Flight Test: Cessna TTX

De­scended from Lan­cair’s Columbia, and pre­vi­ously known as the Cessna 400, there’s no con­fu­sion about the han­dling and range ca­pa­bil­i­ties of this speedy ma­chine

Pilot - - CONTENTS - Words Dave Unwin Pho­tos Cessna

The world’s fastest sin­gle-en­gined pis­ton tourer is also one of the nicest to fly

As the gleam­ing Cessna TTX turned onto the taxi­way I glanced at my watch and noted it was 1102. “Sorry I’m late,” said Peter Herr, as we shook hands out­side Gam­ston’s op­er­a­tions build­ing. “Hey, what’s a cou­ple of min­utes be­tween friends,” I grinned, then paused. “Hang on, have you just flown di­rect from Ger­many?”

The TTX rep­re­sents a sig­nif­i­cant de­par­ture from the norm for the Cessna Air­craft Com­pany. Al­though it has built more than 190,000 sin­gle-en­gined aero­planes, most had two things in com­mon. Ir­re­spec­tive of whether the en­gine was a pis­ton or a tur­bine−or if the third wheel was at the front or back−they were made of me­tal and had a high-wing con­fig­u­ra­tion. How­ever, not only is the TTX of com­pos­ite con­struc­tion and with a low-wing lay­out, it is also the first Cessna that was not de­signed and cer­ti­fied in house, as it is derived from the Columbia 300, 350 and 400 series de­signed by the Lan­cair Com­pany of Bend, Oregon. Hav­ing flown all the Columbia series (al­beit many years ago) I was very much look­ing for­ward to see­ing just how much Cessna had done to what was al­ways a very im­pres­sive ma­chine.

De­spite hav­ing a fixed un­der­car­riage, the TTX is the fastest sin­gle pi­s­to­nengined four-seat tourer in the world and, as you’d ex­pect, the wing fea­tures some ad­vanced aero­dy­nam­ics to al­low it to func­tion ef­fi­ciently and safely at the ex­tremes of the op­er­at­ing en­ve­lope. These in­clude large drooped ‘cuffs’ on the lead­ing edge, lo­cated at ap­prox­i­mately the same chord line as the in­board end of the ailerons, and lit­tle plates at­tached to the out­board ends of the ailerons. These plates project down into the high-pres­sure air and con­strain the span-wise air­flow, in­creas­ing the ef­fi­ciency of the ailerons and en­sur­ing they re­main ef­fec­tive, even at high al­pha. There is no washout (built-in twist to re­duce the an­gle of at­tack of the outer por­tion of the wing): in­stead two stall strips on each lead­ing

edge en­sure that the wing stalls at the root well be­fore the tip, and Peter as­sured me that the com­bi­na­tion of cuffs, plates and large Fowler flaps all com­bine to grant the TTX ex­cel­lent low-speed char­ac­ter­is­tics, de­spite its im­pres­sive top speed.

The high speed cor­ner of the en­ve­lope was the bit I was look­ing for­ward to ex­am­in­ing. It’s not hard to make a 310hp tur­bocharged air­craft go fast, nor is it par­tic­u­larly dif­fi­cult to de­sign a four-seat air­craft to fly slowly. The real achieve­ment is to make it do both.

Cessna may not have had a lot of ex­pe­ri­ence of con­struct­ing with com­pos­ites but it clearly learned quickly, for close in­spec­tion of the two-spar wing re­veals it to be ex­tremely well made and ex­traor­di­nar­ily smooth. Al­though the air­craft is made pri­mar­ily from GRP, the main spars, doors, cowl­ings, flaps and all the fly­ing con­trols are made from car­bon fi­bre com­pos­ite, as are the tailplane ribs and spars. Me­tal is used only for the un­der­car­riage legs and for the mount­ing tubes for the tailplane.

