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Northwest727
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Joined: Sat Jul 30, 2005 10:38 am

Waiting For Ice To Form Before Using Boots?

Thu Mar 22, 2012 4:06 pm

This seems to be a topic that has no clear answer.

I've heard that when flying in icing conditions, a pilot should wait until 1/4-1/2 inch (6-13 mm) of ice accumulates before cycling the boots. The Piper Seneca that I am going to fly 135 shortly AFM states the same, even putting a warning about cycling too early for the risk of making the ice "elastic" and sticking to the boots. But yet, I hear from other sources (some that even reference the Comair EMB120 crash in the '90s) that this is not true with more modern aircraft (built after the 1960s) and is yet another aviation old wive's tale that just won't go away, and that a pilot should cycle the boots as soon as any ice forms. In fact, Embraer apparently rewrote its recommendations before the crash (and never made it into Comair's manuals) that a pilot should not wait for ice to accumulate, as it is dangerous to allow any ice buildup. What is the correct procedure?
 
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Francoflier
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RE: Waiting For Ice To Form Before Using Boots?

Thu Mar 22, 2012 4:21 pm

I have never heard anything to the effect of cycling the boots as soon as ice starts forming. I just can't see how it would work as boots are designed to break the ice, not prevent it.

That's why they're de-icing devices, not anti-icing devices.

Of course, there is a fine line. You shouldn't wait until the ice is too thick to start using them, and then the type of icing will also influence their use and effectiveness.
 
DashTrash
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RE: Waiting For Ice To Form Before Using Boots?

Thu Mar 22, 2012 7:13 pm

Quoting francoflier (Reply 1):
I have never heard anything to the effect of cycling the boots as soon as ice starts forming. I just can't see how it would work as boots are designed to break the ice, not prevent it.

Because after years of operating boots this way the way ice accumulates on a flying surface, adheres to said surface, boot composition, coatings, even the ice itself has changed. With the new ice the atmosphere churns out and everything else I mentioned, the procedures have changed.

Or it could be that lawyers wrote our procedures again, and ice really does bridge those boots.....
 
FlyHossD
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 1:36 am

Quoting Northwest727 (Thread starter):
I've heard that when flying in icing conditions, a pilot should wait until 1/4-1/2 inch (6-13 mm) of ice accumulates before cycling the boots.

For many aircraft, that's correct - let a crust form before using the boots. By the way, I'd recommend not using flaps for landing in a Seneca if you have had any real ice accumulation (yes, I learned that one the hard way).

Quoting francoflier (Reply 1):

I have never heard anything to the effect of cycling the boots as soon as ice starts forming. I just can't see how it would work as boots are designed to break the ice, not prevent it.

That's why they're de-icing devices, not anti-icing devices.

There are a few aircraft with anti-icing boots; the ATR series for one.

[Edited 2012-03-22 18:38:53]
 
LimaFoxTango
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 2:18 am

Quoting flyhossd (Reply 3):
There are a few aircraft with anti-icing boots; the ATR series for one.

Boots are "De-icing" equipment which means it removes ice after it has accumulated. "Anti-icing" equipment prevents ice from accumulating in the first place ie. pitot, leading edge wing or prop heaters.

According to the Dash 8 Flight Manual:

"On initial detection of ice: AIRFRAME AUTO selector - FAST or SLOW, depending on the rate of ice accumulation. Check that the WING and TAIL advisory lights illuminate and go out sequentially in pairs."

To answer your question, no you do not wait for any buildup of ice before you turn on de-icing boots.
 
FlyHossD
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 4:54 am

Quoting LimaFoxTango (Reply 4):
To answer your question, no you do not wait for any buildup of ice before you turn on de-icing boots.

So in the case of the Dash 8, the boots are anti-icing equipment (like the ATRs)? Just to be clear, the boots on the ATRs are ANTI-ICE boots and are turned on at entry into icing conditions.

Nearly all of the booted aircraft that I've flown were equipped with de-ice boots, where you did wait for a crust to form before inflating the boots.
 
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Francoflier
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 9:13 am

Quoting flyhossd (Reply 3):
There are a few aircraft with anti-icing boots; the ATR series for one.

As far as I know, the ATR's boots are de-ice devices (as are all boots). Then again, this is a semantics issue.

Quoting LimaFoxTango (Reply 4):
To answer your question, no you do not wait for any buildup of ice before you turn on de-icing boots.

Depends.
Bigger aicrafts (turboprops) do have more advanced systems which include an automated boot cycling timer and an ice accretion detector.
On those, you only turn the anti-ice devices when entering icing conditions (OAT less than 5 deg C and visible moisture), those are basically all the electrically heated stuff. When the systems detects ice accumulation, you then turn on the boots, which are automatically cycled. There is generally a choice of 2 cycle times, depending on the severity of the icing condition.
In this case, you just set them and forget them, but the operating principle of the boot is still the same: the timer waits a little while the ice accumulates and then inflates the boots to break and remove what has formed during that time.

