Givrajul La Motoarele Cu Piston CAA

8/10/2019 Givrajul La Motoarele Cu Piston CAA

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GENERAL AVIATION SAFETY SENSE

14A

PISTON ENGINE ICING


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1 INTRODUCTION

a Altho ug h t h is lea f le t i s ma inlya d d r e sse d t o a e r o p la n e o p e r a t i o n s,

much o f it s con t en t a pplies equa lly

to pis ton-engined hel icopters and

gyroplanes .

b Pisto n eng ine ind uct ion syste micing , com mon ly re fer red to a sca rburet to r ic ing , ca n o ccur even on

warm days, particularly if they arehumid. It can be so severe t ha t un lesscorrect a ct ion i s t a ken the eng inema y sto p (espec ia lly a t low pow er

se t t ing s dur ing descen t , approa ch o r

dur ing h e l icopt er au to ro ta t ion).

c Every yea r the re a re severa l

a cciden t s in t he UK w here eng ineind uct ion syste m icing ma y ha ve

b e e n a f a ct o r. U n f o r t u n a t e ly t h e

evide nce rap id ly d isa ppea rs.

d So me a ircra f t /en g inecom bina t ions a re more prone t o

icing tha n o thers and th i s should be

bo rne in mind w hen f l y ing d i f fe ren t

a ir cra f t t ypes .

2 TYPES OF ICING

There a re th ree ma in types of

ind uct ion syste m icing :

a Carbu ret t or Icing

The mo st comm on , ea r liest t o show ,

a nd th e m ost ser iou s, i s carb icing

ca used by the sudd en tempe ra t ure

d r o p d u e t o f u e l va p o r isa t io n a n d

pressure reduc t ion a t t he ca rbure t t or

ventu r i. The t empe ra t ure drop o f

2030C result s in a t mo spheric

mo istu re turning in to ice w hich

g ra du a lly blocks t he ven tu ri. This

upset s t he f uel/a ir ra t io cau sing a

prog ressive , smoo th loss o f pow er

a nd s low ly st r a ng les the eng ine .

Con vent iona l f loa t t ype ca rbure t t or s

a r e m o r e p r o n e t o icin g t h a npressure jet t ypes.

b Fuel Icin gLess comm o n, is fu el ic ing w hich is

th e resu lt o f w a te r, he ld in

suspension in t he f uel , precipi ta t ing

a nd f reez ing in the induc t ion p ip ing ,espec ia lly in t he e lbow s fo rmed b y

b e nds .

c Imp act Ice

Ice w hich b ui lds up on a i r int a kes,

f i lte rs, a l terna te a i r valves e t c i s

cal led impa ct ice . It f orm s on th e

a ircra f t in sno w , sleet , sub-zero cloud

GENERAL AVIATION SAFETY SENSE LEAFLET 14A

PISTON ENGINE ICING

Thro tt lebutterfly

Fuel

To e ng ine

Air

Ice in carb urett or venturi

Fuel icing (less commo n)

BUILD-UP OF ICING IN INDUCTION SYSTEM

CAA Car t o DO C(G)6 Drg No 8805b 23-11-84 10-5-90


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a nd ra in , (if e i ther the ra in or th e

a ircra f t i s be low zero C). Th is typ e o f

ic ing can a f f ec t fu el inject ion syste ms

a s w e l l a s ca rbure t t ors. In g enera l,

impa ct i ce is th e ma in ha za rd fo r

t u rb o c harg e d e ng ine s.

d Test ing h a s sho w n t ha t b eca use o fit s g rea te r a nd sea son a lly va r ia b le

vo la t i lit y an d h i g he r w a t e r co n t e n t ,

ca rb icing is mo re l ikely w henMOG AS is used .

e Eng ine s a t r e du ce d p o w e r se t t ing sa re more prone to icing because

eng ine ind uct ion tem pera t ures a relow er. Also , th e pa rt ia l ly c losed

but te r f l y ca n mo re ea sily berestr icte d by th e ice b ui ld-up.

Not e : For t he sake o f s impl ici ty, in t he res t

o f t h is leaf le t , the t erm Ca rb Ic ing

includes Ind uct ion Icing a nd Carb Hea t

includ es Alt erna te Air.

