Casa Grande, AZ, USA
N521A
Bellanca 14-19
The airplane was making a precautionary landing due to a fluid leak (most likely fuel) in the cockpit and had an explosive flash fire in the cabin during the landing roll. The pilot stated that a clear fluid was running down the cabin side of the firewall from an area right of center. The right seat passenger reported that the leak appeared to be coming from behind the instrument panel directly in front of her position. The pilot then pulled back the power slowly and headed for the closest airport. A passenger and the ground witnesses described the touchdown and rollout as normal until an explosion occurred, which filled the cabin with flames and blew the entry door off the right side of the airplane. Witnesses on the ground reported seeing flames coming out of the front-bottom of the aircraft before hearing a "pop" in conjunction with the explosion inside the cockpit. The fabric-over-tubular-steel-frame airframe was thermally destroyed except for the steel components. An examination of the thermal damage patterns disclosed that the most extensive thermal damage appeared to be forward of the right front seat where the passenger reported the fluid leak. Also parts of the metal frame were severely warped, especially on the lower right-hand side near the firewall and below where the instrument panel would be. In addition the bottom braces of the engine mount were warped due thermal damage. Furthermore, there was sooting and heat resultant discoloration on the firewall in the engine compartment. On the topside and on the right-hand side of the firewall red and black discoloration without sooting was evident. The color on the right side of the firewall was a mixture of black and tan, with a little red. On the bottom part of the firewall there was minimal sooting and a tan color. The only flammable fluid lines on the right quadrant of the firewall are the pressure measurement lines for fuel, engine oil, and hydraulics. These Mil-6000 hose lines are connected to firewall and pass-through fittings, that are located almost directly in front of the right seat passenger's location on the upper part of the firewall. On the cabin side of the firewall, three other Mil-6000 hoses connect these fittings to a "3-in-1" instrument panel gage that displays the operating pressure of these three systems. No evidence was found in the maintenance records that these fuel lines had ever been replaced. While the fuel related components (i.e. carburetor, fuel pump, and associated lines) attached to the engine were thermally damaged, the degree of damage was significantly less than the fuel components attached to the firewall. The thermal damage and sooting patterns indicate that an accelerant based fire originated on both sides of the firewall near the bottom.
HISTORY OF FLIGHT On April 30, 2001, at 1850 mountain standard time, a Bellanca 14-19, N521A, caught fire and exploded while making a precautionary landing at Casa Grande Municipal Airport (CGZ), Casa Grande, Arizona. The airplane was destroyed and the certificated airline transport pilot and one of his two passengers received serious injuries. The second passenger sustained serious thermal burns and succumbed to her injuries 20 days after the accident. The airplane was being operated as a personal flight by the owner/pilot under the provisions of 14 CFR Part 91 when the accident occurred. The local flight had originated from Chandler Municipal Airport (CHD), Chandler, Arizona, about 1830. Visual meteorological conditions prevailed at the time and no flight plan had been filed. The front seat passenger reported that a fluid leak had developed from an area behind the right side of the instrument panel, and was dripping on the floor near the rudder pedals. The pilot stated that the fluid was coming from an inspection panel on the firewall and that the fluid was clear. The pilot then pulled back the power slowly and headed for Casa Grande airport and subsequently attempted a precautionary landing in order to determine the extent of the problem. The passenger described the touchdown and rollout as normal until an explosion occurred, which filled the cabin area with flames. A second witness, who was downwind in the traffic pattern, stated that the airplane had landed without incident on runway 05. It was on rollout when flames appeared from beneath the forward part of fuselage. Seconds later, as the airplane slowed near a taxiway, the cabin exploded with a bright flash. The right cabin door was blown open and the airplane ground looped. The airplane ran off the left side of the runway before reentering the runway and coming to a stop on a bearing of 110 degrees. Witnesses on the ground reported seeing flames coming out of the front-bottom portion of the airplane before hearing a "pop" in conjunction with the explosion inside the cockpit. The passenger in the back seat exited the airplane and was followed by the pilot who had been in the left front seat. When the pilot realized that the right front seat passenger had not exited, he reentered the cabin and helped her out of the airplane. The airport-based fire fighters responded within 2 minutes; however, the airplane had become completely engulfed in flames before it could be extinguished. The fire department attributed the fire to gasoline. All three occupants initially received serious thermal injuries. PERSONAL INFORMATION The pilot was a Boeing 737 captain, for a major airline. Review of the Federal Aviation Administration (FAA) airman records disclosed that the pilot held an airline transport pilot certificate with type ratings for a B-737 and a SA-227. Review of the FAA Medical Certification records revealed that the pilot held a third-class medical, which was issued on May 12, 2000. At that time he reported that he had accrued 14,805 hours. AIRCRAFT INFORMATION The airplane was a Bellanca 14-19, serial number 2074. A review of the airplane's logbooks revealed a total airframe time of 1,673.2 hours. An annual inspection was completed on May 16, 2000, at a total time of 1,661.2 hours. The airplane had a Lycoming O-435-A engine, serial number L-597-17, installed. Total