By me
Photos as credited

While the very mention of its name often invokes fond nostalgia and strong apprehension in equal measure, there’s no denying that the pudgy little UTVA 75 remains one of the most famous, significant – and perhaps maligned – aircraft ever produced by the Yugoslav aviation industry. One of a number of piston props conceived, designed and built solely in-country, it had left a lasting mark on the local aeronautical landscape, having over the years seen off generation after generation of young pilots, service in a bewildering number of roles in every nook and cranny of the land – and the occasional appearance in the odd accident column…

But for all its past ubiquity, the type has become somewhat of a rare sight today, with most of the airworthy civilian examples nowadays confined to flying clubs in Serbia, Bosnia and Herzegovina and Macedonia. Outside military dumps, finding one elsewhere requires a bit of luck – so much so that even the locals (many of which had flown them extensively in the 80s and 90s) raise an eyebrow when one happens to rumble by.

So imagine my surprise when – having so far only five examples under my camera’s belt – I became aware of a beautifully curious four-seat example parked just 70 km away at Novo Mesto Airfield (LJNM) in southeastern Slovenia. Having only seen such a “quad” in one 80s photo, I was through the roof even before I found out it was the only such example in existence – a fact that (as if any further persuasion was necessary!) had seen me grab my car keys and set off across the border to see what’s what… 🙂

Wings of the nation

But, before we cover this prime example of Achtung, Skyhawk! material, a bit of history to introduce this compact little type to readers who may have never seen one in the metal 🙂 . Flying for the first time on 19 May 1976, the UTVA 75 – known under the factory designation U-75 – was designed to be a simple, straightforward basic trainer* that could be efficiently used both in civilian and military roles. Even though the Yugoslav aviation industry had always put much stock in this segment, its offering of such aircraft was next to abysmal at the time, with the late 40s Ikarus Aero 2 and mid-50s Aero 3 being the only machines widely available for the role. Despite having given wings to post-WW2 Yugoslavia, they were both very much outdated designs, sporting wood & fabric structures, tandem cockpits, narrow-track tailwheel landing gear, basic instrument fits – and flight characteristics that often did not inspire much confidence in the student.

* interestingly, the project had originally envisaged a whole family of aircraft stemming from one basic design, including a four-cylinder two-seat utility machine dubbed the M-10, and – most interesting for us 🙂 – a six-cylinder touring four-seater called the M-11. Eventually though, financial difficulties (which had also seen the temporary inclusion of Polish aircraft manufacturers in the design between 1973 and 1975) had left the M-10 as the sole survivor, paving the way for its development into the U-75.

Designed around more modern principles, the U-75 had a lot going for it in the trainer role: it was robust, simple, easy to maintain and had just enough power to pull a few basic aerobatic maneuvers – but not enough to allow the student to correct every mistake with liberal application of the throttle. Additionally, it had a side-by-side seat configuration, a large instrument panel suitable for more advanced avionics (including blind-flying gear) – and, most importantly, was built entirely of metal (prolonging its service life in the aerobatic role) and used a wide-track tricycle gear with low pressure tires that made it safe and relaxing to operate even on poor airstrips. Other features had included a tailhook for towing gliders or banners, while the military could be content with a removable pylon under each wing, which could accommodate jettisonable fuel tanks, cargo drop containers (carrying 100 kg (220 lbs) each), light bombs of 50 kg (110 lbs) – and even unguided 12-tube 57 mm rocket packs and twin 7.62 mm machine gun pods.

Designed from Day 1 to meet the requirements of the FAA’s FAR Part 23 regulations concerning UTILITY category aircraft, the U-75 can also boast a +6/-3 load limit – and was found in actual operations to be rather crash-worthy, since its wing and wing box were strengthened to cope with the rigors of “external cargo” 🙂 . Despite hailing from “the East”, under the hood the U-75 sports quite a bit of Western hardware, including a four-cylinder, fuel-injected 180 HP Lycoming IO-360-B1F whirling a Hartzell HC-C2YK-1 BF/F 7666A two-blade constant speed propeller.

