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Simulator Training for strong crosswind landings

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Simulator Training for strong crosswind landings

Old 7th Jun 2014, 23:23
  #41 (permalink)  
Join Date: Apr 2005
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Originally Posted by misd-agin
Modern Level D simulators do an excellent job of normal flying. And can be used for teaching manual flying skills. But they'll never 100% replicate flying the real airplane. A simple fact is simulators don't scare you but airplanes can kill you.

But the simulators are good enough that the first flight for newly qualified pilots is normally with a full load of passengers.

Simulators built in the last couple of years are better than 3, 5, or 10 years earlier. Flying an old level D simulator is horrible compared to a new build simulator. Is the old model good enough? Yes. Is it at the level of a new build simulator? Absolutely not.
While I completely understand and agree with most of your comment, I think the term “horrible” really should be taken as a range of “acceptability vs realism.” Of course, no simulator – at least at this point – can do all the things an airplane can do … and probably the most immediately recognizable is the “you-are-about-to-die” aspect. Although, I can say that I’ve been on-board a simulator when the building in which it was housed was directly hit by a bolt of lightning that actually shoved the simulator’s 6-axis motion system capabilities to the maximum extension in each direction and probably exceeding at least some! Scared? You bet! The sim cab stopped in about a 30 deg nose low and as close to a 90 deg left bank that could be achieved with the 54 inch jacks. First and only time I’ve had to use the escape ropes to get out of a simulator!

Originally Posted by Bergerie1
Your knowledge of level D simulators is vastly superior to mine but I share your confidence in their ability to provide good training for cross-wind landings. However, training at or after the stall is a different matter and I would very much like to hear your views on the subject.
Good question … I wish I had a solidly good answer … so until one comes along … I’ll use this one. But, I warn all readers of my propensity to use “a lot of words,” so bear with me, please.

Originally, back when training was conducted almost exclusively in airplanes (yes, there were things called “simulators” back then but they were extremely limited and provided good training but only relevant to cockpit procedures and systems operations) the idea of conducting flight training was a serious issue … particularly with larger, air transport airplanes, and most particularly with stall training.

We all know that an aerodynamic stall and recovery does not necessarily result in a spin – but most instructors had that potential stuck firmly in their memory banks – and some students were prone to grab the aileron and elevators controls and literally “kick” and hold the rudder, doing both in such a manner that would rival any gorilla’s determined grip on any tree branch! It didn’t happen often, but it didn’t take many times to prepare an instructor to do almost anything to regain control of the airplane – Right Now! Of course a spin is a spin, and recovery from spins may differ from airplane to airplane … and as you would easily understand, the larger the airplane the more … um … interesting … the experience. Instructors were prone to be very observant and very demonstrative in describing and demonstrating how to get into an approach to stall and how to recover from that condition. No one wanted to get the airplane into a stall.

Recovery from stalls in most airplanes was, as you would immediately recognize, almost always accomplished by applying the proper rudder to center the ball (zero the yaw), applying elevator controls to decrease the angle of attack (sometimes this meant a rather large control movement forward), and aileron input to put the airplane in a zero bank – all simultaneously. With a slightly (sometimes a bit more than “slightly”) nose-low attitude, the power was advanced symmetrically. The result was generally a proper and effective recovery. Well … that is essentially, if not exactly, the procedures that were to be applied to recover from any approach to stall … where an “approach to stall” was defined as the initiation of any installed warning (warning horn, warning light, or stick-shaker), or the initiation of the elevator/airframe buffet. This practice became the routine for training in an airplane– take the airplane just to the approach to stall and teach these same, correct, recovery procedures – emphasizing that anything that went beyond the simple approach to stall warning or any fully developed stall, should be responded to in exactly the same way. This was the routine for airplane training – and it did not include training to recover from fully developed stalls. When simulators were on the rise, and the clear direction the training industry was moving … toward the greater use of flight simulator … the fact that full stall training in the airplane did not include anything beyond the approach to stall, the acceptance of the use of simulators to teach recoveries from the same approaches to stall was not a huge leap – and was, for quite some time, considered to be quite adequate.

Another problem that exacerbated the situation was the fact was that engine acceleration was directly coupled to the throttle position, and there was very little simulation of airflow taken into consideration for the computed level of thrust generated by the engines. If the pilot pushed the throttles forward, the engines were programmed to produce the appropriate amount of thrust based on that throttle position, regardless of the attitude/position of the engines. Unfortunately, in some simulators, slowing to an approach to stall required an increasing pitch attitude to maintain the established deceleration rate. Even those who would accept a slight rate of descent to be generated also increased the AOA to continue to airspeed deceleration. The relative airflow that would have gone into the engine with that specific AOA was not calculated or at least was not programmed into the simulator. This situation, in combination with the edict that a “minimum loss of altitude” was expected during the recovery, resulted in “perfection oriented pilots” (and I’m sure you know the kind of pilots I mean) to want to keep that pitch attitude throughout the recovery. You and I know that an airplane with a relatively high pitch attitude or at least a relatively high AOA, will not accelerate as quickly when the power is added if the pilot maintains that attitude or that AOA as it would if the attitude or AOA is reduced. Unfortunately, because of the error in the simulator programming, the pilots using these simulators found that by holding the pitch attitude (perhaps even increasing it slightly to aid in the airspeed reduction) and simply advancing the throttles, the airspeed would increase, and regain flying speed in a relatively short time.

