With the Northern Hemisphere in the depths of winter, Dr Foster Ross, chief technical officer at Kilfrost – a global leader in de- and anti-icing – warns how ice is a danger which is all too often underestimated or misunderstood amongst the business jet and turboprop community. In doing so, Dr. Ross took the time to speak with World Aircraft Sales Magazine and answer some common questions on ice.Back to Articles
Â -Â Advice and guidance on de- and anti-icing for your aircraft.
With the Northern Hemisphere in the depths of winter, Dr Foster Ross, chief technical officer at Kilfrost â a global leader in de- and anti-icing â warns how ice is a danger which is all too often underestimated or misunderstood amongst the business jet and turboprop community. In doing so, Dr. Ross took the time to speak with World Aircraft Sales Magazine and answer some common questions on ice, and offer advice and guidance on safe winter flying.
WHEN DOES ICE FORM?
Generally the heaviest ice formation occurs when the water content in the air is highest close to 0ËC â this can prove to be particularly treacherous, because pilots often think that conditions are not cold enough yet to worry when the fact is that this is exactly the time to be concerned. As the temperature falls further, the air becomes increasingly drier producing less ice.
The main danger point for accumulation of ice tends to be when aircraft are on the ground, and every year we see a number of accidents caused when pilots fail to notice, or even ignore, ice or frost on a wing. Even a small amount can substantially degrade an aircraftâs performance.
WHY DOES ICE/FROST FORM?
Hoar frost is certainly one of the easier types to spot, but is all too often underestimated. It commonly accumulates on aircraft overnight, particularly when the sky is clear, and forms because the aircraftâs body becomes cooler than the outside air. This process is known as radiant cooling, and while only a few degrees difference is needed, itâs not uncommon for the aircraft skin to actually measure as much as 5ËC or, in very severe conditions, 10ËC less than the outside air temperature.
This is why frost will readily form on an aircraft even when the outside air temperature is as much as 4ËC above zero.
HOW SHOULD AN EFFECTIVE SAFETY CHECK BE CONDUCTED?
Needless to say that initial safety checks are imperative. You should give particular attention to critical surfaces like the wing â especially its leading edge as this is where the majority of the lift is produced. Visually check for ice deposits, but also run a finger over the surface to feel for any change to the smoothness of the wing edge.
It is not without good reason that the Civil Aviation Authority advises that your eyes and your hands are the best tools for checking for ice and frost.
WHY CAN ICE PROVE SO DANGEROUS?
When the leading edge becomes contaminated with ice, results have shown a reduction in the effectiveness of lift to be substantial. It isnât the weight of the ice which causes the problems, but the surface roughness. Even something thatâs only as rough as the finest emery paper is enough to cause a distortion of the aircraftâs aerodynamic properties.
After an accident in Colorado during the winter of 2004/2005, the NTSB in Washington studied the effect of ice build-up and found that while most pilots understand that visible ice contamination on a wing can result in severe aerodynamic and control penalties, many donât realise that even minute particles can result in similar penalties.
Their research showed that particles of frost or ice as fine as a grain of table salt and distributed as sparsely as one per cm2 over an aircraft wingâs upper surface can prevent enough lift to actually prevent it taking off. And according to their wind tunnel data, this level of frost and ice accumulation can cause lift losses of between 22% and 33% both on the ground and in the air.
Combine this loss of lift with other factors such as an aircraftâs load and the length of a runway, and it becomes much clearer why we see so many avoidable accidents every year.
HOW SHOULD YOU DE-ICE YOUR AIRCRAFT?
To de-ice an aircraft you need to remove the rough surface and leave the wings â particularly the leading edges â as clean and as smooth as possible.
There are various methods of de-icing and a number of products are available. On the ground, if youâre at a larger airport then you can make arrangements for your aircraft to be sprayed using the available heated and pre-diluted Type I fluid - but if you operate from a small or remote location it may not be viable to heat de-icing fluid, and you may not wish to make a significant investment in application equipment. This doesnât mean, however, that de-icing shouldnât occur.
Solutions, including Kilfrostâs RDF (Rapid De-icing Fluid), are ideal in these situations. A general purpose ground de-icier which reacts quickly and is used in cold concentrate form, the RDF doesnât require any preparation.
In terms of application, the back pack sprayers you can buy at most good garden centres will do a perfectly adequate job, and theyâre extremely cost-effective to purchase. Kilfrostâs RDF fluid has a low viscosity enabling it to spray easily, and dissolve the ice which then drains away. A small amount of fluid does remain on the wings, however as the aircraft takes off this shears completely away, leaving the wing clean and smooth for flight.
IN FLIGHT DE-ICING
For in-flight de-icing many business jets will be fitted with a TKS, or âweeping wingâ system. This works by dripping fluid at regular intervals from a micro porous strip on the leading edge of the aircraft, keeping it clear of ice deposits throughout the flight.
Small business jets that regularly fly at lower altitudes through cloud are liable to experience icing in winter, particularly with the growth of ice on the leading edges of wings. If left untreated, the accumulation of ice in-flight can endanger the safety of the aircraft, so ensuring you have an appropriate TKS fluid is critical to your safe operation. Again, Kilfrost produces a range of TKS fluids (see below).
Whichever TKS fluid you decide to use during the colder months, it pays to be winter- wise - taking that extra time to ensure the TKS de-icing fluid tank is regularly topped up before each flight and that the TKS system is functioning and serviced in-line with the OEMâs requirements.