In the interest of more realism in FSX, I'm taking Mark's advice (and a few other's, too), and starting to fly without the FSX ATC. However, I was wondering how you would know when to start your descent in a jetliner that doesn't use VNAV, for instance the 707. Of course, in the 757 or 767, VNAV would start the descent for you, but what if you don't have VNAV? Do you just decide? And in reality, would ATC tell you when to descend, or would you decide for yourself?

Also, how do you figure out the ILS intercept altitude?

Thanks,
boeing247

So you can figure out the whole thing from this.


^^Here, I wanted to be at the pattern altitude for Cairo at 5nm out, so I'm not cutting it close, so thats what I calculated.

Second, to do a proper approach, you should have an approach plate. This give you the waypoints along the ILS glideslope path, andthe altitudes you should be at them. In teh older aircraft, you must nesure the marker be heard at the right spot, and at the right altitude when you hear it (all on the plate). ATC would tell you to descend to an altitude, its up to the pilots to decide at which speed and vertical speed the plane must descend.

Since I fly in real-world, I have a ForeFlight subscription on my iPad, and it gives me all the plates for the United States, for the subscription charge (annual) with no charges to update every 32 days, I have no idea where to find them online. They have Canada now, for an extra charge.

Markoz wrote on Nov 28^th, 2011 at 1:37am:

But if you're using the FSX ATC, it does know that you are flying IFR, right? I mean, if you use it, it actually gave you the IFR clearance.
Haven't used it for years, so I could be wrong of course.

Regarding the winds. Note that the groundspeed of yours is the reference value to determine your rate of descent. By it's nature, it takes the current winds into account and you are of course free to determine a safety buffer for starting your descent.
Winds can change on entering lower altitudes and while the rw guys may take a close look at their forecast data, we flight simmers may just use some extra buffer for determining the right point to start the descent.

Speaking of a 3 degree descent by the rule of thumb, you e. g. would be at FL300 and 90nm out to come in at 0ft. You can add some 10% buffer zone and start your descent at 99nm out, so you can counteract some wind influences.
The trick is to check your descent rate on a regular basis, so don't just start the descent and wish for some luck, but e. g. check it at FL200, 100 and so on. You have to alter your vertical speed either way, which is what a VNAV system does all the time.

701151 wrote on Nov 28^th, 2011 at 12:29am:

I hope this doesn't come in too offensive, but a few weeks back you even advised people that landing downwind would be a 'favourable condition' for a pilot.  
So please accept my apologies, but I'm concerned about aviation safety now.  
www.captainsim.org/yabb2/YaBB.pl?num=1317424001/17#17


On some charts sources. The big online networks rely on the free work and/or accessibility of charts, so they offer most of the stuff one needs. This of course includes countries where official charts aren't available for free, so a Google search for IVAO or VATSIM chart sources often enough leads to nice flight sim ones.
The quality often differs of course, from purely user made ones to just some more or less outdated rw ones.

There are chart programs out there, for a sim use. They read the Navigraph data and then generate charts, even allowing them to be customized or running as a moving map. One doesn't need a Navigraph subscription of course, they come with a pre-installed dataset which is ok for the every day flying.
However, a Navigraph subscription isn't expensive, so one could even update the dataset every month if needed. There's a 30 day full trial available here. http://www.aivlasoft.com/products/index.html

For instance, the approach chart looks like this. The red symbol is optional and can follow your plane's position if you like. So it may also act as a training tool.

701151 wrote on Oct 4^th, 2011 at 12:38am:

www.captainsim.org/yabb2/YaBB.pl?num=1317424001/17#17

Peter, I think you are the guy sitting next to a pilot (which is flying). Not the one being legally responsible for the flight. Am I wrong?
I doesn't matter much though, but I was surprised about the 'downwind statement' of course. Maybe that's why I recall it.   For a sim usage, this is no problem of course. It's just a different beast if I do things right or not so right in my sim, or if I explain certain items to others, mixing them up severely (180 degrees to be precise). But it's a sim for a reason and I enjoy the freedom there, maybe in the same way as you do.

