- Date
- April 4, 1991, 12:10 local (17:10 UTC)
- Place
- Merion, PA
- Injuries
- 7 fatal, 1 serious, 4 minor; on the ground: 2 fatal, 1 serious, 4 minor
- Phase of flight
- Approach
- Weather
- Visual (VMC) · Day
- Status
- Completed · report September 27, 1991
- Report
- Approved by Office Director
- Investigation class
- Class 1
- NTSB office
- Major Investigations Division
- Safety recommendations
- Yes
- FAA reports
- 19910404008911A19910404008912A
- Case key
- 15949
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Probable cause
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.
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
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
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.
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 · 2
- Registration
- N78S
- Reported as
- Bell 412SP
- Category
- Helicopter
- Serial number
- 33114
- Airframe hours
- 1,841
- Engine
- P&W PT6T-3B, 1,350 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
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
- Registration
- N3645D
- Reported as
- Piper Aerostar 601 (AEROSTAR 6)
- Category
- Airplane
- Serial number
- 61-0844
- Airframe hours
- 2,739
- Engine
- 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
Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.
Flight crew · 2
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot, aircraft N78S
- Age
- 42
- Certificates
- 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
- Role
- Pilot, aircraft N3645D
- Age
- 30
- Certificates
- 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.