Jacob Hobbs
Nowra High School
Industrial Arts
Engineering Studies
Aviation – Assessment Task 3
By Jacob Hobbs
Teacher - Mr Hunt
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Jacob Hobbs
Introduction
This report will investigate the British Airways Flight 5390, which was scheduled to fly from
Birmingham Airport in England, to Malaga in Spain on the 10th of June, 1990.
The BAC One-Eleven left Birmingham Airport at 7:20 am with 87 people on board, 81
passengers and 6 crew members. Take off proceeded as normal, and ascension to Flight Level 140
was uneventful. Once cleared to climb to the cruising level, the Pilot (Tim Lancaster) and Co-Pilot
(Alastair Atchison) unbuckled their shoulder harnesses and began to relax into the flight as the
Autopilot brought the plane up to the cruising altitude. It was at 7:33 am (13 minutes into the flight),
as the plane flew through 17300ft that the pressure difference became too much and the pilots
windscreen aperture (left side) blew out, causing an explosive decompression which caused a
condensation mist to form throughout the cabin, blew the flight deck door inwards and across the
radio and navigation consoles and sucked the Pilot out of the gaping hole. The pilot’s leg caught the
control column, causing the plane to come out of Autopilot and into a dive. Stewards ran into the
flight deck and held onto the pilot, whose body was pressed against the flight deck roof from the
ram effect of 560km/h wind. The Co-Pilot the struggled the regain control of the dive. When he did
regain control, he remained in the dive so as to get out of the high traffic air lanes which they were
passing through and to get to a lower altitude fast, as at this high altitude there is little oxygen and
the BAC One-Eleven isn’t equipped with oxygen devices for all passengers.
The Co-Pilot reached Flight Level 110 and re-engaged the Autopilot. He then attempted to
make a distress call but was unable to hear their reply due to the great noise of gushing wind in the
flight deck. It wasn’t until they reached 280km/h that the radio responses were legible, and the CoPilot was vectored into Southampton Airport. The Co-Pilot raised concerns about the length of the
runway as, generally, the BAC 111 requires 2500m of runway, when under the maximum landing
weight (39460kg), but at Southampton Airport there was a maximum of 1800m and the aircraft was
over its weight (40725kg) as it still was full of fuel and the BAC 111 isn’t equipped for fuel dumping.
The Co-Pilot had no choice ad was forced to attempt the risky landing and hope that the tyres
wouldn’t explode. The BAC 111 landed at 7:55 am, and all passengers were evacuated. Fire crew
recovered the Pilot from where he was hanging and he was taken to Hospital, where it was found
that he sustained only fractures to his arm and wrist, a broken thumb, bruising, frostbite and shock.
All other passengers and crew were fine except for one steward who sustained cuts and bruises on
his arm from holding onto the pilot’s legs.
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Jacob Hobbs
Identification
The aircraft in question was a BAC One-Eleven 528FL, registered as G-BJRT. This aircraft was
manufactured in 1977 by the British Aircraft Corporation (BAC) Ltd. From its time of manufacture it
had spent 37724.07 hours in flight, and still had a total of 41 hours until its next mandatory
maintenance check. In this flight, the aircraft was well under its maximum capacity with only 87
passengers and crew on board (81 passengers, 6 crew); the BAC One-Eleven has a maximum seating
capacity of 119.
Wing Span
28.5m
Overall Length
32.61m
Overall Height
7.47m
Fuselage Diameter
3.4m
Economical Cruising Speed
742km/h
Stall Speed (no flaps)
195km/h
Max Cruise Altitude
40000ft
Max Take Off Weight
44000kg
Actual Take of Weight
42905kg
Max Landing Weight
39460kg
Actual Landing Weight
40725kg
Maximum Wing Loading
472kg/m2
Maximum Power Loading
424.7kg/kN
Development
The dream of flight has haunted people for hundreds of years. Before the first successful
manned flight there were many attempts which failed for various reasons. Many designs failed as
they were utterly absurd, where others only failed as at that time the materials required to make the
design work weren’t available.
