The Boeing 737 was on a scheduled service from Adelaide to
Melbourne. The crew had flown a standard arrival route to a
locator/distance measuring equipment approach to runway 27. The
weather at the time was overcast with the cloud base at about 2,000
ft with drizzle. Extensive airport works were being conducted on
and near runway 27. When the aircraft encountered visual
conditions, the pilots found the aircraft high on the approach and
attempted to regain the glide path by increasing the aircraft's
rate of descent. As the aircraft approached 500 ft above ground
level, the rate of descent was assessed as too high and the first
officer called for a missed approach to be conducted, which was
carried out by the pilot in command.
The aerodrome controller (ADC) instructed the pilot to maintain
runway heading, to maintain 3,000 ft, and to call the departure
controller radio frequency. Approximately 1 minute later, the
departure controller advised the ADC that no radio contact had been
made with the aircraft. Subsequent attempts to contact the pilot by
radio on several other frequencies were unsuccessful. The departure
controller also noted that the aircraft had climbed to 3,400 ft.
After approximately a minute, the pilot re-established radio
contact with the ADC and advised that he was unable to contact the
departure controller. The ADC instructed the pilot to climb to
5,000 ft and to attempt to call the departure controller. The
aircraft was observed to climb to 5,400 ft and subsequently the
pilot established radio contact with the departure controller.
The pilots thought that the reason why they had been high on the
approach was because they incorrectly transcribed the information
from the operator's internal notice to airmen (INTAM) regarding
amended procedures due to the aerodrome works. The departure
controller requested the pilots to confirm the aircraft's altitude
and it was during this check that the pilots realised that the
barometric settings on the altimeters had not been set to the
airfield QNH of 1028 hectopascals (hPa) but rather had been left on
1013 hPa; the setting required for flight above the transition
altitude (10,000 ft.) As a result, the aircraft altimeters had
under-read by about 450 ft. Once the pilots had corrected the
error, the subsequent approach was conducted without further
incident.
QNH is the mean sea level pressure derived from the barometric
pressure at the station location. The local QNH at an airport is
normally derived from an actual pressure reading. Australian
aviation regulations require that, when an accurate QNH is set on
the pressure-setting subscale of an altimeter planned for use under
the Instrument Flight Rules, the altimeter(s) should read the
nominated elevation to within 60 ft. QNH should be set on the
altimeter pressure-setting subscale of all aircraft cruising in the
altimeter setting region, which extends from the earth's surface to
the transition altitude of 10,000 ft in Australia. QNE is the
standard pressure altimeter setting of 1013.2 hPa that is set for
flight above the transition altitude.
The works and consequent limitations on the use of the runway
were detailed in a notice to airmen (NOTAM) and in an Aeronautical
Information Publication Supplement (AIP/SUP). Some of the
restrictions and amendments to the runway 27 usage included a
displaced threshold, the installation of a precision approach path
indicator (PAPI) vice the normal T-VASIS (which was unavailable)
and non-availability of the high intensity approach lighting.
The first officer's experience was primarily on the 737-400 and
the pilot in command had primarily flown the newer 737-800, which
was equipped with significantly more integrated and up-to-date
cockpit displays compared with the 737-400. One of the altitude
indication features available on the 737-800 primary flight display
(PFD) automatically highlights, in boxed amber, the barometric
setting if the STD (Standard) QNE, rather than the local QNH is set
and the aircraft descends through the transition flight level. The
electronic altimeter is connected to the aircraft's flight
management computer (FMC) and therefore can register if the
subscale has been changed or not by reconciling the altitude to the
database transition and whether or not STD is still set. The
737-400 cockpit displays did not have a similar indication because
the altimeters are not connected to the FMC database that includes
the aerodrome transition level/altitude information.
Both pilots were on the third consecutive day that required a
0600 departure. They both reported retiring the previous evening
between 2000 and 2100. The first officer reported that he had some
preoccupation with health issues involving his child. The pilot in
command reported that on a later sector that day, he began to feel
unwell, experiencing flu-like symptoms.
The instrument approach conducted by the crew was an
operator-modified version of the published procedure. The amended
approach was issued via a company INTAM that raised the published
minimum DME altitudes by 73 ft. Because the modified approach was
issued via text rather than a chart, the crew was required to
transcribe the changes from the INTAM to their own in-flight
briefing notes and they reported that they had taken some effort to
ensure that they had transcribed the amendments correctly.
The operator had a sterile cockpit policy that applied from when
the fasten seat belts sign was illuminated to when the landing gear
was lowered. During this period, the cabin crew was not to contact
the technical crew on the flight deck unless an urgent
safety-related message needed to be passed. The fasten seat belts
sign during this approach was illuminated at 20,000 ft.
The operator's pilots recall the checklist by referring to
information listed on the yoke of the aircraft controls. A sliding
marker was used to indicate where a checklist procedure was
suspended to assist the pilots to regain the place in the
checklist. In this case, the descent approach checklist
included:
- Anti-Ice ON/OFF
- Air Cond & Press SET
- Altimeters & Instruments SET & X-CHECKED
- N1 & IAS Bugs CHECKED & SET
The operator's flight crew training manual required the descent
approach checklist to be initiated during the descent and completed
passing 10,000 ft. In practice, to enable a crosscheck of the
altimeter settings, the pilots were required to stop the checklist
at `Altimeters & Instruments' until the aircraft had descended
below the transition altitude.
The pilots reported that after sterile cockpit procedures had
been invoked and while they were conducting the descent approach
checklist, a cabin attendant mistakenly contacted them on the
intercom. The barometric subscales on the altimeters were not
adjusted after they had recommenced the checklist following descent
through the transition altitude.
A later opportunity to correct the missed check was lost when
the pilots reported that they had crosschecked the altimeter
settings and indications during the approach but they did not
notice that the QNH had not been set. When the aircraft became
visual at about 5 NM on final approach, the PAPI indication was
four whites, indicating that the aircraft was high on glidepath. On
seeing the airport, the pilots momentarily accepted the PAPI
glidepath indication as being normal, as it was what they would
have expected to see for an `on-glidepath' indication when using
the T-VASIS.
Although they quickly realised their misinterpretation of the
PAPI indication and the pilot increased the rate-of-descent to
correct the aircraft's approach profile, the crew were unable to
regain the normal approach as they approached 500 ft height above
touchdown (HAT). Consequently, they conducted a missed approach as
prescribed in the operator's flight administration manual. The
manual advised pilots that an approach should be stable by 1,000 ft
HAT and if the approach was not stable by 500 ft HAT, then a missed
approach, or go-around, was to be conducted. The operator also
stated in the manual that, `Flight Crew are encouraged to perform a
Missed Approach whenever any doubt exists to the safe continuation
of an approach and landing'.
The pilots reported that when pre-setting the frequency it was
possible to dial the frequency on the radio control too quickly and
the selection could overshoot by 0.25 megahertz. They reported that
after they selected what they thought was the departure
controller's frequency, the frequency channel appeared too quiet so
they returned the selected frequency to the ADC frequency where
they regained communications.
The operator reported that the general management processes
taught to the company pilots were based on prioritising response
and sequence management. This was associated with almost all of the
training conducted by the operator, particularly during simulator
training.
