A "Classifier 3" (CL:3) is a thumb-up three handshape. CL:3 is generally used to represent a vehicle. It can be used as a pronoun for cars, trucks, motorcycles, (some) boats, and submarines. It is NOT used for airplanes, but it is used in one of the variations of "helicopter."
See: CLASSIFIERS
Depending on the movement, you can use CL:3 to show the parking of a car, a row
of cars, an accident, etc.
CL:3 = "vehicles"
Some classifier usages become so common that they graduate to becoming
established, conventional signs. For example: It is easy to see the
"Classifier 3" roots of the the sign GARAGE. But the sign
"garage" is so common
that we don't think of it as a "classifier." We just think of it as "sign."
But if you use the CL:3 handshape to show 3 cars in a garage or if the cars are
parked forward or backward then you would be using the handshape as a
classifier.
GARAGE:
For more information regarding the "GARAGE" sign see: ► GARAGE
The sign for "crash" is "loosely" based on "CL:3" type handshapes. But if you observe
the sign done at high speed during signed conversations you'll notice that the
handshape starts as a "modified 5" handshape that turns into an "S" shape.
But again, it is easy to see the CL:3 roots of this sign.
CRASH:
CRASH: 
You can use a "CL:3" as part of the helicopter sign to show how a helicopter is moving through the air.
Below I'm showing a version of the helicopter sign. If I were to move the helicopter forward or sideways the sign would become a "classifier." If I just keep the sign in the same place and don't add any special movements nor any non-manual markers (eye-gaze, head movements, etc.) then it is not a classifier, but instead it is just a normal sign for "helicopter." If I do add other movement and non-manual markers, then this sign becomes a classifier showing me how the helicopter is functioning.
HELICOPTER (Version)
CL-3: "a very long row of cars"
First show the sign for "CAR" topicalized with your eyebrows up. Then show a
"CL-3" and an intense facial expression and move the CL-3 sideways in a
straight line about 12 or more inches.
Notes:
Notes: