Icing

[337G]

Since I have not had any experience in the 337 with regards to icing can any one out there answer for me this question from a friend who has been flying a 337 for a few months now and is also pretty green when it comes to flying the 337 in icing conditions. Information about Your experience with the plane in these conditions is much appreciated!

" in regards to icing - I simply turn around if I can't make it melt away by changing altitudes. On Friday I ran into freezing rain that was not expected. I turned around , changed my flight plan, and diverted to P.A. An hour and a half later a Barron came into P.A. with about 1/2 inch of ice covering the first 16" of everything on the airplane. He encountered the ice exactly where I had. Seeing all that ice leads me to ask just how much ice is too much? What are the capabilities of a 337 compared to the Barron, and so on? I'M ALL EARS. Do you continue to fly into a known icing condition, expected or not"?

Cheers

[WebMaster]

NO!!!

I have boots on my plane. I have flown in ice. It is not fun. In fact, I was down right 'concerned' as I headed for the airport where I was going to land. It took a lot of throttle to stay flying, and I had to pitch up slightly. I was cycling the boots very often. I landed with about 4 inches of ice on the front of the radar dome (my aircraft has radar in a pod under the right wing). I had ice everywhere. The aircraft is not certified for known ice. You have to remember that. If you don't have any boots, you have no way to shed what is accumulating, and the situation just gets real bad in a hurry.

Now, I have flown where a bit of ice accumulated, and blew it off, no problem, but in heavy icing situations, the ONLY thing to do is get out of it. If you do not have boots, you don't have the ability to shed even a small amount, and you have to treat the situation as if it was an emergency, because it is.

Hope that helps.

[Jerry De Santis]

I have a P337G with boots. I I have been in ice too many times and Larry is right, avoid it. You were wise to turn around.

Now to answer your question. Procedure for my plane is not to use the boots until there is abut 3/4 inch of ice on the leading edge. The Skymaster will really carry a load but to tell you the truth, going into freezing rain is never on my agenda. Better wishing I was in the air when I'm on the ground then wishing I was on the ground when I'm in the air is my motto.
Jerry

ICE

[kevin]

Larry, Jerry and I all fly in heavy icing country. Larry flys quite a bit in lake-effect near Michigan, Jerry flys there and all over, and my flying is quite a bit in the Pacific Northwest.

So it is with some trepidation that I offer a slightly different opinion than Jerry's.

It has long been said that one should wait until you have a good load of ice (1/2 to 3/4 of an inch) before excercising the boots. Recently, one of the AOPA authors, I think it was Horne, did some research to see where that rule came from, and although oft repeated, Horne could not find the source of the rule, and could find no evidence that more frequent actuation of the boots removes less ice, or really causes the boots to form a pocket inside the ice on the leading edge, as is said. In my own experience, actuating the boots with a 1/4 inch of ice causes no problems. And icing is a very frequent occurence during a winter flight in the Pacific Northwest.

However you decide to go, I want to point out something that I have never read anywhere else:

Sometimes, the boots don't work.

One time, on a training flight, my instructor and I let 1" of ice develop on my P337, because I wanted to see how the airplane would act with that much of a load. On that particular day, it did quite well, losing only 20 knots of airspeed (but that will be different for every icing encounter, it depends on the type and rate of icing). Anyway, with an inch of ice on the airplane, I pressed the boot button, and nothing happened.

I immediately experienced a high level of stress, since we were at 16000' over a 10000' MEA airway through the Siskiyou mountains (between Medford, Oregon and Red Bluff, California, near Fort Jones). We turned around and landed in Medford, but a successful completion of that flight was made possible by the freezing level being at 9000', well above the field elevation of Medford. I would not want to have to carry that load of ice to the ground.

The boot system had sprung a leak since the last use, making it impossible for the pumps to pressurize the boots.

So, what I learned from that is to actuate the boots sooner to see if they work, to realize that they could fail any time, and to not fly myself into a situation where the boots HAVE to work.

There is a downside to more frequent actuation of the boots. The boot system on a Skymaster is a weak sister, and every time you actuate the boots you take a chance that you will kill your vacum pump. Now, there I go passing on what could be a wives tale, as I have never lost a pump that way. But my instructor, who has 500 hours in 337s in icing country, says it be true.

Those are my policies, you should make your own. If you fly in the central and eastern US, you have many, many more immediate alternates available than in the west. On the other hand, the freezing level goes all the way to the ground in winter in most of the US (except the balmy West Coast), meaning that any ice you accumulate, you are going to keep, unless you have boots (that work). In an unbooted airplane, with freezing levels on the ground, as Larry says, ice is an emergency, and you need to go where you KNOW there is no ice (either an ice free altitude, on top or below the freezing level, or turn around) *immediately*. In my opinon.

Blue skies (and no ice),

Kevin

[WebMaster]

Originally posted by kevin
It has long been said that one should wait until you have a good load of ice (1/2 to 3/4 of an inch) before excercising the boots. Recently, one of the AOPA authors, I think it was Horne, did some research to see where that rule came from, and although oft repeated, Horne could not find the source of the rule, and could find no evidence that more frequent actuation of the boots removes less ice, or really causes the boots to form a pocket inside the ice on the leading edge, as is said.

