Icing: It's getting to be that time again!

[OtisAir]

Video's 1, 2, and 3. Ya'll be safe out there please.

 

[Ted]

Good to watch those videos again, as they've got some excellent information. This winter, I'm watching them with some observations and thinking how it applies to my aircraft, and one question came up.

They talk about typical aircraft configurations being ones in which the extension of the flaps results in the center of pressure in the wing moving aft, resulting in a nose down pitching moment. Additionally, they talk about tails that have a horizontal stabilizer and an elevator separate from that. In the case of my Aztec, the extension of flaps results in a nose up pitching moment (center of pressure moves forward) and the horizontal tail is a full stabilator, so the whole thing moves up and down. How would that make it different? I'd think the full stabilator would start to show symptoms earlier since a disruption of flow around it will always be affecting it. I think the configuration of my plane matches that of a number of others that we fly (especially the Piper pilots).

 

[twdeckard]

They talk about typical aircraft configurations being ones in which the extension of the flaps results in the center of pressure in the wing moving aft, resulting in a nose down pitching moment.

When talking about the Center of Pressure strictly, think about the wing only (I don't think you depict a CoP for the whole airframe).

As flaps are lowered, the center of pressure moves rearward creating a nose down, pitching moment. In airplanes that pitch up it is becuase the change in downwash from the flap enhanced wing increases the angle of attack for the tail so dramatically that it overcomes the moment from the shift of pressure on the wing.

Now how this would affect your vulnerability to tailplane icing ... I suspect the collection efficiency of the tailplane compared to the wing would be of greater concern. A supersticous fellow might say if the airplane pitches up with flaps you are more vulnerable to flaps deployment if contaminated.

As for if an all flying stabilator would cue you sooner I cannot say but I would guess that it would?

I'd be curious if any of the Aztec freight dogs chimed in, especially if there was guidance to avoid "pumping" the yoke when accruing ice becuase you wind up pasting more of the bottom surface of the stabilator?

Perhaps its really not a concern in the Aztec beyond the normal phobias for ice. By the time you are worried about your longitudinal stability you've long since run out of lattitude?

 

[Ted]

More or less my thoughts. The Aztec's tail will be a more efficient ice collector than the wing (the tail reminds me of the wing of a Mooney), but given the plane's brick-like aerodynamics, what I get from people is that it's a pretty good plane for ice use due in part to its inefficiencies.

Would be good to hear from Aztec freight pilots on this.

 

[Aztec Driver]

I have been looking for those answers ever since my encounter. It does seem to fly OK, but I chose not to deploy flaps for that reason.

 

[Greg Bockelman]

So what is the story with those pictures? Looks more like freezing rain on the ground rather than an inflight encounter.

 

[Teller1900]

After this week (so far) I can say with certainty that icing season is here on the East coast, and it's angry!

 

[Aztec Driver]

So what is the story with those pictures? Looks more like freezing rain on the ground rather than an inflight encounter.

That is freezing rain in flight. After diverting and landing, the next day it was encased in a solid block of ice.

 

[Erice]

I remember reading another forum right after the Colgan 3407 accident in Buffalo last February. The recurrent training that CJC pilots were last given focused a lot on tail plane icing. Sounds like they may have watched this exact video. Some on that forum were saying it was no wonder that the CA of 3407 pulled back on the yoke--as much as they reinforced that action in this presentation. Unfortunately, it was just a wing stall.

The point is, the differences in the feel between wing and tail icing are very subtle, and require exactly the opposite action to recover.
________
silver surfer reviews

 

[Ted]

After this week (so far) I can say with certainty that icing season is here on the East coast, and it's angry!

Yeah, that's for sure. Fortunately when I was flying yesterday the icing wasn't bad. Picked up about an inch and a half total. Annoying part was that it wasn't hard enough to want to come off nicely. Definitely learned a lot, good flight. Glad to have the equipment on board. The tail did get heavy once the ice started building on it, but worked fine.

