Documentation
Models / Plans


The SZD-8 "Jaskółka" Series and its development




On the 7th February 1950 at the Experimental Department for Gliding in Poland, a meeting was held with the participation of engineers and pilots for which the topic was the definition of technical specifications for the construction of two gliders, a single and a two-seater. The result of this deliberation gave rise to the "Bocian" and the "Jaskółka".They agreed to build the "Jaskółkas", according to the following initial approximate specifications.

The prototype "Jaskółka" was to be designed by the Gliding Department test team under the direction of MSc. Tadeusz Kostii. The Glider had to be able to carry out soaring flights and perform full aerobatics with ease and also be able to fly in cloud.

The Glider was to be designed with a cantilevered mid wing, which could easily accommodate the pilot and his luggage in carriers set in the wing fairings. The tetrapezoidal wingform wing had a convergence of l:3.5 and an aspect ratio of 18.8. The wing had mechanically operated fowler flaps operating as flaperons for half of the tilt of the flaps as well as having Schemp-Hirth type aerodynamic air brakes. The canopy frame construction was to be made to be opened by retracting backwards. Special emphasis was placed on the rapid assembly and disassembly of the sailplane by automatically connecting wing surfaces and the folding tailplane controls direct to drive attachments built into the side of the fuselage. Further considerations were:-

  • Construction and equipment was to be the same as for the then state of the art modern sailplanes
  • rubber tyred wheels with brakes,
  • aerodynamic brakes
  • split ailerons with wash-out
  • integrated handles for lifting the rear of the sailplane during ground handling
  • a comfortable seat with adjustable belt tightener,
  • adjustable control pedals in flight
  • a joystick with a balance spring
  • a good set of flight instruments (9 pieces)
  • oxygen apparatus available during flight
  • a device to compensate for flight control lines shortening in low temperatures at high altitudes.

After the start of the project it was later moved to a workshop at Bialej.

On the 21st September 1951, the test pilot Adam Zientek (left) made the first flight of the SZD-8 "Jaskółka" bearing production number 071 and registration marks SP-1222. He started the arduous testing period, during which it appeared that a number of the innovative devices had brought more problems than benefits. Namely:

  • Pedal adjustment proved to be very difficult in flight, circling flaps cumbersome to use , seat belt tightener was faulty in operation, drives actuators for the ailerons, flaps and aerodynamic brakes were too stiff and steerability and lateral control was incredibly difficult in flight. Comparative trials with the "Mucha" glider showed that the "Jaskółka was better than the "Mucha" at high-speed and was more able to the cope with new tasks given out to contest glider pilots. In contrast, a very serious defect of the glider was that it would easily enter a flat spin and when recovering from the spin, the forces on the joystick were so great that the pilot, Adam Zientek, bent the joystick by 30˚, with the result that when the controls were in neutral, the joystick was touching the side of glider. The pilots skills prevailed and the glider was landed safely.

In view of these irregularities, the modified prototype was given the pre-construction name SZD-8-2 "Jaskółka". The changes were mainly on lengthening the airframe, enlarging the tail and changing the ratio of the fin to rudder. The first flight of the pre-construction Sailplane was made on the 16th March 1952 and the whole program flight tests were completed by August 30th the same year. Much effort was made to cure the "Jaskółkas" flat spin. During flight tests in the revised prototype, factory test pilot Adam Dziurzynski performed 1000 tail spins. All changes made to the glider for analysis and measurement issues were preceded by theoretical calculations done by MSc. Wladyslaw Nowakowski. Flight measurements essentially influenced by changes in the spinning lead to correcting the problem. The spin had now become steeper, speed of descent was about 21 m/sec, the duration of one spin on average was 3 seconds and easily recoverable with only a slight delay.

The second prototype "Jaskółka, bearing the registration number SP-1223 flew on the 3rd December 1951 and had already made the necessary changes:

  • changed the aileron outline
  • eliminated the coupling with the ailerons
  • changed the entire couplings drives
  • removed the control cable temperature compensator
  • modified the fuselage shape in order to eliminate the malicious "flat spin"
  • changed the connection drives between the wing and fuselage
  • fitted a test closure mechanism to the canopy

The glider was now relatively stable and the pilots had raised no concerns regarding the controls and the flight forces of the "Jaskółka" and so preparation for production could commence.

