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Vol.3, No.8 Vol.3, No.8 Vol.3, No.8 FFFlight Safety & Quality Assurance Division August 2008light Safety & Quality Assurance Division August 2008light Safety & Quality Assurance Division August 2008

FLIGHT SAFETY/AIRCRAFT ACCIDENT LINKS

kacops.kuwaitairways.com www.flightsafety.org

www.ntsb.gov www.bea-fr.org www.bst.gc.ca

www.bfu-web.de www.aaib.gov.uk www.atsb.gov.au

In this issue

Dual Side Stick inputs 2

Hot towers 4

Lightings strikes 5

Photo of the month 6

IBERIA A320 crash at Bilbao

1

FLIGHT SAFETYFLIGHT SAFETYFLIGHT SAFETY

Fly-By-Wire(FBW) aircraft like A320/ A330

and A340 have Flight Control Computers

(FCC) which translate pilot commands from

the control stick into control surface com-

mands. These aircrafts have features like

Angle-of-Attack (AOA) Limiting etc., to en-

hance safety. A control logic handles the

situation of both pilots operating the control

stick. However, there have been incidents

arising from dual inputs.

We look into this issue in some detail.

We are in the middle of summer and the

varied weather conditions prevail around. We

look at the role of hot towers and lightning

strikes on flight operations and safety.

As always, we look forward to your feed-

back, suggestions and contributions. Happy

reading and many more safe landings.

Editorial

On February 2001, around 23:10 local

time, Iberia flight 1456, an Airbus A320-214

was approaching Bilbao’s Sondica airport.

The flight was from Barcelona to Bilbao and

had 136 passengers and 7 crew on board. The

conditions in Bilbao were night VMC, with a

10Kt southwest wind and gusts up to 25 Kt.

Visibility was in excess of 10 Km and there

were scattered clouds above 5600ft.

The flight from Barcelona was uneventful.

The pilot on the RH side was the PF and was

in line flying under supervision. The supervis-

ing Captain was on the LH side and was the

PM. The third crew member seated on the

jump seat, was the first officer who had given

his seat to the pilot under supervision.

At about 25 Nm and 7500 ft from the des-

tination, they crossed a small cumulus with

strong turbulence. Descending through 6000

ft and established on the Bilbao localizer they

found winds of 55Kts. The Bilbao ATC tower

cleared them to land on runway 30, and

informed of winds of 8-15kts at 240 degrees

with light turbulence.

The aircraft reached the decision height of

247 ft under VMC and continued the approach

to land. In the last few seconds of touchdown,

the vertical descent speed was very high

around 1200 ft/min and the sink rate warning

of the GPWS sounded twice.

Pitch-up command were applied by both

pilots on the sidestick, but the crew’s desired

and commanded action was not performed by

the aircraft.

As the AOA-protection was triggered

during this event, the system commanded a

nose down signal, which was performed, even

though both pilots had their sticks full back-

ward, commanding a “climb”.

Then the Captain, in view of the sink rate

warnings, selected TOGA power setting to go

around and abort the landing.

The pilot’s actions could not avoid the hard

touchdown. The aircraft touched down with all

three gears struts almost simultaneously. The

nose gear subsequently collapsed and the

plane slid along the runway for 1100m before

coming to a stop. During the emergency

evacuation, twenty three passengers and a

cabin crew had minor injuries. An old female

passenger with serious injuries had to be

hospitalized.

The aircraft suffered substantial damage

and was beyond economical repair.

The Spanish CIAIAC (Comisión de In-

vestigación de Accidentes e Incidentes

Iberia A320 crash at Bilbao NEWSLETTER TEAM Capt. Shawki Al-Ablani

Dr.M.S.Rajamurthy

Contact: Flight Safety & Quality

Assurance Division, Operations Dept.

P.O.Box.394, Safat 13004 Kuwait

Phone:+965- 4725475 Fax: +965- 4749823

E mail: kwioeku@kuwaitairways.com

© Fred Seggie/airliners.net

de Aviación Civil) investigated the

accident and came with the following

findings.

• During the approach to Bilbao

airport the aircraft experienced signs of

moderate to severe turbulence

• High altitude wind intensities and

other weather conditions were condu-

cive to the appearance of turbulence

phenomena.

