Crosswind Landings - Crab or side slip??
06-20-2006, 06:31 PM
#51
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RE: Crosswind Landings - Crab or side slip??
Good question schokshi. Deserves a good answer.
A few considerations before we discuss X/W technique.
It's good that you're thinking about such things, but more important that you focus upon what's relevant to your training now. That's why good instruction is structured with a progressive syllabus. 10-12 dual (?) or ICUS 'solo' landings under your belt is too early (norm. ab initio stud.) to tackle a 10 kt X/W , especially with an LT-40. Your instructor should realise that and defer your X/W training until more suitable conditions exist. Unfortunately in R/C as so often happens, desire on both sides too frequently outvotes discipline, precluding the wisdom in that action.
Until you've had a solid grounding in and achieved a reasonable level in the basic competencies, instruction in X/W landing technique is ineffective, generally frustrating and essentially pointless.
Exacerbating that is the LT-40. A superb trainer, perhaps its only weakness if one might label it that is its poorer X/W performance in stronger X/W conditions. I say "poorer" because it has an exceptionally light wing loading with large area and high lift section which makes it susceptible during approach and landing to the effects of both orographic (gust) turbulance (relative AA) and ground track displacement for drift angle. In conjunction with its large side area, fin and large tail moment, it can be a handful in strong X/W conditions requiring anticipative and immediate confident corrective control input as required. 10kts steady cross would qualify as beyond the capability of a student at your stage, and a handful even for you average post solo with an LT-40. If it's gusting higher, all the worse. It's that designs only vice for GF IMEO, although not actually a vice in accord with the prerequisites for crosswind instructing given that ab initio instruction is actually its primary and designated role. Which leads to the point that initial X/W training should be conducted in X/W conditions more suitable to both to the design and taking into account the individual student, but not before the appropriate phase of training when the stud has demonstrated sufficient skills to cope with it. That's why there exists a time honoured proven successful syllabus which should be adhered to. In lighter crosswind conditions and when the student is ready, the LT-40 is a very good trainer for teaching crosswind technique precisely because it will exageratively exhibit all the characteristics a model will in crosswind allowing him to recognise and requiring he master the required control inputs to perform a sound crosswind landing.
As for crab or sidelslip. Crab is generally considered the easier to learn, but of course requires a larger correction to straighten up as you flare and is susceptible to significant drift if the aircraft is held of or has a predisposition to float in ground effect as the LT-40 does. Sidelslip requires superior co-ordination and timing, but is easier to fly 'onto the ground' so to speak, avoiding excessive float (and thus drift) during hold off and establishing a positive wheels on landing. Either are effective, although the latter is definitely preferable for a design such as the LT-40 or in very strong crosswinds. At this juncture, something to look to master in the future. Right now, you should look to congratulate yourself on airmanship of recognising when conditions are too difficult for your phase of training to render the particular air exercise effective (useful), and focus on having the discipline to accept and execute that "no go" decision in the face of the understandable enthusiasm driven desire to do otherwise. In that you'll make more progress than attempting to master something like X/W landings using either technique at this stage.
Here's a time proven maxim for your consideration and contemplation, which is of course as applicable to the crosswind landing as any other landing. Never attempt to turn a bad approach into an even worse landing, a common enough mistake of 'judgement' which has a high probability of having the resultant 'landing' going completely pear shaped and ending up with you damaging or completely breaking your model. Two words so easily and often ignored, "Go Around". If you're not established (ie: config. stable) on speed, on glide path, tracking runway heading by short final, execute a missed approach and overshoot to go around to set up another approach which is as a mandatory procedure. That's the golden rule to consistant, well flown and above all safe landings.
I did not want to extend my solo any more than necessary.
Name me anyone who does? "Measure twice, cut once".
Don't be in a hurry. Enjoy your time trainng. Sharpness of the tools, conditions and instruction available notwithstanding, you'll learn at the rate at which you're able. And remember, in all things aviation including R/C, intellect should always be master over ego, not the other way around. Happy landings.
A few considerations before we discuss X/W technique.
It's good that you're thinking about such things, but more important that you focus upon what's relevant to your training now. That's why good instruction is structured with a progressive syllabus. 10-12 dual (?) or ICUS 'solo' landings under your belt is too early (norm. ab initio stud.) to tackle a 10 kt X/W , especially with an LT-40. Your instructor should realise that and defer your X/W training until more suitable conditions exist. Unfortunately in R/C as so often happens, desire on both sides too frequently outvotes discipline, precluding the wisdom in that action.
Until you've had a solid grounding in and achieved a reasonable level in the basic competencies, instruction in X/W landing technique is ineffective, generally frustrating and essentially pointless.
Exacerbating that is the LT-40. A superb trainer, perhaps its only weakness if one might label it that is its poorer X/W performance in stronger X/W conditions. I say "poorer" because it has an exceptionally light wing loading with large area and high lift section which makes it susceptible during approach and landing to the effects of both orographic (gust) turbulance (relative AA) and ground track displacement for drift angle. In conjunction with its large side area, fin and large tail moment, it can be a handful in strong X/W conditions requiring anticipative and immediate confident corrective control input as required. 10kts steady cross would qualify as beyond the capability of a student at your stage, and a handful even for you average post solo with an LT-40. If it's gusting higher, all the worse. It's that designs only vice for GF IMEO, although not actually a vice in accord with the prerequisites for crosswind instructing given that ab initio instruction is actually its primary and designated role. Which leads to the point that initial X/W training should be conducted in X/W conditions more suitable to both to the design and taking into account the individual student, but not before the appropriate phase of training when the stud has demonstrated sufficient skills to cope with it. That's why there exists a time honoured proven successful syllabus which should be adhered to. In lighter crosswind conditions and when the student is ready, the LT-40 is a very good trainer for teaching crosswind technique precisely because it will exageratively exhibit all the characteristics a model will in crosswind allowing him to recognise and requiring he master the required control inputs to perform a sound crosswind landing.