Unfortunately, THAT is wholly unrealistic. It was an error in the simulator programming, BUT it was what was programmed into at least some simulators. Fast forward to the ABX DC-8 crash in Narrows Virginia on December 22, 1996. The pilots on that airplane (up for a post maintenance check) attempted to do exactly what they learned in the simulator – and it cost them their lives. They refused to lower the nose, and kept attempting to “fly out of the top of the stall.” With the attitude they had, the airflow into the engine intakes and the throttle position calling for “more” simply resulted in engine compressor stalls.

Despite the publicity of this 1996 accident and the conversations regarding stall training, there wasn’t much that changed in simulators and not much that changed in the way simulators were used to teach recoveries from approaches to stall. Again, fast forward to 2009 – the Colgan Air, Dash 8-Q400, crash on February 12, 2009 in Clarence Center, New York. As a result of this accident more scrutiny was aimed at the way this crew was trained, and the realism that simulation can or cannot provide in that portion of the “flight envelope.”

There had been concerted efforts proposed and some actually begun over the last 8-12 years – but without knowing exactly what was at risk and/or what could be achieved, a whole-hearted effort (as costly as such efforts have been and are likely to be in the future) pressing forward and accelerating the efforts were difficult to achieve. So, reasonable facsimiles of such a robust effort were initiated by several organizations … two of which were the US FAA and the UK’s Royal Aeronautical Society (RAeS). Since the Colgan accident and the publicity that tragedy generated – particularly the publicity focused on the US Congress – the FAA has taken several serious steps forward – some to initiate and some to advance or increase some programs already begun, to examine simulation and it’s potentials. The same kind of discussions have been taking place at the RAeS – and there has been considerable focus directed to these and associated flight training and simulation issues. As a result, today there are several on-going, multi-corporation efforts underway that are looking specifically at how simulators can and/or should be used to train for airplane situations that are at or outside of the normal flight operational envelope. Certainly, an aerodynamic stall would be considered outside of that normal envelope – but approaches to stall – where the recovery is initiated at the first indication of an approaching stall, is very likely at or approaching the boundary of that envelope – and, significantly, not beyond that boundary. The question then becomes how far past the normal envelope boundary can we go, should we go, and with what accuracy, to allow the programming of simulators? How does one gather data in an area where there is no consistency; where there are no accurate predictions; where airflow patterns are “random;” and all the rest of the issues that most pilots know in general concept … but few, very few, know what or how to go about defining, or measuring those factors, or know how to structure that data into a reasonably accurate aerodynamic model that reasonably represents an airplane and put that model into a computer-run, firmly bolted to the floor, reasonably accurate representation of a familiar airplane cockpit!

Well, thanks to the diligent efforts of some of these groups of professionals – today, I know we have at least one, and now, I understand, a second, transport category airplane simulators (the first one IS and I believe the second one is ALSO a B-737) that have an aerodynamic model installed that is accurate enough that the several test pilots (2 or 3 on the first, and likely up to 7 or 8 on the second) who have flown those simulators, have reported that the simulator performs and, critically, handles, as much like the airplane (the B-737) throughout the aerodynamic stall entry, the actual stall, and the stall recovery, as any anything they have seen. As an example of the competency of these pilots, one that I witnessed personally, when an interested observer quizzed one of these test pilots how far he had personally taken that airplane into the actual aerodynamic stall … he answered, “a 3-turn spin.”

At the moment, I am not aware of precisely where this program is and how much additional work on data gathering, data reduction, verification, and validation has yet to take place; nor am I aware of precisely how close we may be to the commercial development of such models. As I’ve indicated, here and elsewhere, I am now retired and working as a generalized flight training and simulation consultant – and therefore do not have the same connections to these programs as I have had for the last several decades – although I do retain some rather close friendships with many who are directly, intimately, up-to-their-necks, involved. We also have to determine what kind of rule or regulation would be necessary or appropriate for the incorporation of this aerodynamic model (these models – presuming there are 2) into airline simulator use – including the requirements that would, should, or could be leveled on the pilots using these simulators – if any. Presumably, if the process is as good as it appears to be … future questions might be, will there be any follow-on development of aero-models for other airplane types/models/series? Also yet to be determined is the cost of this whole package and whether or not a regulatory authority can or should mandate that airlines purchase and incorporate these aero-models into their fleet of simulators – or if there should be some kind of governmental reimbursement scheme. Also, I am not sure if there would be a restriction on the level of simulation that would be required to accept these kinds of simulation programming scenarios – however, it makes sense that the level of simulator would have to be relatively advanced.