With a MTOM of 960 kg, this package is responsible for a maximum level-flight speed of 215 km/h (116 kts), a maximum ceiling of 4,000 m (13,100 ft) and – combined with a wing profile suitable for low speed maneuvering – take-off and landing runs of only 125 m (410 ft) and 100 m (328 ft) respectively. The efficiency of the constant speed prop also means that the U-75 can be relatively frugal in a stable cruise, registering a range of 800 km (432 NM) on 150 liters (40 USG) of internal fuel. When fitted with two 100 liter (26 USG) drop tanks however, the U-75 was supposed to be able to reach an impressive 2,000 km (1,080 NM) – though this was a theoretical calculation only, since the aircraft had never been test flown to this extreme (the tanks themselves were never used in actual training operations).

Equipment-wise, the standard 75 was provided with the usual VFR instrument setup, including everything from the Basic 6 with the addition of an ADF receiver (all of which were powered from a simple and unremarkable 14 V electrical system). The armed versions used by the Air Force would also be provided with a simple optical aiming sight on the left side, while all models could be additionally equipped for night VFR operations. Interestingly, the instruments used were an unusual East-West mix, with the artificial horizon, turn and bank indicator, ADF, manifold pressure/fuel flow gauge and the tachometer all sourced from the US, with the rest of the instrumentation either indigenous or acquired from other European states that had used the metric system.

In service, the U-75 was always much blighted by a popular reputation for violent spinning (sometimes fatally), which bred some distrust in the design. However, while it could indeed be thrown into a serious spin if the pilot was determined enough, most of the type’s spinning accidents were due to it being flown contrary to manufacturer recommendation. Even before it had entered series production in 1978, official flight tests had concluded that the U-75 had no abnormal tendencies to spin if flown by the book – a fact also testified to by numerous operators who had never had any such problems, despite regularly putting their machines through various aerobatic and near-aerobatic routines**.

** one of the main causes of the 75’s willingness to spin if pushed was the location of the (rather heavy) battery. Initially, it was to be located immediately behind the cabin; however, it was calculated that this would shift the CG too far forward, making the aircraft too stable and docile for its intended training role. To combat this issue, the battery was relocated to the extreme of the aircraft – the tail cone – thus moving the CG backwards and making the aircraft less stable and more maneuverable (but still well within accepted limits).

Interestingly, the U-75’s public perception parallels another love-hate civil aircraft, the sporty Mitsubishi MU-2 twin turboprop. From a purely statistical viewpoint one of the unsafest designs around, the MU-2 had gained its unenviable reputation mostly due its users’ inexperience with turboprop hot ships, coupled with poor and insufficient training (especially in the US). Once these issues are surmounted, owners swear on them to no end, with numerous examples having clocked up accident-free flight time that runs well beyond 15,000 hours.

By the time production had ended in 1985, the U-75 had become one of the most produced indigenous Yugoslav designs, with 138 examples made (including the prototypes) – though not coming close to the country’s other notable aviation product, the Soko G-2 Galeb jet trainer, of which 248 were made 🙂 . Being a wee little piston prop had also meant that the U-75 was very usable outside military and training circles, with a good number eventually making it into various civilian flying clubs and to various private owners following Yugoslavia’s collapse. Despite 20 years of attrition still a common sight in Serbia, Bosnia, Macedonia and (very occasionally) Slovenia, the type is – as noted previously – sadly absent from Croatian skies, with the only examples operated after 1991 having flown with the Croatian Air Force. Used initially for limited combat operations during the war, the type would continue to soldier on in the basic training role until 2007, when it was withdrawn and replaced by the Zlin Z-242L…

2+2=78

The story of the four-seat U-75 would, however, begin not long after the first of the standard machines had started rolling off the production line. For all the variety produced by the Yugoslav aviation industry, no manufacturer of the time had a modern touring machine on offer, with most of their light aircraft output catering to utility and training needs – leaving various imported Cessnas and Pipers to fill the gap. Having been the newest indigenous design available when the industry had finally turned more of its attention to this segment – not to mention its connection to the stillborn M-11 – the U-75 had seemed to be a good place to start, its basic design offering a low-risk opportunity to quickly (and cheaply) produce a suitable aircraft for the role. From the very outset, the design goal had been to create something of a home-grown PA-28 that could be used both for personal flying and IFR training – as well as potentially exported abroad***.

