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Thanks for your nice comment, CoolP.

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windplayer, actually you are using dead reckoning process to calculate one's current position by using a previously beacon, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course. Despite the disadvantage of dead reckoning is that since new values are calculated solely from previous values, any errors and uncertainties of the process are cumulative, but it works.

Cheers,

Pinatubo.

CoastalDriver wrote on Nov 28^th, 2011 at 10:55pm:

Another great post. But I'd make that 'IAS' a 'GS' (for groundspeed) since, otherwise, you will not fly a 3 degree approach but something else in a more pointed angle, especially when starting high, where your IAS reading is low.

As an example, I'm currently at FL330, IAS is 270 kts, GS is 513 and the only speed defining how fast I get closer to my destination is the GS. If the winds change, my IAS will stay the same, but my GS will change, I would have to recalc my VS setting. That's the spirit.

So my initial descent rate would be approx 2500 ft/min (5 times GS or /2 + '0') and not 1350 ft/min (270/2 + '0') as your current text explains it. That's a 3 degree angle with the 2500 ft/min (which we are aiming for) and a 1.7 degree one with the IAS based method. Therefore, you will end up being too high when taking the IAS readout as reference.


To windplayer's and Pina's post. I must admit that I have a ton of respect for the guys really flying the dead reckoning in the sim. It can be very rewarding when the navigational instrument (stopwatch) and an aware pilot succeed on finding the right spot to land or navigate further from.  
Even more respect when flying with some rw injected weather.

I can see that I am going to have to do some descents and approaches using IAS. I, like CoolP,  have always based my rate of descent on Ground Speed and not IAS.

Mark

Well guys - seems I have some of you confused. Let me begin by explaining the first key premise of flying any aeroplane of any type:

ATTITUDE + POWER = PERFORMANCE

This means that for any given attitude (pitch angle) plus power setting you will obtain performance or outcome. This is why jets are very much a by the numbers excercise, you learn the pitch angle plus the power settings required to obtain various speeds/ROC's etc. I have a power/attitude/speed table for all the aircraft I fly as a point of reference and it is the first thing I experiment with when I get a new sim model by going through take offs level flight at various altitudes, turns and descents before I go any further to get some idea of what power and pitch attitudes are required for level flight, climbs, level turns, climbing turns, descending turns and descent and approaches, to work out what is what with each aircraft if the information is not otherwise available.

You will notice with the 707 or 727 for example the initial takeoff pitch attitude is quite high and then is decreased in increments to about say 8 degrees or less in the climb. Your ROC will vary with temperature, weight and power. You will have noticed with the 727 that the flight deck angle or pitch on final at Vat is quite high and even in level flight the aircraft is flying at a particularly higher attitude or pitch angle that a lot of say non turbine aeroplanes. In descent the actual pitch attitude is quite flat without power and it is the apparent angle from the deck that gives a different impression, so generally say like for the 727 on descent using attitude and idle power the attitude indicator is only -2 or so degrees (dependent on weight and temps)

Level flight will have a certain pitch attitude, dependent on wing design, altitude and weight and power.

What we are trying to do here is descend managing the intertia of the aeroplane plus speed, so to obtain a certain performance what do you need to vary? Attitude or power, so it follows that if you are at flight idle (or basically zero thrust), then to obtain a certain performance you need to vary the attitude or pitch angle. Better to change the attitude than to be flogging the engines up and down and burning heaps of fuel in the process, why use fuel when gravity is doing the work for you?

The 3 degree ROD process I have described so far is to allow you to use the inertia and gravity momentum of the aircraft to descend with minimum power. Naturally if the ROD increases beyond reasonable limits you will need to apply or decrease power and change the attitude, so we are using power to control speed and attitude to control ROD and we keep this process going all the way down to touchdown. At the start of descent you lower the nose first, then allow the aircraft to start descending, then bring the power back. There will be level off points where you need to let the aircraft effectively fly level for a minute or two to reduce speed, the more drag the quicker the deacceleration, 707 and 727's are quite slippery or not as draggy so will take longer to slow down, during this slow down point you may need to apply power to maintain the performance you require. You will have no doubt experienced this or recall these phases as passengers in jet transport aircraft. The key to making this all work is anticipation and being ahead of the aeroplane by knowing where your going and at what points you need to slow down and or configure the aircraft. Those points are distance and altitude.

