June 24, 201411 yr WAI is really more de-ice in that you let it build and then remove it. I don't think the WAI on the 737 works like that. What you describe is how boots work on older airplanes, and the NGX doesn't have wing boots. The WAI can remove ice, yes, but i think it's best used to prevent ice buildup. Maybe someone with more technical knowledge can give us a better idea. Cristi Neagu
June 24, 201411 yr Commercial Member I don't think the WAI on the 737 works like that. What you describe is how boots work on older airplanes, and the NGX doesn't have wing boots. The WAI can remove ice, yes, but i think it's best used to prevent ice buildup. Maybe someone with more technical knowledge can give us a better idea. Have a look at his avatar... He flies the 737 for Alaska (the plane in question, in an area that has its fair share of icing conditions). I have a feeling he knows what he's talking about. :wink: Kyle Rodgers
June 24, 201411 yr Have a look at his avatar.. What's that at his avatar anyway? [color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]
June 24, 201411 yr Have a look at his avatar... He flies the 737 for Alaska (the plane in question, in an area that has its fair share of icing conditions). I have a feeling he knows what he's talking about. :wink: That's inside information right there... Cristi Neagu
June 24, 201411 yr Commercial Member What's that at his avatar anyway? I'd forgotten it was so far zoomed in. It's one of their planes painted up to look like a salmon: http://www.nycaviation.com/newspage/wp-content/uploads/2012/10/salmon1-1024-620x413.jpg Kyle Rodgers
June 24, 201411 yr I'd forgotten it was so far zoomed in. It's one of their planes painted up to look like a salmon: http://www.nycaviation.com/newspage/wp-content/uploads/2012/10/salmon1-1024-620x413.jpg :lol: That's one crazy livery. [color=#a9a9a9][size=1][size=4][img]http://forum.avsim.net/public/style_images/flags/rs.png[/img][/size] Lj. Prodanovic[/size][/color]
June 24, 201411 yr Re: Icing I was surprised how WAI was run, too. I flew turboprops for about 7000 hrs before I started flying the B737. On the turboprop, we were cruising around in the teens in prime icing conditions. We'd run the boots most often as a deice, but sometimes put them in a timer mode to cycle every 90 seconds or so. (I forget.) The jet screams out of the worst areas of icing and up into the blue above. Or at least the -40C. Here's what typically happens: you're climbing out and it's just below 0C TAT. Maybe you notice a trace ice on the wiper bolt. No problem. As you climb through the tops of the clouds, there's some moderate ice and the windshield gets a patch in the top inside corner. That prompts you to look out at the wing. Sure enough, there's a coating on the leading edge. No problem, you're out of it in a few seconds, anyway. When you're in the clear, a quick shot of WAI gets rid of the ice on the 3 inboard slats. I've never had an issue where the 737 was noticeably affected by icing. The turboprop was much more critical for icing. Don't run WAI above around FL350. You'll lose your packs possibly and pressurization. I've never run the WAI for more than a few seconds at a time. I'm sure that jets do encounter bad icing and need to leave the WAI on, but I haven't seen it yet. And yes, my avatar is the Salmon Thirty Salmon. That paint job is amazing up close. The scales have glitter. Pretty cool. Matt Cee
June 24, 201411 yr Commercial Member The scales have glitter. Pretty cool. haha - seriously? That had to cost a pretty penny since the FAA has to bless all of that mess... Good info on the rest, too! Kyle Rodgers
June 24, 201411 yr It's a lot more complex than that: Weight, temp, pressure, thrust setting (presumably, you wouldn't be using de-rates if you're doing a bleeds off, but that doesn't mean that you can't), wind, and runway contamination are all factors. Programs like TOPCAT could give you more precise values. I'm using topcat but you have to select the Air con off option but don't have the tools to know when to do it... Vernon Howells
June 24, 201411 yr Commercial Member I'm using topcat but you have to select the Air con off option but don't have the tools to know when to do it... You don't really need tools to tell you... Calculate the takeoff with bleeds on. If it works, then you're fine. If it doesn't work and tells you that you're limited by something, try to re-calc with bleeds off. If that works, then run a bleeds off takeoff (but make sure you're familiar with the procedure to get everything back online after takeoff). Bleeds off is somewhat of a last-ditch effort to get out of a tough (short or high altitude) airfield without kicking passengers off. If it doesn't work, you'll have to reduce weight (this is one of the reasons why airlines have to bump passengers occasionally). Again: Try to understand the concepts behind things before launching off into new territory :wink: The concept behind bleeds off is to throw more thrust out the back end of the engine. Now, think about when this would be necessary, and why it would make a difference. Then, act appropriately. Kyle Rodgers
June 24, 201411 yr Thanks kyle i have fs2crew to help me out on deck! Kyle i have also got PFPX looked at your tutorials you never mentioned the OBS(A) theres a few different ones but my thinking is Taking off to clear obstacles ? Vernon Howells
June 24, 201411 yr Very interesting. This IMO shows the actual complexity of the subject. I thought WAI on T/O would be a "no go", no matter what... Even if selected ON, the Wing A/I isn't actually active during takeoff itself. The valves close if either thrust lever goes above the takeoff config warning horn switch position. On older Boeings the wing A/I is in flight use only.
June 24, 201411 yr Re: Icing Don't run WAI above around FL350. You'll lose your packs possibly and pressurization. hey there Spin737, can you please elaborate more about this particular case? I'm curious. Thanks! -E Enrique Vaamonde
June 25, 201411 yr hey there Spin737, can you please elaborate more about this particular case? I'm curious. Thanks! -E Sure, but this is from memory. The WAI, TAI, and Pressurization are the three biggest users of bleed air. At higher altitudes, there's not enough bleed air for the demand from the 5th stage and so the 9th stage air opens up, too. The 9th stage air is too much hot air for the system so it causes a bleed trip on one of the sides. That in turn causes an even bigger demand on the remaining engine's bleed, so that one closes, too. Two successive bleed trips and now you have no bleed for pressurization. The WAI is just too much for the system at altitude. Matt Cee
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