Skyward F50 at Nairobi on Jul 2nd 2014, lost height after takeoff and impacted building
Last Update: February 20, 2020 / 17:49:32 GMT/Zulu time
Incident Facts
Date of incident
Jul 2, 2014
Classification
Crash
Airline
Skyward International Aviation
Departure
Nairobi, Kenya
Destination
Mogadishu, Somalia
Aircraft Registration
5Y-CET
Aircraft Type
Fokker 50
ICAO Type Designator
F50
Airport ICAO Code
HKJK
The airport reported the aircraft crashed shortly after takeoff hitting a lightpole and impacting a commercial building that was basically empty. All 4 occupants perished in the impact, all 4 bodies have been recovered.
On March 3rd 2017 The Aviation Herald managed to get hold of an interim report dated Jul 10th 2015.
The investigation reported the aircraft departed about 500kg over maximum takeoff weight. About 8 seconds after the takeoff run was initiated aural warning alerts started, which the flight crew made reference to also in combination with visual indications, the takeoff run was continued however. The #1 propeller's rpm dropped from about 100% to about 50% and remained there for the remainder of the flight, at the same time the left engine's torque increased to 110%, the right hand engine operated normally throughout the flight. The aircraft became airborne at 100 KIAS near the end of runway 06 which is 4,117 meters long, climbed to about 50 feet AGL but never above, continuously drifted to the left and impacted a building about 2.1km northnortheast of the runway end at a 120 degrees left bank.
The investigation reported that the accident captain had flown the aircraft into Nairobi the previous day. The cockpit voice recorder revealed aural warning sounds similiar to the accident flight during that flight, too.
The captain (ATPL, 14,531 hours total, 6,821 hours in command on type) was assisted by a first officer (CPL, 823 hours total, 513 hours on type).
The investigation wrote: "The accident airplane had about 27,243 and 26,358, respectively, of total hours and total cycles since new. The no. 1 and no. 2 engines, respectively, had 19,343 and 32,145 hours since new. The no. 1 propeller had about 33,208 and 7,064 hours, respectively, since new and since overhaul, the airplane was acquired in April 2014 from an operator in The Netherland and ferried to Kenya in early May 2014 where it was subsequently operated for 92 hours at the time of the accident."
So far, although the interim report indicates a final report was estimated for end of 2015 there is no indication of such a final report.
On Feb 20th 2020 Kenya's Aircraft Accident Investigation Department (AAID) released their final report, dated Nov 26th 2019, concluding the probable cause of the crash was:
The probable cause of the accident was the decision by the crew to conduct the flight with a known mechanical problem and their failure to abort or reject the takeoff after receiving twenty seven cautions.
The report does not mention any victims on the ground, instead it states to other injuries (on the ground) as "not applicable" while providing 0 to other fatalities or other uninjured.
The AAID described the sequence of events:
the flight was cleared for takeoff at 0112.30. At 01.11.58, both engines accelerated to a high power setting with engine no. 1 stabilizing at 78% torque, 100% propeller speed and engine 2 stabilizing at 80% torque, 99% propeller speed. About six seconds later, the Capt indicates “power is set”. About 2 seconds afterwards the Capt indicated “the auto-feather is off, left” and then 5 seconds later, the FO calls out “seven eighty” (?).
