DM-2 by A.Merkulov

amjet engine, used as booster on combat aircraft. Installed under the wing (lower on biplanes like I-152), pair of those engines provided ~20km/h of extra speed. But when engines were not operating, both speed and flight characteristics of the aircraft suffered severely due to additional drag (applied in the quite a wrong place).

More powerful DPM-4 in 1940 accelerated the I-153 to 440km/h at 2000m, but it was impossible to save biplane fighters from their faith.