3 ATMOSPHERIC CONDITIONS

a Carb icing is not restr icte d t o coldw e a t he r, a nd w ill o ccu r o n warmdays if t h e humidity is high,especial ly at low power settings.Flight te sts ha ve prod uced seriou s

icing a t de s ce n t p o w e r w it h t he

a mbient (no t sur f a ce) tem pera t ure

over 25 C, even w ith re la t ive

hu midit y a s low a s 30%. At cruise

po w er, icing o ccurred a t 20 C w h e n

t he hu m i d it y w a s 60% o r m o re .(Cold, c lea r w inter d a ys a re less of aha z a rd t ha n hu m id su m m e r da y s

be ca use cold a ir ho lds less mo istu re

tha n w a rm a i r. ) In th e United

King do m a nd Eu ro p e w he re h ig h

hum idity i s commo n, pi lo t s must b e

co ns t an t l y o n t he a le r t f o r t he

po ssib il ity o f carb icing a nd ta ke

correc t ive ac t ion before a n

irre tr ieva ble s itua t ion a r ises . If t hereis a n en g ine f a ilu re due t o ca rb icing ,

t he e ng ine m a y no t re -st a r t an d e ve n

i f it d oe s, the de lay could be cr it ical .

b Ca rb icing ca n o ccur even in c lea ra ir and is t he re f o re m o re da ng e ro u sdue t o t he l ack o f v isua l w a rning . In

cloud th e r isk o f i cing ma y be h ig her

bu t th e p i lo t is less l ikely to b eca u g h t u n a w a r e s.

c Specif ic w a rnings of induct ionsystem icing a re no t n orma lly

inclu de d in a v ia t i o n w e a t he r

f o re ca st s and y o u m u st b e p re p are d

t o de a l w it h i t o n t h e b a sis o f y o u r

know ledg e a nd exper ience . When

de w p o in t i n f o rm a t io n i s no ta va i la b le , assume high humidity

pa r t i cu la r ly w hen: th e surfa ce an d low level visib ili ty

is po o r, especia l ly in th e ea rly

m o rn ing a nd l a t e e ve n ing , a nd

p ar t i cu la r ly w he n ne a r a la rg e

a r ea o f w a t e r;

t h e g r o u n d is w e t (e ve n w it h d e w )

a nd t he w ind i s lig h t ;

ju st b e lo w clo u d b a se o r b e t w e e n

cloud la yers (h ighes t l iq u id w a te rcon ten t is a t cloud to ps);

in precipitat ion, especial ly i f

pers is tent ;

in c lea r a i r w here c loud or fo g

ma y ha ve just dispersed;

in c lo u d a nd f o g , t he s e b e ing

w a ter drop le ts ; hence the re la t ive

humidi ty sho u ld be a ssumed t o b e

100%.d The char t over lea f show s th e w iderang e o f a m b i e n t co nd it i o ns w he re

th e fo rmat ion o f ca rb icing is mo st

l ikely. Pa rt icular no te sho uld b et a ke n o f t he m u c h g re a t e r risk o f

serious ic ing w i th d escent po w er. The

clo s e r t he t e m p e ra t u re an d d e w p o i n t

re ad i ng s , t he g re a t e r t he re la t i ve

humidi ty .


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b St art Up

St a r t u p w it h t he c a rb he a t c o n t ro l in

t h e COLD posi t ion.

c Taxying

Gene ra l ly, th e use o f c arb hea t i s no trecommended whi le t axy ing because

the a ir is usua lly unf i lte red w hen in

t h e HOT po si t ion. How ever, if i t i snecessary USE IT.

d Groun d Run -Up

Check th a t t here i s a significantp o w e r de cre ase w he n ho t a ir is

selecte d (t ypica l ly 75100 rpm o r

35" o f m a n if o l d p re ssu re ) a nd t ha t

pow er is rega ined w hen co ld a ir is re-selecte d. If i t i s suspected th a t ice ispresent , the ho t po sit ion should be

se lected unt il the ice h a s clea red a nd

no rmal pow er is resto red .

e Imm edia t e ly Pr io r t o Take-Of f

Since ic ing can o ccur w hen ta xying

w it h l o w p o w e r se t t in g s , o r w h e n t h e

eng ine is idl ing , se lec t carb h ea t ON

fo r 5 second s an d th en OFF,im m e di a t e ly b e f o re t a ke o f f t o cle a r

a ny b ui ld-up. If t he a i rcra f t i s kept

w a it i ng a t t he ho l d ing p o in t i n

con di t ions o f h igh humidity , it m a y

be n ecessa ry to ca rry ou t th e run-up

dr ill more t ha n o nce to clea r ice

w hich m a y have f o rm e d .

