787WannabePilot

Disc A/P @ 1000 feet for landing... tips?

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I have started disconnecting the A/P at approx 1000', rather than 500' as I was doing it before to get a bit more practice.

However, unless my weather settings are wacky, I am getting bounced all around. I use the HGS, but I find I am 'chasing the target' quite a bit.

Any advice?

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1 hour ago, 787WannabePilot said:

Any advice?

Kick the AP off even earlier to develop the stick and rudder skills necessary to accomplish what you're looking for. You're not giving yourself much time to develop those skills, which is why you're behind the plane and chasing things.

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1 hour ago, 787WannabePilot said:

I use the HGS, but I find I am 'chasing the target' quite a bit.

That is a very common problem during the learning stage.  Change your focus to the aircraft attitude symbol and move it such that you set up a trend that follows the FD circle.  This should mitigate some of the over controlling you are doing. Don't worry about keeping the circle inside the boresight all the time, the trend is more important.  A good place to disconnect A/P and A/T is when you are stabilized (flaps in landing position, speed on target), which might be anytime after FAF until 1000 AGL (you should always be stabilized by 1000)

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On your way in use the HUD and the flight path symbol to help you know where the plane is headed.

However if you are manually landing the plane, you should mostly be using the things on and around the runway as guidance to land (probably why until you see the runway, you shouldn't be in manual mode yet). You should not be following the guidance cue to tell you where to land, you should be using the runway tell you where to land.

I find the FD circle useless on approach.

Use automation to achieve a stable approach, then disconnect. Don't disconnect until after you are stable. Sometimes it takes more time, sometimes less. Usually it happens around 1500 feet, but it varies depending on conditions. For this reason the ideal time to disconnect varies.

During the approach the flight path symbol in the hud helps me generically figure out where I am headed after I disconnect.

As I get closer, the runway centerline tells me where I want to be horizontally, and the VASI lights tell me where  I want to be vertically

 As I get closer still, the runway markings help guide me in the rest of the way. Crossing the apron look up at the horizon and plant it down as you see fit depending on conditions.



 

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Typically a 737-800 is going to be about one minute and twenty seconds from touchdown when at 1,000 feet AGL, and it will have only just got the gear down a few seconds before that, when at around 1,500 feet AGL. It would typically be slowing down from about 160 knots to around 130-125 knots for coming in over the numbers, so you're not really leaving enough time to get a feel for how the thing is flying if you are tripping the autopilot off at that point, since it is right in the middle of a 30 knot deceleration. Having done so at 500 feet previously, the thing was probably already so stabilised at close to the landing speed, so that all you had to do was ride it in and flare at the right moment, but from 1,000 feet when it's still dropping from 160 knots on its extended final down to 125 knots or so for its final ride in and the gear coming down has affected the necessary throttle setting, is what is making life hard for you.

Theoretically if it is reasonably well trimmed, you shouldn't need to do that much to hold it on course and descent, but the fact that you are going to be slowing down by about 30 knots from that point to crossing the threshold means it won't just sit in the pipe without any control inputs at all like it probably would do from 500 feet when the autothrottle and autopilot has done all the work already. So that's where the problem lies; you're too late on the controls to be having a good feel for what throttle and pitch settings are necessary when taking over at 1,000 feet AGL, and without a good feel for hand flying behaviour, you'll tend to make mistakes, not critical ones, but enough to prevent a smooth transition to manual control for a nice landing. You'd be far better off taking it off autopilot at around 3,500 feet when you are just about turning for the localiser. Then you'll know what it is flying like at about 160 knots and what throttle setting is holding it there.

Concentrate on 'flying the needles' on the PFD right out from 3,500 feet, as this will give you a good idea of the trend for any descent or climb for a given pitch and throttle setting, and from that you'll see that if you arrest any trends early, you shouldn't really have to move the yoke too much at all in terms of pitch corrections and will have a good idea of what throttle setting you'll need to get to the reference landing speed. Don't try and smooth out every bump, an airliner like the 737 has a lot of momentum, thus it will ride through bumps and keep an average direction, so don't fights those bumps, just let it ride down that ILS glideslope line and use small amounts of power and pitch changes to keep it there, gradually dropping down to a stable final approach speed.

Three or four goes at that and you'll have it sussed. Oh, and don't use too much flaps unless you really need to, especially in windy conditions, that makes the power adjustments necessary to keep it on the glideslope occur over a wider range because you have to overcome the drag from the flaps.

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I normally have the aircraft stabilised by 1000ft. I find if the gear is out and the final flap setting is set, then the aircraft thrust and descent rate is pretty established and you only need to make very minor adjustments after disconnecting the AP.

