Beech Aircraft Corp 200, VH-SWP

Investigation number

200105188

Occurrence date

24/10/2001

Location

22 km SSE Timber Creek, Aero.

Report release date

17/05/2002

Report status

Final

Investigation type

Occurrence Investigation

Investigation status

Completed

Aviation occurrence type

Incorrect configuration

Occurrence category

Incident

Highest injury level

None

Safety Action Significant Factors Analysis Summary

ATSB safety action

An Australian Transport Safety Bureau investigation into a
Beechcraft King Air 200 depressurisation incident, BO/199902928,
issued three recommendations on the subject of cabin alert aural
warning systems. The final report contained an additional
recommendation on the same subject. Recommendation R20000288
stated:

"The ATSB therefore recommends that CASA mandate the fitment of
aural warnings to operate in conjunction with the cabin altitude
alert warning systems on all Beechcraft Super King Air and other
applicable aircraft".

The Civil Aviation Safety Authority's response dated 2 February
2001 stated:

"The Civil Aviation Safety Authority accepts this recommendation
and will move to prepare a regulatory amendment to make it
mandatory for pressurised aircraft to have aural cabin altitude
alert warning systems. This amendment will follow the normal
regulatory development process which, in the first instance, will
lead to the circulation of a Discussion Paper. It is anticipated
that the paper will be released this month".

On the 2 February 2001, the Civil Aviation Safety Authority
(CASA) also issued a Draft Discussion Paper, DP 0102CS, to the
Australian aviation industry. The discussion paper was titled
Proposal for Aural Warning to Operate With Cabin Altitude Alert
Warning Systems. The discussion paper indicated that it was CASA's
preferred option to mandate requirements to modify the aircraft
concerned to install an audible warning to complement the existing
cabin altitude alert warning system. Responses to that paper were
to be provided to CASA by the 12 March 2001.

In April 2002 CASA issued a Notice of Proposed Rule Making
(NPRM) on the fitment of aural warnings to pressurised jet and
turboprop aircraft.

Investigation report BO/199902928 and the resultant
recommendations are available on the Australian Transport Safety
Bureau's Website, www.atsb.gov.au or from the Bureau on
request.

Local safety action

The operator conducted its own investigation into the issues
surrounding this incident. As a result of that investigation a
number of changes have been made to the company's operational
procedures. Those include a reassessment of company pilot training
and check-to-line requirements. Greater emphasis is now being
placed on adherence to checklists and occupational health and
safety issues relating to operations in hot and humid
environments.

The operator actively commenced correspondence with the Civil
Aviation Safety Authority to enable the re-installation of the
aural warning device kits. On the 15 January 2002, the Civil
Aviation Safety Authority responded to the request. The response
indicated that the operator could manufacture the system under the
operator's "current certificate of approval, as manufacture in the
course of aircraft maintenance". The CASA letter stated:

"Following a review of matters associated with the original
warning kits and their installation, it is considered there are a
number of matters you need to address to accomplish these
modifications, they are:

"1.The draft NPRM 0116CS "Proposal for Aural Warning to Operate
with Cabin Altitude Warning Systems" should be considered as much
as possible, to avoid having to make future design changes to the
system.

"2. A design advice on the modification should be submitted to
CASA by the CAR35 Authorised Person to save possible rework. It
would be expected that there would be a FAR 23.1309 hazard analysis
carried out on the system as part of the design justification.

"3. The design needs to incorporate a backup sensor for cabin
pressure in addition to the basic sensor fitted. Any failure in the
backup system should not disable the warning from the prime system
and vice versa. (ie FAR 23.1309 analysis)

"4. The design will call up parts and components by
specification for installation in the modification."

On the 20 February 2002, the operator advised the ATSB that it
had commissioned a CAR 35 engineer to draft a proposal for the
design and approval of audible warning devices using the Civil
Aviation Safety Authority's guidelines. Once that has been
accomplished and a CAR 35 Engineering Order has been raised, the
devices will be manufactured by a sub-contractor and installed in
the operator's fleet of King Air aircraft.

Some vital checklist actions from the PRE TAKE OFF checklist and
the AFTER TAKE OFF checklist were not completed by the pilot.
Oppressively hot and humid conditions on the ground would have been
very uncomfortable and likely to encourage the pilot to hasten his
departure. Any haste during departure would have increased the risk
of omitting a checklist item.

