Simviation Forums

What is the importance of landing on the glide slope perfectly? What if it isn't perfect colored lights in the VASI? What if the plane is all red 10NM away at 2000ft and is 1 white over red at around 5NM away? Is it still good or a perfect white over red is what real pilots do?

It depends on the plane and the conditions. It's mostly just a reference. Being exactly on a glideslope becomes more important, the bigger and faster the plane. A safe approach angle for a Cessna172 into a stiff headwind, is different than that for a Lear in zero wind. The angle that the lights give you is published for each runway.. so you adjust accordingly for the plane you're flying and the conditions at the time.


Edit:

When you are far away from the airport, the glideslope matters quite a lot, as it keeps you from hitting random buildings or power poles as might happen if you get too low. As you get closer to the airport, obstacles tend to get smaller (if they are getting larger, either you need to lay off the drink, or clip them down *ahem*) the VASI lights and glideslope indicator become less a requirement and more of a simple reference. But always remember: better too high then too low, because if you're too high, you usually get another chance, too low, not as much.

That's my general opinion on ILS glideslope and VASI visual approach. It is not coming from a professional pilot, but it gets me on the ground quite nicely, so it seems I'm on point here.

When you are far away from the airport, the glideslope matters quite a lot

Again.. this is situational. Your approach to an airport (even in a KingAir or Lear) can have you at 3000agl some ten miles out and you'd be way below the glidslope..

Note on capturing the ILS that on the visual VASI / PAPI lights you will always tend to be showing "low" until you capture it... 'cause you have to intercept it from below.

best,

....................john

Right at the start, let me say that this is flying a kite to stimulate discussion - nothing else!    The ILS is an approach aid, not a landing aid.   It's function is to put you in a position from which you can - when you see the runway- transition to a visual approach and landing.      That being the case, I have always wondered why the ILS touchdown point is positioned some 200 yards down the runway.    On a dark and dirty night with weather minima, you tend to break cloud at a point very close to the end of runway still flying at your approach speed - with maybe a knot or two in the bank for the wife and kids.     I've had this once or twice and it's a real gut wrencher to find yourself over the runway going like a bat out of Hell.      This has often led me to wonder why the ILS touchdown point is not positioned (where topography allows) something like 200-500 yards SHORT of the runway.        You would then fly a perfectly normal ILS down to break off height.        If you could not see the runway or the approach lights, you would carry out the standard missed approach procedure.     If you could see the runway or approach lights, you could transition to a normal visual approach with a bit of time in hand to get your rate of descent and speed down before the wheels hit the concrete.       I should say that every one of my colleagues with whom I've discussed the idea disagrees with the idea - but then most pilots are conservative by nature.       It's never going to happen but, at least, it might be worth thinking about.      Please, no abusive replies!

Brett,   Always a pleasure to have your comments - and I don't disagree with what you say.     The only point I would make is that when ILS was installed at the majority of airports, approach and touchdown speeds were somewhat lower than is the case with some modern - or reasonably modern - aircraft.    Some are now edging up to the 190-200K category.     At speeds like that, you want every bit of runway you can get.    Anyway, it was just something to think about

It sure did make me think.. thanks.. I like thinking and talking about this stuff... You're right, in that I'm certain 90% of ILS approaches end up with a pilot landing long.

Probably too much equipment to maintain..

Too much to buy. ILS is expensive. Our local airport, KIRK, put in a used ILS system at a cost of over a million bucks. More like 1.5 million, I believe.   That's right, USED.

Another point about the touchdown point being down the runway a bit, there are aircraft and pilots certified to fly an aircraft all the way to the concrete without visual reference. I forget the designation, CAT III?   THEY sure wouldn't want to point short of the runway.

This a reply to rafair about the displaced touchdown.

If you are flying a small jet say a an A320 then as you go through screen height at about 35ft you should touch down with all parts of your a/c spread over the rwy. If you are in a heavy however, the majority of the a/c will land short. This is because of it's sizeand the higher pilot eyepoint.

To get back on topic the ILS beam frequently does not match the VASI or PAPI red and yellowas the ILS is intended for IMC and the neccesity to bring a/c down in a continuous descent and clear of ground obstacles which in VMC should be obvious.

The other point mentioned about decision height is important. "A good landing is made at the top of the glide slope" was something that was drummed into me during my pilot training. So anticipate any divergnce from the glideslope and make small corrections. If by decision height there is no guarantee that "all" the a/c ill make it onto the tarmac the "go around" I say again "go around!"
Vololiberista

Not going to add much here except that the VASI/PAPI lights in FS9 are based on the viewpoint of the camera...So if you were to go to Spot view and move around the camera as the aircraft is on short final, you'll see that the lights constantly change with respect to the camera

[quote]Brett,

as far as I know the only civillian a/c that touched down at speeds above 160kts was Concorde. Most approaches are never more than 180kts for any jet (for Concorde it was 190kts). The critical speed is Vat which depends largely on the weight of the a/c at the end of it's flight. Vat=Velocity at threshold. It can vary from anything around 170 down to 5kts above stall and is one of the reasons why most jet transports cannot land with a full load of pax and fuel. a. they are too heavy for the undercarriade and b. there isn't enough rwy in front to stop safely.
Vololiberista

Just a let-know, different angles (say, Spot view) will change what the PAPI says. [smiley=thumbsup.gif] Just a let-know if you use an oustide view.