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Old 13th Nov 2017, 18:30   #1 (permalink)
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Simulator "Ground Handling" Characteristics

Dear colleagues,

I have been wondering: How well does the simulator you use regularly replicate your aircraft type's ground handling characteristics i.e. during ground roll on the runway. How realistic (or not) are crosswind handing and asymmetric thrust operations including engine out t/o aborts, V1-cuts, landings and roll outs?

I have been very disappointed with most (basically all, to varying degrees) biz jet sims I have used and my last time in a 733 sim was 15 years ago so can't remember the details.

The recent 747 runway excursion prompted lot's of replies saying how difficult a low speed outboard engine failure is on a 747 and it got me wondering how much of that could be down to very twitchy sim characteristics.

On the Flight safety Level D sims I have used recently (all very new sims) runway operations feel more like skating on ice and not at all like they do in the aircraft.

Also, colleagues who have done actual single engine training in the aircraft have told me that it was almost a non-event compared to the sim.

Is this the same or similar in modern Airbus and Boeing sims?

Last edited by 733driver; 13th Nov 2017 at 19:05.
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Old 13th Nov 2017, 18:47   #2 (permalink)
 
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Haven't been in a simulator that could correctly simulator ground motion, especially lateral acceleration was always wrongly simulated. Keyword here is "simulator sickness". But it helps if you keep the speed low, taxying at 5kts is quite fine

Apparently there is some simulator algorithm that could improve that, but i haven't been in a simulator that was equipped with that. See About Lm2 - AWx - Acceleration Worx
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Old 13th Nov 2017, 19:04   #3 (permalink)
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Thanks Denti. I agree. The motion can never seem to replicate the correct forces.

However, forces and motion aside, how well do modern airline type sims replicate/simulate what the aircraft does? For example, is is much harder in the sim to control the aircraft on the runway with a crosswind component and/or asymmetric trust? That has been my experience in the biz jet world and I'd like to know if airline style sim training these days suffers from the same lack of realism especially during ground ops (runway stuff, not necessarily taxi ops).
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Old 13th Nov 2017, 19:56   #4 (permalink)
 
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Hi 733driver,

There was a good discussion a few years ago on PPRuNe
See simulator-training-strong-crosswind-landings.
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Old 13th Nov 2017, 19:57   #5 (permalink)
 
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In my experience, crosswind landings are more challenging in the simulator. In those cases, I have learned to ignore my physical sensations and focus on the imagery before me.

Agreed with Denti that ground handling dynamics are generally poor and I admit to having suffered with slight dizziness during simulated ground ops on occasion.
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Old 13th Nov 2017, 22:06   #6 (permalink)
 
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On 733drovers comments that started this thread, yes the old girl(747-1 thru 8) are all a handful on outboard engine failures. I've seen all kinds of techniques most with little to no real help. The recognition of the failure is all important. Immediate call out, rapid thrust reduction and load the binders is the only thing that works.


I watched one crew repeatedly fight for control even with reasonable throttle reduction. The Captain kept insisting that the yoke be held full forward with massive brakes jammed on. As the nose kept heading closer to the runway edge. Lets do that over again, OK? Now, this time leave the yoke were it is, no forward load and see what happens. Worked out much better, stayed reasonably close to the center line. The discussion that followed: The Captain had lots of hours in tankers and that is what they did. Loading the nose on a 74 only compresses the nose strut and reduces the weight on the other sixteen wheels and brakes. Love to see light bulbs illuminate through the ears.
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Old 14th Nov 2017, 07:59   #7 (permalink)
 
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Expected so much more from the a350 sim , rubbish on the ground
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Old 14th Nov 2017, 10:03   #8 (permalink)
 
