Setting the throttle when disengaging ATS during final approach

[CargoBull 0]

Real pilots usually disengage autopilot and autothrottle during final, touching down manually. A real authothrottle actually moves the thrustlevers so they are in the right position at that moment, and if the plane was on a stable descent in T/D configuration, it will gracefully continue the appoach until touchdown without much interaction except for the flare-out (crosswinds permitting :-))

 

But PC throttles are not moved by the ATS, and FSX does not read out whichever position the throttles have when the ATS is turned off. Hence the effective (internal) thrust setting is kind of arbitrary at that moment and usually does not correspond to the mechanical lever position even if you try to set it to the suspected "right" position before disengaging the ATS.

 

Especially when the plane feels the throttle is set too low, all kings of envelope protection algorithms kick in, and you really lose control of the plane while it fights your attempts to settle it down anyway.

 

Real flight manuals don't help here of course. How do you handle this? Other than not switching it off?

[FLEX1978 373]

On the NGX and maybe 777 PMDG does add a throttle marker or (doughnuts) as Airbus call them on the EICAS to help with matching the throttle during disconect. Unfortunately not on the MD11.

 

I should add on the MD11 standard SOP is to leave the auto throttle engaged even when hand flying the approach, pretty much the same as the 777.

 

99% of the time I always left the A/T to do the work, however I always disconnected on the 744F, my method was to disconnect in the approach around the same time the autothrottle was commanding idle thrust , that way a smooth disconnect was always guaranteed.

 

You can also get a feel of how your calibrated throttle will match the auto throttle, just fly some circuits and practice matching your throttle position and then disconnecting, after a while it becomes second nature.

 

Regards

[Don t moderate me this way 882]

I'd set the hardware lever(s) to idle before disengaging ATS.

 

It seems easier to me to adjust from low to high, using the momentum of the plane and the spool-down time of the engines. Less potential to spoil things, IMO.

[riccardo74 36]

Usually I can't complete an MD11 flight in one shot due to lack of time, so I save my flight and reload. So my slider (throttle) on joystick are not in the exact position when I engaged A/P and ATS.

 

When I am at 1000 feet I disengage ATS and A/P and LSAS, I move a bit the slider just to match the exact N1 percentage and proceed manually. At 30 feet a retard the throttle and flare smoothly till touchdown.

[FLEX1978 373]

Hey Ricardo,

 

Keep LSAS engaged!

[riccardo74 36]

Hey Ricardo,

 

Keep LSAS engaged!

Why? I always disengage it.

[FLEX1978 373]

Why? I always disengage it.

Hey,

 

LSAS is stability augmentation, it designed to assist you in manual flight, especially when you land! Keep it on

[riccardo74 36]

Ok, I'll do it sir

[tombeckett2285 7]

Why? I always disengage it.

You will also lose the speed and stall protection factors if you disable LSAS - but it is inoperative when below 150ft radio height, or above this if a particular force is applied to the control column - 2lbs rings a bell but I'm not 100%.

 

Tom Beckett

 

Sent from my iPhone using Tapatalk

[CargoBull 0]

So many replies in a short time, thanks!

 

>> SOP is to leave the auto throttle engaged even when hand flying the approach, pretty much the same as the 777.

 

Well, concerning the 777, what went wrong with the Aseana 777 landing at KSFO recently? That was OT sorry

 

Apart from that, we are in a sim. And automatic landings, or even manual landings with autothrottle are boring. I mean it's interesting to know how it works and learn and be able to operate the plane properly, but it's also like watching two chess computers play each other. What's your part in that? :-)

 

>> my method was to disconnect in the approach around the same time the autothrottle was commanding idle thrust , that way a smooth disconnect was always guaranteed.

 

"Idle" on the MD11 is like 25% N1 right? Never saw it that low in a descent. However that could be because, when going manual at the TOD or even earlier, I am too quick with the flaps. I am not a pro so I extend the flaps one more notch whenever I feel that the plane needs my help to decelerate. That way you get slow-flying "powered descents", I know. I suppose what I should rather do, even in manual flight or when flying with manual A/P settings, is follow the pink FMS speeds displayed in the PFD and the proposed flap settings in the speed tape.

 

Just talking to myself, you can see that :-) but comments are welcome.

