REPUBLIC OF KENYA

MINISTRY OF TRANSPORT AND INFRASTRUCTURE

AIR ACCIDENT INVESTIGATION

FINAL REPORT 5Y-VVQ 16.10.2013

P.O. Box 52692- 00200 Nairobi

Telephone: 254-20-2729200 Fax: 254-20-2737320

CIVIL AIRCRAFT FINAL ACCIDENT REPORT

CAV/ACC/VVQ/09

OPERATOR: BLUEBIRD AVIATION LIMITED

OWNER: BLUEBIRD AVIATION LIMITED

AIRCRAFT: BEECHCRAFT 1900D

REGISTRATION: 5Y-VVQ

PLACE: WILSON AIRPORT (HKNW)

Co-ordinates 01°19′18″S 36°48′54″E

DATE: 9 NOVEMBER 2009

TIME: 0517

All times given in this report is Coordinated Universal Time (UTC)

East African Local Time is UTC plus 3 hours.

TABLE OF CONTENTS SYNOPSIS .................................................................................................................................................. 7

1. FACTUAL INFORMATION ............................................................................................................. 9

1.1. History of Flight ....................................................................................................................... 9

1.2. Injuries to persons ...................................................................................................................... 10

1.3. Damage to Aircraft ................................................................................................................ 11

1.4. Other damage ......................................................................................................................... 11

1.5. Personnel Information ......................................................................................................... 11

1.5.1. The Captain ..................................................................................................................... 11

1.5.2. The First Officer ............................................................................................................. 12

1.5.3. Certifying Staff ............................................................................................................... 14

1.6. Aircraft Information .............................................................................................................. 15

1.6.1. General ............................................................................................................................. 15

1.6.2. Low oil pressure warning ............................................................................................ 16

1.6.3. One engine inoperative approach and landing .................................................... 16

1.6.4. Airspeed Limitations .................................................................................................... 17

1.6.5. Mass and Balance ......................................................................................................... 18

1.7. Meteorological Information ................................................................................................ 19

1.8. Aids to navigation ................................................................................................................. 19

1.9. Communications ................................................................................................................... 19

1.10. Aerodrome Information ................................................................................................... 20

1.11. Flight Recorders ................................................................................................................. 20

1.11.1. Cockpit Voice Recorder ........................................................................................... 20

1.11.2. Flight Data Recorder ................................................................................................ 20

1.12. Wreckage and Impact Information .............................................................................. 21

1.13. Medical and Pathological Information ........................................................................ 22

1.14. Fire ......................................................................................................................................... 22

1.15. Survival Aspects ................................................................................................................ 22

1.16. Operation of Multi-engine Aircraft with One Engine Inoperative ...................... 23

1.16.1. Air minimum control speed (VMCA) ....................................................................... 23

1.16.2. The ‘P’ Factor and Effect of Loss of ‘Critical Engine’ ..................................... 25

1.17. Organizational and Management Information ......................................................... 26

1.17.1. Bluebird Aviation Limited ....................................................................................... 26

1.17.2. Kenya Civil Aviation Authority .............................................................................. 26

1.18. Additional Information .................................................................................................... 27

1.19. Useful and Effective Investigative Techniques ......................................................... 27

2. ANALYSIS ......................................................................................................................................... 28

3. CONCLUSIONS .............................................................................................................................. 31

3.1. Findings .................................................................................................................................... 31

3.2. Probable Cause ...................................................................................................................... 32

4. SAFETY RECOMMENDATIONS ................................................................................................ 32

APPENDICES .......................................................................................................................................... 33

Appendix I - FDR Plots .................................................................................................................... 33

Appendix II – Wilson Airport Chart ............................................................................................. 33

Appendix III - ATC Tape Transcript ............................................................................................ 33

Appendix IV – Radar Data .............................................................................................................. 33

Appendix V - Photographs ............................................................................................................. 33

SYNOPSIS

The Air Accident Investigation Department was notified of an accident by

Wilson Airport Air Traffic Control Tower at approximately 0525 on 9 November

2009. An Investigation Team comprising of officers from Air Accident

Investigation Department (AAID) arrived at the accident scene about twenty

minutes after the crash to carry out on-site investigation.

In conformity with international standards, ICAO and State of Design and

Manufacture were immediately notified about the accident. The State of Design

and Manufacture sent an accredited representative to participate in the

investigation.

At about 0517 on November 9 2009, a Beechcraft 1900D registration 5Y-VVQ

operated by Bluebird Aviation Limited, crashed on final approach to runway 32

after being cleared to land. The pilot was doing a single engine approach on the

twin engine aircraft after a precautionary shut down of the left engine. The

aircraft was operating under Commercial Air Transport Category (Passenger)

and was on a routine flight to deliver cargo to Somalia. Forty four (44) minutes

after take-off, the captain reported that the aircraft had developed a technical

problem and he was turning back. There were two persons on board – The

Captain and First Officer. The Captain was fatally injured whereas the First

Officer sustained serious injuries. The aircraft was completely destroyed by

impact forces and post crash fire.

1. FACTUAL INFORMATION

1.1. History of Flight

On November 9 2009, 5Y-VVQ operated by Bluebird Aviation Limited was on a

routine Commercial Air Transport (Cargo) flight from Wilson Airport (HKNW)

destined for Guryell, Somalia. The aircraft was loaded with cargo of khat (miraa).

The flight crew consisted of the Captain and First Officer. The aircraft departed

Wilson Airport at 0339 with its fuel tanks having been filled with 1950kg of jet

fuel. The Flight Plan filed with Air Traffic Services (ATS) indicated an endurance

of 4 hours. Cruise speed was indicated as 260 knots at FL250. Alternate

aerodromes as per the Flight Plan were Belete Uen (HCMN) and Galcaio (HCMR)

Airports both in Somalia.

