Crash Of United Airlines Flight 232 Engineering Essay

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This is an over view of United Airlines Flight 232. This is about a DC-10 that was having mechanical difficulties and landed at the nearest airport possible. The airport it landed at was a Category 6 airport. This airport was too small for this type of aircraft. The aircraft then landed at full throttle.

Flight 232

United Airlines Flight 232 was en-route from Denver to Chicago on the 19 July 1989. During the flight there was a loud noise that was coming from the tail mounted engine. At the time of the incident the crew heard the noise but did not know that the engine fan assembly had came apart with enough force and severed through the right horizontal stabilizer. In this same area was a 10 inch wide route that all three hydraulic systems shared. When the engine cut through this it caused the aircraft to lose all three hydraulic systems that power all the flight controls on the aircraft. The crew still had control of the other two engines but no flight control power. This would have control the flight surfaces i.e. flaps, vertical and horizontal stabilizers. So with this being realized the crew then started using the throttles to control the aircraft. They powered one engine to full power and throttled the other back. This helped maintain the necessary heading but increased speed greatly for all landing purposes.

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Next the crew found the closest airport that they could land the plane at. The crew found Sioux City Gateway Airport, also known as Colonel Bud Day Field, is located 6 miles south of Sioux City and west of Sergeant Bluff, in Woodbury County, Iowa. This airport is considered a Category 6 airport. Sioux Gateway Airport covers a massive area of 2,460 acres this contains two runways: 13/31 with a concrete surface measuring 9,002 x 150 ft and 17/35 with an asphalt surface measuring 6,600 x 150 ft (US DOT & FAA, 2010).

I could not find any information from date of the accident but for the 12-month period ending April 30, 2006, the airport had 30,726 aircraft operations, an average of 84 per day: 65% general aviation, 19% military and 16% scheduled commercial. There are 67 aircraft based at this airport: 66% single engine, 19% jet aircraft, 13% military and 1% helicopters. This particular airfield is a dual use airport. Meaning that both civilian and Air National Guard use this airport. The ARFF services provided for the airport are provided by the Air National Guard (US DOT & FAA, 2010).

The National Fire Protection Association (NFPA) classifies this as a category six for their current ARFF capabilities. After doing some investigation, and going under the (NFPA 403) there are actually two different category sixes. There is a 6a and a 6b, the purpose for the two different category sixes is for extinguishing agent capabilities. The one big difference that I can tell between the two is that the 6b needs to be able to handle a double decked aircraft. The facility, which is certificated under Federal Aviation Administration (FAA) regulations 14 CFR 139, as an Index B airport (Boucher, 2003). The index is based on the largest airplane with an average of five or more scheduled daily departures; the regulations stipulate the minimum level of firefighting equipment and agents for each index. For SUX, Index B was based on an airplane equivalent to the Boeing 737-200 series and requires a minimum 1,500 gallons of water for foam production. An airport serving McDonnell Douglas DC-10 series airplanes and would require more than double the quantity of fire extinguishing agents required for an Index B airport (Boucher, 2003) .

With that being said and a decent feeling for the ground work of the airfield. I was able to find a video of the plane coming in for its landing. I was very surprised to find one and also very lucky here is a link and I would advice to watch the following link: http://www.dailymotion.com/video/x5yztk_1989-sioux-city-crash_news. The aircraft landing was originally planned for the 9,000 foot Runway 31. There were several difficulties in controlling the aircraft. This made lining up the aircraft in its current condition almost impossible. While dumping all most of the excess fuel if not all, the plane executed a series of mostly right-hand turns (it was easier to turn the plane in this direction) the intention was being able to be easily line up with runway 31. When the aircrew came out of there right hand turns, they were left with an approach on the shorter Runway 22, this was only a 6,600 feet over half a mile shorter, with little or no capacity to maneuver. Fire trucks had already been placed on runway 22, the crash trucks were anticipating a landing on runway 31, this caused a massive scramble as the trucks rushed out of runway 31 over to runway 22 (Conroy, 2005).

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The pilot did his best to continue and try and control the aircraft's loss of altitude by adjusting engine thrust. With the loss of all hydraulics, the pilot was unable to control any kind of airspeed, that being said the sink rate was very high. When it came in for final descent, the aircraft was nearing 240 knots and sinking at 1850 feet per minute, while a safe landing would require 140 knots and 300 feet per minute (NTSB 1990). The aircraft began to sink faster while on final approach and began veering to the right. The very tip of the right wing was the first thing to hit the runway; this began spilling fuel and ignited immediately. The tail section then broke off from the blunt force of the impact and sent the rest of flight 232 bouncing several times. This shredded the landing gear and engines, finally breaking the fuselage into several main pieces. On the final impact the right wing was sheared off and the main part of the aircraft skidded sideways, rolling into its final position over on to its back, and slid to a stop upside down in a corn field to the right side of runway 22 (NTSB 1990). The video of the crash showed the flaming right wing tumbling end-over-end, but if you watched the video it is very difficult to make this out. Major debris from Engine #2 and other parts from the tail structures of the plane, were later found on farmland near Alta, Iowa. The brute force of this crash caused pieces of the aircraft to land approximately 60 miles northeast of Sioux City (NTSB 1990).

