In June 1942, Petr Biskup served in the 71 IAP-KBF. This unit was at the time equipped with a mix of I-16s, I-152s and I-153s.

On 8 June 1942, Biskup and Kapitan Konstantin Solovev from 71 IAP-KBF claimed a shared Ju 88 while flying I-153s.

In the evening on 31 August, kapteeni Eino Luukkanen led five Brewsters of 1/LeLv 24 to a search in the Seiskari-Lavansaari area. In a clash with eight Chaikas, half of them were claimed shot down into the sea over Lavansaari. The claimants were vääpeli Eero Kinnunen (BW-382) (18:50-20:00), ylikersantti Reino Malin (BW-373) (19:50-20:00) and kapteeni Luukkanen (BW-393) (19:50-20:05). The fourth was claimed between 19:50-20:05 as a shared between luutnantti Kai Metsola (BW-375) and ylikersantti M Pellinen (BW-376).
The Soviets reported that Kapitan Biskup’s four I-153s from 71 IAP-KBF were patrolling over Lavanssari, when they were attacked by 12 Capronis and Fiats. RS-82 rockets were launched in the first head-on firing which split the enemy formation. The attacked then continued in pairs and also from head on. After one such enemy turn, Biskup and Starshiy Leytenant A. Gruzdev scored hit on one Caproni, which went into the sea. After 20 minutes of fighting 12 additional Capronis appeared on the scene and also four I-153s from 71 IAP-KBF. In repeated attacks two more Capronis were damaged with rockets and machinegun fire, and they then broke off to Someri direction. One of them could not make it and fell into the sea.

Biskup ended the war with 2 shared biplane victories.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1942
	08/06/42		½	Ju 88	Shared destroyed	I-153			71 IAP-KBF
	31/08/42	19:50-20:05	½	Buffalo (a)	Shared destroyed	I-153		Lavansaari	71 IAP-KBF

Biplane victories: 2 shared destroyed.
TOTAL: 2 shared destroyed.
(a) Claimed with RS-82 rockets in combat with Brewster Buffaloes from 1/LeLv 24, which claimed four I-153s without losses. 71 IAP-KBF claimed two and one damaged Buffaloes without known losses.

Sources:
Airmen of World
Suomen Ilmavoimat part IV – 1942 – Kalevi Keskinen and Kari Stenman, 2007, ISBN 978-952-99743-2-0