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B733, vicinity Chambery France, 2010

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Summary
On 7 February 2010, a Boeing 737-300 being operated by Jet2 on a scheduled passenger flight from Leeds/Bradford UK to Chambery France was making an ILS approach to runway 18 at destination in day IMC when a Mode 2 EGPWS ‘Terrain, Pull Up’ Warning occurred. A climb was immediately initiated to VMC on top and a second ILS approach was then made uneventfully. Despite extreme pitch during the early stages of the pull up climb, none if the 109 occupants, all secured for landing, were injured.
Event Details
When February 2010
Actual or Potential
Event Type
Controlled Flight Into Terrain (CFIT), Human Factors, Loss of Control
Day/Night Day
Flight Conditions IMC
Flight Details
Aircraft BOEING 737-300
Operator Jet2.com
Domicile United Kingdom
Type of Flight Public Transport (Passenger)
Origin Leeds Bradford
Actual Destination Chambéry
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Descent
ENR / APR
Location - Airport
Airport vicinity Chambéry
General
Tag(s) Approach not stabilised
CFIT
Tag(s) Into terrain,
No Visual Reference,
Vertical navigation error,
IFR flight plan
HF
Tag(s) Ineffective Monitoring,
Manual Handling,
Procedural non compliance,
Inappropriate crew response - skills deficiency
LOC
Tag(s) Aircraft Flight Path Control Error,
Extreme Pitch
Safety Net Mitigations
Malfunction of Relevant Safety Net No
TAWS Effective
Outcome
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation
Safety Recommendation(s)
Group(s) None Made
Investigation Type
Type Independent

Description

On 7 February 2010, a Boeing 737-300 being operated by Jet2 on a scheduled passenger flight from Leeds/Bradford UK to Chambery France was making an Instrument Landing System (ILS) approach to runway 18 at destination in day Instrument Meteorological Conditions (IMC) when a Mode 2 Terrain Avoidance and Warning System (TAWS) ‘Terrain, Pull Up’ Warning occurred. A climb was immediately initiated to Visual Meteorological Conditions (VMC) on top and a second ILS approach was then made uneventfully. Despite extreme pitch during the early stages of the pull up climb, none if the 109 occupants, all secured for landing, were injured.

Investigation

An Investigation was carried out by the UK AAIB. The Cockpit Voice Recorder (CVR) had been overwritten but useful Flight Data Recorder (FDR) data was recovered except for the recorded position which was derived from the FMS and therefore “susceptible to errors”. Download of the EGPWS computer provided useful information and the ATC radar recording allowed aircraft position to be determined accurately.

It was noted that in the light of a State Requirement for commanders of all commercial flights to receive special training from their company before they are allowed to fly to Chambery, Jet2 had designated the destination as a Category ‘C’ airfield and provided its crews with a special brief. The aircraft commander was found to have received this training four years earlier as a First Officer and although he had since complied with the annual recency requirements, had not received any further training when he was promoted to Captain.

It was established that the First Officer had been designated as PF because had the light northerly wind increased as forecast, it might have meant that a circling approach to Runway 36 would be required “for which the right hand seat pilot would have been better placed to maintain a clear view of the runway”. In fact, the wind remained light and the aircraft was cleared for a straight in ILS to Runway 18.

FDR data showed that the ILS LLZ had been captured normally with the AP engaged and that descent on the ILS had been commenced at a range of 11 nm20,372 m
20.372 km
66,837.27 ft
but with VS (Vertical Speed) selected rather than the ILS GS. This would have complied with Company SOPs had a circling approach followed the ILS but was contrary to SOP for a normal auto ILS approach, even at the steeper than normal GS angle at Chambery of 4.46° as this should be done with APP mode engaged. As VS mode was engaged, the aircraft was already about 850 ft259.08 m
below the ILS GS and began to descend at about 2200 fpm with the speed increasing slowly from 160 knots296.32 km/h
82.24 m/s
to 175 knots324.1 km/h
89.95 m/s
. At a range of 8.6 nm15,927.2 m
15.927 km
52,254.593 ft
from the runway, where the ILS track passes over a ridge of high ground, the terrain closure rate suddenly increased to over 6,000 fpm and when the terrain clearance reduced to 1125 feet342.9 m
, an EGPWS Mode 2 Hard ‘Pull Up’ Warning was activated. Almost simultaneously, the AP was disconnected and a climb commenced from a minimum recorded terrain clearance of 1,112 ft338.938 m
. It was noted that the limitations attributable to FDR data recording rates meant that it was not possible to determine if the climb had been initiated just before the EGPWS warning as reported by the crew.

During the subsequent climb, airspeed reduced from 175 knots324.1 km/h
89.95 m/s
to 110 knots203.72 km/h
56.54 m/s
during the approximately 40 seconds it took to climb from an altitude of 3500 feet1,066.8 m
to VMC at 6000 feet1,828.8 m
where the aircraft was levelled. The rate of climb averaged about 3,800 fpm and the recorded pitch attitude reached a maximum of +37° within 15 seconds of the climb commencing before then reducing to around 25° until approaching 6000 feet. No reference is made by the investigation to the weight of the aircraft during the climb and the corresponding stalling speeds.

The Final Report: AAIB Bulletin: 12/2010 EW/C2010/02/03 of the Investigation was published on 9 December 2010.

Further Reading