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clarkTX

Autothrottle stays slow after takeoff

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Hi allAfter takeoff from KAFW my ATS doesn't want to increase speed past 190kts so I can't get to slat-retract speed or beyond. I'd like to accel to 250 and I have entered that into the flight plan beginning at TTT. But as it crosses TTT (and the next waypoints) the ATS ignores the waypoint speed and stays slow.In the pic attached, you can see I'm in ATS mode, profile mode and FMS-NAV mode. The aircraft is fully auto at this time as far as I can tell. For what its worth, my SAITEK throttle is full forward at this time.You can't see the PERF page, but it says "ECON CLB" and has 347kts in its climb speed settings. Before take-off I verified the acceleration altitude was around 3700' so I'm above this.Why won't she accelerate so I can clean up slats and get going? Is the 5000' ceiling interfering with the ATS?The only other odd thing I can see in this scenario is that the first waypoint is close to airport and 90 degrees of the runway heading so I can't just go straight to it. I climb away until about 4000' before ATC lets me turn back to TTT and I noticed that the route to TTT has the "-/" (begin climb) icon. I could be that By the time I can turn back to TTT I've already reached 5k and that climb icon might have disappeared.Maybe I'm breaking the ATS logic so it can't advance past take off speed?Any help appreciated.ThanksClark

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Your display shows you're flying at a commanded speed of 192, meaning you're in the wrong Autopilot mode for what you're looking for. I suggest reading the tutorial, as it will explain in brief how to work with some of the different modes. Basically, what you need to do in cases like this is click FMS Speed.A quick read through the autopilot section of the manuals would probably help you out a lot.

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Thanks. Since 192 is white, I wondered that myself but it went from white 184 to white 192 as it passed TTT all by itself. I didn't touch anything except Autoflight once in the air.The only way I know how to command a specific speed is by the SPD knob and I have not pushed or pulled that, and that is set to 250 anyway. Is there another way I may have commanded a speed? My flight plan for TTT, NOBLY and beyond all had commanded speeds of 250 as well.I'll rerun the scenario from a save just before take-off and I'll press the ATS cancel and autopilot cancel buttons to be sure. Then I'll press Autoflight again to re-engage the ATS. I'll come back with the results and more details of the ATS messages.ThanksClarkEdit: I'll also try the FMS SPD button as you suggest. I had thought that mode was automatic but maybe not...

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So I can't duplicate this situation again so I probably just missed a step somewhere in there.ThanksClark

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Clark,Before take off you must arme FMS SPD, NAV and Profile. When spooling up the engines on your take off run at 70% N1 press Autoflight and again above 400 Ft. Then it should be in amber.Cheers,John

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Thanks John. The wrinkle is that I don't want to engage the flight plan yet (NAV and PROFILE) since ATC has only cleared me for "runway heading" to this point.What I've found out is that if you engage the autopilot in a climb with a set Altitude in the FCP, this *also* kicks the speed/thrust control into "Speed on Pitch" and defaults it to the current speed. Thus the aircraft wallows at just above v2 until you enter the desired speed into the FCP and pull the speed knob. Lesson learned: the speed number can "go white" even when you haven't touched the speed knob because your altitude commands are implicitly linked with speed/throttle. Now I know :)So, when FSX ATC says "takeoff and follow runway heading" here's what I do now:* prime the FCP controls with the runway heading, initial climb altitude and initial speed (say 235kts to get you just above slat retraction).* pull the heading knob before takeoff to prep the FD roll mode into "Heading xxx" (you can't seem to prep speed and altitude while on the ground though)* lineup and advance to takeoff thrust* follow the FD cues and climb out along runway heading* at 1500+ activate AUTOFLIGHT which will follow the pre-loaded heading xxx flight director* pull the FCP altitude and speed knobs to command the autopilot to accelerate and climb to your first SID altitude and get you to SR speed* contact departure and receive clearance to turn to your first waypoint and "resume own navigation"* now press FMS SPD, NAV, and PROFILE buttons to engage the flight plan* (optional) if the first waypoint is far off to one side and the FMS wants to go back too far to get on track, use DIR-TO to cut the corner.If anyone knows an easier way to follow ATC "fly runway heading" on autopilot by doing more prep on the ground I'd appreciate hearing it. I'm unable to pre-arm the speed or altitude into the autopilot before wheels up. Heading will preload into the flight director but you cant seem to preload speed and altitude while on the ground, so you need to pull those knobs in the air.Maybe you can quickly enter a PBD waypoint 10 miles down runway heading and then you could active NAV/PROFILE and the new plan would stay on the runway heading. Anybody do it that way?Clark