• The aircraft vertical speed in the

last seconds of the approach was very

high

• The design of the flight control

system was such that the actions of

both pilots over the flight controls

were ignored by the logic of the control

system and prevented the aircraft from

flaring.

• TOGA thrust was applied to the

engines in the last instant before touch-

down but the aircraft could not initiate

a climb.

• The aircraft impacted with the

nose gear, centered on the runway, at

the threshold. The nose gear collapsed

and the aircraft stopped after 1100m of

ground run. At the end of the run, the

aircraft lost directional control and

came to a stop at an angle to the

runway.

• The aircraft suffered damage to

the nose gear and the two engine

nacelles, and the main gear tires burst.

Internal structural damage caused the

aircraft to be written off.

The investigation concluded that the

cause of the accident was the activation

of the AOA protection system which,

under a particular combination of

vertical gusts & windshear and the si-

multaneous actions of both crew mem-

bers on the sidesticks, not considered

in the design, prevented the aircraft

from pitching up and flaring during the

landing.

The CIAIAC made specific recom-

mendations regarding the dual inputs,

to the manufacturer Airbus and the

Operator IBERIA as follows.

• On March 12, 2001, CIAIAC made

a preliminary recommendation to the

French Civil Aviation authority (DGAC-

F) to define with the manufacturer and

to immediately issue safety measures

to prevent the repetition of these kind

of events in the aircraft of the type

A320 family and in other aircraft

equipped with similar Flight Control

systems

• Taking into account that the dual

inputs actions on the sidestick cause

the effect of adding both inputs, it is

recommended that the operator Iberia

improve the instruction of their A-320

crews in order to avoid the simultane-

ous activation of the sidestick by both

pilots without pushing the override

button, regardless of the type and

composition of the flight crew.

In March 2001, DGCA-F issued a

Airworthiness Directive (AD) for the

A319/A320 aircraft. It ordered the

crews to fly at least 10 Kts faster and

use only Config.3 (flaps 3) setting on

approach in conditions with reported

gust wind increment (max. wind minus

average wind) greater than 10Kts or

moderate to severe turbulence

expected in short final. It also stated

that if “sink rate” GPWS warning occurs

below 200ft, an immediate go around

should be initiated.

Airbus Industrie developed a new

standard for the Elevator and Aileron

Computer (ELAC), to modify the logic in

the Angle-of-Attack (AOA) protection in

case of turbulent conditions. This new

standard was certified by mid 2001 and

the corresponding Service Bulletin (SB)

was published in September 2001.

The software modification consid-

ered mandatory by the aeronautical

authority, had to be incorporated on all

A-319/A320 and A321 before December

2002.

The software modification to the

ELAC included two actions that affect

the activation and de-activation of the

AOA protection system.

With these modifications the protec-

tion level is maintained against dynami-

cally aggressive maneuvers made by

the pilot, but the premature activation

of the AOA protection triggered by wind

gusts is inhibited, and a de-activation in

flight at low height at less stringent

conditions is allowed.

REFERENCE:

1. CIAIAC Technical report A-006/2001,

“Accident of aircraft Airbus A-320-214,

registration EC-HKJ, at Bilbao Airport

on 7 February 2001.”

Page 2 FLIGHT SAFETY Volume 3, No.8

Dual side stick inputs

In the dual control cockpit environ-

ment, the flying task sharing principle is

that at any time one pilot is flying (PF)

and the other Pilot is monitoring (PM).

In the extreme event when PM

disagrees with the PF inputs, he/she has

to verbally request corrective actions or,

if deemed necessary, take over the

controls by clearly announcing “I have

controls”. This will mean that he/she

becomes PF from that moment and the

other Pilot PM.

Like the case of Iberia flight 1456,

there have been incidents where both

pilots demanded control by simultane-

ously operating their sidestick.

An A320-200 on a climb to FL 320 at

about Mach 0.78, (Clean Config. with

AP2 engaged (CLIMB/NAV) and ATHR

Engaged & Active in Thrust mode)

encountered significant turbulence and

began an Uncommanded roll to the

right. This was initially counteracted by

the Auto Pilot. However, at a speed

above 250kts, Auto Pilot command on

ailerons are limited at 8°. Therefore,

The crashed Iberia A320 with collapsed nose gear

due to the high turbulence the roll

reached a value of 40° to the right.

