Spe­cial Feature: F-35B Light­ning II

The supremely ca­pa­ble fifth-gen­er­a­tion jet fighter that out­does ev­ery­thing that went be­fore — and is the eas­i­est yet to fly

Pilot - - CONTENTS - Words Dave Un­win Photos Lock­heed Martin

There’s noth­ing fright­ning about pi­lot­ing Lock­heed Martin’s STOVL fighter, a tech­no­log­i­cal mas­ter­piece

Hov­er­ing slowly and pre­cisely along the taxi­way I couldn’t help but be re­minded of the time I flew a Har­rier TMK10. I’d thought that the Har­rier was an in­cred­i­ble fly­ing ma­chine, but the F-35 is some­thing else!

In fact, as soon as I set­tled in the Martin-baker Mk16 ejec­tion seat it was ap­par­ent that the F-35’s cock­pit is un­like that of any other fighter I’ve flown. Of course, I should qual­ify that ob­ser­va­tion by mak­ing it clear that although I’ve been lucky enough to fly about a dozen dif­fer­ent fight­ers and fighter-train­ers, pow­ered by pis­ton, tur­bo­prop and jet-en­gines, I am not a fighter pilot. How­ever, what I can of­fer is an im­pres­sion of a fly­ing ex­pe­ri­ence some of Pilot’s younger read­ers will even­tu­ally get to live for real, as the UK has or­dered 138 Light­ning IIS and many other west­ern nations will also buy them. In fact, for many coun­tries the F-35 will even­tu­ally be the only com­bat air­craft they op­er­ate, for− in­cred­i­ble as it may seem−the F-35 is in­tended to re­place a sig­nif­i­cant per­cent­age of the west­ern world’s tac­ti­cal air­craft, and

will cer­tainly be fly­ing well into the sec­ond half of the 21st Century!

It is also a sig­nif­i­cant aero­plane in that some of the bril­liant sys­tems in­cor­po­rated in the de­sign will even­tu­ally fil­ter down to air­lin­ers and busi­ness air­craft (think of how the B787 and many biz­jets have now adopted mil­i­tary-style Huds−head-up dis­plays). Finally, the F-35 may well be the last ever manned fighter...

So, what is the Light­ning II? It is a ‘fifth-gen­er­a­tion’ jet fighter that is pro­duced in three dis­tinct vari­ants: the con­ven­tional take­off and land­ing (CTOL) F-35A; the short take­off/ver­ti­cal land­ing (STOVL) F-35B and a car­rier vari­ant (CV), the F-35C. The UK is buy­ing the B model to equip both the RAF and Royal Navy. In­ter­est­ingly but un­sur­pris­ingly, the pro­gramme aim from the out­set was to max­imise com­mon­al­ity be­tween the three ver­sions, be­cause the costs in­curred in de­vel­op­ing a jet fighter of this lat­est gen­er­a­tion are colos­sal. In fact the to­tal life-cy­cle cost to the US Gov­ern­ment alone may well ex­ceed $1 tril­lion−much more

than any other mil­i­tary air­craft in his­tory. In­tended from its in­cep­tion to be an internatio­nal pro­gramme, this very ad­vanced air­craft re­lies on an in­cred­i­ble amount of soft­ware, with over eight mil­lion source lines of code. This is four times the amount used for the first of the fifth-gen­er­a­tion fight­ers, the F-22 Rap­tor, and re­flects just how pow­er­ful the F-35’s sys­tems and sen­sors are. They in­clude the Ac­tive Elec­tron­i­cally Scanned Ar­ray radar (AESA), elec­tro-op­ti­cal Dis­trib­uted Aper­ture Sys­tem (DAS) and an Elec­troOp­ti­cal Tar­get­ing Sys­tem (EOTS). For me at least, the most amaz­ing of these is the DAS, as its six sen­sors give a pilot un­lim­ited all-round day/night vi­sion. Con­se­quently, if the pilot looks down in the cock­pit, they ‘see’ in their hel­met dis­play what is un­der­neath the air­craft!