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"Maybe you can quickly enter a PBD waypoint 10 miles down runway heading and then you could active NAV/PROFILE and the new plan would stay on the runway heading. Anybody do it that way?"Actually, this method turned out to work really well. Its easy to enter a PBD ten miles down the runway heading eg (KAFW/168/10), then fly NAV/PROFILE immediately. Use "DIR-TO" to skip on to the first SID waypoint once you get permission to "resume own navigation".Well... problem solved!CheersClark

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The easiest way to do it is not to press NAV before TO, just spd and profile and autoflight at 70% N1 and above 400ft. When lining up push the heading knob and it should be Ok (or select desired heading and pull the knob).Cheers,John

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Profile and Navigation is not needed prior the Take Off run !The only thing you really need is to press Autoflight, then advance the Throttles to about 70% (throttle hold) then fully forward, you hear a clicking sound wich indicates the AT is active, then the display should switch to TO Clamp.After TO you can engage Profile and Navigation, but first after pressing Autoflight again, the AP is active.

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Profile and Navigation is not needed prior the Take Off run !
True, but the more things you can "arm" before takeoff the less you need to activate during the busy climb out. So, for me, the smoothest way to automate the climb to my 5000' SID limit along runway heading is to enter a PBD downrange, set the FCP altitude limit to 5000, speed limit 230kt, and pre-arm NAV and PROFILE all while holding short of the runway (or even earlier). Then takeoff, press just Autoflight, and the plane speeds up and levels off at 5000' straight downrange.Its a trivial difference from activating an explicit FCP speed/hdg/alt I admit but its fun to compare methods. :)Clark

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I don't mean to be that guy......actually, who am I kidding, I do, actually.You know a lot of the issues here could be fixed if you (or the collection who seem to be mystified about the AP modes here) spent a little time in the manuals reading up on the different modes. I see a few misguided ideas, and one hack-around to get the AP to do what a simple mode change could certainly accomplish. Flying a SID with custom stuff like that could actually get you in more hot water if ATC asks you to do something other than what you're expecting. If it's a vectored SID, you should be on the HDG SEL, or hand flying.In the end, it's up to you.You can certainly bleed over from one engine to the other to start them, but it's not the best course of action all things considered. Efficiency and proper operation comes with proper understanding of the airframe.Now, go. Go read, and enjoy newfound knowledge.

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Hi KyleThat's twice now you've assumed I haven't read anything and that's disappointing. At least John and Frank are trading ideas. I would be glad to hear your step by step technique to use the AP in the case where you are not heading towards your climb point if you care to share. It is precisely because ATC has given me a command that is not in the original flight plan, that I'm deviating from the docs and tutorials that all say to activate NAV and violate ATC.I don't have a copilot to work the radios so I'm trying to do both so the AP is helpful here. If you typically fly this part by hand, that's ok by me.Clark

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@BoFrost

Profile and Navigation is not needed prior the Take Off run!
If you want it manual, no. Otherwise ist should be in amber on your PFD. During TO you have your hands on the yoke, PM is monitoring.@scan13
The only difference is now that KLM uses flap 11 for TO.Also check at 4:40, they are with profile.Cheers.John

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Clark, from memory if you dont command a specific speed in the speed window or engage f s the aircraft will climb at v2 plus 20.This is also the pitch command tou have to aim for on climb out.My suggestion is to engage heading select and also select a speed in the autopilot on command mode.This way, when you are on climbout, and engage autopilot, it will follow headin select, at the speed you desire and climb to the level assigned by atc.The Animal is programmed to follow a climb profile, unless you tell it to do otherwise.The integration of the autopilot and autothrottle is a little tricky to understand, but the more you fly it, the more you will get to understand what it is trying to do.