As I said earlier … I believe we haven’t seen anything like we’re likely to see in the future with respect to the use of competent simulation – and personally, I’ve committed my efforts to do all I can to encourage all who might be interested to join the effort – to any degree – to any level that makes sense. Personally, I’d like to see colleges and universities who have active aviation programs, expand those programs to address the kinds of things that research will help resolve with respect to airplanes being satisfactorily simulated with a computer program and a good looking model/replica of the airplane cockpit. Simulation is very likely the very best thing that has or could have happened to the aviation industry – and it will need a lot of professional guidance, observance, critical evaluations, suggestions, and who knows what else to take the maximum advantage of what I think is a very bright future in this area.

I hope I’ve answered your questions … but, more so, I hope I generated a newly charged interest in this particular aspect of aviation. Thanks.
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Old 8th Jun 2014, 08:57
  #42 (permalink)  
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Many, many thanks. I am just about to go on holiday so will not be able to study what you have written until I get back. I have done many approach to stall training exercises in the real aircraft on 707s and VC10s and also CofA test flights on these and the 747, all of which involved stalls. Obviously a careful deceleration at 1kt/sec is designed both to ensure a standard measurement of the stall warning and stall speeds but also to ensure that the aircraft did not enter an uncontrolled post stall condition.

Although long retired, I have followed the industry debate on stall training, in particular the RAeS discussions and resulting papers. Much as I applaud the efforts to improve the quality of simulation along the lines you have described for the 737, I do wonder whether the money would be better spent increasing the amount and the standard of the training within the current flight envelope. I think more of the debate should be focused on ensuring that ALL flight training personnel know thoroughly (1) the problems associated with the stall on their aircraft type, (2) the limitations of the simulator they are using, and (3) the correct piloting techniques to both avoid and recover from a stall.

Please don't get me wrong. Better simulator fidelity will always be welcome, but I also think a much greater understanding of what is involved when training in this interesting area is probably of even greater importance. It is a matter of where the available money is best spent.

Many thanks again for your excellent post.
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Old 8th Jun 2014, 10:36
  #43 (permalink)  
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I hope I generated a newly charged interest in this particular aspect of aviation
Flying school CFI's who read PPRuNe forums would be wise to carefully consider your comments. I believe they are applicable to not only jet transport simulators but synthetic training devices found in many flying schools. I am surprised that more use of these devices is not being made for ab-initio student pilots before they go for their first serious dual instructional flight. I don't include the well known TIF or trial instructional flight which introduces a would be candidate for his first feeling of flight.

Not only does a synthetic trainer allow a student to learn the names of the various instruments and levers and flight controls, it allows dual instruction to be done in a quiet room with none of the myriad distractions of a typical real flight where the racket of the engine can be nerve-wracking as is the wearing of a bulky headset with its often awkward positioning of the microphone . In the air, rapid fire ATC instructions are mostly meaningless to a student initially and even the instructor's "pattering" is frequently interrupted by the need to look outside for conflicting traffic in a training area. Air sickness may be a problem initially and that in itself can put off some students for life.

So much can be demonstrated in even a basic synthetic trainer and that includes engine starting, effects of controls right through to elementary climbing, straight and level and descending. Even basic radio procedures can be introduced in those first few sessions in the ground trainer.

Once the student steps into his first Cessna 172, Warrior or the newer trainers on the market, the distractions inevitable in real flight are soon overcome and progress towards first solo is probably halved and at far less cost to the student. Paradoxically, that may be a problem since less cost to the student means less income to the flying school instructors. Reasons will then be dreamed up why students should avoid ground trainers; the most common excuse being students would forget to look outside during real flight. Opinions will vary, of course

Last edited by Centaurus; 8th Jun 2014 at 10:50.
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Old 8th Jun 2014, 16:11
  #44 (permalink)  
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Probably because you spent more time in the aircraft than you did in the sim?

The simulator allows you work on your scan,and set up your method how to deal with a crosswind,possibly a decreasing crosswind as you go down,hence a possible quick change in track required to maintain the centerline..the requirement to focus inside and outside....
The feel of the pants i believe is only a benefitial aid during low visibility,poor lighted runways manual landings...the rest is all about scan,looking outside including for the flare (pitch up),rudder input to straight up the nose and sink rate the rate at which one should decrease the thrust...
A croswind requires in general a longer landing distance as the pilot decrabs and the thrust stays in a tad longer...
I know how to do xwind landings. I've been flying being paid for 11 years and although I learn every day, I know I am (was) proficient in xwind landings up to and including 38kts, as was the limit on my last type.
However all that experience and skill has not helped me make 1 decent xwind landing in any sim, on any type, or any sim. After every type qualification I dreaded my first landing, fortunately until now unnecessary.
Could it be some people actually do landings different than others? While some can see how and what to do, others feel it?
I really am not joking, I can't land the sim and had problems on earlier types too.