This is where things get a little intense. The ARFF's ability to continuously stay on top of the post crash fire near the aircrafts right wing root would be a major factor. The investigation also identified several deficiencies in the current design and operation of the Kovatch A/S32P-18 (P-18) water supply vehicle, the absence of FAA requirements to regularly test fire service vehicles at their maximum discharge capacity, as well as delays in correcting reported deficiencies in Kovatch P-18 fire service vehicles (Kolstad 1990).

There were two ARFF vehicles that were first to arrive at the scene of the accident. They began a mass application of extinguishing foam immediately. The bottom of the fuselage, also known as the bell of the plane was blanketed with foam. The foam blanket temporarily suppressed the fire during the evacuation of passengers and crew (Remember the plane is belly up). According to NTSB pproximately nine minutes after the landing both ARFF vehicles had ran out of water, a P-18 water supply vehicle was positioned adjacent to the two ARFF vehicles, and a 2 1/2-inch hose was connected between the P-18 and each vehicle. When the P-18 water pump was charged to its maximum capacity of 500 gallons per minute, a restriction developed in the vehicle's tank-to-pump hose that stopped all water flow to the two ARFF vehicles (NTSB, 1990). Thus, the airport's primary attack vehicles could not be replenished with water to continue attacking the fire. Two Sioux City Fire Department pumper trucks subsequently resupplied the airport's ARFF vehicles. On a side note we had discussed this very thing about having the local fire department having the ability to replenish an airport in case of an accident and this is a perfect example of a local department that most likely saved the day. The main thing that I could not find was if the local fire department ever trained with the airport crew. However, during this delay of about 8 minutes, no extinguishing agent was applied to the fuselage, and the fire at the airplane's right wing root (the original foaming spot) intensified. Soon thereafter, fire penetrated the cabin, resulting in secluded fires that could not be attacked by exterior fire fighting tactics. This was due to the lack of access to the fire being on the inside of the aircraft. Despite attempts to advance hand lines to the interior of the airplane, the fire intensified inside the cabin and burned out of control for about 2 1/2 hours (Kolstad 1990).

The Kovatch P-18 water supply vehicle has no foam-producing capability, hence why it's a water supply vehicle. As Kolsatd said it is designed primarily to supply water to the primary ARFF vehicles. It is certified by the manufacturer of a water capacity of 2,000 gallons and a maximum water pump discharge rate of 500 gallons per minute (Kolsad 1990). In September 1988, the Iowa Air National Guard purchased the P-18 through the Air Force and placed it in service at SUX. It was learned that during the 2 years after this accident occurred that the Air Force had purchased 210 Kovatch P-18 water supply vehicles. The investigators also learned that some P-18's are based at joint-use airports that are certified by the FAA as having ARFF capabilities in compliance with 14 CFR 139. This was obviously wrong they only had water replenishment capabilities. The water supply vehicle was listed in the SUX airport certification manual, the airport fire chief testified at the Safety Board's hearing that the vehicle had never been tested to its maximum discharge capacity of 500 gpm (NTSB 1990). At this point I tried very diligently to find what are the prerequisites for their vehicle testing frequency (for that specific vehicle from the manufacturer). The only thing that I could find is that they fell under the FAA's regulations. I really wanted to know if that vehicle needed to be tested at full discharge daily, weekly, monthly etc.

