Final Report Nr.1/2006

Final Report Of The Serious Incident With ,,air Baltic’’airlines  Aircraft Fokker-50, Yl-bas, On 25 November 2005 At "Riga" International Airport

In accordance with Annex 13 of the Convention of Chicago as well as the Directive 94/56/EC of 21 November 1994 establishing the fundamental principles governing the investigation of civil aviation accidents and incidents of the Council of the European Union, the purpose of an investigation conducted under the responsibility of the Latvian Accident and incident investigation division is not to apportion blame or liability. Aircraft Accident and Incident Investigation Bureau is functionally   independent of all aviation authorities of the Republic of Latvia. The task of the Investigation Bureau is to investigate aviation accidents, serious incidents as well if necessary for enhancing flight safety incidents. The objective of investigation is to increase air safety and to prevent the recurrence of aviation accidents and incidents.


58 Brivibas Str., Riga
LV-1011, Latvia
Phone. 7288140
Fax.     7283339

Director of Aircraft Accident and Incident Investigation Bureau

Ivars Alfreds Gaveika

Final Report Nr.1/2006

Report On The Serious Aviation Incident To The Netherlands Manufactured Aircraft Fokker – 50 Of ,,air Baltic” Airlines Yl-bas On November 25, 2005


General Information Of The Serious Incident

The Investigation



1. Factual information

1.1. History of the flight

1.2. Injuries to persons

1.3. Damage to aircraft

1.4. Other damage

1.5. Personnel Information

1.6. Aircraft information

1.7. Meteorological information

1.8. Aids to Navigation

1.9. Communications

1.10. Aerodrome information

1.11. Flight recorders

1.12. Wreckage and impact information

1.13. Medical and pathological information

1.14. Fire

1.15. Survival aspects

1.16. Tests and research

1.17. Organisational and management information

1.18. Additional information

1.19. Useful or effective investigation techniques

 2. Analysis

 3. Conclusions

 4. Safety Recomendations


1. Radio communication records -  Air Traffic Control Centre of the Republic of Latvia

2. Aircraft Flight Data transcription.

3. Latvian Environment, Geology and Meteorology Agency information about actual and forecast  an appreciation of the weather.

4. Captain and Co-pilot Flight Safety Reports of ,,Air Baltic” Airlines

5. Flight plans.

6. Loadsheet of aircraft Fokker – 50 ,,YL-BAS”. 

7. ,,Air Baltic” Airlines maintenance personal Explanatory notes.

8. Aircraft Captain Airline Transport Pilot Licence  &  Training Certificate copies. 

9. Aircraft Co-pilot Training Certificate copy. 

General Information Of The Serious Incident

Unless stated otherwise all times in this report are UTC time

Registered Owner of aircraft -           „Air Baltic” Airlines

Operator:                                             ,,Air Baltic” Airlines

 Aircraft Type                         -            F27 Mk 050

 Manufacturer   -           Fokker Aircraft B.V. the Netherlands

 Nationality:                                         Latvia

 Registration                            -            YL-BAS

 Manufacturer’s Serial number-           20162

 Year of manufacture                -           1989

 Place of Serious Incident        -           International  Airport  ”Riga”

 Date and Time:                        -           25 November 2005 at 05.43 UTC      

The Investigation

The notification on fax message form about ,,Air Baltic Corporation” airlines aircraft Fokker -50

YL- BAS Serious Aviation Incident was notified to the Aviation Accidents & Incidents Investigation Bureau (AAIB) from the Aeronautical Rescue Co-ordination Centre (ARCC) on November 25,  2005 at 08.14 local time.

Following investigators left for investigation to ,,Riga” International Airport

Mr I. A. Gaveika (Investigator in Charge)

Mr I. Zorgenfreijs (Senior Investigator)

Having arrived in ,,Riga” International Airport it was stated that, crew with aircraft F-50

YL –BAS had already left for passengers to Helsinki in order to continue return flight to Vilnius.   

Investigation team came to airline ,,Air Baltic Corporation” airlines office for receiving all documentation and materials necessary for beginning investigation these Serious Aviation Incident. 


 Having performed flight on route Vilnius - Helsinki at FL230, reaching route navigation point ,,ILSGO,” appeared light turbulence. Captain required FL250. Crossing FL240 started aircraft cockpit depressuarization emergency sound and light (MW) alarm system warning about altitude increasing (,,Cab.Alt”) in the aircraft cockpit.. Crew recognized highcabin altitude indication in the aircraft cockpit between 10 000 to 20 000 feet. Crew immediately used aircraft oxygen masks.

Having notified ATC traffic controller about depressuarization problem crew began emergency landing procedures. After providing all necessary information to ATC traffic controller was allowed to perform landing to ,,Riga.” International Airport (RIX). Landing procedures have performed without remarks. Passengers have not claims.

