# NTSB DCA91MA031: Bell 412SP, N78S, Merion, PA, April 4, 1991 - Type: NTSB accident investigation - Classification: Accident · Fatal · Class 1 · Major · Final report - Date: April 4, 1991, 12:10 local (17:10 UTC) - Place: Merion, PA - Coordinates: 39.999595, -75.24089 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=39.9996&lon=-75.2409&mi=10 - Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 7 fatal, 1 serious, 4 minor; on the ground: 2 fatal, 1 serious, 4 minor - Status: Completed, report September 27, 1991 - Report: Approved by Office Director - Investigation class: Class 1 - NTSB office: Major Investigations Division - Safety recommendations: Yes - NTSB case key (mKey): 15949 - NTSB case page: https://www.ntsb.gov/investigations/Pages/DCA91MA031.aspx - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/15949/pdf - Board report AAR9101S (PDF): https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9101S.pdf - Page: https://openairdocs.org/ntsb/DCA91MA031 ## Probable cause (aircraft 2) THE POOR JUDGEMENT BY THE CAPTAIN OF THE AIRPLANE TO PERMIT THE IN-FLIGHT INSPECTION AFTER HE HAD DETERMINED TO THE BEST OF HIS ABILITY THAT THE NOSE LANDING GEAR WAS FULLY EXTENDED, THE POOR JUDGMENT OF THE CAPTAIN OF THE HELICOPTER TO CONDUCT THE INSPECTION, AND THE FAILURE OF THE FLIGHTCREW OF THE HELICOPTER TO MAINTAIN SAFE SEPARATION. CONTRIBUTINGTO THE ACCIDENT WAS THE INCOMPLETE TRAINING AND CHECKING THAT THE FLIGHTCREW OF N3645D RECEIVED FROM LYCOMING AIR SERVICE AND THE FAA PRINCIPAL OPERATIONS INSPECTOR ASSIGNED TO THE OPERATOR. ## Probable cause (aircraft 1) THE POOR JUDGEMENT BY THE CAPTAIN OF THE AIRPLANE TO PERMIT THE IN-FLIGHT INSPECTION AFTER HE HAD DETERMINED TO THE BEST OF HIS ABILITY THAT THE NOSE LANDING GEAR WAS FULLY EXTENDED, THE POOR JUDGMENT OF THE CAPTAIN OF THE HELICOPTER TO CONDUCT THE INSPECTION, AND THE FAILURE OF THE FLIGHTCREW OF THE HELICOPTER TO MAINTAIN SAFE SEPARATION. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Midair collision, approach - judgment - poor, pilot of other aircraft (cause) - judgment - poor, pilot in command (cause) - clearance - not maintained, pilot in command (cause) - In flight collision with terrain/water, descent - uncontrolled - Midair collision, maneuvering - landing gear,gear indicating system - inoperative - emergency procedure - performed, pilot in command - judgment - poor, pilot in command (cause) - inadequate transition/upgrade training, company/operator management (contributing factor) - inadequate surveillance,insufficient staff, faa(organization) (contributing factor) - judgment - poor, pilot of other aircraft (cause) - clearance - not maintained, pilot of other aircraft (cause) - In flight collision with terrain/water, descent - uncontrolled ## Analysis (aircraft 2) PIPER AEROSTAR 601, N3645D, WAS ARRG AS BELL 412 (HELICOPTER), N78S, WAS DEPG. N3645D RPRTD THE ACFT'S NOSE GEAR INDCR LGT DID NOT ILLUMINATE TO VERIFY THE NOSE GEAR WAS DWN & LOCKED. CREW OF N78S HEARD THE COM & SAW N3645D AS THEY CROSSEDBENEATH N3645D'S APCH PATH. THEY RPRTD N3546D'S NOSE GEAR APPEARED TO BE EXTDD. N3645D FLEW PAST THE TWR & TWR PSNL ALSORPRTD THE NOSE GEAR APPEARED TO BE EXTDD. AS N3645D WAS CLRD TO TURN DWNWND, N78S OFFERED TO JOIN FOR A CLOSER LOOK. CAPT OF N3645D ACCEPTED THE OFFER. DRG JOINUP, N78S CONVERGED FM LEFT REAR, THEN RPRTD THEY WOULD PASS ARND THE RGT SIDE& LOOK AT EVERYTHING AS THEY WENT BY. THEY RPRTD THAT EVERYTHING LOOKED OK. MOMENTS LTR, THE 2 ACFT COLLIDED & CRASHED TO THE GND. NO MECH RSN WAS FND THAT WOULD HAVE RESULTED IN THE ACDNT. NONE OF THE PLTS HAD TRNG FOR FLT IN CLOSE PROX- IMITY TO ANOTHER ACFT. THERE WERE INDCNS THE CAPT OF N3645D LACKED TRNG IN ACFT SYSTEMS & THAT HIS EMPLOYER (THE OPER) LACKED SURVEILLANCE BY THE FAA. THE EMERG PROC SXN OF THE AEROSTAR FLT