# NTSB WPR11LA290: Christen Industries Pitts S-1T, N77MN, Alkali Lake, OR, June 26, 2011 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: June 26, 2011, 10:15 local (17:15 UTC) - Place: Alkali Lake, OR - Coordinates: 43.166389, -119.484169 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=43.1664&lon=-119.4842&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report November 3, 2011 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 80902 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11LA290 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/80902/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=80902 - Page: https://openairdocs.org/ntsb/WPR11LA290 ## Probable cause The loss of engine oil during cruise flight due to the failure of the front bearing oil seal. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip eng front section](https://openairdocs.org/ntsb-findings/01058510): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Christen Industries PITTS S-1T, 1 case](https://openairdocs.org/ntsb-findings/01058510/cases.md?model=2210002), [All aircraft, 13 cases](https://openairdocs.org/ntsb-findings/01058510/cases.md) - [Terrain: sloped/uneven terrain](https://openairdocs.org/ntsb-findings/03021017): Environmental issues › Physical environment · Effect on operation (probable cause); cases with it: [Christen Industries PITTS S-1T, 1 case](https://openairdocs.org/ntsb-findings/03021017/cases.md?model=2210002), [All aircraft, 270 cases](https://openairdocs.org/ntsb-findings/03021017/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Christen Industries PITTS S-1T, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=2210002), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Landing: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Christen Industries PITTS S-1T, 1 case](https://openairdocs.org/ntsb-events/440/sequence.md?model=2210002), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Christen Industries PITTS S-1T, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=2210002), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that, during cruise flight, a large amount of oil suddenly covered the windscreen, causing her to initiate a precautionary off-airport landing as the oil pressure dropped to zero. Because of the uneven terrain in area in which she was flying, suitable landing sites were minimal. During the landing, the pilot attempted to pitch the tail-wheel airplane upward in order to drag the tail along the ground to slow the airspeed. The pilot stated that she had no response from the elevator or ailerons. The airplane impacted the uneven terrain in a nose-low attitude and cartwheeled, resulting in structural damage to all four wings and the fuselage. Examination of the recovered engine revealed that the front bearing oil seal was partially extruded from the crankcase nose seal bore. No additional mechanical anomalies were noted during the examination of the engine or airframe. The reason for the front bearing oil seal becoming extruded from the crankcase bore area was undetermined. ## Factual narrative On June 26, 2011, about 1015 Pacific daylight time, a Christian Industries Inc. Pitts S-1T, N77MN, sustained substantial damage during a forced landing following a partial loss of engine power about 26 miles northeast of Alkali Lake, Oregon. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, the sole occupant of the airplane, sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight. The cross-country flight originated from Burns, Oregon, about 0950 with an intended destination of Lakeview, Oregon. The pilot reported that during cruise flight at 6,500 feet mean sea level (msl), a large amount of oil suddenly coated the windscreen. The pilot turned away from the edge of a plateau and noticed that the engine oil pressure gauge indicated "0." The pilot stated that during the off airport landing, she attempted to pull the nose up and drag the tail on the ground to slow the airplane, but had no response from the elevator or ailerons. Subsequently, the airplane impacted the ground in a nose-low attitude and cart wheeled before it came to rest upright. Examination of the airplane by the pilot revealed that the upper and lower right wings were folded upwards and the fuselage exhibited structural damage. The wreckage was recovered to a secure location for further examination. Examination of the recovered Lycoming AEIO-360-A1E engine, serial number L-24247-51A, revealed that a heavy amount of visible oil and oil covered dirt was observed surrounding the forward portion of the engine and engine cowling. All engine accessories remained attached to the engine crankcase and accessory case. All cylinders remained secure to the engine crankcase. The propeller remained attached to the crankshaft propeller flange. All oil line fittings were found tight and secure. The propeller and top spark plugs were removed. The crankcase front bearing oil seal was partially extruded from the crankcase nose seal bore. The crankshaft was rotated by hand at the crankshaft propeller flange. Rotational continuity was established throughout the engine and valve train. Thumb compression and suction was obtained on all four cylinders. The front bearing oil seal was removed from the crankshaft and examined. The spring was found intact and undamaged. A slight amount of sealant type material was found around the circumference of the forward portion of the seal. The hose extending from the crankcase breather fitting was removed. Compressed air was applied to the end of the removed hose and air was felt expelling from the crankcase breather fitting and the crankcase nose seal bore area. The reason for the front bearing oil seal to become extruded from the crankcase bore area was undetermined. Review of the airplanes maintenance logbooks revealed that the front bearing oil seal was replaced on September 14, 2010, at a tachometertime of 1,845.4 hours and replaced again on June 8, 2011, at a tachometer time of 1,910.2 hours. At the time of the accident, the airplane had accumulated 10.1 hours since the front bearing oil seal was replaced. THIS CASE WAS MODIFIED OCTOBER 6, 2011. ## Aircraft - Registration: [N77MN](https://openairdocs.org/deregistered/N77MN-2014-09-16), registration cancelled 2014-09-16, S/N 1040, built 1986 (OpenAirDocs) - Reported make and model: CHRISTEN INDUSTRIES INC PITTS S-1T - Registry model: [Christen Industries PITTS S-1T](https://openairdocs.org/model/christen-industries-pitts-s-1t) (registry code 2210002) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane - Serial number: 1040 - Airframe hours: 1919 - Engines: Lycoming AEIO-360-A1E 200 hp reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Condition, January 11, 2011, 70 hours before - Departed: Burns, OR - Destination: Lakeview, OR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: minor; commercial; airplane ratings: single-engine sea, single-engine land; medical: class 2, with waivers/limitations; last flight review November 18, 2009; seat: center; flight hours: 2,316 total, 1,650 in this make and model, 2,270 as pilot in command, 40 in the last 90 days, 10 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 150° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 63 °F, dew point 37 °F - Altimeter: 30.04 inHg - Observed at: KBNO, 34 nm away ## 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 20110626013549A](https://openairdocs.org/incident/20110626013549A), Jun 26, 2011: Christen Industries Inc PITTS S-1T, Alkali Lake, OR, Destroyed. During cruise flight at approx 6500 MSL the pilot experienced a substantial amount of oil on the windscreen. Within about 5 seconds the pilot scanned the… ## Docket (6 files) The files NTSB released with the investigation on September 29, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=80902. 4.8 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 298 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354118&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Summary of Engine Examination (item 2, .PDF, 61 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354119&FileExtension=.PDF&FileName=Summary%20of%20Engine%20Examination-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 3, .PDF, 31 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354200&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Photo 1: View of the recovered wreckage. (item 4, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354120&FileExtension=.PDF&FileName=Photo%201%3A%20View%20of%20the%20recovered%20wreckage.-Master.PDF - Photo 2: View of the top portion of the engine. (item 5, .PDF, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354121&FileExtension=.PDF&FileName=Photo%202%3A%20View%20of%20the%20top%20portion%20of%20the%20engine.-Master.PDF - Photo 3: View of the forward bearing oil seal. (item 6, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40354122&FileExtension=.PDF&FileName=Photo%203%3A%20View%20of%20the%20forward%20bearing%20oil%20seal.-Master.PDF 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.