SZD-8 bis

From the experience gained with each of the prototypes SP-1222 and SP-l223 and satisfaction with their trials, engineers Justin Sandauer, Adam Skarbilski and Thaddeus Kosti started work on the first production design. Following the implementation of the necessary changes and improvements and further new problems resolved, production of the SZD-8 bis "Jaskółka" began. The construction was completed in December 1952 and on December 24th, test pilot Adam Zientek flew the first production SZD-8 bis bearing registration marks SP-1305


Early production SZD-8 bis


A line up of 14 Jaskółkas

The new "Jaskółka" differed from the prototype in:

  • the shape of the fuselage was changed around the cockpit
  • modified the wing-fuselage transition
  • modified the fuselage nose
  • tail style amended by the aerodynamic design of the brakes (single blades instead of double)
  • re-designed all the flight controls
  • revised the design of the flaps operation
  • amended the construction of the canopy and cockpit
  • revised the design of the spar
  • installed a semi-retracting undercarriage

The glider was subjected to the full tests of the State and factory during the First Polish Gliding Championships in Leszno in 1953, by various experimental competition pilots: Ablamowicz, Bojanowski, Dziurzyński and Zientek.

The first series of 30 "Jaskółkas" did not cater for the demand of the domestic market and the growing popularity as well as foreign orders forced the plant to subsequently restart production.

The video below from YouTube shows how to rig a Jaskolka


SZD-8 bis E

The following SZD-8 bis E detail photo files are available for download and are relevant to most versions:

DZS
Also
from Retroplane

Following the experience gained, design engineers, looked back to check if they could improve the construction and after taking into account all comments they further developed a version called the SZD-8 bis E. This SZD-8 bis differs only slightly. The tailplane height was changed minimally and the back runner and drives for the fowler flaps were reinforced as well as the brakes and undercarriage aerodynamics along with the undercarriage itself. A series of 30 "Jaskółka" SZD-8 bis E were produced and in the spring of 1954, took part in the International Gliding Contest in Leszno.

SZD-8 bis W

Wing control connectors

The escalating gliding requirements had forced the designers to newer developments. Introduction to the rules for gliding competitions gave them a new problem - ballasting the gliders. The easiest way was to put tanks in the wing filled with water which would be emptied out in flight. Development of the new specification was under the direction of construction engineer Stanislawa Wielgus. The project used a production SZD-8 bis, SP-1529, which was fitted with tanks in the wings that would hold 95kG of water filled by a tube placed at the upper wing-fuselage transition.


Filling the water tanks

The newly formed glider was identified as SZD-8 bis W. Time for emptying tanks in flight was 2.5 minutes. The glider without water would get airborne after about 30 meters of run, but with water, it needed 100 meters. After evaluation of the tests results of the converted SZD bis-8 sailplanes types following installation of water tanks, a number of changes were introduced, including:

  • further strengthening the undercarriage
  • tightening the control cables
  • moving the location of the oxygen equipment to behind the seat so as to be more convenient
  • changing the size of the instrument panel
  • in flight adjustable pedals
  • the most striking reshaping of the front of the fuselage
  • removing the transition line in the forward canopy which smoothed the nose of the glider and improved aerodynamic performance

SZD-8-III and SZD-8 bis O and SZD-8 bis Z



Pictures from "Flight Magazine"

New instrument panel from SZD-8 bis O onward

The SZD-8 bis Z, had the new canopy with smooth transition between the fuselage and canopy. "Z" stood for "zawodnicza" meaning competition version.

A further increase in demand for "Jaskółkas" pushed for still more improvements. Thus, under the guidance of S.Wielgus, SZD built the versions III and SZD-8 bis O, with little difference from each other. The final SZD-8-III is based on the glider SZD-8 Bis E and SZD-8 bis Z. The structural changes were:

  • new undercarriage and rear skid construction
  • use of locally made bearings for all the drives in the present production.


SZD-8 bis H

The final SZD-8 bis H differs from SZD-8 bis E in that it used the fuselage shape of the SZD-8 bis Z and improved the shape of the instrument array. It had no water tanks for ballast. This version was made with maticulous care as it was intended for foreign audiences.


