Flight Report Fw 190/783
Nr. 4
Werk Flughafen 

Date: Flight. Nr.: Take-off: Landing: Pilot:
11.3.1943 59 1538 1548 Beisinger
15.3.1943 60 1554 1610 Bartsch
16.3.1943 61 1413 1535 Beisinger

Engine BMW 801 D2/20208
Tight engine cowling.
Split flaps with opening angle indicator.
px and Δ px measuring equipment
Armament 2 MG 17, MG 2 151, with ammunition.
External or internal intake supply ducts.

1. Record the cooling pressure drop in climb and level flight with combat power with external and internal air intakes
2. Record the cooling pressure drop dependent on speed and the split flaps opening angle at n = 2400 rpm.

The tests were carried out here in order to clarify the question whether the split flaps can be re-closed partially or entirely without exceeding the allowable cylinder temperatures above the cylinder temperature reversal heights during climb with combat power.

Since this evidence could not be provided by direct measurement of cylinder temperatures due to too great difficulties, the required cooling pressure gradient was taken as a reference. As the comparison of the flown Δ px values with requirements for hottest European summer day by the engine manufacturer shows, the cooling pressure drop with internal air intake ranges from not quite to nearly sufficient in climb, while the use of external intakes result in a certain, albeit at a higher altitude is only slight excess. It follows that a reduction of the cool air outlet cross section by operating the split flaps above 7000 - 8000 m cannot be made.

As the plot of the Δ px values determined in level flight with closed split flaps shows, even here the required cooling pressure gradient no longer exists, for internal intake above 9300 m and for external intakes above 9950 m, so that from the altitudes stated the split flaps must be opened slightly. However, as the flaps are not closing 100% if the pre-load is not constantly checked and readjusted, and a small opening angle already creates an adequate drop off, these measures should not occur.

The following consideration applies to normal inner air intake duct. With GM 1 - addition there is not enough Δ px generated with existing production fan, so that an increase of the cooling air outlet cross section or at higher altitudes a more pressure-creating fan is necessary.

With the present design, in climb with open split flaps, with GM 1, a sufficient Δ px could be created by increasing the speed, for example, at 8000 m from 260 to 310 km/h (see graph 2), however, then, while taking in account the speed increase by ~ 80 g/sec GM 1 addition, at approximately 10300 m, the speed is equal to the level speed achieved with combat power, and thus the limit is reached.

Level flight with GM 1 with closed split flaps, taking into account a Δ px increase of 20 to 25 mm water column due to the speed increase from GM 1, result in the need to open the split flaps from 8500 m on more and more with increasing altitude in order to obtain a sufficient cooling pressure gradient, whereby the speed gain due to GM 1 - addition for the most part is lost again.

The limit here is also in ~ 10300 m, where the split flaps are fully open, in addition, the Δ px required can not be provided, so that, as already mentioned, a greater outlet cross-section or a variable fan becomes necessary.

Langenhagen, 7. April 1943


Flugbericht FW 190/783 Nr. 4 (pdf)

Translation by Jörn Dietrich and Mike Williams

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