Mount Cook Airline

Safety Investigations & Education in an Airline

Nathan McGraw

05 June 2010

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Overview

Mount Cook Airline - our approach to safety

Tail icing investigation

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Who are we?

Part of the Air NZ Group

Wholly owned subsidiary

Independent AOC

11 x ATR 72-500

2,300 sectors per month

10 scheduled destinations

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Our Approach to Safety

We don’t rank safety: Safety is critical

Use SMS principals (formal SMS in development)

Proactive approach (don’t wait for an incident)

Investigate events that go well

Safety education is essential

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Our Approach to Safety

Operational Safety (not Flight Safety or OSH)

Previously an ‘investigation office’ only

Op Safety team Two pilots (F/Os) Two cabin crewmembers

All current line crewmembers (minimum 50% line flying)

Safety focus (no fingers in other pies)

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Our Approach to Safety

Cabin crew are an essential part of the team

Many investigations have a cabin crew aspect

Separate area of expertise

Non-technical approach

Non-management contact for line cabin crewmembers

Line cabin crewmembers have a voice (better buy-in)

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Our Approach to Safety

Safety Advisors, not Investigators

Both pilots have training & examining backgrounds

Both pilots are FOs and have been Captains previously

Qualified military test pilot and instructor

Trained investigators

RABQSA accredited auditor

HF training (USC, ATSB)

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Our Approach to Safety

Essential Qualities of a Safety Advisor

Integrity

Objectivity

Moral courage

Respected by crewmembers and management

High personal standards (sets an example)

Infectious attitude towards safety (generative approach)

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Our Approach to Safety

Ratio of work30% monitoring (processing data, reports)

20% investigations

60% safety liaison & education

____

110% (we work very hard)

Focus on education improves credibility and buy-in

credibility = report quality & quantity

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Safety Reports

Investigation

Positive Education

Trust / Buy-inMaintaining

Credibility

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Our Approach to Safety

Safety Reports – our morning newspaper

All about trust (hard to earn, shattered in an instant)

Absolute avoidance of punitive action

De-identification, even when not requested

Responsible to the regulator for notification; but Greater responsibility to our fellow crewmembers

Integrity (we do what we say we’ll do)

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Our Approach to Safety

Safety Investigations - how can we do this better?

Evidence-based approach

Huge HF emphasis

Lots of tests for ‘reasonableness’

Substitution tests to identify systemic factors

Absolute avoidance of punitive content

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Our Approach to Safety

Safety Education – Give people the tools to be safe!

Op Safety Report: weekly report to management

Safety Snapshot: monthly occurrence bulletin

Aoraki Safety: biannual magazine

Op Safety website: library, links, resources

Classroom: HF module during annual CRM courses

All positive material – no preachy statements

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Our Approach to Safety

Traditional Safety Office Get summonsed when you’ve had an incident Only produces investigation reports Punishment for naughty pilots

Message: Safety Office is a negative place

Our Op Safety office Positive place (even during investigations) Churns out positive safety material (learning emphasis) Try to make safety interesting, enjoyable, and accessible

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Recent Investigations

TCAS TA at Queenstown

GNSS Database Validity

Engine failure after takeoff

DG fumes in-flight

Severe turbulence (yes Peter, it’s coming)

Tail icing events

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Tail Icing Events

Important

Not suggesting that the ATR is unsafe in icing conditions

ATR has produced comprehensive & detailed information for operators and pilots

ATR icing procedures are robust and appropriate

Investigation is applicable to all aircraft types

Only significant points covered in this presentation

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Tail Icing Events

NZ Climate

Polar Maritime (cold, moist flow)

Airframe icing at altitude (especially for turboprops)

NZ pilots generally knowledgeable about airframe icing

Icing all year – both events happened in late summer

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Tail Icing Events

First Event

Freezing rain in climb between FL160 and FL170 (Marlborough Sounds)