Be­fore sam­pling the sim­u­la­tor I took a leisurely walk round the full-scale mockup. At 15.4m in length and with a wing­span of 10.7m, it’s not as big as some fight­ers−but is quite tall, at 4.3m. In some re­spects it’s not en­tirely dis­sim­i­lar to a scaled down, sin­gle-en­gined F-22, although in oth­ers it’s rad­i­cally dif­fer­ent. One of the first things I no­tice is that although there are hard­points on the wings there are no py­lons, as all the weapons are car­ried in­ter­nally. This keeps the radar sig­na­ture down, en­sur­ing the air­craft is very stealthy. The wings, tail and un­der­car­riage all look con­ven­tional, although I know that the propul­sion sys­tem on the F-35B vari­ant is far from be­ing so. The en­gine is the Pratt & Whit­ney F135, the most pow­er­ful jet en­gine ever made for a fighter. Ad­di­tion­ally, the B model in­cor­po­rates the Rolls-royce ‘Lift­sys­tem’, and this com­bi­na­tion en­ables the air­craft to make a very short take­off, fly su­per­sonic and then land ver­ti­cally. I may well run out of su­perla­tives be­fore I fin­ish this ar­ti­cle, but the mo­tor re­ally is a me­chan­i­cal mar­vel, as is the re­mark­able Lift­sys­tem.

The F135 is a more pow­er­ful de­riv­a­tive of the Pratt & Whit­ney F119 en­gine, as used on the twin-en­gine F-22 Rap­tor. It can pro­duce up to 28,000lb (124.55kn) of dry thrust and an in­cred­i­ble 43,000lb (191.27kn) ‘wet’ (with af­ter­burner). To put this in con­text, the two Rolls-royce Avon en­gines of Bri­tain’s previous English Elec­tric Light­ning fighter each pro­duced 16,000lb wet (32,000lb to­tal thrust)

An in­ter­est­ing facet is that the F135’s two spools con­tra-ro­tate, which helps to shape the di­rec­tion of core air­flow as it tran­si­tions be­tween the high-pres­sure tur­bine (HPT) and low-pres­sure tur­bine (LPT) im­prov­ing the ef­fi­ciency of the en­gine and pos­si­bly re­duc­ing the num­ber of rows of static sta­tors and vanes. The LPT also turns the drive­shaft that pow­ers the Rolls-royce Lift­fan, lo­cated be­hind the cock­pit and ahead of the en­gine. This is a hor­i­zon­tally-mounted unit con­sist­ing of two con­tra-ro­tat­ing fans, one di­rectly above the other be­hind the cock­pit and cov­ered by a large door, which is only opened when the F-35B is hov­er­ing, per­form­ing a short take­off or tran­si­tion­ing be­tween hor­i­zon­tal and ver­ti­cal flight. Each fan is driven by a sep­a­rate bevel gear sys­tem con­tained in a com­mon gear­box to which power is trans­mit­ted by a drive­shaft which runs along the air­craft’s lon­gi­tu­di­nal axis. In the hover the drive­shaft de­liv­ers 28,000shp to the Lift­fan’s clutch-and­bevel-gear sys­tem so that the unit pro­vides down­ward thrust as a col­umn of cool air, along with a pil­lar of hot gas from the en­gine’s tailpipe, known as the Three­Bear­ing Swivel Mod­ule, or 3BSM. This re­mark­able piece of equip­ment con­sists of three ar­tic­u­lated sec­tions of ti­ta­nium

Sen­sors give the pilot un­lim­ited all-round day/night vi­sion... if the pilot looks down in the cock­pit they see what’s un­der­neath

In the hover the drive­shaft de­liv­ers 28,000shp to the Lift­fan’s clutch...

Right: dare we say it — a top glass cock­pit like no fighter pilot’s ‘office’ be­fore. Main features, from left to right, in­clude: the slid­ing throt­tle, shaped to act as a hand rest; un­der­car­riage lever (red light show­ing); an in­stru­ment panel given over en­tirely to the touch­screens of the PCD, the lower sec­tions of which are di­vided into ‘por­tals’ dis­play­ing pilot se­lected sys­tems in­for­ma­tion; and the side­stick (note the arm brace) which of­fers both con­ven­tional flight con­trol and up and down/side­ways con­trol in ver­ti­cal land­ing mode Be­low: air­craft near­est the cam­era are F-35BS, parked with Lift­fan and Aux­il­iary Air In­let Doors doors open