If you try the half the IAS method to manage your ROD you will find that you do have to apply and reduce power now and then but the changes will be minimal and by the time your below 10,000 ft you will generally be using say about 60-70% N1 and as you increase drag by extending flaps and then gear then you will need more power to maintain airspeed and then only have to make minor changes in pitch attitude to control the rate of descent.

Don't worry to much about the changes in speed of IAS v TAS v GS with altitude on the way down, the ASI is correcting this automatically and you have MACH indicator as another reference,  the altitmeter distance check will smooth this out for you and help you increase or decrease the ROD required to cater for changes in winds. You can go as fast as you like as long as you don't exceed the barber pole limits for the aircraft, generally aim to keep speed just below or add barber pole indications until below about F150.

Cool IP et al, no worries, I never had the luxury of flying aircraft with advanced computer control systems and you might say I like LOU are from that era when most aircraft were developing into what they are today, that is autopilots were simple systems (like the 727 and 707 here), there were no engine control computers, no angle of attack indicators and no EFIS systems. My last flying was in a big heavy turboprop and it was very much a hybrid machine and reflected its design age. Which is why a lot of guys struggle to understand the 727 and the 707 because it takes you back to the beginning of the jet era and a lot of this sort of stuff had to be thought about by the pilot and managed properly particularly with swept wing turbine aeroplanes.

I used and taught the 3 degree profile system for years and probably because of that I am comfortable with the concepts and the need to keep it simple, after all it is really about geometry at the end of the day. I have lost count of the number of professional pilots I saw struggle with the ILS who would chase the ILS all over the place rather sticking with and understanding the basic relationship between attitude and power. Really it is about just finessing the flying by always flying an attitude first second and last. What you see on the AI is what you should see outside that is all, the trouble is that jets by and large because of the wing design, flaps etc, end up with quite high nose attitudes and when your at the end of that long lever (the fuselage) it is easy to be deluded by what your seeing as opposed to what the aeroplane is doing and showing by the instrumentation.

Anyway have a go at the method I have described, you will find with a bit of practice and it does not come automatically by the way, you will fly a lot smoother and be ahead of the aeroplane all the way, then you can really enjoy the challenges.

I might add that returning to topic about ATC, the FSX program either starts you down much to early or late and then will hang you up about half way down which makes the last descent segment really difficult, in real life ATC will be expecting you to fly the standard 3 times profile and thus not be asking you to slow down, speed up or having you stuck at a certain altitude, so it works a lot better. That is one of the reasons why I use flight following in FSX and generally forget about full ATC control as it just stuffs you around for no real good reason and you can't do things like fly a holding pattern or other manouevres as they are not programmed into FSX.

Anyway have fun.

Boeing 247 the ils interception point is always at 10nm which you will find marked on an ILS approach plate on the vertical profile for the approach shown on the bottom of the chart. Generally it is at 3000 ft AGL however there are some ILS approaches that are steeper at 4 degrees but they are catered for by giving you a glide path signal further out but these are rare. There are a lot of ILS where you intercept the glide path at 7 nm or abut 2100 -2500 feet and some further out at 13 or even 20nm at a higher altitude, generally the reasons for these approaches is do with the siting of the ILS equipment on the ground at the airport. You will note from looking at a lot of the charts that for most ILS's there is a NDB or locater beacon at the beginning of the ILS which you have to tune up using your ADF and this will give you a positive fix when you pass it if you do not have DME or it is not a co-located with the ILS and not all are. They are also very useful to track to a point to pick up the ILS but generally have a very short range of only about 20 nm.

AT 10 nm if your on the localiser the vertical beam of an ILS the vertical ILS needle and the glide path needle will be centred as well. In my flying you should be at final approach speed at this point and this point was time for gear down and minimal flap changes until past the check height shown by the maltese cross on the approach plate, flying the profile and being configured means you can make minimal attitude changes and power changes and basically slide on down the ILS to minimums.

You will note that you can pick up the localiser beam well before the glide path beam and the ILS needle will be indicating fly up or be above the centre until you hit the 10 nm point when the both centre and then you merely follow the commands indicated, needle going up means fly up, needle going down fly down, needle left go left, needle right go right. Be aware however that this all changes once you start to go past the end of the runway and fly away such as in a go around when the needle sense becomes reversed so if it indicates to the left you go right etc.

Hope this helps.