 1. Factual information

 1.1. History of the flight

- Flight number – BTI321;

- Departure point- Vilnius International Airport (VNO);

- Departure time – 25 November 2005., 04. 50 (UTC);

- Landing point – ,,Riga” International Airport;

- Landing runway-Rwy18 (heading 180);

- Landing time – 05.43 (UTC);

- Fuel weight before flight – 1957 kg;

- Fuel weight after landing – 1410 kg; 

- Weather condition at the moment of landing:

- visibility -more than 10 000 m

- wind direction-130°  

- wind velocity-12 kts

1.2. Injuries to persons


1.3. Damage to aircraft


1.4. Other damage

 There was no damage

1.5. Personnel information

Crew qualification according to determinated requirements.

The Captain, age 46, graduated Aktjubinsk Aviation University at 1991.

Pilot qualification according to determinated requirements:

Total flying experience-10370 hours;

Flying experience as captain (PIC) -1037 hours.;

Flying experience on aircraft type - F-50 PIC-757 hours;

Flying hours in previous day - 06.15;

Flaying hours in incident day - 00.53;

Previous rest period-17 hours 45min.;

Last examination of pilot qualification – August 24, 2005;

First officer, age 48, graduated Zaporozhje pilot instructors college at 1989;

Total flying experience -3600 hours;

Flying experience on aircraft type F-50-527 hours;

Flying hours in previous day -06.15 hours;

Flying time on day of incident - 00.53 hours.

1.6. Aircraft information

Aircraft type – F27 Mk 050;

Registration -  YL-BAS;

Owner of aircraft –„Air Baltic Corporation”  Airlines;

Total aircraft flying hours-32391 hours;

Manufacturer-Fokker Aircraft B.V. , the Netherlands;

Manufacturer’s serial No.-20162;

Take off Weight- 18181kg;

Landing Weight– 17684kg;

Fuel weight before flight – 1957 kg;

Fuel weight after landing – 1410 kg; 

Fuel type – Jet A;

Engines – PW 125B;

Serial No. -LH-124343; RH-125005;


The left (number1) engine had accumulated - 29823 hors;

The right (number2) engine had accumulated - 28435 hours;

Actual aircraft Balance Check within determined - 69,5;

Last maintenance check–October 25, 2005.

1.7. Meteorological information

International Airport „RIGA”

TAF EVRA 250500Z 250615 15014KT 6000 SCT005 OVC012 PROB40 TEMPO

0615 1000 SN BR OVC003=

TAF EVRA 250500Z250615 15014KT6000 SCT005 OVC012 PROB40 TEMPO 09182000 SN BR BKN007 OVC015=

TAF EVRA 250800Z 250918 14014KT 9000 SCT010 OVC020 PROB40 TEMPO

0918 2000 SN BR BKN007 OVC015

METAR EVRA 250420Z 15013KT 9999 OVC016 M01/M03 Q1007 I8190060 NOSIG

METAR EVRA 250450Z 15013KT 9999 OVC016 M01/M03 Q1007 18190060 NOSIG

METAR EVRA 250520Z 15013KT 9999 OVC016 M01/M03 Q1007 18190060 NOSIG

METAR EVRA 250550Z 13012KT 9999 –SN OVC016 M02/03 Q106 18190060 NOSIG

Airport Vilnius

TAF EYVI 250200Z 25312 15016KT 2500 SN BLSN BKN006 OVC050 PROB40 TEMPO 0408 17010KT 0800 –SN FZFG VV002=

TAF EYVI 250500Z 250615 14012KT 3000 SN BR BKN006 OVC030 TEMPO0615 17018KT 1000+SN BLSN VV003=

METAR EYVI 250450Z 15012KT 4000 BR OVC010 M02/M02 Q1006 204/0295


METAR EYI 250520Z 14012KT 7000 OVC011 M02/M02 Q1006 204/0295 NOSIG

1.8. Aids to Navigation


1.9. Communications

Phraseology of ATC  traffic controllers have conformed with „Procedures for Air Navigation Services - Air Traffic Management”- 14th Edition, 2001. (ICAO Doc. 4444)   Chapter 7 –Aerodrome and meteorological information, Items 7. 3. 1. 2. and

 Radio communication with ,,Approach Riga” (Riga APP) frequency  127,3 MHz, „Tower ,Riga” (Riga TWR) - frequency 118,1 MHz and Control Center Riga (Riga ACC)- frequency 133,2 MHz (See. Appendix 1).

1.10. Aerodrome information

The runway in use was Runway 18. Its physical characteristics are:

Dimensions – 2550x45 metres

Runway 18. slope-0,05%

TORA – 2550m;

TODA – 2950m;

ASDA – 2550m;

LDA - 2550m.

 Surface –asphalt concrete. Remark – composite structure


Approach and runway lighting:

-APSH LGT type LEN INST –ALSF -1 (CAT) 900 m distance 30 m;

-THR LGT colour WBAR –green;

-VASIS(MEHT) PAPI –left GP 3,00°   (62,7 feets);


Runway centerline lighting system – not installed.

