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JeffEvans

A couple of "in real life" questions

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What percentage of the time is autoland used in real life? When hand-flying the landing do you leave the autothrottle on? At what point, in hand-flying the landing, do you disconnect the autopilot?Thanks in advance.

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Autoland is used in RW in real bad wx - really low visibility.In my company the crews had to practise Autoland every 90 days to keep their proficiency...re A/T I don't know....Disc. A/P between 1000 and 2000 ft when established on finalKarl-Heinz - EDDI/THF " Tempelhof "" The mother of all airports " - Sir Norman Fosterhttp://www.precisionmanuals.com/images/forum/747400.jpg


Karl-Heinz Wichmann - EDDI/THF "Tempelhof"

"The mother of all airports" - Sir Norman Foster

Now CLOSED - its a shame !

747400.jpg

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Guest jumbojock

We take the A/T out at the same time as the A/P usually. That's normally when fully configured on the glideslope and at Vref plus additions. As previoiusly stated, around 1000 ft.David "jumbojock" Robertson

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Hi,The autothrottle issue has always puzzled me, in some videos and pictures AP's are off bu AT's remain engaged, I couldn't determine if this is a company procedure, so is this only down to the pilot's discretion?

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It's company SOP - but every SOP I have come across tell crews to disconnect the auto throttle when hand flying except during departure.Rob


Rob Prest

 

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Thanks everyone. Always difficult to determine what procedures are for safety/mechanical reasons and which are purely company procedures or SOP's.

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Our company SOP is to leave the A/T engaged - to provide GA and Stall/Flap protection but de-select Speed on Finals, thus meaning that the AP does not provide any inputs and stays in the ARM mode.

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Guest shogun007

With regards to the Aotu Throttle engaged / disengaged.Our Company suggests that when hand flying an approach you disconnect the Autothrottle. The main reason for this is so you have dirrect control over the thrust. The aircraft Auto throttle quite often has some lag in its inputs. This can mean that the A/T is always chasing the Command Speed Bug, which in turn affects the aircraft attitude on approach.A good rule of thumb for this is that every 5 kts fast or slow will change your attitude by 1 degree away from the desired attitude. So 5kts fast will give you an attitude 1 degree lower than the one you need. This in turn corelates to an increase in your Rate of Descent, of approximately the Mach Number x 100ft. So on approach lets say your Mach number for a Vref of 245 kts might be .25M, this will give you an increased RoD of 250ft/min on top of the 800ft/min that you should have for a 3 degree approach.So if you are controlling the thrust then it will make for a much more stable approach at a constant angle and rate of descent.Hope this makes sense.Regards Steve Power

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Guest rellehenk

At my company we leave the autothrottle engaged during approach (MD11).

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>With regards to the Aotu Throttle engaged / disengaged.>>Our Company suggests that when hand flying an approach you>disconnect the Autothrottle. The main reason for this is so>you have dirrect control over the thrust. The aircraft Auto>throttle quite often has some lag in its inputs. This can mean>that the A/T is always chasing the Command Speed Bug, which in>turn affects the aircraft attitude on approach.>>A good rule of thumb for this is that every 5 kts fast or slow>will change your attitude by 1 degree away from the desired>attitude. So 5kts fast will give you an attitude 1 degree>lower than the one you need. This in turn corelates to an>increase in your Rate of Descent, of approximately the Mach>Number x 100ft. So on approach lets say your Mach number for a>Vref of 245 kts might be .25M, this will give you an increased>RoD of 250ft/min on top of the 800ft/min that you should have>for a 3 degree approach.>>So if you are controlling the thrust then it will make for a>much more stable approach at a constant angle and rate of>descent.>>Hope this makes sense.>>Regards Steve Power- 1) "from the desired attitude", "the one you need": Why would you chase a certain attitude? As long as you are on the GP, able to see the runway and at Vref + component??- 2) "So on approach let's say your Mach number for a Vref of 245 kts might be .25M": Your company uses mach number for approach?!Sory, I'm not a professional by far but this is the first...Rate of descent at approach is GS(Ground Speed) *5. So if Vref + component = 150kts, your descent rate = 750'/min.Anyone correct me if I'm wrong!- 3) "Vref of 243": are you flying a 747 flapless sir?- 4) "Hope this makes sense": no, but I'm always willing to learn sir!Best Regards,Bert Van Bulck

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>> Why would you chase a certain attitude? As long as you are on the >> GP, able to see the runway and at Vref + component??Generally, for a given config, the aircraft will be at a certain pitch attitude. It's how you fly when you've lost your ASI - pitch/power. :)If you fly pitch/VS, then the power will also be correct (using power to adjust VS rate), and you should be at the correct speed for the weight/config.Are ASI failures modeled? Try it! ;) Compare your approx. speed with the FS speed and see how close you are (don't cheat!). :)Best regards,Robin.

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Guest shogun007

Sorry Bert, Re the 245. It was a typo. Let's try a Vref of 145kts +5kts.Re the Mach number, no we don't use a Mach number for approach speed, it's a rule of thumb that works nicely to give you an idea of how much your Rate of Climb or Descent will change with a 1 degree pitch change. You can try it in the cruise. Say .84M, a 1 degree pitch change from the cruise attitude will result in approximately 840 ft/min Rate of climb or descent.Sorry to cause some confusion amongst the readers.Regards Steve Power

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Guest rellehenk

Use power to control airspeed and pitch to control glide path. The other way around is used in general aviation (small prop aircraft)

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Guest Ryan Briggs

Sorry, this applys for all aviation and your only half correctDuring Slow flight *flaps down High engine power* The rule is always Pitch for Speed Power for altitude, No matter Where you go in aviation, that simple Law keeps you alive, however it only applys for the Backside of the Power curve, when you get to the forward side of it its pitch for altitude Power for speed :), When you land a 747 without instruments You pitch for speed Power for altitude, it always works, and it always keeps you alive......heh

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Guest rellehenk

Sorry, but we don't do it that way. On approach with big jets: pitch for glide path, thrust for speed. Imagine when you fly an approach with the autothrottle engaged.. It will increase the power when the speed is dropping, you are not going to lower the nose if your are on glide.

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