Rwanda CRJ9 at Entebbe and Kigali on Feb 4th 2018, engine damage by foreign object ingestion
Last Update: August 5, 2019 / 15:02:27 GMT/Zulu time
A post flight inspectio revealed significant damage to all 28 fan blades of the left hand engine (CF34), a metal bolt was found in the acoustic lining of the fan intake. The bolt did not belong to the occurrence aircraft.
On Aug 5th 2019 Rwanda's AAIID (Aviation Accident and Incident Investigation Department) released their final report releasing following findings:
3.1.1 After arrival of flight WB 465 at KGL on Febr. 4th 2018, impact damage to all fan blades of the left-hand engine was found, as well as minor punch-type damage to the left-hand outboard main gear tire.
3.1.2 The fan blade damage was caused by a bolt, that was found lodged in the acoustic liner of the fan intake.
3.1.3 The bolt causing the fan blade damage did not originate from the engine and thus has been ingested by it.
3.1.4 Most probably the bolt was picked up by the outboard wheel from the left-hand main gear during taxi-out at EBB and subsequently ingested by the left-hand engine during the take-off roll. This scenario however could not be demonstrated unambiguously.
3.1.5 The Airport Council International (ACI), the International Civil Aviation Organisation (ICAO) and the European Aviation Safety Agency (EASA) have issued comprehensive guidelines on Foreign Object Debris (FOD) prevention programmes.
3.1.6 The EASA guidelines on FOD prevention programmes will be incorporated in ICAO documentation by the end of 2020.
3.1.7 The newly developed EASA guidelines emphasise that the aerodrome FOD control programme should cover hazards involved with construction activities.
3.1.8 At the time of the incident extensive works on airside of EBB airport were in progress.
3.1.9 The Airport Authorities from KGL and EBB have not demonstrated their FOD control programmes nor documented rules on runway inspection requirements.
The AAIID analysed:
The fan blade damage, that was found after arrival of flight WB465 at KGL, was consistent with impact forces from the bolt that was found lodged in the acoustic liner of the fan intake. Since it was unambiguously demonstrated that this bolt did not originate from the engine or the aircraft itself, the bolt must have been ingested by the engine. However, even at high power settings such as during take-off, ingestion of a small object with a mass like that of the bolt concerned is not very likely for a Bombardier CRJ900 aircraft because of its relatively high positioned rear-mounted engines. It is therefore significant that, apart from the fan blade damage, also small punch-type damage to the tread of the left-hand outboard main gear tire was found that had not been detected before, see Appendix 1. This leads up to the most likely scenario whereby during taxi-out or on the runway the bolt was picked up by the left-hand outboard tire at low speed, subsequently came loose from the tire by centrifugal forces during the high speed part of the take-off run and then was ingested by the left-hand engine, running at take-off power.
The fan blade damage was found after arrival at KGL, whereas during the preflight inspections at the en route stations of flight WB465 no abnormalities were found. Besides the last runway inspection at KGL prior to the landing of flight WB 465 had shown no abnormalities.
The available landing distance for runway 28 at KGL is 3279 m, which is more than adequate for CRJ900 operations. This aspect, in combination with the prevailing company procedure to use idle reverse whenever possible, make it credible that no high reverse power settings during the landing roll of flight WB465 have been applied.
These circumstances indicate that ingestion of the bolt most probably has occurred during the take-off run at the last transit stop before reaching destination KGL, being Entebbe International Airport.
The reported extensive airside works in progress at EBB, that in itself create an additional FOD hazard, during the time of the incident add to the credibility of the scenario depicted above.
Nonetheless it must be stated clearly that, however likely, this scenario could not be demonstrated unambiguously due to lack of available data.
2.2 FOD prevention programme and runway inspection regime at Kigali and Entebbe
Both the Kigali and Entebbe Airport Authorities have been asked for their FOD prevention programme and runway inspection regime.
Kigali International Airport
From the KGL Airport Authorities two hand written runway inspections sheets were received, see Appendix 3. Since no specific runway inspections forms for KGL Airport are available, regular plain paper sheets from a notepad are used.
From the two sheets it can be concluded that frequent runway inspections at irregular intervals are being conducted. However, it could not be demonstrated that these inspections are based on a sound policy, laid down in the KGL Airport Operations Manual, nor that a FOD prevention programme is documented.
Entebbe International Airport
Despite several requests no information from the EBB Airport Authorities on their FOD prevention programme or runway inspection regime was received.
Based on the above it must be concluded that both KGL and EBB Airport Authorities should make an effort to develop and implement both a comprehensive FOD prevention programme and criteria for their runway inspection regime.
Such programme and criteria should be clearly documented in their respective Airport Operations Manuals and follow the directives and guidelines from ACI, ICAO and EASA as discussed in paragraph 1.16.2.
Especially the EASA documentation is of importance since it contains the latest standards and the most up to date information on this subject, that will be incorporated in the ICAO documentation framework by the end of 2020.
To this respect it is worthwhile to mention that EASA calls amongst others for:
− A continuous aerodrome FOD training programme, whereby employees from all stakeholders who perform activities on airside are made aware of FOD risks and adopt a ‘clean as you go‘ technique during their work.
− Specific FOD prevention procedures to be established and employed for each construction project. Thereby aerodrome pre-construction planning should include means for controlling and containing FOD generated by the construction in a pro-active way.
As stated in paragraph 1.10, extensive works on the manoeuvring area of EBB airport will be going on for the next years to come, imposing an increased risk for FOD related incidents. Pending implementation of a comprehensive FOD prevention programme as described above, the EBB Airport Authorities should therefore evaluate their current efforts to control FOD, both proactively and reactively, without delay. Based on this evaluation immediate action should be taken where needed.
This article is published under license from Avherald.com. © of text by Avherald.com.
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