Flight test: Sukhoi Su-29
- Credit: Keith Wilson
Coming from a line of aerobatic aircraft designed to challenge the West, this aggressive looking Russian is more ballet dancer than bear | Words: Bob Davy - Photos: Keith Wilson
The first aircraft in this line, the Sukhoi Su-26 first flew in 1984 and was designed to be a world-beating, make that a West-beating aerobatic aircraft during the Cold War.
As such, Sukhoi had the might of the Soviet Government behind it?this aeroplane certainly wasn’t built down to a price. Take for instance the undercarriage: it’s made of solid titanium, and each unit was said to cost in excess of $10,000 back in the 1980s.
Hmm, titanium?it’s interesting stuff. It might be incredibly light and strong but, like those incredibly flexible glasses that you can tie a knot in then untie without damage, titanium gear legs can keep on bending and bending under load, until... Let’s come back to that later.
The biggest problem with the Sukhoi Su-26 is of course that your first flight in it is your first solo, and an Su-26 is nothing like the Yak-55M that came before it. I have flown both aircraft and would class the Yak-55 as one of the easiest aerobatic taildraggers to fly whereas the Sukhoi is in the top three hardest, right alongside the Sbach XA-42 (e.g. almost everyone one who flies one has ground-looped it.)
When I did my check flight in the Su-26 I finished off with some ‘aeros’ over the airfield, where instructor Paul Bonhomme was watching and waiting. The last manoeuvre was a loop with a surprise avalanche at the top?a positive flick, but inverted.
It was perfectly lined up, with exit in line with entry. When I landed Paul walked over and said “well, you seem to be at home in the Sukhoi. I particularly liked the avalanche at the end.” My reply was “thanks, it would have been great if I’d actually meant to do it.”
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I hadn’t been accurate enough on centralising the rudder over the top of the loop and the combination of yaw, G and reducing airspeed gave me a perfect flick. I had immediately centralised the controls and she exited.
The alignment was pure chance. (For your entertainment rather than education, I would add that the exclamation in the cockpit was a very loud “oh s***!”)
Sukhoi set about fixing the attrition rate/training needs of various civilian and military customers across the world. The answer: a two-seat derivative, first flying seven years after the Su-26. To keep the weight down the Su-29 made extensive use of composites?more than fifty per cent of the structure?and the result is that the aircraft only weighed fifty kilos more.
Think about that for a moment: the addition of a dual-control cockpit with a net difference equivalent to the weight of a 1990s Russian supermodel. It was an astonishing achievement at the time.
As an example, the Yak-52 TD is 240kg heavier than the Yak-50 (I set aside normal tri-gear Yak-52 because of the extra weight of the nosewheel). Today the weight difference between two-seat and single-seat Extras is slightly more than that between the Su-29 and -26 despite the much lower penalty in using modern featherlight instruments and avionics.
Had the Russians had today’s technology thirty years ago, the 29 would probably be about the same weight as the 26 or perhaps even lighter.
Make no mistake, while their time at the top of the competition tree might have come and gone since the men’s last World Championships win in 2005 and Svetlana Kapanina’s ladies’ World title win in 2011 (google her videos?a most incredible and artistic pilot) Sukhois are still seriously out there in the aerobatic world.
It’s interesting to meet with up-and-coming aerobatic competition pilots flying western types and see their reaction when mentioning the Su-26 and -29. Reverence and respect? Certainly. Downright fear? More than occasionally. White Waltham’s own competition aerobatics instructor/Extra 330/Cap 232/Pitts-owner Mike Collett is new to the type and says that he’s aware of the 29 being likely to bite him if he ‘pokes it too hard’.
Many Sukhois have also been retrofitted with more powerful engines and better propellers: out with the 360hp/240cm, two-blade prop combination as seen on the Yaks of the period, replacing it with an engine delivering up to 450hp and a 250-260cm, three-blade western propeller.
The one I am about to fly has around 430hp with a 260cm MT composite prop. As Paul Bonhomme once said: “throttle open equals ugly aeroplane, throttle closed equals easy aeroplane.” The torque effect and gyroscopic forces on this aircraft can be tremendous, particularly at low speed.
