pegruder

Now a question for the 737 Pilots!

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So I originally made this post directed at just A320 Pilots but realized I should have opened this up to be a bit more general as I'm kinda comparing scenarios across the 737 and the A320 in sim.  The question is during landing as you are about to flare and cutting power, does the 737, specifically the 737-800 seem to float alot down the runway.  I've seemed to notice, again, comparing XP with the JAR A320 (Non "study-level", as far as I know) and P3D 737-800 (PMDG, from what I hear considered study level) major differences in landing characteristics.  In P3D upon landing in the 737-800 when I cut power I seem to float alot during flare after I cut power.  This seems to hold true to most planes in P3D but the PMDG 737 is the only AC I have that I've heard be considered a study level.  When I'm in XP i tend to use the JAR A320 which I haven't heard considered study level, and landing to me feels a bit more realistic.  When flaring and cutting power there seems to be a definite change in descent rate.  The 737 I can cut power and float/gain altitude, which is nearly the complete opposite to me in the A320.  I know I'm comparing different sims AND different aircraft, just kinda curious on which is more realistic (if not both!).  Maybe it's each aircraft's unique characteristics?  Hopefully what I'm asking makes sense.  Curious on the replies!

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38 minutes ago, pegruder said:

So I originally made this post directed at just A320 Pilots but realized I should have opened this up to be a bit more general as I'm kinda comparing scenarios across the 737 and the A320 in sim.  The question is during landing as you are about to flare and cutting power, does the 737, specifically the 737-800 seem to float alot down the runway.  I've seemed to notice, again, comparing XP with the JAR A320 (Non "study-level", as far as I know) and P3D 737-800 (PMDG, from what I hear considered study level) major differences in landing characteristics.  In P3D upon landing in the 737-800 when I cut power I seem to float alot during flare after I cut power.  This seems to hold true to most planes in P3D but the PMDG 737 is the only AC I have that I've heard be considered a study level.  When I'm in XP i tend to use the JAR A320 which I haven't heard considered study level, and landing to me feels a bit more realistic.  When flaring and cutting power there seems to be a definite change in descent rate.  The 737 I can cut power and float/gain altitude, which is nearly the complete opposite to me in the A320.  I know I'm comparing different sims AND different aircraft, just kinda curious on which is more realistic (if not both!).  Maybe it's each aircraft's unique characteristics?  Hopefully what I'm asking makes sense.  Curious on the replies!

Isn't it just a matter of 'how' you flare and when you cut the power? I've done landings with the NGX in P3D that were beautifully smooth and I was floating down the runway a bit. I've also done landings which were not quite as smooth and I cut the power a little earlier for various reasons and felt the aircraft going down faster.

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The A320 is a more modern design with better aerodynamics and better high lift devices than the 737, which was of course designed many years earlier than the A320 so that's not surprising. Because of that, the A320 has a lower approach speed requirement and consequently a lower landing speed, so naturally enough that will mean you'll be at non-flying speed sooner than you would be in a 737 and it is thus less likely to float a long way with its throttles retarded. That said, the 737 on the other hand is fairly famous for floating quite a bit once it gets in ground effect, in fact it can actually be down to around 100 knots and still be well able to keep on flying. You can see this demonstrated in the accident at Schiphol of Turkish Airlines flight 1951, where at one point the aircraft was down to 83 knots on approach, it struck the ground at about 95 knots, but even at these slow speeds it remained remarkably intact and most people on board only suffered minor injuries. Such slow speeds gives you an idea of just how long those big airliners can keep on flying even when they are well under (by as much as 40 knots) the typical reference speeds for approaches.

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4 minutes ago, Canuck said:

Isn't it just a matter of 'how' you flare and when you cut the power? I've done landings with the NGX in P3D that were beautifully smooth and I was floating down the runway a bit. I've also done landings which were not quite as smooth and I cut the power a little earlier for various reasons and felt the aircraft going down faster.

I certainly could be me.  Based upon weather and other factors I'm sure it could influence how the aircraft is reacting, I just feel its more to the consistent side of float/altitude increase than continuing descent in the NGX.  Sometimes I've cut power at the 40-50 ft mark and still floated for a bit with the engines at idle.  The A320 in XP and even noticed with the default 737 in XP shell seem to show a noticeable drop in descent when cutting power.  If I cut power at 50ft in the A320 for instance I almost feel like that would be a tire blowout (although I haven't tried).

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2 minutes ago, Chock said:

The A320 is a more modern design with better aerodynamics and better high lift devices than the 737, which was of course designed many years earlier than the A320 so that's not surprising. Because of that, the A320 has a lower approach speed requirement and consequently a lower landing speed, so naturally enough that will mean you'll be at non-flying speed sooner than you would be in a 737 and it is thus less likely to float a long way with its throttles retarded. That said, the 737 on the other hand is fairly famous for floating quite a bit once it gets in ground effect, in fact it can actually be down to around 100 knots and still be well able to keep on flying. You can see this demonstrated in the accident at Schiphol of Turkish Airlines flight 1951, where at one point the aircraft was down to 83 knots on approach, it struck the ground at about 95 knots, but even at these slow speeds it remained remarkably intact and most people on board only suffered minor injuries. Such slow speeds gives you an idea of just how long those big airliners can keep on flying even when they are well under (by as much as 40 knots) the typical reference speeds for approaches.