About 16 seconds after initial engine acceleration was applied, the first of a series of three chimes audio alerts occurred, and continued at 1 second interval throughout the CVR recording. Immediately after the initial chimes, the Capt said “you see” and “how much is that?”. The FO responded “okay niner”. The Capt then asked “it has gotten to?” The FO replied “thirty four thirty ninety two” and shortly afterward “the left one is thirty”
About 24 seconds after initial engine acceleration, engine 1 torque climbs over a period of 2 seconds to a recorded value of 119.9%, the maximum value the recorder is capable of recording. Simultaneously Engine 1 propeller speed falls from 100% to 57%. Other engine shaft speeds remain at approximately their original high power values. Airspeed at the point this change occurs was less than 30 knots. During this period, the FO called out “one twenty two now [pause] torque”. The Capt responded “it is rising eh? The FO then noted “torque one twenty six now”. About 31 seconds after initial engine acceleration, the FO called out “okay speed alive sixty”. About a second later the Capt asked “do we reduce or”? The FO responded “we can just cut”. The Capt inquired “do we abort or continue?” The FO responded, “okay one one twelve and nine four point three” and then “okay one sixteen [pause] ninety four.” The Capt acknowledged “yeah okay”
About 47 seconds after initial engine acceleration, the Capt said twice “did I reduce it?”and the FO responded sequentially “yeah” and “okay”]
About 52 seconds after initial engine acceleration, the Capt asked “how is it now?” and the FO replied “yeah one oh two [pause] ninety four”. About 7 seconds later the FO called out “okay, one sixteen ninety four”.
About 1 minute after initial engine acceleration, the Capt inquired “Is it really going?” The FO replied “one oh one, ninety five”. The Capt acknowledged and shortly afterward he queried “is it going really, is the aircraft really moving”. The FO responded “okay, one oh one, ninety five”. About 4 seconds later, the Capt indicated “it is not giving power”
About 1 minute 9 seconds after the initial engine acceleration the FO called out “okay speed has now reached about hundred”. The Capt responded “oh yeah” and immediately afterward the FO called out “okay one eleven, ninety five”.
About 1 minute 18 seconds after the initial engine acceleration, the FO indicated “hundred now”. The Capt acknowledged.
About 1 minute 26 seconds after the initial engine acceleration, the FO called out “V one V R rotate”
About 1 minute 33 seconds after the initial engine acceleration a transition of the airplane from ground to air mode is recorded and the pressure altitude begins to climb along with the Capt immediately afterward expressing two exclamations.
Following the transition to air mode there were 51 seconds of flight recorder data before the recording ended. During this time and over a period of about 3 seconds, the FO calls out “positive rate of climb” and the Capt responded “gear up”. About 3 second later, the Capt expressed “it doesn’t have power [pause] it’s on one side.” About 6 seconds afterward, the FO said “we can also turn back” .
About 3 seconds later the first of seven “don’t sink” (GPWS aural warning alerts) begins over a period of 23 seconds. After the second GPWS alert the Capt queried “ok, we’re ok?” After the third GPWS alert, the FO said “we can turn back” and the Capt immediately responded “let’s just go”. The FO replied “okay”.
After the fifth GPWS alert, the Capt indicated “and this one is showing one fourteen” and then queried? “we can turn back?”. About 2 seconds later, the FO called out “okay speed is one hundred” and the Capt responded “but this one has nothing” About 1 second later and about the time of the sixth GPW alert, JKIA control tower radioed “five yankee charlie echo tango contact radar one two three decimal three. Good morning.”
After the seventh GPWS alert the recording ended about 13 seconds later. During this time, the controller called the aircraft again. The Capt expressed “tell him [pause] tell him we have no power”. The last CVR data indicates the FO radioed, “ah tower charlie echo” and the transmission abruptly ended along with simultaneous sounds of distress.
According to FDR data, about 15 seconds after the airplane transitioned from ground to air mode the recorded altitude peaked about 5060 feet and accompanied by a maximum airspeed of 100 knots. Along with a variation of airspeed between 90 knots and 100 knots for the remainder of the recording, during the following 20 seconds the altitude decreased to about 5000 feet and then increased to 5050 feet over the next 10 seconds where it remained until the recording ended at 1.14.27.
The aircraft crashed during the hours of darkness at geographical coordinates of 01° 17’16”S, 36° 57’5”E.
The captain (54, ATPL, 14,531 hours total, 6,821 hours on type in command) was pilot flying, the first officer (CPL, 823 hours total, 513 hours on type) was pilot monitoring.
