Nostrum CRJ9 at San Sebastian on Oct 25th 2013, damaged gear on +2.988G landing, flew next sector

Last Update: May 18, 2016 / 14:47:21 GMT/Zulu time

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Incident Facts

Date of incident
Oct 25, 2013

Classification
Accident

Airline
Air Nostrum

Flight number
YW-8322

Departure
Madrid, Spain

Destination
San Sebastian, Spain

Aircraft Registration
EC-JYA

Aircraft Type
Canadair CL-600 Regional Jet CRJ-705

ICAO Type Designator
CRJ9

An Air Nostrum Canadair CRJ-900 on behalf of Iberia, registration EC-JYA performing flight YW-8322/IB-8322 from Madrid,SP to San Sebastian,SP (Spain) with 65 passengers and 6 crew, performed a visual approach to San Sebastian's runway 04. Following safe touch down the aircraft slowed down more quickly than anticipated, the aircraft taxied to the apron, where passengers disembarked safely.

The realization of the rather abrupt deceleration prompted the crew to perform a thorough visual inspection of the landing gear of their jet, however, no damage was detected. The crew therefore decided to continue their schedule and to return to Madrid as flight YW-8325/IB-8325 where the aircraft landed safely.

Spain's CIAIAC reported that the crew informed maintenance at Madrid about the occurrence, an inspection by maintenance revealed damage to the landing gear that required grounding of the aircraft. Closer examination revealed the aircraft may have experienced a hard landing which caused damage to the structure of the landing gear, the structures needed to be replaced. Although reporting structural damage to the landing gear the CIAIAC rated the damage "minor" but opened an investigation into the occurrence.

On May 18th 2016 Spain's CIAIAC released their final report into the occurrence, still rated an incident, concluding the probable cause of the occurrence was:

The incident was caused by the performance of a non-stabilized approach maneuver with a high sink rate in the final segment that resulted in the aircraft making a hard landing.

The following contributed to the incident:

- The presence of a southerly wind (tailwind) during the approach, which probably sped up the approach and forced the crew to increase the sink rate.

- By not holding a briefing on the maneuver they were going to execute, the crew did not prepare adequately for the approach.

- The crew did not do a go around, as required by the Operations Manual for a nonstabilized approach.

- The first officer’s lack of experience at that airfield and on that aircraft in particular.

The CIAIAC reported that a cloud mass was moving in from Hondarribia mountains also bringing in stormy weather. The aircraft was cleared to maintain MSA and join a VOR runway 22 instrument approach. However, as the crew had the airport and runway 04 in sight as well as the reported winds (from 10 to 20 degrees at 8 to 9 knots) favoured runway 04 indicating a head wind component, the crew decided to perform a visual approach to runway 04 although their FMS at that point still showed a substantial tailwind component of 16 knots. They were too high for that approach however and therefore flew a descending full circle, upon completing the 360 the crew put the aircraft into full landing configuration.

The CIAIAC then continued factual narration of the landing:

As per his statement, the pilot flying (first officer) varied the aircraft’s flight path slightly to the left to avoid some hills along the approach route and thus avoid activating the EGPWS. He did not follow the PAPI reference reading, since the glide slope it required (3.9º) was beyond the stabilization parameters shown by the NOTAM in the OFP. As a result the landing was conducted with all four PAPI lights showing red.

According to the crew, the approach was stabilized and made extensive use of standard callouts. The captain was constantly monitoring the wind, given the difference between the cockpit readout and the wind information provided by ATC, and on several occasions, including during the final approach, requested updated wind data from the control tower.

According to the crew’s accounts, the reference speed they used for the landing was the reduced VREF, specified in the special procedure for operating at EAS. During the flare, starting at a height above the runway of 50 ft, the aircraft moved sharply downward, causing the two main gear legs to touch down hard. The stick shaker did not activate (according to the crew they had a 13-kt wind gust), neither did the sink rate. The captain had asked the first officer to raise their pitch angle, which reached 7º, but the first officer did not want to raise the nose any further, fearing a tail strike.

They did not consider increasing thrust since the engines were at idle and they did not think they would respond in time.

After the landing, despite not having any specific references to check if they had exceeded the established hard landing limits but due to the firm touchdown, the crew decided to do a thorough walkaround inspection of the aircraft. They checked the wheels, tires and main landing gear leg assemblies and saw nothing out of the ordinary.

They also reviewed the synoptic hydraulic diagram shown on the EICAS display and noticed no damage or leaks. The amount of hydraulic fluid in the tanks was within normal limits (87-91%) and the fluid temperature was normal. In light of this information, the crew decided to make the return flight to Madrid-Barajas (LEMD) and notify its maintenance personnel there.