f Take-Off

Ta ke-o ff sho uld only be commenced

w he n y o u a re su re t he e ng ine isdeve lop ing fu l l pow er. When a t f u ll

pow er an d a s a irspeed is bu i ld ing ,

y o u m u st c he ck t ha t t he f u ll t h ro t t le

rpm a nd /or m a ni fo ld pressure is a sexpec ted . Carburettor heat mustNOT be used during take-offunlessspecif ica lly aut ho rized in th e Fl ig ht

Ma nua l o r P ilo t s Opera t ing

H a n d b o o k .

g Climb

Be a le r t f o r sympto ms o f c arb i cing ,

especial ly w he n visible mo ist ure is

present o r i f con di t ions are in t he

high prob a b i lit y ran g es in th e cha r t .

h Cruise

M o ni t o r ap p ro p r ia t e e n g i ne

inst ru m e nt s f o r any cha ng e s w h ichcould indica te icing . Ma ke a ca rb

he a t che ck a t le a st e ve ry 10 m inu t e s ,

(mo re f req uent ly if cond it ions are

cond ucive t o icing) . Use full heat a n dno t e t he w a rn ing o f p a ra 4 (e ), it

ma y t a ke up to 15 seconds to c lea r

t he ice a nd t he e ng ine w ill co n t inu e

to run roug hly a s the ice mel t s a ndpa sses th roug h the en g ine . If th e

icing is so severe th a t t he en g ine h a sdied , keep the ho t a ir se lected a s

residua l hea t in t he ra p id ly coo ling

exhaus t may be e f f ec t ive . In a ll ca ses ,it i s v it a l to se lect c arb hea t b e fo re

a ny se lec to r va lves or linka g es a re

f roze n so l id by a n a ccumula t ion o fice aro und t hem. Avoid cloud s a s

much as possib le , no te ; th a t f ew

p isto n eng ined a ircra f t a re clea red

fo r f l ig ht in ic ing cond it ion s.

i Descent and Ap pro ach

Carb icing is much m o re l ikely a treduced po w er, so se lec t ho t a ir

before, rather than after, p o w e r isre du ce d f o r t he de s ce n t , a nd

especial ly fo r a p ra c t ice fo rced

la nd i ng o r a he l ico p t e r au t o ro t a t i o n ,

ie , be fo re the exha ust s t a r t s to coo l.

(This a lso a l lo w s a check tha t n o ice is

p re se n t a nd t ha t t he c a rb he a t i s st i llw orking .) Ma inta in FULL hea t d uring

lo ng p e r io d s o f f l ig h t w it h re du ce d

pow er se t t ing s. At in te rva l s o f a bo u t

500 f t o r more f req uent ly if

con di t ions req u ire , inc rea se po w er to

cru ise se t t ing t o w a rm t he e ng ine

a nd t o p ro vide s u f f icie n t he a t t o

mel t a ny i ce .

j Downw i n d

Ensu re t ha t t he d o w nw ind c he ckincludes th e fo l lo w ing check:


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No t e t he RPM/Ma nifo ld Pressure

Apply Fu ll Ca rb hea t fo r a bo ut

15 se co nd s a nd no t e t he re du ce dindica t ion .

Ret urn Ca rb he a t t o Cold. The

RPM/Ma nifo ld Pre ssure w ill ret urnto th e ea r lie r ind ica t ion i f the re

w a s no icing . If it i s high er icin g

w a s p re se n t .

k Base Leg an d Fin al A pp ro ach

Unless o the rw ise s t a ted in t he P i lo t ' s

O p e ra t i ng Ha ndb o o k o r

Flig ht Ma nua l, th e HOT posit ionsho u l d b e se le ct e d o n b a se l e g w he n

pow er is reduced . On some eng ineins ta lla t ions , to ensure be t te r eng ine

re sp o ns e and t o p e rm it a g o -a ro u nd

t o b e i n it i a t e d w it ho u t d e la y, it i s

re co m m e n d e d t h a t t h e ca r b h e a t b e

return ed to COLD a t a bo ut 200/300 f t

on f ina ls.

l Go-arou nd or Tou ch and Go

Ensure t he carb hea t i s COLD, idea l ly

be f ore , o r s imul ta neo usly as pow er isa p p lie d f o r a g o -a ro u nd .

m Af te r Land ingReturn t o t he COLD se t t ing be f ore

ta xy ing , if n o t a lread y se t COLD,

(para k).

