Crashed Dana MD-83 crew
feared reprisal over emergency
14 MARCH, 2017 - SOURCE:
FLIGHTGLOBAL PRO - BY: DAVID KAMINSKI-MORROW - LONDON
Nigerian
investigators have disclosed that the crew of a Dana Air Boeing MD-83 failed to
take emergency action in response to a serious engine problem, apparently in
fear of attracting attention from regulators, before the jet experienced
dual-engine power loss and crashed on approach to Lagos.
The crew had been discussing a
discrepancy in the thrust from one of the aircraft’s Pratt & Whitney JT8D
engines early into the fatal flight from Abuja.
But the Nigerian Accident
Investigation Bureau inquiry found that the MD-83 did not return to Abuja, and
overflew several alternate airports – including Akure and Ibadan – where an
emergency landing could have been made.
“At one time the pilot asserted
that the aircraft could not quit on them,” says the inquiry into the 3 June
2012 crash. “At another time, the captain said declaring an emergency would
make [the Nigerian Civil Aviation Authority] come after them.
“The delay to declare an
emergency due to unexplained fear of the regulatory body compounded their
problems.”
Both Pratt & Whitney JT8D
engines failed to deliver commanded thrust during final approach to Lagos and
the aircraft crashed with the loss of all 153 occupants as well as six people
on the ground.
No flight-data recorder
information was available to the Nigerian Accident Investigation Bureau and the
inquiry has had to rely heavily on the cockpit-voice recorder.
The final inquiry report
contains a confusing record of the accident sequence, particularly regarding
the timing of events.
But it states that the
cockpit-voice recorder captured some 30min of the flight and, at the point the
recording started, some 16min after the jet was airborne, the pilots were
already discussing an abnormal condition regarding the correlation between
thrust setting and the engine power indication.
Audio spectrum analysis by US
investigators and Pratt & Whitney has proven “inconclusive”, says
the inquiry. “No definitive outcome was established.” It states that, while the
problem started with the left-hand engine, no flame-out was established.
While the crew initially did not
express concern about the condition in the engine, they became “increasingly”
worried as the flight progressed, says the inquiry. But the crew neither
declared an emergency nor called for the abnormal checklist to diagnose the
problem.
During preparations for the
approach, the crew confirmed there was no throttle response from the left
engine, and the captain took over the controls. The crew opted for an approach
to Lagos’ runway 18R but still did not transmit any distress call.
With confirmation of throttle
response from the right engine, the anti-ice, ignition and bleed air were
switched off. The crew received vectors from the radar controller and started
configuring the MD-83 for landing, by deploying the flaps.
“Subsequently the problem became
compounded as thrust was required to continue the final approach,” says the
inquiry, pointing out that there was no evidence of an attempt to follow an
engine-out descent profile. The landing-gear, it adds, was deployed after an
audio alert from the ground-proximity warning system.
The aircraft increased its rate
of descent as it passed 5,000ft some 15nm from Lagos. About 1min later the
first officer asked whether both engines had “come up”, to which the captain
responded: “Negative.”
Both engines at this point were
failing to deliver the commanded thrust, says the inquiry, and the first
officer asked the captain whether he should declare an emergency. The crew
agreed to a distress call, transmitting: “Dual engine failure, negative
response from throttles.”
“Though there was loss in engine
power, there was no evidence of engine flame-out since the crew were able to
select flaps, lower and retract the landing-gear as evident on the
[cockpit-voice recorder transcript,” says the inquiry.
The radar controller instructed
the flight to contact Lagos tower, but the crew was unable to select the tower
frequency.
Investigators state that the
crew discussed switching to runway 18L, offset further to the north, and the
captain instructed a retraction of flaps and landing-gear. But the captain,
having expressed concern about a possible stall, reiterated that he had “lost
everything” and “lost both engines”, and called for various items – including
“relight”, “ignition override” and “just anything” – which might help in the
final moments of the flight.
Attempts to maintain altitude
with manual control were unsuccessful, and automated warnings about the
aircraft and the retracted landing-gear continued until impact in a
densely-populated area some 8km north of the airport, on the approach
centreline for runway 18R.
Investigators state that, while
the engine power loss directly led to the crash, the crew’s “inappropriate
omission” of checklist use and “inability to appreciate the severity” of the
problem contributed to the failure to divert to an alternate airport.
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