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The McGrawmiddotHi1 Companies ~ wwwAviationWeekcombca MARCH 2010

s Be Commercial

Taking Control by Wire Reprinted from the March 2010

issue of Business amp Commercial Aviation

Copyright copy2010 by The McGraw-Hill Companies This reprint implies no endorsement either tacit or expressed of any company product service or investment opportunity

Taking Control by Wire

The Falcon 7Xs pioneering fly-by-wire system is the future here today

By Roomiddot Det1vilermiddot

Abou t t h nc yc rs ago I flew a Falco n ltJOOEX from Sa n Frl nltiscu LO Columbus Ohio Arriving btc lt Lme Av iation

t he good folk s o f the nig h t stlff qu ick ly and cornpctently flushed and fueled the thne-holcr

I ns idc t he F BO th ere wa s a sihmiddote rshyhlircd gentlen11n wi th 1 Segwly o ne o f t hose t wo-wheeled transporters upo n wh ic h the rider merely sta nds ho lds t he handlebars leans in t he direction towa rd which he wl nts to t rave l a nd moves o ut I low hHd could this be to maste r I asked

2 ltllincjf ComJJitbullrrialltia tion I March 2010

for a turn and wIS gra nted a ride down the lung hall way

I d idn t do we ll It seemed to m e a hard machine to contro l sm ooth ly and I wiggled and tort ured my way about hlifwty dow n the hall and man aged to t ur n it around without damaging t he doors of various offices or knocking a ny pictures off t he wal l Vhc n I got back to t he front the o ld man was sluki ng hi s head

Qu it trying to balance thi s t h ing lt ba la nces itself Jus t sta nd on it t h ink about which d irectio n you wa nt to t ravel and go Its t hlt simple he said M y fiveshyyea r-old g ra nddaughter does nt have the proble m s that a pilot docs because s he

doesn t t ry and cont ro l it P retend it has four whee ls and just stand o n it

tVith t hat advice it was instan tly a lot of fun and easy to ma neuve r in precisely sm a ll radii Keep this story in mind T d idn t reali ze it at t he ti me but it was a breakthrough that I wou ld use later

We Are FBW At Dassndt Falcon jets big an nua l breakfast

at the N BAA Convention several years before

the above incidem the inventor of the Segway

tra nspo rter Dean Kamen spoke A quietshy

spoken gen ius in my estimation Ilt amens nor

jusr smarr bu t he has the abi lit y to make his

ge ni us understandable to the rest o f us l ies

working on numerous pro jects includi ng water

wwwAviationWeekcom bca

Taking Control by Wire

The Falcon 7Xs pioneering fly-by-wire system is the future here today

By Roomiddot Det1vilermiddot

Abou t t h nc yc rs ago I flew a Falco n ltJOOEX from Sa n Frl nltiscu LO Columbus Ohio Arriving btc lt Lme Av iation

t he good folk s o f the nig h t stlff qu ick ly and cornpctently flushed and fueled the thne-holcr

I ns idc t he F BO th ere wa s a sihmiddote rshyhlircd gentlen11n wi th 1 Segwly o ne o f t hose t wo-wheeled transporters upo n wh ic h the rider merely sta nds ho lds t he handlebars leans in t he direction towa rd which he wl nts to t rave l a nd moves o ut I low hHd could this be to maste r I asked

2 ltllincjf ComJJitbullrrialltia tion I March 2010

for a turn and wIS gra nted a ride down the lung hall way

I d idn t do we ll It seemed to m e a hard machine to contro l sm ooth ly and I wiggled and tort ured my way about hlifwty dow n the hall and man aged to t ur n it around without damaging t he doors of various offices or knocking a ny pictures off t he wal l Vhc n I got back to t he front the o ld man was sluki ng hi s head

Qu it trying to balance thi s t h ing lt ba la nces itself Jus t sta nd on it t h ink about which d irectio n you wa nt to t ravel and go Its t hlt simple he said M y fiveshyyea r-old g ra nddaughter does nt have the proble m s that a pilot docs because s he

doesn t t ry and cont ro l it P retend it has four whee ls and just stand o n it

tVith t hat advice it was instan tly a lot of fun and easy to ma neuve r in precisely sm a ll radii Keep this story in mind T d idn t reali ze it at t he ti me but it was a breakthrough that I wou ld use later

