AirJamPanAm From United States of America, joined Sep 2003, 248 posts, RR: 0 Posted (9 years 6 months 1 week 4 days 6 hours ago) and read 2339 times:
Can someone explain the rules regarding de-icing?
How much precipitation etc?
I remember last winter being on a CO flight at LGA that was being de-iced with about only an inch of snowfall in the middle of the afternoon.
I have to admit that scraping sound wasn't reassuring, but I guess it would have been better than that other sound when metal hits the ground.
What is that red stuff that was flowing over the windows during the process anyway?
thank you in advance.
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Pilotpip From United States of America, joined Sep 2003, 3082 posts, RR: 12 Reply 1, posted (9 years 6 months 1 week 4 days 5 hours ago) and read 2286 times:
The red stuff was de-icing fluid. Since they were getting snow off the wing it was more than likely Type 1. There are a couple types that are used. Type 1 being the thinnest and mainly used for initial clearing. The other two types, II and IV are more viscous. Those are used when it is nessesary to keep the fluid on for a longer period of time(ie departure).
Each airline sets it's own standards for hold-over time. This is the time that is permitted between the process and departure. It varies based on preciptation conditions, type of fluid used, temperature, etc. These times are in their ops manual. I can't really give specifics because they very and I don't know them.
One thing to consider. Air Florida had a DC-9 crash back in the early 80s in DC because of a miniscule amount of snow and frost on the wing. The captain wanted to get home and instead ended up hitting a bridge over the Potomac.
Avioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11 Reply 4, posted (9 years 6 months 1 week 4 days 1 hour ago) and read 2216 times:
The red stuff is most likely type IV "anti-icing" fluid.
It's non-newtonian in its flow characteristics meaning that it stays on the wings and forms a barrier so that the ice and snow won't get to the metal and freeze in place.
If you strike a newtonian fluid it acts like water and gets out of the way. It also flows downhill under all environmental circumstances.
Non-newtonian fluids act almost the opposite. They "stick" to the aircraft and the ice and snow are carried off the aircraft as it accelerates.
Non-newtonian fluids have a "shear value" which translates to a wind or airspeed where the fluid will start flowing and sluicing off the aircraft, carrying the ice with it. (It usually starts to flow off the plane at about 30 knots and is gone by 80).
That leaves clean wings and flight controls at V-1 for a safe departure.
That's the simple version. I can get a lot more complicated if you like. (It's a four to six hour class I give every year to the de-icing vehicle operators.)
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
Jetguy From , joined Dec 1969, posts, RR: Reply 9, posted (9 years 6 months 1 week 3 days 8 hours ago) and read 2098 times:
I have no idea where Steve went to, I'm curious as to the answer. I really don't think that it would be caused by cold-soaked airframes and condensation in Tucson - I've spent a lot of time flying into areas where that can be a real problem during certain times of the year. However, when the temperature - dewpoint spread is 30 degrees F. or greater it's not an issue. I'm not sure, but I don't think that you'd get a temperature of 110 degrees in Tucson during monsoon season and besides, he said "no rain for 6 months". I'm still guessing that it has something to do with the icing certification testing conducted by Bombardier. If that's not it I have no clue. I've flown to TUC a million times and I used to attend FlightSafety there for Lear recurrent. Needless to say, I've never needed to deice there before. Like I said, I very curious to find out the answer.
Avioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11 Reply 10, posted (9 years 6 months 1 week 3 days 1 hour ago) and read 2060 times:
Since they put the lake in Tempe, (just east of PHX) MD-80 wing deicing is frequently needed when the wind is from the east. Cold soaked fuel in the wings can make a lot of frost and ice before it warms up.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
Avioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11 Reply 12, posted (9 years 6 months 1 week 3 days ago) and read 2042 times:
It has to do with the fact that the lake provides moisture which causes frost and ice on the upper surface of the MD-80 wings.
It's ongoing and common. Not related to labor pains.
The -80 series wing is much more flexable than the other DC-9 wings. If any ice forms (which it does commonly) it tends to slough off on takeoff and destroy engine fan blades. That's why there's a "bare hand" preflight inspection requirement in effect for most airlines.
The links below will give a little more information.
