[1] Safety Board (24/02/94) section 1.12.3.1. Retrieved on

1 El Al Flight 1862 at Amsterdam, Netherlands (N.D). Accident
overview. Retrieved on 30/11/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=38&LLTypeID=2

 

2 El
Al Flight 1862 at Amsterdam, Netherlands (N.D). Fuse Pins. Retrieved on
05/12/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=38&LLTypeID=2

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3 Raad voor
de Luchtvaart, Nederlands Aviation Safety Board (24/02/94), section 1.6.3.1.
Retrieved on 30/11/2017

 

4
Raad voor de Luchtvaart, Nederlands Aviation Safety Board
(24/02/94) document
AAR 92-11. Retrieved on 30/11/2017.

5 El Al Flight 1862 at Amsterdam, Netherlands (N.D). Breakaway
philosophy of the 747 strut. Retrieved on 30/11/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=38&LLTypeID=2

 

6 El
Al Flight 1862 at Amsterdam, Netherlands (N.D) .Figure of bottle bore fuse pin
– initial design. Retrieved on 30/11/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=38&LLTypeID=2

 

7
El Al Flight 1862 at Amsterdam, Netherlands (N.D).
Design evolution of 747 fuse pin. Retrieved on 30/11/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1&LLID=38&LLTypeID=2

 

8 Raad voor
de Luchtvaart, Nederlands Aviation Safety Board (24/02/94) section 1.16.1.
Retrieved on 05/12/2017.

 

9 Raad voor
de Luchtvaart, Nederlands Aviation Safety Board (24/02/94) section 1.12.3.1.
Retrieved on 30/11/2017.

10 Raad voor
de Luchtvaart, Nederlands Aviation Safety Board (24/02/94) section 1.12.3.4.
Retrieved on 05/12/2017.

11 Lizzy
Bloem, 2004, The 1992 El Al Bijlmer crash: A cover-up of a chemical inferno?,
The electronic intifada. Retrieved on 05/12/2017.

12
Aviation, 2017, what is the reasoning behind using depleted uranium as
counterweights in the 747? Retrieved on 06/12/2017.
https://aviation.stackexchange.com/questions/35344/what-is-the-reasoning-behind-using-depleted-uranium-as-counterweights-in-the-747

13
Neal Baker, 2017, WEAPON OF MASS DESTRUCTION What is sarin nerve gas, how does it kill you and
what does footage of the Syria ‘chemical weapon attack’ show?, The Sun.
Retrieved on 06/12/2017

 

14
RIBA Architecture, 2005, Code of professional conduct, Retrieved on 06/12/17

15
Don Phillips, 1993, BOEING ABANDONS 747 JUMBO JET’S BREAKAWAY ENGINE DESIGN,
Washington, The Washington Post, 4th paragraph

16
El Al Flight 1862 at Amsterdam, Netherlands (N.D). Design changes to the 747
struts. Retrieved on 06/12/2017 from http://lessonslearned.faa.gov/ll_main.cfm?TabID=1=38=2

 

17
2015, Causes of fatal accidents by decade, Planecrashinfo.com, Retrieved on
07/12/2017

 

In
contrast, at the time of the flight 1862 around 60% of all plane crashes were
due to pilot error17. This is a shocking statistic and although the
El Al crash was not directly down to the pilot’s errors, he could have
potentially played some part in it and its aftermath. Because of the planes
Israeli identity, one of the El Al privileges at Schiphol airport was to be
able to “fly the El Al way” meaning the ability to land and take off as it
pleases. This authority over other planes boils down to a heightened risk of
hijack due to the cargo goods onboard. It is thought that this may be the
reason for the pilot’s choice of route over the busy residential area despite
the air traffic control tower apparently having a different flightpath and
landing strip in mind. Although this did not directly affect the mechanical
failures of the plane, had it not been for the pilot’s choice of route the
plane could have landed elsewhere and spared 46 lives.

Not only
did the disaster speed up the evolution and integration of improved fuse pins
but it also led to significant design changes of the engine struts. From 1995
the FAA mandated the retrofit of the new struts which are a more robust design
for increased strength; designed to be “failsafe for all engine attachment
points and damage tolerant for any strut to wing failures”16. These new struts also feature the improved
straight bore fuse pins which although they are used to protect the wing tank,
the design is intended to prevent the engine pylon separating from the wing
during flight16.  In the event
of the failure of one of the fittings, the remaining fittings are designed such
that they will support the strut until the stress exceeds the point that the
critical crack length is reached. The design of the strut has progressed
massively, and continues to progress, since flight 1862 and as a result only
around 18% of todays plane crashes are due to mechanical failures17; even less specifically emerging from the
engine struts.