The rudder and full-span ailerons (with two spades per side!) are immensely powerful and the stick ultra-sensitive in pitch?so much so that pilots new to Sukhois almost always pull up to twice the G than they planned to, until they settle down. And some pilots never do.
Just looking at the Su-29 at White Waltham my blood pressure is already climbing. I’m going front-seat first?the student’s seat?and there’s not much to do other than climb up on to the wing, being careful to stay on the grip strips, pull the parachute out of its bucket in the seat back, strap it on and strap in.
This is a lengthy affair due to the double waist straps with ratchets, a negative G strap, and two shoulder straps?seven in all, and it takes time to adjust everything when the previous occupant isn’t the same size as you.
It’s also important to tuck away the strap ends so they don’t hit you in the face during negative G stuff, and make sure nothing is dangling down the sides of the seat and interfering with the rear cockpit’s rudder pedals which sit alongside. This is especially important when flying solo from the rear.
Then there is front seat rudder adjustment to take care of... it’s good to have a patient instructor to help, in my case Simon ‘Abbo’ Abbot, who can be seen in the accompanying air-to-airs with his daughter, Julie in the front. Julie is also a pilot and she shares her father’s aerobatic courage, including completing ‘the Abbo family initiation’, an outside loop.
Hands up here: no, I have not completed the Abbo family initiation because I hate anything more than minus one G.
Once strapped in, the seating position makes me feel like I’m in a hospital delivery room, about to have a baby. The steep rake in the seat combined with the aircraft attitude on the ground gives the impression of laying on your back with legs wide apart, the rudder pedals like foot stirrups.
The cockpit is dominated by that enormous stick, a two-hand job for the more violent manoeuvres. A big, chunky throttle falls to hand down the left side of my thigh with a prop lever next to it, both lower and farther back than ideal.
The instrument panel has a big red lever on the left which is pulled in an emergency (to call the midwife?
No, to eject the canopy) and there are other rudimentary flight instruments, from left to right: a western altimeter, a metric ASI above a clock, an RPM gauge indicating percentage of maximum, as you find in a jet, and a small annunciator panel above a CHT gauge.
On the centre console between my legs are two G meters, one mounted upside down for the negative stuff. It’s all very basic?the radio, intercom and engine starting is organised from the back.
Good aircraft command high prices. Expect to pay around $150,000 for an Su-29, maybe more for a really nice one with low hours. Because of the success of the Su-29, Sukhoi went on to design a ‘super’ 26 with the same composite technology.
It was called the Su-31 and was much lighter than the Su-26 but, for the top aerobatic pilots, not as nice to fly because the lower fuselage mass shifted the C of G forwards, and the ailerons were not as good. In the ’90s there was a market for Su-31 pilots looking for pairs of Su-26 ailerons to retrofit! Weird but true.
I wait for Abbo to strap in and then it’s time to lower the side-hinged canopy over and across from right to left?it’s a long reach and quite heavy?and then push the locking lever forward fully home on its left forward corner. Engine starting takes place from the rear seat, so I just sit there and soak up the environment, appreciating that this aircraft was designed with only one purpose in mind. But is it?
I can appreciate that the view ahead is non-existent on the ground, so maybe this aeroplane would make not just an aerobatic trainer but a good step towards getting into a taildragger warbird. I’ll find out shortly. What about using it as a transport? It’s a fair question: the Su-29 has two 100 litre wing tanks as well as a 65 litre aerobatic tank in the fuselage, giving a maximum range with reserves of over 500nm?but would you want actually to use it for touring?
It would be like volunteering for an extended stay in the delivery room. (A student of mine did buy an Su-29 as a tourer twenty years ago, against my advice. He never toured in it?in fact never even managed to solo it?and would have sold it a couple of years later had his friend not written it off first in a forced landing.)
