TB-10 Take Two

So­cata’s speedy tourer re­freshed for the 21st Cen­tury

Pilot - - FRONT PAGE - Words Dave Un­win

Hum­ming smoothly to­wards the invit­ing waters of the Chan­nel at two miles a minute I turn to Cavendish Avi­a­tion’s MD, Steve Allen and nod in agree­ment. “You’re not wrong, Steve − this is the per­fect Le Touquet air­craft!”

The French have al­ways had a rep­u­ta­tion for de­sign­ing fine fly­ing ma­chines, but as I walk to­ward the gleam­ing TB-10 Tobago my ini­tial thought is that I sim­ply can’t be­lieve that this is a 33-year-old air­frame. Built in 1983 by So­cata, which was then part of the Euro­pean Aero­nau­tic De­fence Space Com­pany (EADS − THE largest aerospace com­pany in Europe), it has been ex­ten­sively re­fur­bished by Earls Colne-based Cavendish Avi­a­tion and re­ally does look prac­ti­cally new. It is an at­trac­tive aero­plane too and, from the tip of the spin­ner to the apex of the rak­ishly swept fin, it looks fast even when it is stand­ing still. The pre-flight re­veals that it is also ex­tremely well made.

So­cata (an acro­nym for So­ciété de Con­struc­tions d’avions de Tourisme et d’af­faires) was orig­i­nally a sub­sidiary of the French aerospace gi­ant Aérospa­tiale and − as one of the main con­trac­tors for the pro­duc­tion of a large num­ber of Air­bus com­po­nents−con­se­quently had the use of a num­ber of highly so­phis­ti­cated CNC (com­puter nu­mer­i­cally con­trolled) ma­chine tools. Al­though more com­mon to­day, their use in the pro­duc­tion of light air­craft was quite un­usual 36 years ago.

De­signed dur­ing the late 1970s as a faster-fly­ing re­place­ment for the well­known Ral­lye se­ries of light air­craft, the TB line (TB for Tarbes, where the air­craft were built) in­cludes the TB-9 Tampico and TB-20 Trinidad. An­other in­ter­est­ing facet of the Tobago and in­deed the en­tire TB range (as they all share a high de­gree of com­mon­al­ity) is that the main spar is milled from a sin­gle piece of metal. This means that it is en­tirely free of any kind of join, greatly in­creas­ing its struc­tural in­tegrity.

Dis­tin­guish­ing aero­dy­namic as­pects are that its fin and rud­der are, un­usu­ally, set for­ward of the tailplane (ac­tu­ally a sta­bi­la­tor or all-fly­ing tailplane) and that there are a pair of ven­tral strakes mounted un­der the fuse­lage. Ven­tral strakes and dor­sal fil­lets al­ways make me think “Hmm, aero­dy­namic fudge” as their ad­di­tion is usu­ally to im­prove di­rec­tional sta­bil­ity. How­ever, Steve tells me that in this case So­cata fit­ted the strakes to as­sist in spin re­cov­ery (al­though the TB-10 is not ap­proved for spins). “Al­though, in prac­tice, they do as­sist greatly in hands-off di­rec­tional sta­bil­ity −as you will dis­cover.”

Any­way, de­spite my ini­tial scep­ti­cism about both the fin and those strakes, I have to ad­mit that upon closer in­spec­tion there was very lit­tle about the Tobago that I didn’t like the look of. Wher­ever pos­si­ble the aero­plane’s skin has been flush-riv­eted and the en­tire air­frame ap­pears to be es­pe­cially well made. As the en­gi­neers who orig­i­nally built the air­craft prob­a­bly also worked on Fal­con busi­ness jets and Mi­rage fight­ers, the very high build qual­ity is un­sur­pris­ing. As de­liv­ered from the

fac­tory, its 180hp Ly­coming O-360 drove a two-blade Hartzell con­stant-speed prop, but Cavendish Avi­a­tion is now up­grad­ing the air­craft by fit­ting three-blade Mccauley units with ‘Scim­i­tar’ blades. Steve was very en­thu­si­as­tic about the dif­fer­ence these new Mccauley props make, as they are much qui­eter than the orig­i­nal two-blade Hartzell. Start­ing with the next air­craft to be re­fur­bished, the com­pany also plans to re­place the orig­i­nal ex­haust with a four-into-one merged-col­lec­tor man­i­fold pro­duced by Ate­lier Chabord. With this ar­range­ment the In­conel man­i­fold con­nects to an extender pipe that car­ries a large si­lencer mounted un­der the fuse­lage, re­duc­ing noise still fur­ther. Ac­cess to the en­gine is rea­son­able (there are quite a few fas­ten­ers to undo) but the oil can be checked via a small hatch on the top of the cowl­ing. It’s quite ob­vi­ous that So­cata made a de­ter­mined effort to re­duce drag, so it’s a lit­tle sur­pris­ing that, de­spite all three un­der­car­riage wheels be­ing en­closed with tight-fit­ting spats, the nose­wheel’s drag links are ex­posed.