noz­zle cas­ing, each sec­tion con­nected to the oth­ers and driven by its own ring bear­ing. It can di­rect air through a 95-de­gree range, from five de­grees for­ward to hor­i­zon­tally aft. In­ter­est­ingly the ring bear­ing ac­tu­a­tors for the 3BSM are pow­ered by ‘fu­el­draulics’, some of the jet fuel be­ing bled off and pres­surised to 3,500psi, func­tion­ing as hy­draulic fluid to drive the servo-valve ac­tu­a­tors. The 3BSM can swivel fully from hor­i­zon­tal to ver­ti­cal in 2.5 sec­onds, com­pletely redi­rect­ing all the thrust down­wards. The fi­nal com­po­nent the ver­ti­cal lift/con­trol sys­tem is the pair of ‘Roll-posts’, vari­able-area noz­zles un­der­neath each wing that pro­vide roll con­trol in hover mode by di­rect­ing by­pass air from the en­gine through a pair of flap-type ti­ta­nium doors.

To­gether with the down­ward thrust pro­duced by the Lift­fan and the two wing-po­si­tioned ‘Roll-posts’, the F-35B can turn 15,700lb of dry tailpipe thrust into 39,400lb of thrust di­rected ver­ti­cally down­ward−in less than three sec­onds!

As the hover de­mands very high power, be­hind the Lift­fan’s big in­let door are a pair of Aux­il­iary Air In­let Doors (AAIDS) which pro­vide ad­di­tional air for the en­gine. Be­low the Lift­fan, the vari­able area vane box (VAVB) di­rects the cool air driven down­wards ver­ti­cally by the Lift­fan. The VAVB’S alu­minium lou­vered doors can be an­gled all the way from 45 de­grees back, through fully ver­ti­cal to five de­grees for­ward.

In good hands

I sit down in the cock­pit un­der the watch­ful eyes of−un­likely as it may sound−kenn and Bar­bie. Kenn Cooper and ex-f-18 driver Craig Dalle (call­sign Bar­bie)

know the sys­tems inside out and back-tofront, so I’m in good hands. The first thing that strikes me is just how clean the cock­pit and panel are. There are very few switches, knobs and levers, and even con­trols you’d think vi­tal for a STOVL air­craft, such as noz­zle and flap se­lec­tors are con­spic­u­ous by their ab­sence. All you re­ally have are the en­gine start switches, un­der­car­riage lever, emer­gency jet­ti­son but­ton, land­ing lights, park brake… and that’s pretty well it. Ev­ery­thing else is con­trolled ei­ther via the touch­screens or by voice con­trol. Another item miss­ing is the HUD. Nev­er­the­less, F-35 pi­lots are pre­sented with a truly phe­nom­e­nal amount of in­for­ma­tion, much of which is dis­played in their hel­met vi­sors. In fact, and un­sur­pris­ingly, this air­craft’s an­cil­lar­ies (such as the ejec­tion seat and pilot’s hel­met) are just as so­phis­ti­cated as the aero­plane it­self.

The cock­pit is dom­i­nated by an L-3 panoramic cock­pit dis­play (PCD) with touch­screen con­trol and ac­tive ma­trix liq­uid crys­tal dis­plays. The PCD features dual 250 x 200mm screens, mounted on ei­ther side of a cen­trally lo­cated 500 x 200mm dis­play. The big screen has a 2560 x 1024 pixel dis­play while the smaller two are 1280 x 1024. They’re ex­tremely clear and easy to read. The upper part of the large screen is pri­mar­ily for sub-sys­tem in­for­ma­tion, such as en­gine gauges, fuel quan­tity and un­der­car­riage sta­tus, cau­tion and warn­ing sys­tems, plus au­topi­lot/auto throt­tle and nav­i­ga­tion in­for­ma­tion, and lots more. Tac­ti­cal in­for­ma­tion is dis­played on the lower part of the screen and is split into four seg­ments called ‘por­tals’. The pilot can place any­thing any­where and even change the size of the por­tals.

Sym­bol­ogy at the bot­tom left of the dis­play on the F-35B’S PCD shows the sta­tus of the 3BSM and Lift­fan. In the cen­tre of the con­sole is a bat­tery-pow­ered standby flight dis­play. How­ever, most of the in­for­ma­tion is dis­played within the pilot’s vi­sor, while sit­u­a­tional aware­ness is en­hanced by a voice com­mand sys­tem that is­sues di­rec­tional threat warn­ing mes­sages.