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Sims cannot produce acceleration. Human body apart from visual cues experiences g loads which cannot be simulated. As a result there is a mismatch between visual cues and sensation (which is absent). That triggers symptoms like having eaten a poisonous substance. I have seen a captain throwing up in Sim. However I find A320 sim fairly OK in crosswind landings and EFATO. In Airbus nothing much happens with engine failure so may be easier to simulate.
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Old 14th Nov 2017, 10:21   #9 (permalink)
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Again, I'm not so much talking about how "sensations" are simulated but rather what the aircraft (sim) does on the ground. For example, it would normally be very difficult to ground loop a transport category aircraft (or any tricycle gear aircraft for that matter) on a dry runway with good braking action but in some sims I have had the "pleasure" to fly, it was very "easy" to do. A take off abort with an engine failure would sometimes result in ground loops resembling ice skating figures. Same for significant cross winds on landing even with everything done right (de-crab in the flare, increasing into wind aileron during roll-out etc): Sometimes the thing would just ground loop just before reaching taxi speed. Happened to me (and witnessed others do it) in more than one sim. Never had a problem with crosswinds in the real aircraft....
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Old 14th Nov 2017, 12:22   #10 (permalink)
 
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pf, #7. Perhaps you should reconsider your expectations. Simulators are only models of the real aircraft; “all models are wrong, but some are useful” - the aptly named George Box, FRS.
A conclusion of ‘rubbish’ relates more to an expectation opposed to the real aircraft. Unfortunately many people use simulators inappropriately because of this, inferring performance or manoeuvre beyond the data used in the model.

733 #9, re ‘sensations’; these are central components of a simulated replication of an aircraft by providing a feedback loop for control - consider the overall system, man, machine, and environment (real vs simulated). A good representation of sensation can mask a poorly simulated aircraft. More often the reverse, particularly with reduced side force / acceleration where a poor representations of force or visual scene conflict with the aircraft dynamics; this mental conflict creates additional workload or need for physical compensation. Also consider how an expert pilot views a simulation vs a novice pilot, the latter might adapt by forming a technique for the sim which also applies to the aircraft ... or not !
Directional control with nose wheel steering might involve larger side forces or visual yaw depiction than that used in flight, thus it is of lesser quality, possibly limited by sim motion - how much sim tilt is required to replicate side force, how accurate, how long (for acceleration). Also, force feedback is important. Does the NWS tiller provide accurate force representation vs that which might be provided by rudder steering - relate this to the simulated environment, a dry runway vs simulated wet/slippery vs crosswind. (The last old sim I flew never met tyhe book landing distance on a wet runway - negative training for a landing overrun, ... or a positive contribution to emerg evac drills after a ‘surprise’).

Overall I agree with the concerns, and also with continued growth and emphasis on simulator training the machines (models) must have adequate fidelity for the task - and even greater fidelity for learning from mistakes, perhaps something beyond the training objective. Do we best learn from doing it ‘right’ or after a mistake?
I suspect that many regulators, having previously specified the quality of simulators, now envisage using them beyond their current capabilities with the risk of negative training.
Cost is always a driver, thus use a sim opposed to an aircraft; but perhaps the industry is approaching the boundary where using an aircraft will provide the greater cost benefit, in particular for those experiences and levels of confidence which cannot be simulated.

‘Simulators can create surprise, but they might never create fear potential startle’.
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Old 14th Nov 2017, 18:34   #11 (permalink)
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Shouldn't we expect a lot from a level D simulator which qualifies for zero flight time training?

I think the sim should simulate the aircraft's handling qualities (including on the runway, but not too worried about taxiing) as realistically as possible. If it turns out that the maximum achievable level of realism is not all that high then why have ZFT training in the first place?
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Old 14th Nov 2017, 19:13   #12 (permalink)
 
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Quote:
A take off abort with an engine failure would sometimes result in ground loops resembling ice skating figures. Same for significant cross winds on landing even with everything done right (de-crab in the flare, increasing into wind aileron during roll-out etc): Sometimes the thing would just ground loop just before reaching taxi speed
I don't know which aircraft SIM or which manufacturer you are mentioning I have not seen any of this in A320 SIM. Except tyre burst, and low speed reject TO if not handled properly it can happen.
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Old 14th Nov 2017, 21:30   #13 (permalink)
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I was referring to the two latest generation Flight Safety International (FSI) biz jet sims I have "flown" recently. Sorry, if this is still a bit vague.
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Old 14th Nov 2017, 22:03   #14 (permalink)
 
