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Engine BMW 801 D2/25543.
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Old fan with wide rectangular blades or
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new fan with narrow rectangular blades.
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Tight engine cowling
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Split flaps with reinforced actuator
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Armament: 2 MG 17, two MG 151 (without ammunition).
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MG FF belt hatches.
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Maintenance-free undercarriage pre load springs.
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Operable wheel doors.
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Flap actuator without synchronization and coasting
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(no take-off position).
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Armored ring mounting in accordance with BSK 897
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Oil cooler 140 x 6/7 with 10 mm air outlet gap
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without cover.
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| Program:
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| 1. |
Recording the pressure before and the pressure drop in the radial cylinder with the old and new fans in climb and level flight.
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| 2. |
px and Δ px as a function of rpm and ram pressure at different heights.
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| 3. |
Check of oil temperatures with low power and very low outside air temperatures.
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| Results:
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| 1. |
As a preliminary
investigation for the aircraft with GM 1 - accessory (non-pressurized
liquid) the cooling pressure gradient was measured with two different
fans in climb and level flight at combat power (n-2400 U / min). The recorded values of the cooling pressure gradient for the old fan are, for unknown reasons, lower, compared to the measured results, laid down in Flight Report
190/711 No. 2, to be precise in climbing corrected to 0 m height by
50 mm water column.
An increase of 40 mm water column was achieved with the new fan, (see
graph) so that the installation of this fan in the GM 1 machine is well worth it.
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| 2. |
The cooling pressure gradients obtained in level flights at steadied speeds with various rpm are shown on the attached graph for the corresponding altitudes.
The speeds obtained here correspond to the plotted values in Flight Report 190/711 No. 2.
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| 3. |
On the basis of a complaint by the troops, after which
the motor runs with too cold oil at very low outdoor temperatures, the
oil temperatures were determined with stock oil cooler thermostat (switching
temperature ~ 57°) compared to Rö 11 with a switching temperature of 65
+/- 5° for 8000 m altitude with
low power:
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190/711 |
Production thermostat
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Production radiator 140 x 7/8
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Cooling air outlet gap 10 mm without cover
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HB = 8000 m, n = 1700 rpm, tL = - 40°, töKA=48°
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190/711 |
Production thermostat
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Production radiator 140 x 7/8 with cover
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Cooling air outlet gap 10 mm with stock cover
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HB = 8000 m, n = 1700 U/min, tL = - 40°, töKA=54°
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190/382 |
New thermostat (switching temperature 65 + - 5 °)
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Experimental cooler 140 x 6/7
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Cooling air outlet gap 15 mm with stock cover
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HB = 8000 m, n = 1700 U/min, tL = - 40°, töKA=58°
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Although a direct comparison
is not possible due to the different conditions and the different
machines, the following statement can be made: In spite of the radiator
140 x 6/7 with better cooling effect as well as the 15 mm air gap, the
cooler outlet temperature is ~ 4° higher when using the new thermostats
and when using a 10 mm gap should be increased so far, that the installation of the proposed
Rechlin 3 mm cooling air gap does not seem necessary.
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Since the steady-state temperatures were flown at high
altitude with relatively low ram pressure, slightly lower oil
temperatures are to be expected at similar temperatures and flights
near the ground. However, please note that the oil is heated up by
another ~ 5° prior to the engine inlet and that this temperature is shown by the standard Fw-measuring point.
Further experiments in these areas are to be conducted with the GM 1 -
machine.
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