Runback ice formation

[Vaneev]

Dear colleague, could you explain expression " runback ice formation". Is it recurrent ice sediment on the wing after shedding or possible strike pieces of shedding ice against stabilizer, or anything else?
Thank you and good luck!

[Longhitter]

Not an expert, but the documentation I have read on it describes it as the following:

It's ice that forms on the upper and/or lower surface of a wing/tailplane aft of the heated leading edge, either as a result of switching the heaters on after ice has previously formed on the leading edge or as a result of supercooled water droplets first freezing and then melting and running back towards the area aft of the leading edge and then refreezing.

Hope this answers your question.

[Boingboingdriver]

correct,

It may happen if pilots dont realize that wing anti ice switch should be used as DEICE and not ANTIICE whenever airborne.
So if wing antice is used prior to entering icing conditions, upon entry,frozen particules will melt in contact with the heated surface, melt and refreeze on the back of the leading edge.

Capt STD:E

[Old Fella]

Runback Ice Formation generally occurs when thermal de-icing systems are used. The ice on the de-iced section of the airfoil melts and if it is not shed in sheets it tends to run back from the de-iced area and refreeze. As distinct from pneumatic de-icer boots, which crack the ice rather than melt it, thermal de-icers are best used as anti-icers, i.e., apply the heat as soon as icing conditions are encountered to minimise ice accretion.

[Denti]

Probably type dependend. Our documentation from Boeing indicates we should wait until we have around 1 inch of ice on the leading edge before we switch thermal wing anti ice on and then switch it off as soon as ice has been shed. So basicly an intermittent operation that has to be done manually as the 737 doesn't do it automaticly.

[Bullethead]

Question for those with more experience than me in freezing weather operations, how often have any of you actually used wing de/anti-icing in a swept wing jet aeroplane? I've been flying them for 26 years, all over the world, and used engine anti-ice frequently but I've never had to use wing de/anti-ice.

Just curious.

Regards,
BH.

[Vaneev]

I encounter heavy icing conditions almost every year. This year it was in Vienna, but most frequently it happened over Russia and Ukraine. And I was have to use wing de/anti-ice.
Regards

[Denti]

Yup, even in the middle of europe you have to use wing anti-ice quite often throughout the year. If you're unlucky and you have to hold in icing conditions (not that uncommon during the cold time of the year) you even might have to use ice shedding procedures to keep engine vibration to an acceptable level, and better follow correct wing de-icing procedures there or you will get runback icing, and that is not funny at all.

[Bullethead]

Vaneev & Denti.

Thanks guys.

I must be living a charmed life, admittedly I don't get to fly in the northern hemisphere in winter very often though.

Regards,
BH.

[PEI_3721]

Runback ice can be associated with large super cooled droplets, Aircraft Icing Handbook (http://www.caa.govt.nz/safety_info/GAPs/Aircraft_Icing_Handbook.pdf) pages 7 & 91, also see ‘clear ice’ page 2.

[barit1]

Runback ice has also been reported in engine inlet ducts; It melts off the heated highlight area and runs back & refreezes ahead of the engine airfoil OD.

[Castle Don]

Just to keep this going ad nauseam.... Runback Ice can occur on propeller blades also, causing significant thrust losses.

Personally, I have only seen it associated with composite blades, where the heat from the electrical leading edge "mat" doesn't get conducted back into the body of the blade.....therefore the melted ice runs back and immediately re-freezes.