slant range

[EK773ER]

Top o the Morning to you all!

Need some experience sharing on the matter of 'slant range' please.

I want to understand exactly what it is, when to use it, and the easiest way to calculate it please.

Many thanks in advance

[Dash8driver1312]

Trigonometry ;-) slant is your hypotenuse, where the altitude and horizontal distance form your base and vertical. Get back to that A squared= B squared and C squared stuff!

On the other hand, when talking VORs, the readout is always the slant range.

[EK773ER]

Do you have any rule of thumb methods of calculating it?

[Lord Spandex Masher]

DME?......

[EK773ER]

For example, if the minimum visibility required for the approach is 5km from the approach plate, then how do you calculate actual slant range required at minimums?

[qwertyuiop]

Why do people want to make flying so complicated?

[Visual Procedures]

You calculate it as the voice from above says 'minimums'.. If you can see the lights, you have the required slant range


The reality is the vertical component is so small vs the horizontal that there is no difference.

Eg Cat I ILS no lights. 60m (200') vertical, 1500m horizonal.

Pythagoras says the hypotenuse ie Slant vis is 1501m.

Its flying not rocket surgery. No need to over think these things

[Outatowner]

Get back to that A squared= B squared/C squared stuff!

That's not how I remember the theorem. Want to try again?

[albatross]

Even though I have never heard of Slant Vis being given in any forecast, actual or pirep and in 35 years of driving airframes have never heard it discussed exept in relation to DME vs Flight alt. and being that at the range refered to and slant angle being 3 deg that the difference would be very small- fer gawd's sake - instead of being sarcastic why not just say:
A squared + B squared = C squared?
feel free to critique my grammar and punctuation.

[checcker10]

777ER. Please tell me you don't fly the planes in your title?
Cause if you do,how the hell did you get a licence without knowing this.
Get a calculator out and work it out.
Like it seems all the young FOs have to do, to find out ATOW.
Don't they teach you nothing in schools now days...........
Rant Over

(BTW there's probably an app somewhere out there!!!)

[ironbutt57]

good grief...

[Schnowzer]

Royston,

You must be taking the mickey! 460' = 140m. For the 2700 m to work you would need to be on about a 55 degree approach with no lights.

If it is a 3 degree approach, Cos 3 degrees = 1.001, there is cock all difference and any difference is flown whilst the auto-call out says "minimums"

There are 2 issues with slant range! Flying over the airport you get a false sense of security looking straight down through a thin layer of fog, 1500m is 5000' near as dammit so from 5 k you think things are better than they are as you fly past looking down through a 100m layer. The other snag is that Vis can be affected by very low-level inversions occasionally.

But don't bother with slant range and Pythagoras because cunningly approach lights rarely begin at zero DME and extend about 900m short at most places so even on minimums you'll normally get in. That is why at 200 feet which is actually 1/2 nm from the threshold you are nearly over the approach lighting array and can therefore get away with 550m RVR rather than 1000m.

[captainsmiffy]

Who gives a monkeys about slant range? If the viz is legal, get down there and take a look....!! Viz is never cut and dried at exactly what they tell you it is anyway. You can always go around. Too many rocket scientists getting bored and making the job into something impossible when, really, it is a very practical past-time.

[ironbutt57]

admittedly...the "6x" rule was accurate when flying the Kathmandu VOR 02, one would never see the runway if published minimums were in effect

[A Squared]

Originally Posted by EK773ER

For example, if the minimum visibility required for the approach is 5km from the approach plate, then how do you calculate actual slant range required at minimums?

Well, there's some things that don't quite add up about your question, but as a practical matter, for approaches the difference between horizontal distance and slant range is too small to even be displayed on cockpit displays.

If you had a required visibility of 5km for an approach (what sort of approach is that?) If you were 5 km from the runway , you should be at an altitude fairly close to a 3 degree glideslope. That would mean that you'd be at about 262 meters altitude, the slant range from your airplane to the runway would be 5006.8 meters ( the square root of 5000 squared plus 262 squared) So the difference between horizontal and slant distance is 6.8 meters or about 0.003 NM. Cockpit displays of distance are typically only to a tenth of a NM ( XXX.1 NM) so the difference it not only too small to worry about, it's too small to even *see* when you're flying.

[Saltaire]

How about 5X altitude? 1000' above ground would require 5k vis - as in circling minimum? Makes sense?

[OCEAN WUN ZERO]

VHF Slant range

If I remember correctly its:-

1.25 X square root of H1(station elevation) + square root of H2( your altitude)

[Lord Spandex Masher]

OWZ, correct for max theoretical VHF range but it's 1.25 x sqrt your altitude minus 1.25 x sqrt station elevation. Effectively your height above the station.

[ManaAdaSistem]

Can you guys do cross wind landings?

[ekwhistleblower]

Yep in 5 x the wind of most airlines!