Boeing 247, your correct about not chasing the glide path and thinking about be at a steady approach attitude to intercept the ILS (localiser path and glide path or vertical and horizontal displays on the ILS gauge). The approach you posted is a little tricky but let me see if I can give you a simple explanation using the Capt Sim 727.

The ILS is 111.55 so you would set this on nav 1 and set your course indicator on the HSI to 260 degrees the ILS localiser course. As it is an ILS/DME you should get a DME readout from about 20 nm from the station or location of the Denver ILS for RWY 25. The 10,000 ft altitude shown on the plate is referenced to being at 14.8 DME (little box) and the altitude has a line underneath. The line underneath the altitude always means a 'not below altitude', you can be above 10,000 ft but never below to remain safe, so in this case you would not be below or be at 10,000ft intercepting the localiser at 14.8 DME. You would then fly in or track 260 degrees your vertical needle centred and be able to commence a descent to 8000 ft and not be below 8000 ft at that altitude until when and you do intercept the glide path (needle alive or starting to work wait until it centres on your HSI and then follow the glide path commands to continue descent on the ILS, noting again that you must not be below 7000 ft at 4.7 DME and then continue the descent to your minima on altimeter of 5552 ft or 200 ft which is the minimum height you can descend to in instrument conditions and if your not visual at that point then you go around following the published track which in this case is 260 keeping you over the runway as you climb out and your turn commences when you intercept the 306 radial from the Falcon VOR 116.3.

Looking at the chart and interpolating it would suggest the glide path will appear at about 8-10 DME or one third of the distance between 4.7 and 14.8 DME from the 111.55 Denver RWY 25 ILS.

Note that you can reference the location of the beginning of the ILS when you cross the 043 Radial of the Falcon VOR and the check height fix of 4.7 DME when you also cross the 002 Radial from the Falcon VOR and then use the same VOR to intercept the missed approach track which is the 336 radial of the Falcon VOR. This is for a localiser only no DME approach.

So here is how you would do it, you would have Denver ILS on NAV 1, HSI cursor set to 260 and Falcon VOR on NAV 2 and the indicator on the panel for NAV 2 set to the VOR setting and it will give you the picture with the needle pointing to the station and the tail of the needle moving up and the away as you cross the 043 R then the 002 R then the 306 R. You will get the standard glide path localiser indications and a dme readout in the dme counter window on the bottom left and the HSI.

So you would concentrate on the AI and HSI to fly the ILS, with a nice standard descent profile of say about 150 knots (about 750 FPM ROD)  noting the altitudes of not below 10,000 as you reach the Falcon 043R on the secondary nav display shown by the needle, the continue descending to 8000ft at which point you will get the glide path indicator begin to centre itself then continueing the descent following the glide path needle as a command instrument (fly up or down) to not below 7000 ft until you reach 4.7 DME and then continue on descending as your slowing to Vat say about 130 knots (only 650 fpm ROD) to the minima (NOTE: YOU SHOULD HAVE YOUR RAD ALT SET TO A 200 FT DH) then land or power up, gear up and then climb out as your retract the flaps if your going around.

The reason for the references to the RADIALS based on the Falcon VOR is that this is also a localiser approach and you could fly a localiser approach, that is there may be no glide path available and or your aircraft may not have DME by tracking 260 and then using the radial crossing points to positively fix your position and hence from the chart you would know your distance as for example if your on the 260 localiser and your crossing the 043 Falcon radial you can only be at 14.8 NM or the position shown on the chart. It is what is known as a positive fix or the intersection of two position lines.

As you can see they put a lot of information on these approach plates and some have a dual purpose.

If I could do videos I would put together a visual example for this approach using the Captain Sim 727 but of that process I am ignorant I am afraid.

Hope this helps you understand what is going on here for this one. As you can see it is one of the reasons in good crews and procedures you will review the approach and really study it well a good 10 minutes before the top of descent point you have it all squared away before you begin the approach and you know what your doing in advance. In two pilot crews the Pilot Flying will brief the approach verbally aloud to the pilot not flying and by doing this you cross check your understanding of what the approach involves how your going to fly it and what your going to do if it all goes pear shaped at the end.

You guys *really* need to go online. FSX's ATC is nothing short of a joke 

Join IVAO or VATSIM, talk to real ATCs (well, at least real people) and enter a whole new world in simulation. After 2600 hours online, i just can't fly offline anymore 

Some are real pilots and real ATCs, so you can expect a high level of communication language and procedures and learn from it.