stalled, each having the same volume as the

internal tank, i.e., 35 liters.

Although even such an extensively modified

aircraft did not take the Czechoslovak pilots

to the top places on international aerobatic

scene, it gained popularity with pilots and series production yielded 45 of this variant. In

addition to many famous Czechoslovak solo

aerobatic pilots who flew the Z 526 AFS, the

era of the Box Trenér group, consisting of Jiří

Tlustý, Božej Struž, Antonín Klimenda and

Laco Trebatický, culminated in 1982.

The total lifetime of the “Shorty” is 4500 flight

hours, however, it can stay in the aerobatic

category for a maximum of the first 1000

hours. Logically, the question arose how to

deal with the remaining 3500 hours. It was

solved by Aerotechnik, where the calculations, approval and the first conversion of

OK-ZRB to the AFS-V towing version were

carried out. Subsequent conversions were

carried out at the Trenčín Aircraft Repair

Works, where overhauls of these aircraft

were also carried out, as fourteen were produced in total. The rebuilding included the

modification of the instrument panel, from

which the no longer needed accelerometer

and inverted bank indicator disappeared.

Instead, a signal control button was added

to check the function of the newly installed

bell. This indicates the approach of stall speed or idling with the landing gear retracted.

The idle warning with retracted landing gear

was later changed to a horn, which, however,

has no control button in the cockpit and its

function can only be checked in flight. The

aircraft must also be equipped with a fire

extinguisher and a rear-view mirror. A visible feature of the converted aircraft is also

the installation of an oil cooler with NACA

air inlet in the left engine cowling. Of course,

the entire conversion could not be possible

without installation of an approved towing

device, for the emergency drop of which a

tow handle was added. It is located on the

March 2022

left between the seat and the side of the

cabin, dangerously close to the emergency

undercarriage opening handle... With few

exceptions, towing aircraft have permanently mounted auxiliary tanks. Apart from

the possibility to carry double the amount

of fuel, their installation reminds the pilot

clearly enough that the aerobatic career of

the aircraft in question is over. At the same

time, the “tanks” improve the aerodynamical

characteristics of the wing by reducing its

induced drag. The disadvantage is the free

movement of fuel through the system, so the

“Shorty” with wing tip tanks usually stands

tilted to one side.

Most of the Z 526 AFSs were sold to Poland

– a total of 17 units. This was followed by the

GDR, where 11 of them went, two each to Romania, Hungary and Italy, and one was sold

to the FRG. In Czechoslovakia, 16 examples

of “Shorty” were originally operated. The history of these will be presented in the next


The and www.gonzoaviation.

com webpages were helpful sources of information. We thank both for kind cooperation.

INFO Eduard


Photo: Richard Plos

In a new role