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brucek

What is and how to "spin" and "slip"??

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Maybe a stupid question for those who know -- but could somebody kindly give me a reasonably detailed description of what these are and how to perform them? Are they something that is done intentionally or unintentionally.? I am a little confused - as , not being a real life pilot, now that Rob Young has issued a new FDE for the C172 that allows these in FS2002 , I would have thought that a C172 was not supposed to spin in real life.Any advice much appreciated.Thanks Barry

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Hi, the C172 FDE comes with a reasonably detailed readme! :-)Best Regards, Uwe

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Sorry UWE -- but I would like to know more about these aircraft flight movements -- the README assumes that I already know what they are!!Barry

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Hi Barry, in my limited knowledge of English I'll try to explain what are "spins" and "slips".Spin is a maneuver or condition that an airplane performs in some circumstances. To "spin" an airplane you need to stall it first, then you apply full left/right rudder while you try to keep the airplane straight (wings levelled and positive pitch). Eventually, one of the wings will sink and the aircraft will start to fall and rotate in that wing axis making a "spiral" shape as it falls. Speed is usually low in this falls and in order to recover the airplane from this "spin" you need to apply full rudder in the opposite direction of the spin, low the nose of the airplane to gain speed and genteelly pull the nose up.A "slip" descent, is a maneuver that a pilot performs to gain maximum descent rates without gaining speed (most of the time in approaches). You can do it applying left/right rudder and rolling the airplane in the opposite direction (5 to 10 degrees). The airplane will approach similar to a high crab angle approach with vertical speed of -1500 fpm or more without speed increases. As soon as you reach the desire altitude you just position your airplane as usual and land. A simple aerodynamic explanation of this manouver is that the airframe acts like a big flap at the same time that you increase drag. I hope you can understand me, it's not easy to explain something this complicated in your second language.Carlos.

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I thought that you did great with that explanation.Tadd :)

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The Cessna 172 is approved for spins in real life. The POH covers the proceedures.L.Adamson

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>Hi Barry, in my limited knowledge of English I'll try to >explain what are "spins" and "slips". Thanks for this info>A "slip" descent, is a maneuver that a pilot performs to >gain maximum descent rates without gaining speed (most of >the time in approaches). You can do it applying left/right >rudder and rolling the airplane in the opposite direction (5 >to 10 degrees). The airplane will approach similar to a high >crab angle approach with vertical speed of -1500 fpm or more >without speed increases. As soon as you reach the desire >altitude you just position your airplane as usual and land. >A simple aerodynamic explanation of this manouver is that >the airframe acts like a big flap at the same time that you >increase drag. Is this the type of manouvre performed while in a crosswind landing ? If so, I have never read that the crosswind landing type slip causes a higher descent rate. Up till now I have only ever performed the "crab" type approach in a crosswind. I attempted to perform your instructed procedure while at 5000 feet , slowed to 70 knots with 2 lots of flaps as though I was about to descend on final at -300 FPM , - but applying full rudder first seems to almost instantly bank the aircraft and it was very difficult to then apply aileron to counteract it without altering course . Will have to practice some more - it obviously is an "advanced" technique for small aircraft flying.Thanks Barry

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When breaking/recovering from a spin don't forget to pull idle throttle or you could break the airplane on the pull out. You don't need to use full opposite rudder, just enough to stop the spin. If you use to much or don't neutralize the rudder after the spin is over, you go send yourself spinning in the other direction. Under VFR conditions use the ground to determine the direction of spin or in IFR, use only the turn coordnator / bank indicator (this is the only somewhat reliable gauge to use because everything else will be tumbling). When doing a slip (without flaps) you will actually gain speed, usually close to Vno. Well that's if you are in a hurry to get down. I'll do slips to lose altitude at 110kts which will give a pegged VSI at 2000ft/min down. Slipping without flaps are the normal procedure when in the air and need to loose altitude fast. When doing a slip to landing you can use flaps but be cautioned though, you could damage the flaps and or cause elevator instability. In real flying, I limit myself to only 20 degrees of flaps for slips to landing. When doing a slip either to land or loose altitude you must pull idle throttle before starting the slip and then apply full rudder first then adjust your roll as nessesary usually around 5 to 10 degrees like stated above. Slipping into the wind doesn't matter, I find that slipping it the left feels natural when flying leftseat.

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>Is this the type of manouvre performed while in a crosswind landing ?No, in fact I think is prohibited (I really don't remember). The risk of a spin stall is higher because you will need to apply too much rudder and bank angle too maintain runway course.The main reason to perform a slip approach/descent is to descent with high rates and without gaining speed. Why you need to descent so fast with slow speed? Several reasons, for example:1) You are too high and too close from the runway touchdown point. 2) You are in an emergency, you lost the engine and you are at 4000 feet and the only place you can land the airplane safely is 2 miles straight ahead from you.>I attempted to perform your instructed procedure while at 5000 feet , slowed to 70 knots with 2 lots of flaps as though I was about to descend on final at -300 FPM , - but applying full rudder first seems to almost instantly bank the aircraft and it was very difficult to then apply aileron to counteract it without altering course . Will have to practice some more - it obviously is an "advanced" technique for small aircraft flying.As a matter of fact this is an advanced maneuver, you'll need a lot of practice to get it done correctly. You have to find the right amount of rudder and the right amount of bank angle, too much rudder will make your airplane to flight away from the course you're suppose to be flying, too much bank angle you're increasing the risk of a spin stall in a very low altitude which would be catastrophic.Remember that when you are in a "crab" approach, your wing leading edge is almost facing the wind. In a "slip" descent, one side of your airplane is facing the wind causing an increase of drag (reduction of speed) and a reduction of lift (increasing the descent rate). Banking the airplane compensates the rudder and makes the airplane to flight in a straight line (runway course), also you are increasing lift because the airplane airframe acts like one big flap. You only need to find the correct amount of rudder and bank angle.Carlos.

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Hi Baz,In a spin: Imagine you are in a real 172, which has Pfactor (you can't turn it off in the real one :) ). This, of course, is the left turning tendancy caused by the unsymmetrical aerofoil effect of the prop at high angles of attack. This is counteracted with right rudder- you need more as you either get slower or increase angle of attack (or both). So- imagine that you don't use right rudder, and try to do a power-on stall. As your airspeed decreases at the high angle of attack you are holding to get into the stall, your airplane is turning left- and it does it quite aggressively as these stall speeds. One wing (the inside wing- or left) will stall more deeply than the other, as it's moving slower due to the left turning tendancy. This results in the a/c turning over, and then entering a spinning motion. To maintain the spin, you must maintain the stall, so back pressure is still required. Spins cannot occur without stalls.This was my first experience 10 years ago in a stall, in a 152. My CFI spent 5 minutes talking about P-Factor on the ground, then showed me a stall, then had me do one. I can recall the sun moving in a circle about the top of the a/c just before the stall, then we went inverted. I screamed, he took over, then after I had changed underpants :) he explained once again about P-Factor. I never forgot that experience, and still recall it to this day whenever doing power on stalls.Bruce.

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