 

Then i ignore instruments, bar airspeed of course, and concentrate on the  VASI and most importantly, when looking at the runway don't just focus on the piano keys, look down the whole runway, you will get a better picture of what the aircraft is doing regarding drift etc.

 

 

 

 

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Hand flying at 1000 ft is plenty of time to get a feel for the airplane.

A good rule of thumb is to be stable, configured and on vref at 1500 AGL. If you hit this target, by the time you are taking it off autopilot at 1000 feet, the airplane should be at the proper pitch and power.

From here, just make small changes. Don't over control. Small changes go a long way when your flying at 140-150 knots.

Same with thrust. You shouldn't need to go above 5% n1 changes. This will cause you to destabilize the approach which will throw everything off.

The FD is going to be moving around because it's following an ILS.

Just remember, small changes.

 

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5 hours ago, ahsmatt7 said:

A good rule of thumb is to be stable, configured and on vref at 1500 AGL.

ATC at major airports are gonna love your 737 tootling in at Vref whilst still four miles from the threshold at 1,500 feet with a big queue of airliners all at 160+ knots up your tailpipe being told to go around lol.

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Well, considering that ahsmatt7 is a real world airliner pilot, I get the feeling that he knows what he is talking about! My input here is probably pointless (since I currently fly in totally calm conditions), but I am generally on the glideslope and stabilised way before I get down to 1000 feet, so landing the plane manually from there is a piece of cake :wink:

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8 hours ago, Chock said:

ATC at major airports are gonna love your 737 tootling in at Vref whilst still four miles from the threshold at 1,500 feet with a big queue of airliners all at 160+ knots up your tailpipe being told to go around lol.

I fly King Airs and its always fun when they tell you to keep your speed up in that thing going into a major airport. But that is better than getting the "Turn right 90 degrees and climb to..." call because you are too slow. I know its your approach once cleared, but in practice it doesn't work out that way.

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8 hours ago, Chock said:

ATC at major airports are gonna love your 737 tootling in at Vref whilst still four miles from the threshold at 1,500 feet with a big queue of airliners all at 160+ knots up your tailpipe being told to go around lol.

In IMC, approach isn't going to assign a speed to maintain to a point closer in than the marker (on an ILS).  Typically,  that's at least 5nm out.  It would actually be unusual not to be slowed to roughly target speed by 4nm out.  I'm not saying it can't happen and still qualify as stable,  but it isn't typical.  Slowing at the marker is certainly not going to force a go around for following traffic unless they're too close to begin with. 

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2 hours ago, Stearmandriver said:

In IMC, approach isn't going to assign a speed to maintain to a point closer in than the marker (on an ILS).  Typically,  that's at least 5nm out.  It would actually be unusual not to be slowed to roughly target speed by 4nm out.  I'm not saying it can't happen and still qualify as stable,  but it isn't typical.  Slowing at the marker is certainly not going to force a go around for following traffic unless they're too close to begin with. 

Probably not in IMC, but that wasn't part of the OP's issue. What I can tell you is that at my local EGCC (Manchester Int'l), I'd put money on the controllers there telling you to expedite if you're at Vref when still four miles from touchdown.

Of course I know it was only a rule of thumb to be saying Vref that far out, in order to help out the OP with sussing out how to stabilise for an approach, so it's no bad thing in a sim to be suggesting that when we don't have to really concern ourselves with traffic spacing except maybe on Vatsim or some such. After all, we can do what we like in our PMDG 737s, since there really is no ATC to upset and who cares if those AI traffic airliners get sent around? so my comment was obviously a bit tongue in cheek, hence the 'lol' on the end of it which a few people appear to have missed. But joking aside, interestingly, I just tracked the speed of a Dornier 328 coming in to 23R at Manchester, with nothing behind it so no real reason to be pouring the sauce on, but even that thing was still doing 150 as it passed through 1,000 feet.

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1 hour ago, Chock said:

I'd put money on the controllers there telling you to expedite if you're at Vref when still four miles from touchdown.

They can ask all they want but when it comes down to it the aircraft behind me is their problem, not mine.

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1 minute ago, JoeDiamond said:

They can ask all they want but when it comes down to it the aircraft behind me is their problem, not mine.

Yup, that is absolutely true, it is indeed the problem of the controllers to provide adequate spacing for anything they clear for a line up, or any other steering direction for that matter, but it's probably not going to win you many friends in the tower if you don't do things in a suitably expiditious manner which fits with the general rhythm of operations.

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I take my cue from the flickdeck to sim guy, who is a real Boeing 737 pilot....4nm out, drop gear and go flaps 15, so by then one wouldn't be at Vref yet

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