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There is actually no "ground handling qualities" department at Airbus, and one could guess it's the same at others manufacturers, so it's really no surprise that ground characteristics are poorly simulated.
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Old 15th Nov 2017, 03:18   #15 (permalink)
 
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In CAE Airbus simulators EFATO, reject take of simulation is good. I have done QTG for simulators in which we even reject with engine fail on contaminated runway and distance measured. Forget about ground loop you can keep it dead straight.
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Old 15th Nov 2017, 04:29   #16 (permalink)
 
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They are SIMulators not DUPLICATORS, as long as the fidelity levels satisfy the regulatory authorities this is all that we can expect....
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Old 15th Nov 2017, 12:04   #17 (permalink)
 
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Think how far the aircraft cockpit actually moves sideways over the ground during a 90 degree turn say - for an A320 it's about 30 meters ! There is no way the SIM can physically move that far, so it cannot reproduce the correct physical sensation.

It can give an idea of some forces, for example on take-off to simulate the acceleration, the whole SIM pitches up about 40 degrees, but it keeps the window views and the PFDs level so your brain thinks you are sitting level but you are pushed into your seat because unseen by you, the SIM has actually reclined, so gravity is being used to simulate forward acceleration.

I don't know if the SIM rolls to simulate sideways accelerations, but none of the many SIMs I have been in have given very good sideways rendition, especially with engine failures around V1 - it’s mostly visual and audio. Although, to be fair I have never actually had a real engine failure at around V1, so I don’t know what it feels like !

On every type I have flown so far; when I get out to fly the real aircraft, it flies much better than the SIM, and is much easier !

{Incidentally, the reason we sometimes have motion-sickness is because when the signals from our balance organs and our eyes disagree, the brain assumes we must have eaten a neuropoison, so it wants to empty the stomach! Closing your eyes - if you can ! - removes one source of disagreement and usually prevents the feeling of sickness.}
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Old 19th Nov 2017, 23:21   #18 (permalink)
 
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Not standing up for or against any one simulator, but here is what the current standards are for the FAA
From 14 CFR part 60
Appendix A, TABLE A1A.—MINIMUM SIMULATOR REQUIREMENTS - Programming:
2.d.3. ... Ground handling characteristics, including aerodynamic and ground reaction modeling including
steering inputs, operations with crosswind, braking, thrust reversing, deceleration, and turning radius.

Appendix A, TABLE A2A FULL FLIGHT SIMULATOR (FFS) OBJECTIVE TESTS
Test # 1.b.7.
Title= Rejected Takeoff
±5% time or ±1.5 sec
±7.5% distance or
±250 ft (±76 m).
Test details - Record time and distance from brake release to full stop.
Speed for initiation of the reject must be at least 80% of V1 speed. The airplane must be at or near the maximum takeoff gross weight. Use maximum braking effort, auto or manual.

And then from the Initial/Upgrade evaluation, which is subjective.
(3) Rejected Takeoff (Dry/Wet/Icy Runway) and check the following:
(a) Autobrake function.
(b) Anti-skid operation.
(c) Motion/visual effects during deceleration.
(d) Record stopping distance (use runway plot or runway lights remaining).
Continue taxiing along the runway while applying brakes and check the following:
(e) Center line lights alternating red/white for 2000 feet/600 meters.
(f) Center line lights all red for 1000 feet/300 meters.
(g) Runway end, red stop bars.
(h) Braking fade effect.
(i) Brake temperature indications.

Everything else is subjective. One level D sim I worked on had a malfunction for a nose gear collapse. One crew wrote it up, saying the aircraft slid too long on the runway after the nose structure touched the ground. My questions was "You know this how?"
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