Taxi, take off and climb were uneventful. However, at 0423 and flying at FL230

the crew contacted Nairobi Area Control Centre (ACC) and requested for a turn

back to Wilson Airport due to a ‘slight problem’. At about the same time, the

aircraft made a right turn from a heading of 50° to 240° magnetic and

commenced descend. The crew reported descending to FL220 and expressed

intention to descend further to FL180. However, ACC informed 5Y-VVQ crew to

initially maintain FL200 due to traffic moving in the opposite direction. At 0428

the crew informed ACC that they were unable to maintain FL200 and requested

to descend to FL180 having crossed the opposite traffic. At 0429, the crew

confirmed to Air Traffic Control (ATC) that they were heading to Wilson Airport

and indicated that they did not require any assistance. The aircraft continued

descending until FL120. The Nairobi Approach Radar established contact with

the aircraft at 0441:10 and indicated to the crew that they were 98 nautical

miles North East of November Victor. The crew was then told to turn left to a

heading of 225° and report when they were top of descend, which they did. At

0441:38 the crew reported again that they had a ‘slight problem’ and as a

security measure they had to shut down one engine. They also expressed desire

to route direct to Silos. At 0442 5Y-VVQ aligned with the North East access lane

via Ndula Marker. At 0445, the crew confirmed to Nairobi Approach Radar that

the malfunction was on the left engine and again acknowledged that they did not

require any assistance.

At 0451, the crew requested for radar vectors for Instrument Landing System

(ILS) of runway 06 Jomo Kenyatta International Airport (JKIA) with a long final to

runway 32 of Wilson Airport. At 0509, the aircraft descended to 8000ft heading

260°. At 0514, the crew was given vectors for runway 32 Wilson Airport. At the

same time, the aircraft turned right to a heading 310° as it continued to descend

to 7000ft. The crew confirmed the vectors and at 0515 stated that they were

passing Visual Meteorological Conditions (VMC). They were also informed that the

Wilson Airport runway 32 was 6.5 nautical miles away in the two o’clock

direction. The aircraft continued to descend to 6000ft and at 0516, the crew

confirmed sight of runway 32. The crew was then transferred from the radar to

the Wilson Tower frequency for landing. 5Y-VVQ was cleared for a straight-in

approach to runway 32. Wilson Tower then communicated to the crew airfield

QNH as 1022hPa and that winds were calm. At 05:16:50, the Tower had 5Y-VVQ

visual and it was cleared to land on runway 32. At about the same time, the

aircraft made a 5° right bank and again leveled off before making a steep left

bank rising to 30° within 4 seconds. According to Tower and eyewitness

information, the aircraft appeared high on approach and on short-final, it was

observed to turn a bit to the right. This was followed by a steep left bank.

The aircraft left wing hit the ground first approximately 100 meters outside the

airport perimeter fence. The aircraft then flipped over, hitting and breaking the

airport fence and coming to rest on the left of runway 32 approximately 100

meters from its threshold. The aircraft immediately caught fire upon the impact.

Upon further investigations and interview of company personnel, it was

established that the crew had made the decision to shut down the left engine

following a low oil pressure warning. The flight crew did not declare an

emergency.

1.2. Injuries to persons

Injuries Crew Passengers Others

Fatal 1 - -

Serious 1 - -

Minor/None - -

1.3. Damage to Aircraft

The aircraft was destroyed by impact forces and the post impact fire.

1.4. Other damage

A section of the airport’s perimeter fence was also damaged.

1.5. Personnel Information

1.5.1. The Captain

The captain, a Kenyan male aged 32, had been working with Bluebird Aviation

Limited for approximately 7 years at the time of accident. He held a valid Airline

Transport Pilot License (ATPL) No. YK-4384-AL issued on 3 March 2006 by Kenya

Civil Aviation Authority (KCAA). The ATPL had coverage for aeroplanes and was

valid till 20 March 2010. The pilot also held a Multi-engine instrument rating.

Pilots logs obtained from the company indicated that the captain had flown a

total of 179.3 hours during the three months prior to the accident, 67 hours

being on the Beech 1900D aircraft type. The captain was reported to be a very

able and confident individual with no known previous incident record. There were

no complaints about him from other pilots.

The Captain held a Flight Radio Telephony Operator License YK-4384-RL which

was valid until 20 March 2010. Records indicated that he had passed instrument

rating renewal flight test on 28 January 2009 conducted on a DHC-8 aircraft. The

Captain had also passed another instrument rating renewal flight test conducted

on a Beech 1900D on 29 January 2008.

The pilot applied for inclusion of Beech 1900 as a type rating on his license on 19

September 2006 after passing the Technical Type Rating examination for the

aircraft on 17 May 2006.

There was no evidence of pilot proficiency tests conducted on the aircraft from

the records provided by KCAA.

Date of Birth/Age 11 July 1977

Sex Male

Nationality Kenyan

License No. YK-4384-AL

Type of License ATPL (Aeroplanes)

Validity of license Valid till 20th march 2010

Ratings DHC-8, Fokker 50, B1900, B200, Let 410

UVP

Profiency check Instrument rating Renewal Flight Test on

28 January 2009

Total Flying Hours 7000

Total hours as PIC 2300

Total hours on type 944

Total time (hrs) in the last 30 days 57.5

Total time (hrs) in the last 7 days 22.5

Total time (hrs) in the last 24 hours 1.6

Duty time The previous flight conducted by the pilot was on 7 November 2009 for duration of 4.4 hours. The accident flight lasted for

1.6 hours.

Medical Certificate (Class/Valid

Date)

Class 1 Medical Certificate. Examined on

11/03/2009

1.5.2. The First Officer

The First Officer (FO), a Kenyan male aged 42 at the time of accident, had been

employed at Bluebird Aviation Limited for six years prior to the date of accident.

