Icing two questions.

[160knots]

• Just looking at some Stats:
  
  AVTUR – Freezing point -47C
  
  Aviation Turbine Kerosene AVTUR- Freezing-50C
  
  JET A- Freezing point -47C
  
  I am told the fuel temp at high altitude drops to the minus 20’s, so why does one fuel need PRIST and the other not? Surely all fuels contain some dissolved water including JET A.

• From an earlier thread why isn’t the

Tailplane heated?

[NutLoose]

If you are talking military Avtur on the tanker after the spec F40 or F34 you will normally see FSII after the F40 this means the fuel has fuel system icing inhibitor already blended into the fuel..

this may help

http://www.nato.int/docu/logi-en/1997/lo-15a.htm

[Mad (Flt) Scientist]

* From an earlier thread why isn’t the Tailplane heated?

Assuming you're talking about de-icing/anti-icing, compared to the wing, it's all a question of the design necessity.

the performance implications of designing for ice on the wing are horrendous - significant reduction in maximum lift coefficient, affecting stall speed and hence all scheduled speeds (V2, Vref, etc) AND large amounts of drag. It's far more effective to take the hit in engine thrust associated with the bleed or power offtakes to power an anti-ice system for the wing, than it is to try to design an aircraft with no icing protection.

The tail, however, is usually a different story - it's more practical to design for ice on the tail than the wing; the drag implications are far less significant, as it's a much smaller surface, and the impact of reduced CLmax is much smaller - depending on other requirements, you may not even need to 'oversize' the tail. The case where tail de-/anti-icing is most commonly needed is the manual controls aircraft, because tail ice can significantly affect elevator hinge moments, and that can cause control problems. But an aircraft with hydraulically powered controls can usually cope with ice on the tail.

Caveat I'm talking in all cases about the en-route icing cases - typically the double-horned leading edge shapes. I am IN NO WAY advocating takeoffs with ice adhering to the tailplane on any aircraft.