Contents
(Parenthetical remarks in italic by Gene)
Crabs, Kicks and Slips to Landings
The Problem
Ken Wiebe wrote:
This is a great thread. I've been wrestling (mentally) with slips, mostly having to do with crosswind landings. The side- vs. forward-slip references were confusing me, but now I think I'm getting it.
Awhile back there was a thread that dealt more directly with crosswind landing techniques, and naturally it got into sideslips. But one thing that confused me in that thread was crabbing, and references to the comfort of passengers, coordinated vs. uncoordinated, etc. Can we throw crabbing into the mix for this thread?
I think I understand how crabbing by itself can be a crosswind correction technique: Nose points into wind, ground track is at an angle to longitudinal axis. And this is all done by deflecting the rudder, and rudder alone, correct?
It seems like all slips are "uncoordinated" - but what about crabbing? I think I remember the x-wind landing thread where crabbing was referred to as "coordinated". Is that true? And, what does the ball do in these scenarios (sideslip, forward slip, crabbing)? Are there only two ways you can or should correct for x-wind? (I.e., the two main techniques used for the approach for crosswind landings - crabbing and side slipping) What if you're not on final and you need to correct?
Thanks in advance. In replies, please state what the ball is doing and whether it's considered coordinated. Also maybe discuss this pax comfort issue too.
Ken Wiebe
The Advice:
Crabbing is not what you do. Crabbing is what the wind does to you. When you "crab" to a landing you merely fly the airplane along. The wind blows you sideways as you go forward so your actual track over the ground is not quite in the direction your nose is pointed. Rather like rowing a boat across the river. If you want to go directly across, you had best point your nose upstream a bit!
When you "crab" down final you are merely flying in level flight and adjusting your heading to make the desired ground track, exactly as you do with flying cross country. It is more comfortable for the passengers because it IS coordinated flight. You are merely accepting the drift caused by the wind.
The problem with crabbing all the way to a landing, is that, when you land you are going one way and your nose is pointed the other. This makes for some strange and abrupt heading changes when (before) you touch down! :-) Fortunately, if you have a nose wheel, and have it well in the air as you should, when you touch down the abrupt heading change is in the correct direction for roll out. This is the standard crosswind landing technique for Ercoupes and Boeing 747's. :-) The approach is comfortable for the passengers, but the touchdown can give you a bit of a jerk! (Unless wing-low into wind corrects for drift when nose is straight with the runway.)
The ideal crosswind landing is to continue the crab, that you have been flying with all the way, whether you realized it or not, until you are about to land and then transition to a slip such that your sideways travel in the slip exactly matches the wind velocity. That way you wheels are pointed in the correct direction before you place them solidly onto the runway and there are no sudden changes at touchdown, making the whole process smoother and less alarming to pilot and pax. (Exact timing required but rarely achieved.)
How far away from touchdown should you make this transition? Let your conscience be your guide. Some teach the "kick-out" method where you make the transition just as your wheels are about to touch. The problem with this method is that it requires excruciatingly accurate timing. I find that my reflexes aren't up to that kind of timing consistently as I get older, and therefore prefer to transition from the crab to the slip far enough from touchdown to have the slip stabilized before I need it at ground contact. How far out is that? Depends. :-)
I recommend that student pilots begin to establish the slip as soon as the roll out of the turn from base to final approach. That gives them lots of time to play with the slip and get everything stabilized before they have to roundout and flare. Just be careful not to let the slip go when you start the roundout and flare!
Highflyer
Turns about a Point and S-Turns
The Problem
C. TASK: TURNS AROUND A POINT.
Objective 5:
Applies adequate wind-drift correction to track a constant radius circle around the selected reference point with a bank of approximately 45 degrees at the steepest point in the turn.
Advice:
From that, one would gather that selecting an 'approximate' bank angle of 45 degrees simply requires choosing a
distance from the point that calls for such a bank angle on the downwind turn. At least, that was how I was taught!
-Ryan
Advice:
At least one of my CFIs has indicated to ENTER on a 45-degree bank -- regardless of the wind. Another had me/let me go shallower. The MATH says that with NO WIND the whole thing will work at ANY CONSTANT bank -- say 30 degrees. And that if you have for each 10% wind speed relative to airspeed (10 kts for a typical 100 kt light trainer to keep the math easy) you need about 5 more degrees or less if you are trying to maintain the same arc as
the 30 degree no-wind circle:
10% == 25-35 degrees
20% == 20-40 degrees
30% == 15-45 degrees
40% == 10-50 degrees
The PTS that I read said, "a maximum of 45 degrees" but did NOT give a MINIMUM, nor did it give a maximum or minimum radius for the turn.
There is also the "just make a circle" school of thought.
What is the truth? The PTS as written? Created on the spot by the DE at checkride?
Herb Martin
(student pilot)
Advice:
From that, one would gather that selecting an 'approximate' bank angle of 45 degrees simply requires choosing a
distance from the point that calls for such a bank angle on the downwind turn. At least, that was how I was taught!
-Ryan
Advice
Applies adequate wind-drift correction to track a constant radius circle around the selected reference point with a bank of approximately 45 [degrees] at the steepest point in the turn. …and since you enter on the downwind, which is the part of the turn which requires the steepest bank, that would seem to require that you enter at a bank of "approximately 45 degrees". My instructor is also big on the "pick 4 ground reference points to hit as you make your circle" thing, and that's not in the PTS at all.
Ben Jackson
Advice:
If I remember correctly, you should not exceed 45 degrees of bank. 45 degrees of bank is considered a steep turn for a PPL certificate, and nowhere on the checkride will you be asked to demonstrate more than that. (Commercial is different)
If possible, pick out an intersection of two roads. Find 4 points along these roads that are equal distance from the actual intersection. While flying over these 4 points, keep planning ahead to the next point by adjusting bank to compensate for the wind. These points will be somewhere between 1/4 to 1/2 mile from the intersection. As you can see, you really won't be looking at the point you're flying around, but at the 4 reference points around that point...and always planning your flight for the next point. Wings should never become level, but adjusted constantly to compensate for wind so that a perfect (symmetrical) flight path is flown around the point. (remember to hold a constant altitude also) <g> Best,
BJ
I can tell you that my DE of many years ago wanted to see "fluid and total control" of the airplane while doing the turn about point. The bank angle didn't matter as it will vary as you complete the turn and how much wind correction it needed. I would start with a standard rate turn and then "vary" the bank angle depending on wind and location in the turn. The most important thing here is coordinated flight with proper inputs, altitude, airspeed and distance from reference point.
In my opinion, the best way is to determine the wind direction and enter from the downwind to establish bank angle then you know you will have to shallow the bank angle on the upwind part to "stretch" the circle and then return to your original bank angle to finish. Don't get hung up on a "particular" bank angle...use what works at the time. Don't look inside the airplane too much, mentally/visually "draw" a circle around the reference point and then just fly the airplane over that imagined circle using proper inputs. Good luck and hope this helps...--
Terry.
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