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SWAFO, question for you here - Paton - 28-07-2005
As a general rule, when do you use them? I know that pitot heat heats the pitot tube used for the pitot-static system instruments. But I am not sure
when you are supposed to use it.
And also, what exactally should you do if you notice oil temps or oil pressure rising?
Post Edited ( 07-28-05 08:32 )
Re: Another question concerning pitot heat and anti-ice. - silo - 28-07-2005
Anybody feel free to add (or correct), of course.
For the wings If I'm not mistaken, anytime the OAT is -20 to 0 and there's visible moisture in the air. Need to double check though. Keep in mind that even if the outside temperature when you enter the clouds is +10 celsius, at the wing the temperature drops because of the venturi effect (faster air speed, lower pressure, lower temperature). And that's why sometimes in GA aircrafts u still put the carb heat on even if the temp is +20 C (if the humidity is above 80%), because in the carburetor at the venturi the temp will be lower.
Basically I turn on anti-ice (wings and engines) when the temp is between -20 and +10 and there's visible humidity.
You know, SWAFO could give a real world answer.
Post Edited ( 07-28-05 05:37 )
Re: SWAFO, question for you here - silo - 28-07-2005
"And also, what exactally should you do if you notice oil temps or oil pressure rising?"
Reduce power setting, reduce climb rate (if you are in a climb of course), increase airflow over the engines (and mixture fully rich if you are in
a piston a/c). If temp keeps rising, stop the climb momentarily, reduce power to cruise and start praying.
Double check with the pressure. Good pressure and high temperature is sign of gauge error.If the pressure is dropping too and you smell hot oil through the speakers, you might want to prepare to declare an emergency and look for a suitable airport for landing as the engine is
about to substain damage.
Sorry if I keep answering your questions, there's nothing on TV tonight
Post Edited ( 07-28-05 09:03 )
Re: SWAFO, question for you here - fruitfly - 28-07-2005
Here's another one:
What stands behind the 'cost index' within FMC and what values to use?
Re: SWAFO, question for you here - nem - 28-07-2005
Generally speaking it's an index for fuel cost and influences how economically the FMC plans fuel use. Most airlines use 30-50 if i'm not mistaken.
Re: SWAFO, question for you here - Ryanamur - 28-07-2005
Quote:silo wrote:
Anybody feel free to add (or correct), of course.
For the wings If I'm not mistaken, anytime the OAT is -20 to 0 and there's visible moisture in the air.
Basically I turn on anti-ice (wings and engines) when the temp is between -20 and +10 and there's visible humidity.
You know, SWAFO could give a real world answer.
I personnally used to turn the pitot heat and carb heat on when the OAT got to about +10C and all the way down to -47C (never flew at temps colder then that!
). Visible moisture or not. Don't forget that in a venturi the temp drops so you might not have visible moisture outside but air might reach saturation and condensate in your carb!). The pitot heat will only affect your altimeter by a few feet so it's much better to have it on then to lose your altimeter. Now, about the anti-ice, it totally depends on which kind of system you are using. But, to my knowledge, they should only be used when there is an
indication that icing is taking place (ie: don't leave it on for the whole fligtht). I've personnally used two types: liquid and air expansion.
Liquid is obvious, you shoot a liquid from a reservoir to get rid of the ice. This is usually used to de-ice propelers. Since it's coming from a
reservoir, you don't want to waste it. Hence you only put it on when you are flying in icing conditions and you ask ATC to clear you to an altitude
where there is no icing.
The air expansion is usually to de-ice surfaces like the leading edge of your wings. Again, you want to wait until the ice has formed to activate it.
Once activated, your leading edge expands and the ice falls off. Once the ice is off, you turn it off. If you leave it on all the time, the ice will
just form around the expanded surface and you'll have a bitch of a time trying to get rid of it...
Post Edited ( 07-28-05 15:03 )
Re: SWAFO, question for you here - SWAFO - 28-07-2005
Once again, listen to Phil... for the most part he know's what he's talking about... lol.
Lot's of questions... let me see if I can give you some answers (remember, all my answers are 737 type specific):
1. Q: As a general rule, when do you use them? I know that pitot heat heats the pitot tube used for the pitot-static system instruments. But
I am not sure
when you are supposed to use it.