THE SUMMARY IS OVERLEAF


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6 SUMMARY

Icing forms steal thi ly.

Som e a ircra f t /eng ine

combinat ions are more suscept ib le

t h a n o t h e r s. Icing ma y occur in w a rm humid

cond it ion s an d is a po ssib il ity atany time of the year in the UK.

Mog a s ma kes ca rb icing mo re

likely.

Low pow er se t t ing s, such a s in a

de scent o r in t he c ircui t , a re mo reprone t o g ive ca rb i cing .

U se f u l l ca rb he a t f r e q u e n t ly w he n

f lying in cond it ions w here carb

ic ing is l ikely. Reme mb er t ha t th e

RP M g a u g e is y o u r p rim a ry

ind ica t ion fo r a f ixed p itch

propel ler ; mani fo ld pressure for

variab le pi tch.

Trea t th e ca rb h ea t a s an ON/OFF

contro l e i ther fu l l ho t o r fu ll

cold.

It t a k e s t im e f o r t h e h e a t t o w o r k

a nd t h e e ng i ne m ay ru n ro u g h l y

w hi le t he ice is c lea ring .

Timely use o f a pprop ria te

pr o ced ur e s ca n PREVENT THIS

PROBLEM.

FINALLY

In t he event o f ca rb hea t system f a ilure in f l ig ht :

Keep o u t o f i cing con di t ions.

M ai n t a in h i g h t h ro t t l e se t t ing fu ll thro t t le if po ssib le .

Wea ken t he mixtu re s light ly.

La nd a s soo n a s rea son a b ly possib le .

PREVENTION IS BETTER THAN CURE

Other leaflets in this series:

1C Go o d A ir m an sh ip Gu id e

2B Ca re o f Passenge rs

3C W in t er Flyin g

5D VFR Navi gat i on

6C Aer od rome Sen se

7B Aer o pl an e Per f o rman ce

8D Ai r Tra f f i c Se rvi ces Ou tside

Cont ro l led Airspace

9A Wei gh t an d Bal an ce

10A Bir d Avo id an ce 11 In t er cep t io n Pr oced ur es

12C St r ip Sen se

1 3A Co ll isi on Avo id an ce

15B W ake Vo rt ex

1 6A Bal lo o n A irman sh ip Gu id e

1 7B Hel ico p t er A irman sh ip

18A M i li t ar y Low Fl yi ng

19 Aerobat ics

20A VFR Fl ig h t Pl an s

21A Di t ch ing

22 Rad io t elephony

2 3 Pi lo t s: It s y ou r Deci si on

24 Pi lo t Healt h New leaf lets w ill appear from t ime to

time on a non-reg ular ba sis.

There is no res tr ic t ion on photo-copying and ex trac ts can be

published provided the source is a cknow ledg ed.

Th i s l e a f l e t d o e s n o t s u p e r s e d e o r r e p l a c e a n y f o r m a l

documents .

If c lubs , org an isa t ions or individua ls w ish to receive fur t her

co p i e s, p l e a s e w r it e t o We s t w a r d d o c u m e d i a Li m it e d ,

3 7 Wi n d s o r St r e e t , C h e lt e n h a m , G l o s G L5 2 2 D G . Fa x . No .

01242 584139. Tele ph o ne 01242 235151.

Su gges t io n s an d tec h n ic a l q u er ie s to SR G Sa fe ty Pro m o t io n

Sec t ion , Avia t io n Ho use , Ga tw ick Airport , West Sussex RH6

0YR. Te lep ho ne 01293 573225/7.

ISSN 0266-1519

Civil Aviat ion Aut ho rity 2000

P re p a r e d b y t h e S a f e t y P ro m o t io n S e ct i o n a n d t h e

C o r p o r a t e C o m m u n i c a t i o n s D e p a r t m e n t o f t h e C i v i l

Avia tion Auth ority.

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Givrajul La Motoarele Cu Piston CAA