Wow, thats insane when you think of the weight of these birds and to able to remain airborne like that!  I have certainly heard about the 737 picking up speed on descents as well, especially since I always mess up my descent planning lol!

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6 minutes ago, Chock said:

The A320 is a more modern design with better aerodynamics and better high lift devices than the 737, which was of course design many years earlier than the A320 so that's not surprising. Because of that, the A320 has a lower approach speed requirement and consequently a lower landing speed, so naturally enough that will mean you'll be at non-flying speed sooner than you would be in a 737 and it is thus less likely to float a long way with its throttles retarded. That said, the 737 on the other hand is fairly famous for floating quite a bit once it gets in ground effect, in fact it can actually be down to around 100 knots and still be well able to keep on flying. You can see this demonstrated in the accident at Schiphol of Turkish Airlines flight 1951, where at one point the aircraft was down to 83 knots on approach, it struck the ground at about 95 knots, but even at these slow speeds it remained remarkably intact and most people on board only suffered minor injuries. such slow speeds gives you an idea of just how long those big airliners can keep on flying even when they are well under (by as much as 40 knots) the typical refernce speeds.

Wouldn't that make the 737 'safer' since you're not as close to non-flying speed as in the A320?

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Just a memory to share about 737's...

Dallas Love field is/was the primary base for Southwest Airlines. The runways at KDAL are not particularly long...about 6000 ft, if i'm not mistaken.

My point is with 6000 ft, on a hot afternoon, you can't afford any floating. The SWA pilots don't mess around with trying to "grease one on". They plant the landing which is, obviously, the correct technique. Trying to grease one would get you a call from the chief pilot, I would imagine.

I'm not typed in 737's, but have watched many operations out of KDAL and have had the pleasure of riding in the jump seat into and out of this airport with SWA.

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I'm on the Airbus now, but from my 737 days, some advice:

At 500' you should be bringing the touchdown point outside even more into your scan. As you approach 200' you want that touchdown point nailed in your screen, just like in a C152. Keep scanning speed, G/S and PAPIs to ensure all is well though. As you cross the fence at 50' you should be looking completely outside, with small inputs of aileron to nail the center line and elevator to maintain your rate of descent. When you hear that call of "FIFTY" you should raise your stare from the touchdown point that is going to disappear under the nose, to 2/3 the way down the runway (I just look to the end personally), which gives you the horizon in your peripheral vision to judge your sink rate. 

Keep it descending and listen to the "FORTY", "THIRTY", "TWENTY" calls. The speed at which these occur tells you how quickly you are sinking! When you hear the "TWENTY" you should be starting the flare, as there will be a delay between you hearing it and applying the required control input to actually initiate the flare. If you leave it below the call of "TWENTY" you will probably hit the ground with too high a rate of descent. 

There are many variables, but assuming you are ON SPEED exactly as you initiate the flare, in smooth light wind conditions, then you can start to close the thrust levers as per the FCTM so that the main gear touches as they reach the back stops. One such variable is if you have carried an extra few knots; you may need to close the levers earlier, if you are a few knots slower than your Vref you may need to slightly delay closing of the thrust levers to prevent a harsh touchdown. This comes with experience. Add in crosswinds, gusty winds, lots of rain etc and it all gets a little harder still, but the same principles apply.

When the main gear touches down, swiftly apply reverse thrust to the interlocks and apply slight back pressure on the reverse levers until the interlocks release. Avoid pulling back or pushing forward on the column. FLY the nose down onto the runway (which requires a check back on the column to prevent it 'falling' onto the runway). Put the upwind aileron into wind (if required) and nail the centter line with rudder inputs. Take more than idle reverse thrust as required and/ or briefed. Disarm the autobrakes (usually by pushing the toe-brakes) before you come to a stop and pull up straight ahead on the center line unless you have briefed that you are going to steer the aircraft off on a high speed exit. Even if you have briefed this intention, ensure you are at a suitably slow ground speed before turning off the runway, as it can be deceptive looking outside, when you think you are going quite slowly, but in fact you are still doing 70kts! Ensure that when you briefed you used the landing performance figures and measured the distance from the threshold to the intended turnoff to ensure your autobrake setting is going to give you a reasonable chance of making that turnoff. I

Keep reverse thrust as taken until below 60kts. When you hear the sixty knot call, REDUCE REVERSE THRUST TO BE AT REVERSE IDLE AS YOU SLOW TO TAXI SPEED and then stow the reversers, don't (as many do), stow the reversers abruptly when they hear the 60kt call. Anyway, hope this helps. it's been a few years since I left the Boeing!
 