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1000 BC – the Chinese developed kites, which were the first man-made objects to fly and be
controlled.
1485-1500 – Leonardo Da Vinci designs various flying machines, which didn’t work at the
time. Since then many have been verified to have been able to work, but only didn’t in
Leonardo’s time as he didn’t have the resources available to make them strong or light
enough.
1783 – The next design was the lighter than air, Hot Air Balloon. These two men were the
first men ever to ‘fly’.
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1783 – Two men fly the first ever hydrogen balloon.
1895 – Biplane gliders developed.
1903 – Wright brothers fly first manned, powered, sustained and controlled flight in a
heavier than air machine. The flight lasted 9 seconds. The aircraft was made of timber and
canvas.
1909 – French Aviator makes the first crossing of English Channel in a wooden aircraft.
1926 – First free flight of a liquid fuelled rocket.
1930 – Frank Whittle invents jet engine.
1933 – Boeing 247, the first modern airliner flies. This aircraft was one of the first to
incorporate anodised aluminium, which gave a light weight design but is still very strong.
1947 – Charles Yeager flies the Bell X-1 and is the first man to travel faster than the speed of
sound.
1957 – Soviet Union launches first man made earth satellite, the Sputnik 1. One of the first
aircraft to utilise composite materials and ceramics in the design to get better strength,
durability and heat resistance whilst not gaining excessive weight.
1961 – Yuri Gagarin is the first man in space.
1969 – Neil Armstrong and Edwin Aldrin Jr. are the first men on the moon. By this time,
many aircraft are using composite, ceramics and high grade metals (e.g. titanium) to achieve
the properties which the aircraft demands.
2000 – First crew arrives at the International Space Station.
This timeline shows how advances in flight quickly progressed after the first flight in 1903.
Within 6 years of the first 6 second flight, aircraft had developed enough to be able to cross the
English Channel. In a mere 30 years flight had become commercial and was available for anyone, and
after only 44 years, flight had progressed from a single piston engine, to a high speed jet engine
which was capable of breaking the speed of sound. And finally, after the first flight of only about 4m
high, within 66 years man was able to produce a vehicle which could travel the 1738km to the moon.
The advances in flight were extraordinary and have allowed people
Thrust
The BAC One-Eleven 528FL is powered by two low-bypass Rolls-Royce Spey 512-14DW
Turbofans. The Spey engines have been made by Rolls-Royce for over 40 years, and have been varied
for use in varying styles of aircraft, from commercial aircraft to military aircraft (F-4K Phantom), and
even converted into turboshaft variants for use in ships (Royal Navy’s Type 23 Frigates). The versions
used in the BAC 111 are 5.2m long, have a diameter of 1.09m and have a dry weight of 1856kg.
These engines can each produce a maximum take-off thrust of 55.8kN, and a maximum continuous
thrust of 51.53kN.
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They consist of:
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Intake - 825.5mm diameter fan.
Bypass Air – 0.64:1, bypass ratio, put these engines into the low-bypass category.
Compressor - axial flow, with a 5-stage low pressure section and a 12-stage high pressure
section.
Combustors – 10 can-annular combustion chambers.
Turbine – 2-stage low pressure turbine and a 2-stage high pressure turbine.
Exhaust – exhaust cone.
These engines are mounted at the rear of the aircraft, beneath the T-tail shaped elevators. This
configuration was chosen for the BAC One-Eleven as by having the engines at the back of the plane
they were able to have them closer to the aircrafts centre of thrust, and therefore cause less power
yaw in the case of single engine failure. Also being further from the cabin, it gave a quieter
experience for passengers.
