Take-off performance calculation errors
I am currently reading a report about these types of errors. One example I don't understand is what happened in this case. How would a visual departure affect takeoff performance.
"Boeing 737: September 2007
Location: Alice Springs, NT
In preparation for takeoff, the crew calculated the take-off performance data based on a required navigation performance (RNP) departure. While taxiing, the crew were advised by air traffic control (ATC) that there would be a delay for the RNP departure due to an inbound aircraft that required priority. The crew received a revised clearance from ATC to conduct a visual departure. After takeoff, the crew realised that the takeoff data had not been checked or amended to take into account the revised departure clearance."
"A change in operational or environmental conditions was recorded in six of the 11 occurrences. This change necessitated the crew to either check, amend and/or update the take-off performance parameters previously calculated. These included:
• the ambient temperature increasing above the FLEX temperature
• a change from an RNP departure to a visual departure
• a change from a full-length runway departure to an intersection departure
• MAC TOW re-calculation using a ZFW work-around
• an unserviceable ACARS printer requiring verbal transcription
• a change in V speed/s due to a wet runway."