Propeller strike during start-up, Fokker F27... - Onderzoeksraad voor ...

1.8 Aids to navigation
Not applicable.
1.9 Communication
Communication between ground crew and flightcrew is possible through an interphone system.
Microphone and headset jacks for the groundcrew are located near the external power
receptacle directly below the first officer’s sliding window. The microphones and headsets are
used from the moment the crew is ready to start the engines. At this time the microphone
selector switch is selected in the cockpit to open intercom so the flightcrew microphones are hot.
As a result the mechanic will hear everything that is said on the flightdeck. The mechanic has to
push a transmit button on his microphone to be heard by the flightcrew.
The Fokker 50 has two independent very high frequency (VHF) radios. When only the aircraft
batteries are powering the electrical system (for example when both engines are shutdown
without the auxiliary power unit (APU) operating or external power being connected), only one
VHF radio is available. In this situation the aircraft interphone system is also unavailable.
1.10 Airport information
The aircraft was parked at position B86 facing South West at Amsterdam Airport Schiphol Bapron;
the heading was approximately 240º.
The immediate area surrounding the aircraft was dry and free from fuel and oil spills (see
appendix A).
1.11 Flight recorders
1.11.1 Cockpit voice recorder
The CVR was used for this investigation. Four channels are available, but only three are used
on the KLC Fokker 50 aircraft. The audio signals of the captain’s and first officer’s audio selector
panels are recorded on separate channels and one channel records the audio signal picked up
by the area microphone. The recording was of good quality and lasted for approximately six
minutes after engine shut down. All conversations between captain, first officer and mechanic
were clearly audible.
Several distinctive sounds could be heard on the CVR. When the mechanic plugged in his
headset a characteristic click was heard on the first officer’s audio channel. The same click was
heard when he disconnected his headset and a few seconds later the area microphone channel
recorded an unusual “ffrrrt” sound. It is assumed that this was the sound of the mechanic coming
into contact with the propeller.
The time interval between the click when the mechanic disconnected his headset and the sound
of him coming in contact with the propeller was between three to four seconds.
The time between the mechanic coming in contact with the propeller and the activation of the
engine shut down was about seventeen seconds.
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