MANUAL LACKED INFO ON EMERG GEAR EXTN. ## Analysis (aircraft 1) PIPER AEROSTAR 601, N3645D, WAS ARRG AS BELL 412 (HELICOPTER), N78S, WAS DEPG. N3645D RPRTD THE ACFT'S NOSE GEAR INDCR LGT DID NOT ILLUMINATE TO VERIFY THE NOSE GEAR WAS DWN & LOCKED. CREW OF N78S HEARD THE COM & SAW N3645D AS THEY CROSSEDBENEATH N3645D'S APCH PATH. THEY RPRTD N3645D'S NOSE GEAR APPEARED TO BE EXTDD. N3645D FLEW PAST THE TWR & TWR PSNL ALSORPRTD THE NOSE GEAR APPEARED TO BE EXTDD. AS N3645D WAS CLRD TO TURN DWNWND, N78S OFFERED TO JOIN FOR A CLOSER LOOK. CAPT OF N3645D ACCEPTED THE OFFER. DRG JOINUP, N78S CONVERGED FM LEFT REAR, THEN RPRTD THEY WOULD PASS ARND THE RGT SIDE& LOOK AT EVERYTHING AS THEY WENT BY. THEY RPRTD THAT EVERYTHING LOOKED OK. MOMENTS LTR, THE 2 ACFT COLLIDED & CRASHED TO THE GND. NO MECH RSN WAS FND THAT WOULD HAVE RESULTED IN THE ACDNT. NONE OF THE PLTS HAD TRNG FOR FLT IN CLOSE PROX- IMITY TO ANOTHER ACFT. THERE WERE INDCNS THE CAPT OF N3645D LACKED TRNG IN ACFT SYSTEMS & THAT HIS EMPLOYER (THE OPER) LACKED SURVEILLANCE BY THE FAA. THE EMERG PROC SXN OF THE AEROSTAR FLT MANUAL LACKED INFO ON EMERG GEAR EXTN. ## Aircraft 1 - Registration: [N78S](https://openairdocs.org/deregistered/N78S-1991-09-23), registration cancelled 1991-09-23, S/N 33114 (OpenAirDocs) - Reported make and model: BELL 412SP - Registry model: [Bell 412](https://openairdocs.org/model/bell-412) (registry code 1182202) (OpenAirDocs) - Category: Helicopter - Serial number: 33114 - Airframe hours: 1841 - Engines: P&W PT6T-3B 1350 horsepower turbo shaft - Damage: Destroyed - Fire: On-Ground - Flight: Executive/Corporate, Part 91 - Operator: Sun Company Inc. - Registered owner: Sun Company Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 12, 1991, 6 hours before - Departed: PHL, PHILADELPHIA, PA - Destination: RADNOR, PA - Flight plan: VFR ## Aircraft 2 - Registration: [N3645D](https://openairdocs.org/deregistered/N3645D-1991-11-20), registration cancelled 1991-11-20, S/N 6108448162153 (OpenAirDocs) - Reported make and model: PIPER AEROSTAR 601 (AEROSTAR 6) - Registry model: [Piper AEROSTAR 601](https://openairdocs.org/model/piper-aerostar-601) (registry code 7106010) (OpenAirDocs) - Category: Airplane - Serial number: 61-0844 - Airframe hours: 2739 - Engines: LYCOMING IO-540-S1A5 300 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Part 135 - Operator: Lycoming Air Service, doing business as Lycoming Air Service - Registered owner: W. W. Aviation, Inc - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 25, 1991, 25 hours before - Departed: IPT, WILLIAMSPORT, PA - Destination: PHL, PHILADELPHIA, PA - Flight plan: IFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot, aircraft N78S; age 42; commercial, flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; toxicology performed; flight hours: 8,000 total, 17 in the last 90 days, 6 in the last 30 days, 2 in the last 24 hours - Pilot, aircraft N3645D; age 30; flight instructor, airline transport, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 1,876 total ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 63 °F, dew point 41 °F - Altimeter: 30.00 inHg - Observed at: PHL, 8 nm away ## FAA reports on this event (2) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19910404008911A](https://openairdocs.org/incident/19910404008911A), Apr 4, 1991: Bell 412, Philadelphia, PA, Destroyed, 4 fatal. Struck bottom of N3645D while trying to confirm its gear position,both crashed. Pilots misjudged their positions. - [Accident 19910404008912A](https://openairdocs.org/incident/19910404008912A), Apr 4, 1991: Piper PA60601, Philadelphia, PA, Destroyed, 5 fatal. Was struck from below by N78S that was trying to check nose gear down. Both crashed. Judgement and skill factors. 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.