*** even though the international public’s unfavorable perception of Yugoslavia’s engineering capability (in part well earned) might have put off people from buying its hardware, several of its aircraft were in fact highly regarded in Western aeronautical circles. Most notably, in a USAF fly-off competition in the 80s, the Soko G-4 Super Galeb jet trainer was judged superior in a number of respects to the visually similar BAe Hawk – however, the implications of a major Western power buying military hardware from a Socialist state (never mind its alliance) had sealed the aircraft’s international sales prospects well before it had even been flown.

However, since the whole project had had “cheap and cheerful” as its premise, the changes necessary to turn the standard 75 into a four-seater had to be kept minimal (in part to also reduce disruption on the production line). To this end, the design team had taken the type’s fourth prototype – registered YU-DRJ and sporting serial 53004 – and reconfigured its capacious cargo bay to give a bit more room, slotted in two additional seats – and then fitted a longer, extensively-glazed two-piece canopy to make entry into the back easier.

Dubbed the U-78, the new aircraft had in other respects remained identical to the stock 75**** (retaining even the towing hook under the tail). Even though it had also retained the original’s spartan mil-spec cockpit, production models were envisaged to sport a comprehensive IFR suite, sourced in full from Bendix-King and including the:

• KI 525A HSI (slaved to a remote gyrocompass and with full ILS capability) + ADI
• KI 229 RMI
• KNS 81 RNAV system (a fascinating piece of kit used for early area navigation, covered in more detail here)
• KN 62A DME
• KT 79 transponder
• and the system’s associated navigation and communication radios

**** there were indications in some sources that flush-headed rivets were used in lieu of the dome rivets of the standard model; available photo evidence however shows dome rivets on the fuselage, though it is not possible to discern their type on the wing. Informed opinion from a UTVA engineer is that it is highly unlikely (on a cost/benefit basis alone) that flush rivets were used anywhere on the aircraft.

However, back in the actual world, many of the finer details of both the design and DRJ’s service life remain a mystery; according to people in the know, the production documentation for the U-78 had always been scant at best, and what little was widely known was further lost during Yugoslavia’s violent dissolution in the early 90s. Furthermore, the aircraft had never been formally tested by the Vazduhoplovni opitni centar, or VOC – the state flight test center which was required to sign off each indigenous design – so no accurate or official performance numbers exists. Pretty much not even the people who had worked on the basic U-75 at the time have a complete and definitive picture of its capabilities…

What is known for certain is that DRJ – as the U-78 – had flown for the first time on 23 March 1979. Following standard factory testing, it would be transferred to the VOC at Batajnica Airbase (LYBT) just outside Belgrade, where it would continue to fly informally until 14 August 1981, when it had suffered an unspecified accident and was written off.

The loss of the only prototype – and the continued desire to press ahead with the project – had meant that the UTVA works would eventually need to produce a replacement. Interestingly, this would occur only in 1986, a year after production of the standard 75 had come to an end. This had meant that the new aircraft would not be manufactured outright in the classical sense, but rather assembled from the ground up using replacement parts (manufactured in advance to support the fleet in the future) and DRJ’s vertical stabilizer (which had survived the accident). Given serial 53263 – denoting it as the first of the post-production modifications – this new aircraft would officially be designated the U-75A-41 (though always shortened to just U-75A), and would initially carry the reg YU-XAC. Despite the different name though, XAC would not differ from DRJ (apart from dome rivets definitely being used throughout 🙂 ).

Flying for the first time on 14 May 1986, XAC would also initially pass to the VOC – again informally – before ending up with UTVA’s own flying club (AK UTVA Pančevo) as YU-BRJ. Sadly though, it would be completely destroyed on 24 March 1999 when the factory and its facilities were severely damaged in a NATO air strike.

I’m leaving on a container ship…

Even though XAC would – as proof of the design – go on to fly for a good number of years, forewarning of Yugoslavia’s 1991 implosion had quickly dashed many hopes of continuing development beyond the prototype stage. However, just before the country’s whole aviation industry would grind to a halt, the UTVA works had managed to cobble together one final aircraft, the lucky No. 3 that would lure me to Slovenia 🙂 .