A big blast of smoke accompanied by a waggle of the wings reacting to the swing of the prop announces the engine start of the mighty M14PF. Abbo closes the iris ‘cooling gills’ with the lever on his right cockpit wall and we wait for a further five minutes for the CHT to reach 120?C and oil temp 40?C before we are allowed to open up to taxi.
Abbo releases the tailwheel lock: it’s at the right base of his seat, a little catch like the bolt action on a rifle, and spring-loaded to ‘lock’. Then it’s down to me. I open the throttle just a little but the response is immediate and we surge forward on the grass.
I’m used to high power-to-weight ratios but this is something else. Steering is light and powerful and I’m finding it easy to weave to the holding point. Not a difficult aircraft to taxi, I’d say?apart from the view forward, or lack of it.
Line up into wind, stick hard back, feet on the brakes (no parking brake) Abbo operates the cowl iris (there’s no control in the front) and I open the throttle to seventy per cent to check the mags, alternate air and exercise the prop, then close it to check the idle. It’s all straightforward stuff and we’re ready to go. I line up on Runway 25 right and Abbo signals me to launch.
I run straight a few feet then ask him to lock the tailwheel, then with stick back, open up the throttle, adding left rudder progressively, calling “one thousand, two thousand, three thousand.” The roar of this M14PF is angry and visceral and the acceleration immense as we catapult into the sky with the ASI arcing past 120kmh and the VSI pegging 3,500fpm, I am told (I’m concentrating instead on keeping the wings from rocking? those ailerons are so twitchy at low speed?and checking that the sky forward and above me is clear).
I’m also getting the sensitive pitch thing but I’m used to that with other types like the Sbach, so it’s not as difficult as it might be.
I pull the power back to ‘eight bananas’ of manifold pressure?Abbo tells me when I have hit that on his gauge in the back?and I set 82% RPM with the prop. In the blink of an eye we are at circuit height and now my left hand is coming way, way back on the throttle to keep things sensible, i.e. below 200kmh.
Flying level at this speed I can see ahead over the nose but as I reduce to 150kmh for base the nose goes ever higher?the Sukhoi has a symmetrical aerofoil and so relies on angle of attack to produce lift. Turning in on final it’s worse, so I push a bootfull of right rudder against the crosswind from the left and fly cross-controlled with left wing down until fifty feet, and then kick everything straight.
Now I can’t see out front but I’d previously lined up slightly right of the centre line stripes and wait for them to come into view as speed comes back to 130kmh. The horizon is now at the top of the ‘shark gills’ either side of the nose and I close the throttle to lower the aircraft onto the runway. I manage to miss ‘the bump’ (all Waltham pilots know where this is?the intersection of R21 and 25) and we settle on three points. Everything okay.
I do the same thing on the next circuit, but hit the bump on touchdown and all hell breaks loose. I remember Bonhomme’s advice from twenty-plus years ago and count “one thousand, two thousand, three thousand” as I pull the stick back at precisely that rate after we touch down again: any slower and you risk getting into PIO (pilot-induced oscillation) in pitch; faster and you risk propelling yourself into the air only to stall too far away from the ground.
Then the ‘titanium toffee’ gear legs will come in to play. Unlike steel or composite they will keep deflecting until the prop hits the ground, then spring back to the original position as if nothing happened.
I know of four Sukhois at Waltham alone where this has happened. We do one more and the landing is somewhere between the previous two. The Boss is happy and it’s time to swap seats.
In the command seat
So now I’m strapped into the back. The panel is slightly different, with a manifold gauge in the middle, between my legs on the centre console is the electrical switchery and beneath that the radios. (These aircraft were hand-built and the cockpit fit of each one is slightly different.)
The engine is still warm from the previous flight so it’s simply a case of unguarding the starter paddle on the left cockpit wall, operating it as I simultaneously switch on the mags beneath it and then holding the revs at not more than 45% with the throttle after she fires.
Close the cooling iris and wait for 120/40 CHT/oil temp, switch on the radio and intercom, and unlock the tailwheel to taxi. The view from here is even worse. But it’s nice to be in the captain’s seat, especially with Abbo in front to look after me if I screw up.