SZD-8 ter Z

The next version of the "Jaskółka" no longer differed significantly from the previous. The glider SP-1750, "Jaskółka" SZD-8 ter Z is a revised version of SZD-8 bis Z. It was developed by a team under the direction of Master Engineer Z. Brachackiego. The aerodynamic brakes were changed from wood to metal, instrument array was preconstructed, the water tanks system improved by using powered water discharge valves, a new sharper fuselage-wing transitionwas made using low cost glass fibre mouldings instead of the expensive plywood panelling to overcome costly labour.


SZD-8 ter ZO


SZD-8 ter ZO (SP-3675 )
detail photo files for download are available

by Viktor Drzeniek HERE
and
freom Retroplane webiste
HERE

In 1958, in parallel with SZD-8, had been the construction of an SZD-8 ZO ter, differing from the SZD-8 Z ter by a lack of water ballast. A total of 40 units were built, of which several flew with Polish aeroclubs.

Finally there was an unrealised versions of the "Jaskółka" called the "Jaskółka K" which was without flaps on the wing in order to reduce the cost of building the glider.

The difference between the first prototype SZD-8 compared with the last version, the SZD-8 ter ZO varies greatly not only with the external outline, but also with its performance, the general flight properties, trim level and way of painting, upholstery and the degree of comfort and luxury in the Cockpit.

The "Jaskółka SZD-8 ZO had very good control, high maneuverability and particularly good performance with speeds up to 130 km/h in combination with very small forces required on the joystick. Flaps reduced the speed easily in flight and also during the approach and landing. Closing the aerodynamic brakes required a relatively large force, especially at speeds over 80 km/h.

Construction notes for the SZD-8 ter ZO

The glider SZD-8 ter ZO "Jaskółka" is a universal single seat competitive glider on a cantileverd mid-wing, able to carry out flights in clouds.

Fuselage construction was oval in shape with a plywood skin and with glass fibre panels for the nose section forward of the canopy and for the wing fairings. The front of the fuselage has a wooden skid and a semi retractable wheel with a diameter of 300 mm for take-off and landing is installed near the center of gravity. On the rear of the fuselage is sprung metal runner. The brake is coupled with the air brakes. At the lower front and bottom of the fuselage below the seat are mounted tow hooks. At the rear of the fuselage was hidden a handle to help manoeuvere the glider on the ground.

The Cockpit Canopy is made from mineral glass with fixed and moving sections travelling along guides, emergency escape and fitted with a side ventilator. The seat had an adjustable backrest and control pedals could be adjusted in flight. On the left side of the cockpit is positioned the lever for the flaps, air brakes and on the right side of cockpit is the control lever for the retrectable wheel. The Tow Release handle is placed on the left side of the instrument panel. Cables in the fuselage link to the release mechanism. The pilots in-flight baggage storage behind the seat is not available as this area is used to accommodate the barograph as well as the battery box for the lighting. Beneath this shelf are mounted type KP-18 two liter bottles of oxygen, mounted on the main former. Large baggage carriers are available for the pilot inside the wing-fuselage fairing. All metal parts are electrically bonded. Equipment and instrument panel: speedometer, altimeter, variometer energy ± 5 m/sec, variometer ±30 m/sec, compass, bank indicator and rate of climb. The total pressure sensor is placed in the nose of the fuselage. Static Pressure is measured with probe placed on the side of the fuselage.

The Wing is a Trapezoidal from in two sections with a single spar and is fully covered with plywood. The Wing profile is NACA 23012A, 4° dihedral with 1° wash-out. Two part Slotted balanced flaps with built in differential and covered with canvas. Inboard of the wings are aerodynamically balanced fowler flaps. These can be locked in the positions corresponding to surface deflections of 0°, 9°, 17°, 25°.Metal aerodynamic brakes are mounted behind the rear box spar with a locking device capable of automatically keeping them closed to prevent unwanted deployment in flight. At the of wingtip there is a navigation light and to the rear of this tip is fitted a lightning brush. The wing-fuselage coupling is automatic when assembling the glider.