A: Pitot heat is used anytime the engine's are running. Normally, we'll shut it off just prior to parking at the gate. You're right about it
heating the pitot/static tubes. We want to keep them warm, since at our cruising altitudes we regularly have temperatures in the -50 to -
100 degree F range. Pretty cold up there (the wind chill makes it even colder), and the last thing we want is icing around our pitot/static
tubes that feed information to the instruments... that wouldn't be too good, as we'd have erratic or incorrect (if any) readings.
2. Q: what exactally should you do if you notice oil temps or oil pressure rising?
A: Usually, oil temperature and pressure will fluctuate by a small amount constantly while in flight (in FS, everything is always the same
between both engines... not very realistic). If we notice any increase in pressure or temperature (of any system for that matter), we'll
monitor the condition to see if it's a normal occurence, or if it's going to create an abnormal condition. If it appears to be a non-normal
situation, we'll follow our aplicable checklists, and contact dispatch for advisory. They make all the final decisions in route deviation/flight
termination, etc.
3. Q: When do you use anti-icing?
A: On the 737 we have two types of anti-ice. We have the wing, and engine (nacelle) anti-ice systems. The engine anti-ice systems
have very simple operation, and will be activated any time we can detect visible moisture, and the outside air temperature is below 10
degrees celsius. Visible moisture includes rain, snow, clouds, sleet, etc. So, we'll usually use engine anti-ice during takeoff and landing
if it's raining/snowing and below 10 celsius. We'll use it during climb/cruise/descent if we are encountering any clouds or precipitation
and the temperatures is below 10 C... very easy operation. Now for the wing anti-ice. We can choose to utilize this system as a de-icing
mechanism, or anti-icing, depending on the conditions, and time/duration of use. We'll only use this when encountering moderate or
more severe icing with visible precipitation outside. Typically, I'll use this in short durations as an anti-icing device. This way, I'll flip it on
and off from time to time when encountering the conditions it's specified for use in. You can also use it as a deicing mechanism.
Whenever you detect visible icing on the leading edge of the wing that requires removal (not thick enough for ground de-icing), you can
use the wing anti-ice to basically burn it off. The last example won't really apply in FS (unless there's a gauge or something that allows
you to detect icing, in which case I need to know about it! lol). By the way, some aircraft can takeoff with wing anti-ice, some will have it
trip off when taking off. It's not desirable during takeoff since it uses a lot of bleed air.
4. Q:What stands behind the 'cost index' within FMC and what values to use?
A: Cost index is just what Nem said it was. It's basically a variable that allows the company to have control over our fuel economy.
Lower numbers are more economical, while higher numbers are less economical. I believe the range is 1-1000. Here at Southwest, all
flights use a cost index of 36. What this number does is basically determine our ECON (economy, or best value) climb, cruise, and
descent speeds based on atmospheric conditions/cruising altitude. Normally, we'll stick to these numbers, but if we need to make up
time (which means burning more fuel to go faster), or if we have some extra time (which means saving the company money, using less
fuel... happens rarely), we'll use manually inputted climb/cruise/descent speeds (usually quite a bit faster than the ECON speeds). With
rising fuel prices, these numbers have been dropping rapidly at many major carriers.
I think that answers all of them for now... let me know if you have anymore... happy to help.
Re: SWAFO, question for you here - Ryanamur - 28-07-2005
Quote:SWAFO wrote:
Once again, listen to Phil... for the most part he know's what he's talking about... lol.
I only know what I know and I know enough to know that I don't know all that I should know!
About the windchill: it's a little more complicated than just saying it's really cold with the windchill!
The problem with the windchill is that it's not a real temperature. It's an equivalency rate! For example, if the temperature is 5C out and you have a
windchill of -5C, you will NOT have ice formation because the coldest the item will reach will still be 5C (for a stationary object). The windchill
only indicates that the object will lose its heat at the same rate as if it was -5C... but the temperature of the object itseft will not dip below 5C
therefore you cannot have ice formation!
