skelsey

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skelsey last won the day on November 26 2017

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About skelsey

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    Broadcast journalist and BAVirtual Director of Training.
  1. Of course. However, see my point above: it goes to waste if you end up with the speedbrake out all the time. You use the speedbrake because you have too much energy. The amount of energy you have is a function of height (gravitational potential energy) and speed (kinetic energy). You obtain both by converting fuel (chemical energy) in to thrust. When you close the thrust levers at top of descent you (for all intents and purposes) stop converting fuel in to kinetic energy. To maintain airspeed therefore you have to descend - converting your gravitational potential energy in to kinetic energy. If you level off without adding thrust, you are now converting your kinetic energy back in to gravitational potential and so on. As you descend, your overall energy reduces (until ultimately you stop on the runway and you have KE=0 and GPE=0). Having a slippery airframe reduces the rate at which energy is 'lost' to noise/heat/creating turbulence in the air etc. This allows you to close the thrust levers earlier and 'glide' further without additional thrust and therefore burn less fuel. However, if you stay at cruise too long you are effectively pouring more and more energy in to the system. This energy comes from burning fuel. When you start down, you realise you have too much energy so you put the speedbrakes out in order to convert some of that 'extra' energy in to noise, turbulence etc. Effectively you are throwing away all the fuel you burnt between the 'ideal' descent point and the point at which you actually started down. This is why some people make a point about speedbrake usage - because it is a fundamentally inefficient way to fly the aeroplane and if you have a choice (not always the case in the imperfect real world with ATC requirements) there are more efficient ways to manage energy which result in an overall lower fuel burn and greater passenger comfort (speedbrakes are invariably noisy and vibration-inducing). As I say, the heating analogy above is a good way to think about it, or like racing up to a red traffic light in your car and standing on the brakes at the last moment - it works, but by anticipating ahead and getting off the gas earlier you burn less fuel and give your passengers a smoother ride - get off the gas early enough and you will barely have to touch the brake at all, though this may not always be practical in busy traffic! (Of course, if you get off the gas too early you may coast to a stop before you get to the stop line, and thus have to get back on the gas again - which is also less efficient than the 'ideal' profile).
  2. Sure - and I think this might be a bit of a US/EU thing to a certain extent as I know you guys over there have some pretty aggressive STAR descent profiles and slam-dunk ATC demands which are unachievable without extra drag. Fundamentally, however, it is a question of smoothness and efficiency. Is it more efficient to turn the heating in your house on full whack, wait until you're dripping with sweat and then open all the windows to quickly cool it down, or to turn the heater on less and/or anticipate turning it off earlier so that you don't overheat and have to then throw all that energy away? As I say, I'm not disputing that the speedbrakes are there to be used if necessary -- if the question is is it better to end up high and fast on approach and go around/end up off the end of the runway or use some speedbrake and get the energy level of the aircraft under control then clearly it needs using (and generally earlier rather than later!). But in a sim with little in the way of ATC restrictions and minimal traffic levels, you can usually start down any time you want. There is no energy problem that couldn't have been solved by closing the thrust levers and starting down earlier, no matter how slippery the airframe! I know a friend who flies corporate jets (and has done for a very long time) often comments on the amount of speedbrake use when he positions on airline flights and appreciates the occasions when there isn't so much...
  3. Not especially - these days the VATSIM METARs generally update pretty much as soon as they are published (ie roughly every 30 minutes or so but exceptionally more regularly). I do however agree that whilst FR24 is useful as a guide, fundamentally one should really use the VATSIM METAR and local documentation (preferred runways etc - generally found in the AIP textual data) to determine runway in use; it's a much bigger operation to switch ends at a busy airport in real life than it is on VATSIM and so in some cases it is not unusual for RW to retain a configuration with quite a lot of tailwind etc. rather than switch. VATSIM pilots are generally very averse to any sort of tailwind and if you try and follow real life in that situation you are almost guaranted to come face to face with someone. As always, at an uncontrolled aerodrome the Rules of the Air state that you should to conform to what others are doing; in essence, by all means have a look at FR24 if it helps your planning before you get there, but ultimately one should establish what the majority of others are doing and endeavour to fit in, regardless of what is going on in real life.
  4. I quite agree!
  5. As mentioned above, the the body gear steering system relies on knowing the aircraft's ground speed in order to know when to activate/deactivate. What system provides ground speed information? ;)