As for crab or sidelslip. Crab is generally considered the easier to learn, but of course requires a larger correction to straighten up as you flare and is susceptible to significant drift if the aircraft is held of or has a predisposition to float in ground effect as the LT-40 does. Sidelslip requires superior co-ordination and timing, but is easier to fly 'onto the ground' so to speak, avoiding excessive float (and thus drift) during hold off and establishing a positive wheels on landing. Either are effective, although the latter is definitely preferable for a design such as the LT-40 or in very strong crosswinds. At this juncture, something to look to master in the future. Right now, you should look to congratulate yourself on airmanship of recognising when conditions are too difficult for your phase of training to render the particular air exercise effective (useful), and focus on having the discipline to accept and execute that "no go" decision in the face of the understandable enthusiasm driven desire to do otherwise. In that you'll make more progress than attempting to master something like X/W landings using either technique at this stage.
Here's a time proven maxim for your consideration and contemplation, which is of course as applicable to the crosswind landing as any other landing. Never attempt to turn a bad approach into an even worse landing, a common enough mistake of 'judgement' which has a high probability of having the resultant 'landing' going completely pear shaped and ending up with you damaging or completely breaking your model. Two words so easily and often ignored, "Go Around". If you're not established (ie: config. stable) on speed, on glide path, tracking runway heading by short final, execute a missed approach and overshoot to go around to set up another approach which is as a mandatory procedure. That's the golden rule to consistant, well flown and above all safe landings.
I did not want to extend my solo any more than necessary.
Name me anyone who does? "Measure twice, cut once".
Don't be in a hurry. Enjoy your time trainng. Sharpness of the tools, conditions and instruction available notwithstanding, you'll learn at the rate at which you're able. And remember, in all things aviation including R/C, intellect should always be master over ego, not the other way around. Happy landings.
06-20-2006, 06:36 PM
#52
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RE: Crosswind Landings - Crab or side slip??
Normally I agree with what Mike East says -- however, in this case I don't. Weathervaning doesn't exist in flight -- what the pilot observes is the difference between heading & track. The model pilot instinctively flies a track -- he makes the plane go where he wants it to go. In order to do that in a cross wind he must fly with an up-wind heading -- this misleads him into thinking that the model is weathervaning.
However -- weathervaning most certainly can occur on the ground -- with entertaining results.
However -- weathervaning most certainly can occur on the ground -- with entertaining results.
06-20-2006, 06:54 PM
#53
RE: Crosswind Landings - Crab or side slip??
Brit, again I think this is all about symantics. If were were all to go out to the field and observe a few flights I think we would all agree that we are saying the same things and seeing the same things. Its just difficult to clearly communicate in type.
Only thing is, call it anything you want but I most definitely see the plane pointing into the crosswind ever so slightly with a gusty crosswind, without any rudder input from me whatsoever. Thats a fact and a personal observation. Humbly speaking I'm not a real airplane pilot, but Im a pretty doggone good RC airplane pilot and I know exactly what I see on crosswind approaches. Its a weird thing to see but I do see it on gusty landing approaches all the time. Perhaps in a dead steady crosswind the plane will reach equilibrium in the wind and as you say it tracks in/out with the wind and the nose points straight into the direction the planes momentum carries it.
As a matter of fact I'm taking all of the fun out of this and agreeing with you guys after thinking about another form of flight where you can get a much better perspective on this. Bow Hunting, or shooting a bow and arrow. I never really thought about it at the time, but when I fire a bow, I momentarily see the arrow yaw back and forth slightly, but once it establishes equilibrium and levels out it may get pushed left or right by the breeze but it tracks forward "as straight as an arrow". [8D] All things in the universe being pretty constant I'm sure that the same thing is happening with the airplane, it has to.. BUT, I still maintain that in a gusty crosswind you can get some weathervaning as the side force is varied on the rudder and fuselage.
There I said it, are you happy?
Only thing is, call it anything you want but I most definitely see the plane pointing into the crosswind ever so slightly with a gusty crosswind, without any rudder input from me whatsoever. Thats a fact and a personal observation. Humbly speaking I'm not a real airplane pilot, but Im a pretty doggone good RC airplane pilot and I know exactly what I see on crosswind approaches. Its a weird thing to see but I do see it on gusty landing approaches all the time. Perhaps in a dead steady crosswind the plane will reach equilibrium in the wind and as you say it tracks in/out with the wind and the nose points straight into the direction the planes momentum carries it.
As a matter of fact I'm taking all of the fun out of this and agreeing with you guys after thinking about another form of flight where you can get a much better perspective on this. Bow Hunting, or shooting a bow and arrow. I never really thought about it at the time, but when I fire a bow, I momentarily see the arrow yaw back and forth slightly, but once it establishes equilibrium and levels out it may get pushed left or right by the breeze but it tracks forward "as straight as an arrow". [8D] All things in the universe being pretty constant I'm sure that the same thing is happening with the airplane, it has to.. BUT, I still maintain that in a gusty crosswind you can get some weathervaning as the side force is varied on the rudder and fuselage.
There I said it, are you happy?
06-20-2006, 07:27 PM
#54
RE: Crosswind Landings - Crab or side slip??
I think that this thread has gone about as far as it needs to be. It has digressed from an informative thread for beginners to a in-depth discussion of aerodynamics. As it stands now it is WAY above the level of the beginner's forum. I'm going to go ahead and lock this thread down.
Ken
Ken
