United Airlines Flight 608 Accident Report

.,SA-I 53 File No. 1-0097-47 ) CIVIL AERONAUTICS BOARD I ACCIDENT I W ESTIGATOO I I Adopted: February 2, 1948 . Released: February 3, 19y8 UNITED AIR LlhES, INC., BRYCE CANYON, UTAH, OCTOXR 24, 1947 The Accident - United Air Lines I Flight 608 crashed observed what appeared 'to be white smoke at 1229 MST,2 October 24, 1947, 1 1/2 streaming from the aircraft, followed miles southeast of Bryce Canyon Airport, later by dense black smoke. The first Utah, during an attempted emergency witnesses who observed fire in the bottom landing resulting from a fire in flight. of the aircr8ft at approximately the The aircraft, a Model DC-6, NC 37510, center-section were located approxi- was demolished by impact and fire, and mately 15 miles south of Bryce Canyon. all of the 46 passengers and the crew of Until shortly before the moment of im- 6 were killed. pact,. the aircraft appeared to be under normal control; hawever, no_,witnesses History of the FI ight were located who observed the, crash. Flight 608 departed Los Angeles, Cal- ifornia, at 1023 with its destination I nvest i gat ion Chicago, Illinois, to cruise at 19,000 Immediately after the accident the feet according to visual flight rules. wreckage was protected by Civil Aeronau- Routine position reports were made over tics Administration personnel until a Fontana, Daggett and Silver Lake, Cali- guard was established by the National' fornia; Las Vegas, Nevada; and Sdint Park Service, pending the arrival of George, Utah. During the latter report, Board investigators. During the evening the flight indicated that it estimated of the same day various investigation passing over Bryce Canyon, Utah, at 1222. groups were organized and an inspection At 1221 Flight 608 reported that a of the wreckage and a search of the flight fire had been detected in the bagggge path were begun. Parts of the wrecked compartment which the crew was unable to aircraft were transported to the Douglas extinguish. The report added that the Aircraft Company plant at Santa Monica, cabin was filled with smoke and that the California, as rapidly as possible in flight was attempting to make an emer- order that identification and evaluation gency landing at Bryce Canyon Airport. as well as reconstruction of the perti- Shortly thereafter the flight again re- nent structure, might be facilitated. ported that the nt&ilis going out-we The latter reconstruction included the may get down and we may not." At 1226 major portion of the fuselage from the an6ther transmission was received from leading edge of the wings to the rear the flight indicating that it was going pressure bulkhead. A separate mock-up Into the "best placen available. One of the air-conditioning compartment was minute later the flight reported wwe may also made as a means of tracing the flame make it-approaching a strip." No fur- path and assessing the damage resulting ther contact was had from the flight. from fire in flight. Witnesses who observed the aircraft The aircraft struck the ground at a as it was approaching Bryce Canyon from point approximately 1 1/2 miles southeast approximately 20 miles southwest first of the Bryce Canyon Airport while headed in a westerly direction. The flight path 'The Board is making further analysis of the con- was projected from the point of impact slderable amount of technlcal data complled in the southeastward in a long gentle right course or its lnrdstlgatlon of thls accident and sfm- llar accldent at Gallup, New Mexico and a report wlll curve which eventually swung southwest- be made at a later date containing a complete analy- ward toward Tropic, Utah. Various arti- sts of all pertlnent data and further discussion or the several factors contrlbutlng to the cause of this cles carried aboard the aircraft and acc dent. kAll tlmes referred to herein are Mountaln Stand- component parts of the aircraft structure ard and baaed on the eehour clock. were located along the flight path for a -18416 (1)' ... ' 2 Accident Invest i gat i on Report maximum distance of 26 miles from the Examination crf the powerplants, hy- point of impact. The sequence of struc- draulic system, electrical system and tural failure resulting from the fire cabin supercharging system indicated that aboard the aircraft was readily recon- none of these sFstems contributed to the structed from these objects. It was ap- fire in this imstance. Inspection of the parent that the aircraft structure began primary wing an$ empennage structure and to disintegrate in the center section in the control surfaces gave no evidence of the vicinity of the right wing fillet failure in flight. and that parts of the interior of the At the time af departure from Los aircraft in the proximity of this area Angeles all four main and the four