Okie From United States of America, joined Jul 2003, 2355 posts, RR: 3 Reply 13, posted (9 years 6 months 1 week 2 days 23 hours ago) and read 2022 times:
I have seen the de-icing on a DC-10 and a S-80 on flights that I have been on out of DFW on AA when the temps were well above freezing.
I also read an accident report I believe on a DC-8 at ANK that attributed the accident to cold soaked fuel. The hypothis was that when the plane descended into ANK at low weight the plane passed though a cloud layer that deposited ice on the wings and was not noticed by the crew even though there was no precip on the ground at the time but the temp was right at freezing. Once refueled and back up to MTOW the plane fell out of the sky after leaving ground effect.
I wish I could remember the event and I would link it.
Jetguy From , joined Dec 1969, posts, RR: Reply 14, posted (9 years 6 months 1 week 2 days 22 hours ago) and read 2012 times:
We used to ice-up Lears flying into Atlanta. We were at altitude just long enough to cold-soak the airframe. We would pick up a boat load of ice as we descended into the moist air and the water condensated and froze on the airframe. It also made for some tough taxiing - the water would condensate on the plastic windshield and you'd completely fog up. The procedure was to turn on the windshield bleed air 45 minutes prior to descent, but it didn't help all that much - you would still have problems. About the only thing that helped were the STCed electric "hair dryers" that were mounted on the side window frames so as to blow warm air directly on the windshield. In the "pre-electric windshield heat" Lears, the only time you didn't have a visibility problem do to condensation was when the temperature/dew point spread was greater than 30 degrees F.
Actually, nothing would surprise me when it comes to icing - I once shot an IFR approach to minimums (blowing snow) in West Yellowstone Montana. On July 24th.
I'm still interested in hearing the answer to the trivia question.
L-188 From United States of America, joined Jul 1999, 29350 posts, RR: 62 Reply 15, posted (9 years 6 months 1 week 2 days 14 hours ago) and read 1970 times:
"Can someone explain the rules regarding de-icing?
How much precipitation etc?"
Well not really. And the reason is that every company will have a slightly different version of the rules approved in their Ops Specs.
Likewise each different chemical manufacturer will have a slight different instruction manual. And of course each aircraft will have it's own set of manuals with their own sets of instructions.
Rules of thumb are cold soaked wings, temperature below the freezing point, but it can get so cold that de-ice is not needed. Visible moisture, snow or ice build up on the wings.
I suspect that what you saw sprayed was Type I propylene Glycol. It would have a red or brownish orange color, which again will vary by manufacture or mix. It is the same stuff that is used in those "environmentally friendly" car anti-freezes and is also used as a food preservative. I have a bag of strawberry muffin mix that lists it as an ingredient. Keeps the berries in the mix moist I guess.
I'll give you a couple example.
One company I worked for allowed 1/4 inch of frost on the bottom of Cold Soaked wings. Another allowed 3/8 ths on the bottom surface.
One company had charts for type one mixture ratio's and sprayed different mixes dependent on weather conditions. Another company just sprayed 50/50 because that was all that was available at the remote site.
One company had the rampers performing the De-ice, another it was Maintainence's job.
I suspect that the reason for the spray in Tucson happened was simply because the manual said it had to be done. Alaska used to have (and may still) a policy of always spraying the wings of their MD-80's down on short turns.
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Deltamike172 From United States of America, joined Mar 2001, 67 posts, RR: 0 Reply 17, posted (9 years 6 months 5 days 23 hours ago) and read 1865 times:
Going back to the Air Florida 737 incident.
Its tough not laugh when you read the NTSB report. Instead of pulling off into the deice pad to get deiced after a half hour or so, the captain decided (to save time) they'd pull up close behind the aircraft they were following on the taxiway and let the engine exhaust do all the work. This actually made the it worse by creating a thick slush on the leading edge of the wings, and if the captain had just let the snow be, without trying to "deice via exhaust" he may have had enough power to get out of there OK. It also didn't help that they NEVER firewalled the throttle... reguardless of their known EPR gauge problem. Don't laugh, almost everyone died.
Apparently, Flow control was created becuase of this incident, so that planes don't wait in line for more than 10 minutes. Some pilots just don't want to skip out of line after the alloted time to deice again, and then be put back at the end of the line. (this is why the Air Flordia captain elected to use the plane in front of him).