Using engine anti-ice when dewpoint spread 3 degrees or less
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From: Norway
Using engine anti-ice when dewpoint spread 3 degrees or less
How many operators out there use engine anti-ice after engine start when OAT is +10 C or less and dew-point spread is 3 degrees or less, regardless of visibility or precipitation? And why or why not?
Joined: Mar 2000
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From: Arizona USA
Generally do, in the L1011.
Not +10 however, plus eight.
Not just after start however, on the parallel just before (or after) extending flaps.
And no, doing everything before taxiing is not my idea of how it should be done, unless the intended taxi route is very short.
Why do I use engine anti-ice?
Because it's there to be used.
However, if the visibility is reduced, on it goes just after start.
Seems prudent to me.
Not +10 however, plus eight.
Not just after start however, on the parallel just before (or after) extending flaps.
And no, doing everything before taxiing is not my idea of how it should be done, unless the intended taxi route is very short.
Why do I use engine anti-ice?
Because it's there to be used.
However, if the visibility is reduced, on it goes just after start.
Seems prudent to me.
Joined: May 2000
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From: Seattle
The 3 deg Temp-Dewpoint spread is part of the definition of "visible moisture" in our FHB (747 Classic/GE). We use nacelle anti-ice in that situation.
Since the air pressure drops somewhat as the air is sucked into the intakes, it is possible for moisture to condense and freeze as it cools below ambient. At that temp there is seldom a problem with any reduced thrust due to A/I, so it's a good idea to use it.
Some engines/installations are more susceptible than others. Follow the guidance in your books.
Since the air pressure drops somewhat as the air is sucked into the intakes, it is possible for moisture to condense and freeze as it cools below ambient. At that temp there is seldom a problem with any reduced thrust due to A/I, so it's a good idea to use it.
Some engines/installations are more susceptible than others. Follow the guidance in your books.
Thread Starter
Joined: Aug 2007
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From: Norway
Thank you, Intruder! Exactly my point why it is important to use engine anti-ice when the dew-point spread is 3 degrees or less! I belive I have read that the combination of high engine RPM and low airspeed is the key here.
Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
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From: Hampshire, UK
I have never seen this. My B737 Operations manual says no such thing. Previously my B747 Flying Manuals for RB211 and P&W models (747-100,-200 and -400) had no such definition. Simply +10C and below and visibility 1500m or less with visible moisture. I have never heard this 3 degree split mentioned.
I'm not saying it is wrong, but no engines are experiencing any problems when not operated that way!
I'm not saying it is wrong, but no engines are experiencing any problems when not operated that way!
Joined: Aug 2002
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From: Switzerland, Singapore
There are different operators that handle the anti-ice thing differently. But it also depends on the aircraft. Dew point spread is a very common way of defining visible moisture, but always comes as a combination with something, i.e. OAT.
Some airlines define it with a visibility (say 1.5km) plus a temperature. If your spread is small, chances are that you have bad visibility. This of course can only be obtained close to an airport (where dew points are regularly transmitted).
Some airlines define it with a visibility (say 1.5km) plus a temperature. If your spread is small, chances are that you have bad visibility. This of course can only be obtained close to an airport (where dew points are regularly transmitted).
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From: vancouver oldebloke
The temp/dewpoint 3degree spread is a holdover from the first Jet era..The DC8/9 used this as an antiicing guide(pratt witneys).The vis moisture below plus 8 was used at this time.After the 'Palmair'crash at Washington the FAA went to a straight Vis.moisture below plus ten,although I see in some of the business jets manuals plus 8 is still a reference..
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Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
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From: Hampshire, UK
Dew point spread is a very common way of defining visible moisture
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From: Florida
The KISS principal should be followed
The idea is not to get pilots to think too much, else they don't read the manuals. The safe side to be on is the 10 degree safety bar in visible moisture. As was stated earlier when engines suck they depress the temp in the inlet.
Lots of problems with ice forming in engines and not on the wiper blades etc.