 

>> I'd set the hardware lever(s) to idle before disengaging ATS.

 

If you don't touch the levers after disengaging ATS, the sim will continue with the last simulated setting it knew. Not with the physical setting that it reads from the sim'd  hardware. And there's the whole problem - if you then touch the levers ever so slightly, the sim wakes up and adjusts to the physical settings - which may mean that it goes from an "assumed" e.g. 60% N1 to e.g. a physical 25% in one tenth of a second. Even if you move it back up immediately, the instability begins right there.

 

I consider that behaviour a programming error. Maybe there's no actuator to move the hardware levers on your joystick or Saitek lever unit etc., but they *could* read out the physical setting and help you adjust it properly before disengaging the ATS.

 

Flying with the F2/F3 keys (decrease/increase thrust) does not have that problem because this method does not have an absolute setting. Pressing either key takes it from where the simulator thinks the setting was. But hey....

 

In conclusion, I'd go with riccardo74 and set the levers to an estimated correct physical position, then disengange ATS, then touch the levers a fraction in order to see what the plane makes of it, and then react to that.

 

* * *

 

Anyway: What about the apparent erratic behaviour of the plane when it gets a bit disturbed on its glidepath, e.g. when going to manual at 1000ft AGL with intitially mismatching thrust levers? Is it just me? Or a sim problem? Is it some kind of "envelope protection" that keeps me from touching down when the final approach gets too rough?

 

E.g. it happened that the plane, with A/P and ATS off, would refuse to go below 40% N1, refuse to go below like 160...180 KIAS, refuse to deploy spoilers, and refuse to be forced down onto the runway, with any conceivable aural warning shouting at me. How long could a real plane try to to keep the pilot from grounding it? Even a bad pilot must be given a chance before the fuel is out, and I am really good at setting them down safely after a curvy and bumpy final .....

[pschlute 37]

Idle thrust will vary with altitude. The higher you are, the higher "idle" N1 will be.

[realpilotsimpilot 11]

FLEX1978, on 07 Nov 2013 - 4:58 PM, said:

I should add on the MD11 standard SOP is to leave the auto throttle engaged even when hand flying the approach, pretty much the same as the 777.

I haven't flown MD-11 in a fair while, but my recollection was that when I tried to fly it with the A/T on through approach it would try to re-accelerate on landing roll after I applied the brakes. Maybe I was doing something wrong?

[Kerlix 99]

I haven't flown MD-11 in a fair while, but my recollection was that when I tried to fly it with the A/T on through approach it would try to re-accelerate on landing roll after I applied the brakes. Maybe I was doing something wrong?

 

 

The A/T begins to retard to idle at 50 ft radio altitude I believe. It's always functioned properly for me. 

 

I vaguely remember someone reporting the same problem that you mentioned a long time ago. Ha. Possibly it was you. But I'm pretty sure they were able to nail that down and figure out what was going on.

 

 

 

E.g. it happened that the plane, with A/P and ATS off, would refuse to go below 40% N1, refuse to go below like 160...180 KIAS, refuse to deploy spoilers, and refuse to be forced down onto the runway, with any conceivable aural warning shouting at me. How long could a real plane try to to keep the pilot from grounding it? Even a bad pilot must be given a chance before the fuel is out, and I am really good at setting them down safely after a curvy and bumpy final .....

 

That's really odd behavior. Are you sure you aren't disconnecting the A/P, then accidentally reconnecting it with an extra button/key press?

 

I've never seen anything like that. You could try re-calibrating your hardware to see if your physical throttles "idle" area isn't the same as what the sim is seeing. As long as the plane is within it's normal flight envelope, I can't imagine a plane actively trying to keep a pilot from touching down. It may scream and holler if you're doing a poor job of it, but it shouldn't keep you from touching down.

[realpilotsimpilot 11]

The A/T begins to retard to idle at 50 ft radio altitude I believe. It's always functioned properly for me.

Thanks. This could easily be a PEBKAC error, so this is an excuse to revisit the bird and wheel it out of the virtual hangar for a couple flights.

[Kerlix 99]

Thanks. This could easily be a PEBKAC error, so this is an excuse to revisit the bird and wheel it out of the virtual hangar for a couple flights.

 

 

She's such a great plane. Any excuse to take it up is a good excuse in my book haha.