An­other change from most sin­gleengine Cess­nas is that pushrods are used to op­er­ate the ailerons and el­e­va­tors. The flaps and speed­brakes−an­other de­vi­a­tion from the Cessna norm−are elec­tri­cally ac­tu­ated; the flaps have three set­tings: up, 12° for take­off, and 40° for land­ing. As the TTX is cer­ti­fied for IFR, light­ning pro­tec­tion is pro­vided by the in­cor­po­ra­tion of a me­tal mesh (cop­per or alu­minium) into every ex­te­rior sur­face of the air­craft. Com­pos­ite air­craft can be badly af­fected by light­ning strikes, as the ma­te­ri­als used in their con­struc­tion are non-con­duc­tive, and be­cause the TTX is very much an ‘elec­tric aero­plane’ it is vi­tally im­por­tant that the en­ergy from a light­ning strike−or even an ac­cu­mu­la­tion of static elec­tric­ity− is dis­si­pated safely and ef­fec­tively. Con­se­quently, a con­sid­er­able num­ber of static wicks pro­trude from the trail­ing edge of the wings and el­e­va­tor to al­low any build-up of static to be dis­charged safely with­out ad­versely af­fect­ing any of the

elec­tri­cal sys­tems. The FIKI (flight into known ic­ing) pack­age uses TKS fluid via a ‘weep­ing wing’ sys­tem for the lead­ing edges of the wings, fin and tailplane, and a slinger ring for the prop.

The tri­cy­cle un­der­car­riage is a fixed tubu­lar steel ar­range­ment fit­ted with toe-ac­tu­ated hy­draulic Cleve­land brakes and a cas­tor­ing nose­wheel. At 2.2m the wheel track is rel­a­tively wide, while the wheel­base is only slightly smaller at just over 2m. All three wheels are quite closely spat­ted (as you’d ex­pect of an air­craft that has been de­signed to fly fast with a fixed un­der­car­riage), the main­wheels us­ing 6.00-6 tyres and the nose­wheel a 5.00-5. How­ever, the down­side is that as the tyres are not very big, if op­er­ated at the 1,633kg MAUW on a soft sur­face the TTX would soon sink down to the spats. Un­like most Cessna sin­gles, it is not a good aero­plane for soft or un­pre­pared run­ways (to be fair, nei­ther is its clos­est com­peti­tor, the SR22). While this is a triv­ial point in the USA, which has plenty of hard-sur­faced run­ways, in Europe even some quite large fields are all-grass. In­ter­est­ingly, the main­wheel spats are fit­ted with small NACA ducts to al­low the heat to dis­si­pate should the

If op­er­ated at MAUW on a soft sur­face, the TTX would sink down to the spats

brakes be used over-en­thu­si­as­ti­cally. And if you’re won­der­ing why the un­der­car­riage is fixed, the rea­sons are sim­ple: cost, com­plex­ity, weight, and cheaper in­sur­ance where there is no dan­ger of land­ing wheels-up!

The air­craft I flew was fit­ted with the in­creas­ingly fa­mil­iar Hartzell ‘Scim­i­tar’ three-blade pro­pel­ler (al­though Mc­cauley props are now stan­dard) set be­hind a highly-pol­ished spin­ner. It is turned by a 310hp Con­ti­nen­tal TSIO-550-C fit­ted with dual tur­bocharg­ers and in­ter­cool­ers which can put out up to 85% power at 25,000ft, and all 310hp at al­ti­tudes as high as 18,000ft. There’s an in­trigu­ing plunger in the cowl’s port air in­take which al­lows the oil cooler’s in­let to be ad­justed prior to flight to suit am­bi­ent air tem­per­a­ture. Some­what sur­pris­ingly, cowl flaps are not fit­ted.

The el­e­va­tor is a two-piece unit, while the rud­der ap­pears no­tice­ably larger than on the Columbia (both in chord and span), and a sub­stan­tial, raked ven­tral strake has been added to­wards the rear of the em­pen­nage. This in­creases keel area to aid in spin re­cov­ery, for whereas the 300 and 350 pro­gen­i­tors were cer­ti­fied with the FAA as be­ing ‘spin re­sis­tant’ (in­ca­pable of depart­ing con­trolled flight into a spin), the 400 and TTX are ‘spin re­cov­er­able’.

Ac­cess to the cock­pit is very good. The gen­er­ously-sized gull wing doors open wide and are held up by gas struts−and sen­si­bly-sited han­dles and steps make it easy to step up onto the wing. In­stead of a large non-slip walk­way, there are merely slen­der strips of non-skid ma­te­rial on the wing. Clearly, every ef­fort has been made to re­duce drag.