Lighting location and colour on runway sides – white lighting located of length

2550 m, with interval 60 m, latest 600 m yellow.

Lighting and lighting colour on runway end (WBAR)-red.

Braking koeficient - 0,5

1.11. Flight data records

 Aircraft  Flight recorders data transcribed  (see. Appendix 2).

1.12. Wreckage and impact information

 Not damage

1.13. Medical and pathological information

Not relevant to this incident

1.14. Fire

There was no fire

1.15. Survival aspects

 Not necessity to survey

1.16. Tests and research

 Not necessary

1.17. Organisational and management information


1.18. Additional information


1.19. Useful or effective investigation techniques

Not apply

2. Analysis

Instant Aviation serious incident not entailed with aircraft system and equipment deficiency or failure. Aircraft systems and equipment have operated normally within determined parameters.       

Having performed the aircraft YL-BAS preflight maintenance check in the Vilnius International airport, maintenance personal after finishing aircraft cockpit heating operation and having closed   ground air conditioning panel cover at the bottom of aircraft fuselage right side, not fixed the latch of cover in position „closed” according to operation instruction, but leaved it in position „open”, as a result the aircraft ground air conditioning panel cover kept not pressure proof before takeoff.. Aircraft captain, having performed preflight inspection (PFI), did’nt detect open position of ground air conditioning panel cover and declared that aircraft comply determined technical requirements and completely ready for flight fixing it in the aircraft logbook.

After takeoff from Vilnius International airport, climbing and decreasing atmospheric pressure outside of aircraft, through not locked ground air conditioning manhole began pressure decreasing in the aircraft cockpit.   Due to light turbulence at FL230 crew required ATC for FL250. Performing climbing at FL240 started aircraft cockpit depressuarization emergency sound and light alarm system. Crew recognized high cabin altitude indication in the aircraft cockpit (between 10 000 to 20 000 feet).

Captain made a decision about aircraft emergency landing to the nearest airport i.e. ,,Riga International Airport.”

3. Conclusions

 Main cause of pressure decreasing in the aircraft cockpit during flight primarily was maintenance quality and control having performed aircraft cockpit heating operation at the Vilnius  International airport,   preparing aircraft to flight.  After finishing aircraft cockpit heating operation using aircraft ground air conditioning system, disconnecting of heated air feed-tube the latch of fuselage air conditioning cover had not fixed in position „closed” , but left in position „open”, as a result of   these action was created conditions for air leaking from aircraft cockpit and depressuarization during flight climbing at certain flight altitude.

Secondly aircraft captain, having performed aircraft preflight inspection didn’t detect open position of ground air conditioning panel cover and made a decision for flying out.

 Uncomfortable to requirements of flight safety Aircraft maintenance quality could be qualified as unsatisfactory experience and self-supervision skills of personal as well as  fatigue at the end of night shift.             

Aircraft captain, having performed aircraft preflight inspection before flight (PFI), hadn’t done aircraft inspection according to requirements of Manual (OM-Part B), Item   (Pre-flight Inspection), subpoint 3.

Having investigated aviation incidents the Aviation Accidents & Incidents Investigation Bureau (AAIB) periodically has causes of non- compliance of performed maintenance and aircraft preflight inspection to standard procedures determined in normative and technical documentation, regardless of in normative and technical documentation explicitly determined operations and it capacity as well as given responsible authorities and persons. These problems have not technical, but human factor related in aviation maintenance. It can apply in full to listed   Serious aviation incident and origin cause in ,,Air Baltic” Airlines. Whilst it is the individual who caries out the unsafe actions and its creates flight safety problems with consequent flight safety risks, accountable authorities must develop up a flight safety policy and perform concrete prevention actions for reducing of flight safety and, therefore the risk of recurrence similar maintenance related incidents in further operation.  

 4. Flight Safety Recomendations

 Necessary to implement following recommendations:

 4.1. Recomendation 2005-11

 Airline „Air Baltic” should perform analysis about effect of human factor to aircraft maintenance quality. On basis of analysis state the reason whether mishaps and violations have regulatory, managerial or financial character. Perform additional training maintenance personal   for development self-supervision skills and  strengthening   practical operations.  

 4.2. Recomendation 2005–12

 „Air Baltic” Airlines should perform analysis of aircraft preflight inspection procedures for purpose to develop preflight inspection operations and if necessary perform organization in frame of training process additional theoretical and practical studies with regard to preflight inspection effect on flight safety and risk reducing.  

 4.3. Recomendation 2005-13

 „Air Baltic” Airlines accountable services, about flight safety and quality assurance, in relevance with Serious aviation incident, that carried out to using emergency procedures during flight and forced landing at the ,,Riga” International airport, should perform analysis of technical maintenance programs  for evaluating its efficiency and if necessary perform corrective actions for improving flight safety and reducing potential risks.  

April 24, 2006

Director of Aircraft Accident and Incident Investigation Bureau

Ivars Alfreds Gaveika