As we move into the colder part of the year, we begin to consider winter weather and its implications for aviation here at GoFly. Whilst it’s not all extra chores and precautions – the winter months offer some of the most spectacular and breath-taking flying days – there are a few key extra points that all students and private hirers should be aware of. In the first of a four-part article series on winter aviation, we look at ground de-icing.
It’s often the case during winter that aircraft parked overnight outside start a new day with a layer of frost deposited on any surface not covered up. Any frost on an aircraft’s exterior surfaces is a hazard to safe flight; studies have shown that an extra layer of frozen water on an aircraft’s wing, equivalent to a layer of rough sandpaper, will reduce the lift produced by that wing by up to 40%. The frost will also produce more air resistance, and therefore overall the aircraft aerodynamics are adversely changed.
This produces, in practical terms, a longer runway take off distance, a degraded climb rate, more power required to maintain cruise speed (and therefore an higher rate of fuel consumption), and a stall speed increased by up to 30%. In addition, under some circumstances, a frost covered aircraft could suffer a tail plane stall, and become uncontrollable in flight. It’s safe to say there are no positive benefits! In effect, a pilot flying an aircraft with a contaminated wing has become a test pilot (whether they hold the relevant qualifications or not), as the aircraft’s handling qualities and performance are now unknown and untested.
It is possible to encounter icing whilst airborne, with similar effects to ground frost; this will be the subject of another article later in this series. However please note that inflight icing should be avoided, especially at the day VFR PPL level!
Happily, there is a simple and highly effective solution for ground de-icing; to remove the frost prior to flight. It should be noted that this does mean all the frost; pilots should not dismiss a thin layer as inconsequential, or rely on it being dislodged during the take-off run. Even a deceptively thin layer can be a danger, and airflow is highly unlikely to remove it.
One simple method is to turn the aircraft to face tail into sun. For an early morning start at Old Sarum, this normally means positioning the aircraft so that it points nose towards the Control Tower or Café, leaving no part of the wing or elevator in shade. As the sun rises, the frost will then start to melt naturally. Excess loose frost should also be scraped or brushed off as the aircraft is warmed by the rising sun.
For any remaining harder frost, or on those rare days in England when the sun isn’t shining, a specialised de-ice fluid is used. This is sprayed onto the exterior skin of the aircraft, left on for a certain amount of time, and then brushed off, taking the remaining frost or ice with it. We have sufficient stocks of this for the winter season – if used in the correct way (there are no restrictions on use of the de-ice fluid, but it is possible to use too much fluid to achieve the desired result – at much greater expense!).
If you’ve not yet de-iced an aircraft, then the Operations staff or a friendly instructor will be happy to show you the correct method. De-icing may be a chore, but it does allow safe flying on glorious winter flying days; the oft-clinched “gin-clear” day provides fantastic visibility, and crisp, smooth flying conditions. And if you’re lucky enough to be able to aviate after significant snowfall, then the snow-covered countryside offers some marvellous vistas, and a unique perspective on them from the cockpit of a PA-28.
Happy winter aviating!
Ben Koprowski, FI