My ini­tial im­pres­sion of the in­te­rior is that it is more like an ex­pen­sive car than a GA air­craft, as the seats and side­walls are cov­ered with hand-stitched leather. An­other fea­ture that en­hances the au­to­mo­tive anal­ogy (but di­min­ishes the air­craft in my eyes) is that the re­straint sys­tem is an in­er­tia-reel three-point har­ness. Al­though very com­fort­able, I didn’t much care for it, as the only re­straint sys­tem bet­ter than a four-point har­ness is a five-point har­ness! On the plus side, the en­ergy-ab­sorb­ing seats ex­ceed cur­rent FAA cer­ti­fi­ca­tion re­quire­ments, the cock­pit in­cor­po­rates a roll-cage ca­pa­ble of sup­port­ing three times the air­craft’s weight, and in the event of the air­craft com­ing to rest in­verted it is pos­si­ble to jet­ti­son the doors. Be­hind the rear seats, which are held in by pip-pins, is the ca­pa­cious bag­gage bay which can not only carry a good weight but−more im­por­tantly −a con­sid­er­able vol­ume. It is ac­cessed via a large, lock­able door on the port side, and an ex­cel­lent fea­ture is that you can­not re­move the key from the lock un­less it is se­cured.

I like the lo­ca­tion of the stepped cir­cuit­breaker panel, which is on the port side­wall by the pilot’s left knee; it is both easy to see and, more im­por­tantly, reach. Any pilot who has ever fum­bled with a re­cal­ci­trant cir­cuit-breaker will read­ily agree. An­other non-cessna fea­ture is the side­stick. Note that this is a true, fully ar­tic­u­lated side­stick and not the for­ward and aft slid­ing ‘side-yoke’ fit­ted to Cir­rus air­craft. I also ap­prove of the elec­tronic cli­mate con­trol sys­tem, which in­cor­po­rates a full air con­di­tion­ing pack­age−a vast im­prove­ment over the heat­ing and ven­ti­la­tion sys­tems fit­ted to most light air­craft. I’m not so keen on the lo­ca­tion of the park brake−it’s also on the port side­wall un­der the panel and a bit of a stretch. Nei­ther Peter nor I are as thin as we once were, and he al­lowed that it would be bet­ter if it were a bit more ac­ces­si­ble.

Dual elec­tri­cal sys­tems

To meet and ex­ceed the re­quire­ments of this ‘elec­tric aero­plane’, two 28-volt/15amp hour bat­ter­ies are fed from a pair of pow­er­ful al­ter­na­tors, and dis­trib­ute the power via sep­a­rate busses. Not only are

these dual sys­tems en­tirely in­de­pen­dent, but ei­ther one has the ca­pac­ity to power all the es­sen­tial sys­tems−in­clud­ing standby EFIS, fuel pump and flaps−via its own Es­sen­tial Bus Cir­cuit. The pri­mary flight dis­play (PFD) will al­ways have power, as it is con­nected to both busses− the level of re­dun­dancy pro­vided is quite out­stand­ing. One fur­ther re­fine­ment is that, should one al­ter­na­tor fail, all the pilot needs to do is press the ‘cross-tie’ switch to en­sure that both bat­ter­ies are charg­ing and al­low even the non-es­sen­tial sys­tems to con­tinue to be pow­ered.

The avion­ics pack­age is Garmin’s amaz­ing G2000, and the instrument panel is filled with the two twelve-inch PFDS, and an L3 Com­mu­ni­ca­tion ‘Tril­ogy’ standby EFIS (elec­tronic flight instrument sys­tem) to the left of the pilot’s PFD. The G2000 is the ‘pis­ton’ ver­sion of the G3000−or is it the other way round−that I dis­cussed in my flight test of the Piper M600 tur­bo­prop ( Pilot August 2017). So rather than re­peat­ing ev­ery­thing about how in­tu­itive are the dig­i­tal touch­screen and shal­low menu struc­ture, how much I like the Syn­thetic Vi­sion and 60/40 screen split, or how it re­tains the same ‘ESP’ and ‘USP’ pro­tec­tions pro­vided by the GFC 700 au­topi­lot’s en­hanced au­to­matic flight con­trol sys­tem, (which can even fly cou­pled go-arounds)… well, let’s just say that it truly is bril­liant. In fact, un­til you fly with a G2000, it is dif­fi­cult to ap­pre­ci­ate just how pow­er­ful it is.