Control Surfaces are horizontal trapezoidal and have great affect. By the use of one pin the tail can be folded down and engaged. Connecting drives are done automatically. The stabilizer surfaces are covered with plywood panels and the aerodynamically balanced rudder with canvas. The vertical stabilizer is built as an integral part of the fuselage and covered with plywood. At the top of the rudder is placed a lightning brush installation. The rudder is of wooden construction, canvas covered and fitted to the fin stern post



SZD-14x "Jaskółka M "


Colour scheme of SP-1223

Other gliders were built based on the succesful "Jaskółka" design, the first being the glider SZD-14x "Jaskółka M ', called 'Motylkiem". It was the fifth experimental glider designed by the Experimental Gliding Department. The idea for the construction of a butterfly tailed glider had interested Engineer Kosti for a long time. In the hangar there was already an unusable prototype SZD-8-2 "Jaskółka" SP-1223 and so he used this opportunity. Construction development was to be carried out by engineer Wladyslaw Okarmus, with theoretical development by MSc. Tadeusz Kosti. The experiment was intended to:

  • examine techniques of control application
  • to scrutinise the effect on climbs and turn control performance compared with normal tails
  • try the suitability of the tail for application on jet-propelled gliders

Test flying started on the "Jaskółka M" in September 1951. with Adam Dziurzyński, the test pilot at Bielsko and it was during these gliding trials that he had an incident. At the time of exiting a tail spin he twisted the back of the fuselage, which was made from plywood panels. The pilot had no parachute and risked crashing his glider but managed to land it with a broken tail bent at an angle nearing 45°. The cause was a much larger force on the fuselage than that of a normal tail. For the risk he had taken guiding his glider to land, he received a reward from the SZD management. The flights made by the "Jaskólca M" found that the Butterfly Tail gave serious benefits. Tailplane drag was reduced by changing the number of tail surfaces from three to two which decreased by about 25% the amount of surface area affecting drag. Starting in tall grass is also much easier and less dangerous. The negative features include the need to cope with greater stress on the fuselage and a more complicated control linkage needed compared to a standard tail unit. The tail was a wooden structure and after landing could be freely moved by hand.


This series of images shows the damage sustained to theSZD 14 during flight tests
(see full report at Air Photo GORPOL)

The performance of the "Jaskólki M" was little different in principle from that of the "Jaskółka" series. At the Second Polish Gliding Championship with Stanislaw Wielgus, the 'Motylek" placied 18th in the overall scoring despite having to leave the competition The flying properties the of "Motylek" were vey similar to the "Jaskółka". It behaved quite well in acrobatics, allowing the pilot to perform effective side slips.


SZD-11 "Albatros"

The second structure, derived from the "Jaskółka was the SZD-11 "Albatros". The project to build an "Albatros" was started in 1951, but due to the poor living conditions of the time, a debate began on the broader policy of the relevance of building gliders, and whether Universal Sailplanes, which has a single fuselage and two pairs of wings for different conditions was more appropriate.

The result was a directive from the Experimental Gliding Department Directorate of Aviation to leave the designers free to develop the project. Engineers Justin Sandauer and Joseph Niespal started work and decided that it should fill a gap in the market for gliders being adapted to the thermal conditions prevailing in the Polish climate, that is, medium-sized thermal updraft of around 2 m/sec. The "Mucha ter" had not been a fully competitive glider, while the "Jaskółka was more fit for use in stronger thermal conditions. The gliders with the most desirable properties were to be found in the popular aeroclubs. Based on these considerations were to be the following technical conditions:

  • minimum sink rate around 0.7 m/sec at a speed of about 60 km/h
  • the maximum L.D ratio around 26.5
  • 18 m span
  • aspect ratio 18
  • wing loading of approximately 20 kg/m²
  • flying weight of 340kg.

The primary objective of the design was the adoption of the fuselage of the "Jaskółka which already was characterized with good aerodynamics and comfort. As a result the wing was increased from that of the "Jaskółka" and a new enlarged tail was made with an area of 2sq.m. The "Albatros" wing was of similar structure to the "Jaskółka" wing but in comparison with SZD-8 "Jaskolka it achieved approximately 30% lower wing loading.

The first flight of this new glider was made in October 1954 at Tadeusz Góra. The flight characteristics were so good, especially in slow thermaling turns, that in the next few builds of the glider it was planned to remove the flaps to reduce the production cost, however, non were ever built.


