Going through about 20 degrees nose low, I considered rolling inverted to see if it would help get the nose up, but squashed that idea since I did not have inverted fuel or oil on the plane. As a last resort, I hit the stick with the heel of my hand as hard as I could, breaking the elevator loose without damaging anything (verified with a detailed inspection the next day...) Ended up working with center to get as low as I could and flew a no-trim no-flap VOR approach into Klamath Falls at night.

Lessons learned: STAY OUT OF ICE!! Even tho the large excess performance we enjoy in our RVs can compensate for some poor decisions, you can still end up dead in a BIG hurry by not respecting mother nature. I'm only alive due to a little luck in regaining control of the aircraft (and not breaking a linkage or something) as well as a lot of preflight planning on diverts, terrain, and single pilot night IFR setup.

There is a lot of knowledge out there about pitot icing, airframe icing, engine intake icing, tail stalls, etc. It had never even occurred to me that I might get enough ice fast enough to flow back and freeze a control surface...

Fly safe

John
RV-10 SSLLOOWW BUILD 40208 Wings
 
Icing conditions

As heard at Van's, RV's are not tested for icing conditions, performance with ice on board or how ice accumulates on the airframe and control surfaces.

I have heard for years that this is not the plane to fly in icing condition.

I fly over the cascades in NW Oregon most every month of the year, although not in icing conditions.

Check the weather.
 
I had an inadvertent icing encounter yesterday, and took advantage of the opportunity to check the effect on stall speed and stall characteristics.

I took off from our small airport and climbed to assess the height of the cloud bases. As I approached the base of the cloud I hit some light freezing drizzle. I immediately turned and got out of it, but I had collected an even coating of frozen droplets on the windscreen and wing leading edges. Visually, it looked like 80 grit sandpaper, but it was a very thin layer which conformed to the shape of the wing leading edge.

I checked the stall speed and stall characteristics, with flaps up and fully down. The stall characteristics were identical to what I have seen on every other stall I have done. I descended to 1000 ft AGL, with max airspeed to get the total air temperature up, and melted the ice. I then checked stall speed again, without ice. I found that this very small amount of ice increased the stall speed by 2 kt, or about 4%.

This stall speed increase represents about an 8% loss in lift available from the wing. This was a smaller effect than I had expected to see, based on my experience artificial ice shapes on larger aircraft, with more critical airfoils. A larger amount of ice would certainly have a larger effect. Be careful out there.
 
Last night while descending out of 500ft on an ILS we experienced extreme icing and subsequent failure of our left engine intake anti-ice. This resulted in a large amount of ingestion into the left engine intake which shutdown the left engine. It took all the effort mustered from our two man crew to get things under control. It was a wild ride and great lesson learned. Fortunately this occurred in a simulator, but still left me sweating.

Keep in mind that when a PIREP from a Transport Category aircraft says "light to moderate" they have equipment to shed that. "Light to moderate" barely raises an eyebrow.

"Light to moderate" in an RV however would be equivalent to "extreme" for the 121 operator. "Extreme" to them is "icing that exists beyond protection". Since an RV has no protection, even traces can have "extreme" results.

Rime, clear and mixed are the normal classifications of icing, but if you ever find yourself in sleet, you are in real trouble.
 
Not all airplanes require air frame de-ice...

Certainly RV's are not suited for any ice. I have very limited experience with it because I avoid it but have inadvertently encountered it once of twice, never more than just a trace. Flying below a cloud deck with good visibility but the OAT below freezing can result in a trace of ice most any day. I experienced it on the trip to Oregon in late November.

Just another reference point with regard to ice and airplanes - the USAF KC-135 tanker has no de-ice provision for the wing or tail. Engines and windscreen yes but no airframe de-ice. I don't know how or why Boeing and the USAF determined it was not needed. We did fly in icing conditions with no concern or apparent performance degradation. In fact some days it seemed a little ice made the machine climb better. The civilian version, the 707, did have wing and tail de-ice but that may have been more due to regulations governing commercial aircraft than the actual need for it.

If an airplane has enough power, speed can be increased to where skin friction causes a temp rise and the ice will melt off. If RV's could go that fast, it would work there also. :)
 
David-aviator said:
If an airplane has enough power, speed can be increased to where skin friction causes a temp rise and the ice will melt off. If RV's could go that fast, it would work there also. :)
Click to expand...
Actually, this temp rise is available even to RVs. The effect is proportional to the square of the TAS, so the amount of temperature rise we get is certainly much less than seen in faster aircraft, but it can be useful none the less.

At 160 kt TAS the total temperature (i.e. the temperature of the air at the stagnation point on the leading edge of wings, etc) is about 7 deg F warmer than the ambient temperature. This ram temperature rise is the reason why I was able to melt the ice I collected on Friday, as the OAT was just below freezing.
 
I've picked up ice once in the first 50 hours of my -6A from passing through light snow. Nothing on windscreen at all, however, the wing had a trace of rime. After landing and getting out, I found the tail surfaces also had a trace of rime present as I had expected based on their smaller leading edge radii.
 
Bevan said:
Kevin,

Can you explain the calculation as to how you get 7 deg rise above ambient?

Bevan
Click to expand...

Bevan,

The most commonly seen formula for ram temperature rise is:

Total temperature = OAT * ( 1 + 0.2 * M^2)

where Total temperature = ram temperature = OAT + ram temperature rise
M = Mach number

So, ram temperature rise = OAT * 0.2 * M^2

OAT and total temperature must be in absolute temperatures (i.e. in degree K or degree R).

The above equation is not so useful for those who fly aircraft without mach meters.

There is a mathematically equivalent, but much more useful formula that is based on TAS instead of mach number:

ram temperature rise in deg C = (TAS^2) / 7592
ram temperature rise in deg F = (TAS^2) / 4218

TAS is in kt for both the above formulae.

In the earlier post, I should have said 6 deg F, rather than 7 deg F. Not sure why I said 7.
 
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