Both pilots reacted with full LH stick

commands and 10° LH rudder pedals.

This induced the disengagement of the

Auto Pilot. During the next 20 seconds,

the Captain and First Officer applied

dual stick inputs, leading to roll oscillat-

ing between 33° left and 49° right, as

well as a loss of 2400 feet altitude. The

Captain then re-engaged the Auto Pilot,

selected Flight Level 310, and the flight

resumed without noticeable event.

Another example of dual input.

The feedback to Airbus from line

operations indicate that dual inputs still

occurred and sometimes led to opera-

tional incidents.

Types of Dual stick inputs

Analysis of reported dual side stick

inputs events by Airbus revealed that

there are three types of occurrences:

1. The “Spurious” Dual Stick inputs

These are due to an inadvertent move-

ment of the stick by the PM. For exam-

ple when grabbing the FCOM or when

pressing the R/T. A spurious dual stick

input only marginally affects the aircraft

behavior as it is of small magnitude and

time limited.

2. The “Comfort” Dual Stick inputs

These are due to short interventions

from the PM who wants to improve the

aircraft’s attitude or trajectory: These

are generally experienced in approach,

during a capture (altitude, localizer), or

in flare, and have minor effects on the

aircraft’s altitude/trajectory. However,

as the PF is not aware of the PM’s inter-

ventions, PF may be disturbed and may

counteract the PM’s inputs.

3. The “Instinctive” Dual Stick Inputs

These are due to a “reflex” action on

the part of the PM on the stick. This

instinctive reaction may come about

when an unexpected event occurs, like

for example an AP disengagement, an

overspeed situation or a dangerous

maneuver. Such interventions are more

significant in terms of stick deflection

and duration. Usually in such situations,

both pilots push the stick in the same

direction, which may lead to over

control and situations illustrated by the

two cases reported here.

Sidestick Operation

In A320 and A340, the two sidesticks

are not mechanically linked as in the old

mechanical controls. As a result they

can be operated independent of the

other. When one sidestick is operated it

sends an electrical signal to the Flight

Control Computer (FCC). When both

sticks are moved simultaneously, the

system takes the algebraic sum of the

two signals. The total is limited to the

signal that would result from the maxi-

mum deflection of a single sidestick.

To avoid both signals being added

by the system, a priority Push button

(PB) is provided on each stick. By

pressing this button, a pilot may cancel

the inputs of the other pilot.

Dual Sidestick inputs Warning

System

To warn the crew in case of dual

sidestick operations, Airbus designed a

package of dual input indicators and

audio warning. These operate when

both side sticks are deflected simulta-

neously by more than 2°.

Visual indication

When a dual input situation is

detected, the two green priority

lights located on the cockpit front

panel flash simultaneously. This visual

indication is an ADVISORY of a dual

input situation

Aural Indication

After the visual indication has been

triggered, a synthetic voice “DUAL

INPUT” comes up every 5 sec, as long

as the dual input condition persists.

The synthetic voice is a WARNING

of a dual input situation (Note: This

audio has the lowest priority among the

synthetic voice audio alerts.)

These visual and aural warnings

have proved to be efficient means to

inform the pilot of dual inputs.

These visual and audio indications

are designed to provide the crew with a

progressive alert.

It is found that these warnings are

very effective in educating the pilots to

respect the basic task sharing principle

and drastically reduced the number of

dual input occurrences.

The Dual stick warning system has

been implemented in A320 and A340

fleet of KAC. In the A320 and A340

FCOMs Vol.1(1.27.40) under Flight Con-

trols, sub-heading Sidesticks, this is

very clearly explained.

REFERENCE:

1.Frederic Combes., “Dual stick inputs”,

SAFETY FIRST, No.3, December 2006.