According to the load sheet the takeoff weight, including 5000 kg of cargo (maximum payload permitted 5000kg), was 20,167 kg below the maximum takeoff weight of 20,820 kg.
The cargo was weighed after the accident and was found to be 5,520 kg. Including the weight of the two flight crew (assumed 75kg each) the actual takeoff mass was computed at 21,087kg, 267kg above MTOW (editorial note: the weight and balance computations in the final report are confusing and inconsistent, to say at least, for example the report states the 22,517kg was only 267kg above the MTOW of 20,820kg). Comparing the load sheet prepared for the flight and the computation of the report it turns out, that the final report computed the landing mass (LM) by adding the trip fuel to the takeoff mass of 21,087 kg thus resulting in 22,517kg which then went into the text of the report as TOW.
However, in the analysis the AAID states with respect to weighing the actual cargo and the numbers above:
Calculations of the aircraft weight and balance that included the post-accident measured weights of most of the cargo determined that at takeoff the airplane weight was between 0.5 and 1.5 tonnes over the maximum certified gross weight. Of note is that AAID was unable to transport the entire consignment of cargo from the accident site. It is estimated that 0.5 – 1.5 tonnes was left on site and not weighed. It is further estimated that some of the cargo was pilfered at the site prior to the arrival of security personnel. That notwithstanding, the cargo that was actually weighed was 0.5 tonnes in excess of what was stated in the flight load sheet.
The AAID analysed:
The cockpit voice recorder (CVR) data revealed aural warning alerts began about 8 seconds after the takeoff roll was initiated of which thereafter the flight crew also made reference to indications associated with visual warning alerts. However, despite the various alerts (about 27) the flight crew continued the takeoff. The flight data recorder data showed that no. 1 propeller rpm reduced from 100% to 50% where it stabilized at for the remainder of the flight. The decrease in propeller rpm corresponded with an increase of the no. 1 engine torque to about 110% along with the occurrence of the aural warning alerts. According to radar data, the lift-off occurred near the end of the runway.
The ‘triple chime’ is the highest level of alert to the crew and indicates fire/smoke warnings, aircraft configuration warnings or aircraft systems malfunction warnings. As for the engines, it may indicate an engine failure, engine fire, too high turbine inlet temperature (I.T.T.) or engine oil pressure drop. In this case, the I.T.T was operating normally and therefore it was not a factor. Triple chimes warnings require immediate action by the crew. As for the engines, as it was the case, it required to abort the take-off because the aircraft speed was below V1. If it occurs when airborne, it required the immediate shut down engine #1
The no. 2 engine operated normally throughout the entire flight.
The investigation revealed that the day before the accident, the airplane was repositioned from Nairobi-Wilson Airport to JKIA . The flight was commanded by the accident captain. During that flight, the CVR data disclosed warning alerts similar to those of the accident flight accompanied by the flight crew discussion on the interpretation and significance of the alerts. The investigation did not reveal any actions undertaken before the accident to address any irregularities that may have been associated with the warning alerts during the repositioning flight.
Metars:
HKJK 020300Z 23004KT 9999 BKN018 15/12 Q1025
HKJK 020200Z 22005KT 9999 BKN018 15/13 Q1025
HKJK 020100Z 31003KT 9999 BKN018 15/13 Q1024
HKJK 020000Z 35005KT 9999 BKN018 15/13 Q1024
HKJK 012300Z 32004KT 9999 BKN019 16/13 Q1025
HKJK 012200Z VRB02KT 9999 BKN020 16/13 Q1025
Incident Facts
Date of incident
Jul 2, 2014
Classification
Crash
Airline
Skyward International Aviation
Departure
Nairobi, Kenya
Destination
Mogadishu, Somalia
Aircraft Registration
5Y-CET
Aircraft Type
Fokker 50
ICAO Type Designator
F50
Airport ICAO Code
HKJK
This article is published under license from Avherald.com. © of text by Avherald.com.
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