No problem with stating wrong things, but you are sometimes very confident about them, which may distract some other people.  
Blaming some typos when the context is mixed up .. well. Yeah, lets keep it that way since saying 'I was wrong' is a hard thing to do for some.  
I've just reacted on the very confident statement of yours I think. Apologies.

No problem with that, Peter. I also notice your positive attitude to help others, which is a great thing. So keep that one up and maybe work on the .. typos.  


Your descent plan is a nice thing for example. Maybe you could add your used formulas for others to be able to work out one by themselves.

Very good description, Pina. Mind the groundspeed as reference for the VS.
By the way, did I mention that I've found some nice freeware for South America and with a lot of details for Brazil? http://www.fsxamericagigascenery2010.xpg.com.br/ It was a pain to download, but is a fun to fly and explore. And your country offers some nice views and approaches.  

Windplayer et al, in the real world descent profiles are generally standard at a 3 degree profile to get you nicely onto the ILS or IAP fix, as indicated above the way to work it out is simple, some people use a 4 X profile but the outcome is the same.

Here is what we (I) used to do and what I taught as an instructor and check and training captain for years on a variety of real aeroplanes. Once you understand it, it is actually simple math then it become simple and all the tools you need are in the cockpit- Airspeed indicator, Altimeter, Distance readout (DME or GPS) and an approach chart.

ALT x 3 is distance to commence descent minus the altitude of the aerodrome and or IAF (instrument approach fix) commencement altitude:

EG. Your at F330 the ILS starts at 3000ft and airport elevation is say 100ft. 3x33 =99 nautical miles TOD to go all the way down at that profile, speed is generally irrelevant so you can barber pole or max or stay at a speed profile depends on the aircraft. Slowing down is the issue and you need to slow the descent and go level now and then to reduce speed and then keep descending (in a big and heavy aeroplane that may require a minute or two at level speed to deaccelerate or slow down, then away down you go again,

If the aerodrome your goind to land at is say at a high elevation then you take that off for example, aerodrome is 5000 ft then you actual height to lose from F330 is 28,000 feet, so F280 multiplied by 3 gives you - 84 nautical miles. For all intents and purposes ignore the last 0 on the FL. Remember you need to be ready to go and prepared by looking at the approach etc way before the descent point and then waiting for it to arrive and away you go.

So how do you stay on profile all the way down and as you slow the aeroplane to different speed profiles for the approach and landing?

The answer is quite simply you match your ROD to the IAS - How?

You divide IAS speed by 2 to give you the required rate of descent to stay on profile, hence:

If you descending at 300 kts then your ROD is 1500 fpm
if your descending at 225 kts then your ROD is 1100 fpm
if your descending at 200 kts then your ROD is 1000 fpm
if your descending at 180 kts then your ROD is 900 fpm
if your descending at 150 kts then your ROD is 750 fpm and,
if your at 120 kts your ROD is 600 fpm.

And so it goes.

So all you have to do is change the pitch attitude up or down to keep to or obtain the desired rate of descent.

You can check your profile if you have GPS or DME as you will go through 1000 ft of altitude every 3 nm. So if your a little ahead because of wind then you increase your ROD to stay on profile, or if your getting behind because of a headwind you decrease the ROD.

So you can easily check how your going by taking the distance and dividing it by 3 to find the altitude you should be at with a 3x profile, e.g. at 21 DME or NM you should be at ? 7000 ft. AT top of descent or 99 nm divided by 3 gives? guess what F330.

See how it works, the trick of using ROD to keep on profile means as you reduce speed by the time you arrive at you FAF or commencement of the ILS for example, your on profile and this works for all aeroplanes no matter what type. The great thing about this technique is that you also fly the Instrument Approach the same way by managing your ROD and you will also find that this matches very nicely the ROD or descent rate required for the speed to fly an ILS or other instrument approach.

Hope this helps, happy to put together a quick downloadable tutorial if people really would like this. 

It only becomes a bit of an art form when you want to fly say an non precision approach (NDB) or DME Arc arrival then you need to work back on all the distances including the arc distance to work out your descent point - but that as they say is for another time.