 

[flyingcheesehead]

Icing: It's ALWAYS that time. I've flown actual in the winter months without ice, but the big eye-opener was when I picked up ice - In August. Bit of a surprise, there...

 

[Commander Dave]

Had my first icing encounter this year as I was crossing Lake Erie at 9000 feet. It was not a very comfortable experience. I had no idea how much ice the Commander can carry, I just knew I didn't want any. All in all, I must have hit some mixed as I picked up about 3/8" of ice in a matter of seconds.

My biggest concern was actually the windscreen. I knew I was about to fly into the first cloud (was asking ATC for higher for 3 minutes prior.) I was at 9000, -4 degrees so whether it would have been frozen already, or would stick to the aircraft was unsure to me. However once I hit the mix, the windshield was completely covered and I could no longer see to avoid clouds. Luckily I didn't encounter too much more, and ATC finally gave me the clearance for higher. Another minute or so, and I would have declared an emergency and taken higher.

First experience, wasn't pleasant.

Lessons learned:

Always have an out
Don't think that -4 will be too cold for ice (rules say +2 to -5 are potential)
If penetration is coming, get the climb/descent, or get a Vector - don't enter
And lastly - If it's still flying - fly the airplane (my aircraft control definately suffered while I was looking around at the ice on the wings and wondering how bad it was. Finally I decided to accept it and fly the plane)

 

[Commander Dave]

I'm not sure what rules you are referencing, however, you might want to read a recent e-Tip I sent to my members about the role temperature plays in icing.

Scott,

Thank you for the e-Tip. That information was very useful to me. Believe it or not the reference I made came from a recent FAAST team visit regarding icing. The speakers made the +2 to -5 degrees C comment.

I appreciate your setting me straight.

 

[gprellwitz]

Thanks Scott, I was about to comment on that icing temperature range.

And Dave, if you picked up 3/8" in a matter of seconds, why were you going to wait another minute before declaring an emergency? Had you continued to collect ice at that rate, after a minute higher very well may not have been an option available to you.

 

[Commander Dave]

Grant,

The reason I was waiting was nothing else was happening. As I said this was my first experience (and quite frankly would like it to be my last) when I went into the cloud it was like a SPLAT! almost as if (while driving) I hit a puddle on the road and my windshield was covered with water. After that, nothing else was happening. I wasn't picking up anything else, I just couldn't see to avoid what had just happened.

Since I wasn't picking up more, I was a bit more patient with ATC. I should also note due to the manner and speed at which it collected I didn't think a 180 turn was wise. I was in the clear (for the moment) and wanted to stay there. I knew about 500-700 feet higher was clear, so thats what I wanted.

Alot learned for me on this day. However I'm sure I have plenty left to learn.

Keep the critiques coming!! The life you save may be mine!

Seriously, this event was quite alarming at the time. I don't have the Super Pilot ego, I'm here to learn from anyone I can.

 

[wsuffa]

Grant,

The reason I was waiting was nothing else was happening. As I said this was my first experience (and quite frankly would like it to be my last) when I went into the cloud it was like a SPLAT! almost as if (while driving) I hit a puddle on the road and my windshield was covered with water. After that, nothing else was happening. I wasn't picking up anything else, I just couldn't see to avoid what had just happened.

Since I wasn't picking up more, I was a bit more patient with ATC. I should also note due to the manner and speed at which it collected I didn't think a 180 turn was wise. I was in the clear (for the moment) and wanted to stay there. I knew about 500-700 feet higher was clear, so thats what I wanted.

Alot learned for me on this day. However I'm sure I have plenty left to learn.

Keep the critiques coming!! The life you save may be mine!

Seriously, this event was quite alarming at the time. I don't have the Super Pilot ego, I'm here to learn from anyone I can.

Dave,

I don't know whether you have vortex generators or not on your bird, but that makes a difference. I've picked up light rime a couple of times on my Commander before I could get out of it.

