SAS263

" if I don't want to see Step Climb predicted altitudes in LEGS I should enter 0 (zero) into Step Size on the PERF page?" Correct. Doing that, If you have a flight plan that includes step points that you intended to follow you can, and should, enter those as specified step points using "/FLnnnS" on the appropriate waypoint. Apparently different airlines have different SOPs on how they want to handle the whole step climb thing, but this is your sim so do what you want. You can let the FMC do its thing, you can mix that with specified step points or you can turn off the FMC prediction and only use specified climb points. Just be aware of the resulting changes in the predicted values for fuel/time @ Destination. I´ve no idea of STEP SIZE can be set to default to zero. I´ve only had time to do a quick test of mixing in specified step climbs and got mixed results. I won´t go more into them before doing more testing.

Ryan, are you talking about the predicted values for FUEL AT DEST? That´s precisely what I was saying, perhaps hidden in my wall of text I don´t know how the NGX behaves so I´m not sure what you mean with your reference to that aircraft, but I assume from your comment that there are differences? Perhaps best to leave that topic out of this thread

Jev, I´ll try to answer some things but this is a fairly complex topic. I´ll try to get back to you when I´ve had some more time looking at my books at home. However, first of all the Auto Step Climb feature should be regarded as completely separate from the FMC. The FMC should not change its behaviour on ASC being on or off. The ON/OFF switch for step climb calculations is the STEP climb size in the PERF INIT page. If you set that to zero the FMC will not do any calculations. If you set it to RVSM, 4000 or something else valid it will do step climb calculations and, very importantly, will calculate fuel burn throughout the flight as if those step climbs will be done when the FMC calculates them. In other words, if the FMC calculates that you should climb to FL370 at waypoint D the Fuel at Dest reflects that. If you delay in making that step climb you will end up burning more fuel than what is being predicted. So, if you have set everything up for FL350 with Step Size RVSM and the FMC things that you should climb to FL410 that is what you´ll see in the LEGS pages. The FMC assumes that you will make that climb immediately. If you go to the VNAV page you will see STEP TO FL410 and AT NOW (or something like that, going from memory here). The following is also from memory and may be less than 100% accurate! When you make the Step Climb you go to the CRZ page and enter the new FL there. This is how you tell VNAV what you want done. The altitudes in the LEGS pages are planning/calculations and restrictions and the FL set in CRZ is the ordered value. Then set the new FL in the MCP and push the button (I belive you can just set the new value in the MCP, push the button and this will enter into the FMC CRZ 1L field). If the aircraft is in VNAV it should now perform that climb. As you see it´s perfectly normal to see differences between the CRZ FL value (which lets VNAV know what you want it to do right now) and the calculated FL values in LEGS and VNAV STEP TO. " I would think it would screw up VNAV descent planning for there to be a 6,000 feet difference between actual cruise level and what was being displayed in the FMC." No, I don´t think so. You´d simply enter into the descent later. The problem though is that all the fuel calculations will be wrong as I previously mentioned. Therefore this is not a situation that one should leave alone. "Why is the flight computer suggesting a Step Climb to a level above the displayed Max?" Well, this is something that I want to check first. I remember reading explanations for what those OPT/MAX/RECMD FL actually mean and why they can differ in various ways, including what you´re seeing. OPT shows the optimum altitude based on gross weight and speed shown on the speed line (2L). MAX shows maximum cruise altitude based on current gross weight, engine out operation (not sure what this means), selected speed option, disregards any altitude or speed constraints and a residual climb rate of 100 ft per minute. So, my interpretation is the OPT is Optimum right now, MAX is How high can I go with a slow climb starting right now and what you see in the LEGS pages is what is doable in the future according to the FMC predictions. I´d guess that the FMC thinks that by the time you get to FL410 from the current FL350 you will have burned off enough fuel to be safe and sound there. Work calls, I´ll get back later.

STEP size only governs wether the FMC should do any step climb calculations. Think of it as an on/off switch where ON can have a number of settings. It has nothing to do with the aircraft actually performing those climbs or not. If you have a STEP size of for instance RSVM then the calculated fuel at destination is computed as if any step climbs calculated by the FMC are also done. In other words, if you have STEP size RSVM and it calculates a climb and you do not do that climb you will consume more fuel than what the FMC predicts. IMO STEP size should have no direct impact in the AUTO STEP CLIMB feature behaviour. AUTO step climbs should only take into consideration the step climbs in the LEGS page, regardless if they are calculated by the FMC or specified by the pilot by entering FL370S at a certain point. I´ve yet to try out how the PMDG 777 FMC behaves when one injects specified step points. I´m curious to see if a calculated step point is removed when a specified step point is inserted after the calculated one.

Linky to PPRUNE: http://www.pprune.org/tech-log/524114-entries-777-fmc-when-mixing-specified-step-points.html Some more procedures surface in the thread.

I posted in PPRUNE and got the answer below: "I´m having a discussion on what entries one makes in the 777 FMC when flying for instance a trans-atlantic route which has legs where the FL is set, such as NATs legs. As I understand it from Bulfers Guide any specified step points entered into the LEGS page(s) overrides the FMC calculated ones. Say that the FMC indicates a step climb at point D, but your flight plan says to make that FL later, at point E. When you enter that FL370S the calculations will use that, not the previously calculated one at D? Also, I assume you always enter something else than zero as STEP SIZE since you´ll still want the FMC to calculate for the parts of the flight that are not restricted vertically for various reasons? The argument could be that the flight plan from dispatch should be used completely and not make use of the FMCs calculations. I think that sounds wrong since the FMC mixes in measured data as opposed to the dispatch plan that only uses predicted data (wind/temp/weights etc). Bulfers guide also says somewhere that the STEP TO fields are blank when STEP SIZE is zero?" Answer: "Correct regarding inserting a step point- but there is a bulletin warning against entering steps down route at LOWER than the current cruising altitude. Step size defaults to "RVSM", meaning it looks to the next appropriate RVSM level (It used to be "ICAO"). You change that to zero when you do not intend to make any more step climbs, and FMC predictions are then based on maintaining current level." So, my take on it is that as long as step climbs, regardless of being calculated by the FMC or specified by the pilot, are to be planned/performed STEP SIZE should be set (RVSM most common). When, for whatever reason, no more step climbs of any kind are to be made, STEP SIZE = zero. Still interesting to see how the PMDG FMC handles specified step points entered before/after calculated ones.

