Flying Dry - Air Tahoma Fuel Starvation - Case Study Example

Flying Dry - Air Tahoma Fuel Starvation In modern aviation, the turbine has become a staple. Modern jet engines take advantage of the turbine’s ability to convert fluid movements to mechanical energy, and many use complex electronic fuel balancing systems to ensure that these turbine engines function optimally—systems that may become prone to mechanical or electronic failure as well as operator error. Ensuring proper operation of aircraft that utilize this technology requires a combination of maintenance, adherence to prescribed preflight guidelines for operation, and correct operation by the captain and crew of the aircraft. One type of turbine engine error that may occur is fuel starvation. This type of failure occurred in the August 2004 crash of the Air Tahoma Flight 185, in which the Convair 580 twin engine turboprop was destroyed on impact only one mile short of the runway, resulting in the death of the first-officer and damage to surrounding property (Aircraft Accident Report). The history and details of the Air Tahoma Flight 185 crash, the cause of the accident, and the relevance to current safety issues are each important in learning from this crash and taking preventative measures against this type of incident in the future. Air Tahoma, a spin-off from Cool Air, Inc., was a Columbus based father-son operated company that was looking to grow and expand its current fleet of thirteen turboprops. Like many small and ambitious companies before them, there is some speculation that in the hurry to expand critical safety checkpoints may have been relaxed. The company had recently contracted with DHL as freight parcel delivery company, and Flight 185 was scheduled for a routine roundtrip flight from Memphis to Cincinnati/Northern Kentucky International Airport when the crash occurred (Pilcher, 2004). The company had previously had several run-ins with federal safety inspectors before the crash, as records show, including citations for maintenance problems three times in the previous four years, including one resulting in a $5000 settlement for problems in providing an airworthy aircraft by the company (Pilcher, 2004). Air Tahoma operated two types of twin turboprop planes, the Convair 240 and the Convair 580 (Pilcher, 2004). Unlike the much larger much larger Boeing 727s, DC-8s and Airbus 300s operated by the main local carrier for DHL at the time, Astar Air Cargo, these are small aircraft capable of holding only fifty-six passengers, but more commonly used for transport (Frawley, 1998). These aircraft are converted from the original 1950s and 1960s model Convair CV-340 or CV-440 aircraft in which the two piston engines have been replaced by Allison 501 D13D/H turboprop engines and an enlarged vertical fin and modified horizontal stabilizers have been added to the aircraft. Air Tahoma Flight 185 was an example a Convair 580, converted in 1967 from a Convair CV-440. The conversions to the aircraft used by Air Tahoma were performed by Pacific Airmotive on behalf of the Allison Engine Company a number of years before the incident, with no recorded above average instance of mechanical failure (Frawley, 1998). There is some speculation that the company’s safety policies should have been addressed before the Flight 185 incident; however, the company rebutted that claims made against them were the product of a disgruntled former employee (Pilcher, 2004). In its sudden out of control descent, Air Tahoma Flight 185 took the tops out of a grove of pines at the World of Sports golf course and plowed into a tree across the sixth fairway less than thirty seconds before its scheduled one a.m. landing time, only one mile from Runway 36R at the Cincinnati/Northern Kentucky International Airport (Pilcher, 2004). Local emergency rescue personnel were on the scene shortly after Flight 185 went down. The pilot walked away from the crash, and was found in a distressed state talking by phone with company dispatchers on the nearby fairway and taken to St. Luke Hospital West. The co-pilot’s gnarled body was found tangled in trees nearby when rescue workers arrived on scene. After the crash, a great deal of speculation went on, with the pilot unclear of the event that had caused the crash and NTSB’s investigation team on the scene (Pilcher, 2004). The National Transportation Safety Board (NTSB) report was officially released in May 2006, giving details on the crash of Air Tahoma Flight 185 and listing the primary cause of the crash as fuel starvation event caused by the captain’s failure to adhere to established procedures for usage of the fuel crossfeed operation, resulting in starvation of fuel from the left fuel tank (NTSB, 2006). Fuel starvation is distinct from fuel exhaustion, which would imply that no fuel was available in either tank. Fuel starvation refers to a condition where the requisite fuel is available on the aircraft, but there is a supply problem which either fully or partially prevents the fuel from reaching the turbine engine. Blocked fuel filters, fuel tank mechanical failure, problems with tank selection in multiple tank systems, and most commonly water-contaminated fuel—where water, having a higher specific gravity than fuel is drawn to the intakes in the lower part of the tank and delivered to the engine—are common causes of fuel starvation (FAA, 2010). In the case of Air Tahoma Flight 185, the output pressure settings on the fuel boost pumps combined with the open crossfeed valve, left intentionally open by the captain against standard protocol, resulted in both engines drawing fuel from the left tank. The fuel not used by the engines was