Aerosoft Aerosoft Team [Inactive Account] 51558 Posted December 14, 2009 Aerosoft Share Posted December 14, 2009 Really got to find a level of question you guys are not able to crack in 30 seconds. Taxiing at 10 knots on a smooth surface the pilot accidentally retracts the gear. All safety systems fail and the gear is indeed being retracted. Yet the wheels do not come up. Why? Link to comment Share on other sites More sharing options...
Robert S 75 Posted December 14, 2009 Share Posted December 14, 2009 The rubber of the wheels (grip) and the relative speed (10 Knots) provide enough traction when combined with the weight of the aircraft so that the motors of the landing gear cannot overcome those combined forces to move the wheel directly laterally. In other words, take a pole, attach a free spinning wheel with tire, apply roughly 3500 lbs of downforce, roll it at 10 knots and just try to move that wheel laterally with force equal to a landing gear motor...the wheel will continue to move straight forwards! Robert Link to comment Share on other sites More sharing options...
Snave 466 Posted December 14, 2009 Share Posted December 14, 2009 Two answers to this one: 1: Many operating systems for gear extension and retraction rely on an over-centre rotation to commence the retraction sequence. The `knuckle joint` being probably the best-known example. Even in the event of microswitch failure the gear cannot physically retract until sufficient weight has been taken off the aircraft - or until the wheels leave the ground. and the smartarse aswer: 2: The `smooth surface` is water. Given the incompressibility of water it is exceedingly difficult for `conventional` gear to raise in water as it cannot overcome the resistance and the mechanism can be hydraulically locked by outside water! Same principle as applies to a submarine, where the ballast tanks are NOT fully-enclosed structures, but have free-flooding holes in the bottom. Only when the UPPER vents are opened does the air escape and the water rush in to fill the void. ...Oh and this answers another question about why amphibians usually have double-linkage gear and not simple rotation mechanisms. Lift and slide allows water to drain as the gear retracts. I'll get me anorak... Link to comment Share on other sites More sharing options...
Aerosoft Aerosoft Team [Inactive Account] 51558 Posted December 14, 2009 Author Aerosoft Share Posted December 14, 2009 All wrong so far. All safety systems fail, knucles joints and all. Link to comment Share on other sites More sharing options...
chucky 10 Posted December 14, 2009 Share Posted December 14, 2009 The wheels don't come up. The plane comes down. 1 Link to comment Share on other sites More sharing options...
Alexander Wurz 42 Posted December 14, 2009 Share Posted December 14, 2009 Well, the dictionary says, the word gear could mean in the nautical way somethin like dishes - and if the pilot is eating soemthing and he retract accidently his gear, it would cause a mess and no security systems could protect him And of course, all wheels stay where they are Link to comment Share on other sites More sharing options...
VPA159 2 Posted December 14, 2009 Share Posted December 14, 2009 I was going to say the squat switch, but that'd be considerered a safety system. Friction and weight counter balance the pull of the hydralics. There's not enough pull in the raising mechanism to overcome the weight and friction. Gear also is usually raised against the direction of travel (forwards), at least nose gear is. This helps lowering the gear with wind when airborne. If you're taxiing, there's friction going against the pull of the raising mechanism. The main gear retracts sideways, but the friction 90 deg off is still pretty powerful, especially since most of the weight is on those wheels. Link to comment Share on other sites More sharing options...
James A 39 Posted December 14, 2009 Share Posted December 14, 2009 All systems have failed therefore the wheels stay put. Nothing happens. Link to comment Share on other sites More sharing options...
Thralni 24 Posted December 14, 2009 Share Posted December 14, 2009 It really matters how you define "wheel" on this one. Do you mean the entire gear, as follows: the tires, suspension, the whole lot, or do you mean just the tirepart of the wheel? (can't find a good way to say it. How about "the turning thing"?) If it's the latter, the wheels stay on the ground while the fuselage and all appandages go down. Otherwise, I have no idea... Link to comment Share on other sites More sharing options...
FSXaddict 18 Posted December 14, 2009 Share Posted December 14, 2009 I was going to say the squat switch, but that'd be considerered a safety system. As well as the weight-on-wheels switch! But my guess is that since the systems have failed, they hydraulic system would fail, preventing the downlock strut from being unlocked and able to be moved from the over-center position. Link to comment Share on other sites More sharing options...
Alexander Wurz 42 Posted December 15, 2009 Share Posted December 15, 2009 Just a guess, butt I think you could also refer to one of the Catalina Models. One of them has no real Landing Gear, just some wheels to roll the Aircraft from a Hangar to the Water. If then the Pilot who is moving the Aircraft around accidently retracts the Gear, The Wheels won't come up, the Wheels would fall of the Aircraft and the Aircraft would fall down. Link to comment Share on other sites More sharing options...
Aerosoft Aerosoft Team [Inactive Account] 51558 Posted December 15, 2009 Author Aerosoft Share Posted December 15, 2009 The wheels don't come up. The plane comes down. Bingo, we got a winner! 1 Link to comment Share on other sites More sharing options...
chucky 10 Posted December 15, 2009 Share Posted December 15, 2009 I posted it as a joke, but then I thought maybe that's actually what he was looking for. The aircraft I was going to finish my complex checkout in recently had something similar happen to it, although it was going a bit faster than 10 knots, I understand. Link to comment Share on other sites More sharing options...
chucky 10 Posted December 15, 2009 Share Posted December 15, 2009 Oh, and I didn't see the stricture against pilots. I am a pilot, albeit an extremely new (and inexperienced) one. I'm not sure if this was one of the ones you wanted us to stay out of. If so, sorry (others got the answer after me, so the glory can go to them). I should read posts more carefully. Link to comment Share on other sites More sharing options...
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