He held a valid Airline Transport Pilot License (ATPL) – Aeroplanes No. YK-4217-

AL issued by KCAA on 22 January 2008. The license was valid until 12 March

2010. The pilot also held a valid Radio Telephony Operator’s License YK-4217-RL

which was also valid until 12 March 2010. The FO was instrument rated and at

the time of accident had a total of 448 instrument flying hours. He passed the

last instrument flying test about one year prior to the date of the accident on 10

November 2008.

On 28 December 2008, the pilot applied for inclusion of Beech 1900 as a Group I

rating on his ATPL, which was approved. Beech 1900 was included in the ATPL

as a Group I rating on 2 January 2009. At this point the pilot had a total of 92.5

hours on type. The pilot had previously applied for inclusion of Beech 1900 as a

Group II rating on 16 December 2006 with a total of 11.2 hours on type and

having passed TTR on Beech 1900 on 8 September 2005.

Records indicate that the FO last flew the accident aircraft on the day before the

accident as the PIC.

There was no evidence of pilot proficiency tests conducted on the aircraft from the

records provided by KCAA.

Date of Birth/Age 6 June 1967

Sex Male

Nationality Kenyan

Licence No YK-4217-AL

Type of Licence ATPL (Aeroplanes)

Validity of licence Valid until 12 March 2010

Ratings Group I: B1900, Cessna 310, Cessna 182, Cessna 152, Christen Husky.

Group II: DHC-8, Fokker 27-50, Let 410A, Let 410 UVP-E9, Let 410 UVP-E20

Proficiency check Instrument rating Renewal Flight Test on

10 November 2008

Total Flying Hours 6078

Total hours as PIC (on both single and multiengine aircraft)

818

Total hours as PIC on multiengine aircraft

484

Total hours on type 459.1

Total time (hrs) in the last 30 days 53

Total time (hrs) in the last 7 days 26.6

Total time (hrs) in the last 24 hours 6.8

Duty time The previous flight conducted by the pilot was on 8 November 2009 for duration of

5.2 hours. The accident flight lasted for 1.6 hours.

Medical Certificate (Class/Valid Date)

Class 1 Medical Certificate. Examined on 08/09/2009

1.5.3. Certifying Staff

Two members of certifying staff was found to have been given authorizations by

KCAA to issue Certificate of Release to Service (CRS) for maintenance carried out

on the Beech 1900D aircraft. They had not undertaken the requisite aircraft type

training. Authorization for Category ‘R’ and ‘X’ was valid until 30 march 2010

while for the Beechcraft 1900 Category ‘A’ was valid until 8 April 2010. There

were members of Certifying Staff rated on the PT6A series engines. The members

of Certifying Staff had valid Aircraft Maintenance Engineer’s licenses at the time

of accident.

1.6. Aircraft Information

1.6.1. General

Manufacturer Hawker Beechcraft Corporation

Type Beechcraft 1900D

Aircraft Serial Number UE-250

Year of manufacture 1996

Number and type of engines 2 Pratt & Whitney PT6A-67D turboprop

engines

Shaft Horsepower (Takeoff; Max

Cont.)

1279; 1214

Total Airframe hours/cycles 15,865.9/15941

Certificate of Registration Kenyan registered 16 April 2008

Certificate of Airworthiness Issued on 07 May 2009 under the

Commercial Air Transport (Passengers).

Valid until 07 May 2010.

The aircraft was previously registered in South Africa under the registration ZS-

OYH. Bluebird Aviation Limited purchased the aircraft from Skyinvest

Administration (PTY) Ltd and it was entered into the Kenyan register on 16th April

2008.

The aircraft was issued with a Certificate of Airworthiness under the category

Commercial Air Transport (Passengers) more than a year later on 7 May 2009. At

the time of accident it was being operated for the purpose of commercial air

transport of cargo.

The aircraft was equipped with two Pratt & Whitney PT6A-67D turboprop

engines. The time since new for the left engine Serial № PCE-PS0067 was

13947.8 hours, and the time since overhaul was 5111.4 hours. Time since new

for the right engine Serial № PCE-114010 was 22570 hours, and time since

overhaul was 4611. The time between overhaul (TBO) for this type of engines was

established at 6000 hours. Maintenance records indicated that the following

checks had been carried on the left engine prior to the accident: 50 hour

inspection on 18 September 2009 and a 200 hour inspection on 29 August 2009.

Engine ground runs were carried out on both occasions and results were

satisfactory. Previous maintenance records also indicated that a faulty engine low

oil pressure switch replacement had been carried out on 21 Nov 2008.

Each engine was equipped with a four-blade, full-feathering, constant-speed

Hartzell propeller of composite construction. Propeller rotation was clockwise

when viewed from the aft of the aircraft. The left engine was the ‘critical’ engine;

this is discussed at subsection 1.16.2.

1.6.2. Low oil pressure warning

The aircraft was equipped with a Low Oil Pressure annunciator for both the right

and left engines. According to the Beech 1900D Aircraft Flight Manual (AFM), oil

pressures below 90 PSI are undesirable and should be tolerated only for the

completion of the flight at a reduced power setting not to exceed 2000 foot-

pounds torque. In case of an engine oil pressure low warning, the AFM stipulates

the following emergency procedures that should be followed:

1. Confirm through the oil pressure gauge that the pressure is below 60 PSI

2. If confirmed, secure engine or land at the nearest suitable airport using the

minimum power required to sustain flight

Generally low oil pressure indication in PT6A engines may be as a result of the

following possible causes:

Oil level too low

Faulty Indicating system

Oil filter restriction

Poor adjustment of pressure regulating valve

Oil leaks

Faulty pressure relief valve

Oil pump failure

Improperly secured oil tank cap

1.6.3. One engine inoperative approach and landing

The approved AFM prescribes the following procedures that should be followed

during the execution of a one engine inoperative approach and landing.

