History of the Flight
On 28 August 2015 a Boeing 737-300 Freighter, registered PK-BBY was being operated by PT. Cardig Air on a scheduled cargo flight from Sentani Airport (WAJJ) Jayapura to Wamena Airport1 (WAVV) Papua, Indonesia. At 1234 LT (0334 UTC2), the aircraft departed to Wamena and on board the aircraft were two pilots, and 14,610 kg of cargo. The Pilot in Command (PIC) acted as Pilot Flying (PF) while the Second in Command (SIC) who was under line training acted as Pilot Monitoring (PM). There was no reported or recorded aircraft system abnormality during the flight until the time of occurrence. At 0637 UTC, when the aircraft approaching PASS VALLEY, the Wamena Tower controller provided information that the runway in use was runway 15 and the wind was 150°/18 knots, QNH was 1,003 mbs and temperature was 23 °C. At 0639 UTC, the pilot reported position over PASS VALLEY, descended passing FL135. The Wamena Tower controller instructed the pilot to report position over JIWIKA. At 0645 UTC, the pilot reported position over JIWIKA and continued to final runway 15. At 0646 UTC, the pilot reported position on final runway 15 and Wamena Tower controller provided landing clearance with additional information of wind 150°/15 knots and QNH 1,003 mbs. At 0647 UTC, the aircraft touched down about 35 meter before the beginning runway 15 with vertical acceleration of 3.68 G. The left main landing gear collapsed and the left engine contacted to the runway surface. The aircraft stopped at about 1,500 meters from runway threshold. No one was injured on this occurrence.
Photo: MD
Damage to Aircraft
The aircraft substantially damaged, with the following condition:
The trunnion link of the left Main Landing Gear (MLG) assembly broken with the detail:
- the left MLG collapsed;
- the left landing gear access panel lower fairing damaged;
- the shock strut of the right MLG leaked and deflated.
The detail damages on the left Engine are as follow:
- Lower Fan cowling inner and outer damage;
- Lower Gearbox Casing scratch;
- Lower C-Duck thrust reverser inner damage;
- Lower C-Duct thrust reverser outer damage.
The detail damages on the left wing are as follow:
- Lower inboard trailing edge, aft and mid flap dent;
- Upper outboard flap track fairing dent;
- Inboard flap track fairing dent;
- Flap transmission assembly (ball screw) number 2 broken.
The collapsed left MLG
Significant Information from Flight Recorders
The significant information from the flight recorderswas as follows:
- 06:42:24 UTC, the pilot reported over JIWIKA on altitude 10,000 feet and the FDR recorded the altitude was on 10,568 feet. The engines were on idle.
- Between 06:42:24 until 06:43:44 UTC, the average rate of descend was approximately 2,000 feet per minute.
- 06:43:39 UTC, the flap selector was set to 40 position when the aircraft on altitude of 8,120 feet, and moved to 39.9° when the aircraft on altitude of 5,908 feet one minute 25 seconds later.
- 06:45:37 UTC, the EGPWS “CAUTION WINDSHEAR” active on altitude of 5,520 feet.
- 06:45:43 UTC, the engine power increased when the aircraft altitude was on 5,920 feet prior the EGPWS altitude call “ONE HUNDRED” heard.
- Started from 06:45:45 UTC, the FDR recorded the CAS increased from 148 knots to 154 knots followed by N1 decreased gradually from 73% to 38%. Three seconds before touched down, the rate of descend was constant on value 1,320 feet per minute followed by EGPWS warning “SINK RATE”.
- 06:45:52 UTC, the aircraft touched down on altitude 5,324 feet with recorded vertical acceleration up to 3.683 G.
Wreckage and Impact Information
The investigation found touchdown mark before the beginning of the pavement at about 35 meter from threshold runway 15.
Findings
According to factual information during the investigation, the Komite Nasional Keselamatan Transportasi determines the findings of the investigation are listed as follows:
1. The pilots held valid licenses and medical certificates.
2. The aircraft had a valid Certificate of Airworthiness (C of A) and Certificate of Registration (C of R), and was operated within the weight and balance envelope.
3. There were no reports of aircraft system abnormalities during the flight.
4. After passed JIWIKA on altitude 10,000 feet, the FDR recorded the engines were on idle, the average rate of descend was approximately 2,000 feet per minute.
5. At altitude approximately 8,000 feet, the flap selected to 40 position and moved to 39.9° one minute 25 seconds later.
6. The BMKG weather report was wind 150°/14-19 knots and the Wamena Tower controller reported to the pilot that the wind was 150°/15 knots. The information of gust wind, which indicated the possibility of windshear, was not reported to the pilot.
7. The EGPWS “CAUTION WINDSHEAR” active on altitude of 5,520 feet.
8. 06:45:43 UTC, the engine power increased when the aircraft altitude was on 5,920 feet prior the EGPWS altitude call “ONE HUNDRED” heard.
9. Started from 06:45:45 UTC, the FDR recorded the CAS increased from 148 knots to 154 knots followed by N1 decreased gradually from 73% to 38%. Three seconds before touched down, the rate of descend was constant on value 1,320 feet per minute followed by EGPWS warning “SINK RATE”.
10. The aircraft touched down at about 35 meters before the beginning runway 15 with the vertical acceleration recorded of 3.68 G.
11. The trunnion link of the left Main Landing Gear (MLG) assembly was found broken and the left main landing gear collapsed.
12. The FDR data contained of 107 flight hours consisted of 170 flight sectors which recorded five times of the vertical acceleration more than 2 G during landing at Wamena. The accumulation of such value of vertical acceleration might lead to landing gear strength degradation.
13. The Visual Approach Slope Indicator (VASI) of runway 15 was not operated after the runway extension.
14. The investigation found several touchdown marks on the pavement before the runway
15. Excessive rubber deposit was found on the surface of runway 15 at about 600 meter started from the runway threshold.
16. The absence of speed correction following the information of headwind of 15 knots and pilot crew briefing after activation of EGPWS caution windshear indicated that the pilot did not aware of the existing windshear, that might be contributed by the absence of gust wind information.
17. The large thrust reduction was not in accordance with the FCOM for windshear precaution and resulted in rapid descend.
18. The accident flight collapsed the landing gear, the FDR recorded the vertical acceleration was 3.683 G which was within the landing gear design limit. This indicated the degradation of landing gear strength.
Contributing Factor
The large thrust reduction during the windshear resulted in rapid descend and the aircraft touched down with 3.683 G then collapsed the landing gear that had strength degradation.
SAFETY RECOMMENDATIONS
Komite Nasional Keselamatan Transportasi (KNKT) considered the safety actions taken by the aircraft operator were relevant to improve safety. In addition, KNKT issued safety recommendations to address safety issues identified in this report.
The DGCA is responsible to ensure the implementation of the safety recommendations addressed to the operators.
PT. Cardig Air
To improve the windshear training to ensure appropriate pilot respond.
AirNav Indonesia
To improve the knowledge of air traffic controller related to the windshear to be able to provide useful information for flight operation.
Wamena Airport
- To develop an aerodrome maintenance programme
- To review and improve the runway inspection system
- To install VASI on the runway 15
DGCA
To ensure the establishment and maintenance of flight data analysis program as part of aircraft operator safety management system as stated in Civil Aviation Safety Regulation part 121.65 (c).
The preliminary accident report is here.
The final accident report is here.
For a full analysis of 737 Classic MLG failures on landing please follow this link. |
PK-BBY 737-300CF Gear collapse on landing