While the various posts indicate some concern about the validity (fidelity) of simulators in crosswind landings, maybe they are better than the alternative ie nothing. Can you just imagine the OMG reactions of the captive audience down the back when a MPL cadet pilot is given his first 30 knot crosswind landing in the real aircraft without the benefit of previous simulator training to get the technique right? He may be nothing more than the captain's apprentice yet he is legally second in command.
While I will not disagree with "some is better than none", I am glad my company enforces the rule no xwind >15kts the first year.
While the sim might teach you the actions (which you already should know), line flying will teach you the skill, or at least it was that way with me, every time on every type.
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Old 8th Jun 2014, 16:20
  #45 (permalink)  
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Bergerie1 and Centaurus

I probably should not be surprised that the 2 of you posted very similar comments in response to my rather “wordy” post. BOTH of you are right on target!! As I’ve said many times on this forum and in my regular discussions with members of the industry with whom I regularly interact … simulation is a tool … a very valuable tool to be sure … but a tool nonetheless. And like any tool, the user of that tool should be trained to know how to use it, what its capabilities and limitations are, and how best to take advantage of those capabilities and how to face, address, and compensate for its limitations. Unquestionably, one point that simply cannot be overstated and certainly cannot be ignored is that no matter the level of simulation, all simulation will have both capabilities AND limitations. And, of course, I’m not limiting my comments to using this tool for exposure to flight operations at or beyond the normal flight envelope boundaries – simulation tasks conducted well within the normal flight envelope do, and will continue to, demand the significant majority of training time.

Additionally, and most certainly, an increase in the amount and the quality of training within the normal envelope would prove to be valuable and I would never propose less training. Of course I am fully aware of the cost factors involved and I don’t advocate the indiscriminate increase in money thrown toward just any aspect of our industry. Any such commitment for increased funding should certainly have a very pointed target and, when and where possible, a description of the desired outcome. However, an improvement in a pilot’s understanding of any particular concept – particularly if such understanding allows that pilot to make or use better, or more applicable reasoning in their decision making and their skill levels when initiating any decision regarding airplane control in response to whatever is seen, heard, and/or felt during line operations would have significant benefit to the overall operation’s bottom line … first, in those rare times when there is a clearly identified instance that competent pilot response is necessary to prevent or to minimize the effects of any potential or actual circumstance that could or would have developed into a disaster, the value of such preparation would be easily recognized; and, second, but I think significantly, there is ALSO such benefit achieved even if the specific application of such decision making or control application cannot be specifically identified and/or measured. The thought here is that avoidance of the development of circumstances leading to a crisis may not be immediately (perhaps never) recognized, but is certainly every bit as important and beneficial.

Also, significantly, the points made by Centaurus regarding the application of simulation to basic level pilot training should not be dismissed, but should be recognized and embraced, fully. The caveat I continue to offer is two-fold: first, the accuracy of whatever is included in the simulation (even the basic “synthetic” replications described) should be championed to the greatest extent possible given budget constraints; and second, the training provided to the instructors using each piece of simulation equipment should provide complete understanding of both the capabilities and the limitations of the relevant training equipment. This instructor training should include appropriate methods and/or tasks to ensure that the student is properly trained and understands when, where, and how any simulation limitation, inaccuracy, or anomaly affects the presentation provided by that specific simulation equipment so that the student does not incorrectly believe, and therefore assimilate, an incorrect understanding that the airplane would present that same limitation, inaccuracy, or anomaly and negatively influence that student’s knowledge and understanding of the operation of the airplane being represented.

Also, I completely understand Centaurus’ concern about the potential paradox regarding instructor income … and my first “knee-jerk” would be to point out to the operators of such training facilities that any reduction in airborne training in an airplane, which certainly reduces facility revenue, is also a reduction in the direct operating cost to that facility. That reduction in direct operating cost may be used as a partial source of salary increase to instructors, who should, in turn, have to show more competency in using quality simulation equipment, as well as to cover the increased cost of such equipment. The difference that would likely continue to exist might be recouped by the attractiveness of overall reduced cost to students to acquire the desired pilot training (making the student more attractive to potential airline or airplane using companies) and thereby making the job-market more attractive and therefore generating more students seeking such jobs. My logic is that with better simulation equipment and better trained instructors using this equipment, doing so more easily and more regularly, is likely to result in better trained and therefore more competent student graduates, which, in turn, just might make graduates of such an operation more attractive to those who seek to employ persons with such quality training. And if that turns out to be true, word WILL spread and very likely attract additional students … that is providing we, as an industry, can point to the increased safety margins and competent delivery of reliable transportation services to the public.

OK … but it DOES sound good - and surely there is SOME level of legitimacy attached … right?