Jet engines work in a very simple manner and have only one moving part. They work by firstly
sucking air in through the intake at the front of the engine. This air is then compressed in the
compressor of the engine. The compressor does this by accelerating the gases (due to Bernoulli’s
Theorem “high speed = high pressure”) through the high and low pressure sections of the
compressor. This compressed air is then combusted in the combustion chamber, which can be an
annular or can-annular configuration (Can-annular in BAC OneEleven). This combustion is done by squirting gaseous jet fuel into
the high pressure air and igniting it with a small flame. This
combustion further increase the speed of the air and it is fired
from the end of the combustion chamber and channelled onto the
turbines. In the BAC One-Eleven three are 3 turbines: a high pressure
turbine, a low pressure turbine and a free turbine. The high and low pressure turbines power their
respective compressor sections, whereas the free turbine is used to power the fan on the front of
the engine. The remaining gases are expelled out the back of the engine creating 61% of the total
thrust. The other 39% is created by the low bypass fan which is powered by the free turbine. This fan
sucks air in and around the engine for cooling and for extra thrust. The engine is very simple as the
only moving part is the drive shaft through the middle which connects to the compressor blades, the
fan and the turbines, so all move as one. Bypass engines are very efficient compared to those
without any bypass air.
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Method of Lift
The BAC One-Eleven is a
general commercial aviation aircraft,
and therefore relies on its wings for
lifting the entire weight of the aircraft.
The wings utilise Bernoulli’s theorem
and Newtons 3rd law of motion to create an
upwards force, or Lift. Bernoulli’s theorem states that “an increase in fluid velocity results in a
decrease in pressure, and a decrease in velocity causes a higher pressure”. This principle relates to
the aerofoil shape of the wing as the camber of the upper surface of the wing causes the airflow
over the top of the wing to accelerate so that when the top and bottom flows meet at the trailing
edge they are joining back at the same point to which they left at the leading edge. As this high
velocity air causes a low pressure on the top and the relatively low velocity air on the bottom causes
a higher pressure, it causes the wing to be ‘sucked’ up towards the lower pressure; resulting in an
upwards lifting force.
Newtons 3rd Law states “for every action there is an equal and opposite reaction”. This
relates to the lifting force of the wing as the angle of attack which the wing is cutting through the air
at means that the underside of the wing is hitting the airflow at an angle and forcing this air
downwards. This downwards force results in an upwards resultant force on the wing.
The aircraft has a total wingspan (tip to tip) of 28.5m and a fuselage diameter of 3.4m, so
this gives 25.1m of actual wing length. The wing is sweptback 20o at the quarter chord (the line
drawn one quarter of the total chord length, from the leading edge). The chord at the root of the
wing is 5.11m, and 1.65m at the tip. The total area of the wing surface is 95.78m2. From these
lengths and areas we are able to determine the aspect ratio of the BAC One-Eleven’s wings:
𝑏2
𝑊𝑖𝑛𝑔𝑠𝑝𝑎𝑛2
𝑨𝒔𝒑𝒆𝒄𝒕 𝑹𝒂𝒕𝒊𝒐 =
=
𝑆
𝐴𝑟𝑒𝑎 𝑜𝑓 𝑃𝑙𝑎𝑛𝑓𝑜𝑟𝑚
𝐴𝑅 =
28.52
95.78
𝐴𝑅 = 8.48
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Jacob Hobbs
Materials Used
Modern aircraft use many materials in their construction to create a strong and reliable
structure which, when properly maintained can carry out all tasks required and withstand any
excessive forces.
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5 ply Polyvinyl-Butyl Glass
The windscreen of the BAC One-Eleven uses a 5 ply construction of polyvinylbutyl (PVB) glass. This lamination process produces a stronger construction to
withstand impacts such as bird strikes, and the outward force of the pressure
differential when at altitude. The five layers of glass are laminated together with
the PVB material. The image on the right demonstrates how the individual layers
are laminated together. The innermost layer of glass in the windscreen is low
tempered, meaning it has been heated and then rapidly cooled. This process
causes the glass to form smaller crystals and therefore breaks into much smaller
and less sharp fragments when it is broken. This tempered glass is used on the
innermost layer to prevent shards of glass entering the flight deck in the case of
bird strikes. This tempered glass is also much stronger than the other, annealed
glass sheets and therefore adds strength to the windscreen. Tempered glass can withstand
pressures of up to 9400psi, much higher than the pressure difference experienced in the
aircraft.
