Upload
doanngoc
View
220
Download
2
Embed Size (px)
Citation preview
AN INAN INAN IN---HOUSE NEWSLETTHOUSE NEWSLETTHOUSE NEWSLETTER OF OPERATIONS DEPT.ER OF OPERATIONS DEPT.ER OF OPERATIONS DEPT.
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: [email protected]
© 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 [email protected] 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