Last edited by AirRabbit; 8th Jun 2014 at 19:00.
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Old 9th Jun 2014, 09:35
  #46 (permalink)  
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I know how to do xwind landings. I've been flying being paid for 11 years and although I learn every day, I know I am (was) proficient in xwind landings up to and including 38kts, as was the limit on my last type.
However all that experience and skill has not helped me make 1 decent xwind landing in any sim, on any type, or any sim. After every type qualification I dreaded my first landing, fortunately until now unnecessary
The problem could be simulator fidelity. The reason why simulators should be checked by a qualified simulator test pilot during the scheduled 120 day check is to pick up any slipping from fidelity that inevitably occurs over time. And that means not just any company pilot who happens to be current on the type. The following comment is by a former Australia Regulator expert on simulator accreditation.

"For those who believe that a high grade simulator cannot correctly replicate the real aircraft I would suggest they consider how this can be and what might be a solution to fix it.
The standards set over two decades ago were clearly set out in legislation and developed into various computer programs. For a Level Five - now Level D simulator - the credits sought by the industry were to include "Zero Flight Time Training". To achieve this there were two main requirements in achieving real-world fidelity - they were: the program had to replicate data from "actual flight test" results; the other tests were subjective as to how it "felt" to an experienced and recent set of hands flying the test manoeuvres.

To achieve "sensitive hands" some Regulators required the simulator specialists to actually fly the aircraft over most, if not all, the manoeuvre parameters and in some cases, outside normally on-line limits. Examples were the low and high speed buffet margins in various configurations and different altitudes. Roll yaw couples were high on the objective and subjective test programs and especial had to pass to pass the subjective "feel good" hand flying.

In respect of the maintenance of fidelity as required by recurrent fidelity checks, it seems as time has passed the skill levels of simulator test pilots have eroded with the tasks often undertaken by current line pilots. This is not an accusation or slight on their ability .......but have they had the practice or recent experience required to ensure the subjective test actually replicate the aircraft?

I wonder how many simulator checkers have actually stalled and manoeuvred the actual aircraft to confirm the simulator replicates the aircraft. It was a surprise to me to feel and hear how a B747 - 200 300 400 performs, to mention one small corner of the envelope.
How about ground roll measurements with the various setting of Auto Brake and a check on the coaming cut off angle with all engines operating versus one inoperative with a different flap and body angle?
And have they actually done an alternate flap extension in the aircraft and how about an emergency gear extension?

Accreditation Test Guides, now sometimes called the Qualification Test Guide, should set out all the objective data sourced from actual flight test data. It is the computer geniuses and the recent and qualified simulator test pilots who need to address each and every test (over time) and then you might find that many actually enjoy their ability to fly the simulator ...just like the aircraft."
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Old 9th Jun 2014, 10:36
  #47 (permalink)  
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Hi Centaurus,

you might find that many actually enjoy their ability to fly the simulator ...just like the aircraft.
Until we get simulators capable of very large vertical motion (60 feet), and capable of cab rotation through 360 degs - nasa.gov/facilities/vms/index.shtml, then they will never "feel" just like the aircraft.

"The Motion Base, offers unequaled range of motion, moving as much as 60 feet vertically and 40 feet horizontally. This is one key to high-fidelity simulation and makes the VMS unsurpassed at simulating aircraft during all phases of flight, including the critical phases of landing and takeoff."
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Old 9th Jun 2014, 13:33
  #48 (permalink)  
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The Motion Base, offers unequaled range of motion, moving as much as 60 feet vertically and 40 feet horizontally. This is one key to high-fidelity simulation and makes the VMS unsurpassed at simulating aircraft during all phases of flight, including the critical phases of landing and takeoff
Wanted. Quick action motion sickness pills to be made available free of charge each in briefing room.
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Old 9th Jun 2014, 14:14
  #49 (permalink)  
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Hi Judd,
Wanted. Quick action motion sickness pills....
On the contrary. I've never been sick in the aircraft, but feel horribly sick when taxiing around on the ground in the sim, because the picture doesn't agree with my senses.

That's why most of us find it more difficult to keep the sim straight on the runway - we are missing those real heading changes and lateral acceleration clues.
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Old 9th Jun 2014, 18:56
  #50 (permalink)  
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That may be because of the latency. If the visual system, the motion system and the instruments do not all respond with exactly the same latency, and in less than 120milliseconds (correct me if this figure is wrong,) the result is a sense of disorientation and sometimes motion sickness.
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Old 9th Jun 2014, 19:59
  #51 (permalink)  
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I suspect what you are experiencing is due to the characteristics of modern Wide display visual systems.

Basically your brain is expecting a three-dimensional image focused at infinity, but it's actually a two-dimensional image focused on the display optics just in front of you.