This must add a con­sid­er­able amount of drag.

The fuel is con­tained in a pair of 102 litre tanks lo­cated in the wing’s lead­ing edge. The wings fea­ture a small amount of di­he­dral, but are aligned chord­wise with the lon­gi­tu­di­nal axis, hav­ing zero an­gle of in­ci­dence at the root. The trail­ing edge con­sists of bal­anced ailerons and elec­tri­cally-ac­tu­ated slot­ted flaps, with a ground-ad­justable trim tab in the star­board aileron. The wingtips are fi­bre­glass. An­other aero­dy­namic anom­aly is that the sta­bi­la­tor ap­pears to have very lit­tle down move­ment. It fea­tures a full-span an­tibal­ance trim tab, while the rud­der has a ground-ad­justable trim tab.

Over­all, the TB seems to be a thought­fully de­signed, well-made ma­chine, an im­pres­sion re­in­forced when en­ter­ing the cabin, as ac­cess to the cock­pit is ex­cel­lent. There are small steps mounted ei­ther side just aft of the trail­ing edge and, with the large gull-wing doors un­locked and opened, it is easy to step up onto the wing and then down into the cock­pit. The non-slip wing­root walk­way is also sen­si­bly-sized. Some air­craft have ridicu­lously nar­row walk­ways and you are al­ways very aware that it would be only too easy for some­one to step where they shouldn’t. Upon set­tling into the com­fort­able seat I was im­me­di­ately struck by how roomy the cock­pit is. The cabin is about 125cm wide at shoul­der height, which for an air­craft in this class is very gen­er­ous, and com­bined with the large windows which ex­tend up into the roof re­ally does make the cabin feel as if it is ac­tu­ally part of a much larger air­craft. The rear seat is of the bench type and later mod­els were cer­ti­fied for three oc­cu­pants in the back, al­though I imag­ine that they would all need to be sig­nif­i­cantly slim­mer than me! The test air­craft is s/n0058, and a four-seater. Apart from the two gull-wing doors there is also a sep­a­rate bag­gage bay hatch on the port side of the fuse­lage aft of the wing. The bag­gage bay can carry up to 45kg, is quite ca­pa­cious and ac­ces­si­ble in flight, al­though I did think that the bag­gage bay door could have been a bit big­ger.

Ex­tremely spa­cious cock­pit

I thought the cock­pit was ex­tremely spa­cious and quite well laid out al­though, as reg­u­lar read­ers might have al­ready guessed, there are some er­gonomic ar­eas that I found less than sat­is­fac­tory, such as the power con­trol levers. At the base of the avion­ics stack is a large cen­tre con­sole that ex­tends back be­tween the front seats. This car­ries the throt­tle, prop, mix­ture and carb heat levers, and al­though they’re cor­rectly shaped and or­dered, the colours aren’t en­tirely right (the carb heat is blue, the colour cor­rectly used for the pro­pel­ler). Not an is­sue for the pri­vate owner, but the sort of ‘gotcha’ that just might con­fuse a low-houred renter un­der stress. Con­versely, the pitch trim wheel is per­fect: large, nicely geared and ex­actly where you’d want it (just be­hind the throt­tle lever) with the pitch trim in­di­ca­tor ad­ja­cent.