Tony, I dug out my copy of Bulfers FMC User´s Guide (which I thoroughly recommend) and flipped through it. There is a lot of info regarding the FMC fuel calculations and it´s been a while since I looked at it. I think that you´re idea of replacing the FMC calculated step points with those from the flight plan is correct in order the get an accurate fuel plan for the flight. Note that winds are very important to enter, but I think that´s not surprising. What may be surprising is that no winds in the perf init page or RTE DATA pages means that the FMC calculates with zero winds along the route. It actually uses a mix of the current measured winds which are used to 100% near the current location, but further along the route it mixes in the entered forecast winds and at a certain point those are used to 100%. Having zero winds along the route obviously gives bad calculations. As I said the guide is a pretty hefty document. I can´t find any info on wether one should zero out the Step Size when using manually entered steps. My GUESS is that one should leave it at say RVSM and enter the steps manually. This would mean that legs where a certain FL is required (NAT) locks the calculations/fuel predictions to that, but other legs can be calculated on the fly by the FMC, letting it use the current wind data which should be better then the forecast used in the flight plan. Live values should have preference over forecast values when possible. Hope my theory makes sense Some other hints as to why Step Size should be entered (needs confirmation on how it works in the sim/IRL): On the cruise page, Step To is blank if Step Size is zero. "If a specified step point is made on a LEGS page, 1R displays the flight plan STEP TO altitude corresponding to the specified step altitude on the next lateral flight plan leg on the LEGS page which has a step to altitude." (overrides calculated step points?). There is an example in the book where the FMC calculates a step point at a point in the flight plan. By entering a specified step point further along the route, after the calculated point, the FMC will calculate fuel based on a step climb there, not the previously calculated one. Oh, VNAV does not automatically perform a step climb when the specified step point is reached. Again, lots of info and I have no idea how this is implemented in the PMDG bird. I hope I haven´t confused matters too much, and in the end we´ll have to try it out and see what happens. To summerize, my view is that a step size should be entered. Manually entered step points will override calculated ones. No clue how the auto step feature manages things, but it should use the step climbs in the LEGS page, regardless of them being calculated or entered manually.

The only one that will get away with impersonating Bruce Lee is Chuck Norris :ph34r:

Obviously I have no idea how the thing is programmed, but to me it makes sense that a setting of step climb 0 in the FMC (perf init?) overrides any auto step climb features, even when you manually enter a FL340S point. I´d guess that the auto step feature only works when the FMC calculates step climbs and you have programmed it to not calculate any, hence no auto step climb. Try doing the same thing but with RVSM/whatever instead of zero. Blank/delete the calculated step points so that the flight plan only have your manual step climb points. It seems a bit conflicting in telling the FMC to not calculate any step climbs and at the same time enter a pilot entered step climb point?

Just out of curiousity, what have you all set the trim repeat slider at in FSX? I belive I´ve read in the intro/tut that the trim change is as slow in the sim as it is in reality. I have my slider set in the middle position and the trim change is pretty far from slow for me. When setting the TO trim I really have to just make quick dabs on the buttons otherwise the change is too great, or rather, the rate of change is too(?) large. This may be the cause of some of the posters saying that they experience no change for a short time and then a rush of change.

Agree with Badfinger. I set my Alt to the initial cruise FL and don´t touch it. Come back to the computer later on and the plane/FMC/hidden wizard has done the step climb all by it self, including setting the new cruise FL in the MCP.

Ditto

I´m sure I´m bashing in an already open door, but I thought I´d remind you that you don´t need to press any keyboard keys to move the eyepoint. Simply press and hold your mouse scrollwheel and drag the view as you like, makes it very easy to look over the engine in taildraggers.I´ve no clue how this maps for those that don´t have a clickable scroll wheel though. Backspace reverts to the default eyepoint.

In addition to the advice above you could try this for the very touchdown bit. Don´t try to land, try to keep the aircraft in the air very close to the ground with trottle all the way to idle. The closer to the ground you are able to do this, the smoother the landing will be.What happens is that as your airspeed decreases yo need to pull the stick back more and more to stay level. Usually you will stall about the same time as the stick is as far back as it gets. When the aircraft stalls it will be in such an attitude (nose up) so that the two main wheels and the tail wheels touch the ground simultaneously, hence three point landing. Since you are trying to be as close to the ground as possible, the drop as you stall is minimal or at best non-existing. I´ve never flown a tricycle geared plane, but the landings I´ve sat beside the pilot have all had the stall warning just starting to sound as we landed, so I think the technique is similar.For larger taildraggers there is another technique in which you fly the airplane closer to the ground, set the two main gears and then throttle back to idle and let the aircraft settle down. Doing this is harder and introduces the risk of making a too hard landing which causes the tail to go down by its inertia. The risk is that at that moment the airspeed can be so high that the increase in angle of attack of the wings caused by the tail being "forced" down means that the plane will lift off again. This can lead to unpleasant things...

Rob, I absolutely do not take any offense from that! Your explanation is very good and doubtless of use to a lot of people. In fact, there are a number of RL pilots that forget/neglect such things with sometimes fatal results.