We taxi out and takeoff again. The outlook is not improved by the late afternoon sun shining through the tinted Perspex of the canopy, further obscuring the limited view forwards and to the sides of the front seater.
I get airborne and switch from the ‘acro’ tank to the wing tanks with the sliding selector under the right canopy rail. We do that to conserve the acro tank fuel, which this engine can gobble up in little over thirty minutes at full power?plus we mustn’t have any fuel in the wings during aerobatics otherwise it could rush to the tips during rolling manoeuvres and the hydraulic pressure burst the tanks. As Mike Collett put it “there’s a lot more to do and think about when flying a Sukhoi compared to a western aircraft such as an Extra 330.”
At a cruise speed of 280kmh at seventy per cent power we are soon in the training area for some general handling and aeros. In anticipation I open the iris fully and then push in the ‘lolly pop’ oil cooler control underneath it.
First I try a stall: apart from catching a gentle swing to the right as I close the throttle, there’s not much to do except progressively raise the nose to what ends up looking like an alarming angle before the G break occurs cleanly at 110kmh. Next we do it with power. Predictably it’s a different affair with a pronounced wing drop but everything gets sensible, with a normal stall recovery.
Let’s try a spin. Controversial but true, as with many aircraft the Su-29 recovers from a spin better if you keep some power on to energise the controls, but everything is straightforward. Abbo demonstrates his party piece here?a spin recovery with aileron only! Spin entry is normal and the aircraft behaves predictably but for the exit Abbo first centralises the controls then pushes the stick across towards the rotation of the spin.
The aircraft stops rotating and exits the manoeuvre with an aileron roll! Think about it?the upgoing aileron unstalls the wing on the inside of the spin so now both wings are flying again; the downgoing aileron on the outside of the spin provides a rolling input. Evidently you can do the same thing in an Extra 330 and in many aircraft fitted with full- span ailerons.
I fly a short sequence of aerobatics and am really enjoying myself with the amazing controllability of this aircraft and what feels like unlimited power. The roll rate is phenomenal?more than 360 degrees per second for sure and quicker than I can time and calculate with any precision.
One thing I do notice is that I’m instinctively using two hands on the stick. It’s two-handed for two reasons: the roll forces are very heavy at high deflection, and it’s easier not to accidentally put in a pitch input when rolling. Ideal control harmony is ‘123’ for ailerons, elevator and rudder respectively, whereas the Sukhoi’s is more like 311.
It takes a lot of getting used to. Because the of the light pitch forces, powerful elevator and reclined seat position (which is actually very comfortable in flight I have to say) I glance at the G meters and am surprised to see +6/-2 recorded, when my normal routine is no more than +4/-1.
Then Abbo takes over and demonstrates the aircraft much farther towards its ultimate potential of +12/-10 G and... it’s soon time to go home! My stomach is churning and my head spinning as I take the controls, concentrate on the horizon and turn back to base. All I can say, though, is what a machine! I would break long before it would.
Trainer and tourer
As we head back to the circuit I start to think again about what you could use this aeroplane for. Would I tour in it? The answer, surprisingly is yes. It’s actually a really nice aircraft to fly in the normal regime, the view out of the canopy is excellent everywhere except beneath the nose, it’s quick and relatively long-range. Shame that I could only pack what I’m wearing, plus maybe a toothbrush stuffed down a sock.
What about warbird training? Undoubtedly yes. If you can master a Sukhoi there’s no doubt you are well on your way to being able to fly one of the piston-engine fighters. The Su-29 is as relevant as a T-6 in terms of ground handing and, with a power-to-weight ratio similar to a P-51’s, it’s considerably more relevant in the air.
Back in the circuit everything goes well until I turn final. The sun is now low on the horizon and I really cannot see the runway. I have to go around. My next approach is a curving one and the runway view much better.
I’m only wings level for the last 100ft or so, the centre line starts tracking down my left side and I lower the aircraft onto the grass completely blind ahead but confident where I am.
The roll-out is bumpy because of the runway rather than just because of me. Welcome back to Waltham. It’s been a great training session, that’s for sure.