The non-standard clearance instruction, received soon after
take-off, required re-programming of the GPS. That action captured
his attention during the climb, and distracted the pilot from
performing parts of the AFTER TAKE OFF checklist and the Transition
Altitude Procedure.

The pilot had expected the routine illumination of the green
auto feather advisory annunciators during the takeoff and for part
of the climb. Consequently he did not identify that additional
green annunciators, in the form of the bleed air off indications,
were illuminated.

The pilot only noticed that the cabin altitude warning lights
were illuminated after the flight nurse had alerted him to the
automatic deployment of the passenger oxygen masks. Because of the
separate pressure switches involved, it is possible that this
deployment occurred slightly before the cabin altitude pressure
warning. Alternatively, or in addition, the sun's relative position
to the aircraft may have partially occluded the master warning
light, making it difficult for the pilot to detect. The inclusion
of an aural warning to operate in conjunction with the visual cabin
altitude warning annunciator would have provided the pilot with an
additional warning during a period of high workload. Desirably, the
aural warning would be triggered by a different pressure switch
than the visual warning.

The operator's instruction that permitted completion of the
AFTER TAKE OFF check "as workload permits", allowed for
postponement of a critical check on cabin pressurisation until well
above 10,000 ft. Postponement of the AFTER TAKE OFF check also
maintained the Auto Feather in an active state, and kept the green
annunciator lights illuminated.

The pilot chose not to put on the oxygen mask, as required by
the operator's Emergency Procedures, when alerted to the lack of
pressurisation. That action resulted in a risk of the pilot
suffering from hypoxia had the aircraft continued to climb in an
unpressurised state.

The Beechcraft Super King Air 200 aircraft had arrived at Timber
Creek NT to conduct an aeromedical flight to Tindal NT. The
aircraft had the pilot, a flight nurse and one patient on
board.

While on the ground at Timber Creek, the environment had been
oppressively hot. Both the pilot and flight nurse reported feeling
extremely uncomfortable and had both been perspiring profusely. The
aircraft's airconditioning system was not operating properly and
had offered little respite from the conditions, either on the
ground or in the air. Due to the type of injuries that the patient
had suffered, the flight nurse had requested that the pilot
maintain "sea level" cabin pressure for the return flight. The
flight nurse had also fitted an oxygen mask to the patient. The
pilot recalled setting the pressurisation controls to suit the
request from the flight nurse.

On the inbound flight, the pilot had been advised by Air Traffic
Control to expect a non-standard clearance for the return flight
due to RAAF aircraft activity in the area.

Following take-off, at about 2,000 ft, the air traffic
controller instructed the pilot to intercept the 173 radial at 120
NM from Tindal, and then to track along that radial to Tindal. That
had been necessary to avoid the now active Military restricted area
R248(B). The pilot reported that he had then become occupied with
re-programming the aircraft's Global Positioning System (GPS).
During the climb to the cleared level, Flight Level 130, the pilot
reported that he believed that he had actioned all the required
checklist items.

As the aircraft climbed through FL125, the flight nurse noticed
that the passenger oxygen masks had deployed and conveyed that fact
to the pilot. The pilot was unaware of the deployment and had
immediately turned around to assess the situation. When he turned
his attention back to the instrument panel, the pilot noticed that
the cabin ALT WARN caption positioned on the glare-shield mounted
Master Warning panel was illuminated. Both Master Warning captions
were also flashing. The pilot then contacted Air Traffic Control
and received a clearance for an immediate descent to 10,000 ft.

The flight nurse donned the nearest available passenger oxygen
mask and re-checked the flow of supplemental oxygen to the oxygen
mask worn by the patient. The pilot did not don an oxygen mask
during the incident.

Once established at 10,000 ft, the pilot discovered that both
the left and right bleed air OFF green advisory annunciators were
illuminated, and that both bleed air switches were in the ENVIR OFF
position. In that position, no bleed air was available for aircraft
pressurisation. The pilot had then selected both bleed air switches
to OPEN, and restored normal pressurisation.

The flight was then continued to Tindal at the lower
altitude.

The pilot was appropriately licensed for the flight and had
approximately 3,600 hours total flying experience, of which 90
hours were on King Air 200 aircraft, with about 50 hours as pilot
in command.

The Operator's Pre-Take Off Procedures required the bleed air to
be selected to ON (OPEN). When the three-position bleed air
switches were selected to EVIR OFF or INST & ENVIR OFF, a green
advisory light L or R BLEED AIR OFF annunciator was illuminated.
The pilot reported that he could not remember having selected the
switches to OPEN prior to take-off.