Page 3 FLIGHT SAFETY Volume 3, No.8

Captain F/O

DUAL INPUT

A green light will come ON in front of the Pilot who is taken control if the other stick is not in neutral position, and a red light in front of the

pilot whose stick is deactivated

Page 4 FLIGHT SAFETY Volume 3, No.8

Hot Towers Adopted from Karsten Shein’s article “Towering Infernos” in May 2007 issue of Professional Pilot

Map of global sea surface temperatures produced by the National Centers for Environmental Prediction and the University of Wisconsin. Deep red regions near the equator are areas where hot towers may occur.

Flying across the equator, one would

expect a calm, clear sky and endless

visibility over azure tropical waters.

But, as you approach equator, you

notice a wall of white ahead in the

distance. As you move closer, with every

mile, there are more small cumulus

clouds below, and you could even pick

up an occasional turbulence jostle. The

wall of white is now much larger, extend-

ing well above your present altitude, and

there are several tall peaks scattered

among the mountain range of water va-

por.

An ascent should get you up and

over the cloudscape in front of you, but

with just a few miles to go, you can tell

that some of these are pushing well

above your service ceiling—no small feat

given the cruising altitude of FL350 to

FL450 is what keeps you above the

weather.

But these clouds are monsters. At a

reasonable estimate the tallest of them

are pushing 60,00ft. As a pilot you intui-

tively know that cumulus clouds means

updrafts and turbulence and a towering

cumulus of these proportions will not

produce smooth sailing. These extreme

clouds are known as HOT TOWERS.

The general impression of tropical

region is one of gentle, warm breezes,

cloudless skies and year round warmth,

except for an occasional hurricane. As

tropics are integral and often vigorous

part of earth’s heat pump, strong

weather is often found there and unsus-

pecting aviators who let their guard

down will be in for some surprises.

The region within 10 degrees of the

equator is known as the tropics and here

the sun is more or less directly overhead

for most part of the year and thus solar

heating is consistent in this region.

A look at the world map reveals that

most of the Earth’s tropical surface is

covered by ocean. As water is good at

absorbing heat, it gets heated by the

sun. The air also gets heated by the sun

and hot air can hold lot of water vapor

readily supplied by the warm ocean. The

combination of hot air and high humidity

makes the air less dense than the cooler

drier air above it. This makes the hot air

to move up till it reaches a point where

the density is equal. As the air moves up

away form its heat and moisture

sources, it cools, lessening its ability to

hold moisture. But as the water vapor

condenses, it releases its latent heat

which in turn slows the cooling allowing

the air to ascent further.

When sufficient water vapor conden-

sation occurs cumulus cloud is formed.

The quantity of water vapor and the

height to which air can rise before find-

ing an equilibrium density level deter-

mines the height of the cumulus cloud.

The critical factor to sustain these large

clouds is the continued supply of warm

humid air from below. This help comes

from the thermal global atmospheric

circulation.

Unlike the tropics, the Earth’s higher

latitudes experience a deficit in heat

throughout the year. To keep polar heat

loss from causing high latitudes to cool

uncontrollably, the surplus heat from the

tropics must be transported poleward.

The rising air reaches a point at

which it stops ascending. But it is now in

the way of the rising air beneath it. It

can’t go up as the stable air above acts

as a ceiling. It cannot go East or West as

the situation is same. So the only place

to go is poleward.

Eventually, the cold dry air aloft

sinks back towards the surface around

the tropics. But, as the sinking air

reaches the subtropical oceans, it

spreads out, with some of it flowing back

towards the equator, picking up moisture

from the warm water along the way to

go around. This thermally driven circula-

tion known as the Hadley cell is the

frame on which the towering cumuli or

the hot towers form.

As this inflow is occurring on each

side of the equator, it converges in the

tropics at a place known as the Inter-

tropical Convergence Zone (ITCZ) the

location of which varies from summer to

winter, but is generally found near where

the sun is almost directly overhead.

As it migrates around the equator,

the ITCZ, like other atmospheric bounda-

ries, develops kinks known as troughs

and ridges. Convection within the

troughs tends to be stronger than in the

ridges, and it is there that hot towers

often form. If the conditions in the

trough are right some storm cells grow

to tremendous height and result in

extremely heavy rainfall and frequent

lightning.