time on the engine at the annual inspection was 1,663.2 hours. The hour meter read 122.2 during the last annual inspection. The current owner purchased this airplane in December 1995. The airplane had been disassembled and stored by the previous owner; however, prior to delivery to the current owner the airplane was reassembled and an annual inspection was conducted. The owner stated that during the 1997 annual inspection, squawk sheet discrepancies were also worked on. Many of the entries in the squawk book dealt with the fuel system. The owner was unable to furnish Safety Board investigators with copies of the squawk entries, and the airframe logbooks indicated that the annual was completed. AERODROME INFORMATION Casa Grande Municipal Airport has a 1,464-foot mean sea level (msl) field elevation, and one hard surfaced runway on a 050-230 magnetic orientation. Runway 23 is 5,200 feet long by 100 feet wide, and is equipped with medium intensity runway edge lights and a 2-box Visual Approach Slope Indicator system to the left of the runway. METEOROLOGICAL INFORMATION The Automated Weather Observation System at CGZ reported the weather at the time of the accident: winds 310-degrees at 4 knots; visibility 10 sm; sky clear; temperature 31 degrees Celsius; dew point -1-degrees Celsius; and altimeter setting of 29.91 inHG. WRECKAGE AND IMPACT INFORMATION The airplane is constructed of a welded tubular steel frame with a fabric covering. The wreckage was oriented on runway 5 with a 110-degree magnetic bearing. It was observed that the fire consumed majority of the fabric skin, leaving only the metal frame and patches of fabric on the left wing and tail section. Also parts of the metal frame were warped, especially on the lower right-hand side near the firewall and where the instrument panel would have been. In addition, the bottom braces of the engine mount exhibited thermal damage and were warped. The aircraft had extensive thermal damage due to the fire after landing, and it was observed that the most thermal damage appeared to be forward of the right seat where the passenger reported the fluid leak. Furthermore, it was observed that there was sooting and discoloration on the firewall in the engine compartment. There was red and black soot on the topside and on the right-hand side of the firewall, along with some discoloration. On the right side of the firewall the color was a mixture of black and tan, with a little red. On the bottom of the firewall there was minimal sooting and a tan color. The accident airplane was equipped with three metal fuel tanks. All three fuel tanks were swollen and breached and partially consumed by the fire. There was no evidence to indicate puncturing, crushing, or scraping of any tank had occurred. No fuel was recovered from the wreckage. The carburetor was sooted, but intact and still attached to the engine crankcase. TEST AND RESEARCH An examination by a Safety Board investigator revealed that two pressure gauges are located in the top right portion of the instrument panel around the point identified by the right seat passenger as the source of the fluid leak. A pressure line from the fuel and oil pumps is connected to 3-in-1-gauge, which also displays fuel quantity of the selected tank. A detailed examination of the remnants of both lines revealed that both lines were MIL-H-6000 fuel and oil hose. No diagrams of the fuel system were readily available, and investigators contacted the owner of a stock Bellanca 14-19 for a description of the fuel system. The main fuel line from the selector valve runs down the center of the fuselage under the floor and exits through a firewall pass-through fitting at the bottom center of the firewall. The line continues to the gascolator, which is located on the lower left side of the firewall. From the gascolator, a line carries the fuel supply to the engine driven fuel pump and thence to the carburetor inlet fitting. From the fuel pump, a secondary line for fuel pressure measurement goes up to one of three firewall pass through fittings located on the upper right quadrant (as viewed from the cockpit) of the firewall; these three fittings are side by side and would be nearly in front of the right seat passenger's location. The two other fittings are for oil and hydraulic pressure line connections. On the cockpit side of the firewall, lines connect these fittings to a "3-in-1" instrument panel gage that registers fuel, oil, and hydraulic pressure. The owner of the exemplar airplane also noted that there is no inspection panel on the firewall, only a dimpled/depressed area (from engine side inward into the cabin) that is used for generator clearance at the back of the engine. The fittings for the 3-in-1-fuel gauge line are above and just to the right of this dimpled area. Review of the airplane's maintenance history disclosed no documentation showing that the 3-in-1-guage lines had been replaced within the preceding 5 years. The position of the hoses is within the cabin, between the instrument panel and the firewall. Their location, near the top of the instrument panel, makes performing a visual or physical inspection without prior removal of the instrument panel a virtual impossibility. The 3-in-1-fuel gauge was overhauled in November 1998. FAA Form 8130-3, airworthiness approval tag, was completed for the 3-in-1-fuel gauge November 9, 1998. ADDITIONAL INFORMATION The wreckage was released to the insurance company adjuster representing the registered owner on August 2, 2002.
A fuel leak on the cabin and engine sides of the firewall with a probable origin at the firewall pass-through fitting for the fuel pressure gage line. The fire likely began on the engine side of the firewall near the bottom with the explosive ignition of the pooled fuel/vapors in the cockpit after burn through penetration of the fuselage fabric skin on the bottom aft side of the firewall. Further refinement of the leak source between the pass-through fitting and the lines/connectors could not be established due to thermal destruction of the components.
Source: NTSB Aviation Accident Database
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