ASN Aircraft accident Swearingen SA-226AT Merlin IV N54GP Manchester-Boston Regional Airport, NH (MHT)
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Status:Accident investigation report completed and information captured
Date:Friday 10 December 2021
Type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different
Swearingen SA-226AT Merlin IV
Operator:Castle Aviation
Registration: N54GP
MSN: AT-034
First flight: 1975
Total airframe hrs:10633
Engines: 2 Garrett TPE331-10UA-511G
Crew:Fatalities: 1 / Occupants: 1
Passengers:Fatalities: 0 / Occupants: 0
Total:Fatalities: 1 / Occupants: 1
Aircraft damage: Destroyed
Aircraft fate: Written off (damaged beyond repair)
Location:0,6 km (0.4 mls) SW of Manchester-Boston Regional Airport, NH (MHT) (   United States of America)
Phase: Approach (APR)
Departure airport:Caldwell Wright Airport, NJ (CDW/KCDW), United States of America
Destination airport:Manchester-Boston Regional Airport, NH (MHT/KMHT), United States of America
Castle Aviation flight CSJ921, a Swearingen SA-226AT Merlin IV, N54GP, was destroyed when it crashed into the bank of the Merimack River, about 600 m short of the threshold of runway 6 at Manchester-Boston Regional Airport, NH (MHT), New Hampshire, USA. The sole pilot onboard was fatally injured.
The airplane was on the ILS approach to runway 6 at Manchester Boston Regional Airport in darkness. During the approach, the pilot reported an engine failure at 23:30:42 but did not specify which engine. The aircraft crashed nine seconds later.
During that last 9-second period of the flight, the airplane’s groundspeed slowed from 99 kts to 88 kts, as it descended about 400 ft in a slight left turn to impact (the airplane’s minimum controllable airspeed was 92 kts). The slowing left turn, in conjunction with left wing low impact signatures observed at the accident site were consistent with a loss of control just prior to impact.

Probable Cause:

Probable Cause: The pilot's failure to secure and feather the left engine and increase power on the right engine after a perceived loss of engine power in the left engine, which resulted in a loss of control and impact with terrain just short of the runway. Contributing to the accident was a reduction in engine power from the left engine due to a 1st stage turbine blade midspan separation and material loss in the 2nd stage stator that were the result of engine operation at high temperatures for an extended period of time.

Accident investigation:

Investigating agency: NTSB
Status: Investigation completed
Duration: 2 years
Accident number: ERA22FA086
Download report: Summary report


Loss of control

» Flightaware Flight track
» ADSBexchange flight track

METAR Weather report:
04:21 UTC / 23:21 local time:
SPECI KMHT 110421Z 00000KT 10SM BKN017 OVC075 M02/M05 A3016
time 0421Z, wind calm, visibility 10 statute miles, broken 1,700, overcast 7,500


photo of Swearingen-SA-226AT-Merlin-IV-N54GP
accident date: 10-12-2021
type: Swearingen SA-226AT Merlin IV
registration: N54GP

Video, social media

This map shows the airport of departure and the intended destination of the flight. The line is connecting ADS-B datapoints from AX.
Distance from Caldwell Wright Airport, NJ to Manchester-Boston Regional Airport, NH as the crow flies is 326 km (204 miles).
Accident location: Approximate; accuracy within a few kilometers.

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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Merlin IV

  • ca 70 built
  • 22nd loss
  • 9th fatal accident
  • The worst accident
» safety profile

 United States of America
  • 60th worst accident
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