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Hi Kyle That's twice now you've assumed I haven't read anything and that's disappointing. At least John and Frank are trading ideas. I would be glad to hear your step by step technique to use the AP in the case where you are not heading towards your climb point if you care to share. It is precisely because ATC has given me a command that is not in the original flight plan, that I'm deviating from the docs and tutorials that all say to activate NAV and violate ATC. I don't have a copilot to work the radios so I'm trying to do both so the AP is helpful here. If you typically fly this part by hand, that's ok by me. Clark
I'm not entirely sure what you'd have me assume if someone's understanding here doesn't show that they've read the manuals. That isn't to say someone is dumb, or anything of that nature, at all. Basically, if someone tells me "aircraft can never exceed 250 under 10,000', ever, ever, ever," I assume they're parroting what others have told them, instead of reaffirming that they've read that particular reg (which is misquoted in this forum hundreds of times over). So, it would follow that if I see someone is having a hard time, is confused about, or is not putting forth accurate information about the autopilot of the MD-11 that they have not fully read that section of the manuals. If that really too much of an assumption?I would have provided more information in my post, but the issue isn't that I'm assuming that you didn't read, it's that you're not taking the reading and properly applying it if you've read it. Your comment "step by step" is why I say that. There is no step by step with an autopilot, really. It has different modes that are used in different circumstances to meet different end goals. It seems like you're trying to bend the tutorial to fit every single flight, and that's not accurate. First, the tutorial assumes you're essentially ignoring ATC. Second, it also assumes you can fly the entire route from departure to destination with no hitch - no vectoring, no discontinuities, nothing other than the equivalent of VNAV or LNAV, and flights are very rarely that. The cure for this would be reading the manual again, to fully grasp the information related to AP modes.It would be improper for me to say "this is the exact step by step process by which you can set the autopilot: 1, 2, 3. Done."Instead, it is more proper for me to say "read the manual to understand the autopilot modes and it will become apparent which situations in which to use them." I'm not trying to avoid explaining them, rather I'm trying to avoid influencing your own decision making. I can climb in PROF, I can climb in V/S and I can climb in FL CH. Which one is more proper than the other? It depends. What are you trying to accomplish?I see fully why you want step by step instructions, because your error (which you also pointed out yourself) was likely in missing a step in your preparation, but step by step gets you nowhere in aviation except the expected, and the expected is only good until something unexpected happens. Your knowledge of your plane is what saves your rear at that point.I will provide the following as guidance, based on personal preference, and not what everyone must do:Vectors - always on HDG. Why? If ATC says "fly heading 190 after ELISN, vectors for the approach," ATC assumes you're going to point the nose as 190 on your nav display (or set 190 in the heading window). If you create a custom waypoint of ELISN/190/99 in order to meet that same goal, the aircraft will track 190, which means it will compensate for the wind. If everyone else flying a heading 190 and you're tracking instead, it could put you in the wrong spot in relation to the rest of the traffic.Pilot nav SIDs (no vectors at all) - on NAV. Why? Just as you mentioned: reduce workload.Initial climbout - on PROF. Why? It's optimal, and it offers protection (pitch for speed, instead of pitch for rate). Set the initial altitude in the altitude window and it'll stop automatically, to comply with ATC's restriction. PROF should also control your airspeed setting (through the FMS command), unless you manually set it in the speed window.
The only difference is now that KLM uses flap 11 for TO. Also check at 4:40, they are with profile. Cheers. John
Not sure what you're trying to show me here...

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Thanks, Will and Kyle. I finally understood that the FD/AP will briefly run Takeoff mode and will hold the runway heading without a specific heading input but setting HDG can also work.Here is the key piece of text it took me many flights and re-reads to finally see: "When the FMS PROF mode is engaged, altitude is controlled by the FMS altitude targets in PROF climb or the FMS steering commands in PROF descent." For me, this one sentence buried in hundreds of pages was huge. The PROF mode works differently in climb than in descent. In descent it's monitoring waypoints so tweaking the filght plan may make more sense; in ascent its watching the accel targets on the FMS takeoff page. Couple this with the fact the PROF mode will set the throttles to THRUST mode when climbing to the FCP altitude and now I can finally understand why the autothrottle behaves the way it does.To climb out on runway heading, all one has to do is (one method as you said Kyle) is to pre-arm PROFILE on the ground, engage autopilot at 100+ to hold the runway heading automatically, and PROFILE will takeover at 400+ and cause a "throttle up" to THRUST mode so you can clean up. You need not be on the flight plan at this time because PROFILE ascent doesn't use the waypoints, it uses raw altitude targets. It finally clicked. I let it go and it does what it claims beautifully. I thought I had tried this before and it didn't work but I must have been setting altitude explicitly, not using PROFILE. I think that leads to "speed on pitch" which is not the acceleration I wanted. I could nose over I guess and that's ok, its just not what I was looking for at that time.Heh, this plane only gets better and better. Thanks all.CheersClark

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