The report will be giving a brief introduction on the fuse pin. Following up by an in depth investigation on the damages done to EL AL flight 1862 like the fuse pin, the right wing leading edge, the lug of the pylon, aerodynamics and also the hydraulic systems of the aircraft. The report will also consist of a investigation on how did the aircraft crash when it was able to fly with 2 engines. This investigation will include the data from the flight recorder data, and summarising of the investigation of damages done. Lastly, the report will end with the conclusion and also the recommendations to the structural and maintenance area so that it can be improved
Report on Amsterdam air crash flight EL AL 1862
The purpose of this report is to inform the audience about the EL AL 1862 crash that happened in Amsterdam is October 4 1991. Secondly, this report is to evaluate the structural failure that leads to the crash. And finally, this report is to present solutions and modifications to the existing BOEING- 747 so that reoccurrence of the kind of accident will not happen again.
EL AL flight 1862 was a Boeing 747-200 freighter. 4th October 1991, EL AL flight 1862 was meant planned to fly from Schiphol Airport, Amsterdam, Netherlands to Tel Aviv, Israel. 7 and half minutes after takeoff, Pilot's reported that engine 3 and 4 was not in operation. However, the pilot was able to use remaining controls to regain stability of the plane. Pilot immediately contacted the control tower for the longest runway on Schiphol Airport for emergency landing. After 8 minutes of flying after EL AL 1862 regained stability, it began to land at Schiphol airport. The plane started to pitch its nose up to slow the plane down. At this moment, the plane started to roll violently to the right again and this time, the pilot was not able to regain back its stability and therefore crashed into the flats in Bijlmermeer of Amsterdam.
The methodology for this report are the secondary information mostly based on videos from national geographic channel, and websites from manufacturers from of the planes, NSAB(Netherlands Safety Aviation Board) and flight safety foundation that explains the crash and lastly the cockpit conversation of the pilots when it was about to crash.
1.4 scope of report
The report will be covering the structural failure of the fuse pin of the right wing engine pylon ,what caused the fuse pin to break away and what caused the plane to roll violently to the right. In addition to that, recommendations on how can the plane and inspections can be done therefore accidents like this would not happen again.
2.40pm EL AL 1862 cargo arrived from new York
3.00pm loading begins
5.20 flight 1862 has passed security checks
6.00 captain fuchs powers up the 4 P&W engines
6.27 engines at full thrust engines climb to 60500ft. Settles to fly to televeeve
6.30 fire crews race into position to schipol air port where the 747 will arrive in 5 minutes
6.33 air traffic control clears the runway 27 2mins from the belma suburb
6.42 EL AL flight 1862 crashed into the apartment block
2.0 Structural failure of fuse pin
2.1 Fuse Pin functions
The fuse pin is 14cm hollow steel bolt. The function of a fuse pins are to hold the pylon which holds the engine to the wing of the aeroplane. The fuse pin is strong enough to hold the 5 tonnes Pratt & Whitney engine at full throttle. However, the fuse pins are meant to fail at a certain critical point if the vibrations of the engines get too violent due to bird strikes or mechanical seizures. The fuse pin is meant to shear off at both ends of the Fuse pin in order for the engine to fall off the wing harmlessly. (National geographic channel, 2004).
2.2 Breaking of the Lug of engine no. 3
The inboard mid-spar fitting of the pylon fitting of engine number 3 was recovered at Gooimeer. The fuse pin could not be found. Shown in figure 1, the clevis of the outboard lug has failed. According the investigations done by the National Aerospace Laboratory. The clevis of the outboard lug failed and Fractured due to a combination bending and tensile loads which caused the structure to overload. This could only be caused by the metal fatigue of the fuse pin. (FAA , 1994)
Figure 1: Outboard lug of pylon no.3 (Seconds from disasters, 2004)
2.3 Defects of Fuse Pin
A section of the out board wing support fitting (inboard side only) on engine no.3 was recovered at the accident area. The central section of the fuse pin was still intact with the support fitting. The section of the outboard support is sent to the Dutch national aerospace laboratory to conduct a metallurgic investigation of the fuse pin. The laboratory had concluded that the fuse pin sheared off due to metal fatigue. They found a large crack 4mm deep in the fuse pin. To add on to that, the material of the fuse pin has met the chemistry specification. However, the hardness measurements indicator that the tensile strength was about 117ksi, which is lower than the specific range of 126-139ksi. (FAA, 1994)
Figure 2: Section of outboard wing support fitting on engine no.3 (Seconds from disaster, 2004)
3.0 shearing of Engine
3.1 Engine no.3
The cause of engine no.3 to shear off was due to the structural failure of the fuse pin. Fatigue cracks in the fuse pin caused it to fail below allowable stress. Due to fatigue failure, the fuse pin did not break off at both ends, but it's broke off at only one end as illustrated at figure 3. (seconds from disaster, 2004)
Figure 3: fuse pin breaking off on pylon no.3 (seconds from disaster, 2004)
3.2 Engine no.4
There was no sort of structural failure or fatigue failure on engine 4. However, the reason why engine no.4 sheared off is because as engine no.3 sheared off, it shoots forward and in a split second, it fall backwards hitting engine 4. As illustrated in figure 4. ( seconds from disaster, 2004)
Engine 3 flew backward to shear off engine 4
Figure 4: Engine 3 shearing off Engine 4 (seconds from disaster, 2004)
4.0 Damage to the right wing
4.1 Damage of the Leading Edge
The right wing's leading edge has been torn off. The area of damage is about 10 meters of the leading edge. This is 1m away from the inboard of pylon no.3 to 1m away from the outboard of pylon no.4. The cause of this is because when engine 3 has been sheared off from the wing, the engine shot forward and in a split second, it flew backwards resulting in shearing off engine no.4 together with 10m of the leading edge. Figure 5 shows the damaged area of the right wing's leading edge. ( FAA , 1994)
Damaged Leading Edge
Figure 5: Estimated damage to the leading edge (FAA, 1994)
4.2 Damage of the Right Wing Hydraulics system
Due to the separation of Engine no. 3 and no.4, hydraulics systems no.3 and no.4 on the right wing were severely damaged. Due to this, hydraulic systems no.3 and no.4 have stopped functioning. Therefore, hydraulic pressure from hydraulic system no.3 and no. 4 was not available for the primary flight controls for the wing. This will put more strain on remaining hydraulic controls. Figure 6 shows a table on which flight control systems have been lost. (FAA, 1994)
Figure 6: Remaining and lost Hydraulics systems (FAA, 1994)
4.3 Damage done to the Aerodynamics of plane
Since 10 meters of the right wing leading edge has been torn off, a huge amount of air disruption is acted on the right wing. This will cause a difference in lift between the two wing causing EL AL 1862 to roll violently to the right.