The AFM has put a caution to pilots to ensure that they use the rudder to

maintain directional control (heading) and ailerons to maintain a 5° bank towards

the operative engine (lateral attitude). At the first sign of VMCA or stall warning

(which may be evidenced by: inability to maintain heading or lateral attitude ,

aerdynamic stall buffet, or stall warning horn sound), the pilot is cautioned to

immediately initiate recovery; reduce power to idle on the operative engine and

immediately lower the nose to regain VSSE.

From the procudres above, the it is evident that the pilot should maintain VREF

during final approach to land with one engine inoperative. VREF is directly

proportional to the stalling speed in landing configuration, VSO. With the wings

level (0° bank) and VSO at 80KIAS, the VREF will be 104KIAS.

1.6.4.

1.6.5. Airspeed Limitations

The following airspeed limitations that must be observed in the operation of the

Beech 1900D aircraft have been stipulated in the approved AFM.

1.6.6. Mass and Balance

The load and trim sheet prepared by the crew for the flight indicated that the

aircraft ramp weight was 7741kgs and the take-off weight was 7691kgs. The

takeoff weight was 99 per cent of the maximum take-off weight of 7765kgs. The

load and trim sheet also showed that the calculated take-off Centre of Gravity

(CG) was 286.2 inches aft of datum. If the flight had proceeded to the destination

of Guryell as per the flight plan, the landing weight and centre of gravity as per

load and trim sheet would have been 6693kgs and 284.8 inches aft of datum

respectively.

The aircraft’s weight and balance was calculated based on an average fuel

consumption of 352kg/hr per engine derived from the load and trim sheet data

and flight plan. This value was used for the sector with both engines operating.

For the sector with one engine inoperative, an average fuel consumption of

460Kg/hr was used, corresponding to an increase in the operative engine power

setting. The aircraft weight at the time of accident was determined to be

approximately 6761kgs with the CG position being at 284.9 inches aft of the

datum.

The Beech 1900D FAA-Approved AFM provided information on the forward and

aft CG limits. The forward CG limit for this aircraft is located 283.0 inches aft of

datum at 7765kgs weight, with a straight line variation to 274.5 inches aft of

datum at 5262kgs. The aft CG limit is located 299.9 inches aft of datum at all

weights during takeoff, climb approach and landing. The maximum landing

weight was indicated as 7604kgs in the AFM.

The take-off safety speed (V2) as per FDR data was noted to be approximately 125

knots indicated airspeed (KIAS) for a take-off mass of 7691kgs.

1.7. Meteorological Information

Weather information was available to the crew from ATC. Official Meteorology

Aerodrome Routine Weather Reports (METARs) for HKNW were issued hourly and

sometimes as conditions may warrant, such as during wind shift, change in

visibility or cloud cover.

The 0500Z METAR for HKNW indicated that wind direction was 050° at 8 knots,

visibility was better than 10 km, clouds were broken at 1700 ft, the temperature

was 18°C, dew point was 15°C, and QNH was 1022hPa. The 0600Z METAR

indicated that wind direction was 060° at 8 knots, visibility was better than 10

km, clouds were broken at 1800ft, the temperature was 19°C and, dew point was

14°C and QNH was 1022hPa.

The 0515Z METAR for HKNW provided by ATC indicated that wind direction was

010° at 5 knots. Visibility was reported to be better than 10 km and clouds were

broken at 1700 ft. The temperature was 18°C and dew point was 15°C. QNH was

1022.7hPa.

ATC tape transcripts indicated that the flight crew was informed by Tower of the

prevailing calm winds and QNH of 1022hPa just before they were cleared to land.

1.8. Aids to navigation

Wilson Airport runways 07 and 14 were equipped with Precision Approach Path

Indicators (PAPI) at the time of the accident. However, runway 32 was not

equipped with navigation aids.

1.9. Communications

The flight crew was in constant communication with the ATC from the time they

requested to turn back to Wilson Airport until when they were cleared to land on

runway 32. Radio communication at Nairobi Area Control Centre was achieved

through the frequency 121.3MHZ, at the Nairobi Approach Radar through

122.3MHZ and at Wilson Tower through 118.1MHZ. All communications were

satisfactory and no problems were reported at around the time of the accident. A

complete tape recording and transcript of the VHF transmissions between the

aircraft and ATC was made available to the investigation and has been useful in

this report.

1.10. Aerodrome Information

Wilson Airport (ICAO designation HKNW) is located five kilometers south of

Nairobi and serves both domestic and international traffic. It is located at latitude

01° 19' 18.19" S and longitude 036° 48' 53.40" E at an elevation of 5546 feet

AMSL. The aerodrome operating hours are from 0330 to 1730. The airport has

four asphalt runways 07/25 (4800×79 ft), 14/32 (5118×75 ft). The airport is not

equipped with ILS equipment. Approach, threshold and runway lighting is not

provided for runway 14/32.

The airport is also equipped with a control tower normally manned by four air

traffic controllers per shift. Approach control is achieved through monitoring of

radar display monitors at the Visual Control Room. Radar surveillance data was

obtained from Nairobi Approach Radar.

1.11. Flight Recorders

In accordance with regulatory requirements the aircraft was equipped with both a

cockpit voice recorder (CVR) and a flight data recorder (FDR). Both were easily

and immediately recovered in satisfactory condition from the wreckage after the

accident and sent to National Transportation Safety Board (NTSB) laboratory in

the USA for readout.

1.11.1. Cockpit Voice Recorder

The CVR installed in the aircraft was a Fairchild model A100S, Part No.S100-

0080-00, Serial Number 01222. It records 30 minutes of digital audio stored in

solid-state memory modules. The CVR has four recording channels: One channel

for each flight crew and one for the cockpit area microphone. The information

obtained from the CVR did not correlate in any way with the activities of the

accident flight.