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Aluminium Aircraft Skin
The BAC One-Eleven uses 2024-T3 aluminium for the external skin structure for the
pressurised aircraft. The aluminium provides an excellent fatigue strength, fracture toughness
and notch sensitivity. Aluminium is chosen for the skin over other metals as it is a very strong
but light material. The strength of aluminium also increases as the temperature decreases. This
quality is very desirable in aircraft as the temperature decreases as altitude increases.
Aluminium is also a very easy material to work with as it is easily machinable. It is able to be
milled, turned and bored. It can also be rolled, stamped, forged, hammered, riveted and welded
to achieve the desired shapes and give maximum strength. This also allows the skin surface to
be easily repaired or patched if required. The most desirable attribute which aircraft designers
require is the corrosion resistance which is provided by aluminium. When exposed to oxygen,
aluminium forms a thin layer of aluminium oxide on the surface of the metal which is
impervious to corrosion. This thin layer of outer corrosion protects the structural integrity of
the inner material.
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Tyres
The tyres of the BAC One-Eleven undergo many forces and temperature changes and must
therefore be able to withstand these stresses. The tyres are made of reinforced rubber layers.
The inner layer is reinforced with steel wire beads which are connected tightly to anchors so
that the tire has a snug fit on the wheel. The inner plies are reinforced with nylon cord, angled
diagonally to create balanced strength. These layers are also reinforced with fabric breakers
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Jacob Hobbs
which are designed to distribute shock and impacts over a wider area, and increase the strength
of the tyre. The outer ply’s of the tyres and the sidewalls are thick rubber with heat welded
nylon cords and shredded wire embedded in it. This extra strength on the exterior is intended
to protect the tyre from moisture, bruises, snags and cuts.
The tread pattern on the tyres is designed to have maximum stability in high crosswinds,
channel water away to prevent hydroplaning, and have maximum friction for high braking
forced. The tyres are protected by heat fuses which detect excessive temperatures and prevent
explosions by deflating the tyre safely. This minimizes damage to the aircraft.
Accident Investigations
After the accident a full scale investigation was undertaken to determine the cause of the
accident and the faults which may have caused the deaths of 87 people if it wasn’t for the skilled
crew. The investigation determined that it was an accumulation of many faults which led up to the
accident. The windscreen in the BAC One-Eleven is unique is fitted from the outside and relies solely
on the 90 bolts to hold the windscreen in position, rather than the windscreen being fitted from the
inside and the pressure difference holding the windscreen in the frame. Ultimately, the windscreen
failed as it was held in place by the wrong type of bolts, which were too small in diameter. The many
factors which led to the accident are:
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The windscreen was originally fitted with the wrong bolts (A211-7D).
When finding new bolts for the windscreen, the engineer, rather than checking the parts
catalogue, went to the parts store and found a bolt which matched the A211-7D by sight and
ended up selecting many A211-8C’s as well as some more A211-7D’s . The A211-8C’s were
0.66 mm too small in diameter, and the A211-7D’s were 2.5mm too short.
When told that the BAC One-Eleven’s windscreen actually used A211-8D bolts, not the A2118C which he had selected, the engineer ignored what he was told and continued his job.
When fitting the bolts, the engineer failed to notice that the bolts he was installing left an
abnormally large amount of countersink
showing. This can be seen in the image
below.
When installing the bolts, the engineer
used an uncontrolled torque screwdriver
which wasn’t properly calibrated and
therefore, the bolts were only partially tightened.
Finally, a safety lift which was used to lift the engineer to the windscreen height was
incorrect and provided inadequate access and visibility of the job. This added to his difficulty
in seeing that the bolts he had installed were incorrect.
Correct Bolts
Incorrect
Bolts
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Part Number
A211-8D
A211-8C
A211-7D
Shank Length (mm)
20.32
20.32
17.8
Diameter (mm)
4.73 – 4.81
4.07 – 4.16
4.73 – 4.81
Thread Size
10 UNF
8 UNC
10 UNF
Jacob Hobbs
The main sources of error which caused this accident were the improper work practices which
were being undertaken. Normally an engineer must check the maintenance manual to determine
which parts must be used, and then select these parts from the store with assistance from the parts
store manager. These parts are found in an uncontrolled carousel which has cabinets of loose bolts
and other fixings. Once these bolts are removed from their package they are unidentifiable
individually and therefore make it more difficult to determine what part is what. Also, after
completion of maintenance, a secondary check is normally undertaken on vital systems and parts
(such as the windscreen).