Your eye gets confused and doesn't know where to focus and this in some people induces nausea. This can be more pronounced when taxying as you tend to be looking (focusing) even closer.
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Old 9th Jun 2014, 20:30
  #52 (permalink)  
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I always tell my trainees it is a SIMULATOR not a DUPLICATOR, it will provide responses similar to real aircraft, but the last 200 feet to touchdown tends to be a little artificial, as motion and visual cues are different to the "Real World", however despite this it is possible to train for and carry out acceptable crosswind landings up to our 40 Kt. limit.
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Old 9th Jun 2014, 22:37
  #53 (permalink)  
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Probably just an admission of my own inadequacies when it comes to being perceptually on the ball ... after a few minutes in the (now old) sims, I fell into the trap of (very nearly) forgetting it was a sim and treating it (very nearly) like an aeroplane.

Admittedly the 727 was not up to that but, for my 737 endorsement - around 30 years ago - the only real differences I noticed in the aeroplane for the check to line training were

(a) it was more fun and the hosties were much better looking than the sim instructor.
(b) the visuals, certainly, were much better
(c) the aeroplane was a tad easier to fly than the sim

Sure, sims are computer driven boxes bolted to the floor.

The realism was more than adequate for me and, from such sim instructing as I have done, for most of the pilot folks ?

Surely we now are at the stage of very much diminishing returns ?

I would pose the question are we better off putting our efforts and money elsewhere in the safety and standards equation ?
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Old 10th Jun 2014, 05:12
  #54 (permalink)  
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Very informative discussion

Interesting to read about this latency issue on the visuals, as I have always perceived it.

I always feel sick taxiing if it's prolonged. And I am sure this is why sims are harder to land, because the visuals don't give all the clues as the real aircraft does. I now forget about flaring nicely in the sim, because I see it as wasted effort with only partially invalid information.

Sim instructors, and engineers etc, get enough exposure to these differences, that they don't notice it, as much as those of us who only visit twice yearly.

As far as crosswind landings go, I have always ignored Airbuses advice for landing or takeoff. Following turboprop or Boeing procedures gives a much nicer, more controlled arrival/departure. Why is it Airbus don't seem to like crossed controls?
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Old 10th Jun 2014, 05:54
  #55 (permalink)  
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I come across many pilots getting nervous before entering the simulator.
Could it be they are afraid for the latency of the visuals?
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Old 10th Jun 2014, 06:08
  #56 (permalink)  
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John T
That was my point in my post 43. A much better understanding of the strengths and limitations of the simulator by training pilots is probably needed. A simulator has its limitations and instructors need to know these, particularly with regard to stall training. There are areas where no simulator can fully reproduce the aircraft - post stall being the main one.
Having said that, they are excellent training tools. AirRabbit's lengthy posts are some of the best I have seen on the subject. Old simulators could not adequately reproduce the aircraft in ground effect. Level D simulators are very good - so long as they have been kept in good condition and are regularly checked by pilots qualified to do this, not just any training pilot.
Even when this is the case, there is still sometimes a feeling of 'disassociation', due, I think to the inevitable small latencies in the feedback to the visual.
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Old 10th Jun 2014, 10:31
  #57 (permalink)  
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A simulator has its limitations and instructors need to know these, particularly with regard to stall training.

.. and in regard to everything not in the middle of the paddock, I suggest. Behind the box is a computer and the simulation validity is limited by what the computer driving the box might be capable of. I'm somewhat out of touch with current boxes but, going back a little, the product was limited by what the sim techs could tweak within the limitations of the computing power. I guess the situation is much the same these days albeit that the computing power is far greater and the capability likewise ?

AirRabbit's lengthy posts are some of the best I have seen on the subject.

There's a good reason for that, I suggest, confident that I know who he is. I listen attentively to what he has to say on the subject.

Even when this is the case, there is still sometimes a feeling of 'disassociation', due, I think to the inevitable small latencies in the feedback to the visual.

Indeed .. I had no great trouble finding myself experiencing vertigo in the old 727 box especially taxying. Much better when the visuals were set to 0/0.
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Old 10th Jun 2014, 10:56
  #58 (permalink)  
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Airbus love crossed controls! When you apply rudder to align the aircraft with the direction of travel, the flight controls work to keep the roll rate zero with side-stick neutral. So the controls may well be crossed... what you cannot do is keep the side-stick "crossed" because that demands a continuous roll rate.
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Old 10th Jun 2014, 23:12
  #59 (permalink)  
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Bergerie1 and John T

Gentlemen – thanks for the votes of confidence from you both – I find those comments exceptionally flattering … and particularly so when I consider who made them.

Of course simulation has come an exceptionally long way in a relatively short time – as the advancements in computer issues have advanced so have the applications of many specific uses of those computer systems. Here are some quotes from the latest attempt to standardize the technical issues regarding simulators and the testing that should be performed on each and every Flight Simulation Training Device (FSTD) with the tighter tolerances applicable to the higher levels of FSTD - Level C and Level D. The comments below are relative to motion, visual, and cockpit instrument responses. Latency timing in FSTDs is expressed in terms of milliseconds (ms) where 1 ms is equal to 1 one-thousandth of a second (0.001 second).

