# NTSB ANC99LA030: Interstate S-1B1, N48027, Anchorage, AK, March 4, 1999 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: March 4, 1999, 14:53 local (18:53 UTC) - Place: Anchorage, AK - Coordinates: 61.209499, -149.889358 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.2095&lon=-149.8894&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report April 25, 2001 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - NTSB case key (mKey): 45887 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC99LA030 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/45887/pdf - Page: https://openairdocs.org/ntsb/ANC99LA030 ## Probable cause Fuel starvation resulting from the pilot not understanding the fuel system procedures, and selecting the improper fuel selector position. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - nonmechanical, approach - vfr pattern - base turn - fluid,fuel - starvation (cause) - procedures/directives - not understood, pilot in command (cause) - fuel tank selector position - improper, pilot in command (cause) - Forced landing, descent - emergency ## Analysis While approaching the airport, the airplane's engine lost power. The pilot applied carburetor heat with no response. He intentionally ensured the fuel valve was selected to the 'left main' position, because he knew there was about five gallons of fuel in that tank. The right tank was empty. The fuel system in the left tank has two outlet standpipes. The 'left main' loses suction with about five gallons remaining. The 'reserve' standpipe allows these remaining five gallons to flow out of the tank when 'reserve' is selected on the fuel valve. The pilot told the NTSB investigator-in-charge (IIC) he did not understand the plumbing for the fuel system. The pilot performed a forced landing at an off airport site. The NTSB IIC confirmed that there was fuel in the left tank, and only a trace of fuel in the right tank. ## Factual narrative On March 4, 1999, at 1453 Alaska standard time, an Interstate S-1B1 Arctic Tern, tailwheel equipped airplane, N48027, was substantially damaged during a forced landing about 1/2 mile short of runway 33 at Merrill Field, Anchorage, Alaska. The solo private pilot sustained minor injuries. The airplane was being operated as a local, personal flight under 14 CFR Part 91. The flight departed Merrill Field at 1315. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The NTSB investigator-in-charge (IIC) interviewed the pilot at the scene at 1530 on March 4. The pilot indicated that as he was returning to Merrill Field, the engine began to run rough, and the engine speed dropped to about 600 rpm. He applied carburetor heat, but did not notice a change in rpm. During the emergency descent, while in a wings level attitude, engine power momentarily returned to normal, then dropped off again. The pilot said he confirmed his fuel selector was on the left tank, which held about five gallons of fuel. He stated that he realized he was not going to reach the runway, and completed a forced landing at slow speed into a snow covered area with small trees. The pilot told the NTSB IIC that during his flight, he intentionally exhausted the fuel in the right tank, and was returning to Merrill on the left tank. Initial inspection of the airplane revealed fuel in the left tank, and a trace amount in the right tank. A steady stream of clear, blue fluid flowed out of each wing tank sump drain with no evidence of water. All engine controls were connected, and moved freely. There was no indication of rotational scratching or bending visible on the propeller. Additional interviews with the pilot, and an inspection of the fuel system, revealed that the left fuel tank has two outlet standpipes which supply the fuel selector valve. The "left main" outlet standpipe is the taller of the two, and loses suction when the fuel level in the left tank drops to about five gallons. The "reserve" standpipe is shorter, and allows the remaining five gallons to be drawn from the left wing tank. The fuel selector valve handle is located between the pilot's legs, and is not easily visible to the pilot. The pilot stated that he was not familiar with the fuel system plumbing, nor that use of the "reserve" position on the fuel selector valve was required to access the remaining five gallons of fuel in the left wing tank. He said he intentionally insured the valve selector was on the left tank position, because he knew there was still five gallons of fuel in that tank. ## Aircraft - Registration: [N48027](https://openairdocs.org/aircraft/N48027), registered now, S/N 11, built 1942 (OpenAirDocs) - Reported make and model: Interstate S-1B1 - Registry model: [Interstate S-1B1](https://openairdocs.org/model/interstate-s-1b1) (registry code 1850302) (OpenAirDocs) - Registry engine: [Franklin 4ACG199H3](https://openairdocs.org/engine/franklin-4acg199h3) (registry code 27010, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 11 - Airframe hours: 1153 - Engines: Lycoming O-320-E2D 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: William A. Quirk, III - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 27, 1998, 158 hours before - Departed: MRI - Airport: MRI, Merrill Field ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 59; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: front; flight hours: 2,425 total, 205 in this make and model, 2,425 as pilot in command, 19 in the last 90 days, 12 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 25 °F, dew point 5 °F - Altimeter: 30.00 inHg - Observed at: MRI, 1 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 19990304013749A](https://openairdocs.org/incident/19990304013749A), Mar 4, 1999: Arctic S1B1, Anchorage, AK, Substantial damage. (.19) On March 4, 1999, at 1453 Alaska standard time, an interstate S-1B1 Arctic tern, tail wheel equipped airplane, N48027, was substantially damaged during a… ## Other investigations on N48027 (1) 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. - [NTSB ANC02LA026](https://openairdocs.org/ntsb/ANC02LA026), Mar 29, 2002: Interstate S-1B1 (N48027), Big Lake, AK, substantial damage. Probable cause: The separation of the exhaust system stack from the heat exchanger. A factor associated with the accident was an engine compartment fire. 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.