al- began to fall from the aircraft early' in ternate tanks were filled to capacity; the development of the fire. The exten- both auxiliary tanks were emyty. Be- siveness of this disintegration is in- cause of illness, the captain's regular dicated by the fact that the trailing co-pilot did not accompany him on this edge of the right wing flap, the main flight. The testimony of the captain's cabin entrance door and the buffet cold regular co-pilot indlcates the procedure box had fallen from the aircraft prior which the captafn normally followed with to impact. The extent of burning on respect to fuel management: The take- parts of the cabin interior, prior toim- off and climb would be accomplished with pact, indicates conclusively that the each engine drawing fuel from its re- fire in flight was of such severity as spective main tmk. Immediately after to have been unsurvivable for cabin reaching cruising altitude the captain occupants. would switch each engine to its alter- Reconstruction of the fuselage and nate tank. In this manner the flight analysis of the burning of its struc- would proceed until a minimurb of 500 tural components indicate that the burn- pounds of fuel remained in the lowest ing in flight took place in an area cov- alternate tank. At this poifit, the cap- ~ ering the lower right side of the fuse- tain would transfer fuel from the higher lage beginning at a point in the center of the alternate tanks to the lower in section approximately midwing and ex- order to equalize the contents of all tending rearward approximately 23 feet alternate tanks. This procedure requires and upward along the right side of the placing the left cross-feed in the Ron fuselage to the top of the window line. engines 1 and 2" position and the right Inspection of the structure and compo- cross-feed in the "on engines 3 and 4" nents of the cockpit and the rear lounge position; the booster pump switches for and toilets show no evidence of burning the respective out-board alternate tanks in flight. in the *highn position. After having Control cables passing through the equalized-the contents of the alternate air-conditioning compartment, commonly tanks, the captain would stop the trans- referred to as the nboiler room," were fer process by turning the booster pump found to have been partially consumed by switches and the cross-feed controls to fire and it was evident that all of these the noff" position. cables had failed in tension in the The Model DC-6 as delivered by the burned area. At least one of the emer- manufacturer was equipped with. a fuse- gency landing flares which are located lage fire extingulshing and detecting at- the trailing edge of the right wing system which included protection for both fillet immediately forward of the alcohol forward and aft baggage compartments and tank was found to have been ignited in the hydraulic accessories compartment. flight. Chemical analysis of smudge However, with the exception of a 1.4 marks on aircraft parts and components pound bottle of carbon dioxide which indicates clearly that the damage result- lischarged 'directly into the cabin heater ing from the burning of the barium ni- 2ombustlon cnamber, no fire-extinguish- . trate in the flares covered an extensive ing protection was provided the air-con- area aft and above the flare location. iitioning accessories compartment. The alcohol tank which had also fallen Inspection of the DC-6 fuel system from the aircraft prior to impact showed lisclosed that the No. 3 alternate tank p signs of severe external burning and in- vent outlet w'as located on the right side dicated the probability of having been of the fuselage near the leading edge of ruptured before it left the aircraft. the wing and close to the bottom wing -18416 .. Accident lnvesti gation Report 3 fillet. Approximately 10 feet aft of during flright. NO Instructions had been this point and slightly to the left there given the sir carrier's pilots concerning was an air scoop which served as a source possible hazards associated with over- -of cabin heater combustion air and coql- flow of gasoline from the No. 3 alter- ing air for the cabin supercharger air nate tank. No instructions were pro- after-cooler and cabin supercharger oil vided in the manufacturer's DC-6 Opera- cooler. Flight tests conducted with tioq Manual, or the CUApproved DC-6 other model DC-6 aircraft subsequent to Aircraft Operating Manual advising this accident revealed that overflow from against fuel transfer, nor were any in- the No. 3 alternate tank through the air structions contained in the air carrier's vent line and out the vent outlet would DC-6 Pilot's Operating Manual outlining sweep back in the slip stream toward the any procedures for fuel transfer.

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