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• January 20, 2017 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Effect of Ice and Frost Formations on Drag of NACA 651-212 Airfoil for Various Modes of Thermal Ice Protection

One of the most important problems associated with aircraft icing
is the effect of various-shaped ice formations on the performance of the
aircraft, specifically the effects of ice and frost formations on lift
and drag characteristics of airfoils. Establishment of these effects
will help determine (1) the design requirements of icing-protection
systems currently being developed and (2) the necessity for means of
preventing the accumulation of frost on aircraft surfaces prior to and
during take-off.

A study of the icing—protection requirements for high-speed, high~
altitude, turbojet-pOWered aircraft (ref. 1) indicates that continuous
heating systems for airfoils, designed to evaporate all the impinging
water for selected meteorological icing conditions, will result in pro-
hibitive loads on the available heat sources and large deterioration of
aircraft performance. As a means for reducing these high heat loads,
cyclic de—icing systems (refs. 2 and 5) have been proposed. Cyclic
de-icing systems, however, are subject to runback icing on the surfaces
aft of the heated areas (due to melting of some ice during the heating
period) and considerable leading—edge icing during the heat—off period.
The effects of ice formations on airfoil characteristics Were insuffi-
ciently established to permit an evaluation in reference 1 of the reduc-
tion in aerodynamic performance of aircraft equipped with cyclic de—icing
systems.

An evaluation of the effect of runback ice formations on airfoil
characteristics is also of interest for continuous heating systems. In
general, a continuous heating system is designed to evaporate the
impinging water for a particular icing condition; and if a more severe
icing condition is encountered, some water will not be evaporated, with
a consequent formation of runback icing. Furthermore, it is pointed out
in reference 1 that a considerable saving in heat can be accomplished
'for a continuous heating system if some runback icing can be tolerated
for a selected design meteorological icing condition. It.is of interest,
therefore, to ascertain whether the drag resulting from runback icing is
more detrimental to performance than is the propulsion penalty incurred
by supplying the additional heat necessary to evaporate all the imping-
ing water.