CFI Pop Quiz #121 - Point

[Chris Burgess]

During turns around a point, an imaginary line from the pilot's eye and parallel to the lateral axis should point to the pylon when the aircraft is abeam the point headed directly

A) crosswind.
B) downwind only.
C) upwind or downwind.

[chuter]

I'm going to say "C", thinking that there wouldn't be a crab angle at these points in the turn.

[JByrd]

C - There is no bank correction upwind or downwind. Crosswind above the point requires less bank, below the point more bank.

Jim

[ventana7]

Sort of a confusing question. C is most correct.

Michael it is bank angle you are dealing with--which will change as Jim pointed out. Crab angle would refer to flying a specific track over the ground - ie crabbed into the wind to fly a straight line on a cross country trip or crabbed into the wind on final approach before you switch to cross control for landing.

[Chris Burgess]

When flying turns around a point in wind, the lateral axis, parallel to say the axle from the pilot's eye, will be in alignment with the pylon only during the time the aircraft is flying directly upwind or directly downwind, answer "C" is correct. At other times the aircraft will be crabbed into the wind, not aligned to it's movement across the ground. It is a varying bank angle maneuver from a downwind entry. Bank is in constant flux and you are crabbing except when flying directly downwind and directly upwind.

[ventana7]

Chris,
I understand the actions and aerodynamics completely but I disagree with the term crab.

IMHO --Since your manuver is a perfect circle and since what you are trying to teach a student is the concept of varying bank angle I think using the word crabbing can be confusing.


Crabbing is usually pointing into a wind to avoid drifting downwind and is done by changing your compass heading not by varying bank angle. This would apply more to X-C flight in a cross wind or on the legs in an instrument hold.

In my mind in the pattern you would use the concept of crabbing on downwind and on final approach and the concept of varying bank angle on your turns to and from base.

Keep em comming - these are some of the best info and discussions on the forum

Rob

[Matthew Parsons]

Where did the pylon come from? Is the point the pylon? Is this a turn around a point on the ground (apparent now from the discussion, but not from the question)?

For the answer to be valid, you must also specify that a constant range from the point/pylon be maintained.

Interesting question from a CFI. I thought you'd be encouraging flight towards a point, not flight around a point. Flight around a point would encourage flying with reference to the ground and the well discussed dangers of maintaining ground speed.

[Chris Burgess]

This can be a required "ground reference" maneuver for most gyroplane certificates. The Examiner has his choice of several but he must select one. "Turns Around A Point" is one. Point/Pylon/Pivot, that is your reference for a constant radius turn in winds. The question is as given in the FAA test. Sport Pilot practical test standards require you to be able to preform this maneuver. Even though you think of "crab" as a straight and level maneuver, think of each point in the turn. The only time your lateral axis is pointing directly at the point/pylon/pivot is when flying directly upwind or directly downwind. There will be some element of crab during all other times in the turn even though you are in a bank.

Matthew, there are standards of performance to include altitude within +/- 100 feet and airspeed +/- 10 knots. You should be trained for this by a CFI. I didn't write the question. "Turns Around a Point" is the name of this ground reference maneuver. It's elements are also discussed in FAA H-8083-21

[ventana7]

Chris,
I respectfully disagree.

Think of a fixed wing since the wing nicely makes our imaginary line to the pylon. If the pylon were a 1000' high tower and you flew around it in no wind the wing would always point directly to the tower. The size of your circle would determine how high up the tower your wing pointed.

But at any moment you should be flying on a 90 degree angle to the tower. ie. When you are due north of the tower in a left turn your DG should read 270. When you are at 359 degrees your DG should read 269 etc.

The goal in a wind situation is to describe exactly the same circle. In our previous example the wing always pointed to the same altitude of the tower-- say the 50' level. Now at some point in your windy turn it may point to the 20' level as you are more steeply banked and at others the 70' level as your bank is shallow. However your heading always remains at 90 degrees to the tower-- you are never crabbed into the wind otherwise you would not describe a circle.

If your lateral axis --ie the wing on a FW is NOT pointed directly at the pylon you are either in an uncoordinated turn (slipping or skidding) and are not doing the manuver correctly.



Rob

[Harry_S.]

Many years ago, they called this maneuver *Circles about a point* which required a constant radius on the point. In a wind condition this maneuver did require varying degrees in angle of bank.


Cheers :)

[Chris Burgess]

You may find it good reading to check a handbook on "Turns Around a Point". After all, I intend to stir your curiosity as well.