| 1. | The reworked engine cooling flap design of the front side flaps left and right, i.e. the replacement of the so far existing three small by two larger flaps with an opening angle of 33°, resulted in a significant increase of the cooling pressure drop inside the cylinder block as well as the cooling pressure in front of the cylinders in climbing flight with combat power.
As can be seen in sheet No. 1, there was an increase in Δ p* of about 60 ./. 70 mm H2O, so that now the required pressure drop for 220° cylinder temperature for the TS-engine (possibly also for power increase with MW 50 or GM 1) exists with fully opened flaps.
However, it is advisable, preferrably by the company BMW, to reassess the values with the apropriate cylinder temperature measurements.
The pressure increase in front of the cylinder block of 40 ./. 60 mm H2O was probably caused by improvements of the cooling fan efficiency and air flow conditions inside the engine compartment due to higher air flow in this flight condition.
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| 2. | In level flight (sheet 2) with closed cooling flaps it could be determined, that the new design has a better airtightness. The cooling pressure drop is 60 ./. 70 mm H2O lower when compared to the old flap design and the pressure in front of the cylinder block is 30 ./. 50 mm higher.
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| Nonetheless, with this measure as well as the aerodynamic improvement of the panel in front of the windshield, no significant speed increase could be determined. The level flight results with combat power (sheet 3) are (0 ./. 5 km/h) higher than previous measurements which is within the uncertainty of measurement.
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| The new cooling flaps cause significantly higher trim changes compared to the old installation. For example, a take off with open flaps required an extra 2° of tail heavy trim. There was no flutter with open flaps. The cooling flaps gear is worse. In spite of the small gear ratio it is harder to operate. Starting from the "Open" position, the flaps are hard to move in the first third, easy to move in the second third and very hard to move in the last third towards the "Closed" position. In the last part operation is only possible in jerks and with changing of grip. Because there is no stop and the deflection at the rear flaps is too soft, the tension in the closed condition can be increased up to the deformation of parts in the cooling flaps gear.
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| 3. | The Tanklafette 300 is unusable in its current layout, because sideway forces are insufficiently supported.
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| See telex to Mr. Klemm dated 15.12.44 and 10.1.45.
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| 4. | Unsuspended installation of the trim indicator was all right in the test version. Durability of the instrument remains to be seen.
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| Replacement of rubber elements in the suspension of homing indicator and additional artificial horizon with springs is impossible due to strong interference with the indications.
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| See BSK 190.9-1201 and telex to Mr. Klemm dated 12.1.45.
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Langenhagen, 20.3.45
GT/Schw.
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