Like XAC, this new machine could only come about in an unusual manner. Despite not having produced any new aircraft since 1985, the factory was still busy repairing, overhauling and scrapping in-service 75s – activities that would continue right up until the start of hostilities. At one point in the very late 80s, the company had come into possession of YU-DJO – a stock 75 manufactured in 1983 with the serial 53230 – which had been written off following an accident. Seeing their last chance at keeping at least something of the four-seater dream alive, the factory had decided to take what remained of the aircraft and rebuild it into an XAC-like model using any available spares and parts of other demobbed 75s.

What happens next, however, requires a short digression. The consensus among online sources and forums dedicated to Yugoslav aviation is that the aircraft had never actually been completed prior to the war, and that only an empty shell had been produced. Much doubt is also cast on the extent to which it would have conformed to the U-78/75A standard, especially since it was a rebuild of an existing 75 (using its basic fuselage), rather than a bespoke four-seat model.

These sources also state that the aircraft had remained at the factory until 2003, when it was sold – along with a regular 75 – to a buyer in the US. However, the buyer was said to have been unable to register the four-seater due to issues with its paperwork, with specific reasons given including missing/discarded documents, the aircraft being a composite of several different serial numbers and “unassigned parts” – as well as available documentation pertaining only to the bits belonging to DJO. Having thus sat around for a while, it was said to have returned to Serbia in 2008, to be restored, re-certified and sold on to a buyer in Slovenia shortly afterwards.

But, having had the great opportunity to personally interview the buyer in question, the story I was made aware of was quite different. It transpires that the aircraft had actually been fully completed and outfitted by spring of 1991 – and that its paperwork was, in fact, clean and in good order. Possibly intended for export right from the outset*****, the machine would soon be dismantled, crated up and – in the company of the aforementioned two-seater – shipped by sea to Mr. John Wallace of Oshkosh, Wisconsin, who had recently become the official distributor for UTVA aircraft in the US.

***** whether this export was just a fluke or planned from day one is not known with certainty. Given the ad-hoc nature of the build – with Yugoslavia already disintegrating – the project documentation was not diligently kept, so even UTVA employees are in the dark on this issue.

Interestingly, Mr. Wallace had specifically requested both versions of the aircraft, since he was interested in marketing both its military and civilian potential (that is, having a single design fulfill the training, light attack and touring roles). However, to be able to actively offer them on the market, Mr. Wallace had first needed to make some changes to comply with FAA regulations, most notably swapping the existing Yugoslav instruments and avionics for a US-spec cockpit suite sporting imperial measurements (in another point of contention, there is some doubt that US instruments had already been fitted in Yugoslavia – though this is believed to be incorrect).

But, by the time the changes had been made and the aircraft were ready for re-assembly, open hostilities in now ex-Yugoslavia had already started, leading to the introduction of a wide-ranging UN embargo against all of its former states. For Mr. Wallace this had meant that he could no longer import any new aircraft from Serbia, making both of his current examples – worthless.

Faced now with a whole new set of financial problems, he had immediately decided to sell the engines of both aircraft in order to try and recoup at least some of the funds invested in setting up the dealership and shipping the machines across the Pond. This had made the already unwanted machines even more useless, with both examples eventually consigned to languish around in Mr. Wallace’s garage, still packed up in their original shipping crates. Having absolutely no use for two engine-less jigsaw puzzles whose market value had been steadily decreasing, he had in 2007 decided to put the aircraft up for sale, going so far as listing them on – eBay 🙂 .

As it is often stated online, “if it looks stupid and it works, it’s not stupid” – which fully applied here, since the aircraft were quickly spotted on that very site by Mr. Leon Pogelšek of Ljubljana, Slovenia. Having recently completed his PPL, he had expressed a desire for his first aircraft to be indigenous, with the four-seater seeming like the perfect ticket for the job. However, since both aircraft were being sold as a single item, there was no other option but to buy the lot and possibly use the two-seater for spares.

