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Guest Alias

MD11 not keeping speed

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Guest Alias

Hi,as you can see I am following the STAR to RINOS (that is the IAF) in PROF mode. The fact is that the a/c should keep 245 knots while, in reality, is slowing down without motivation:is it normal?Thanks2010223195624176copia.jpg

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Hi,as you can see I am following the STAR to RINOS (that is the IAF) in PROF mode. The fact is that the a/c should keep 245 knots while, in reality, is slowing down without motivation:is it normal?Thanks2010223195624176copia.jpg
I'm getting strange autopilot reactions like speed not holding,it goes into high speed protection then into low speed protection.Magenta readings turn into white readings without doing anything.I closed fsmeteo thinking maybe that might have thrown it off but it still happens.I have the latest service pack and I'm using fs9.David

David

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Well I seel you are o the downwind leg of the STAR and you are already at flaps 28. You shouldn't be anywhere past flaps 15 even when you are turning to final from the base leg. When you are on final you will go flaps 28, gear down, then 35. When you select flaps 28 your spedd decreases to VREF


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Im not the most technical person but you have your flaps rolled out to 28, when FMS is managing speed it will start reducing the speed, flaps 15 will bring you down to 180, flaps 28 brings you down to your vref speeds. You can control your speed by setting your IAS and then pulling the knob. Simply put the AC is not going to maintain a speed if something is stopping it.


 

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Lorenzo,if you want to maintain 245 kts just leave your flaps and slats up, you won't need them anyway at that speed. FMS SPD will then maintain the speed specified on the F-PLN page.Markus


Markus Burkhard

 

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Guest Alias
Lorenzo,if you want to maintain 245 kts just leave your flaps and slats up, you won't need them anyway at that speed. FMS SPD will then maintain the speed specified on the F-PLN page.Markus
Hi Markus,you're right, but flaps were deployed because the speed was decreasing rapidly (against any logic since at D334M it should have been 245 kt.) and the system called for them. If you see the magenta dot on the speedtape is pointing at 155 kt. that was the VREF for this landing. You say that leaving flaps up could have solved the problem? Sorry but I can't believe it, it would have triggered the speed protection instead (I suppose).

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Hi noticed that on the fms u got spd set to 171 at d353 than the next leg at d334 set to 245? so i gathered the aicraft was at right speed at this point and now its trying to get to 245 for d334


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I too guess it's mostly because of the flaps setting. My experience is that the autothrottle often has a hard time keeping the speed outside of the amber bands when the allowed speed range is narrowed by setting high flaps values. In windy situations, autothrottle fights even on a stabilized ILS autoland and I've seen the speed marker wandering well into the amber bands many times. Sometimes speed protection kicks in then.Keep speed as high as possible as long as possible, that's a basic rule for airliners. Being that far away from your destination, I wouldn't even deploy slats. Whenever the plane is brought out of the clean configuration, you can expect some limitations like not longer being able to use spoilers when flaps are out of up, or e.g. speed changes are more difficult because of drag inducing devices (gear,...), so adapting to flight situations is harder IMHO.When speed management is planned well and you can follow that plan, there's no need to prematurely leave clean configuration.Andreas


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I would guess you hit flaps 28 at or before D353M which changed target speed to VREF. As other have mentioned, F28 when rolling into final, then gear, then f35 then touchdown. You are still at 6,000feet, what do you need flaps for?


Paul Smith.

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Guest Jim888

I have learned through other MD-11 pilots, that FSINN weather and FSX weather cause speed issues. Before I could not maintain speed at altitude, this was because the OAT that was being measured was different than actual.THE FIX.Disable FSINN weather and use only the FSX weather, but be aware of the slow updates, this causes the plane to overspeed at times.

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