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The accident occurred while performing an airline while performing an introductory flight with a potentially interested candidate for glider training. The flight had been announced and approved and then performed according to VFR rules and VMC conditions.

In the take-off phase and initial climbing after take-off, at the altitude of about 20 meters, there was a partial engine failure and a drop in engine power on the plane, after which the pilot made a slight turn to the left, and then, without announcing it, unhooked the glider. After the turn, the plane returned and landed undamaged on runway in the opposite direction, and the unhooked glider made a forced landing in a partially controlled flight on an inadequate terrain and suffered extensive damage. One person suffered minor injuries.

Based on the investigation, analysis of gathered evidence and available information on the accident, the Commission made the conclusion that the main causes of the accident were the following:

1)      Partial engine failure in the take-off phase and initial climbing after the take-off,

2)      Procedural errors of the dragging plane pilot in the emergency situation due to partial engine failure in take-off and initial climbing after take-off with the glider

The accident was caused by:

a)    Use of inadequate fuel (automobile gasoline – additive) on own initiative in conditions of extremely high external temperatures,

b)    The use of uncertified fuel despite the explicit notice/prohibition of the manufacturer and service for its use,

c)    potentially possible vaporization of fuel as a result of high fuel temperature in the tank and fuel delivery system to the engine,

d)    insufficient experience of the pilot to use uncertified fuel,

e)    insufficient knowledge of the Pilot’s Operating Handbook (POH) fir this type of aircraft and engine operations in regular and emergency situations

f)     unhooking the glider without noticing by radio or visual signals,

g)    delayed reaction of the glider pilot in applying the procedure in case of rope breakage or detachment from the aircraft, and in particular the absence of rope uncoupling after the pilot has understood the situation,

h)    poor aircraft features in terms of towing and climbing speed (about 200 feet/min), i.e. unequipped with a towing propeller but a standard larger pitch propeller.

Full report can be found on the following link.