With the sale finalized, the aircraft – complete with all papers and US instruments, as provided by Mr. Wallace – were once again loaded up into a container and shipped to Slovenia’s main port in the city of Koper. However, once they had arrived, they would immediately be launched into a world of legal issues, which even today – nine years on – conspire to keep the four-seater grounded. Despite the U-75 having been as common as trees in ex-Yugoslavia, no certified mechanics or service centers had remained in Slovenia by 2007, making the aircraft impossible to assemble and fly within the country’s existing regulatory framework (being a one-of uncertified example didn’t help the four-seater either).

Pretty soon though, a workable solution was found, whereby the assembly and overhaul of the quad would be contracted out to a company based at Lisičji jarak Airfield (LYBJ) in Serbia – and headed by a former UTVA executive and engineer – with the two-seater used as payment for the work done (being a low-timer with prime potential for resale)******.

****** unfortunately, the identity of this aircraft is virtually impossible to determine today, since its documentation had been handed over during overhaul. However, it is known that it was one of reportedly six examples sent to Sudan around 2008/2009, where they had resurfaced under the designation SAFAT 03. Interestingly, that designation had initially been used for an upgraded, Sudan-built version of the U-75, which had failed to gain any meaningful orders and progress beyond the prototype stage…

In the event however, the work would drag on for four years – having even been handed over to a third party at one point – during which only the wings would be attached and a new engine and propeller from another U-75 fitted (both of which with only eight hours on the clock). Dissatisfied with the pace of the work so far, Mr. Pogelšek would in early 2013 ship the aircraft over to an official UTVA service center in Sremska Mitrovica – a road trip of 80 km that had, once again, seen the aircraft disassembled into its original state.

Here, the aircraft would be fully completed, outfitted with the type’s original instrumentation and test flown, making it finally suitable for delivery and operation. Wary of the legal requirements that had prevented it from being assembled in Slovenia, Mr. Pogelšek had originally wanted to register it in Serbia – but was informed by the Slovenian CAA that it was also possible to have it on the Slovenian register. Being a unique, uncertified example, it was initially allocated to the country’s experimental register, becoming S5-MZT the same year (M – experimental/homebuilt). However, it was soon decided that – given its commonality to the stock U-75 – the aircraft could even be added to the standard register (prefixed with D like in all former Yugoslav states), becoming S5-DZT in the process. Under this registration, it would be flown to Slovenia sometime in June 2013 (the exact date eluding Mr. Pogelšek’s recollection), making this the longest time it had been airborne in its entire life – for a grand total of just 7 hours and 13 minutes accumulated by the airframe.

The future is now

Unfortunately, soon after its arrival at Novo Mesto, the Slovenian CAA had withdrawn its approval for registration, effectively grounding the aircraft then and there (the exact reasons for this change of heart appear to fall into a domain I wish to steer clear of 🙂 ). Given that the issue was still not resolved at the time of writing, the aircraft had remained immobile for the next three years, though Mr. Pogelšek has made overtones to eventually register it in Hungary and potentially return it to airworthy state. Being employed in the art world, Mr. Podelšek plans on eventually turning the aircraft into a “mobile canvas” (more precisely, an “aero art” flying installation), and repainting it with stylized images of themes from Yugoslavia’s industry – thus paying homage to both the cultural and technical aspects for former Yugoslavia.

In the mean time, it remains the perfect “poster aircraft” for Achtung, Skyhawk! – and provides an almost unparalleled glimpse into a bit of left-field aeronautical thinking that I hope my readers will enjoy! 🙂

Customarily, I would once again like to extend my sincerest thanks for their time and assistance to:

• Mr. Leon Pogelšek, the current owner of S5-DZT
• Messrs Matej Jevšček and Štefan Može of AK Novo Mesto
• Mr. Mario Hrelja, who was one of the people responsible for DZT’s thorough refit
• and Mr. Dragan Kolundžić, engineer at UTVA and author of several publications on its aircraft, without whose patience and education on the U-75 this article would not have been nearly as informative!

Sources:

• Istorija vazduhoplovstva Pančeva: UTVA 75 (The History of Aviation in Pančevo: UTVA 75) by Dragoslav Dimić & Dragan Kolundžić
• UTVA-75 factory catalogue from the mid-80s
• Safat Aviation Complex – SAFAT 03 product page
• My City Military Forum – U-75 discussion (in Serbian)
• Paluba.info – U-75 discussion (in Serbian)