By Boran Pivčić
All photos author
The I-3 is just one of those birds that so liven up a day at the airfield. An imposing Russian radial aerobatic monoplane, usually in a catchy scheme, is not something you casually glance over – especially when it fires up that big tractor under the hood amidst clouds of white smoke and the stench of engine oil. 9A-DOG is no different, though there is a bit more to it than it seems.
1. The I-3 – a bit of history:
Though outwardly very similar to the Sukhoi Su-29 – almost identical at a glance – the I-3 is a different machine altogether. Known in Russia as the Technoavia SP-91 (the I-3, or sometimes E-3, being the export designation), it was designed by Sergey Estoyan, the same man who did the Su-26/29/31 aerobatic series, after he left Sukhoi to co-found Technoavia. First flown in 1993, the I-3 was intended to be a cheaper, somewhat softer version of the Su-29, but one still capable of successfully competing in Unlimited Class aerobatic competitions. In the event, the aircraft didn’t prove to be much of a sales success and only about 20-ish were ever made (23 springs to mind, but I can’t verify that), of which 10-12 are estimated to survive today.
Like other Russian aerobatic aircraft, the I-3 uses the well proven formula of a strong, survivable taildragger airframe with tandem seats under a one-piece canopy – though interestingly, the I-3 can also be converted to a single-seat configuration, something unique in the aerobatic world. And it even has a small baggage compartment! The power comes from the extremely reliable and much-loved Vedneyev M-14P 9 cyl radial, producing 360 HP in this instance (though the westernised I-3M had the option of a more powerful 400 HP model), usually driving a three-blade constant speed prop.
Performance-wise, you can hit the usual +11/-9 G with two occupants, and I think the pilot of 9A-DOG told me the ultimate limit load is a juicy +/-18 G (but still not as impressive as the Su-31’s insane +/-23 G). Roll rate is not disappointing either, to say the least, at 345 deg/sec – almost a full roll in one second. Fuel consumption – we’ll skip that :). Oil consumption… well, despite the M-14 not being oil-thirsty, the pilot of 9A-DOG – who used to own a Yak-52 with the same engine – told me once the engine uses a liter per hour in aerobatic flight… so judge for yourselves :).
2. 9A-DOG – an overview:
9A-DOG – continuing the animal theme set by the aformentioned Yak-52, 9A-BUG – is an early model I-3, built in 1993, the type’s first production year. It had previously flown in the US where it suffered an accident and was rebuilt before being sold to Croatia in 2006. It is permanently based at Lučko and is a frequent visitor to many local airshows (being the only fully aerobatic – not to mention Unlimited Category – aircraft in the country).
Inside, the seating is typical an aircraft of this type – passenger up front, pilot in the back, to keep the center of gravity well back. This makes the aircraft unstable around all three axes – but since stability is inversely proportional to maneuverability, that’s the point. Interestingly, the panel is quite spartan even for an aerobatic aircraft, as it’s fitted with an innovative MFD screen that shows all flight-relevant data (the panel received an upgrade since the last time I saw in in 2006., but didn’t check out what – yet).
All in all, the I-3’s rarity meant I had to include it here at some point :). More pictures may be forthcoming as soon as I take them, as the airshow season is heating up along with the weather – and combined with my new 100-400 mm lens, you may get to see some actiony shots as well…
Specs (flugzeuginfo.net): http://www.flugzeuginfo.net/acdata_php/acdata_technoavia_sp91_en.php
I-3M specs (YAK North America): http://www.yaknorthamerica.com/i3mspecs.htm