I kinda figured my question about the ILS would be hard to answer.  Just took a shot   Thanks for the tutorial on IAS VS TAS.  I guess I never really thought about the difference.  If you're flying IAS, how do you know if your landing speed is too high (or too low)?

 

 

If you're flying IAS, how do you know if your landing speed is too high (or too low)?

 

For a given weight, your approach speed will always be the same IAS. Your TAS, however, will change depending on your altitude. So if your approach speed is 140kts IAS, landing at Johannesburg, for instance (elevation 5500ft) you will be travelling at 150kts TAS (and assuming zero wind, the same over the ground) at touchdown, whereas the same landing at a sea level airfield you'll only be travelling at 140kts TAS.

 

However, whilst your TAS (and GS) is relevant from the point of view of getting the aircraft stopped, you always fly the aircraft using IAS, because if your unaccelerated stall speed is 130kts IAS at sea level it will also be 130kts IAS at 5500ft.

 

What it does mean is that landing at a hot and high airfield means everything happens much faster because of your increased speed over the ground.

 

Your actual approach speed is calculated based on the weight of the aircraft and configuration you are landing in. It is based off a speed called V_REF -- Threshold Speed. This is the speed of the aircraft as you cross the landing threshold at 50ft and is 1.3x the (1g) stalling speed in the landing configuration.

 

It is usual to fly the approach itself at a slightly higher speed -- usually a minimum of V_REF +5kts, with further additives for wind up to a maximum defined by the manufacturer (usually around +20). This additive is then bled off during the very final stages of the approach in order to touch down at around V_REF - V_REF -5kts (not that the ASI should be the main thing you're looking at in the flare!).

Regarding ILS approaches Here are 2 videos that will answer that question in detail . 

 

https://www.youtube.com/watch?v=ijpiqYldYOY

 

https://www.youtube.com/watch?v=TLW8XbjQctE

 

Now I know that the person who made these video's is in the hall of shame here at avsim, but the videos really will help you learn ILS systems. Give it a try. 

Thanks Skelsey.  Guess I've got to read up on each airliner, assuming the FSX models are made to fly the same as real ones.

Darrinward777, I'll give these a look.

I worked as an electronics tech for the FAA. (32 years)  I understand ILS's from the ground as I maintained them for years but never had the opportunity to see them from the aircraft side.

ILS just make sure you approah from below the glide slope not above or you will have problems and be in landing config. Some planes like the 737 require both NAV radios to be tuned to teh ILS others only require one. Make sure course needle set to run way heading than you all good.