The pilot indicated that he had not noticed the green L or R
BLEED AIR OFF annunciators during the climb. He reported that that
was partly due to him being accustomed to seeing the green L and R
AUTOFEATHER advisory captions illuminated on the lower centre
instrument console during the takeoff. The pilot was also unsure if
the ALT WARN and Master Warning caption had been illuminated prior
to him being aware of the passenger oxygen mask deployment.

The operator's After Take Off Procedure included a requirement
to turn the Auto Feather "OFF not below 1500ft". The pilot reported
that the task was often left until after the transition altitude,
when the cockpit routine was "less busy". That meant that the green
L or R AUTOFEATHER advisory captions would remain illuminated until
the checklist was completed, sometimes up to FL 150. The operator's
After Take Off Procedure included a note, which indicated that the
checklist only needed to be completed when workload permitted.

The After Take Off Procedures also required the pressurisation
to be checked. That task involved the pilot checking that the bleed
air valve switches were OPEN (up) position. The pressurisation
gauges were also to be checked to ensure that the aircraft was
pressurising normally. The Transition Altitude Procedures stated
that "pressurisation checks should be made at least every 10,000 ft
during climb and again when stabilised in the cruise".

The operator's Phase One Emergency Procedures, for a loss of
pressurisation with the cabin altitude above 10,000 ft, directed
the pilot to don the crew oxygen mask. The pilot reported that he
had not performed that task as he had quickly descended the
aircraft to 10,000 ft.

The aircraft's air conditioning system had a history of
operating problems, with six instances of maintenance recorded
since January 2001. The flight nurse said that the airconditioning
system had been malfunctioning for some time prior to the incident,
and that the aircraft had been to Darwin several times for repair.
The crew also indicated that on the flight from Tindal to Timber
Creek the interior of the aircraft had been hotter than normal and
that it had not operated at all on the incident flight.

The maintenance record entry following the flight indicated that
the airconditioning system high-pressure switch had tripped.
Maintenance troubleshooting found that the system gas pressure was
incorrect and the pressure had been subsequently adjusted.

The aircraft's cabin altitude warning system and the passenger
emergency oxygen mask system were both designed to operate at a
cabin pressure altitude of 12,500 ft. The two systems were separate
and operated in response to electrical signals received from
individual pressure switches. The cabin altitude warning system
illuminated both the glare-shield mounted flashing red Master
Warning annunciators and the red ALT WARN annunciators on the
warning annunciator panel. The passenger emergency oxygen mask
deployment system activated a green PASS OXY ON annunciator on the
aircraft's Caution/Advisory panel.

The operator had installed an aural warning device that operated
in conjunction with the cabin altitude warning annunciator, into
this aircraft on the 30 November 2000. That device had been
installed under a CAR 35 engineering approval. On the 23 February
2001, following an instruction from the Civil Aviation Safety
Authority that the device had to be removed because it had not been
manufactured in accordance with current legislation, the unit was
removed from the aircraft.

The sun's azimuth was 282 degrees true, which meant that the
sun's light came from behind and to the left of the aircraft. The
sunlight glare from the West may have occluded the red master
warning and the altitude alert on the pilot's side and centre of
the instrument panel glareshield.

A text by Thomas Turner, titled "Checklists & Compliance",
written on the use of checklists in aircraft operations, pointed
out the problem with operating equipment such as global positioning
system units in "altitude critical areas". Such areas were defined
as within 1,000 ft of the ground or within 1,000 ft of levelling
off from a climb or descent. The textbook went on to say
"Concentrate on what it takes to establish the new level flight
attitude, trim the aircraft for level flight, and check to make
sure critical items are complete before turning to less crucial
tasks".

A Civil Aviation Safety Authority booklet "The Global
Positioning System" stated that:

"GPS may relieve the mental task of computing the aircraft's
position and speed in relation to maps of the terrain, but it may
increase the workload of programming and accessing the desired
information from the machine and interpreting it.

"Piloting an aircraft requires continuous monitoring and
reacting to events both inside and outside the cockpit.

"The amount of information we can deal with at any one time is
limited....

"Don't allow the operation of the GPS to interfere with your
primary task of flying the aircraft".

Aircraft Details

Manufacturer

Beech Aircraft Corp

Model

200

Registration

VH-SWP

Serial number

BB-529

Operation type

Aerial Work

Departure point

Timber Creek, NT

Departure time

1333 hours CST

Destination

Tindall, NT

Damage

Nil