When I last checked, all the manuals for consistency in the big iron recognized this. I'll keep my eyes tuned for changes in this forum and check this out if the manuals are not consistent.
The idea is not to get pilots to think too much, else they don't read the manuals. The safe side to be on is the 10 degree safety bar in visible moisture. As was stated earlier when engines suck they depress the temp in the inlet.
Lots of problems with ice forming in engines and not on the wiper blades etc.
When I last checked, all the manuals for consistency in the big iron recognized this. I'll keep my eyes tuned for changes in this forum and check this out if the manuals are not consistent.
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From: Insert something funny here==>__________
This is how my OM B defines Icing Conditions (Fokker 100)
On ground icing conditions are present when OAT is below +6 deg C and
In flight icing conditions are present when TAT is below +6 deg C down to and including -25 deg C AND visible moisture is present.
... it may not be like Boeing but I most certainly still will be going...
On ground icing conditions are present when OAT is below +6 deg C and
- Spread is less than 3 deg OR
- Visible moisture is present OR
- Taxiways and/or runways are contaminated or wet
In flight icing conditions are present when TAT is below +6 deg C down to and including -25 deg C AND visible moisture is present.
... it may not be like Boeing but I most certainly still will be going...
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From: inside of a pretty bustard
they are
1.atmospheric icing conds. when temp is below +5*C on ground (OAT) or below +7*C in flight (TAT) and any moisture observed ,visibilitiy below 1 mile or any precipitations etc...
2.ground icing conds. when OAT is below +5*C and on taxiways or runways it exists patches of water ,slush , snow etc.
now,before performing the de-icing / anti-icing, you have to take in account the real temp.(necessary for type of fluid and ratio) and HOT (hold over time), wich depends of temp and the weather(freezing fog, rain, snow ,sleet) and HOT starts at the same time with the beginning of de-icing operations.
1.atmospheric icing conds. when temp is below +5*C on ground (OAT) or below +7*C in flight (TAT) and any moisture observed ,visibilitiy below 1 mile or any precipitations etc...
2.ground icing conds. when OAT is below +5*C and on taxiways or runways it exists patches of water ,slush , snow etc.
now,before performing the de-icing / anti-icing, you have to take in account the real temp.(necessary for type of fluid and ratio) and HOT (hold over time), wich depends of temp and the weather(freezing fog, rain, snow ,sleet) and HOT starts at the same time with the beginning of de-icing operations.
Joined: Sep 2001
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From: Right Here
3 degree split
Hi, for my 2 cents worth.
For about 5 years, around the turn of the century, on our Jurrasic 737-200s the company SOP included the procedure of Anti-Ice ON when OAT at +10 C or below and dewpoint within 3 degrees. I was told that this was a problem on the 727, mainly the centre engine, and with some of our tech guys having a wack of three holer experience, the same limitations were applied as a precaution. Around 2002 IIRC, this was dropped with no noticeable problems after the change, though I think the JT8D made and ate a lot more ice under normal ground operations than most people realise.
For about 5 years, around the turn of the century, on our Jurrasic 737-200s the company SOP included the procedure of Anti-Ice ON when OAT at +10 C or below and dewpoint within 3 degrees. I was told that this was a problem on the 727, mainly the centre engine, and with some of our tech guys having a wack of three holer experience, the same limitations were applied as a precaution. Around 2002 IIRC, this was dropped with no noticeable problems after the change, though I think the JT8D made and ate a lot more ice under normal ground operations than most people realise.
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From: Insert something funny here==>__________
But if it's not Boeing, why would you want to be goeing?
And what about the bit between +6 and +10 deg C? Why would you Fokkers be free of icing there?
On a more serious note....
It seems to me that in aviation there are SOPs based on solid scientific facts and there are those based more or less on religion.
Maybe this difference +10 and +6 deg is based more on religion than on scientific findings.... This is just a thought from someone who has just the minimum of knowledge on these issues.
So my question to all of you is: Could it actually be possible that it doesn't really matter if you select engine anti ice at +10 or +6? Or is there actually a difference between different engine types and how prone they are to icing?