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cmbaviator

Not enough "nose heay" during flare ?

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Welcome to my world. I've been writing about this for years. It's not just the 747, it's all aircraft models that use the internal ESP (FSX & P3D) flight model. Flight dynamics during thrust changes and in ground effect are almost non-existent. OEI dynamics are obviously wrong too. Some developers have used external flight model to overcome this. Some others use FBW laws to induce pitch down during the flare

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It is sometimes easy to forget when engrossed in operating the PMDG B744v3 that it is only a simulation and a pretty good one at that!  Even full sized zero flight time simulators cannot accurately model the exact handling characteristics of a real aircraft.  Very large aircraft like the B747 and Airbus A380 have a lot of inertia and so it takes them longer to respond to any change of thrust, pitch etc than it would for a smaller aircraft such, as a Cessna 172 or B737.  And has already been said, any decent aircraft addon like PMDG's QOTS B744 and their latest -8 are bound to be affected by the limitations of the actual simulator platforms themselves.   

When carrying out a manual landing in the QOTS B744 the flare should be initiated at approximately 30ft above the runway; increasing the pitch attitude slightly by approx 2 degrees and then smoothly reducing the thrust to idle whilst holding the pitch attitude constant to counteract the simulated nose-down pitch tendency.  The aircraft should be flown onto the runway and not allowed to float, so don't raise the nose any further or change the trim in any way and simply allow the nosewheel to slowly settle as soon as the mainwheels touch down and the automatic spoilers deploy (don't forget to arm them on the approach!).  If you are having difficulty with the landing technique then try carrying out an automatic landing on the same (CAT III) runway, listen to the Radio Altimeter callouts and watch carefully what happens to the aircraft pitch attitude from 50ft down to the nosewheel touchdown.  It is all a question of numbers, really!

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20 minutes ago, berts said:

The aircraft should be flown onto the runway and not allowed to float, so don't raise the nose any further or change the trim in any way and simply allow the nosewheel to slowly settle as soon as the mainwheels touch down and the automatic spoilers deploy

My very first Level D experience over 20 years ago was in the 744 (in the “Eddie Allen” for those that know it).  At the time I had around 250 hours TT but in nothing bigger than a Cessna 210. There were many takeaways on that day, but the one that stands out the most was the instructor telling me to get the nose down on the first few landings. For me coming from light aircraft where you want to keep the nose off as long as you can it took conscious effort in the 744 to fly the nose down.


Brian W

KPAE

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1 hour ago, BrianW said:

My very first Level D experience over 20 years ago was in the 744 (in the “Eddie Allen” for those that know it).  At the time I had around 250 hours TT but in nothing bigger than a Cessna 210. There were many takeaways on that day, but the one that stands out the most was the instructor telling me to get the nose down on the first few landings. For me coming from light aircraft where you want to keep the nose off as long as you can it took conscious effort in the 744 to fly the nose down.

Haha - sounds familiar, but the inverse.

I always landed pretty flat in the Chickenhawk. Was nice when I finally moved to the 'nole, 310, and later the Slowtation. No excessive flare. Just kinda set the thing down.

...when I was in the 744 sim, though, I was asked if I was going to flare at all, but I think that was more the fact that I wasn't used the the sight picture of being that high up - oops.


Kyle Rodgers

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22 minutes ago, scandinavian13 said:

...when I was in the 744 sim, though, I was asked if I was going to flare at all, but I think that was more the fact that I wasn't used the the sight picture of being that high up - oops

Kyle, how embarrassing for you! 

To be perfectly honest, I bet every pilot has been there and misjudged the flare at one time or another.  And when it happens it certainly doesn't need a member of the cabin crew to come onto the Flight Deck with a watering can saying "Now you've planted it you might as well water it"  to tell you so!