The transport delay test has become the primary method for determining the delay introduced into the FSTD due to the time taken for the computations through the FSTD controls, host, motion and visual computer modules. The transport delay test is not dependent upon flight test data, but may require avionics computer and instrument data from the data supplier for some cases

Relative response of the visual system, cockpit/flight deck instruments and initial motion system coupled closely to provide integrated sensory cues. Visual scene changes from steady state disturbance (i.e. the start of the scan of the first video field containing different information) should occur within the system dynamic response limit of 100 milliseconds (ms). Motion onset should also occur within the system dynamic response limit of 100 ms. While motion onset should occur before the start of the scan of the first video field containing different information, it needs to occur before the end of the scan of the same video field. The test to determine compliance with these requirements should include simultaneously recording the output from the pilot’s pitch, roll and yaw controllers, the output from the accelerometer attached to the motion system platform located at an acceptable location near the pilots’ seats, the output signal to the visual system display (including visual system analogue delays) and the output signal to the pilot’s attitude indicator or an equivalent test approved by the NAA.

FSTD response time — Motion. The FSTD response time for motion will be the elapsed time in ms between the pilot control input and the first discernable motion movement recorded by the accelerometers mounted on the motion platform. The latency for the motion system will be the FSTD response time (motion) minus the airplane response time in ms. This time is subject to the test tolerance.

FSTD response time — Visual system. The FSTD response time for visual system will be the elapsed time in ms between the pilot control input and the first discernable visual change measured as appropriate for the visual system. The latency for the visual system will be the FSTD response time (visual system) minus the airplane response time in ms. This time is subject to the test tolerance.
Note.— Visual system response time is measured to the beginning of the frame in which a change occurs.

FSTD response time — Cockpit instrument. The FSTD response time for cockpit instrument will be the elapsed time in ms between the pilot control input and the first discernable change measured as appropriate on the selected cockpit instrument. The latency for the cockpit instrument will be the FSTD response time (cockpit instrument) minus the airplane response time in ms. This time is subject to the test tolerance.
There are some simulators out there where, for whatever reason, they have latencies in some aspects of their operation down into the 20 - 30 ms range. Pretty impressive.

I'll have more to say later on other points raised in this thread - but for now, I've gotta run - cheers!
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Old 11th Jun 2014, 20:44
  #60 (permalink)  
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Hi folks -- a little history … where I am quite sure that some of the “older heads” (sorry, I mean “more experienced professionals”) will, no doubt, recognize, and probably be able to offer similar, although, hopefully, not terribly diverse comments …

Early on in the development of visual system attachments to flight simulation, the Out-The-Window (OTW) imagery was decidedly “primitive.” Initially, the visual scenes were filmed during an approach to a specific airport, and then developed onto something like 50mm movie film which was projected directly in front of the simulator on a screen, and that visual scene was laterally adjusted (left/right) so that only one pilot would see the projected scene without any angular variance. Unfortunately, the other pilot would see that same visual scene at such an incorrect angle (depending on the distance between the 2 pilot seats) that this arrangement often led to the fact that flying the airplane from the not-optimized pilot’s seat was virtually impossible.

This method was soon seen to be fraught with problems – the major one being that when the film broke and was repaired – it turned out that final approach eventually became “shorter and shorter;” and the quality of the film image was eventually eroded due to the regular exposure to the bright projection light. This method evolved into the TV camera method, where the pilots actually “flew” a miniaturized television camera over what was essentially an “HO Gauge” model railroad board onto which was built a miniature airport, with runways, taxiways, and terminals – along with some surrounding features that sometimes included the edges of an adjacent town or city. The same direct projection issues were also present with this system, but the troubles with the film methods were exchanged for trouble with having pilots crash the TV camera into trees or buildings and the limitation of a maximum one 360-degree turn in either direction without necessitating a subsequent turn in the opposite direction later or run the inevitable disconnect of the cable from the camera, instantly providing a dark screen.

A break-through in the advancement of computer technology, resulted in the “CGI,” or computer generated image. A system of Cathode Ray Tube (CRT) visual displays was constructed to provide each pilot his/her own OTW display that could be viewed without any angular variance. Both pilots were seeing the identical OTW display – but the visual scene was limited to the size of the CRT screen. Not much time passed before the horizontal field of view was expanded for each pilot through adding an additional, side-mounted CRT to the left of the Captain’s primary CRT, and to the right of the FO’s primary CRT – expanding the horizontal scene for each pilot, again limited by the size of each additional CRT. Basically only night scenes were available, with some later versions providing a reasonably decent version of a dusk scene. Relatively soon thereafter, again as a result of computer technology advancement, and CRT screen advancements, the visual industry developed the ability to display full daylight scenes. However, each pilot was still limited to his/her own individual display – even expanded with the additional side-mounted CRT.