In the aftermath of the event, Boeing officials
came out and “essentially acknowledged that it had built the worlds most popular
jumbo jet for 25 years under the misconception that the planes could fly after
losing engines and that having an engine break away after a catastrophic
failure sometimes was safer”15 . Straight away they deterred from their ways
and made steps into modifying and implementing a new third straight bore pin.
It was designed such that it would not allow the engine to break free unless in
a belly landing. The newly improved design was ground from a hardened stainless
steel to prevent corrosion and prevent fracture at low stress values. It was since
determined that the internal notches of past pins put the component under elevated
stresses leading to fatigue crack initiation and subsequently a straight bore
hole through the middle was implemented as a design feature used to reduce the
stress build up7. The image shown right details the design evolution
of the mid spar fuse pins aboard a Boeing 747’s engine strut and how they have
changed significantly over time7. To my way of thinking, the
redevelopment of the pins encapsulates the ability to apply specific knowledge to
a problem and rectify it through the likes of multi-dimensional stress analysis,
such was applied on the fuse pins in order to determine the reason for their
failures. As a result, they managed to progress the design into a much more
efficient and safe one which we still use to this day

As
previously touched upon, before the incident it was brought to the attention of
Boeing team that the design of the bottle bore fuse pins in fact initiated
fatigue fracturing in 747’s due to the varying cross-sectional areas, which
allowed designers to vary the strength of the pin across the shaft. 2 years after
the initial suggestion to inspect the fuse pins, a manufacturers recommendation
was then issued to terminate the use of the bottle bore fuse pins and instead
use an improved ‘Bulkhead’ configuration which the Federal Aviation
Administration followed up by then allowing the operator to either change the
fuse pins or continuing to carry out the checks indefinitely7. At
the time of the crash, flight 1862 was one of the few 747’s on which the pins
had not been replaced meaning the chance of fracture was heightened
significantly, eventually leading to their failure which could have been
prevented. In my opinion, this technical factor was definitely an act of gross
negligence as despite being warned 13 years prior to the event about the
seriousness of the situation, they continued to pay a lack of respect to the
recommendations given and showed an inadequate level of professional ethics.

Flight 1862 could be considered a
turning point with regard to some aspects of the aeronautical industry as it
provided us with with an insight into issues that can arise if care is not
taken and problems aren’t dealt with using sufficient professional ethics. The
term professional ethics is used to “encompass the personal, or corporate
standards of behaviour expected by professionals”14. Every professional that exercises their
knowledge in light of a public service must do so to the best of their ability.
It can be considered a moral issue if they fail to comply with this, thus it
could be argued that with regard to certain features of this aircraft the
professional ethics were overlooked in parts and as such, the structural
integrity of the plane and safety of those onboard was compromised.

Discussion

Although
it did not play a contributing role in the downfall of the aircraft the effects
of the crash were heightened by the military cargo on board that, although
initially denied by the Dutch government, contained a number of hazardous
chemicals. The government also neglected claims that the sudden rise of health
ailments and unidentified diseases in the area was of relation to the disaster,
though hundreds inhaled poisonous smoke from the burning aircraft and building11. Among a number of other hazardous materials
on board the aircraft, it was found that along with other 747 planes at the
time, flight 1862 contained around 282kg of depleted uranium which was used as
a counterweight located in the tail of the plane12- a radioactive material that is used in the
production of nuclear and military grade weapons that is extremely harmful when
burned and inhaled. However, more worryingly in fact was the array of chemicals
including methyl phosphate which are used in the production of sarin nerve gas11-
a weapon more recently used in chemical attacks in Syria, expected to be
“around 26 times deadlier than cyanide”13.  Sarin
gas is a colourless and odourless agent that slowly kills its victims by
suffocation and should be handled with extreme care. It is extremely likely
that had it not been for the presence of the gas that the death toll and number
of people with subsequent health issues would have remained lower. Delayed
death started around 48 hours after the disaster, starting with household pets
before humans fell victim. Laboratory research showed severe signs of
poisoning. It was not long before a “hidden epidemic emerged among the
surviving apartment block residents” and a “cluster of serious human health
problems became evident six months after the crash”11.

The loss of the 3rd
and 4th engine pylons resulted in a number of faults in the
mechanical systems on board the aircraft hence initiating the flight control
failure. When the struts were separated from the aircraft the 2 corresponding
hydraulic systems were severely damaged consequently meaning that the hydraulic
pressure required for the flight controls was not available. When the
mechanical systems failed it caused a domino effect, subsequently taking out
the pneumatic systems with it. As the strut was detached it took a 30-ft. strip
of the leading-edge air duct, from between the 3rd and 4th
engines, with it. The damaged duct allowed venting of the bleed air supplied by
the 1st and 2nd engine systems10. It was concluded that as the 3rd
engine was lost, the two functioning engine systems that remained continued to
supply enough air to maintain the pneumatic pressure above the minimum 8-psi
and as a result the valve was kept open10. If it were to drop below
the 8-psi datum then the valve would instantaneously close. As the aircraft
lost height the pressure decreased, hence the flaps closed and all power was
lost in the right wing meaning steering became highly futile10.
Likewise, later research found that at the current velocity of 280 knots there
was sufficient lift on the immobilised wing to keep it airborne. However, as
drag ? (velocity)2 when the
aircraft slowed down in order to land, the drag force exerted on the wings was
dramatically decreased and there was too little lift on the right wing to remain
stable and the probability of a safe landing became highly improbable, if not
impossible. It then banked sharply starboard without recovery.10

As the inboard fuse
pin broke the structural integrity of the 3rd strut was compromised.
The shift in weight of the structure caused the outboard mid-spar fuse pin to
be eccentrically loaded and coupled with the existing hairline fractures this resulted
in its failure. Subsequently, the upper link and then the diagonal brace were
both breached leaving only the side brace attached. The almost simultaneous
failure of this component resulted in the dislocation of the 3rd
strut from the wing which collided with strut engine no. 4 in an outward and
rearward direction 9 before falling several thousand feet to a
lake below the flight path.