After completion of the accident analysis, a number of new rules and procedures were
implemented to reduce further accidents. It is evident from the investigation that the practices
which the engineer undertook, although unsafe, were common in the British Airways maintenance
hangar and had gone unnoticed due to insufficient monitoring and management of the processes
which the engineers were undertaking. After this investigation it was recommended to BA that they
increase their management staff to accommodate for the engineers. Also, tasks such as the
windscreen replacement were made ‘vital’, meaning that they must be checked by an external
engineer to ensure that the job was properly completed.
The investigation also led to many aircraft fixings being marked with their serial number on the
head. This allows the user to easily determine which bolt is which and therefore reduce the risk of
such incidents occurring again where the engineer installed the wrong bolts. Finally, the last
development which was introduced due to the investigation of flight BA 5390 was that all new
pressurised aircraft have windscreens which are installed from the inside. This means that when at
altitude, the pressure difference on the inside of the airplane pushes the window outwards and into
the wedge shaped window frame, locking the window into the frame. This is much safer than the
method used in the BAC One-Eleven, which relies on the 90 bolts to secure the windscreen from the
outside. These new regulations and safety measures greatly decrease the chance of such accidents
occurring again in the future.
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Jacob Hobbs
Load Calculations
The BAC One-Eleven’s wings have a maximum Wing Loading of 472kg/m2. This means that
for every square metre of wing area there is 4.72kN (472 × 10 = 4720𝑁) of force produced. This
means, as the total wing area of the aircraft is 95.78m2, that the total area of the wings is producing
452.08kN (95.78 × 4.72 = 452081.6𝑁) of lifting force. This means that
the wings maximum weight is 45208.16kg, even though this aircraft is
limited to a maximum weight of 44000kg. This is done to allow for extra
lifting force in case of emergency and help in aircraft
manoeuvrability. In the case of BA Flight 5390,
the aircraft took off at a weight of 42905kg, well
under the maximum load of the aircraft.
The BAC One-Eleven has two Rolls-Royce Spey 512-14DW
engines. Each of these engines can produce a maximum of 55.8kN of
force for a limited time, or a maximum of 51.52kN continuously. This
means that there is a total thrust power of 103.04kN continuously.
The Drag of an aircraft is difficult to determine as drag is proportional to the velocity of the
aircraft. This means that as the aircrafts speed changes, so does the drag which is acting against its
movement.
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References
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Air Crash Investigations (MAYDAY) - Season 2 Episode 1(Blowout) - Produced by Cineflix
en.wikipedia.org/wiki/British_Airways_Flight_5390
en.wikipedia.org/wiki/BAC_One-Eleven
www.airliners.net/aircraft-data/stats.main?id=54
www.bac1-11jet.co.uk/
www.dmflightsim.co.uk/bac_1-11_history.htm
en.wikipedia.org/wiki/British_Airways_Flight_5390
www.aaib.gov.uk/cms_resources.cfm?file=/1-1992%20G-BJRT.pdf
www.aaib.gov.uk/cms_resources.cfm?file=/1-1992%20G-BJRT%20Append.pdf
www.jet-engine.net/civtfspec.html
planecrashinfo.com/
www.nytimes.com/1990/06/11/world/4-miles-over-britain-pilot-is-sucked-out-crew-holdson-tight.html
agrino.org/nchiras/research/pubs/thesis/chapter2.pdf
www.easa.europa.eu/certification/type-certificates/docs/engines/EASA-TCDS-E.064_Rolls-Royce_Deutschland_Spey_500_series_engines-01-05122008.pdf
www.ehow.com/facts_5748737_aluminum-used-aircraft-skin_.html
adg.stanford.edu/aa241/structures/structuraldesign.html
www.centennialofflight.gov/essay/Evolution_of_Technology/composites/Tech40.htm
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