Once was at 16,000 feet east of Dallas in late summer - I was in the bottom of a thin cirrus layer - and ATC gave me an immediate descent to 14,000 when I reported it. I did not get anything on the windscreen.

I think the VGs would negatively affect performance in icing, but I've never had any interest in getting into that situation.

Bill

 

[gprellwitz]

Grant,

The reason I was waiting was nothing else was happening. As I said this was my first experience (and quite frankly would like it to be my last) when I went into the cloud it was like a SPLAT! almost as if (while driving) I hit a puddle on the road and my windshield was covered with water. After that, nothing else was happening. I wasn't picking up anything else, I just couldn't see to avoid what had just happened.

Since I wasn't picking up more, I was a bit more patient with ATC. I should also note due to the manner and speed at which it collected I didn't think a 180 turn was wise. I was in the clear (for the moment) and wanted to stay there. I knew about 500-700 feet higher was clear, so thats what I wanted.

Alot learned for me on this day. However I'm sure I have plenty left to learn.

Keep the critiques coming!! The life you save may be mine!

Seriously, this event was quite alarming at the time. I don't have the Super Pilot ego, I'm here to learn from anyone I can.

Oh, I try to be always learning too!

I'm not sure how you could tell that the accretion was virtually instantaneous if you could no longer see out the window. I take it that only the windscreen was affected? It's also good to know that the clouds were so scattered, and a thin layer to boot. (pun intended ) That does give you more outs. Since you lacked forward visibility at the time, I think I would have at least gotten on the radio and immediately requested an immediate climb because you were picking up ice, rather than waiting the minute. And I agree about not doing the 180, given the additional info! (Hey, that was cool! Let's go back for some more and see how much she'll really carry! )

 

[Commander Dave]

No VG's for me Bill.

And agreed, don't need to do it again.

 

[Commander Dave]

I'm not sure how you could tell that the accretion was virtually instantaneous if you could no longer see out the window. I take it that only the windscreen was affected?

Yes forward visibility was lost - I had the side windows so I could see the wings weren't picking up more, and I could still see the temp probe fairly well. (watched these very carefully - too carefully - had to start watching instruments again) The side windows, and about 6-8 inches of the windscreen (part that curves on a Commander) were clear, so basically I was looking out the window to the side. If I could see clouds 500 feet away - I wasn't in them... Thats what I kept watching for.

Since you lacked forward visibility at the time, I think I would have at least gotten on the radio and immediately requested an immediate climb because you were picking up ice, rather than waiting the minute.

Just to add a bit more clarity here. I was flying over an overcast layer at 9000, when I came to Lake Erie. Now the cloud deck was higher (just over the lake.) I had a similar experience during the flight over, and attribute the higher cloud deck to more moisture content available to create more energy for lifting. I saw only the one cloud at my altitude, but clearly could see over it, just not what was beyond it.

I was trying for about 3 minutes to get higher and was unsuccessful. After penetration I wasn't waiting another minute to call ATC, I was talking with them quite regularly (heart beat, heart beat.) There was traffic above me so I was advised I couldn't get the clearance. Since I wasn't picking up any more ice I didn't choose to declare an emergency, and waited one more minute to allow the controller to work this out for me, and made sure he was aware I was picking up ice (I didn't tell him I had it all and it stopped - I said "picking up ice") At this point if he hadn't gotten my request handled (the one minute I was waiting) I was going to take the climb I needed and declare an emergency as I began the climb. He knew my situation and I gave him ample time to react.

All in all, he was very calm, and that helped.

To do this over again...

When I saw the cloud in front of me at -4 C, (Especially after reading Scott's post) when I didn't get the requested climb, I would do a 180 prior to cloud entry and tell the controller I can do 360's this location until he can get me higher or lower.

 

[gprellwitz]

Thanks Dave. A learning experience, n'est pas? And I have heard that the Great Lakes, and Lake Erie in particular, can be ice makers.