We Are FBW At Dassndt Falcon jets big an nua l breakfast

at the N BAA Convention several years before

the above incidem the inventor of the Segway

tra nspo rter Dean Kamen spoke A quietshy

spoken gen ius in my estimation Ilt amens nor

jusr smarr bu t he has the abi lit y to make his

ge ni us understandable to the rest o f us l ies

working on numerous pro jects includi ng water

wwwAviationWeekcom bca

p u r i fic ation b ut at th e t ime Dassau l t wts

tryi ng to get the arrendees more com fo r table

wi t h t h e f ly-by- wire ( FBW) co ncept a nd

Kamen was the perfec t perso n fo r t he task

At o ne poi nt he held up a htnd a nd wiggled

h is fingers Fly-by-wi re he said Electrical

impu lses from Ill~ brai n travel down my arm

to recep tors where rhat electrical impul se is

c ht n ged into a mecha n ical m otion T h ats

ny-hy-wirc Br gos h he wa s ri g h r middotc do n t hamiddote

c~ b le s run nin g up t he le ngth of o u r arms

a nd con nected to a tu rn buckle on the side of

ou r n eck Ve don t set a line of m ach inery

in moti o n jus t to mobulle a fi nger Rather we

think t he m ovemen t electrictlly and it

htppens Ve are fl~middot-b~middot-wi re

Dasstu lt got irs mo nevs wo rth out of that

pluc of scrambled eggs

In a commiddotemional fl ight conrrol S)Stem the

pi lot moves a wheel or st ick and rudder pedals

tO input com mands ro flight controls Those

comma nds g o mecha n ically into tension ed

cables that move over numerous re lty pul le~middot s

be ll c rtnks tnd a rtificial fee l i nducers T h is

in p ut c middotc mually trrimiddotcs ei t he r di rec tl y at

a fl igh t cont rol or in boosted s~middotstem s at a

hydr111lic actuator where it moves middota lvcs that

port flu id ro rhe pi ston of t hat actuator and

m o ve the fligh t control con nected ro that

piston

Pilots arc responsible for cause and effect in

controls P ull roo hard at roo high an tirspccd

and you can overs tress the airpbne or pu ll roo

ha rd at too low a speed and you ca n sta ll it

Thus the pi lot is connected mechmically to the

fl ight controls ofthe airplane Regardless oft he

speed of the tirpllnc or outcome ofth~ input

the controls will respond to the pi lor the on ~middot

brain in the operation

Ask someone about the difference hctw~en

fly-bv-wire 111d convenrion tl control s ~middots tcms

and the~middot l llikd~middot respond middotThe controls arc

commanded by elect r ical impu lses intead of

cables Thats true bur the rc 1l difference i n

an FB system is the computers t hat receimiddote

control in puts a nd d irect control n1mbullcn1ent

ire is just th~ med ium for transpo rting those

commands T he Falcon 7X h as t hree mtin

computers thar protect aga inst nverspecd stdl

and overstress provide stlbi litv augmentation

auto-trim the airpla ne consider pilot in puts

to rhe fligh t cont ro ls and o pt imi ze con fig ushy

rat ion T hree secondary fl ight computers htck

up rhe main compurers

l n the god-awful event t hat al l six of these

d ig it al compute r s fai l t here is a n an a log

computer t h1r comrols the two fl ight spoi lers

w it h r udde r p eda l di s pl acemen t t n d th e

t r innuahlc hor izonta l s tabi lizer wi th th e pitch

t r im sw itch

You dont ltnd the 1 i rpltne in t h is t nd o g

computer manual reversion Yo u keep it r ight

side up whi le ~middotou reset the digita l computers

T he odds of that h 1ppeni n g arc 10 to some

incred ibly negative expo nent but its nice to

know you never reach a po int where ~middotou have

no control An engineer rold me that

I think of these compute r 1 aids not

replacemem~ fo r my h rtin I li ke tO re llte 1

s tor y ahout 1 cardiac s urgeo n wh o wa s t

ptssengcr on 1 Globd Exp ress I w1~ flying

l ie was a private pilot with his own light twin

( Dont ~middotoulove the way these g uys become the

expe rt in the back telling al l the folks middothH

~middotoure doi ng up front tnd wh~middot ) cverthcles

he made t he comment It s 1ll done with

comput~r thce dIIS Bcliemiddote me I know

I asked him if he ope rated at one of those

ho~p ital gt thlt ued comput er s fo r different

surgeries

hy yes It s the b test state of the science

