Hey
lefthanddownabit Actually, while you may or may not believe it, I
do understand aerodynamic modeling. And while I’m not involved in the specifics of aero-modeling every day, I am and have been directly involved on its periphery for the last 20 years. Certainly, you are correct that coefficients are not used to “modify” the equations of motion. However, and, please feel free to correct me if I am in error, once generated and applied they certainly
do modify the outcomes of those EOM – and, though I may not have done it very well, that IS the reference I was making.
The largest difference I’ve seen between simulations limited to “look-up tables” is that at times when the simulator was “flown” outside of its flight test validated envelope (i.e., outside of the table values – often the simulator just quit flying in that part of the envelope. You should take a look at the link provided by
XPMorten to see someone else's "take" on the limitations of "look-up" tables. For example, a major US airline had an older version of the A300-600 / A310 simulator (and now I don’t remember which cockpit was actually replicated) in which a pitch-up and bank angle combination beyond a certain point would simply “hang” the simulator at that pitch/bank attitude with no control input from the pilots – and, in fact, pitch and/or bank inputs from the pilots were fruitless. In fact, something had to be done to “kick” the computer into a section of the table where values
were entered … like pressuring the downside rudder to get the nose to move more toward the horizon. Interestingly, after doing so, the simulator was again “flyable.” There is substantial suspicion that this simulation necessity lead to a very … ah … “interesting” upset event in flight that was looked into by the NTSB. One of the finger points to the guilty culprit was directly toward this particular simulator – and the maneuvering it required – incorrectly “training” the pilots who experienced the upset. Also, please know that my comments here are not based on rumor or innuendo; I have personally “flown” this particular simulator and it DID what I describe here.
On the other hand, more modern simulators use aerodynamic programs that have the ability to compute something for 360 degrees around both the lateral and longitudinal axes. Unfortunately, the only “valid” pitch and bank excursions that are validated as being “like the aircraft,” are those which have flight tested values. In these circumstances, you would not run into a simulator “hanging” at a particular point. The simulator might well perform a reasonable loop or aileron roll because the computer is
going to compute
something all the way around either axis. Of course, once outside the validated flight envelope NO ONE can attest to the simulator’s performance or handling qualities as being anything even close to the airplane the simulator is replicating. In fact, so adamant are some about this particular point that they are absolutely and vehemently AGAINST the use of simulators for training in “upset recoveries.” As anecdotal evidence, talk to any of the guys who have performed loops in B-747 simulators and aileron rolls in DC-9s and B-727’s. Simulators are wonderful tools when used in the proper manner – and just like being able to drive a nail with pipe wrench – you can do loops in a B-747 simulator – but that is not necessarily the way that particular tool was designed to be used.
Hey
john_tullamarine: Your point is very well taken, and has formed the substance for my on-going campaign described in my earlier post:
I have been on a campaign for a number of years to have manufacturers of certain training equipment (CAE and FlightSafety come to mind immediately) that represent the cockpit of a given aircraft in a series of flat-panel displays (either LCD or Plasma) that are touch sensitive; and are programmed with the identical programming that is found on the legitimate Level C or D simulator – so there are no concerns about interoperability issues between systems, etc. I believe such devices can, and would, allow a pilot to complete training with less time in the aircraft or with less time in the Level C or D simulator – without having to have these new training devices meet any regulatory established standards and be qualified as some lesser level of “flight training device;” the caveat, of course, is that they DO, actually, function correctly. There are other pieces of training equipment that are similar, except they do not have the cockpit mockup with touch-sensitive screens. These cases involve the use of laptop computers (or desktop – dictated by preference), also have systems (often including avionics) programmed rather accurately, and are used for pre-classroom training by several major airlines and training centers. However, here too, the programming is based on manufacturer-supplied data and someone knowledgeable about what such programming should do has verified that programming. These devices are also very effectively used in these cases – but, again, there is no expectation that what is learned is complete and there is no implication that “flight training” has been initiated, let alone, been conducted.
The only modification I would make to my quote here, is where I said “I believe such devices can, and would, allow a pilot to complete training with less time in the aircraft or with less time in the Level C or D simulator,” and I probably
should have said “…allow a pilot to complete training with the potential of using substantially less time in the aircraft…” The specific amount of time would likely be directly linked to the accuracy of the training device. Personally, I draw the line between what is and should be “flight training” and what could be and likely should be “extended ground training.” The devices I described that are equipped with touch-sensitive screens and can be “flown” only through autoflight systems I believe are easily classed in the “extended ground training” family. Computers equipped with something like a “joy stick” that provides interactive pilot input and results in simulated airplane response are also candidates for this same family. However, when you walk
into something that for all the world looks like the cockpit of the airplane and you are able to climb into the seat and function like you would be piloting the airplane – we have now crossed over into the “flight training” segment – and these devices, I believe, must be evaluated against prescribed standards, initially and recurrently, and should have limits placed on them regarding what piloting tasks should be authorized to be conducted here instead of in the actual airplane.
I agree with your musing about having this (or another) thread get into the “meat” of simulator evaluation and certification – although, according to the regulators, they don’t “certificate” simulators … the “qualify” them. And, I too, would be interested in participating in that discussion.
Hi
XPMorten: GREAT link! Yes, diplomacy may not be Mr. Meyer’s strong suit, but I wouldn’t want to argue with his accuracy!