Just in front of the power con­trol levers are the but­tons for the electrics, an aero­foil-shaped switch for se­lect­ing the flaps and a flap po­si­tion in­di­ca­tor. Un­less you’ve flown other So­cata air­craft (such as the Ral­lye) you’ll find the sys­tem used for se­lect­ing the elec­tri­cal ser­vices to be slightly un­usual as they favoured us­ing ther­mal over­load but­tons. Con­se­quently each ser­vice has two push but­tons, a now rather yel­lowed white one for on and a red one for off. Un­for­tu­nately, these aren’t la­belled ei­ther − and they re­ally should be. The cir­cuit break­ers are lo­cated in a neat stepped panel close to the pi­lot’s left knee, and the cock­pit also has some very use­ful stowage ar­eas for air­ways man­u­als and the Pi­lot’s Op­er­at­ing Handbook. The com­fort­able con­trol yokes are nicely trimmed in leather, while the beefy

rud­der ped­als are sus­pended from be­low the in­stru­ment panel. Other good fea­tures are that the fuel tank se­lec­tor and park brake are both un­der the pi­lot’s yoke, where they are easy to see and reach, while a small panel in the roof con­tains use­ful op­er­at­ing lim­i­ta­tions.

I’ve al­ready men­tioned that the Tobago gives the im­pres­sion of be­ing a larger air­craft than it ac­tu­ally is, and this il­lu­sion is enhanced by the in­stru­ment panel. Con­sist­ing of three padded ‘boxes’, the one in front of the pi­lot car­ries all the pri­mary flight in­stru­ments and also a very com­pre­hen­sive an­nun­ci­a­tor panel, while the one on the right con­tains the power gauges and some ad­di­tional flight in­stru­ments. In the cen­tre of the panel is a large ver­ti­cal stack crammed with avion­ics, in­clud­ing a GPS and au­topi­lot, and topped with some un­usual ver­ti­cal-read­ing gauges that show oil pres­sure and tem­per­a­ture, fuel quan­tity and pres­sure and volts. How­ever, I have two fairly ma­jor beefs: first, the an­nun­ci­a­tor panel is not la­belled but sim­ply marked with some­what vague sym­bols to show what is what. I don’t care for it. Sec­ond, the gauges in the mid­dle (with the ex­cep­tion of fuel quan­tity) are only colour-coded. Now, I’d rather know (for ex­am­ple) that when I’m cruising at “23 squared” on an ISA day that the oil is at a spe­cific pres­sure and tem­per­a­ture and the fuel at a spe­cific pres­sure, so I can track trends. This ar­range­ment is far too neb­u­lous for my taste, par­tic­u­larly when al­lied with the not-easily in­ter­preted an­nun­ci­a­tor lights.

By now you’re prob­a­bly won­der­ing, “Why didn’t they go glass dur­ing the re­furb?” Well, firstly a pair of Garmin G1000s isn’t cheap, and it is also ir­refutable that many pilots still pre­fer nice round ana­logue di­als, ar­ranged in the clas­sic ‘sa­cred six’. Hav­ing a rea­son­able amount of time in glass cock­pits but hav­ing earned my In­stru­ment Rat­ing on steam gauges, I can hon­estly say I see both ar­gu­ments − al­though on bal­ance I do feel that a fully in­te­grated dig­i­tal cock­pit is a su­pe­rior so­lu­tion. That said, Cavendish does of­fer a be­spoke ser­vice (Steve was adamant that any avion­ics suite should be “pi­lot-in­spired”) so you pays your money and takes your choice!

On the plus side, the re­fur­bish­ment didn’t fin­ish with the ex­te­rior. The seats have been re-up­hol­stered, the leather--

cov­ered yoke is hand-stitched, and the in­te­rior smells like an ex­pen­sive new car − a mi­nor point, but not an in­con­se­quen­tial one. Steve told me about a re­cent cus­tomer whose wife had com­mented how nice it was to go from their As­ton Martin into an equally sump­tu­ous aero­plane, and I knew ex­actly what she was get­ting at. I’ve of­ten won­dered how many peo­ple have been turned off GA when they ar­rived at the air­field in a brand new lux­ury car, and then got into some­thing with an in­te­rior rem­i­nis­cent of a 1975 Austin Al­le­gro.

The seats ad­just over a re­spectable range and, in com­mon with many other mod­ern air­craft, in­er­tia-reel seat belts are fit­ted. Fine for the pas­sen­gers, but I al­ways be­lieve the pi­lot should have a four-point har­ness. A real od­dity is that, when you first sit down, the seats re­ally aren’t that com­fort­able. (I ac­tu­ally thought I was sit­ting on some ob­ject!) Ini­tially it’s quite ob­tru­sive, but af­ter a few min­utes it sim­ply goes away. The doors are well sup­ported by gas struts and it is easy to swing them gen­tly shut. Pulling the lock­ing han­dle to ‘closed’ draws the door snugly into its seal. The Ly­coming starts read­ily (once I re­mem­ber to push in the ro­tary mag switch to start up − an­other French foible) and, with Steve in the other seat, I taxi out to Earls Colne’s Run­way 24.