Hot towers need certain conditions

to form. First, there must be ample heat

and moisture, with moisture extending

throughout troposphere. The second is

the absence of windshear aloft. Strong

winds aloft will tend to knock over the

updrafts before they get too high into

troposphere. Finally, the atmosphere

must be unstable all the way upto

stratosphere. If the rising air encoun-

ters a stable layer, it is likely that it can

only make a few thousand feet instead

of the tens of thousand it would other-

wise achieve.

As continual heating of tropical air

raises the air temperatures, the

Lightning is a product of thunder-

storms and with thunderstorms prevail-

ing all around, there is a risk of light-

ning strikes. Globally it is estimated

that each commercial aircraft sustains

one lightning strike per year.

KAC statistics for 2000-2007

reveal an average of two lightning

strikes per year for the entire fleet.

None of these had any major damage

and all flights terminated safely.

The direct effects of lightning strike

is the burning and puncture at lightning

attachment points, and arcing and

sparking in their vicinity. In case of

composites, lightning strike can cause

puncture and delamination.

The indirect effect of lightning is the

very high-voltage, current and mag-

netic fields on aircraft avionics, Electri-

cal systems, hydraulic tubes and flight

control cables. Lightning induced volt-

ages and currents in fuel tanks and fuel

system plumbing can cause sparks and

ignite the fuel.

Nearly lightning can blind the pilot

rendering him momentarily unable to

navigate either by instrument or by

visual reference. Lightning can induce

permanent errors in the magnetic com-

pass and lightning discharges, even

distant ones, can disrupt radio commu-

nication.

Regulations demand aircraft designs

that will protect it from a fuel explosion,

aircraft electrical/electronic system up-

sets, or significant aircraft structural

damage. The FAA has three Advisory

Circulars (AC) that provide guidance for

approval of lightning protection for an

aircraft. These are

• AC 20-53B on Protection of Aircraft

Page 5 FLIGHT SAFETY Volume 3, No.8

Lightning Strikes Dr.M.S.Rajamurthy

tropospheric air molecules gain energy and require more

room for movement. As a result troposphere expands. The

only direction for this expansion is into the less dense air of

the stratosphere above it. As a result, stratosphere which

normally begins around 30,000—40,000ft does not start until

50,000—60,000ft MSL. This places the stable stratosphere

well above the ceiling of most aircraft.

The hot air updrafts within these hot towers continue to

rise as long as they remain less dense than the air around

them. Instability throughout the full extent of the troposphere

will ensure that this ascension will continue until tempera-

tures invert at the base of the stratosphere. Momentum will

usually carry the hot tower cloud a few hundred feet into the

stratosphere, and the end result is a storm cell that may top

out well above FL600!

Like most thunderstorms hot towers tend to form in the

afternoon, but they differ from most ordinary airmass thun-

derstorms in two aspects. Firstly, they may last for many

hours - often well into the evening - while remaining more or

less stationary. Secondly because of their size and amount of

water vapor they contain, hot towers can suspend rain

droplets until they reach very large sizes– of the order of

5mm or greater. With the generally weak updrafts, these

super sized drops are able to fall through to the ground,

because the updrafts remain steady, the falling rain doesn’t

easily destabilize and destroy the cell as it would with a

regular airmass storm.

Hot towers and hurricanes are connected as the condi-

tions for their formation are similar. Hot towers can provide

massive amounts of energy needed for a hurricane to

strengthen. Research suggests that hot towers are essential

to transport heat energy rapidly to the top of hurricane and

feeding it into the eye to maintain the warm core of the

storm. These are present in the eyewall ( see the figure at

the right top) of most strong hurricane.

Hot towers can easily disrupt a transtropical flight. When

encountered, one can expect engine flooding precipitation,

even at higher flight levels, and can expect the storms to

remain for several hours. Vertical shearing from updraft may

result in significant turbulence in and around the tower. How-

ever, because of their stationary nature, it is easy to predict

their location and occurrence along the route.

Hot towers are an essential component of the atmos-

phere’s circulation system. They are responsible for trans-

porting surplus tropical heat energy towards the poles, and in

the process keep the higher mid-latitudes from becoming too

cold and tropics too hot. Unfortunately, they area an obstacle

to trans-equatorial air travel.

The only safe option is to navigate around hot tower and

expect some turbulence on the way.