1.11.2. Flight Data Recorder

The aircraft was installed with a Fairchild Digital FDR model F800, Part

No.17M703-274, Serial Number 5409. According to the data received after the

readout, there were a total of nine parameters available for analysis. These

included vertical and longitudinal accelerations, indicated airspeed, pressure

altitude, pitch attitude, and pitch control position, magnetic heading, roll attitude

and time. The FDR did not record any engine parameters. All the data from the

accident flight was recorded from take-off until the time of the accident. A

graphical presentation of these parameters is attached to this report as appendix

I.

1.12. Wreckage and Impact Information

The aircraft main wreckage was located to the left of runway 32. It came to rest

100 meters from the threshold of the runway on a bearing of approximately 170°.

Other pieces of wreckage were distributed through a distance of approximately

200 meters from the point of initial impact. The track of the crash path was

approximately 290°.

The terrain of the wreckage path was essentially a flat grass area starting

approximately 100 meters outside the airport perimeter fence. There was a

drainage trench between the main wreckage and other pieces of wreckage in the

trail running on a bearing of approximately 140°. The ground was generally dry.

The initial impact marks of the aircraft were minor ground scratches consistent

with those made by the wing tip. The second impact generated a larger

depression on the ground and there was evidence of fuel spill around this area.

Propeller blade pieces were located to the left of the wreckage path, outside the

airport perimeter fence. A landing gear door was located to the right of the

wreckage trail, outside the airport perimeter fence.

A 15-meter section of the airport perimeter fence was broken and pieces of wire

consistent with that used on the fence were found on the main wreckage. Some

burnt debris was found before the main wreckage. Some grass was also burnt

along the wreckage tail.

Other major pieces of wreckage found on the inside of the airport perimeter fence

along the wreckage path before the main wreckage were the left winglet, right

aileron, left wing section, propeller blade pieces, antenna, left aileron and the stall

warning unit. The left engine was found detached on the drainage trench just

beside the main wreckage.

The main wreckage was mainly composed of the fuselage with the tail section

broken but largely undamaged. The fuselage came to rest with its left side facing

upwards. There were signs of fuel spill on the left hand side of the fuselage and

the right hand side of the aircraft tail section. The right wing was intact with the

main wreckage but was burnt approximately one-third length from the tip. The

right engine also remained intact with the main wreckage. The aircraft nose

section was extensively damaged. The cockpit section separated from the fuselage

structure but remained close. Cargo debris was spread around the area close to

the main wreckage.

Examination of the instrument panel and cockpit switch positions revealed the

following on the pilot’s side: the airspeed indicator pointed on 114KIAS; the

altimeter needle pointed at 5450 feet; left torque indication was 700ft.lb; propeller

RPM needle pointed at 200; oil pressure indication was 60°C; clock indication

was 2.25; the fire handle was in position; turbine RPM indicator was damaged;

fuel flow and temperature indicators were off scale. The copilot’s propeller RPM

needle pointed at 1500. The right hand torque indicator and the turbine RPM

needle were missing. All power controls were in the forward position.

1.13. Medical and Pathological Information

The Captain sustained fatal injuries as a result of the impact. The FO sustained

serious injuries and was hospitalized for a long period.

1.14. Fire

The integrity of the left wing fuel tanks was compromised during the second

impact as evidenced by signs of fuel spill from this point. Some grass was burnt

along the wreckage trail. Fire on the main wreckage was limited to the right wing

and on the left side, it was limited to the area forward of the rear cargo door.

There was evidence of fuel spill on the left hand side of fuselage and the right

hand side of the tail section.

ATC informed the Wilson Airport Fire Services that 5Y-VVQ was returning back to

the Airport and they were on standby at the time even despite the Captain not

declaring an emergency. The Emergency Fire and Rescue personnel responded

immediately with a fire truck and extinguished the fire after the crash.

1.15. Survival Aspects

The nose section and cockpit area of the aircraft received substantial crushing

damage that destroyed livable volume surrounding the occupants. This section

was crumbled and was almost separated from the main wreckage.

The crew was rescued from the mangled cockpit by emergency rescue personnel

and they were found to have sustained serious impact injuries. The pilot

succumbed to the injuries and the copilot survived.

1.16. Operation of Multi-engine Aircraft with One Engine

Inoperative

1.16.1. Air minimum control speed (VMCA)

Basically, when a multi-engine aircraft equipped with wing-mounted engines suffers a partial or complete power loss on one engine, it will experience an

asymmetric thrust about its centerline. Consequently, the aircraft will yaw towards the failed engine, and the pilot must overcome the asymmetrical thrust by creating a counteracting moment by applying rudder towards the operative

engine. With the rudder fully deflected, the yawing moment will depend on the velocity of airflow across the rudder – which in turn is dependent on the airspeed.

If the aircraft decelerates, the airspeed will eventually reach a speed below which the rudder moment can no longer balance the asymmetric thrust moment and directional control will then be lost.

In Figure 1 below, to maintain a state of equilibrium, a deflected rudder (δr)

generates a side force (Yδr) that causes a yawing moment (Nδr) to counter the

asymmetrical thrust yawing moment (NT) generated by the thrust on the

operating engine. Yδr also causes acceleration to the dead engine side and a

sideslip (β) develops. The sideslip creates a positive angle of attack of the airflow over the rudder. The acceleration will continue until a state of equilibrium is

attained. The aerodynamic side force Yδr is proportional to the square of the

airspeed (V2).

1. 2. Figures 1: Forces and moments Figure 2: Forces and moments – acting on an aircraft with one engine with small bank angle away inoperative - wings kept level from inoperative engine

VMCA is the minimum speed at which it is possible to maintain directional control of the aircraft with the critical engine inoperative. It is the lowest airspeed at

which straight flight can just be maintained while either the rudder or the ailerons are maximum deflected. When flown at VMCA, and with a bank angle of about five degrees towards the operative engine, the pilot should be able to

maintain directional control of the aircraft. The aircraft certification process includes demonstration of VMCA.

