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FSNavigator 4.6 problem

Pro Member First Officer
W3CPR First Officer

Hi.. I have been using FSNavigator 4.6 and ran into a strange problem. When I fly from Bogota Columbia SKBO to Cali Columbia SKOL, I never make it. No matter what route I use either automatic or manual, the aircraft never makes it to the assigned altitude. Any time after about 25,000 feet the airspeed starts to drop and eventually the aircraft will stall. I have the pitot heat and ice switches on but that doesn't help either. I am using the 737-400 and the Lear 45 and both act the same way. This is the first time I have run into this as both aircraft can make it to 35,000 feet with no problem but that was over the United States so I am wondering if there is a bug in the FSNavigator somewhere. When I fly the aircraft manually I have no problem. I have AP and Fly FP engaged on FSNavigator when flying the flight plan.

Thanks

3 Responses

Helper Guest

It may be your remaining fuel load weight is too heavy. Are you stepping up through the altitudes to burn off fuel weight or doing a continuous climb through 25,000?

Pro Member First Officer
W3CPR First Officer

Hi and thanks for the reply. I have been doing some tests on various aircraft and notice that as you go up in altitude, aircraft have a difficult time in getting to the top of the climb at 33,000 feet. I believe the FSNavigator is trying to get to the max altitude at a rate that is not achievealbe such as climb rates of 3500 feet per minute in some spots. At altitudes above 25,000 feet you have to be careful of many things such as those that you mention. It appears that as you approach these altitudes and have to climb higher you have to decide on the climb rate, weight and speed, any of which can cause problems. I have found that most commercial aircraft have to reduce their climb rate above 25,000 feet or so. If you do a direct climb from takeoff to lets say 33,000 at a climb rate of 1500 FPM, you find that around 27,000 feet or so you will have a drop in airspeed from 300 MPH and steadily decreasing unless you drop the rate of climb. I believe at some point in FSNavigator you have to take over manually for the last several thousand feet in order to reach the top of your climb, then you can get to your original speed setting. These are the conclusions that I have come to and may not be correct but it is pointing to a problem like I have described. Thanks for your reply.

Helper Guest

In FSNav you can set the crossing altitude (before and after) on individual waypoints along the route. You may need to add some points manually and hold your altitude between those points to allow for fuel burn-off.

That means you'll need to calculate what your weight will be at each way point and only increase altitude as weight allows.

Even on long-haul flights it is unlikely you'll need a 100% fuel load at the start of the flight. Set the fuel load to enough for the duration of the flight plus 1 hour. You can get speed/altitude burn rates from the aircraft specs, if not in FS, then by searching around the net.

3500 fpm is definitely excessive after the initial climb out. After reaching say 20,000 feet, you would need to scale that back to around 500 fpm in a steady climb to 35,000 and above.

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