Associated E120 at Lagos on Oct 3rd 2013, lost height after takeoff
Last Update: April 18, 2018 / 14:51:11 GMT/Zulu time
Incident Facts
Date of incident
Oct 3, 2013
Classification
Crash
Aircraft Registration
5N-BJY
Aircraft Type
Embraer EMB-120 Brasilia
ICAO Type Designator
E120
Causal Factors
- The decision of the crew to continue the take-off despite the abnormal No. 2 Propeller rpm indication.
- Low altitude stall because of low thrust at start of roll for take-off from No. 2 Engine caused by an undetermined malfunction of the propeller control unit.
Contributory Factors
- The aircraft was rotated before attaining V1.
- The decision to continue the take-off with flap configuration warning and auto-feather warning at low speed.
- Poor professional conduct of the flight crew.
- Inadequate application of Crew Resource Management (CRM) principles.
- Poor company culture.
- Inadequate regulatory oversight.
The NAIB analysed that both engines were operating normally. However, the left hand torque indication was stuck at 76% after engine start when it should have been 22%. The crew tried to correct by performing an EEC test, but the problem persisted. The engine should have been shut down at this point, however, the crew continued without reference to the MEL as required. The continuation of a flight with inoperative torque indicator was not permitted.
While taxiing out the crew suspect the torque indication was due to an EEC problem and decided to use engine temperatur indication T6 for adjusting the engine. However, there is no such procedure.
The NAIB wrote:
During taxi, Take-off Flaps (150) was selected by the crew and the indications were normal at this point. However, there was some evidence from the CVR transcript that the crew agreed that if the Take-off Flaps aural warning came on during the take-off roll, they will perform a flapless take-off “again”. This suggested that the crew had previously performed a flapless take-off. There is no flappless take-off procedure in the Operations Manual/SOP.
During the take-off roll, there was continous “Take-off Flap” configuration warnings which the crew disregarded and continued the take-off roll. The take-off should have been aborted at this point.
“Auto Feather” aural warning is an indication to the crew that the auto feather system is not available. After setting take-off power, the “Auto Feather” aural warning came on. At this point the crew should have aborted the take-off but elected to continue and ignored the warning.
During take-off, No. 1 Propeller RPM was indicating 100% and No. 2 Propeller RPM was indicating 55%. Fuel flow for Engine No 1 of about 750pph and Engine No 2 about 640pph. All other parameters for both engines were within limits. The No. 2 Propeller RPM was too low, which should have necessitated the crew to abort the take-off.
Examination of No. 2 Propeller Control Unit (PCU) Ball Screw indicated a propeller blade angle of about 100 to feather position which is not consistent with a blade angle of selected condition lever (max RPM) for take-off power.
The discrepancy between the actual No. 2 Propeller angle and the angle commanded by the crew is a strong indication that there was a malfunction inside the PCU as at the time the take-off power was set, which led the No. 2 Propeller to have an uncommanded high blade angle.
This investigation could not determine the reason for the PCU action which led to the low propeller RPM during take-off.
The NAIB further analysed that the aircraft had not been operated for almost a year and was being returned to service with the operator developing some pressure to perform the flight. The NAIB wrote: "It is evident that there was company pressure on the crew to operate the aircraft on that day, not minding all indication and warnings to the crew, they still decided to carry on with the flight. The investigation also discovered that the staff of the company had not been paid for sometime before the flight. The company was contracted/chartered to conduct the flight. The company must have desperately wanted to conduct the flight to justify the payment received, this in turn influenced the crew to insist on conducting the flight despite the fact that it was apparent to them that the aircraft was not airworthy."
The NAIB analysed the FDR data:
FDR readout revealed that following during take-off: NH for Engine 1 was 95% RPM and for Engine 2 was 94% RPM. NL for Engine 1 was 92% RPM and for Engine 2 was 93% RPM. The torque for Engine 1 was stuck at 76% and torque for Engine 2 was about 100%. The T6 (temperature) of 620oC for Engine No 1 and 610oC for Engine No 2, with a fuel flow for Engine No 1 of about 750pph and Engine No 2 about 640pph.
Incident Facts
Date of incident
Oct 3, 2013
Classification
Crash
Aircraft Registration
5N-BJY
Aircraft Type
Embraer EMB-120 Brasilia
ICAO Type Designator
E120
This article is published under license from Avherald.com. © of text by Avherald.com.
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