The Tobago is, like most mod­ern air­craft with a tri­cy­cle un­der­car­riage, very easy to

The leather cov­ered yokes are hand-stitched and the in­te­rior smells like an ex­pen­sive new car

taxi, al­though the nose­wheel only steers through a rel­a­tively nar­row arc so a dab of dif­fer­en­tial brak­ing is re­quired for a tighter turn. The toe-op­er­ated hy­draulic disc brakes have a nice pro­gres­sive feel and the field of view is good.

Pre-take­off checks are pretty well stan­dard for this class of air­craft, so with the prop set fully fine, fuel pump on, take­off flap set (ten de­grees) and the el­e­va­tor trim neu­tral, I care­fully line up with the cen­tre­line (I say ‘care­fully’ as the run­way seems slightly nar­rower than nor­mal). As it is al­ready quite warm with just a gen­tle zephyr blow­ing I take Steve’s ad­vice to stand on the brakes and run the en­gine up to 2,700rpm with as much man­i­fold pres­sure as we can get. With full fuel, no bag­gage and only two adults aboard we are around 170kg be­low the max­i­mum all-up weight of 1,150kg and the ac­cel­er­a­tion − al­though far from star­tling − is ad­e­quate. A fairly hefty pull on the yoke is re­quired to ro­tate the Tobago into the take­off at­ti­tude at just over 65kt, but as we have a fairly for­ward C of G this must be taken into con­sid­er­a­tion. Any­way, hav­ing used about half of the 840m avail­able, the Tobago is off the ground at around seventy knots and soon set­tles into a good climb of al­most 1,000fpm.

Pass­ing rapidly through 500 feet I press the flap switch to up, turn off the fuel pump, pull throt­tle and prop back to 25/25, nudge the pitch trim wheel for­ward and set off in pur­suit of the camera ship. The Tobago’s Vy (best rate of climb speed) is eighty knots but I de­lib­er­ately trim for ninety in or­der to im­prove the for­ward vis­i­bil­ity. This is not to say that the field of view is sub­stan­dard though − far from it. With such large windows and a very gen­er­ous wind­screen it’s ac­tu­ally su­perb while the sub­tle tint (part of the re­fur­bish­ment) is an­other nice touch.

It re­ally is a beau­ti­ful sum­mer’s day, and head­ing straight to­wards France in a French air­craft seems en­tirely ap­pro­pri­ate. It’s a shame we just can’t cross the coast and keep on go­ing but there’s work to do, and as we close on the Cessna 172 the win­dow swings up and Keith waves us into po­si­tion.

When as­sess­ing an air­craft’s over­all con­trol char­ac­ter­is­tics I al­ways feel that an ex­cel­lent in­di­ca­tor is how easy it is to fly in for­ma­tion, and Keith’s fine pho­to­graphs quite clearly show that, with very lit­tle time on type, I was both con­fi­dent and com­pe­tent enough with the Tobago to hold a per­fectly rock-steady for­ma­tion on the camera ship.

Ear­lier on in this re­port I said that the Tobago feels like it is big­ger than it re­ally is. Well, it also flies like it’s big­ger than it re­ally is. This is al­most cer­tainly due to the rel­a­tively low wing area and con­se­quently high wing load­ing. For ex­am­ple, the diesel-pow­ered Piper Archer that I tested for Pi­lot a few years back has a max­i­mum take­off weight some 10kg more than the Tobago, at 1,160kg. How­ever, its much greater wing area (15.79sq m), against the Tobago’s 11.90) means that the Tobago’s wing load­ing is sig­nif­i­cantly higher than the Archer’s – and in­deed most sim­i­lar air­craft. The net re­sult is a much firmer ride. With the photo shoot over I break away from the Cessna and be­gan to ex­per­i­ment fur­ther with the Tobago’s han­dling and per­for­mance char­ac­ter­is­tics. Set­ting the air­craft up for the cruise at 3,000 feet, I draw the throt­tle and pro­pel­ler levers back to ‘23 squared’ and the nee­dle of the ASI even­tu­ally set­tles just over the 115kt mark, for a true air­speed of around 120kt. I have to guessti­mate the ac­tual TAS, as al­though the ASI is of the type that can be cor­rected for tem­per­a­ture, there isn’t an OAT gauge! Any­way, 120 is a re­ally good ‘go­ing places’ speed, and at two miles a minute in still air the time/dis­tance cal­cu­la­tions are a breeze! It can go faster of course, but at the ex­pense of a lot more fuel be­ing con­sumed, while at 23/23 the fuel flow of around thirty litres per hour is per­fectly