Sideslip causes drag which reduces the remaining single engine performance and should therefore be kept at minimum. This is achieved by a small bank angle

towards the operative engine. When banking, a component of the aircraft weight

(W), leads to a side force due to bank angle (W·sin ϕ in Figure 2), that can replace

the side force Yβ due to sideslip that was required for balance with the wings

level. Side force W·sin ϕ acts in the centre of gravity and therefore does not cause any adverse yawing moments.

VMCA is greater when the CG is at the aft limit. Since the aeroplane rotates around its CG, the moments are calculated using the CG as a reference. A rearward CG

would not affect the thrust moment, but would shorten the arm (S1) to the center

of the rudder's horizontal "lift" (Yδr) which would mean that a higher force

(airspeed) would be required to counteract the engine out yaw.

VMCA increases as the power on the operating engine is increased. With full power applied to the operative engine, as the airspeed drops below VMCA, the aeroplane

tends to roll as well as yaw into the inoperative engine. This tendency becomes greater as the airspeed is further reduced. Since this tendency must be counteracted by aileron control, the yaw condition is further aggravated by

aileron yaw (downward deflection of an aileron typically causes more profile and induced drag than an upwards deflection). If a stall should occur in this condition, a violent roll into the dead engine may be experienced. Such an event

occurring close to the ground could be disastrous. This may be avoided by maintaining airspeed above VMCA at all times during single engine operation. If the

airspeed should fall below VMCA, then power must be reduced on the operative engine and the aeroplane must be banked at least 5 degrees toward the operative engine if the aeroplane is to be safely controlled.

VMCA increases with increased drag on the inoperative engine. A windmilling

propeller will increase the amount of drag being experienced by the inoperative engine. This is because, as the propeller RPM decreases following an engine failure or in-flight shutdown, the angle of attack of the blades eventually becomes

negative, and blade thrust commences to act in a rearward direction. VMCA is highest, therefore, when the critical engine propeller is windmilling at the low pitch, high RPM angle.

The State of Manufacture through the Federal Aviation Administration (FAA) has

published advisory material on the effect of bank angle on VMCA, based on information contained in FAA-H-8083-3 Airplane Flying Handbook. The Handbook states that banking towards the operative engine would reduce VMCA,

and away from the operative engine would increase VMCA by about three KIAS per degree of bank angle less than 5°. According to the Handbook, loss of directional

control may be experienced at speeds of almost 20 knots above the published VMCA when the wings are held level.

1.16.2. The ‘P’ Factor and Effect of Loss of ‘Critical Engine’

For propellers rotating clockwise when viewed from the rear of the aircraft, the downward moving propeller blades of each engine develop more thrust than the upward moving blades. This is because the downward moving propeller blades

have a greater angle of attack than upward moving blades when the relative airflow striking the blades is not aligned with the thrust line. This asymmetrical propeller loading or ‘P’ Factor is more pronounced at a high engine power setting.

The ‘P’ Factor, results in the centre of thrust shifting to the right of the propeller centreline. The yawing moment of the right engine is therefore greater than that

of the left engine because the centre of thrust is farther from the centreline of the fuselage and thus has a longer leverage arm. When the right engine is operative

and the left engine is inoperative, the yawing moment is greater than when the left engine is operative and the right engine inoperative. Therefore, directional

control is more difficult when the left engine (the ‘critical engine’) is inoperative.

1.17. Organizational and Management Information

1.17.1. Bluebird Aviation Limited

Bluebird Aviation limited was incorporated in 1992 and at the time of accident

the company had a total of 16 aircraft fleet. The fleet was composed of Beech

1900, Let 410, Beech 200, Fokker 27-50, DHC8-100, and DHC8-400. The

company mainly conducted cargo operations.

The company had a total of 18 pilots and 10 licensed aircraft maintenance

engineers. There were also 15 aircraft technicians working at the company at the

time of accident. Fourteen of the pilots were commanders of the various aircraft

in the fleet.

Recruitment of pilots at the company was conducted from a pool of applicants

interviewed and hired based on their experiences. Upon being hired, a pilot at the

company would undergo a base check, line check and a flight check with an

experienced pilot. The company utilized training facilities in Canada and Holland

were utilized for the flight crew.

According to the company, engine failure in flight is an emergency. Pilots should

land in a suitable place in case they have an engine emergency.

1.17.2. Kenya Civil Aviation Authority

There was no evidence from the KCAA pilot records that checkout tests or pilot

proficiency checks had been carried out by the operator on the Captain and FO.

There was also no evidence of checkout flights or training flights for operation of a

twin engine aircraft with one engine inoperative. The only evidence of flight test

was during instrument rating renewals and the form D.C.A. (L) 135A was duly

filed with KCAA. This form did not include procedures for testing pilots on

handling multiengine aircraft with one engine inoperative. According to Kenya

Civil Aviation (Operation of Aircraft) Regulation 33:

(1)An operator shall ensure that piloting technique and the ability to execute emergency

procedures is checked in such a way as to demonstrate the pilot’s competence and where the

operation may be conducted under instrument flight rules, an operator shall ensure that the

pilot’s competence to comply with such rules is demonstrated to the check pilot of the operator

or to the Authority.

(2) The checks referred to in sub-regulation (1) shall be performed twice within any period of

one year, and any two such checks which are similar, and which occur within a period of four

consecutive months shall not alone satisfy this requirement.

According to the Kenya Civil Aviation (Operation of Aircraft) Regulation 82 (1):

A pilot- in- command shall land the aircraft at the nearest suitable aerodrome at which a safe

landing can be made whenever an engine of an aircraft fails or is shut down to prevent possible

damage.