  6. Not really; the issue there was more that the AFDS was in an entirely inappropriate mode (FLCH) for the phase of flight and, on top of that, the flight directors were not being followed in manual flight. FLCH is a speed-on-pitch mode with fixed (in the case of a descent, idle (generally)) thrust, so if you don't follow the FD pitch commands Bad Things happen, like not achieving the target speed. Better FMA awareness and more active monitoring in general should have caught the situation. I'm not a B777 expert but I do have access to some manuals and I do recall reading a note to the effect that the B777 exhibits neutral pitch stability and therefore certainly on a touch and go the nose requires actively flying down with forward pressure. On a normal landing however I would have expected the pitch-down effect of braking/reverse etc to assist in bringing the nose down somewhat, but I'm not sure.
  7. There are a couple of options: You could use software such as that suggested above, or alternatively something like SkyVector where you could draw a route and insert the co-ordinates directly in to the FMC LEGS page. The other thing you could do is use the FMC Place/Bearing/Distance or along-track waypoint entries to draw what you want on the nav display -- so you could, for instance, having entered a route to GLESK enter something like GLESK/-5 (or however many miles). This will create a point on the track from your previous waypoint to GLESK, 5 nm before GLESK. Place/Bearing/Distance waypoints can also be used to define a waypoint based on a bearing and distance from any given point in the nav database (or, indeed, from a pseudo-waypoint such as an along-track waypoint or even another PBD waypoint). For instance, if you wanted to create a waypoint that was 10NM from GLESK on a bearing of 090 degrees, you could enter GLESK090/10 (if I recall the Boeing FMC format correctly -- you may wish to check that in the manual!). Using these techniques it is possible to draw almost anything you want on the nav display for the aircraft to follow. Hope that helps!
  8. Hi Chris, Just so I know how to help best -- what exactly is your aim from the flight planning process? I know you're not bothered about spending hours and hours finding exact CFMU-validated real world routes, but it seems to me here that you're going out of your way to come up with routes as far removed from reality as possible. Is there a reason for this or is it just a pathological hatred of airways? The reason you will not find a chart with every single fix on is that it would be unusable due to the amount of clutter. Thus enroute charts generally show only the fixes relevant to enroute navigation, instrument approach charts only show the fixes relevant to that particular approach and so on. The FMC of course has to have all of these fixes in the database and technically is able to route between any of them, but I fear you are, whether in search of simplicity or something else, making this a lot more complicated than it needs to be...
  9. You are of course quite correct - Mayday would almost certainly be rather overstating it!
  10. Also worth noting that Boeing's figures on their website are, I would presume, essentially marketing... "Our 777 is lighter than ever before - 320,000 lb. (Of course, that's rounded down, with virtually no useful equipment at all on board and the lightest and most basic versions of everything but you'll find that out when you buy it...)"
  11. Just to add to Chris' post -- the reason you won't find the empty weight in the FCOM is because it is unique to every airframe. Each specific aircraft in a fleet has a separate document detailing its specific empty weight and CG datum, taking in to account the equipment fitted to that particular airframe. Periodically the airframes are re-weighed and the OEWs updated. So this is one of those things which cannot be correct or incorrect - it just is. Saying that, your VA must be using exceptionally light loads if your ZFW is consistently less than the OEW of the PMDG model -- are you sure you've not got a lbs/kgs issue going on?
  12. . Like most things, all depends on what you're used to - but I'd far rather have my instruments aligned with the aircraft axis!
  13. Unless you're departing Leipzig (or any other German airport in Class E airspace) where the German regulator has decided that EU Regulation 923/2012 requires 250 KIAS with no exceptions and a €50,000 fine if you get caught . (NB: in Class C and above there is no speed limit other than that which may be imposed by ATC). At least one B744 operator out of there is quite literally telling its crews they are generally going to need to keep some flap out until above FL100. Not a problem until you need wing anti-ice at which point if ATC are unobliging a Mayday may be required!
  14. Have you tried (re)engaging the autothrottle at all?
  15. I'm with Guillaume -- stop (turning the aircraft to position any failed engine downwind if appropriate) and deal with it there. Of course, if you have stopped at low speed for a relatively benign issue then you may well be able to taxi off again for another go (or whatever), but personally my view would be that one should always stop fully, set the parking brake and then take a moment to figure out why you have stopped and deal with any immediate actions. Only once absolutely certain it is safe would I move off again. Part of the issue with the Manchester disaster in 1985 was that the Captain elected to taxi off the runway, thus (amongst other things) delaying the evacuation (and placing the fuselage upwind of the fire). Interested to hear from others though!