SZD-11-2 "Super Albatros". sporting the enlarged rudder

In the second Polish Gliding Championship T. Gora piloted this glider into third place in the overall scoring. It was renamed as the SZD-11-2 "Super Albatros". The new name was given because of the following modifications:

  • an further increase in rudder area by 1.5 m2 (shown above)
  • improving the aerodynamics of the wing flaps
  • water ballast tanks borrowed from "Jaskółka Z" were mounted on the wing tips.
  • the drag was reduced compared with the "Jaskółka"
  • the effect of the controls were reduced, especially that of the rudder and the response of the ailerons increased.
SZD-17 Jaskółka L
SZD-17 Cutaway

SZD-17 X "Jaskółka L'

The last derivative in the great "Jaskółka: family was the glider "Jaskółka L". The experience gained with the SZD-14 x, the forthcoming World Gliding Cup in France and the prevailing "fashion" of building gliders with a high load in the fact that the Experimental Gliding Department proceeded to draw up a dossier on the basis of a design for a "Jaskółka glider, with laminar wings, large water tanks and 'v' tailplane. The team under the direction of M. Sc. Tadeusz Kostii and MSc. John Dyrka developed the drawings and on the 9th March 1956, the first SZD-17 X "Jaskółka L', also known as "Laminarką", made its' first flight piloted by Adam Zientka. This "Jaskółka was designed primarily for export. The glider SP-1505 took part in the 1958 World Gliding Championship at Leszno and is shown immediately below. An interesting video of this event can be viewed here


SP-1506, now in the museum at Krakow

Other photos of SP-1506

Tailpiece to the 1958 World Gliding Championships from the Flight Magazine June 1958 :-

THE Leszno Airfield, Poland opening ceremony at Leszno on Sunday, June 15, was followed that afternoon by a superb display of gliding flight. Outstanding items in a high-quality programme included individual aerobatics in a Jaskolka L by J. Popiel; formation and follow-my-leader aerobatics in three Jastrzabs flown by S. Acker man, Z. Szubra and J. Lacki; and a four-glider aerotow by a Yak-12.

From the far side of the airfield an SM.l helicopter buzzed over, and your correspondent steeled himself for yet another selection of the customary helicopter gyrations. This was not for Leszno, however: down from the helicopter snaked a long rope, rapidly to be attached to a Jaskolka glider. With a purposeful lunge forward the unconventional aerotow began. That was not all. After towing the Jaskolka up to a reasonable height the helicopter slowed down and finally hovered, dangling the sailplane underneath like a fish on a line. The pilot of the Jaskolka, J. Adamek, extricated himself from this unenviable position simply by pulling the release-knob. And he went through a neatly polished routine before landing safely. Incredible


Records

With the "Jaskółka" many pilots made international records including one English, one Bulgarian and seventeen world records

1954 - Faster Triangle It is reported that Mr. Dan Smith, C.F. I. at Dunstable and one of the British sailplane pilots taking part in the Communist sponsored international meeting near Poznan, Poland, has. set up a new British speed record for a triangular course. Flying a Polish "Jaskółka" sailplane, he achieved 37.07 m. p.h. ; the previous British record was 29.21 m. p.h., by Philip Wills.

1956 - Warsaw radio announces that the woman glider pilot Majewska, flying a "Jaskółka" single-seat glider, beat the distance to a declared goal record, F.A. I. Class D, by covering a distance of 573 km (about 355.8 miles) on August 10. The existing record is held by Mme. M.Choisnet-Gohard in an Air 100 at 507.052 km (about 314.87 miles).

plus the following records :-
Polish Altitude (1957)
5820m

Triangle 100 km

80.5 km/h
D. Zachara,
Triangle 200 km
67 km/h
M.Czmiel-Paszycowa
Out and return
341,9 km
P. Majewska
Out and return
536 km
L. Misiek


The "Jaskółka" was exported to 14 countries.including England, Belgium, Denmark, Finland, East Germany, Romania, Switzerland, Sweden and the USSR.

In China,quantity production of the Polish gliders Bocian, Jaskółka and Mucha sailplanes began at Tchan-Tia-Kou Sailplane Works Shen Yang in 1955-56.