Edited by berts

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I watched the entire video and the reason that he floated down the runway was due to some of the inherent design features along with the way the aircraft performance data is certified. Basically, all transport category aircraft are designed to be at 50' at Vref with the power at idle in order to land within the touchdown zone ( -250'/+500' of the aiming points ). Any effort to increase the amount of flare is undesirable...A good technique would suggest that at 100' RADALT begin to slowly and smoothly reduce thrust to idle ( Or let the ATS do it's job ) and hold the attitude you flew during the approach with a very slight increase in back pressure to arrest any slight sink developed as a result of the thrust being reduced...This should yield good CONSISTENT results WITHOUT highly undesirable /floatingballooning A BIG NO_NO in a large airplane in particular...Which is the case of the 747-800 like depicted here, SHOULD any ballooning/floating occur an immediate GO-AROUND should be initiated...Also, any thought toward "padding" your speeds is a BIG no-no, because the amount speed increase above the computed Vref/Vac creates an exponentially longer runway length to stop. Large airplanes are designed to be flown "by the numbers" for a reason...It's all about predicted performance and consistent results by the average line pilot. 

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-8 has a supercritical wing, one of the reasons it has such long-range and can fly at high Mach numbers...

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28 minutes ago, BE19Pilot said:

-8 has a supercritical wing, one of the reasons it has such long-range and can fly at high Mach numbers...

Welcome to the PMDG forums, please note their rules ask us to sign our full name on all posts.

Is the supercriticality a thing when the wing is in landing configuration?


Dan Downs KCRP

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1 hour ago, BE19Pilot said:

at 100' RADALT begin to slowly and smoothly reduce thrust to idle

😨

I can think of quite a lot of (in fact, most) transport category aeroplanes where bringing the thrust to idle at 100R would result in the main gear struts being punched through the wings.

The FCTM guidance, oddly enough, provides consistent results. If you can find a Boeing (or Airbus) manual, or a rated trainer, suggesting retarding the thrust levers at 100R I'd love to see it.

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Landing a large aircraft like the B744 is not as straightforward as BE19 suggests. Some of his points are no doubt valid for smaller aircraft, but I am reminded of the old saying that “there are as many ways of flying an aircraft as there are instructors”!

What I described earlier is a small part of the recommended landing technique adopted by most, if not all, B744 operators that I know of. There is a large difference between the B744’s wheel base and the increased cockpit height; in fact it is almost double that of the earlier generation of longhaul passenger jet aircraft such as the DC8 and B707. This means that the B744’s main gear will not touch down at the selected visual aiming point and during a typical approach its wheels will cross the runway threshold at about 50ft for all normal glidepath angles. Therefore, in order to ensure a safe threshold clearance the recommended touchdown point for the main gear should be at least 1,000ft down the runway.

As well as remembering to allow for this large difference between the gear height and the pilot’s eye path height, the aircraft’s inertia must also be taken into account on every approach; especially during the commencement of the flare. Reducing the thrust to idle at 100ft RA for a normal, stabilised approach is NOT recommended on the B744. The aircraft could easily end up landing hard as Simon suggests, or even worse landing short with the pilots kissing goodbye to the main gears (and probably their careers) as the wheels and legs depart the aircraft after hitting the runway threshold.

Edited by berts
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21 hours ago, scandinavian13 said:

when I was in the 744 sim, though, I was asked if I was going to flare at all, but I think that was more the fact that I wasn't used the the sight picture of being that high up - oops.

Kyle,

A few years back there was a freighter pilot that went from the right seat of a B707-320C to the right seat of a DC10-30F.  After doing penance on the -30F it was time to go back to the left seat on the 320C.  On this aspiring Captain's first landing with the check airman, the 320C was nearing the point where the 30F flare would start. The check airman looks over to the soon to be B707 Captain and says "Don't even think about it."

Pretty funny now, not soo much back then.  ROFL


I Earned My Spurs in Vietnam

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On 10/13/2018 at 12:08 PM, skelsey said:

I can think of quite a lot of (in fact, most) transport category aeroplanes where bringing the thrust to idle at 100R would result in the main gear struts being punched through the wings.

Looking at the quote, he does note "slowly." Which could be a reference to slowly walking it back to idle from 100 to 50, instead of relatively quickly at 50. Different techniques to serve similar purposes.

