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Jet aircraft: Trouble in Icing- What can you do?

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HawkerF/O

Well-known member
Joined
Dec 5, 2002
Posts
755
In response to the silly and senseless ridicule this guy got (http://forums.flightinfo.com/showthread.php?t=71599) for actually using this forum for something meaningful and educational, I thought I would follow his lead and do the same. If you don't like it, tough $hit!

1) So, you are stuck down at 6,000ft 40 miles from your intended airport of landing, picking up moderate icing at a pretty good rate and needing to land. No VMC within the range of your fuel or warmer WX to climb into, so you are going to have to fly around in the ice. Well, your wing anti-ice (Bleed Air) just signed off on both engines. It's gone for good. For whatever reason, a freak of nature failed the valves shut. How can you heat up those wings enough to keep the ice off? Be specific about what you can use, and how to use it to determine that you are not picking up any ice and shedding whatever ice you had on your wings. (Clue: In doing this, you'll shed ice from the entire airframe, not just the wings)

2) You are at altitude (FL390) and still in the clouds. All of your Anti-ice works just fine, but you don't want to use it so you can keep your speed up. At what point (what determines or what conditions(s) must be present) for you to know that is ok to leave the Anti-Ice off and by doing so you will not pick up any ice. In other words, what condition must be present in order for you leave the ice off? Remember, you are in the clouds (visible moisture) and since you are higher than FL240 it's well below freezing.

Both of these questions are actually pretty simple, you just have to think about them a little bit. Some of you guys probably know the answer, so it might be good to let a couple of guys that don't know take a stab at it. Good luck guys.................
 
...picking up moderate icing at a pretty good rate...
sounds redundant to me!

1) Most jets can handle that kind of icing no problem without anti-icing working. But if I was in the situation, I'd decend as low as possible, keep the speed up as much as practicable and land without delay.

2) At FL390, icing isn't a concern. The outside temp at that altitude will be somewhere on the order of -60C. Usually icing isn't a problem below -20C.
 
Could be like the 747...its doesnt have leading edge anti-ice.

Check your TAT gauge. Temps between -10 & +10 is where your gonna get ice.
 
Erlanger said:
1) Most jets can handle that kind of icing no problem without anti-icing working. But if I was in the situation, I'd decend as low as possible, keep the speed up as much as practicable and land without delay.
You are touching on it, but not there. Descending as low as possible, may or may not work for you. I assume you mean as low as safely possible. You might know it, but your answer is way too vague. Be more specific. From what you wrote, I'd say you barely make the field if at all. It would be close. Tell me more.

Erlanger said:
2) At FL390, icing isn't a concern. The outside temp at that altitude will be somewhere on the order of -60C. Usually icing isn't a problem below -20C.
Close, but the -20C is off. And still not specific enough. -20C what? Also, at what temp does Jet-A gel?
 
Last edited:
Thedude said:
Could be like the 747...its doesnt have leading edge anti-ice.
Nope, the airplane does have leading edge heat. Not a trick, but I like the way you are thinking.

Thedude said:
Check your TAT gauge. Temps between -10 & +10 is where your gonna get ice.
You are close, but I need more. So the guage reads 0C. So what? What now? You are very close, but you need to go into greater detail. I think you know it, but remember what we are trying to do here. Tell me more.
 
1) Accelerate to as close to M1.0 as possible...the compression will heat the leading edge up and melt the ice off.....ok I fly pistons, but think this will work.

2) At the altitudes you're talking about I don't think ice will be an issue...it's too cold, the ice has formed crystals already. I'll guess at -20ºC
 
At FL390 SAT will be below -40c, so you don't need the anti-ice. At lower altitude increase speed to the maximum possible to increase the TAT above +10c.
 
atrdriver said:
At FL390 SAT will be below -40c, so you don't need the anti-ice. At lower altitude increase speed to the maximum possible to increase the TAT above +10c.
Exactly! -40 SAT is the magic #. As for being down low, you are right, no manufacture has ever seen ice on the airframe at +11 or higher, so accelerate until the TAT reaches +10 or higher and you can fly around all day long and use the TAT as your Anti-Ice. Just keep it above +10 and you'll never get a hint of ice on the entire airframe and it will shed what Ice you have already accumulated.
 
HawkerF/O said:
You are close, but I need more. So the guage reads 0C. So what? What now? You are very close, but you need to go into greater detail. I think you know it, but remember what we are trying to do here. Tell me more.
http://72.14.203.104/search?q=cache:k6uSIY1VwrcJ:www.faa.gov/library/manuals/examiners_inspectors/8400/hbat/media/hbat9821.doc+wing+surface+temperature+rise&hl=en&gl=us&ct=clnk&cd=6

Slide down to appendix 3

Apparently, the faster you go, things warm up for you.
 
HawkerF/O said:
Exactly! -40 SAT is the magic #. As for being down low, you are right, no manufacture has ever seen ice on the airframe at +11 or higher, so accelerate until the TAT reaches +10 or higher and you can fly around all day long and use the TAT as your Anti-Ice. Just keep it above +10 and you'll never get a hint of ice on the entire airframe and it will shed what Ice you have already accumulated.
You might doublecheck your C500 manual...If I recall correctly, -30 is the magic number there.

Now, let's say it's -10C at 4000 feet...you need 20 degrees of ram rise to get to +10C. That requires a TAS of 390 kts, which, due to the colder than standard temperature, is a 400 knot INDICATED airspeed. I've never flown anything that allows more than 370 down there...ruh-roh, Raggy!

The guys I used to fly with who also flew Sabreliners said you just push it up to 300KIAS, and all the ice goes away...they never told me how to shoot an approach at that speed, though ;)

Fly safe!

David
 

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