Retracting Landing gear
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What is the bug?
I don’t think it is critical for ARI to be off. Automatic coordination would be fine and pilot could still command uncoordinated flight as overriding input. My guess is that ARI off for landing is to prevent ARI from coordinating stab to hit runway.
Did you read what I wrote ???
Ari is off when wheel speed is more than 60kts
This is disconnected to manage rudder and aileron independently due to cross wind on ground
The bug is that the brake is not working fine when gear is retracted
So the ARI kicks in normally since wheels are slowing down on their own anyway
We are talking seconds here
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@mavjp Is that 2 to 3 falcon weeks or real weeks lol
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@mavjp Is that 2 to 3 falcon weeks or real weeks lol
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3 - 4 administrative weeks. Plenty of time to still enjoy what we have!
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The bug is that the brake is not working fine when gear is retracted
Sorry, this is the first time I read this. I didn’t see it written before. And BMS pilot cannot manually press brakes either?
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The rudder is inducing roll by aerodynamic coupling , not from flcs
ARI kicks in when wheel speed is less than 60kts
Of course this is modeled in BMS since the real one is in
Does the gyroscopic moment of the wheels affect the flying qualities at all? Expect that would be a small affect but…curious.
Also - is the tire growth due to rotation modeled? (again…just because I’ve see a few RL jets bent by non-dero on retraction…would be a cool failure mode to incorporate.)
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Given the direction the gear moves during retraction, and the direction the moment would act, I dont expect there would be any impact on the flying qualities.
Then again Im not an engineer, so take that cum grano salis.
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It’s a second order effect - and would probably be very small. No idea if or how well BMS models second order effects like inertial moments.
The more interesting thing was something I encountered while working on the T-45A - a drawing of the tire growth due to rotation on takeoff - as I spent some time working on brake system mods on that little jet. As drawn/calculated, the tire will not fit into the wheel well while rotating at takeoff speeds - the A-Skid system de-rotates the tire on retraction automatically…in the olden times pilots used to tap the brakes on climbout and/or prior to retraction to de-spin the tires. Doing that with some newer gear systems can actually cause a more severe failure or damage to the brakes or gear system having to do with the sheer inertia of the wheel assembly and the sudden application of the brakes whout any rolling resistance…I recall that being one of the things we had to pass on to the TA4 and T2 crews at some point.
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inertial moments like that required for a roll departure? Those seem fairly well detailed in the FLCS article.
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I think that for rolling departures one cares about inertial moments of the whole plane; probably the mass of the wheels (even considering the speeds they can be rotating) is too small compared to that of the plane to be significant.
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That’s what I’m thinking of - whole aircraft, but more of gyroscopic and not inertial moment…but the two effects can add. And not an aerodynamic departure - just the speed of the wheel during the takeoff roll…the tire grows. If the jet is rolling on the runway and the pilot applies the brakes the wheel slows gradually, but if the jet is airborne and the pilot applies brakes the brakes may lock the wheels suddenly - in that case the momentum of the wheel may be great enough to bend something. That’s a reason there’s an automatic system to stop the wheels prior to or during retraction.
Spinning objects on the jet can have an impact on other control requirements…usually not to an extreme effect, but to some extent. I recall it being of note with the Pegasus engine on the Harrier, forex - that engine’s spools (hot vs cold sections) counter-rotate in order to lessen control power required to overcome gyroscopic effects as I recall. That’s a BIG consideration in designing rotating machinery for flight, in general - particularly for mechanical design of shafting. I also recall hearing that some jets do/can react quicker in one direction than the other depending on which way the engine spins if both spools turn the same direction…it’s just physics, and the point of my question about any spin while the wheel is in the well having a resultant effect - modeled or not.
https://www.real-world-physics-problems.com/gyroscope-physics.html
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Yeah you get some gyroscopic rigidity in your system then you increase the coupling between different torques. I dunno what a ~100 lb spinning disk 30" in diameter (x2) compares to the pitch and roll and yaw torques going on. Spinning engine masses has got to be larger in magnitude by a couple orders of magnitude though. I don’t know what RPM 160 knots is on a tire circumference but the turbines are much much much more.
Considering that the wheels will be equal and opposite mostly in angular momentum vector it can’t net much.
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Hmmmnnn…I’d expect that they would be additive in angular momentum because they are both spinning in the same direction (main wheels). But what might factor more is the distance that each wheel is from the centerline of the aircraft…further away being worse?
I hate math in public…if I recall the resultant is at 90 degrees to the applied torque, with sign dependent on direction of rotation? But the geometry also has to have some effect. I should think…
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This must be surely the only sim where we can enjoy such a thoughtful, informed discussion about a topic such as this.