5.0 Analysis on Flight Data Recorder
An analysis from the Flight Data Recorder was done. Based on the altitude and the airspeed, we can conclude the performance of EL AL 1862. At maximum continuous thrust and travelling at a low speed of 270 knots due to the loss of 2 engines, EL AL 1862 was not capable of flying at higher altitude and it will have limited manoeuvring capability. (FAA, 1994)
Performance of EL AL 1862 performance of flight has degraded to about 260 knots due to the increased angle of attack. The plane later decelerated to 256 knots that result in a considerable sink rate. (FAA,1994)
6.1 Conditions of Plane After Separation of Pylon to Wing
After the separation on the pylon to the wing, these are the following condition that the EL AL 1862 suffered from.( FAA, 1994)
Right wing's leading edge severely damaged.
Hydraulics system no.3 and no.4 failure
Limited roll control as there was no outboard aileron available
Right inboard aileron less effective due to the disturbance in airflow by the damaged right wing leading edge.
Engine 1 and 2 have to use high thrust settings
6.2 EL AL 1862 first roll to the right
Due to the loss of the 10m stretch of leading edge on the right wing, the right wing loss huge amount of lift. Therefore, this cause a violent roll to the right side. The reason why the plane was able to regain stability in flight was due to the following 2 reasons. (Seconds from disaster, 2004)
The pilot was pushing remaining controls to the limit to regain stability
According to the Flight Data Recorder, the plane was travelling at a speed of 270 knots. This was enough to generate enough lift for right wing to regain stability.
6.3 EL AL 1862 final roll to the right
After the first roll, pilot was able to recover flight stability only by pushing remaining flight controls to the limit. However, when EL AL 1862 was about to land, it followed normal landing procedures to pitch up the aircraft. By slowing down the aircraft. There was a loss of speed. Therefore the right wing lost its lift which causes the violent roll to the right. At this time the pilot cannot could not regain its stability and therefore crash (Seconds from disaster, 2004). (seconds from disaster, 2004)
The conclusion of this report is that the flight accident of EL AL 1862 was because of a crack in the fuse pin due to metal fatigue. However, I believe that it was enough to crash the plane. I believe that the accident happened due to a series of misfortunate events. From the metal fatigue of the fuse pins, to the engine separation of the right inboard engine which hits the right outer engine and lastly to the 10 meters stretch of leading edge. All this factors add up to cause an misfortunate accident. The crash of EL AL was inevitable as the aircraft was bound to crash once it tries to land as explained at 6.3.
8.1 Structural Improvements
Methods have been implemented to prevent crashes like this to happen again. Fuse pins have been changed to a newer type which has higher resistant to metal fatigue. Figure 7 shows you the difference between the to2 fuse pins. (FAA )
Figure 7: old fuse pin (left) new design of fuse pin (right).
(Fatigue and fracture report in an aircraft engine pylon, 1997)
8.2 Improvements in Maintenance
Maintenance can be improved by using ultrasound detection. Using high frequency sound waves that will penetrate metal, composites, liquid and other materials to locate cracks locate porosity cupping, inspect forgings and detect corrosions.(Ultrasonic testing for aircraft, 1975)
Nederlands Aviation Safety Board, 1994[online], available from: http://www.verkeerenwaterstaat.nl/kennisplein/3/9/39448/ElAl_flight_1862.pdf
Seconds from disaster, Amsterdam air crash, Season 3, episode 2, [video]
2005, Singapore, National geographic channel.
R.J.H. Wanhill and A. Oldersma, 1997, Fatigue and Fracture in an Aircraft Engine Pylon [online] Sheffield, England. Available from: http://www.nlr.nl/id~4823/lang~en.pdf
FAA aero center, 1975,Ultrasonic Testing for Aircraft [online]. Available from: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/5e773d29b1f398e2862569d60074b576/$FILE/AC43-7.pdf