However,
in reality things took a different path and the dislocation of the strut from
the wing did not go as engineers would have hoped. Although not all parts of
the number 3 strut were located and most notably missing was the inboard
mid-spar fuse pin, engineers had since analysed the evidence to give the most
probable failure scenario. Soon after its departure, at 17:27 UTC, witnesses on
ground heard a sharp, loud bang as the aircraft continued to climb through 6500
ft. which we know was the point at which the inboard fuse pin fractured.
Because the pressure is proportional to height above the surface of the earth
as the plane climbed, the pressure applied to the pin of constant volume is increased
meaning the net force became so great that it exceeded the ultimate tensile
strength of the material causing it to rupture. The varying cross-sectional
areas of the bottle bore fuse pins used (shown right 6) is also a feature that was implemented so
that in the event of a failure, the fracture would be located at the
interference of the wing lugs and the mid-spar fittings. However, shortly
before the crash in Amsterdam, it was found that these are often to blame for
initiating fatigue cracking and the pins were ordered to be replaced. Despite
this, the 747 jet that was involved in the crash was one of the few that hadn’t
had the bottle bore pins replaced which meant that with increasing pressure the
microscopic fractures in the metal became epicentres for the stress, eventually
causing it to fracture due to the heightened constant fatiguing 7. The fatigue crack that is suspected to
have caused the accident “was up to 4 millimetres in depth and encompassed
about 50 % of the inside circumference” 8.

In an ideal world,
the departure of the engine pylon should have been a clean breakaway as the
original Boeing 747 aircraft at the time were designed to meet a number of
requirements from 14 CFR, Part 25.571, Amendment 0. This stated that in the event
of a single component, of paramount importance to the structural integrity of
the plane, being compromised it “would not result in catastrophic failure or
affect the flight characteristics of the airplane”5. Instead, the external forces applied would
be distributed out across remaining components such that the aircraft will
remain airborne and the safety of passengers is not undermined.

4  The
image shown above gives a schematic of the 747 engine-to-wing attachments.

The engine strut of
a Boeing 747 such as flight 1862 is a highly complex mechanical torque box
designed to connect the engine to the wing through 5 places. 3 of these points
of contact are diagonal links or braces acting as shock resistors, each with
individual fuse pins, whilst the other 2 come in the form of mid-spar fuse
pins. At the time, the 2 fuse pins incorporated into the forward end of the
upper link and aft end of the diagonal brace were designed to rupture at
slightly lower applied loads than others in order to ensure the controlled
separation of the pylon from the wing.3

Analysis The
initial and overriding cause of the crash was the gradual failure by fatigue of
the mid spar fuse pin on board the number 3 engine strut of the aircraft. A
structural fuse pin is essentially a hollowed-out pin intended to provide a
point of failure when a maximum load is applied2. The maximum load applicable to a fuse pin
is determined by machining out the centre of a cylindrical metal tube.
Normally, when applying a metal to a mechanical situation a tempered alloy is used
to increase the modulus of elasticity, so it will return to its shape without
plastically deforming when an external force is applied. However, the
construction of fuse pins is an exception; in the past Boeing design them so
that they are brittle such that when a force is applied that meets the maximum
load, they will simply snap at the point of contact without bending. The
maximum load of the pins was always designed to be less than that of the
surrounding wing materials and fittings so that when a structural overload occurred,
this allowed for the clean break away of the engine strut without damage to the
aircraft, in theory.

Less than 10
minutes after take-off, the impending doom of the aircraft became clear after a
series of unfortunate events caused by both mechanical and pneumatic system
failures. This led to separation of the 3rd and 4th
engine pylons, hence resulting in almost total loss of the plane as it
catapulted towards earth1.

At least 46 people
laid victim to the disaster of which 3 were the crew members on board the
plummeting plane. A further 26 were reported injured and although official
statistics claims the death toll stands at 46, due to the large number of
illegal immigrants laying claim to this area the exact number of deaths is
still in dispute.1

Intro On the clear dry afternoon of October 4th 1992,
at around 17:20 UTC, El Al Israel Airlines flight 1862 departed from Schiphol
Airport in Amsterdam heading for Ben Gurion International Airport, Tel Aviv.
Less than 15 minutes after take-off, the Boeing 747-200 aircraft nose-dived
from the sky into 2 high rise apartment blocks in the suburbs of Amsterdam
after travelling a mere 13 miles. 1