Thn me111s I could be 1 hea rt su rgeon then

right ell not exacrlv he said condescendingly

The do c tor s ti l l ha s to k n ow wh1t th e

computers doi ng ro hi s pat ient and know and

b e pro ficient in th e intricac ie s of whnever

p roced ure is be ing perfor med li es st il l the

surgeon

l~xactl y

I n the i X com puters judge what I wtn t

to do wit h th e ai rpltne T hey guard agt inst

my gett in g too s low or too fts t I donr htvc

to tickle the stt ll to get max performt nce in

1 wi nd shear or terrtin avoida me tnan cuver

I just pull as ha rd as I c1n i n the di rccrion I

w111t to go t nd I m obtt in ing the llltx i mu m

p erforman ce I ct n ge t towtrd m y gotl I

dont htvc to crosscheck al l my att it udes with

airspeed I should but if I don t I ca n neither

s tnl l nor pu l l t he wings n ff I don t h tve to

r emem be r to retr tct t he fli g ht sp o i lers or

ex tend o r retract certa in high - lift devices a t

rerms o f the amount of force they apply ro the FBW offers a chance to make a big change In the way the pilot Interfaces with the control of the airplane

There Is a maintenance and avionics Interface computer that monitors t he performance of all the components and determines how well they are

cri ticli rimes My thi nki ng is backed up by t computer that is programmed with pre-set limits

From Input to Control Movement

l n D asstults FB11 svstem cont rol inputs first go to Flight 6ata Concentrators These electronical ly gather the wants and wishes of the pi lots t h rough thci r inputs to the side-stick control lers and the rudder pedals If the autopi lot is o n the concenshytrators gather the flight dirccrors wants and wishes

When I say they gather t he input Im using pilot jargon not engineering terminolog~middot middot For instance there are 20 ponnriometcrs in each si d e - sr ick controller that electronica ll y measure t he cont ro llers d irection rate and length of time ofdisplacement This is an extremely soph ist icated system Gathering is clone through electrical impulses fed tO all s ix fl ight control computers

To allow t he 1irplane tO respond to the com mands appropriately t he computers must first ascertain the airplanes current per fonn1nce

l n convention li tire raft t he pil ot dete r m i nes a n aircrafts cone i tion by gathering information gathered from various sources including pitot pressure stat ic p ressure s l ip a nd tem pe rature The pi lot reads this in forma t ion as it is displayed on instruments in the cockpit

I n an FBV system these air data inputs have to he t ransmitted electronictl ly ro t he compu ter On the X the clcctr ica l i n pu ts come fro m four A D S (a i r clara system) smart probes- numbcr one to the pilot num bcr two to the copilot

wwwAviationWeekcomjbca

number fou r tO the backup airspeed t nd altitude in dicato r tnd numbe r three backs up any o f the other three positions A reversionary panel allows the pilot to move ADS one two or th ree to e ither the pilots or copilots side These A O S smart probes t re information gatherers of the computerized FBsystem Theyre important

Other computer inpu ts come from the I RScs thc A I I RScs the fbtps whee l speed and VO V sensor

Output from the flight control computers goes to four Actuator Control and Moni to ring Un its The pu r pose o f t hese is to rece ive the inputs from the operating Fl ight Control Computers and send the electri ca l commands to the des i red fl ig h t control actuato rs Later in the proccss t hese sa nt e components monitor flight control movement The e lect ro-hydraulic actuators ports nrc opened in respo nse to clcctr ictl signals telling them how much tnd how ftst ro operate

There is also amaintcntncc and amiddotion ics interface computer thtt mon iro rs the pe r forma ncc of a II the components mel dete rm ines how well they t re which is to say how many of the conponents that should be operating arc doing so

Why So Many Computers There are three sets of fli ght control laws at work in the Fa lcon 7Xs FBV system The three main dual lane (lane A cont rols lane B monito rs) computcrs a rc domintnt T he secondary compu ters t1ke control onlv whe n a ll three of the main computers ~ave fai led