Combination satellite and radar image of hurricane bonnie(aug.1998), clearly showing a 60,000ft MSL hot tower in the eyewall.

A massive storm cell develops an anvil top as it slams into the base of the stable stratosphere. Hot tower ITCZ storms often develop anvil tops protruding several hundred feet into the stratosphere.

Volume 3, No.8 FLIGHT SAFETY

The Confidential Aviation Hazard Reporting System (CAHRS) provides a means of reporting hazards and risks in the aviation system be-fore there is loss of life, injury or damage. It is open to anyone who wishes to submit a hazard report or safety deficiencies confidentially and non-punitively. Reports help to identify deficiencies and provide safety enhancement in areas of aviation. CAHRS forms can be collected at different location of KAC (i.e. Flight Dispatch) Premises. Completed forms can be dropped in FS&QA allocated box at Flight Dispatch or e-mailed to kwioeku@kuwaitairways.com or faxed to 00965-4749823 or mail to Flight Safety and Quality Assurance office, Operations Department, P.O. Box 394, Safat 13004, Kuwait Airways –Kuwait.

Page 6

fuel system against fuel vapor ignition

caused by lightning

• AC 20-136A on Protection of aircraft

electrical/electronic Systems against

indirect effects of Lightning

• AC20-155 -SAE documents to Support

Aircraft Lightning Protection Certifica-

tion.

Over past two decades major air-

craft structures have been built with

composites. Metal aircraft structure

provide good conductive path and light-

ning remains outside the aircraft. As

composites are poor conductors, the

lightning induces higher voltage and

results in high currents on wire bundles,

fuel tubes, hydraulic tubes, push rods

and control cables.

Airbus A340s have carried fuel

safely in their composite horizontal tail

since 1991. Airbus A380 structure has

25% composites the new Boeing 787

will have 50% composites.

In spite of design and certification

for lightning protection, aircraft do

encounter lightning strikes and get

damaged. Following are three cases of

lightning strike damage.

1. On February 10,2008, a Conti-

nental Airlines Boeing 757 was struck

by lightning shortly after taking off from

Newark airport, in torrential rain and

thick clouds. The nose cone was dam-

aged with a 2ft gash, a hole and the

ripped back skin.

2. On April 5,2008, in Sofia, Bul-

garia, a Lufthansa 737 was struck by

lightning just after take off, and the

horizontal stabilizer was damaged.

3. An Airbus A320 was struck by

lightning during landing at Bilbao, Spain

resulting in punctures in the fuselage.

Revision to KCASR DGCA of Kuwait has amended the

Kuwait Civil Aviation Safety Require-

ments (KCASR) increasing the age of

pilots operating commercial flights from

the attainment of the age 60 to 65

years. This is based on the ICAO

Amendment no.167 to the International

Standard and Recommended Practices

of Annex 1—Personnel Licensing.

This comes with additional medical

and operational requirements.

The pilot who attains the age of 60

shall is not permitted to act as PIC or

Co-pilot of an aircraft engaged in air

transport operations unless:

• He is a member of the multi pilot

flight crew

• He is the only pilot in the multi pilot

flight crew who has attained 60 years of

age and

• He did not cease to fly for a period

exceeding 24 months under the privi-

leges of his license.

Additional medical requirements include

ECG, Audiograms, Full blood Hemoglo-

bin, Cardiac Enzyme and lipid profile,

Cardiovascular system, respiratory

system examinations and psychological

evaluations.

PHOTO OF THE MONTH THE JUMBO BREAKS

On 25th May, 2008 a Kalitta Air - Boeing 747-209F on a flight from Brussels, Belgium to Bahrain while attempting to take-off on runway 20, skidded off the runway and split in two pieces. None of the five crew mem-bers were seriously injured.

The crew reportedly heard one or two loud bangs and decided to abort the take-off, but the aircraft continued past the end of the runway, broke in two, and came to a rest 300 meters past the end of the runway, close to a rail line and some 500 meters from housing. © Snorre-VAP/airliners.net

Damaged nose cone of a Continental airways B757

Damaged Horizontal stabilizer of Lufthansa Boeing 737

Punctures on the A320 fuselage due to lightning strike