De­spite the amaz­ing avion­ics suite, the TTX panel is no­tice­ably less clut­tered than that of the Columbia 350 that I flew in 2004, as some of the switches (big, chunky rock­ers) have been moved to a neat over­head panel. It was in­ter­est­ing to note that de­spite ev­ery­thing be­ing elec­tronic, man­i­fold pres­sure and rpm are shown on ana­logue pre­sen­ta­tions as well as dig­i­tal. There was also some­thing I’d never seen be­fore: the ‘Pulse Oxime­ter’ be­low the standby EFIS. This al­lows the pilot to mon­i­tor their pulse and oxy­gen lev­els reg­u­larly by in­sert­ing their in­dex fin­ger−a worth­while check when cruis­ing at FL250 in an un­pres­surised aero­plane (and one that per­haps gives new mean­ing to the ex­hor­ta­tion to ‘Get your fin­ger out’−ed).

All three pri­mary en­gine con­trols are of the Vernier type and are mounted in a neat line at the base of the panel, along with the flap se­lec­tor and but­tons for ‘Go Around’ and ‘Rud­der Hold’ (a fea­ture that is es­pe­cially use­ful in the climb, as we shall see). The speed­brake switch is lo­cated be­tween the throt­tle and prop plungers, per­fectly placed for your right in­dex fin­ger. How­ever, I’m not en­tirely con­vinced about

its er­gonomics. Al­though lift­ing it up does raise or ex­tend the speed­brakes, this is not as log­i­cal as you may at first think, as de­ploy­ing them makes the air­craft ei­ther slow down or de­scend. If I’d de­signed this sys­tem, I’d have made the switch func­tion the same way as the un­der­car­riage and flap selec­tors do on most air­craft i.e. up to fly and down to land−and then re­la­belled the switch in and out in­stead of ‘up’ and ‘down’.

Trim­ming in both pitch and roll is all elec­tric and is done via a neat lit­tle ‘coolie-hat’ switch on the side­stick’s top which also has but­tons for ‘Con­trol Wheel Steer­ing’, au­topi­lot dis­con­nect and of course a PTT. Trim and flap po­si­tion are shown on the G2000. The flap switch is ex­actly how all flap switches should look: large, aero­foil­shaped and with the lim­it­ing speeds marked next to the rel­e­vant set­ting.

Solid feel

The en­gine starts read­ily and, hav­ing in­flated the door seals, sim­ply taxy­ing out to­wards the ac­tive run­way gives an in­di­ca­tion of the Ttx’s char­ac­ter. It re­ally feels solid. The un­der­car­riage pro­vides a firm, com­fort­able ride, with an ex­cel­lent turn­ing cir­cle (cour­tesy of the cas­tor­ing nose­wheel) and pow­er­ful, pro­gres­sive toe-op­er­ated hy­draulic disc brakes. The field of view is good.

Out on the run­way I bring the power in slowly. All en­gines should be treated with re­spect, and this is dou­bly true if they’re tur­bocharged. Fur­ther­more, a swing is more likely with a cas­tor­ing nose­wheel at slow speed if full power is ap­plied too quickly−and we have 310hp turn­ing a large, three-blade prop. Ac­cel­er­a­tion is ex­cel­lent: any ten­dency to swing is eas­ily con­trolled once the pow­er­ful rud­der has some air flow­ing over it and we quickly reach the Vr (ro­ta­tion speed) of 70 knots. Smooth ap­pli­ca­tion of aft side­stick and we rocket sky­ward. Al­though the speed for best climb, Vy is 110kt, for­ward vis­i­bil­ity is some­what con­strained at this speed due to the steep deck an­gle, so I lower the nose and climb at 125. This still pro­duces over 1,000ft/min, al­though climb­ing at Vy would in­crease the climb rate to 1,400.