 

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9 hours ago, Chock said:

The A320 is a more modern design with better aerodynamics and better high lift devices than the 737, which was of course designed many years earlier than the A320 so that's not surprising. Because of that, the A320 has a lower approach speed requirement and consequently a lower landing speed, so naturally enough that will mean you'll be at non-flying speed sooner than you would be in a 737 and it is thus less likely to float a long way with its throttles retarded.

Maybe I’m reading this statement wrong but the 737NG wing has undergone many changes from the original design, it’s not the same wing as the jurassic or classic. The higher Vref of the 738 and 9 is mainly for tailstrike avoidance by establishing a given pitch attitude as opposed to using the more traditional 1.3 x Vso.  It floats because it’s usually carrying an extra margin above stall speed, not because it needs more speed to keep flying due to ancient, and inferior aerodynamics.

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1 hour ago, BrianW said:

Maybe I’m reading this statement wrong but the 737NG wing has undergone many changes from the original design, it’s not the same wing as the jurassic or classic. The higher Vref of the 738 and 9 is mainly for tailstrike avoidance by establishing a given pitch attitude as opposed to using the more traditional 1.3 x Vso.  It floats because it’s usually carrying an extra margin above stall speed, not because it needs more speed to keep flying due to ancient, and inferior aerodynamics.

This is correct - The problem with the 737NG, especially the long-bodied models, is that it lands fast. Because tail strikes are a big threat for the long, low-slung 738 and 9, approach speeds are in the 150- to 160-knot range, which is about 40 knots or more above stall speed. All that extra speed keeps the long-bodied 737s flat to avoid tail strikes, but it also causes them to skip right back in the air at initial touchdown—just a few inches. It’s just long enough for the ground-spoiler system to sense wheel spin, at which point the spoilers deploy—right now! And it’s that second plop to the ground that makes the NGs one of the more difficult airplanes to consistently land well. The A320 is certainly easier to land. 

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Interesting discussion regarding the designs of the aircraft but as far as xplane is concerned, there seems there could be a bug around ground effect where it doesn't work properly. People are complaining that as you approach and transition into ground effect it drops much quicker than it should do.

Look at this thread and check the video which seems to illustrate this.

http://forums.x-plane.org/index.php?/forums/topic/119716-landing-smoothly-in-x-plane-11/

Might be worth considering....

Chris

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4 hours ago, busdriver said:

This is correct - The problem with the 737NG, especially the long-bodied models, is that it lands fast. Because tail strikes are a big threat for the long, low-slung 738 and 9, approach speeds are in the 150- to 160-knot range, which is about 40 knots or more above stall speed. All that extra speed keeps the long-bodied 737s flat to avoid tail strikes, but it also causes them to skip right back in the air at initial touchdown—just a few inches. It’s just long enough for the ground-spoiler system to sense wheel spin, at which point the spoilers deploy—right now! And it’s that second plop to the ground that makes the NGs one of the more difficult airplanes to consistently land well. The A320 is certainly easier to land. 

This is also a matter of concern for Airbus too to some extent. It's undeniably a plus point that one can jump into an A318/319/320/321 (and even an A330) and be pretty much good to go in terms of knowing the avionics and systems, but the SOPs for those longer Airbus variants are full of dire warnings about not forgetting how much more tail overhang you have in an A321 if you've been used to greasing your stubby little A318 onto the runway like a Tiger Moth doing a three-pointer lol.

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30 minutes ago, Chock said:

This is also a matter of concern for Airbus too to some extent. It's undeniably a plus point that one can jump into an A318/319/320/321 (and even an A330) and be pretty much good to go in terms of knowing the avionics and systems, but the SOPs for those longer Airbus variants are full of dire warnings about not forgetting how much more tail overhang you have in an A321 if you've been used to greasing your stubby little A318 onto the runway like a Tiger Moth doing a three-pointer lol.

Yep, my first few attempts on my airlines sim were interesting learning the Airbus. I had more than a few tail strikes on landing! Now, almost 800 hours later, FiFi and I get along pretty well!

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I have certainly noticed the "floating effect" of the PMDG 737NGX at times, but I have also noticed a few heavy landings in my time!! It feels very realistic to me. I don't have the FSL A320 to compare it with, but the comparison to the Majestic Dash 8Q-400 is striking. That aircraft most definitely does not float during the flare :blink:

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Definitely some good information in this thread!  Should help me get better at landing these birds.  In the 737 I almost always bounce my landings and after busdriver's explanation it certainly makes sense.  

3 hours ago, tutmeister said:

Interesting discussion regarding the designs of the aircraft but as far as xplane is concerned, there seems there could be a bug around ground effect where it doesn't work properly. People are complaining that as you approach and transition into ground effect it drops much quicker than it should do.

Look at this thread and check the video which seems to illustrate this.

http://forums.x-plane.org/index.php?/forums/topic/119716-landing-smoothly-in-x-plane-11/

Might be worth considering....

Chris

This also may be part of the problem with some of the landings.  So it seems like P3d in the NGX is fairly on point to how the real bird flies.  XP might be ok to aside from this possible bug.  Can't wait to get back in the NGX in P3D v4 and start practicing again!

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