Computerized Flight Plans

CAUTION!  Computers make mistakes! 

Everyone likes how easy it is to use a computer generated flight plan.  Quick, easy and to the point.  Wham, Bam, thank you mam and you're on your way.  But wait..... Does your flight plan pass the common sense test?  Do the TAS, ground speed, fuel burn and ETA jive? 

Recently I've seen computerized flight plans that are not accurate.  Why? Good question.  Sometimes the wrong airplane was selected.  Maybe the wrong cruise data was entered by mistake.  Maybe the winds aloft where not included or the wrong departure time was entered.  The errors what where discovered where quite noticeable.  One flight plan had used the wrong winds aloft showing a tail wind of 20 knots.  In reality there was a headwind of 20 knots.  Another flight plan I've seen showed a fuel burn of 36 GPH.  In reality the airplane burned 20 GPH.  An yet another showed a Compass Course that was 90 degrees in error!

As Ronald Regan once said, "Trust but Verify".  I use simple rules of thumb.  I know my airplane flys at 133 KTS at 21" and 2200RPM.  At that power setting she burns 12.7 GPH.  With a quick look at the winds aloft and can see if I have a headwind or tailwind and come up with a rough ground speed and ETA.  Run that by the computer flight plan and see if you're close.  If not, something is wrong!  Find out whats going on.