In a smaller aircraft, like a light twin, boots are generally operated manually and the pilot is more involved in determining how much ice has formed to inflate them. Then again he can see his leading edges...

Long story short: The system should be operated exactly how the AFM says they should be operated...
 
FlyHossD
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 10:38 am

Quoting francoflier (Reply 6):
As far as I know, the ATR's boots are de-ice devices (as are all boots). Then again, this is a semantics issue.

No. IIRC, and I flew ATRs for almost 6 years, the boots on ATRs are considered to be anti-ice devices. Considering the ATRs incidents and accidents, at least those that I'm aware of, those aircraft wasn't operated that way (i.e. per the AFM).

Quoting francoflier (Reply 6):
Long story short: The system should be operated exactly how the AFM says they should be operated...

Yes.
 
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Francoflier
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 12:48 pm

Well, you've successfully managed to have me read the ATR FCOM now...

It does label the wing and engine systems as de-ice, and the controls are located on the 'de-icing panel' on the overhead console. However, it does mention that the system should be activated as soon as ice accretion starts and to not wait for ice build up. So basically, as soon as the ice detector lights up, it's flicked on and the boots start doing their thing.
But the need for actual ice accumulation conditions does exist, as opposed to those systems you turn on whether there is ice building up on the airframe or not.

Not sure if that still qualifies as de-ice or anti-ice in the great persnickety dictionary of formal aviation semantics, but I have a feeling it's completely moot anyway...
 
 
RaginMav
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RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 3:06 pm

Ah, the age old boot operating debate. It's like Coke v. Pepsi, A v. B, 2 engine v. 4, snow globes v. flightaware.com, and other mythical a.net arguments.

This:

Quoting francoflier (Reply 6):
Long story short: The system should be operated exactly how the AFM says they should be operated...



is the correct answer.

I'm going to ramble on for a while here... and probably not say anything you don't already know. Humor me, please! AC 91-74A is the icing bible, as far as I'm concerned. Read it, you wont be dissapointed! From it, we get this little nugget:

Quote:
"The FAA recommends that the deicing system be activated at the first indication of icing"

However, at the end of the day, your AFM/POH has the final say. The bad news is, it likely reflects the state of the art from probably the mid-70's. Make sure your AFM/POH is up to date, often times icing data is added or revised long after the aircraft is built and delivered.

In my limited experience (King Air), I find it best to begin boot activation at 1/4" accretion. I don't see much more improvement in shed when I wait longer; therefore, we might as well start activating the boots at 1/4".

Other things to know:

-As I'm sure you know already, keep your boots well conditioned. I cannot over stress how important this is. If you're regularly flying in significant ice, you should dope the boots at least once every two weeks.

-What does your Seneca have for windshield ice protection? If it's alcohol, make sure you activate it well before landing to clear ice. The alcohol needs time to clear the ice, and then run off the windshield.

-If you have an engine or generator failure in icing conditions, the generator on the operating engine will likely be maxed out trying to run everything. Have a plan to deal with this.

End of lecture. Fly safely, my friend!
 
SlamClick
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Joined: Sun Nov 23, 2003 7:09 am

RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 5:21 pm

Best advice I can give is follow your operator's manual and DO NOT follow any advice given by usernames on this site. Would you take medical advice from us?
 
EGGD
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Joined: Sat Feb 24, 2001 12:01 am

RE: Waiting For Ice To Form Before Using Boots?

Fri Mar 23, 2012 5:34 pm

Obviously, first and foremost I agree with SlamClick's advice in the previous post. Taking that into account, my experiences with the Seneca should be taken with a reasonably pinch of salt. I flew in icing conditions a surprising amount of times during my short time on that aircraft, and we were instructed to wait for at least 1/4 inch build up of ice before cycling the boots. As a result of following this rule I am still alive today and that comes after flying in some pretty atrocious conditions.

The 'topic' itself does not have one clear answer, like many that are discussed here. As most aeroplane systems vary quite markedly, it is wise to follow the particular procedure given to the aircraft you are flying.
 
LimaFoxTango
Posts: 1031
Joined: Wed Jun 16, 2004 11:33 pm

RE: Waiting For Ice To Form Before Using Boots?

Sat Mar 24, 2012 3:35 am

Quoting flyhossd (Reply 5):
So in the case of the Dash 8, the boots are anti-icing equipment (like the ATRs)? Just to be clear, the boots on the ATRs are ANTI-ICE boots and are turned on at entry into icing conditions.

Boots are considered de-icing equipment on the Dash 8.

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