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The problem here was that the fire chief relied on the manufacturer's pre-delivery factory tests of the pump's ability to discharge 500 gpm with two 2 1/2-inch lines attached. But no testing of their own was ever done to verify this. Also the fire chief stated that, SUX tested the P-18 weekly at nominal pressure, this was less than 500 gpm. During the National Transportation Safety Board's investigation, the P-18's tank-to-pump suction hose assembly, a soft, 11-inch by 4 1/2-inch inside diameter Gates rubber hose, was removed from the vehicle and examined at the SUX facilities. The full examination showed that the 2-inch internal polyvin 1 Kovatch (manufacturer) stated that the internal stiffener in the soft hose assembly is required to prevent the hose from collapsing (NTSB 1990). Kovatch also stated that the stiffener was installed by a press fit in the center of the hose instead of being welded or made out of a different material. This lead to the examination of the rotated stiffener, this strongly suggests that when the P-18 operator attempted to resupply the both ARFF vehicles by using the two 2 1/2 inch hoses, with the pump set to its maximum operating capacity, there was a momentary high pressure surge had occurred within the tank-to-pump piping system that caused the stiffener to move and rotate to a position that blocked the flow of water to the pump (NTSB 1990). While looking at the susceptibility of the internal stiffener to displace and rotate, the Safety Board found that the stiffener's length was about half the internal diameter of the soft suction hose and in mind this would create a blockage on its own being half the diameter if not just slow the volume of the water to the truck down. The shorter length of the stiffener caused it not to be clamped, this allowed it free to rotate and block the flow of water and it cause it to slide toward the pump intake. This by its self could cause blockage or failure in the system. This caused the Safety Board to be concerned that the design of the P-18, which uses a soft suction hose at a much critical location up stream of the vehicles pumps and this makes it highly susceptible to blockage (NTSB 1990).

Not only in the P-18 is this concept used but in other pumpers manufactured by Kovatch. There needs to be a hose made of more rigid material, this would have null in voided the need for an internal stiffener or an improved design. It is necessary to reduce the chances of hose blockage regardless of operating conditions. Kolstad stated on February 15, 1989, a P-18 operated by the Air Force at Tyndall Air Force Base, Florida, was unable to supply water to an ARFF vehicle during a pumping operation. It was determined that the "A/S32P-18 tank suction line was restricted by a PVC stiffener inside the rubber suction line, and they installed a clamp around the hose and PVC to hold it in place (Kolstad, 1990)." On August 16, 1989, a similar P-18 deficiency was found at Malstrom Air force Base, Montana. Discussions with the Air Force, Kovatch issued Technical Service Bulletin 86-KFT5-P-18-5, dated August 21, 1989. This called for the removal of the tank to pump hose assembly installed on all 210 A/S32P-18 vehicles and this caused for the replacement of the hose assembly with a new tank to pump hose assembly. This one had a 4 inch PVC internal stiffener, much stronger than the original. This caused Kovatch agreed to conduct all the supplying modification kits directly to all air bases whose addresses were provided by Warner Robins Air Logistics Center (Kolstad 1990). August 22, 1989, the Air Force issued a Materials Deficiency Report this caused a one-time test of all Kovatch P-18 vehicles. This would show if the stiffener installed in the hose had rotated laterally 90 degrees or not. The maximum pump discharge rate of 500 gpm, along with the replacement of the faulty 2-inch stiffener with the greater 4-inch stiffener. This allowed 30 days, eight Air Force bases had quickly responded that tests found similar deficiencies to those described (NTSB, 1990).

Now back to the crash. From the lack of proper procedures being followed and running out of agent. Of the 296 people on board, 111 died in the crash. The majority were killed by injuries sustained in the multiple impacts (as you could see by the video), several in the middle fuselage section directly above the fuel tanks died from smoke inhalation in the post-crash fire. I was very surprised that anybody surprised from this crash, from the video I thought everybody was done. This part of the fire burned for longer than it might have but due to the massive delays in the firefighting efforts. Most of the 185 survivors that were seated right behind first class and ahead of the wings. There were many passengers that were able to walk out through the ruptures through the structure. Several cases of individuals got lost in the high field of corn adjacent to the runway until rescue workers arrived on the scene and escorted them to safety (NTSB 1990).

Of the passengers of flight 232: 35 died due to smoke inhalation (None was in first class), 75 died for reasons other than smoke inhalation (17 were in first class), 41 were seriously injured (8 were in first class), 121 had minor injuries (1 was in first class), 13 had no injuries (None were in first class) (Conroy, 2005).

The passengers who died for reasons other than smoke inhalation were seated in rows 1-4, 24-25, and 28-38. Passengers who died due to smoke inhalation were seated in rows 14, 16, and 22-30. A person assigned to 20H moved to an unknown seat and died due to smoke inhalation. One person died 31 days after the accident; the NTSB classified his injuries as "serious." Fifty-two children, including four lap children, were on board the flight due to the United Airlines "Children's Day" promotion. This was very ironic and very sad at the same time to hear. Eleven children, including one lap child, died. Many of the children had traveled alone (Conroy, 2005).

In conclusion I am thankful number one for being able to find the video of this specific accident. With the video I was able to fully understand and see the incident. It just wasn't another "story" out of a book. The interviews with the survivors showed how real this situation was and what was going through their mind during this crucial time.