Dur­ing the walkaround I’d noted the ab­sence of pilot op­er­ated rud­der trim (the small trim tab is only ground ad­justable) and had ex­pected to have to ap­ply quite a bit of right rud­der dur­ing the climb. How­ever, with the rud­der hold sys­tem all you do is cen­tre the slip in­di­ca­tor on the PFD, then press the Rud­der Hold but­ton. It’s great−in fact if climb­ing at full power at the best an­gle speed, Vx of only 82kt, the pedal loads would prob­a­bly be­come quite oner­ous with­out it.

To ex­plore the gen­eral han­dling we climb rapidly to 6,000ft for a look at the stall char­ac­ter­is­tics and stick-free sta­bil­ity. As you would ex­pect, the twin tur­bos en­sure there’s ab­so­lutely no drop-off in en­gine per­for­mance as we climb, and the man­i­fold pres­sure re­mains rock-steady at 35 inches.

For such a fast aero­plane the slow speed side of the en­ve­lope is very benign. Ir­re­spec­tive of whether the flaps are up or down, and with var­i­ous power set­tings, stalls are very gen­tle. Clear tes­ti­mony to the ef­fi­ciency of the wings’ drooped cuffs, stall strips and those plates on the aileron’s out­board ends is the fact that full roll

con­trol is re­tained even when the wing is com­pletely stalled. At our rel­a­tively light weight, this oc­curred at an IAS of 55kt.

An ex­am­i­na­tion of the stick-free sta­bil­ity re­vealed it to be pos­i­tive di­rec­tion­ally, and lon­gi­tu­di­nally, and neu­tral lat­er­ally. The TTX would be quite an easy air­craft to hand-fly on in­stru­ments, al­though with such a pow­er­ful au­topi­lot I’m sure most peo­ple wouldn’t want, or bother to do so in IMC. That said, in VMC the TTX begs to be flown by hand. Al­though quite clearly de­signed as a se­ri­ous trav­el­ling ma­chine, it re­ally does pos­sess ex­tremely fine han­dling. Break­out forces are very low, there’s practically no stic­tion and all three pri­mary con­trols are agree­ably har­monised, well bal­anced and nicely weighted, pro­vid­ing crisp and pre­cise han­dling, while the rud­der hold−ef­fec­tively a zero-slip rud­der trim­mer− def­i­nitely spoils you! The field of

The TTX would be quite an easy air­craft to hand-fly on in­stru­ments

view in the turn (and in­deed every phase of flight) is good, while as the wing load­ing is quite high, it pro­vides a nice sta­ble ride in tur­bu­lence.

Time for a look at the cruise. The TTX re­ally hits its stride at FL250 but, while cruis­ing at 25,000ft puts you above most of the weather, I doubt many peo­ple are keen to fly an un­pres­surised air­craft like this as high as that. As it is we do not have enough time in hand to climb to al­ti­tude and re­ally make the best use of those twin tur­bos and in­ter­cool­ers, but the num­bers I see at more rep­re­sen­ta­tive al­ti­tudes are still hugely im­pres­sive and−per­haps more im­por­tantly, ex­actly what the POH says they’d be. In the USA it is pos­si­ble to fly VFR be­low FL180, and I think that most pi­lots would plan to cruise at around 14-16,000ft. At those al­ti­tudes a power set­ting of 80% (32in MP and 2,500rpm) pro­duces a TAS of an in­cred­i­ble 220kt, for a fuel flow of around 80 lit/hr. And remember, the un­der­car­riage is ‘down and welded’. Pick up a de­cent tail­wind (and it can get windy up there) and ground­speeds in ex­cess of 300kt are per­fectly achiev­able.

The num­bers for range and en­durance are also very good. The two fuel tanks have a to­tal ca­pac­ity of 400 litres (380 use­able), which means that even with IFR re­serves you can safely plan your re­fu­elling stops to be at least 850nm apart. And of course, if you want econ­omy the ‘speed squared’ law

means that only a slight power re­duc­tion im­proves both range and en­durance ap­pre­cia­bly.