On the right side of the cock­pit is the side­stick, which as well as operating the ailerons and el­e­va­tor con­ven­tion­ally also en­ables the pilot of the STOVL vari­ant to hover the aero­plane. The throt­tle is on the left and moves through a lin­ear slide rather than a ro­tary arc. Both side­stick and throt­tle are lib­er­ally stud­ded with switches and but­tons and the HOTAS ‘switchol­ogy’ is pretty com­plex, although in­ter­est­ingly there isn’t a trim but­ton.

Start­ing the en­gine is easy−just turn on the IPP (a sort of APU) then set the en­gine switch to run and it… well; runs. Taxy­ing is very straight­for­ward: the nose­wheel steers through the rud­der and for tighter turns you can ad­just the steer­ing gain. The field out of view out of the for­ward hinged canopy is good, although as long as the syn­thetic vi­sion Dis­trib­uted Aper­ture Sys­tem is func­tion­ing cor­rectly the wind­screen could be opaque. Out on the run­way of the sim­u­lated Nel­lis AFB, I run through the pre-take­off checks and search in vain for the flap se­lec­tor, un­til Bar­bie re­minds me that the flaps are purely au­to­matic. Take off is sim­ple−line up, full ‘dry’ power then into af­ter­burner. The ac­cel­er­a­tion is phe­nom­e­nal, ro­tate at 150kt after a very brief ground roll then re­tract the un­der­car­riage as quickly as pos­si­ble! The speed just keeps building and in no time I’m flash­ing across the vir­tual desert at M0.9 and 100ft−what a rush it would be to do this for real! Clever sym­bol­ogy shows when your vec­tor will co­in­cide with the ground−a use­ful safety fac­tor.

After a very rapid climb to 25,000ft I try some slow flight, but the com­puter won’t let a full aero­dy­namic stall de­velop; in­stead the sink rate sim­ply in­creases. I add power un­til the sink rate is ar­rested at 120kt, then Kenn says “you can loop it from there−just go to full af­ter­burner and pitch up.” I can scarcely be­lieve its pos­si­ble but do as I’m told−and it works as ad­ver­tised. The power and con­trol avail­able is in­cred­i­ble, yet de­spite ev­ery­thing the Light­ning is just so easy to fly. The roll rate is pretty rapid, but the over­whelm­ing char­ac­ter­is­tic is just how pre­cise con­trol feels around all three axes. As I’m more in­ter­ested in fly­ing than fight­ing in the sim, I don’t have time to ex­am­ine the myr­iad weapons avail­able, but can’t re­sist drop­ping a pair of 2,000 pounders on an ‘en­emy building’. As with every other as­pect of the F-35 (with the pos­si­ble ex­cep­tion of the HOTAS, which clearly takes some learning) tar­get cue­ing, aim­ing and bomb re­lease are all per­fectly straight­for­ward. I don’t miss.

Head­ing back to the vir­tual Nel­lis at M0.9 takes no time at all, but as the field comes into view I re­alise that although the throt­tle’s a long way back, the F-35 isn’t de­cel­er­at­ing as much as I’d ex­pected. Sens­ing my surprise Bar­bie ex­plains that “it re­ally doesn’t like to slow down” so I thumb the air­brakes out to help get the speed be­low the 300kt VLO. Hav­ing se­lected the un­der­car­riage down I look in­stinc­tively for the flap lever, then re­mem­ber there isn’t one!

As Nel­lis has an elevation of about 1,900ft, I dis­re­gard the pres­sure al­time­ter and use the Radalt in­stead. Hav­ing flown a rea­son­able cir­cuit with the throt­tle in man­ual and a Vref of 150kt to a touch and go, I turn down­wind at 250kt, re-se­lect ‘gear down’, punch the ‘con­vert’ but­ton and turn back to­wards the run­way. (You can press the con­vert but­ton at any speed, but the com­puter sim­ply won’t en­gage the Lift­fan above 250.) Sym­bols on the PCD show that the F-35 is ready to hover, so I sim­ply press the speed com­mand but­ton on the throt­tle ‘in’.

Air speed con­trolled by a but­ton

Air speed is now con­trolled by click­ing the speed com­mand but­ton up and down to change the se­lected speed in the

com­mand box and you sim­ply ig­nore the throt­tle and use only the stick: push for­ward for down, back for up, left to shift left and right to shift right−it re­ally is that sim­ple. Bar­bie rec­om­mends us­ing sixty knots ini­tially, and then slowly re­duc­ing as the run­way’s thresh­old is ap­proached. He also gen­tly re­minds me to stay off the rud­der, un­less I want to make a ‘pedal turn’ about the ver­ti­cal axis. Once over the run­way num­bers I set ‘zero’ in the speed com­mand box.