In the middle to late 1970’s, three significant specific occurrences were designed and implemented, where each was to have a significant effect on the art/science of simulation (AND simulation really IS both an ART and a SCIENCE):

The first was the development and adoption of a technical aspect of visual system presentation, called “collimation,” a word derived from the concept of "co-linear," that provides the imagery of the OTW scene viewed by the pilots to appear at a focal distance approaching infinity, where both pilots (seated side-by-side) are able to view the visual scene simultaneously without noticing any angular errors or distortions. This principle is used in Full Flight Simulators (FFS) to display imagery of the OTW scene to the pilots seated in the in the simulator when the pilot seats are properly located and adjusted.

The second, was a very serious effort to determine the degree to which the newest advancements in computer technology as applied to simulation could be seriously considered to not just supplement airplane training for pilots, but perhaps to completely replace airplane training. This official proposal was carefully considered and would be authorized strictly on the basis of adopting and successfully demonstrating the accuracy of these computer and simulation viability advancements; and if successfully implemented, would have the most significant effect on pilot training since Orville and Wilbur first tested the concept of flight. Undoubtedly, this was very likely THE most significant step, taken by a regulatory authority, with respect to pilot training and checking – and has now become a rather routine occurrence.

The third, was the development of a visual system that was to be mounted on top of the simulator cab, projecting a full color daylight, dusk, or night scene image, as desired, onto a transparent screen, also mounted on top of the simulator cab, which was to be viewed by the simulator occupants via a front mounted reflective surface (initially very tightly stretched very reflective Mylar film – later some attempts to use actual mirrors) mounted on the front of the simulator cab, so as to move with that cab, and providing the occupants of the simulator a completely unobstructed, reflective view of the back of the roof-mounted, transparent screen, and providing that scene through 150 degrees of horizontal viewing angle and almost 50 degrees of vertical viewing angle. The significance was that this reflective surface was curved, both horizontally and vertically – eventually making mirror installations exceptionally heavy, which had negative impacts on the ability of the motion system to effectively deal with the overall weight of the simulator system. However, this concept allowed cross-cockpit viewing of the entire projected visual scene for both pilots simultaneously. This breakthrough was developed by Rediffusion Simulation, at Crawly, England and their visual department in Arlington, Texas, and was first sold to an enterprising and motivated small airline in South Florida, called “Air Florida,” the same airline that later became famous, not for their foresight in simulation – but for another, much more noteworthy, though tragically negative, occurrence.

This new approach to visual system display technology eventually exploded into a rapid advancement of the type and quality of the screen onto which the scenes were projected, the reflectivity of the “mirror” surface, and the technical issues regarding weight, mounting methods, the number of visual projectors used – enabling a wider horizontal visual scene from the original 150 degrees up to what today approaches “wing tip to wing tip” horizontal and 60 degrees vertical fields of view. Because of the curvature of both the back-projected screen and the reflective surface from which the pilots are able to “see” the visual scene, and the now long-adopted collimation functions, today the OTW scene is viewed by both pilots at a distant focus (which approaches infinity) rather than at the focal distance of a screen onto which is projected that same visual scene.

Because of the fact that the benefits of the technology that makes up modern-day simulation are at least primarily focused on, and borders on being exclusively focused on, the pilots being trained or evaluated, the visual scene optics are adjusted specifically for those pilot occupants. Anyone not located at either of those pilot positions – and that includes the instructor or evaluator – may, at times, find that their inner ear (subject to the motion cues provided by the motion system) may not be completely “in-sync” with what images are transmitted from the eyes to that portion of the brain that is processing those external cues regarding position and position change – called movement or motion. Sometimes, persons on board a simulator may experience what is vertigo or motion sickness – either or both to varying degrees. While there is a reason that we have and use the word “individual,” it is, nonetheless, quite rare that a person occupying either of the pilot seats will experience any such anomaly – predicated, of course, on the fact that the simulator is producing all of those input cues designed to be provided to those pilots (i.e., motion, visual scene, and instrument response) within the established parameters outlined in the regulatory documents for qualification of that particular simulator.

As I attempted to point out in my last, hastily written, post I attempted to point out that the latency issue, while certainly important, has been able to be pushed toward a faster and faster rate of system performance such that a latency problem is not usually something that crops up frequently. Of course, malfunctions or wear, may, at times complicate the latency that is required. The current regulatory requirement in the US, according to Part 60 (presuming I have the latest, most current version – as I know there is another change that is currently working its way through the governmental bureaucracy) calls for a latency of not more than 150 ms for Level C and D simulators – where, as I pointed out, the latest simulator standards document published by ICAO (their Document 9625) the identical language contained in the FAA regulation for its description, the latency value for motion, visual, and instrument response is shown to be not more than 100 ms. However, as I’ve indicated, there are some simulators where aspects of latency approach 20-50 ms – that is an almost unbelievably short period of time – and there is almost no way that such latency could be recognized, even sub-conscientiously.

Last edited by AirRabbit; 11th Jun 2014 at 20:54.
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