CIAM: the APD-A acrobat engine was tested in an inverted position 
The promising Circus The Russian piston aircraft engine APD-A, designed for aircraft of the acrobatic category, was tested in an inverted position, according to the Central Institute of Aviation Motors (TsIAM) named after Peter Baranov.
The organization notes that such “unconventional” tests are necessary to confirm the operability of the new installation and its systems (primarily lubrication and cooling) when performing reverse aerobatics. At present, the APD-A has been confirmed to operate in idle mode.
On the basis of the Yak-52 laboratory aircraft, the APD-A tests, created on the basis of the APD-500 aircraft piston engine demonstrator, are scheduled for 2022.
In October, RIA Novosti, referring to CIAM, reported that the Yak-18T aircraft with an APD-500 based on the power plant of the Russian Aurus car had passed pre-flight tests. During the tests, the engine showed stable operation and the ability to provide the necessary flight characteristics.