Now for some cir­cuits. The G2000 makes nav­i­ga­tion sim­ple, but I still man­age to ar­rive both faster and higher than in­tended, so ex­tend the speed­brakes. They work well, which is use­ful as at only 117kt the Vfe is not as high as I would like. Fly­ing the TTX in the cir­cuit is easy, with a fair field of view, ef­fec­tive flaps and of course those speed­brakes. Pitch trim changes with flap se­lec­tion are easy to trim out and the trim­mer is per­fectly geared.

On fi­nal, the air­craft is very speed-sta­ble, and I have no dif­fi­culty hold­ing the briefed speed of eighty knots. How­ever, even with the speed­brakes out, the TTX re­ally is very slip­pery, and hav­ing turned base a bit early I have to cheat and throw in a steep sideslip to sort things out. The air­craft slips well.

For the first land­ing I re­tract the speed­brakes on short fi­nal, and we float fur­ther than I in­tended. The touch­down is fine−just a lit­tle deep, while the ‘go’ part of the touch and go is… well, let’s say em­phatic. On the sec­ond ap­proach, I ex­tend the down­wind leg, leave the speed­brakes out all the way down and give the throt­tle Vernier an ex­tra half twist in the flare to en­sure the en­gine is at idle. Re­sult? After a de­light­fully smooth touch­down I could have made the first turnoff with only min­i­mal brak­ing−a ground roll of 300m. Not bad for some­thing that can cruise at 235kt!

If it was good be­fore…

This is a hugely im­pres­sive ma­chine. I liked it when it was a Columbia, and all the changes that Cessna has im­ple­mented have made an ex­cel­lent air­craft even bet­ter. And, of course, now that it’s a Cessna prod­uct, the after-sales sup­port is su­pe­rior too, be­cause Tex­tron Avi­a­tion has ser­vice cen­tres all over the world.

Bear­ing in mind that a reader re­cently ex­pressed his dis­plea­sure at my acidic ap­praisal of Beagle’s prod­ucts, by now you’re prob­a­bly think­ing ‘has Dave lost his edge, or has Cessna bought him a good lunch?’ Well the an­swer is nei­ther−the TTX re­ally is that good. The park­ing brake could be bet­ter sited, and putting the head­set hold­ers in the roof wouldn’t be a bad idea, and there’s a large blank space on the star­board side of the panel that could eas­ily take a big glove box. And it’s not a grass strip ma­chine−but you al­ready knew that. If you’re fly­ing an air­craft that can cruise at 235kt and 25,000ft it’s un­likely that a grass strip will be your des­ti­na­tion−more that you’ll need some­where with Cus­toms fa­cil­i­ties!

I think it is the sheer size of the speed en­ve­lope that im­pressed me the most. As I said ear­lier, it’s not dif­fi­cult to make an aero­plane go fast, or go slow. The trick is to make it do both, and the Cessna TTX does just that.

Above: if you ever flip it, those gull­wing doors can be jet­ti­soned — an im­por­tant safety con­sid­er­a­tion Be­low: ad­vanced pro­pel­ler de­sign and Lo­presti pat­tern cowl in­takes shout aero­dy­namic ef­fi­ciency

Ac­cess to both the cabin and lug­gage com­part­ment is very good, gas struts hold­ing open the gull­wing doors se­curely The very nec­es­sary speed brakes Cuffs and stall strips: ev­i­dence of the fine tun­ing that has led to such benign low-speed han­dling

To­tal moder­nity: not only side­sticks but all-glass flight in­stru­ments, in­clud­ing the com­bi­na­tion standby. The Verniers are pretty much the only tra­di­tional thing in sight!

Cessna of­fers some typ­i­cally Amer­i­can trim colour schemes — we pre­fer this un­der­stated op­tion

Switches for the TKS anti-ic­ing sys­tem

Cessna has re­lo­cated some of the switchgear over­head

The model of sleek, speedy so­phis­ti­ca­tion — and far re­moved from GA’S all too com­mon sun­set tech­nol­ogy

As you would ex­pect, night op­er­a­tion is fully catered for

Thanks to the qual­ity of the in­stru­men­ta­tion and de­gree of au­to­ma­tion, the Ttx’s pilot can gen­uinely sit back and en­joy the view — and keep a good look­out in VMC!

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