A/T mode confusion in TOGA 744

[falcon999 24]

"Set 250, get 260 . . .and a ticket!"I was under the impression that "heavys" don't have to follow the 250knt restriction under 10K, on takeoff, because of airspeed/weight restrictions.Comments?

[Guest BAW1085]

Correct...in 744 with fuel for an Atlantic crossing min clean is in the region of 265kts.(Most)Controllers know this.DMAirbus

[Guest kame]

Dear Sam,I am not going to criticize TRC but I just wish PMDG-747 to be better. It's a very inconvenient to has been unable to look over again our discussion that get all deleted. Sincerely,Kan-ichiro FushiharaP.S. Sorry, I misspelled ploblem for problem.

[Chaos81 110]

Are you talking about your discussion that was going on in the TRC3 thread? If so, it hasn't been deleted, just locked. It's still there a few pages back.

[cowpatz 243]

Sorry bit off topic and I hate to say it DM but I think the A380 may turn out to be a lemon. I dont think for one minute it is an "electrical contractors issue" that has pushed the delivery dates back. From my reading there are some major issues to be addressed namely:Over weight.Wing strength testing did not meet requirements.Body gear steering or lack thereof.Wake turbulence category into busy airports. ie approach delays into Heathrow.The fact that some airports do not want it as the wing span is so large that most taxi ways need to be closed adjacent to the taxiing A380 so as to maintain wing tip separation. Serious congestion issue.Not meeting fuel burn specs.Of course the press rarely get anything right when reporting on aviation topics so they could be totally incorrect or partially correct. Also I dont expect Airbus to come out and say they are having problems.....bad PR. I think when they said flight testing was coming along "satisfactorily" gave a hint as to whats happening. If things were going well wouldn't it be something like "great" or "very well"?CheersSteve

[Guest D17S]

Kevin, Good follow-up. I agree that the MD

[Qavion 19]

"So the notion that THR in FLCH is somehow to do with time to target altitude is totally incorrect. This is the kind of wrong conclusion such theories based on observation can lead to."Excuse me, Kevin, but my so-called theory on FLCH is not based on any practical flying experience (I have none), but on quotes directly from Boeing Maintenance and 744 Maintenance Engineer training manuals. Here's a direct quote from the 767 BMM which I have handy, but I have seen similar quotes for the 744 elsewhere."In the Flight Level Change (FLCH) mode, the TMC controls the vertical speed so that the transition to a new altitude takes about 2 minutes subject to the EPR/N1 REF for climb, and aft limits for descent."I have seen 125 seconds quoted in one manual. I can assure you, I didn't pluck this value out of thin air.In some areas, the Boeing Maintenance Manuals go into far more detail than the manuals the average pilot has access to, so you might get a different story from the pilots at PPRuNe. However, I'll let Boeing or the manufacturer sort out this impasse ;)Cheers.Q>

[Guest D17S]

I also expect this variable rate FLCH feature is not just a 744 feature. It would sure make sense that the 767 . . . even the FMC'd 737s, would also have this feature. However the serious 767 sim doesn't have this FLCH, variable climb rate modeled. Appears to be a PMDG (and real world) exclusive. Scooooooooooooooooooooooooooorre! (Opps. Sorry, to much soccer lately.)

[Qavion 19]

"However the serious 767 sim doesn't have this FLCH, variable climb rate modeled."Pity... it was discussed during beta testing... I'm rather surprised it isn't in there. I was sure it was, but I checked it for myself. I hope the APFD system didn't regress at some point during the beta process :(Re 744 FLCH... Here's a quote from one Boeing 744 manual. "With the A/T system armed and FLCH selected, the FMC provides a constant thrust to acquire a particular vertical speed. The vertical speed that the FMC calculates is primarily a function of the magnitude of the change in altitude that is requested (difference between present altitude and MCP selected altitude).If vertical speed during FLCH climb is based on the magnitude of the climb... surely time is key. V/S = feet/minute.Re the mention of the FMC in the quote: The 744 autothrottle computer is physically located inside the Flight Management computer. The FMC doesn't have to be programmed for the FLCH function to work. The A/T has no idea how heavy the aircraft weighs, where the aircraft is going, etc.Cheers.Q>

[Guest BAW1085]

For obvious reasons I cannot go into specifics. I however can say without fear of contradiction that electrical issues are the main problem A380 productiuon is facing. On your other comments..1. Overweight ?The Airframe is built on a huge set of scales, it's very very closely monitored.2. Wake turbulence ?Same rules will apply to the 748, so whats the big deal.3. Body Gear steering ?Perhaps you could elaborate on some specific problems. Fuel Burn problems ?Do you have any alternative data that prove this.Airports declining A380 ops ?Care to name a major airport that has made public statements to that effect.We are all entitled to opinions, but before raising any technical objections I would try to get a little more info. Yes I agree the press are very rarely to be believed on these issues. A typical example I saw was an image of the flight test installation wiring bundles in the Mid deck cabin, with some caption about wiring problems. Of course they neglected to mention all the FTI wiring is removed after the FT phase..!! and the image was completely unrepresentative.RegardsDM

[falcon999 24]

Wow... way OTS... thanks for the response concerning the 250knts under 10K DM.