After the return flight another walk around again did not detect any damage to tyres, wheels, gear of hydraulic systems. Maintenance detected damage to the left main landing leg, "the front panels (above the wing) were found slightly bent".

The captain had noted in the tech log a hard landing with a rate of descent between 400 and 600fpm at touchdown, a review of the flight data recorder revealed however that the vertical rate was in excess of 600 fpm requiring a hard landing inspection.

A subsequent maintenance inspection identified "that the orifice support tube for the left gear had collapsed, the anti-rotation sleeve on the right gear was broken and the number 1 wheel was bent. In addition, all of the data downloaded from the DFDR were sent to the Engineering Department at Bombardier (the aircraft manufacturer) for analysis and determination of additional measures. After analyzing the DFDR data and comparing it against the damage reported, the manufacturer concluded that the shock struts in both legs had been subjected to loads above their design limits. They thus recommended disassembling the shock strut, the shimmy dampers and side stay assemblies, and disassembling and inspecting the four wheels on both main gear legs."

The CIAIAC summarized engineering analysis: "The operator informed the manufacturer that a review of the DFDR data showed an initial impact with a maximum vertical load factor (Nz) of 2.988 g’s. This was followed by a bounce with the spoilers deployed that resulted in a second impact with Nz equal to 2.14 g’s. The nose gear did not contact the ground for an additional five seconds after the second impact, with the pitch angle gradually decreasing until contact was made. Before the initial landing, the aircraft was in a wings-level attitude. The descent rate during the landing was probably between 13 and 15 ft/s (780-900 fpm), higher than the limit load (corresponding to 12 ft/s). The conclusion was that both main gear legs withstood forces in excess of the maximum load."

The CIAIAC stated, that the company did not permit approaches to runway 04 in instrument meteorological conditions.

The CIAIAC analysed: "The operator requires its crews to have an approach briefing, as specified in the FCOM and in the special operating procedure. The briefing must be conducted before starting the descent and specify the use of said special procedure, the conditions required to continue the approach and the go-around procedure. Although the CVR recording was not available, it is likely that the crew held a briefing on the approach to runway 22, since they had been cleared for this maneuver, which was the usual approach. The fact that they had to do a 360º turn to lose some of their excess altitude indicates that theapproach maneuver to runway 04 was not expected. It thus seems unlikely that they did the briefing after deciding to make a visual approach to said runway."

The CIAIAC analysed: "During the approach, starting at about 2000 ft, the winds aloft recorded in the aircraft indicated a tailwind (180-190º) at an average speed of 27 kt. As a result of this tailwind, the ground speed (GS) was higher than the IAS (CAS). Below a QNH-corrected altitude of 426 ft (QNH 1019), the GS started to drop below the IAS, as the wind shifted from a tailwind to a headwind, a wind condition on the runway in use that was reported by the controller in the tower." and stated: "Mount Jaizquibel is located north of the airport. Due to this mountain’s location and to the characteristics of the area in the approaches to runway 04/22, the airport is prone to turbulence and shifting winds, meaning it was possible for there to exist turbulence to leeward due to the geography of the area, which could have affected the prevailing wind conditions in the final part of the approach."

The CIAIAC analysed: "According to the DFDR data, the crew executed this procedure with 134 kts at 50 ft and 125 kt at touchdown, though at a high sink rate. The crew varied the aircraft’s pitch angle from 3 to 5º at 11 ft, but it rose to 7º at the instant of landing. The aircraft’s speed did not drop below the stall speed (108 kts) for that configuration, meaning the aircraft did not fall to the ground, but it did impact the runway with considerable energy. During the flare and the initial contact, the values of N1 exhibited values that differed from approach idle (35% versus 26%). This indicates that the levers were not in the idle position at first contact. Putting back the levers to such position after the first impact caused the ground lift dumping (GLD) system to deploy, resulting in a second hard landing. In keeping with the instructions in the FCOM, the crew should have gone around after bouncing or when they realized they had to apply thrust to make the landing."

Metars:
LESO 251500Z 35004KT 310V030 CAVOK 19/17 Q1009
LESO 251430Z 01004KT 320V040 CAVOK 20/17 Q1009
Incident Facts

Date of incident
Oct 25, 2013

Classification
Accident

Airline
Air Nostrum

Flight number
YW-8322

Departure
Madrid, Spain

Destination
San Sebastian, Spain

Aircraft Registration
EC-JYA

Aircraft Type
Canadair CL-600 Regional Jet CRJ-705

ICAO Type Designator
CRJ9

This article is published under license from Avherald.com. © of text by Avherald.com.
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