transferred into the right tank to compensate for the pressure differential building between the boost pump. As the fuel became exhausted, fluid air was drawn into both turbines, extinguishing the flame in the combustion chamber in a dual-engine flameout event (NTSB, 2006). Normally, the pilot can recover from a flameout event by restoring the fuel and restarting the engine; however, accidents involving these events normally occur at low power settings, such as during descent, where time can be the limiting factor in recovery (FAA, 2010). When the flame-out occurred in both engines of Air Tahoma Flight 185 at low altitude, on approach to the runway, the captain and crew did not have sufficient time to restore fuel and restart the engines, resulting in the crash. According to the NTSB crash report, the crash of Air Tahoma Flight 185 was entirely preventable. There was no evidence of system or structural failures. There was also no meteorological condition or outside event that contributed to the crash. The report attributes the cause of the event to the captain’s inadequate preflight planning, his subsequent distraction during the flight, and his late initiation of the in-range checklist (NTSB 2006). The flight crew’s failure to monitor the fuel gauges and to recognize that the airplane’s changing handling characteristics were caused by a fuel imbalance. The captain failed to file the preflight load manifest, in compliance with federal regulations, though an unsigned copy was found in the wreckage in which the captain had used improper calculations to determine that the flight was actually overweight. Though the plane was, in actuality, within takeoff limits, the captain allowed take-off thinking the aircraft was overweight—a gross breech of federal regulation. The CRV recording shows that the captain was preoccupied with completing weight-balance calculations, ignoring multiple warning signs, including comments by his copilot on the poor balance and unusual handling of the aircraft. Loss of power to the onboard CRV system in the last moments before the crash obscure the final details, though the recordings show that the captain’s preflight actions and distraction during the flight are primary causes in the crash (NTSB 2006). As a result of the crash of Air Tahoma Flight 185, the NTSB reiterated their former recommendation that CVR and in-flight imaging systems be installed and fitted with independent power sources. Specific recommendations for Convair 580 operators included the recommendation to set the left and right fuel boost pump output pressure settings on their airplanes to the same setting. Because the captain, upon questioning, had admitted that his decision to go against protocol for the CV-580 and leave the fuel tank shutoff valve open had been intentional and based on the preconception that valves on this particular aircraft had a tendency to fail, preventing to the use of fuel, details of the report were also recommended to be issued to all principle operators and inspectors of these aircraft in an attempt to eliminate this misconception (NTSB, 2006). Though a public hearing was not held for this accident, the accident publically damaged the reputation of Air Tahoma. Despite this, Air Tahoma continued to operate its flight routes until it closed its doors in 2009 after a second CV-580 crash that killed three crew members (Flight International, 2007). CV-580 aircraft are still relatively common in both military and civilian aircraft worldwide. Convair 580 aircraft have been involved in twenty-four accidents or crashes since 1963 involving one hundred and ninety six fatalities, according to the Aviation Safety Network. Since 1977, there have been one hundred and fifty six accidents or incidents involving Convair 580s in America according to the Federal Aviation Administration (Pilcher, 2004). The crash of Air Tahoma Flight 185 is an important milestone in turbine engine accident investigations, because it illustrates the potential susceptibility of turbine engines to pilot error. Particularly in older aircraft, and converted models, such as the CV-580, it is important that the pilot carefully completes preflight maintenance and procedures and remains aware of instruments at cruising altitudes and speeds in order to prevent these problems from surfacing at descent, when the engines are running at lower power setting and there may not be sufficient time to recover from a major engine event. Familiarization of captain, co-pilot, and crew with emergency recovery methods, such as the FAA published recovery method for flame-out events, in their particular aircraft is often underemphasized, but, as this incident shows, they are critical to improving aircraft safety. References Airplane Turbofan Engine Operation and Malfunctions: Basic Familiarization for Flight Crews. (2010). Federal Aviation Administration (FAA). < http://www.faa.gov/aircraft/air_cert/design_approvals/engine_prop/media/engine_malf_famil.doc.> Crash During Approach to Landing Air Tahoma, Inc., Flight 185 Convair 580, N586P. (2006). Aircraft Accident Report. National Transportation Safety Board (NTSB), 1-67. Directory: World Airlines. (2007). Flight International, March, 67. Frawley, Gerald (1998). Convair CV-540, 580, 600, 640 & CV5800. The International Directory of Civil Aircraft 1997/98, Aerospace Publications, Fyshwick ACT, 86. Pilcher, James (2004). Father-son airline flies for major cargo firms Columbus-based outfit operates 13 turboprops. The Cincinnati Enquirer. August 14 Edition. Retrieved from Pilcher, James (2004). Cargo Plane Wreckage Yields Few Early Clues. The Cincinnati Enquirer. August 14 Edition. Retrieved from Read More