Vith all three of t he main computers in

control the svstern is in normlt11 moclc A ll t he p rot~ctions of the syste m are available If one of the main computers is lost the pi lot may still maintain the normal laws profiles If two of the main com puters are los t the system goes to

bulltl tcrnatc laws which means that some of t he protections 1 re u nwt ilthlc 1fa I three of the main computers fail the pilot is in direct mode basically fl ying 1n airp lan e w ith the seco ncltry f lig ht control computers wh ich a re s ingleshychannel design with no monitoring of t he demanded inputs for compliance with the protections tlhcn in d irect mode t ct relcss pilot can overstress or sta ll the airp lane- TTcll -o- as has tlways been possiblc with cahlc cont ro ls

To ensure the re is a lways el ectr i cit~ to r u n through t he wires t he systltm can be control kd with just one of th ree generators functioning If no generators are working the system still em be elecshytrifi ed through batteries or inputs from a PMA on e ither t he number one or two engine [fall that fa ils t he re is 1 RAT for powcr You must have some h~rdrau li cs

Why the Side Stick FBvV offers 1 chtncc to mtkc 1 big chtnge in t he wty the pi lot interfaces with the control of the airplane hen r first saw Fl3V technology it wts in the F-16 Although r neve r got the opportun ity to fl y that mach ine I ctnnor imagine tny setup more natural to a pilot A reclining seH a throttle in one hand sti ck in the othcr the p il o t s shoulders relaxed 1nd 1rn1s s u ppo rted i n s ide rcsts to he lp accom modate thc g forces Perfeet

] ~middoter since sceing that first F-1 6 it has been my opinion that there can be no bctter fly-hy-w irc setup than the w1y Gcncra l D1rnam ics or D tsswlt or Airbus have dcsigned theirs You cant improve on the natural position of the hands and arms with side-stick controllers To take thi s ma rvelous technolog-y and tttach it to t yoke or a sr ick bet~een th e p ilots legs is like putting a three-speed shifter on the steering wheel column of a new Corvette A word of adv ice to tny 111lt11111shy

factu rcr plann ing on improv ing FBVV The center voke or the center control stick is dead lobullc on

That of course is my o pin ion

Lets Fly It Any pilot who has flown a fighte r a hel ishycopter or even a Cub middotith a control stick knows not to grtb the thing Rather you put your right wrist on you r right leg and couch the stick Vhcn karning to fly formation or to refue l in flight the p roxim ity of the other lt1ircrt ft t ypica ll y

lmmiddotilltl amp ComIIITIilll middotvi11tio11 J March 2010 4

There Is a maintenance and avionics Interface computer that monitors t he performance of all the components and determines how well they are

cri ticli rimes My thi nki ng is backed up by t computer that is programmed with pre-set limits

From Input to Control Movement

l n D asstults FB11 svstem cont rol inputs first go to Flight 6ata Concentrators These electronical ly gather the wants and wishes of the pi lots t h rough thci r inputs to the side-stick control lers and the rudder pedals If the autopi lot is o n the concenshytrators gather the flight dirccrors wants and wishes

When I say they gather t he input Im using pilot jargon not engineering terminolog~middot middot For instance there are 20 ponnriometcrs in each si d e - sr ick controller that electronica ll y measure t he cont ro llers d irection rate and length of time ofdisplacement This is an extremely soph ist icated system Gathering is clone through electrical impulses fed tO all s ix fl ight control computers

To allow t he 1irplane tO respond to the com mands appropriately t he computers must first ascertain the airplanes current per fonn1nce

l n convention li tire raft t he pil ot dete r m i nes a n aircrafts cone i tion by gathering information gathered from various sources including pitot pressure stat ic p ressure s l ip a nd tem pe rature The pi lot reads this in forma t ion as it is displayed on instruments in the cockpit

I n an FBV system these air data inputs have to he t ransmitted electronictl ly ro t he compu ter On the X the clcctr ica l i n pu ts come fro m four A D S (a i r clara system) smart probes- numbcr one to the pilot num bcr two to the copilot

wwwAviationWeekcomjbca

number fou r tO the backup airspeed t nd altitude in dicato r tnd numbe r three backs up any o f the other three positions A reversionary panel allows the pilot to move ADS one two or th ree to e ither the pilots or copilots side These A O S smart probes t re information gatherers of the computerized FBsystem Theyre important

