I've noticed that when climbing through clouds my indicated airspeed will go to zero.I check, and the probe heat switches are on. The problem remains until I turn on the anti-ice (wing and engine) switches, and then the airspeed comes back.I'm assuming that the PMDG has coded the pitot heat call to FS in with the anti-ice switches as opposed to the probe heat switches, but would like that confirmed.Also, will it be fixed in the -800?

While on the subject of anti-ice, can I jump in with a question?In which conditions should wing anti-ice be used?The AOM gives all the specifics for situations where engine anti-ice should be used (and where I do my flying it gets used alot) but doesn't give details for wing anti-ice.Can anyone shed any light on this for me?ThanksDavidP.s. Sorry for hijacking your thread Timothy :)

David, wing Anti-ice should be used when temps are below 10 degrees Cel. Wing anti-ice should never be used on the ground. The reason for this would be that engine bleed air going through the wings is too hot for the slow taxi speeds EG: no relative wind over the wings. The wings need cooling from airflow when wing anti-ice is on. the best thing to do is to keep your engine anti-ice on, and when your on your climb out turn on the wing anti-ice on. I hope this clears some of your questions.Jasonhttp://www.precisionmanuals.com/images/forum/checkcapt.jpg

Hey Jason,So basically use it any time you need to use engine anti-ice, except when on the ground.Thanks for the info and explination :)CheersDavid

Yeah that sums it up well. Also anytime the temp is below 10C, except when on the ground. http://www.precisionmanuals.com/images/forum/checkcapt.jpg

Wing anti-ice should always be ON when temp below 10 C or when standing ice, snow or water is present.The 737NG has thremal switches preventing wing overheat.As stated in the OPs manual:http://forums.avsim.net/user_files/67695.jpgCheersAndy

Use wing and engine AI with temps below +10 C and with visible moisture. If there is no visible moisture, the AI is not used.Cheers,JohnBoeing 727/737 & Lockheed C-130 Mechanichttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

"I check, and the probe heat switches are on. The problem remains until I turn on the anti-ice (wing and engine) switches, and then the airspeed comes back."I ran some checks, Tim and I couldn't reproduce your findings. The NAI/WAI switches had no effect on the instruments, the Probe Heat switches always did (allowing for a minute or two delay for the icing to have an effect... I set my icing to "Moderate").Unfortunately, I can't explain why you are getting this.Cheers.Ian.

Tim, are you using FS METEO or Active Sky?[h4]Best Wishes,Randy J. Smithhttp://www.precisionmanuals.com/images/forum/betaimg.jpg

>> Tim, are you using FS METEO or Active Sky?>>>[h4]Best Wishes,>Randy J. SmithAS2004, yes

Tim,I'm using AS2004 MR1 and my findings are a little different than yours.I never have icing problems using only the pitot heat switches. If I switch on the engine or wing anti-ice switches while the pitot heat switches are on, then I get a drop in airspeed. So I make a habit of always cycling the pitot switches after enabling or disabling the engine and/or wing anti-ice switches.Bruce

>Tim,>>I'm using AS2004 MR1 and my findings are a little different>than yours.>>I never have icing problems using only the pitot heat>switches. If I switch on the engine or wing anti-ice switches>while the pitot heat switches are on, then I get a drop in>airspeed. So I make a habit of always cycling the pitot>switches after enabling or disabling the engine and/or wing>anti-ice switches.>>>BruceHmm... maybe it's a problem with the FS heat position and the PMDG switch position being out of sync. What I'll try next time is to cycle the probe heat on and off and on again.

While the procedures for engine anti-ice typically call for it to be activated for temps less than 10 degrees C with visible moisture present, that isn't necessarily the case for activating the wing anti/deice system.For example, here are the procedures from the manufacturers Operations Manual for the airplane in question:"The wing anti-ice system may be used as a de-icer or anti-icer in flight only. The primary method is to use it as a de-icer by allowing ice to accumulate before turning wing anti-ice on. Thisprocedure provides the cleanest airfoil surface, the least possible runback ice formation, and the least thrust and fuel penalty. The secondary method is to use wing anti-ice prior to ice accumulation. Operate the wing anti-ice system as an anti-icer only during extended operations in moderate or severe icing conditions, such as holding. Ice accumulation on the flight deck window frames, windshield center post or on the windshield wiper arm may be used as an indication of structural icing conditions and the need to turn on wing anti-ice. Normally it is not necessary to shed ice periodically unless extended flight through icing conditions is necessary (holding)."Don S.

I wonder if the problem is related to excessive icing in FS9 Tim ?I have had IAS drop to zero using ActiveSky even with the pitot heat on (they get switched on as aprt of the ground checks).If you have a registered version of FSUIPC you can limit the icing by setting '3' in the appropriate box (check the docs). Doing that I have not had IAS drop to zero.I have never used wing AI for the simple fact that FS gives you no visual clues when in icing conditions, unless I am worng. Also does FS9 simulate wing icing and does the PMDG 737 react to any wing icing?Dave