Messerschmitt AG.
Quick test flight of the 109 G radiator Test Report
109 18 L 42
 Date 9.9.42
 Dept. Flight Testing

Reason:The permissible water temperature was raised for climb and reduced for high speed flight by Mr. Generaling. Eisenlohr with telex Nr.6596. This has the consequence, that now the critical flight condition for the assessment of the radiator sufficiency is no longer the climb as before, but rather high speed flight.

Procedure:Measurement of the coolant temperature and speed in fast flight with combat power at different radiator positions.

Results:The tested radiator is sufficient at high speed flight near the ground for European summer temperature with an acceptable speed loss. However, for tropical conditions, it is completely inadequate, since the flaps open fully already at +42°, which causes a speed loss of 48 km / h. At an air temperature of +50° + 5° the coolant reaches 115°. This temperature is not permissible because high speed flight combat power can last longer than 10 min.

Details:See Test Report No. 109 10 T 42 1.Partial report.

The turned aluminum radiator 9 - 6098 was measured. Setting of the kinematics on the stand:

          closed front 70 mm rear mm 0
          open front 92 mm, rear 305 mm

Results:The measured speed and the temperature difference between air and water temperature are plotted over the flap opening on sheets 3 and 4. Sheets 5 and 6 plot, as a function of outside air temperature, the loss of speed which results, if the radiator flap position is regulated to achieve the specified temperature of 102 ° (according to the behaviour of an ideal thermostat). Specific flap positions are given for certain points. Since the flaps do not close completely because of their flexing, a small loss of speed exists, even at temperatures below normal temperature.

It should be noted that the speed decreasing as the temperature increases is not only due to the larger radiator opening. It is superimposed by the effect of the change in specific weight of the air and the engine performance. This dependence is illustrated on sheet 7, on sheet 5 and 6 it is not taken into account for simplicity.

Augsburg, den 9.9.42

  Messerschmitt AG. Flugerprobung.          Gruppe: Leistungen           Bearbeiter: Kaiser

Schnellflugvermessung des Wasserkühlers 109 G (pdf)

WWII Aircraft Performance   Me 109 G Flight Tests