[cowpatz 243]

1. Overweight ?See Aero-news.net http://www.aero-news.net/index.cfm?Content...9d-984b37bdcae82. Wake turbulence ?>Same rules will apply to the 748, so whats the big deal.Where did you hear that? My understanding is the pax version will be normal category but freighter version might be higher. You are looking at 550 sseater v's a 450 (not much more than current 747). The big deal is the A380 is having double the wake category applied. There are no firm orders for the pax version of the 748 yet anyway. The freighter is a different story but then it can be scheduled for arrival times outside peaks.3. Body Gear steering ?>Perhaps you could elaborate on some specific problems. Chewing up tarmac. In all fairness this may be to test body gear steering system failure on push back. Does it have body gear steering?See attachments.>Fuel Burn problems ?>Do you have any alternative data that prove this.Not data. The A380 has the worst CASM of any current airliner and also has noise problems.See: http://www.nytimes.com/2006/06/15/business...=rssnyt&emc=rss>>Airports declining A380 ops ?>>Care to name a major airport that has made public statements>to that effect.Only 4 US citys have committed to accommodating the A380. KLAX is debatable because the other airport operators are not interested in paying out to accommodate it. Rumour has it that if it ever makes it into KLAX it will have to embark/diembark at a remote gate....and that means buses and huge delays. http://www.team4news.com/Global/story.asp?S=2936364>We are all entitled to opinions, but before raising any>technical objections I would try to get a little more info.>Yes I agree the press are very rarely to be believed on these>issues. A typical example I saw was an image of the flight>test installation wiring bundles in the Mid deck cabin, with>some caption about wiring problems. >>Of course they neglected to mention all the FTI wiring is>removed after the FT phase..!! and the image was completely>unrepresentative.Didn't see that one but I could well imagine.Yes we are all entitled to our opinions and I stated mine. There are many aviation commentators that are speculating that this aircraft could be a real problem child for Airbus even cripple them financially (although I doubt that). Aircraft builders only put back delivery schedules for serious issues. Airbus have done this twice. To me that signals problems. We are not all able to gain access to technical information so the next best thing is the media and dedicated forums and of course the information from these should only be taken at face value. The issues I raised seem to have come from many quarters and where there is smoke there is generally fire. I notice that you offer no data to dispell any of the issues raised.Anyway this is off topic. My comments were intended to be tongue in cheek and not to incite a Boeing/Airbus flame war.I wish Airbus every success with the whale jet. It is an aviation milestone.Cheers Steve

[kevinh 409]

Ok, I don't have access to the manuals, otherwise I would have verified my observations there first. I was just referring to the behaviour I have seen on many occasions in a Level C 744 full flight simulator. I suppose the speed, weight and altitude change I had usually set may have meant thrust went to the climb limit fairly quickly. Using PMDG 744, I see exactly the same behaviour, which means:(a) PMDG did a good job,(:( I am not using climb parameters which would make the vertical speed control obvious (i.e. thrust stabilising at less than the CLB limit).From other training simulator experience, the 737 Classic equivalent mode (Level Change) appears to set CLB thrust at the outset. It's a much older AFCS, so less sophisticated. Again I have not read the manuals, so please don't flame me. The 757 is reportedly similar (see www.757.org.uk).The two minute time to climb for FLCH can only apply to small changes in altitude, because to achieve a large change in altitude in 2 min will inevitably mean thrust reaches the max climb limit before the calculated rate of climb is achieved. It would still make the thrust application smoother to begin with though.Following from this, I think it is fairly clear that the FMA annunciation THR simply means the A/T is controlling thrust, whereas THR REF means the A/T is setting the selected thrust mode limit.Apologies to all for doubting your sources.Kevin

[Qavion 19]

"The two minute time to climb for FLCH can only apply to small changes in altitude, because to achieve a large change in altitude in 2 min will inevitably mean thrust reaches the max climb limit before the calculated rate of climb is achieved. It would still make the thrust application smoother to begin with though"I understood that the idea behind this was for less drama (noise and acceleration) for small altitude changes... I'm not sure if it's any smoother for large altitude changes (???).Access to information on this kind of stuff has always been difficult. It's not really something I would need to know to fix an aircraft (other than be aware of this behaviour). This is why big sim time is invaluable (and a person on the inside of the FMC/APFD manufacturing company also comes in handy). :)Cheers.Q>

[Qavion 19]

Steve... a friend tried this scenario in a Cathay Pacific simulator for me.He said that the A/T switched to THR REF at 400' irrespective of derates (temp or fixed). With flaps out, the aircraft stoppped accelerating at flap speed limit minus 5. Oddly, with flaps up, the aircraft reached Vmo BUT NO OVERSPEED.I can see how, with wind gusting, it might just slip into overspeed with flaps up, hence the need for selecting another mode during climb.Your instructor's comment on THR appearing with derates makes no sense to me, but I don't know if ALL real world 744's are supposed to be the same in this area .. or if ALL 744 big sims are accurately programmed as per airline options in this area.Please feel free to try it for yourself ;)Cheers.Q>