KCAA could not provide a copy of the Beech 1900D Aircraft Operating Manual containing the normal, abnormal and emergency procedures relating to the operation of the aircraft and which the operator was required to submit to the

Authority in compliance with Kenya Civil Aviation (Air Operator Certificate and Administration) Regulation 32:

(1) A holder or applicant for an air operator certificate shall submit a proposed aircraft

operating manual for each type and variant of aircraft operated, containing the normal,

abnormal and emergency procedures relating to the operation of the aircraft for approval by

the Authority.

At the time of accident, there was no evidence that the CVR and FDR had been

inspected by the operator in accordance with the Kenya Civil Aviation (Instruments and Equipment) Regulations 36 and 37. There were no annual inspection reports for the recorders among the records provided by KCAA.

At the time of accident, KCAA was conducting recertification of the operator to

ascertain compliance with the then new Kenya Civil Aviation Regulations. KCAA

had an annual surveillance program in place for AOC holders. Surveillance was

in the form of annual inspections for the renewal of the AOC. Annual inspections

were supplemented by ad-hoc ramp inspections.

ATC informed the Wilson Airport Fire Services that 5Y-VVQ was returning and they were on standby and responded immediately the aircraft crashed.

1.18. Additional Information

None

1.19. Useful and Effective Investigative Techniques

None

2. ANALYSIS

Individual Actions

The circumstances of this accident were consistent with loss of control during

single engine operation of a multi-engine aircraft at speeds below VMCA. The

investigation established that the crew performed a precautionary left engine

shutdown following an engine low oil pressure warning during the outbound

flight. This was consistent with manufacturer’s procedures contained in the AFM.

The procedures indicated that at engine oil pressure below 60PSI, the pilot

should either secure the engine or land at the nearest suitable airport using the

minimum power required to sustain flight. The flight crews decided to shut down

the engine and conduct a single engine return flight to their Wilson Airport base.

The loss of altitude on the return leg was consistent with the aircraft being at an

altitude higher than single-engine ceiling.

During the final approach to runway 32 of Wilson Airport, at approximately 36

seconds before the crash, the aircraft had established a steady heading of 320°.

During the last 6 seconds before impact, the heading changes to 290°, this is

consistent with a left yaw. This is also evidenced by the direction of debris flow

after impact which was determined 290°. The aircraft bank angle was not

stabilized during the final approach. During the last one minute of the flight, the

FDR records a left bank of -15°, which was followed by a right bank of +7°. The

aircraft again banks to the left (-3°), then to the right (+3°). During the last 4

seconds of the flight, the wings are level for the first 3 seconds, before the aircraft

banks to the left. The bank angle changes from 0° to -30° within the last second

of the flight. During the last 5 seconds of the flight, the aircraft vertical

acceleration changes from 0.9g to 1.15g. The longitudinal acceleration in the last

3 seconds of the flight changes from 0.01g to 0.08g. The pitch angle in the last 1

minute of FDR recording changes from -6° to +5° just before the crash. The last

pitch angle recording in the FDR was +3°. During the last 5 minutes of FDR

recording, the aircraft airspeed increases initially from 167KIAS to 199KIAS

before decreasing steadily reaching the lowest value of 93KIAS, 4 seconds before

the end of the recording. At the end of the FDR recording, the airspeed increases

slightly to 95KIAS.

From these events, it is evident that the pilot did not maintain a 5° bank to the

operating engine as cautioned by the manufacturer in the single engine approach

and landing procedures published in the AFM. The wings were level during the

last 4 seconds of the flight, meaning that the aircraft actual VMCA was higher than

the published VMCA of 92KIAS. This is in line with the advisory information on

FAA Airplane Flying Manual FAA-H-8083-3 which indicates that VMCA would

increase at a rate of 3KIAS for every bank angle less than 5° towards the

operating engine. The manual also indicates that loss of control may be

experienced at speeds almost 20 knots above the published VMCA during single

engine operation of a multiengine aircraft. Based on this, it is highly likely that

the actual VMCA was over 107KIAS during the last 4 seconds of the flight. At this

time the aircraft indicated airspeed was 93KIAS. Loss of directional control was,

therefore, imminent.

According to the one engine inoperative approach and landing procedures in the

AFM, the pilot is required to maintain VREF airspeed during the final approach.

VREF, which depends on the stalling speed in landing configuration, was

determined to be 104KIAS. Just before the accident, the pilots were flying at a

much lower airspeed of 93KIAS.

The FDR parameters recorded during the last two seconds of the flight indicate a

rise in pitch control angle from 9° to 17°. The aircraft pitch, however, decreases

from 4° to 3° at the end of the recording. At the same time the airspeed increases

slightly from 93KIAS to 95KIAS just before the end of the recording. Longitudinal

acceleration increases from 0.03g to 0.07g while vertical acceleration increases

from 0.9g to 1.15g towards the end of the recording. The heading changed from

320° to 290° at the end of the recording. From these parameters and wreckage

information, it highly likely that, the pilot selected full power on the operating

engine inducing a left yaw during the last seconds of the flight. The situation was

aggravated by the fact that the left engine is the critical engine in Beech 1900D.

The yawing moment from the right engine thrust was, therefore, greater and

maintaining directional control was difficult under the circumstances. As the

airspeed drops below the VMCA, the aeroplane normally tends to roll as well as yaw

into the inoperative engine.

Based on the recorded radio transmissions between the pilots and the ATC, it is

evident that either the pilots did not fully comprehend the situation they were in

or they were just working in line with company policy. The pilots initially did not

disclose the kind of technical problem they were experiencing until the ATC

queried them. On more than one occasion, the pilots stated that they did not

require any assistance. The pilots never declared an emergency even though,

according to the company, engine failure is an emergency. The Captain was

reported to be very able and confident individual with no known previous incident

record.

It is also highly likely that the pilots did not adequately monitor the degrading

airspeed at the most critical phase of flight and allowed it to reduce below the

VMCA.