Significant reduction in rate-of-climb to <200 fpm

Ice detection system alert

Immediate cruise descent to FL150

Air was 5 °C warmer and all visible ice melted quickly

Flight continued at FL150 with no visible ice accretion

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Tail Icing Events

First Event

After 15 minutes at FL150, loud bang and severe vibration from tail area

Vibration lasted for over 30 seconds but then ceased

Pilots disconnected AP and checked for controllability – all normal

Experienced crew – never encountered vibrations so strong

Suspected ice but diverted to Palmerston North due severity of vibration

Thorough maintenance inspection – no defects or abnormalities

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Tail Icing Events

Second Event

Ice accretion earlier in flight

“Significant icing remained on the IEP”

Cruised in VMC

IMC on descent but VMC at 7,000 ft

All visible ice melted by 4,000 ft

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Tail Icing Events

Second Event

No visible ice and +11 °C on the ground

All ice protection systems turned off (as per SOP)

Pilots planned for and briefed a non-icing landing

‘Fish tailing’ on final approach

Unstable in pitch and yaw – difficult to stabilise and trim

Landed uneventfully

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Tail Icing Events

Second Event

After disembarking, pilots noted significant ice on stabiliser

Ice on pneumatic boots (protected section),

Estimated 150mm forward of leading edge

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Tail Icing Events

Analysis

Considered defects with flight controls, trims, autopilot, ice protection

Review of maintenance records – no defects or discrepancies

Functional test of pneumatic boots – no defects

Tail icing most likely contributing factor

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Tail Icing Events

NASA Tail Icing Research (early 1990s)

Tail icing historically poorly understood

Icing accidents between 1950 & 1980 often misdiagnosed as wing stalls

Tail surfaces accrete ice earlier and faster than wings (sharper leading edge)

Propeller aircraft are more susceptible (particularly turboprops)

Possible to have ice on stabiliser with no other ice on airframe

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Tail Icing Events

Stabiliser on turboprop aircraft often sits in prop wash

Higher velocity = lower temperature

Prop wash air can be up to 5 °C cooler than ambient

Tail can be in icing conditions, even if the rest of the aircraft isn’t!

Prop wash at higher angles-of-attack (for illustrative purposes only).

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Tail Icing Events

Design features which support tail icing (NASA)

Un-powered and aerodynamically balanced elevators Pnuematic de-icing boots in lieu of heated leading edges Horizontal stabilisers with sharp leading edges Large flap deflections (big change of relative airflow over tail)

These features are applicable to a lot of turboprops

Tail ice can be 3 – 6 times thicker than on the wings

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Tail Icing Events

Findings – First Event

No maintenance defects or anomalies

Loud bang was likely tail ice breaking free in warmer air at FL150

Vibration was likely airflow disruption over elevator due to ice breaking free unevenly

Gave the crew a real fright – a very unusual icing event

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Tail Icing Events

Findings – Second Event

No maintenance defects or anomalies

Pilots followed SOPs exactly (passes substitution test)

Residual ice on the tail was very unusual

Aerodynamic instability on approach likely caused by tail icing

Pilots reported symptoms similar to an impending tailplane stall

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Tail Icing Events

Symptoms of impending tailplane stalls (NASA)

Lightening of controls (particularly forward motion)

Difficulty trimming

Onset of pilot-induced oscillations due to change of control balance

Control buffeting (but not the airframe)

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Tail Icing Events

Severe Icing QRH Checklist

Includes significant protections against tailplane stall (reduced flap landing)

Pilots used it only when in defined severe icing

Once clear of severe icing, pilots would resume normal ops and land with full flap (breaking the checklist)

Tail icing is possible without being in defined severe icing

Recommended that checklist be used whenever tail icing is suspected (regardless of whether icing was severe or not)

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Tail Icing Events

Recommendations

Training module for tail icing

Icing exercise in simulator that results in a reduced flap landing

Use severe icing checklist (including reduced flap landing) if tail icing is suspected, even if airframe is visibly clear of all ice

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Tail Icing Events

Results

Good support from ATR during investigation

Great company support, particularly Flight Ops and Training

Enthusiastic uptake from training team

Pilots now routinely report landing with reduced flaps after significant ice encounters

Investigation resulted in positive training and tangible results

Thanks!