COMBINATION VEHICLES Flashcards
You supply air in the tanks by
pushing in the trailer air supply valve
Loss of air pressure in the emergency line causes
the trailer’s emergency brakes to come on
A tractor with a _ trailer requires the shortest amount of stopping distance
fully loaded
Which of these statements is true?
bobtails tractors can take longer to stop than fully loaded combination vehicles
If you cannot make a right turn without swinging into another lane, you should:
turn wide as you complete the turn
The tractor protection valve will close and the trailer emergency brakes will
come on when there is a major leak in what air line?
emergency
Off tracking or “cheating” causes which of these to follow the widest path while making a turn?
3 axle tractor towing a 45 ft trailer
If your vehicle gets stuck on a railroad crossing, you should:
get out of the vehicle and away from the tracks
When driving a set of double trailers, it is necessary to close shut-off valves
on some trailers. Where are these valves located?
at the back of trailers used to tow other trailers
Before you back under a trailer, make sure of what?
the trailer brakes are locked
To unlock the fifth wheel, you pull the handle to what position?
open
After connecting the air lines but before backing under the trailer, you
should:
supply air to the trailer, then pull out the trailer air supply valve
You are coupling a tractor to a semi-trailer and you have backed up but are not yet under it. What should you hook up before backing under it?
the emergency and service air lines
You are coupling a tractor to a trailer. The trailer is at the right height when:
the trailer is raised slightly when the tractor is backed under it
Why should you connect the air lines to a dummy coupler when they are not in use?
it will keep dirt and water out of the lines
The air leakage rate for a combination vehicle with the ENGINE OFF and the
BRAKES OFF should be less than _ per minute.
3 psi
Air and electric lines from the tractor to the trailer should be:
secured properly with enough slack for turns
Air brake equipped trailers made before 1975
often do not have spring brakes
The hand valve should be used
to test the trailer brakes
The air leakage rate for a combination vehicle with the ENGINE OFF and the
BRAKES ON should be less than__ per minute.
4 psi
Your emergency line breaks or gets pulled apart while driving. The loss of
pressure will cause the:
emergency trailer brakes to come on
You have pushed in the trailer air supply valve. You should not move the
vehicle until the whole system is:
at normal pressure
When should you use the hand valve to park a combination vehicle?
never
The best way to tell that your trailer has started to skid is to:
see it in your mirrors
A trailer is most likely to jackknife when it is:
empty
If the service line comes apart but the emergency line stays together, what
will happen right away?
nothing is likely to happen until you try to apply the brakes
When backing a tractor under a trailer you should:
always use lowest reverse gear
After you have coupled the trailer, you should begin raising the landing gear
using what gear?
low gear
You will know the trailer you are using has ABS by:
a yellow malfunction lamp on the left side
If you cross the air lines while coupling to an old trailer what will happen?
if the trailer has no spring brakes, you could drive away but you would
not have trailer brakes
When should you get out of your vehicle when you are backing a trailer?
when you are unsure of your path of travel
When you are uncoupling a loaded trailer, you should lower the landing gear until it:
makes firm contact with the ground, then turn it a few extra cranks in
low gear
How much space should be between the upper and lower fifth wheel after
coupling?
none
The front trailer supports are up and the trailer is resting on the tractor.
Make sure:
there is enough clearance between the frame and the landing gear
Why should you be sure that the fifth wheel is greased as required?
to prevent steering problems
After you lock the kingpin into the fifth wheel, you check the connection by:
pulling the tractor ahead gently with trailer brakes locked
After you supply air to the trailer, make sure the lines are not crossed and the brakes are working. This is done by:
applying and releasing the trailer brakes and listening for sounds
you should maintain at least one second of distance for each _ of vehicle length as following distance.
10 ft
Two things you can do to prevent rolling over are keep the cargo as low to the ground as possible, and:
go slow around turns
You have a major leak in the service line and you put on the brakes. Service air pressure will escape and if it goes low enough will cause the:
trailer emergency brakes to come on
When uncoupling a trailer, after you have locked the trailer brakes, you
should:
back up gently to ease pressure on the fifth wheel jaws
When do you need to use chocks to park a trailer that does not have spring brakes?
always
The fifth wheel locking lever is not locked after the jaws close around the kingpin, this means:
the coupling is not right and should be fixed before driving
When you get ready to back under a trailer, you should line up:
directly in front of the trailer
After you have coupled to a trailer, the tractor protection valve should be placed in the _ position.
normal
How should you test the trailer connection for security?
pull gently forward with the trailer brakes locked, then look at it carefully
The trailer air supply valve should automatically close when air pressure
falls to what range?
20-45 psi
What part of the kingpin should the jaws be locked around?
the shank
The higher your center of gravity of your truck, the:
easier it is to turn over
When checking that the trailer is securely coupled to the tractor, the landing gear should be:
slightly raised
If you must back your trailer on a curved path, you should position your
vehicle so you can back
to the drivers side
If your ABS is not working on your trailer, you should
drive normally but get the system serviced soon
Compared to a straight truck or bus, there are _ things to inspect on a combination vehicle.
more
Air lines are often colored. The emergency line is? The service line is?
red(emergency) blue(service)
To stop a trailer skid you should
release service brake
What gear should the transmission be in after you have uncoupled and are
inspecting the trailer supports?
neutral
You have coupled to a trailer. Where should the landing gear be before
driving away?
fully raised with the crank handle secure in the bracket
