# NTSB FTW94FA141: Mooney M20E, N1905Y, Broomfield, CO, May 1, 1994 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: May 1, 1994, 12:20 local (18:20 UTC) - Place: Broomfield, CO - Coordinates: 39.890476, -105.109741 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.8905&lon=-105.1097&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 2 fatal - Status: Completed, report July 31, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 18894 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW94FA141 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18894/pdf - Page: https://openairdocs.org/ntsb/FTW94FA141 ## Probable cause FATIGUE FAILURE OF THE ENGINE CRANKSHAFT; AND FAILURE OF THE PILOT TO MAINTAIN ADEQUATE AIRSPEED, WHILE MANEUVERING TO LAND, WHICH RESULTED IN A STALL AND COLLISION WITH THE TERRAIN. FACTORS RELATED TO THE ACCIDENT WERE: THE UNDESIRABLE ENGINE/PROPELLER VIBRATION, AND THE LOOSE CRANKCASE AND CYLINDER BASE NUTS. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, takeoff - initial climb - maintenance,modification - performed - miscellaneous,engine - vibration (contributing factor) - propeller system/accessories - vibration (contributing factor) - miscellaneous,bolt/nut/fastener/clamp/spring - loose (contributing factor) - engine assembly,crankshaft - fatigue (cause) - Forced landing, maneuvering - turn to landing area (emergency) - Loss of control - in flight, maneuvering - turn to landing area (emergency) - airspeed - inadequate, pilot in command (cause) - stall/spin - inadvertent, pilot in command (cause) - In flight collision with terrain/water, maneuvering - turn to landing area (emergency) ## Analysis SHORTLY AFTER TAKEOFF, THE PILOT REQUESTED CLEARANCE TO RETURN FOR AN IMMEDIATE LANDING. A WITNESS SAID THAT HE HEARD A METALLIC NOISE FROM THE PLANE AS IT PASSED OVERHEAD. HE SAID THE PILOT MADE A STEEP RIGHT BANK TO LAND ON RUNWAY 29L; HOWEVER, THE PLANE IMPACTED BETWEEN THE PARALLEL RUNWAYS. AN EXAM OF THE ENGINE REVEALED 2 FINGER-TIGHT CYLINDER BASE NUTS & UNDERTORQUED BASE NUTS & CRANKCASE THROUGH-NUTS. A TEARDOWN REVEALED THE CRANKSHAFT HAD FAILED FROM FATIGUE BETWEEN THE #3 & #4 CONNECTING ROD JOURNALS. A METALLURGICAL EXAM OF THE CRANKSHAFT REVEALED HIGH LOCALIZED STRESS-INDUCED FATIGUE CRACKS. THE ENGINE HAD ACCUMULATED 266 HRS OF FLIGHT TIME SINCE MAJOR OVERHAUL ON 1/11/91. THE PLANE HAD BEEN MODIFIED WITH 2 STC'S, 1 FOR INSTALLATION OF A RAYJAY TURBOCHARGER, ANOTHER FOR INSTALLATION OF A 'BLACKMAC' PROPELLER. THE HOLDER OF THE PROPELLER STC REPORTED THE COMPANY WOULD NOT HAVE INSTALLED THE PROPELLER ON A TURBOCHARGED ENGINE, SINCE CERTIFICATION VIBRATORY TESTS WERE ONLY MADE ON NORMALLY ASPIRATED ENGINES. AFTER INSTALLATION ON 1/17/91, THE PROPELLER WAS REMOVED ON 3/19/91 FOR STATIC BALANCE & 'RE-INDEX PROP #1 BLADE 180 DEGREES;' ON 3/28/91, IT WAS REMOVED FOR A BLADE ANGLE CHECK; AND ON 5/23/91, IT RECEIVED A DYNAMIC BALANCE. ## Factual narrative HISTORY OF FLIGHT On May 1, 1994, at 1220 mountain daylight time, N1905Y, a Mooney M20E, was destroyed during a forced landing in Broomfield, Colorado. The private pilot and passenger were fatally injured. Visual meteorological conditions prevailed. Shortly after taking off from runway 11L at the Jefferson County Airport, the pilot requested clearance to make an immediate landing; he did not indicate the nature of his emergency. A witness said he heard a loud metallic noise coming from the engine as the airplane passed overhead. He said the pilot made a steep right bank in an attempt to land on runway 29L and impacted terrain. WRECKAGE AND IMPACT INFORMATION A ground scar was located abeam the 2,000 foot distance-to-go marker of runway 11L, between runways 11L and 11R. Just beyond this scar was a 60 foot gouge in the earth, aligned on a magnetic heading 250 degrees. At the end of this gouge was a 40 foot wide and 10 foot deep ravine. The airplane was found on the bank of the ravine on a magnetic heading of 080 degrees. The propeller assembly remained attached to the engine but one blade was broken off. All three blades exhibited chordwise scratches on the cambered surfaces and were S-curled midspan. The empennage was severed just aft of the baggage compartment. The left wing remained attached to the fuselage but had a circumferential crack at the inboard aileron hinge point. The flap was broken off. The right wing lay next to the fuselage but was twisted 180 degrees. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was conducted by the Jefferson County Coroner's Office, Golden, Colorado. In addition, FAA's Civil Aeromedical Institute (CAMI) conducted a toxicology screen. Trace amounts of pseudoephedrine was detected in blood and urine, and guaiphenesin was detected in urine. Acetaminophen was detected in blood (6.900 ug/ml, ug/g) and urine (152.600 ug/ml. ug/g). According to a CAMI toxicologist, acetaminophen is found to Tylenol; pseudoephedrine is a decongestant, and guaiphenesin is an expectorant. On his most recent medical examination dated October 13, 1993, the pilot indicated he was taking medications that included acetaminophen and pseudoephedrine. The toxicologist was unable to say definitively whether any of these medications, either taken singularly or together, may have been contributory to the accident. TESTS AND RESEARCH Engine disassembly revealed the crankshaft had failed at the crankcheek between numbers 3 and 4 connecting rod journals. The number 4 cylinder lower right base nut and the number 3 cylinder upper left base nut were finger tight. The upper right base nuts on numbers 2 and 4 cylinders broke free approximately 400 inch-pounds. The number 1 cylinder lower right and left base nuts and the number 3 cylinder lower right base nut loosened at less than 500 inch-pounds. All other base nuts loosened at less than 350 inch-pounds. Metal shavings were found inside the left magneto mounting on the accessory case, on the oil suction screen, and in the oil sump. There were two breaks on the bottom of the crankcase below the numbers 3 and 4 cylinders. The engine received a major overhaul on January 11, 1991. Total engine time was 4,412 hours: 266 hours since major overhaul and 11 hours since a 100-hour inspection. The crankshaft was sent to NTSB's metallurgical laboratory for analysis. According to its report, the crankshaft failed as the result of "fatigue cracking that originated from the radius on the aft end on the number 3 connecting rod journal and propagated through most of the crankcheek before final separation." There was "no evidence of metallurgical or manufacturing defects" in the crankshaft. The airplane had been modified by two Supplemental Type Certificates (STCs). The engine was equipped with a Rayjay turbocharger (SE32WE) and a McCauley "BlackMac" 3-blade propeller (SA704NE). According to a spokesman for U.S. Propeller Service in East Haddon, Connecticut, holder of STC SA704NE, the company will not install the "BlackMac" propeller on an airplane with a turbocharged engine because certification vibratory tests were made on normally aspirated engines only. No data exists for turbocharged engines. Maintenance records indicate that after its installation on January 17, 1991, the propeller was removed on March 28, 1991, "for blade angle check," and on March 19, 1991, for "static balance" and "re-index prop #1 blade 180 degrees." On May 23, 1991, the propeller received a "dynamic balance --- before .55 IPS, after .1 IPS." ADDITIONAL INFORMATION The wreckage was released to the owner's representative on May 3, 1994. The crankshaft was released on August 15, 1994. ## Aircraft - Registration: [N1905Y](https://openairdocs.org/deregistered/N1905Y-2012-08-20), registration cancelled 2012-08-20, S/N 288, built 1964 (OpenAirDocs) - Reported make and model: MOONEY M20E - Registry model: [Mooney M20E](https://openairdocs.org/model/mooney-m20e) (registry code 5870212) (OpenAirDocs) - Registry engine: [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series) (registry code 41515, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 288 - Airframe hours: 4412 - Engines: LYCOMING IO-360-A1A 200 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Verbosh, George M. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, March 25, 1994, 11 hours before - Departed: BJC - Destination: BJC - Airport: BJC, Jefferson County, runway 29L, 7,000 × 75 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 42; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 560 total, 347 in this make and model, 502 as pilot in command, 10 in the last 90 days, 9 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 7 knots - Visibility: 60 statute miles - Lowest ceiling: 20,000 ft broken - Temperature: 57 °F, dew point 30 °F - Altimeter: 29.00 inHg - Observed at: BJC ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19940501009599A](https://openairdocs.org/incident/19940501009599A), May 1, 1994: Mooney STCM20, Denver, CO, Destroyed, 2 fatal. Asked return after takeoff. Made steep right bank for 29L but impacted between runways. Crankshaft broke. Due mods. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.