Chinese People's Liberation Army Air Force

Despite its' age the "Jaskółka" was a flying standard to be matched, but slowly its performance paled in the shadows of the newer "Foka" and "Zefir" and in January 1962 the "Flight Magazine" reported :-

"SZD (experimental glider establishment), Bielsko-Biala The spectacular debut of the revolutionary SZD-19-2 Zefir and SZD-24 Foka super-high-performance sailplanes at the 1960 World Gliding Championships, and the phenomenal show they put up during the contest days, were unmistakable pointers that the Polish glider industry had reached a new phase of skill in sailplane design. Few people, however, suspected that the appearance of these elegant machines would be swiftly followed by changes in glider production programmes and training syllabus of a magnitude unparalleled in the past. Gone from the 1961-65 production list are the famous names of Jaskolka, Bocian and Mucha, which have won Poland many world records and scores of "diamonds"; the new generation of the SZD sailplanes, comprising the Kormoran, Kobuz, Li?, Foka and Zefir, will take the place of the old."

The cost of buying a Jaskolka in the UK In 1959 was £1,025


Colour Schemes

The prototype "Jaskółka" was painted red with white registration marks and on the tailplane yellow band 15 cm wide similar to this colourized image
The production versions are painted cream, decorative lines and registration marks in black. On the rudder is a stylized portrait of a swallow.
The "Jaskółka" SZD-8 ter Z and ZO are painted cream with decorative light blue and navy blue lines and on the front of the fuselage is also a stylized swallow.

Production

135 "Jaskółkas" were produced in various versions.
SZD-8 and SZD-8-1 Prototypes
2
SZD-8 bis "Jaskółka bis" and "Jaskółka W
60
SZD-8 bis "Jaskółka Z"
28
SZD-8 bis "Jaskółka O"
5
SZD-8 ter "Jaskółka Z"
10
SZD-8 ter "Jaskółka ZO"
30


DATA
SZD·8
Jaskółka
(prototype)
SZD·8 bis
Jaskółka
SZD·8 ter Z
Jaskółka
SZD-14X
Jaskółka M
SZD-11-2
Super Albatros
SZD-17X
Jaskółka L
Wingspan (m)
16.0
16.0
16.0
16.0
18.0
16.0
Length (m)
6.74
7.42
7.42
6.48
7.6
6.8
Height (m)
1.28
1.41
1.41
1.3
1.41
1.26
Surface Area ()
13.6
13.6
13.6
13.6
17.7
13.6
Aspect Ratio
18.8
18.8
18.8
18.8
18.3
18.8
Empty Weight (kg)
275.5
252
270
288
268
340
Total Weight (kg)
300.5
337
355
*(450)
373
353
425
*(545)
Wing Loading kg/m²)
26.5
24.8
26.2
(33)
27.4
19.5
31.2
(40)
L/D Ratio
25.4
26.4
28.5
26.3
26
30.5
Best Glide Speed (km/h)
80
80
83
(92)
80
74
93
(109)
Minimum Sink (m/sec)
0.76
0.76
0.75
(0.85)
0.79
0.7
0.86
(0.85)
Economic Speed (km/h)
65
68
74
(84)
69
61
93
(104)
Minimum Speed (km/h)
50
55
55
59
52
65
Maximum peed (km/h)
250
250
250
250
230
250

Notes

- Data SZD-8 bis E are identical with the SZD-8 bis.
- Data SZD bis-8, in principle does not differ from SZD-8 bis, empty weight is 267.5 kg.
- Data SZD-8 bis Z, SZD-8 III bis, SZD-8 bis and SZD-8 ZO ter are identical to the SZD-8 ter Z.
- Data SZD-li "Albatros" is identyczno with the SZD 11-2 "Super Albatros", empty weight is 263.5 kg.

- Shown In brackets are the effects of the water ballast

For further reading, download this Documentation from the QFI Magazine from May 1995:


Aknowledgements:

Most of this page has been translated from a Polish document of unknown origin, possibly from the 1950's. Thanks to the Internet I have managed to convert into English, although there may be some errors in translation. If you want the original documents, then you can contact me. If you recognise the source, then please let me know for inclusion in the credits

Thanks also go to:

  • Retroplane for some of the photo file links
  • Viktor Drzeniek for detail photo files
  • http://www.piotrp.de/web/ for extra photos and infromation
  • Doug Garland for detail sketches