Alright hey guys, so I've understood the basics of flying IFR, so now I'm actually starting to fly the aircraft.

But there is a major problem, I can't learn because the autopilot is messing up.

So when I reach my cruise altitude my speed looks fine, but then when I reach my top of descent with flaps 15, my planes hits overspeed which is weird because when I'm flying the overspeed is at 240 knots, which is really weird.

So it hits overspeed then my plane takes a extremely sharp left, can't recover it either. I really want to start landing but it's just not possible with this problem. 

My FMC looks perfectly fine, CLB, CRZ, DES, everything looks good, speeds, etc.

Someone please help me,

Thanks.

P.S. I'm using LNAV and RNAV for the AP.

Hi,

Sounds like you are really enjoying flying your simulator, especially some of the more complicated aircraft. My first thought when I read your post is the aircraft went into a stall spin due to what is called a split flap condition. You did not mention what altitude you were at when this happened but you had said you where at the TOD (top of decent).

 

Deploying flaps when you are going this fast would most l likely damage them physically and the air loads would not allow them to come down evenly on both sides of the aircraft. If this is the case.  That is why your aircraft rolls out of control to the left due to the flaps deploying on the right side with the left side flaps retracted. This would cause the aircraft to roll to the left and put it out of control if not corrected.

 

You did mention that your speed was 240 kts which would be OK if you were at a much lower altitude. If you were at your top of decent, then you would me at a cruise speed of say Mach .76 with an indicated airspeed of around 230 kts (indicated). Your ground speed and true airspeed would be much higher. (maybe around 450 kts) As the aircraft goes up in altitude, the air gets thinner (less air molecules which allows for greater speed and less fuel burn)) 

 

The primary airspeed the aircraft cares about is the (Indicated) airspeed. That is what you see on your airspeed indicator. The pitot tube measures the amount of air molecule's entering it to give you the indicated reading.  Your aircraft's wings are designed to produce a certain amount of (Lift) for given amount of speed. The air has to flow over and under the wing to do this.

 

For aircraft like the 737, in order for the wing to work efficiently at cruise, it needs a wing that has less drag and more speed. For this same wing to work efficiently when landing, it needs more lift and drag. That is why there are flaps and slats on the wing so as to change the wing area from a cruse to a landing wing design.

 

It appears you were trying to set the wing into the landing mode while the aircraft was still in the high speed cruse area. Sorry but the two do not mix well. If you were to deploy the flaps to 15 once you were down at say 2000 feet above the ground setting up for landing, the air would be much more dense (more air molecule's) and the airspeed indicated would match what the wing needs at that altitude and speed in order to create enough lift for safe flight.)

 

There are different ways you can set up your decent from cruse depending on what altitude you are at. In most high performance aircraft like the 737, pilots will just reduce the throttles to allow for the same or slightly higher (Indicated) airspeed as the come down in altitude. This requires some planning to figure out when to start down. That point is your TOD (top of decent) In most cases it cane be 100-150 miles from your landing airport. Another  would be you want or need to stay higher altitude as long as possible to save fuel or at ATC (air traffic control's request) Now maybe you only have say 90 miles to get to your landing approach altitude. In this case you can now deploy the (Speed Brakes) They do two things. They create drag and cut some of the lift the wing is producing. This will cause the aircraft to decent quicker without building up additional speed. Once the aircraft has reached it's normal approach altitude and airspeed, these are usually stowed so as not to interfere with the normal landing wing configuration.  You might see them again on the ground after landing along with what are called ground spoilers which are designed to stop the wing from producing lift and to place more weight on the wheels and allow the brakes to stop the aircraft more quickly.

 

Flying the aircraft is the easy part, understand the aircraft systems and how the work might take some time. Knowing when and when not to use a cetin system can as you have found out can either lead to a safe landing or a out of control situation.

 

Hope I did not confuse you too much with this explanation There should be tutorials (videos) on line that can show you in more detail or simpler terms how to land a aircraft like the 737 from the cruse portion of your flight. Good luck and enjoy your simulated flying.

 

Terry