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NTSB Report
December 12, 1984 · Piper PA-31 · N9011Y
Pontiac, MI
Overview
Report Status
Preliminary report
Event Type
Accident
Date
December 12, 1984
Injury Outcomes
2 injuries (2 fatalities)
Location
Pontiac, MI
Aircraft
Piper PA-31
Tail Number
N9011Y
Injuries
Fatal
Aircraft Damage
Destroyed
NTSB Number
CHI85FA070
THE AIRCRAFT DEPARTED THE AIRPORT WITH ONE DRY AIR PUMP INOPERATIVE AND THE OTHER PUMP READING LOW. AIRCRAFT CONTROL WAS LOST DURING AN INSTRUMENT APPROACH IN IMC APPROXIMATELY 2.5 HOURS LATER. BOTH PUMP DRIVESHAFTS WERE FOUND SHEARED IN THE WRECKAGE AND BOTH BROKEN SHAFT SURFACES SHOWED POLISHED SURFACES. DURING FURTHER TESTING IT WAS DISCOVERED THAT TAPE OR PIPE DOPE HAD BEEN USED IN THE THREADING OF THE INTAKE & OUTFLOW FITTINGS OF THE LEFT PUMP. NO CONTAMINANTS WERE FOUND IN THE RT PUMP BUT THE PUMP WALL INNER SURFACES GAP WAS APPRX .005 IN. THIS GAP IS APPROX 50 PERCENT OVER THE ALLOWABLE TOLERANCE FOR A SERVICEABLE AIR PUMP.THE PRESSURE REGULATOR VALVE TO THE ATTITUDE INDICATOR GYRO & THE COMPASS GYRO WERE EXAMINED & FOUND TO REQUIRE PRESSURE EXCEEDING NORMAL REQUIREMENT STANDARDS.
Full Narrative
THE AIRCRAFT DEPARTED THE AIRPORT WITH ONE DRY AIR PUMP INOPERATIVE AND THE OTHER PUMP READING LOW. AIRCRAFT CONTROL WAS LOST DURING AN INSTRUMENT APPROACH IN IMC APPROXIMATELY 2.5 HOURS LATER. BOTH PUMP DRIVESHAFTS WERE FOUND SHEARED IN THE WRECKAGE AND BOTH BROKEN SHAFT SURFACES SHOWED POLISHED SURFACES. DURING FURTHER TESTING IT WAS DISCOVERED THAT TAPE OR PIPE DOPE HAD BEEN USED IN THE THREADING OF THE INTAKE & OUTFLOW FITTINGS OF THE LEFT PUMP. NO CONTAMINANTS WERE FOUND IN THE RT PUMP BUT THE PUMP WALL INNER SURFACES GAP WAS APPRX .005 IN. THIS GAP IS APPROX 50 PERCENT OVER THE ALLOWABLE TOLERANCE FOR A SERVICEABLE AIR PUMP.THE PRESSURE REGULATOR VALVE TO THE ATTITUDE INDICATOR GYRO & THE COMPASS GYRO WERE EXAMINED & FOUND TO REQUIRE PRESSURE EXCEEDING NORMAL REQUIREMENT STANDARDS.
Flight
Event TypeAccident
Event Time19:32 EST
Nearest AirportOakland Pontiac (3nm W)
Runway0
Runway Length6200 ft
Runway Width150 ft
Flight Plan FiledIFR
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftPiper PA-31
Tail NumberN9011Y
Aircraft CategoryAir
DamageDestroyed
Operating RulePart 135
Engines2
Engine TypeReciprocating
Engine DetailsLycoming · TI0-540-A1A · Reciprocating · 310
Seats6
People & Injuries
Injury Summary2 injuries (2 fatalities)
Fatal2
Serious0
Minor0
Uninjured0
Total2
Crew 1Age 31 · First Class
Conditions
ConditionsIMC
LightDark Night
Wind180° @ 12 kt
Visibility75 sm
Ceiling100 ft
Temperature / Dew Point0 C / 0 C
Altimeter29.00 inHg
Observation Time00:32
Weather SourceWFAC