Ok so when im on approach it always looks like im going way to fast once i get closer to the runway even though im using the approach speed that the fmc gives me. Which is usually like 150 (737-800). but my touchdown speed is lie 135 or even lower. What is a safe touchdown speed and how are you supposed to know what touchdown speed to use.

Welcome to AVSIM!

 

While VREF serves as a base approach speed for additional wind correction (for the B737, wind correction equals half the steady headwind component + the full gust factor), your approach speed should be at least VREF + 5 kt, regardless of the absence or presence of winds. For example, when flying an approach in calm winds, maintain VREF + 5 kt. When flying an approach with a headwind component of 8 kt, maintain VREF + 5 kt. When flying an approach with a headwind component of 12 kt, maintain VREF + 6 kt, not VREF + 5 + 6 kt = VREF + 11 kt.

 

Ideally, touchdown should occur at VREF + gust factor, which indicates that you should bleed off the steady headwind component adjustment (at least 5 kt) through flaring. While the B737 FCTM recommends touching down between VREF −5 kt and VREF + gust factor, I would say anything between VREF −10 kt and VREF + gust factor is acceptable.

When your in your fmc during flight, it will give you ils frequencys, course etc. to the right of that it says the speed for the flap selected.

For example:

 

30/150-----------> the 30 means what flap you have chosen to land on and the 150 is the speed indicated to land on the flap.

 

If you think 150knots is fast for flap 30 ( i think its a tiny faster than average) Then make sure before you take off you configure your fuel and payload properly as these are crucial towards how heavy your landing will be.

 

To sum up if your fmc is telling you to land near that speed at a certain flap, then do so as the fmc will give accurate speeds.

Yes that's what I'm looking at and I generally use 30 flaps because I believe that's used more commonly then 40? I might be too heavy on landing, what's a good way to calculate fuel needed for a flight?

what's a good way to calculate fuel needed for a flight?

I do not own the PMDG B737, so I do not have access to its training materials, but if the latter are similar to those of the PMDG B747, there should be a section describing fuel calculation. I used that section in the PMDG B747 AOM to program an Excel spreadsheet for automated calculations.

 

Alternatively, you could try searching Google. There are numerous results, though I do not know whether they are accurate or not.

http://fuelplanner.com/index.php

 

This homepage caculates the fuel.