Spurred on by the high performance two seaters emerging from the German Akafliegs, like the SB 10 Schiroko, SZD modified the SZD-37x Jantar fuselage to take two seats in tandem and fitted the wings developed from the Zefir 4 to make the SZD-40 Halny.

This (flap) modification was a definite departure from previous (Zefir) attempts in variable wing geometry glider design.

Jerzy Śmielkiewicz[3] suggest that this was due to realisation that a laminar flow could not be sustained over the wing with (high speed retracted configuration) Fowler flap mechanism.

All upper surfaces at the hinge points are formed by continuous flexible seals preventing leak- through causing drag and turbulence problems with the ailerons and flaps.

The sole Halny, SP-2645 (c/n X-106), first flight in December 1972 flown by Zdzislaw Bylok, was used regularly into the 1990s before being retired to the Gliwice Gliding Club Museum[2] Data from [2]General characteristics Performance