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During a VFR flight from Mayerhofen bei Friesach (LOKM) to Zell am See (LOWZ), you reach the waypoint at Mauterndorf (LOSM) four minutes later than planned according to your Operational Flight Plan (OFP). What does this delay suggest?

  • A

    The wind prediction may not have been correct. A stronger tailwind than forecast will lead to around 5 minutes less flight time on the leg from LOSM to LOWZ. The fuel consumption will decrease accordingly.

  • B

    The aircraft flight manual was not correct about the cruise performance. The other data retrieved from the flight manual, such as take-off and landing performance, should be doubted, too.

  • C

    The departure time might have been noted incorrectly. As this is the most likely cause for the deviation from the calculated time overhead LOSM, there is nothing to worry about.

  • D

    The wind prediction may not have been correct. A stronger headwind than forecast will lead to around 5 minutes more flight time on the leg from LOSM to LOWZ. The fuel consumption will increase accordingly.

You're flying VFR from LOKM (Mayerhofen bei Friesach) to LOWZ (Zell am See). While en route, you pass LOSM (Mauterndorf) 4 minutes later than estimated in your Operational Flight Plan (OFP). This indicates that your actual groundspeed was lower than expected.

Assuming factors like heading, power setting, and altitude were as planned, the most likely cause is a stronger headwind than forecast. Wind forecasts, based on upper wind models, are not always accurate in real-time conditions.

A reduced groundspeed means the aircraft is covering less distance over the ground per unit of time. This leads to longer flight times between waypoints like LOSM. As the engine runs longer to cover the same leg, even with unchanged power settings, fuel consumption increases accordingly.

  • "The aircraft flight manual was not correct...": The AFM provides performance based on still-air or standard conditions. It's unlikely that the AFM cruise data is wrong due to a 4-minute timing error.

  • "The departure time might have been noted incorrectly...": If that were the case, all checkpoints would be shifted by that same amount. Here, the discrepancy was noted en route, suggesting an in-flight factor like wind.

  • "A stronger tailwind...": If you had a stronger tailwind, you’d arrive earlier, not later.

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