Other computer inpu ts come from the I RScs thc A I I RScs the fbtps whee l speed and VO V sensor

Output from the flight control computers goes to four Actuator Control and Moni to ring Un its The pu r pose o f t hese is to rece ive the inputs from the operating Fl ight Control Computers and send the electri ca l commands to the des i red fl ig h t control actuato rs Later in the proccss t hese sa nt e components monitor flight control movement The e lect ro-hydraulic actuators ports nrc opened in respo nse to clcctr ictl signals telling them how much tnd how ftst ro operate

There is also amaintcntncc and amiddotion ics interface computer thtt mon iro rs the pe r forma ncc of a II the components mel dete rm ines how well they t re which is to say how many of the conponents that should be operating arc doing so

Why So Many Computers There are three sets of fli ght control laws at work in the Fa lcon 7Xs FBV system The three main dual lane (lane A cont rols lane B monito rs) computcrs a rc domintnt T he secondary compu ters t1ke control onlv whe n a ll three of the main computers ~ave fai led

Vith all three of t he main computers in

control the svstern is in normlt11 moclc A ll t he p rot~ctions of the syste m are available If one of the main computers is lost the pi lot may still maintain the normal laws profiles If two of the main com puters are los t the system goes to

bulltl tcrnatc laws which means that some of t he protections 1 re u nwt ilthlc 1fa I three of the main computers fail the pilot is in direct mode basically fl ying 1n airp lan e w ith the seco ncltry f lig ht control computers wh ich a re s ingleshychannel design with no monitoring of t he demanded inputs for compliance with the protections tlhcn in d irect mode t ct relcss pilot can overstress or sta ll the airp lane- TTcll -o- as has tlways been possiblc with cahlc cont ro ls

To ensure the re is a lways el ectr i cit~ to r u n through t he wires t he systltm can be control kd with just one of th ree generators functioning If no generators are working the system still em be elecshytrifi ed through batteries or inputs from a PMA on e ither t he number one or two engine [fall that fa ils t he re is 1 RAT for powcr You must have some h~rdrau li cs

Why the Side Stick FBvV offers 1 chtncc to mtkc 1 big chtnge in t he wty the pi lot interfaces with the control of the airplane hen r first saw Fl3V technology it wts in the F-16 Although r neve r got the opportun ity to fl y that mach ine I ctnnor imagine tny setup more natural to a pilot A reclining seH a throttle in one hand sti ck in the othcr the p il o t s shoulders relaxed 1nd 1rn1s s u ppo rted i n s ide rcsts to he lp accom modate thc g forces Perfeet

] ~middoter since sceing that first F-1 6 it has been my opinion that there can be no bctter fly-hy-w irc setup than the w1y Gcncra l D1rnam ics or D tsswlt or Airbus have dcsigned theirs You cant improve on the natural position of the hands and arms with side-stick controllers To take thi s ma rvelous technolog-y and tttach it to t yoke or a sr ick bet~een th e p ilots legs is like putting a three-speed shifter on the steering wheel column of a new Corvette A word of adv ice to tny 111lt11111shy

factu rcr plann ing on improv ing FBVV The center voke or the center control stick is dead lobullc on

That of course is my o pin ion

Lets Fly It Any pilot who has flown a fighte r a hel ishycopter or even a Cub middotith a control stick knows not to grtb the thing Rather you put your right wrist on you r right leg and couch the stick Vhcn karning to fly formation or to refue l in flight the p roxim ity of the other lt1ircrt ft t ypica ll y

lmmiddotilltl amp ComIIITIilll middotvi11tio11 J March 2010 4

~---- ------ -------------

Da ta CollectiOn

t I

~

CalculatiOn of Control Surfaoe r - Command Choice of FCC Computer Tranomioslon to Actuatoro t - bull bull bull bullbullJ