Kevin

It actually comes from Ernest K. Gann, talking about getting ice on the wing of a DC-3, ages ago, when DC-3's where the staple of the airline industry. He reported in one of his books that they fired up the new fangled boots, it was too soon, and the ice formed a bridge. He was in trouble. Interestingly, later day attempts to duplicate that have never worked.

Originally posted by kevin
Sometimes, the boots don't work.
Kevin [/b]

Which is why you should try to inflate them, on the ground, before taking off, and verifying that they work... Obviously, you can't check the boots on the horizontal stabilizer.

I do recall Bob Cook writing that he lost the front vacuum pump, while cycling his boots, going into IAG during the winter. Obviously, he needed them, and not only lost the ability to cycle the boots, but also lost a source of vacuum.

[Jerry De Santis]

I have to disagree with Kevin. I, myself did a test once in climb out where I picked up about 1/8 inch of ice. I wanted to see if those folks that said it doesn't make a difference when you inflate the boots. Well, I can tell you first hand, it formed a pocket and, that's right, the ice did not come of the leading edge. It took about 30 minutes of flying at 12,000 feet before it eroded and melted away. So, quite frankly I don't believe any of those people that claim you can use the boots with any thickness of ice...it's simple not true.

Jerry

[kevin]

Larry,

Yes, that is what I remember.

Last point from me - just because they worked on the ground does not mean they will work in the air. I am only suggesting that getting yourself into a position where the boots HAVE to work is unwise. And as you said, you can't check the tail, which is more critical than the wings.

Kevin

[Kevin McDonnell]

Regarding Ice Bridging: The NASA Glenn Research Center did an exhaustive icing study recently and concluded that bridging was a myth. (I'm not trying to argue any point here, but just show the new thinking on this subject contradicts what many of us were taught).

The latest AOP writing reflects the Glenn Research Center view.

See "Boots" on page 6:
http://www.aopa.org/asf/publications/sa11.pdf

See "If you got 'em, pop 'em":
http://www.aopa.org/pilot/features/inflight9910.html

And here's a cool NASA online course about icing:
http://aircrafticing.grc.nasa.gov/courses.html#

Under the section "Aircraft Designs for Icing-Deicing Systems" it makes some interesting statements, such as:

1) Waiting to inflate the boots can be dangerous
2) Ice bridging simply does not occur with modern boots
3) If you begin to accrete ice, activate the deicing system immediately and cycle continuously. Do not wait for a certain amount of ice to accrete, unless the AFM directs otherwise.

[sunnysky]

Just to add my bit to the icing debate. I fly a 337 G in Europe and have had several ice encounters. The boots do help, but ice forms elsewhere too. One problem area is the rear engine air intake which must attract a lot of ice as evidenced by the increase in cht's and oil temperatures. I have found this very limiting for continued flight.
No one has mentioned the prop de ice. Presumably the electric boots and rear exhaust does a good job.
Sunnysky.

[WebMaster]

Interestingly, and appropriate, their is an article on ANN, http://www.aero-news.net/ about the latest icing alert.


FAA advisory Safety Recommendation A-04-66. Also, more information at http://www.ntsb.gov/Recs/mostwanted/air_ice.htm

[Mitch Taylor]

There's an interesting note in Avweb on certifying the rear prop for icing on the Adam 500. FAA now requires pusher props to handle ice chunks shed from the wings. Article is at http://www.avweb.com/newswire/10_53b.../188869-1.html

[Rickskymaster]

Mitch
Where do you base your plane?
We are visiting over the Holidays in LA from Washington, DC.
If you have time to show us your plane, give me a call on the cell
Thanks
Rick
410-916-0039

[SteveG]

The ice training material developed by NASA at the Glenn Research Center in Cleveland is also available on CD-ROM & DVD. I believe Sporty's has them for about ten bucks, the pair. As for ice bridging, they are emphatic that it does not occur but do concede that earlier boot inflation may leave more residual ice than if a thicker accumulation is broken off. They argue that flight with a small amount of residual ice between cycles is less dangerous than risking a loss of control by allowing more ice to form. The discussion on the recovery techniques of a wing stall vs. a tailplane stall is alone worth the price and will certainly have you thinking about an instrument approach in low conditions to a slippery runway while carrying any ice.

[337G]

Hi every one hope you all had a good Christmas and New Years.

Thank you for all the information you have provided it is all very good stuff.

For my two cents worth, I am partial to letting some ice build up on the leading edge before cycling the boots. My last job was flying a PC-12 into Canada's Arctic and I ran into alot of icing. On one trip shortly after the info came out about not waiting for the ice to build up I decided to do an experiment on a moderate iceing day. I let the ice build up first and then cycled the boots to watch the ice nicely break off. Then, I selected the "continuose" mode and the ice did remain clear however, there were areas on the leading edge that would not clear and formed the dreaded pocket. Fortunatly they were only in a couple of areas and not very big in width.

I am sure aircraft wing design has alot to do with it and so each individual airplane will be different therefore we must exercise caution for the first few hours untill we get used our particular airplane and are familiar with what it is capable of handling. But the best remedy is to avoid it when able.

Craig