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Nightflier101BL

Quick question on the AFS and flight director on takeoff

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I had a question regarding the flight director commands to hold V2 during my climbout. During a normal takeoff utilizing the AFS and flight director and having the Vspeeds set correctly, I want to climb out holding V2 or V2+10. Typically, if I overshoot my V2 speed by some amount, I would just hold that speed, and not pitch up to slow back down to V2. The problem is, the flight directors are commanding this pitch up to get back down to my V2 speed.In the 747, I never had this issue. It would set the speed bug and flight director at whatever speed I captured until acceleration height. Is this normal behavior for the MD-11? It's not a big issue but I would like to know if this is supposed to happen or not.Thanks in advance.Robert Williams

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Yeah, take off in the MD-11 require more attention to piloting technique than you are used to in the Queen. You want to nail the speeds, and be right on the FD cue before turning on otto. Delay turning on otto if you need to.

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I'm not using the autopilot in this scenario. I'm just referring to the flight director commands. This is the case for many takeoffs considering that the MD-11 loves to climb straight to outer space, especially when light.I always arm the AFS before takeoff to make use of the autothrottle system.

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I had a question regarding the flight director commands to hold V2 during my climbout. During a normal takeoff utilizing the AFS and flight director and having the Vspeeds set correctly, I want to climb out holding V2 or V2+10. Typically, if I overshoot my V2 speed by some amount, I would just hold that speed, and not pitch up to slow back down to V2. The problem is, the flight directors are commanding this pitch up to get back down to my V2 speed.In the 747, I never had this issue. It would set the speed bug and flight director at whatever speed I captured until acceleration height. Is this normal behavior for the MD-11? It's not a big issue but I would like to know if this is supposed to happen or not.Thanks in advance.Robert Williams
Robert,With all engines running the targetspeed and FD command is V2+10.Basically there's a good reason for this.At the acceleration altitude, the Vmin amber band will change from the TO requirement (1.2Vstall), to the enroute requirement (1.3Vstall).-FR during TO being the same as V2+10, you are able to retract flaps, when accelerating, rightaway.Flap retraction needs some extra attention on the real plane if you are also in a turn, but this does not affect this simulation (yet).Stick to a V2+10 as target is my advice.Regards,Harry

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...edit....sorry I wrote the wrong thing. I'm maintaining whatever speed a catch up with once I'm established in climb - never below V2+10. Obviously, I'm shooting for V2+10, but I'm not wanting to slow my airspeed down once I'm in a climb...as the flight director is instructing me to do.Do you mind me asking, what considerations are there involved in flap retraction in a turn? Are you familiar with the real MD-11?Robert Williams

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...edit....sorry I wrote the wrong thing. I'm maintaining whatever speed a catch up with once I'm established in climb - never below V2+10. Obviously, I'm shooting for V2+10, but I'm not wanting to slow my airspeed down once I'm in a climb...as the flight director is instructing me to do.Do you mind me asking, what considerations are there involved in flap retraction in a turn? Are you familiar with the real MD-11?Robert Williams
Robert,Fly as you like with a V2+10 as a minimum reference. But don't be afraid to raise the nose a little more.Flap and Slat retraction during turns should be delayed to FR +10 or SR +10 kts.This is because the Vmin amberband is G- load dependent in reality, indicating higher values during turns.Was type-rated on the MD11 for 11 years.Regards,Harry

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Okay then, thanks for the information. I was wanting to make sure that wasn't a critical issue if I were to pull back a little bit more and let the speed come back down to V2+10.That makes sense about the flap retraction in turns. I've always waited until at least Vmin+10 no matter the situation. The FCOM also talks about waiting until this time but didn't explain the reason.Thanks for help on this.Robert Williams

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Hi Robert, I am not sure I understand your original question. When you say the you didn't have that problem in the Queen, did you mean that you didn't overspeed or that the FD on the Queen did not call for a pitchup? I know the auto-pilot on the Queen is more forgiving about being on the correct flight path before it takes over, but I think the MD-11's is the more realistic.

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I meant that the 747 flight director did not command the increase in pitch to get my speed back down to V2+10. Say my V2+10 was 170, after I lift off and get established in my climb to AH, I end up at 190 - the 747 flight director and speed bug will instruct me to just hold that speed until AH. When I'm heavy, it's really not an issue, but in the MD-11 on short hops or lightly loaded, I tend to overshoot my target speed by a small margin. I've been holding that speed and disregarding the flight director. I was just wondering if it was normal in real-world practice to allow your airspeed to slow during your initial climb or considered dangerous. Also, if it was normal for the MD-11 to command the slow down.Robert Williams

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I was just wondering if it was normal in real-world practice to allow your airspeed to slow during your initial climb or considered dangerous. Also, if it was normal for the MD-11 to command the slow down.
From what I have gathered from actual pilots, the majority of the MD11 systems simulation is very realistic. It is not normal in real world to allow your airspeed to increase above target V2+10, therefore you are not having to slow down to target. You should be using FLEX if you are light, it makes initial climb much more comfortable.Also, I think disregarding the FD above 400-500 ft AGL is wrong. The FD becomes very useful once it is above 400-500 AGL.It takes time to get used to the relatively high pitch compared to the Queen's 8-12 deg.

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