The Tobago feels like it is big­ger than it re­ally is... it also flies like it’s big­ger than it re­ally is

ac­cept­able. In fact, I was pleas­antly sur­prised by its cruise per­for­mance, as the TB se­ries is fit­ted with a con­stant chord wing, a de­sign not known for con­fer­ring com­mend­able cruise char­ac­ter­is­tics. This TB-10 is also very smooth and quiet.

An ex­plo­ration of the stick-free sta­bil­ity re­veals the air­craft to have strong lon­gi­tu­di­nal sta­bil­ity and weak lat­eral sta­bil­ity. The pro­nounced lon­gi­tu­di­nal sta­bil­ity is prob­a­bly a func­tion of our for­ward C of G, while the low lat­eral sta­bil­ity (just barely pos­i­tive) is shared by many mod­ern light tour­ers. Di­rec­tional sta­bil­ity is good, helped no doubt by those ven­tral strakes.

Nicely co­or­di­nated con­trols

Slow­ing down to ex­plore the stall regime takes a while, as the air­craft is quite slip­pery, so to shed some en­ergy I ex­per­i­ment with some steep turns. The flight con­trols are pow­er­ful and nicely co­or­di­nated, al­though the ailerons do seem a tri­fle on the heavy side. In­ter­est­ingly, and also un­usu­ally, all the pri­mary flight con­trols, in­clud­ing the rud­der, are driven by push-rods. The stall is per­fectly in­nocu­ous, both flaps up and flaps down. With full flap the stall oc­curs at 49kt, and is pre­ceded by aero­dy­namic buffet and also a warn­ing bell, ac­ti­vated by a small vane in the left wing. Cleaned up, it stalls at about sixty and, as ex­pected, there is markedly less aero­dy­namic buffet. This is slightly faster than I’d an­tic­i­pated, but the C of G is well for­ward. In­ci­den­tally, the stall warner is al­most mu­si­cal, and while it would make a fine door­bell it’s a lit­tle too gen­teel and sub­tle for warn­ing that you’re ap­proach­ing crit­i­cal alpha. Be­hav­iour at the stall is very be­nign; ini­tially it be­gins to mush and then gen­tly breaks straight ahead with ab­so­lutely no ten­dency to drop a wing.

Back at Earls Colne a good speed to start from in the cir­cuit at our weight seems to be 90kt, with 80 on base leg, bleed­ing back to 75 on fi­nal with a ‘last-look’ speed of just un­der 70. Vfe is 95. The TB-10 is very speed-sta­ble and easy to land, al­though it does seem to like just a hint of power left on all the way down and the stick forces do feel quite high in the flare. Again, prob­a­bly a func­tion of our for­ward C of G.

Just like for­ma­tion fly­ing, you can learn more about an air­craft dur­ing a few ‘cir­cuits and bumps’, and with each touch-and-go I feel in­creas­ingly at home. None of the land­ings is bad, but I even­tu­ally get a real squeaker, and then call it a day.

Con­clu­sions? Well, the TB-10 of­fers a good com­bi­na­tion of speed and econ­omy, al­lied with nice han­dling and a fine bal­ance be­tween con­trol and sta­bil­ity, all wrapped up in a large, com­fort­able cabin with a grace­ful, Gal­lic ap­pear­ance. Paint the prop and carb heat levers the right colours, spend half an hour with a Dymo la­bel writer and you’d own an air­craft that re­ally does rep­re­sent ex­cep­tional value for money.

Pho­tos Keith Wil­son

1

It’s an en­tirely sub­jec­tive judge­ment, but to our eyes the slightly an­gu­lar lines of TB-10 have aged well and, in this re­freshed glossy-fin­ish form it re­ally looks any­thing but dated

The TB shows off its plan form - its rel­a­tively small wing area/high wing load­ing helps give a smooth ride in tur­bu­lence

Above: xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx x xxx xxxx xxxxv

The TB’S all-pushrod con­trol sys­tem con­fers nice con­trol re­sponse

Cavendish’s next TB, stripped down for a re­fur­bish­ment that is very much more than skin deep

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