About the anti-ice system on the 737, I'm sure that at 70M a pop, the anti-ice system inflates and deflates automatically on a set timer! Meaning it's a turn on and forget device. Right?
Phil
Post Edited ( 07-28-05 16:54 )
Re: SWAFO, question for you here - silo - 28-07-2005
Quote:I personnally used to turn the pitot heat and carb heat on when the OAT got to about +10C and all the way down to -47C (never
flew at temps colder then that! ). Visible moisture or not. Don't forget that in a venturi the temp drops so you might not have visible
moisture outside but air might reach saturation and condensate in your carb!).
Hi Phil, I never spoke of visible moisture for the carb, instead I mentioned the percentage of relative humidity. The visible moisture was
regarding icing on the wings.
"And that's why sometimes in GA aircrafts u still put the carb heat on even if the temp is +20 C (if the humidity is above 80%), because in
the carburetor at the venturi the temp will be lower."
After reviewing some info from my books I'd like to add this: "Carburetor icing is more likely to occur when temperatures are below 21C
(70F) and relative humidity is above 80%. However, due to the sudden cooling that takes place in the carburetor, icing can occur even
with temperatures as high as 38C (100F) and humidity as low as 50%."
Basically we are saying the same thing. I just wanna make sure that you know that I know and that I only know what I know and I know enough to know that I don't know all that I should know!
Post Edited ( 07-28-05 17:31 )
Re: SWAFO, question for you here - Ryanamur - 28-07-2005
Quote:silo wrote:
Hi Phil, I never spoke of visible moisture for the carb, instead I mentioned the percentage of relative humidity. The visible moisture was
regarding icing on the wings.
Yep, you're right, you never did mentioned the visible moisture. Sorry I read your post quickly.
Thanks for the actually numbers for the carb heat... I'll make sure I modify my procedures since I was wrong there!
Phil
Re: SWAFO, question for you here - silo - 28-07-2005
Yeah I didn't remember that detail either!
Check your inbox in 5 mins...
Re: SWAFO, question for you here - SWAFO - 28-07-2005
Phil,
When I mentioned windchill and the cold temperatures, I meant that it would feel cold as hell if you stepped outside the aircraft at
40,000ft. lol. I didn't mean that it increases ice formulation. Sorry if I came off as misleading.
As for the wing anti-ice system... yes, it does have trip-off features (based on duct temperature logic, etc.), however it's not really a set
and forget feature. As I mentioned, we'll normally use it as an anti-ice system, with one minute (approximately) applications while
encountering icing conditions.
One thing I forgot to mention about engine anti-ice... it's not required when climbing or cruising with the temperature below -40C. At the
relatively high thrust settings during these stages of flight, the anti-ice system supplies heat for protection against the accumulation of ice
in the inlet section of the engine (if it's switched on). During operation in lower thrust ranges and under moderate to severe icing
conditions, the engine thrust will occasionally be increased to provide sufficient heat for short periods of time. There are also minimum
N1 settings that must be maintained when using any TAI system.
Re: SWAFO, question for you here - Ryanamur - 28-07-2005
Quote:SWAFO wrote:
Phil,
When I mentioned windchill and the cold temperatures, I meant that it would feel cold as hell if you stepped outside the aircraft at
40,000ft. lol. I didn't mean that it increases ice formulation. Sorry if I came off as misleading.
No problem, most people actually have the misconception that because the windchill is -40 outside that the air temperature is also -40 because of the
wind.
Cheers
Phil
Re: SWAFO, question for you here - Paton - 29-07-2005
Thanks for the replies fellas. I guess a lot of icing depends on the dew point spread as well. If I understand it correctly, if the spread is small,
then air hitting a very cold surface, like say the wing of an airplane, it will condense and possibly form ice? Is this correct?
Re: SWAFO, question for you here - nevinch - 29-07-2005
Actually, I do have another RL question for you. In regards to lights...can you describe when/where you turn on all the lights.
I keep seeing different methods and in FS the ability to fly different aircraft doesn't help because configurations are so different.
But, take the 737 as an example. I understand you are supposed to turn on your beacon lights before firing the engines and of course
landing lights/strobe when taxiing onto runway.
But, what about all the others?
Thx in advance
Chuck