Local Conditions

The adverse yaw and roll and the consequent loss of control occurred at the

landing phase of flight under low altitude conditions. Low altitude meant that

recovery from this condition was practically impossible and impact with the

ground was imminent. If the condition had occurred at a higher altitude, recovery

would have been possible depending on the pilot skill, experience and knowledge.

It would have required the pilot to reduce power on the operative engine and

bank at least 5° toward the operative engine.

From the records provided by KCAA, both pilots had over 6000 total hours flying

experience. There was no evidence, however, that the pilots had experienced such

a condition before in their careers. The pilot`s reaction of selecting a higher power

setting on the operating engine as the airspeed degraded was an indication of

lack of sufficient skill. There were no records available indicating pilots training

on VMCA and safe operation of multiengine aircraft with one engine inoperative.

From ATC interview, the company was constantly in touch with them concerning

the returning aircraft. There were other suitable aerodromes en-route that the

pilots could have landed but they decided to fly all the way to Wilson Airport. It is

likely that there was company pressure to return the aircraft to base rather than

land it at other suitable aerodromes.

Risk Controls

Some of the risk controls which were in place included training on operation of

multi-engine aircraft with one engine inoperative, emergency procedures, and

procedures for handling the aircraft with one engine inoperative. Apart from the

training on single engine operation that is normally given in the course of

acquiring a multi-engine rating, there was no evidence from the records provided

by KCAA that the pilots undertook this training again after acquiring their

ratings. Emergency procedures were not adequately followed including the need

to reduce power on the operating engine to minimize yaw and 5° bank to the

operating engine.

Organizational Influences

Regulations on pilot proficiency checks, landing at the nearest and suitable

aerodrome in case of an engine failure or shutdown, and the requirement of

developing an aircraft operating manual were in place. There was, however, no

evidence from KCAA documents that pilot proficiency checks were being

conducted. The pilots did not land at the nearest suitable aerodrome after the

engine shutdown as per the regulations. They decided to fly back for 54 minutes.

There was the risk of losing the second engine with disastrous consequences. It is

likely that there was lack of adequate risk assessment of flying with one engine

back to Wilson Airport or the pilots were under a lot of pressure to return to base.

The aircraft operating manual required to be developed by the operator under

Civil Aviation Regulations was not provided to the investigation by KCAA. This

was either because the manual had not been developed by the company or the

KCAA copy was not available.

3. CONCLUSIONS

3.1. Findings

1. The aircraft left engine had been shut down as a precaution following

engine low pressure warning.

2. The crew made a decision to fly to Wilson Airport with one engine

inoperative even though there was other suitable and closer aerodromes

en-route.

3. The pilots held the appropriate qualifications to fly the Beech 1900D

aircraft as per the KCAA requirements.

4. The airspeed degraded to below the VMCA.

5. The procedures stipulated in the AFM on one engine inoperative approach

and landing were not fully complied with.

6. The VREF airspeed was not maintained during the final approach to land.

7. The aircraft bank angle was not stabilized during the final approach to

landing.

8. The operative engine power setting was increase in the last seconds of the

flight causing an inadvertent left yaw.

9. The recommended 5° bank angle towards the operative engine was not

maintained during the one engine inoperative flight and especially during

the final approach to landing.

10. The aircraft performance was adversely affected during the final

approach to land because the appropriate bank angle was no maintained

towards the operative engine and the airspeed had degraded below VMCA.

11. The actual VMCA was higher than the published VMCA during the final

moments of the flight.

12. Actions by the pilots to regain control of the aircraft were fruitless

because of the close proximity to the ground

13. There was no evidence that that the pilots had undergone relevant

proficiency checks twice a year as required by the regulations.

14. There was no evidence that an aircraft operating manual for Beech

1900D had been developed by the operator as required by the regulations.

15. There were no annual inspection reports for the FDR and CVR among

the records provided by KCAA.

3.2. Probable Cause

The investigation determined the probable cause of the accident as loss of aircraft

control at low altitude occasioned by operation of the aircraft below VMCA during

one engine inoperative approach. Other significant contributory factors to this

accident include: Inadequate pilot training on single engine operation and VMCA;

inappropriate handling technique during one engine inoperative flight; inability of

the pilot to monitor the degrading airspeed.

4. SAFETY RECOMMENDATIONS

1. KCAA to ensure that pilot proficiency tests are conducted by operators and

the results of such tests are sent to the Authority during application for

license renewal.

2. KCAA to consider putting up a requirement for operators to develop one

engine inoperative checklist as a memory aid for multi-engine pilots during

emergency loss of engine situations.

3. KCAA to ensure that operators include VMCA demonstration flights tests in

their training curriculum.

4. KCAA should ensure that operators and flight crew maintain identical set

of documents in their records held by the Authority and those in their

respective premises.

5. KCAA to ensure that all FDR’s and CVR’s are inspected annually and

inspection reports are sent to the Authority on annual basis.

6. KCAA to ensure that operator’s pilot checklist includes provisions for

functional tests of CVR’s prior to the first flight of the day.

APPENDICES

Appendix I - FDR Plots

Appendix II – Wilson Airport Chart

Appendix III - ATC Tape Transcript

Appendix IV – Radar Data

Appendix V - Photographs

Radar Information

Time Altitude Speed Distance Bearing

5:15:00 68 226 4.2 316

5:15:06 67 226 3.9 317

5:15:12 64 224 3.5 316

5:15:18 61 222 2.9 314

5:15:24 61 223 2.6 312

5:15:30 61 223 2.2 310

5:15:36 61 213 2 310

5:15:42 61 208 1.7 309

5:15:48 61 199 1.3 308

5:15:54 59 179 1.1 309

5:16:00 58 168 0.9 309

5:16:06 57 162 0.7 308

5:16:12 56 156 0.6 306

5:16:18 55 143 0.3 297

5:16:24 55 139 0.1 252

5:16:30 55 112 0.2 0

5:16:36 55 112 0.2 0

5:16:42 55 112 0.2 0