Although its been about fiften years, I re­mem­ber vividly that as the Har­rier tran­si­tioned to purely jet-borne flight it all felt a lit­tle ‘knife-edge’. As it slowed to a stop in the sky, some­what im­prob­a­bly poised on four col­umns of screech­ing, scorch­ing air, I was very aware that the pi­o­neer­ing Bri­tish VTOL jet could suf­fer di­ver­gent di­rec­tional sta­bil­ity if an in­take was blanked by yaw while in the hover, and could suf­fer the same thing in the low speed range when tran­si­tion­ing to and from wing-borne flight. In fact, this sit­u­a­tion was so se­ri­ous (it’s a sort of aerial ground loop that al­most al­ways ends with an ac­ci­dent) that Har­ri­ers were fit­ted with a de­vice that senses if yaw is start­ing to de­velop and shakes the rel­e­vant rud­der pedal as a cue for the pilot.

The Har­rier was a prod­uct of a very dif­fer­ent tech­no­log­i­cal time−and only the very best pi­lots were streamed to fly it. Well, the F-35 is noth­ing like that. There are no is­sues with di­ver­gent di­rec­tional sta­bil­ity or a pedal-shaker. In fact it re­ally does seem ex­tremely easy to fly. Of course, hav­ing never flown a real F-35 I can’t com­ment on the fi­delity of the sim­u­la­tor, but even if a real one is two or even three times harder than the sim, it’s still clearly pretty straight­for­ward to fly− which is how it should be. In­deed, along with all the other tasks that a 21st century fighter pilot must per­form, sim­ply fly­ing the air­craft is prob­a­bly the eas­i­est bit!

In fact the F-35 feels rock-solid and very sta­ble as I ease the stick for­ward and sink onto the run­way. Em­bold­ened by my suc­cess I fly a STOL take­off (full af­ter­burner, stick back at sixty knots)

Use only the stick: push for­ward for down, back for up, left to shift left and right to shift right — it re­ally is that sim­ple

then re­turn for some more ad­vanced hov­er­ing, in­clud­ing some brisk pedal turns, be­fore descend­ing to twenty feet and hover-taxy­ing along the myr­iad taxi­ways at ten knots. I doubt you’d do this in real life as it wouldn’t do the tar­mac any favours at all (I saw a real F-35 hover at Farn­bor­ough the day after my sim flight, and the amount of en­ergy be­ing di­rected down­wards was ex­tra­or­di­nary), but it is good fun, while looking straight down through the floor at what is un­der­neath the air­craft is sim­ply sur­real. As an ex­per­i­ment I push the stick for­ward sharply to try and pro­duce a heavy land­ing, but the com­puter sim­ply won’t al­low touch­downs with a sink rate above 750fpm.

As the fuel state is now quite low I try a ver­ti­cal take­off and quickly pull the stick back−it goes up like a rocket pow­ered lift. One more ver­ti­cal land­ing and its ir­refutable−lock­heed Martin has done an amaz­ing job in mak­ing an in­cred­i­bly com­plex air­craft re­mark­ably un­com­pli­cated.

But what a ma­chine! STOVL, stealthy and su­per­sonic, its ‘fused’ sen­sor sys­tem and stealth de­sign mean the F-35B pilot sees ev­ery­thing, but no one sees the F-35. To para­phrase (I think) Abra­ham Lin­coln, if you’re the kind of fighter pilot that likes this sort of thing, then this is very much the sort of thing that you’ll like!

PH OT O: JA M IE HU NT ER / AV IA CO M

To min­imise the radar sig­na­ture, mak­ing the air­craft as stealthy as pos­si­ble, all weapons are car­ried in­ter­nally. This is the F-35C NON-STOVL car­rier ver­sion, equipped with a tail­hook for ar­rested land­ings

While the Har­rier was famed for tak­ing the drama out of deck land­ings, the F-35B makes them easy

Bal­anc­ing the thrust of the en­gine-driven Lift­fan in ver­ti­cal flight, the seg­mented tailpipe curves to de­flect jet ex­haust down­wards

Even flap de­ploy­ment is au­to­mated — a feature we might like to see in fu­ture light air­craft

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