| At first flights for tuning the
blinds in the intake air lines at the mixture regulator and at the
boost regulator were done. A boost of 1.65 ata was to be reached
after switching to second charger gear, which was accomplished by a
blind of 1.5 x 2.0 Ø at the mixture regulator and 1,5 x 1,8
Ø at the boost regulator. |
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| Both power levels (normal power
and increased power) were flown in immediate succession. 4 cylinder
head temperatures, outside air temperature and flight time were
recorded by the means of a four channel recorder, while boost and speed
were read from the boost gauge and the speed indicator by the pilot at
predetermined altitudes. The accuracy of the measurements, including
the values read from the gauges, was very good, all values could be
exactly reproduced in repeated flights. |
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| I.) |
Speed increase (annex 1)
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1.) |
Level speeds:
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The test aircraft had to be
designated a fast machine, which obtained already at sea level
at normal emergency power 550 km/h and at 5.2 km altitude with
increased emergency power vw = 680 km/h. Annex 1 shows the speed plot.
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2.) |
Power: |
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The related power are also
plotted and were calculated from altitude test bench under
consideration of ram pressure on the intake air temperature and full
throttle altitude, the outside air temperature difference to INA and
engine power loss. A follow up check of the speed change with
v2 / v1 = N2 / N1 accounting for exhaust thrust with the power, the speed variances were below 0,5%.
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3.) |
Fuel consumption:
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The given fuel consumption was
calculated from the measured boost, the aneroid temperature, calculated
from the measured outside air temperature, and the adjustment chart.
The shallow return curve shape at high boosts resulted in full flow
rate in first charger gear up to 0.9 km and in second charger gear from
switching altitude to 5.5 km at the increased boost setting. As can be
seen in the annex, the specific fuel consumption in second supercharger
gear at increased boost at higher than normal temperatures is higher
than normal, while it is lower than normal in first supercharger gear.
But no thermal overload is to be feared in case of lower than normal
temperatures, since the set up of the blinds for the second
charger gear only allows up to 1.58 ata boost in first charger gear and
enough cooling is guaranteed in fast flight. |
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4.) |
Cylinder head temperatures:
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Head temperatures were measured
at the cylinders 8, 9, 11 and 12, where temperatures on cylinder 8 were
lowest and on cylinder 9 were highest. In full throttle altitude second
supercharger gear the highest temperatures result, which on the hottest
cylinder for summer would be 216°C and for the tropics would be
226°C and would pose no threat for the short flight duration.
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| II.) |
Time to climb reduction (annex 2)
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1.) |
Time to climb
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The time to climb is plotted over altitude, where the normal climb performance n = 2400 rpm, pL
= 1.32 ata was compared to the increased climb performance n = 2700 rpm, pL=
1.65 ata. The climb times were 12'17" and 8'38" respectively. While the
time to climb reduction in a climb from 0,0 km to 8,0 km of
3'39" is small as an absolute figure, this is a decrease of 30% because of the generally low time to climb of 12'17".
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2.) |
Power and fuel consumption:
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Power and fuel consumption were
determined in the same way as described under I. Also for specific fuel
consumption the conditions as under I apply.
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3.) |
Cylinder head temperatures:
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The cylinder head temperature was increased by 13°C
on the hottest cylinder compared to normal combat power and was
211°C in 6 km altitude, where outside air temperature was equal to
summer conditions, so that for tropical conditions 221°C result.
The flight speed was Va = 265-270 km/h and the cooling flaps were opened to "position 3". |
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4.) |
Oil temperatures: |
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The oil inlet temperature was increased from 73°C
to 88°C (permissible for 15 min 80°C) by the increased climb
power when reaching 8 km altitude. Since the outside air temperature
was equal to highest summer temperature, this value is permissible for
a short time. But the oil temperature has to be regarded as a criterion and only a larger test basis can make a final decision possible. |
