View Full Version : 737 Jockeys Questions

7th Apr 2010, 15:12
Hello Guys,

some tricky ones for me.

1.The normal threshold crossing alt during ILS approach is 35ft right? So what is the Altitude we cross the beginning of a normal approach lightning system at an ILS approach?

2. What do you guys have beside the option of a go around in a situation: the flaps dont come out before intecepting the glide slope. So like a flaps up landing. Any values for your head like how much runway do i need etc.
Same for flaps 5 etc. What will you do with flaps 25 stuck?

3.What is the real truth about the wx radar and birds at CAVOK-situations? Isnt that an old opinion?

Thanks folks

7th Apr 2010, 16:22
No, TCH (threshold crossing height) is normally around 50' and published on the jeppy plates. Crossing height of the beginning of the approach light system obviously depends on both the design of that system and the GS angle. There is no single number.
The safe option is to go around and sort it out slowly.
Been discussed to death here on PPRuNe and elsewhere. Modern WX radar does not scare birds.

7th Apr 2010, 16:41
I think you might like to check your books. I will refrain from judgmental comments.

We expect to be at a height of 50 feet when crossing the threshold . Altitude is something different.

Approach lights obviously vary but 900 metres is a length you might use.

You would then be around 150 feet above the start of the lights, although given you cannot look straight down, the start of the lights may not be the key issue in CAT 1 minimum weather.

A crossbar at 300 metres (sometimes called a decision bar) giving you horizontal cues to transition visually is a key design element of approach lights and the minimum expected in a simple system.

You can find the data for non normal landing distances in the back of the QRH. I have trouble imagining a situation where you would not break off the approach in this scenario. But as has been said before, in a desperate situation crashing on the airfield at least makes it easier for the emergency services to reach you.

Views differ about birds and radar. Whether it really helps has not as far as I know been proven.