I had a bad habit of chopping throttle when I first started training, which caused a sharp nose drop. I corrected for that closer to the beginning of my flare, but the nose drop was startling to any new instructors I flew with. Over time, I began to just walk it back slowly to avoid any abrupt changes.

Cutting it back wholly at 100R? Yeah. That wouldn't be fun.

23 hours ago, Bluestar said:

A few years back there was a freighter pilot that went from the right seat of a B707-320C to the right seat of a DC10-30F.  After doing penance on the -30F it was time to go back to the left seat on the 320C.  On this aspiring Captain's first landing with the check airman, the 320C was nearing the point where the 30F flare would start. The check airman looks over to the soon to be B707 Captain and says "Don't even think about it."

Pretty funny now, not soo much back then.  ROFL

haha - funny how the context and entertainment of a story can change over time.

My buddy and I had the same instructor when we were flying Chickenhawks. In order to save a little time one day (and get out to a different destination), he flew out, and I flew back. This was the first time that I'd had anyone in the back seat who was also a pilot (student or otherwise), and I knew he'd be recording it. Flared too early, held it off too long, and plopped down on the runway pretty hard. As I found out later, the camera was being held against the ceiling of the cabin for stability. I hit so hard that his arms dropped a good bit, for a noticeable camera viewpoint change. Back when we were still in high school, I wasn't a fan of it. Given the time that has passed, and the change in skill level, I think it's pretty funny now.

...especially my unfazed flight instructor just popping the window open casually with a "right on [not an instruction, but the surfer-dude, chill "right on" said in an "okay cool" sort of way]...okay, let's bring it back to the ramp - good flights today, guys."

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Kyle Rodgers

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1 hour ago, scandinavian13 said:

Looking at the quote, he does note "slowly." Which could be a reference to slowly walking it back to idle from 100 to 50, instead of relatively quickly at 50. Different techniques to serve similar purposes.

Even 50R is pretty early to even start reducing thrust, let alone be all the way back on the idle stops and, again, most pilots I speak to are of the view that idle thrust at 50R in the real thing is likely to result in an 'arrival'. I'm not sure where the idea that the certification standards are predicated on idle thrust at 50R comes from either, because that's certainly not what Boeing recommend.

A light aircraft, of course, is very different and coming to idle 'over the fence' and effectively gliding in with airspeed reducing toward the stall warner is a more valid technique in that environment.

1 hour ago, scandinavian13 said:

I had a bad habit of chopping throttle when I first started training, which caused a sharp nose drop. I corrected for that closer to the beginning of my flare, but the nose drop was startling to any new instructors I flew with. Over time, I began to just walk it back slowly to avoid any abrupt changes.

Absolutely -- I'm fully in agreement that the thrust levers should (generally) be smoothly retarded rather than 'chopped' for exactly the reason above (as mentioned, I can't think of many MSFS models where the thrust-pitch couple is well-represented so this is one area where the sim can give a slightly misleading impression).

As Bertie says, the B747 FCTM suggests starting the flare around 30R by gently raising the nose about 2 degrees and then smoothly retarding the thrust levers to idle to reach the idle stop coincident with main gear touchdown -- this is actually pretty much identical to most if not all of Boeing's other products (with the exception of the pitch increase which I think is a bit less in the B747 compared to other types).

Important disclaimer: clearly the atmosphere is rarely idealised and thus one would naturally expect small variations to e.g. the rate at which the thrust is reduced and the exact height the flare is initiated dependent upon the prevailing conditions, but a near-70% increase in flare height (from 30R to 50R), (or a >200% increase from 30R to 100R!), is a lot.

As is so often the case, smooth, progressive and controlled inputs (whether in pitch, thrust or any other axis) generally gets a more consistent result than snapping the thrust levers shut/yanking back and hoping for the best -- I see many people fly lovely controlled approaches and then more or less shut their eyes, yank the throttle closed, pull back a bit and wait for the impact when it comes to the landing rather than continuing to fly and control the aeroplane all the way to touchdown (and, indeed, a safe taxi speed)!

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