What are icing conditions within clouds when talking about flying?

Question

I am studying flying and have just read this and i do not understand what icing conditions are or how they affetc an air craft.

This non-instrument rated pilot had the presence of mind and skill to control his Cessna 150 after entering instrument meteorological conditions (IMC). Icing conditions in the clouds quickly overcame the airplane. The pilot was seriously injured when the airplane impacted the ground. Read the details in the NTSB accident report.

Answer 1

All I know is that when the TAT is less than 10* C and we're entering visible moisture, the engineer turns on the anti ice.

Think that's about all I need to know actually.

Answer 2

Am not sure about the figure but I remember our instructor telling us around 30,000feet up temp. is -40 and here exist the icing condition you mentioned.

here wing anti-ice is switch-on, nacelle or engine cowl lip is heated so as to prevent ice formation on the engine cowl lip which maybe ingested and might cause damage. Of course windows are already heated (even at ground with minimum heating and airborne at max heating. Also if the fuel is equipped with a fuel heater it is also turn-on.

Answer 3

when da windows ice

Answer 4

If you are in visible precipitation (rain, clouds, or fog with visibility less than 1 mile) and the static air temp (SAT) is below 10C you are technically in "icing conditions".  Does that mean ice is going to form?  No, but it may.  By the way, the reason you need to worry about precip in temps above freezing is that on jet engines the pressure drops as the air is accelerated in the intake.  This pressure drop causes a corresponding temperature drop.  Even though the ambient temperature is above freezing it may be below freezing in the intake.  In carbureted engines the danger is in the pressure/temperature drop in the carburetor venturi.

If the airplane is moving fast enough, friction with the air will cause a temperature increase in proportion to airspeed and this will inhibit ice formation on the wings (think of the space shuttle glowing red hot as it enters the atmosphere at high speed - that's an extreme example but the same thing happens during high speed flight).  This is called total air temperature or TAT.  Although nothing regarding icing is written in stone you typically don't have to worry about airframe icing unless the TAT is below freezing.  At any rate, you can SEE airframe icing so there won't be any doubt if you're getting any.

As far as airframe icing goes it depends greatly on the liquid water content of the cloud.  Sometimes I was flying in a cloud and the TAT was just right for icing (just a little below freezing) and I didn't get any.  You just never can tell for sure.  Whenever the TAT was slightly below freezing and I was in one of those really thick coulds where you can hardly see the wingtip I knew almost before I looked at the wing that I was going to get ice.

For ice to form you must fly through supercooled water.  That means the drops are still liquid but are below freezing.  If it's cold enough (usually below -20C SAT) ice will probably not form because the precipitation is usually frozen at this point and will not collect on the airplane.  Again that -20C temp is a GENERAL rule.

Answer 5

Hi Paul -

At certain flight conditions - generally flying in sleet at near freezing temperature - ice will quickly form on the leading edges and trailing surfaces of airfoils, thereby destroying the lift that is generated by the original shape of the airfoil. Ice can also shed and be ingested by the engines or it can interfere with the operation of flight control surfaces.

I have only personally had one incident that really got my attention - flying into MacDill AFB in a T-37 through thunderstorms. The canopy iced over in seconds, so I could only see out to the sides. When I looked there, all I could see was ice forming on the wings, so I stopped looking anywhere but the instruments. Since the T-37 has no anti-icing systems, the procedure was to change altitude to get out of those conditions. I got clearance and descended to a place where the ice melted, but the aircraft was noticeably sluggish until I lost the extra weight and the non-flying geometry. Bad news.

Answer 6

8 degrees C and below and visible moisture, i.e. snow, rain, fog, clouds, is icing conditions, At any airspeed or altitude.