Monitoring orActuators

I I I Data Exchange

wTth Aviooics -------------- 1-------------------- I I

______tI ____ __ i middot ~ ~-- ----------

causes students to overcontrol because t hey re ho ld in g the stick too ti g ht A crutch that often helps students e1se up is to place a pencil in thei r hand and explain If you feel th1t pencil ~-oure holding the stick too right

l n for ma t io n fl ying precise fo re and aft movements of the stick arc made with the wrist Left and right movements arc usuallv m ade wi th t he r humb in back a nd two fingers touching the front of the st ick The extension-retraction o f those two fingers is ro ll control in formation T he familiar advice is Put it where you wa nt it and trim off the press ure The tr im button o n most h igh-perfo rmance airc raft is loc1red on the to p of the st ick The rhumb is used to trim o ff forward pressures being held by the two f ingers or rea r wa rei prcssu res he ld by the crook between the thumb and two fingers

Obv ious ly you need not hwc f lown fi ghters to eas ily maneuver the 7X but t h1t experience gave me a good point of re ference to sta rt my F BvV indoctrination Nork the stick with the thumb and tips

o r tWO o r three finge rs Put the airplane where you want it and just w1it lt1secondlt trims off the pressure ro stay t here

The 7X will coordina te my turns lt111d nim off the pressu res caused b~- m y ch an ges to t he flight path o r speed Tr is a fli ght path stable airplane Remember t hat fli ght path is the track the center o f g ravity of the airplane makes through the air It is not pitch

In addi tion tO rhe 7Xs adjustable pilot scat and pedals theres a soft pad behind t he side stick that adjusts to reli eve 1ny tension from your hand

Take off and ro tate t he a ir plane into th e fli g ht director c ue G ear up hold 1ttirude for 1 second and then let go The ai rplane stays right the re 1Vhen you get to -+00 feet c lean up lowe r t he flight path and pull the power back to clim b If t he depa rtu re calls fo r a tu rn roll into it neutralize t he aileron pressu res hold fo r a second a nd let go The airplane st1vs there On final you ro ll our a im t he airplane at the end of t he runway set the power and relax it stays a imed at t he e nd

of the ru nway Only wind can change its destination

How Not to Fly a Control-by-Wire Airplane

Since t he 7X maintain s fl ight path its attitude ma y change in t he doing espeshyc ia ll y if yo ure hand fl ying the airplan e w it h the auto throttles off Th is ca n require some mental adjust men t espeshycia lly among experienced pilots

vVeve all been taught that when fl ying at t itud e in s t rumen t s a ll ch an ges in ai rpla ne motion are made wit h reference to attitude We dont push forwa rd on t he stick while looking at the a lt ime ter vVe reference the attitude ind icator and lower t he pitch to correct alt it ude excu rsio ns iVe r e fe rence t he attitude ind icator when adjusting power and aga in when correct ing c hanges in o ur fl ig ht path caused by the changes in power

Bur again to ma i nta in its f l ig h t path the 7X may a utOma tica lly change att itude- sl ightl y but perce pt ibly The pi lot woul d also have changed t he attitude to accompl ish what FB N d id automatically bur since t he cha nge was uncomma nded the pilor might reflexively return the a ircraft to irs fo rmer ltlttitude At t hat poi nt t he pilo t wou ld c ross shycheck per form ance instruments only to d iscover theyre moving because hes now disrupted t he attitude needed to mainr1in the stable fli ght path he requested in the first place H e re-corrcc ts and t he osci lshylations continue

In effect the pilot is trying to balance the Segway

D o n t fig ht the fl y-by-wi re L et it maintain t he airplanes fli ght pat h The 7X cannot be f lown the same as any other a i rplane bur once you le t it mainta in fl ight path and change on ly performance pi lot ing it becomes as easy as rid ing a Segway

The Falcon 7X f ly-by-wi re system derived from years o f Dassau lt f ighte r experience is a pioneering tech nology fo r business av iation T hat others will follow is a given since thi s is t he way that future a irpla nes will be controlled There is no going back to non-compute r monitored flight contro ls at t hi s stage Fl y-byshycomputer is here to stay bull

Reprinted from Business amp Commercial Aviation March 2010 copyright by The McGraw-Hill Companies Incwith all rights reserved This reprint implies no endorsement either tacit or expressed of any company product service or investment opportunity

1-27750832 Reprinted by The YGS Group 7175059701 For more information visit IWIWtheYGSgroupcomlreprints