Ch 6-10 Flashcards
1
Q
Effective range of a siren
A
limited to 80 ft at a 90-degree intersection
2
Q
Ambient Noise
A
- noise in the passenger compartment
- amount depends on speed, radio volume, A/C, and any other noise
- 6-10db above will ensure 100% detectability
- 15db recommended to ensure rapid response from the listener
- on avg, incr. of 1.2db for every 6.2 mph incr.
- ambient noise in idling vehicle = 32.4-66.7db
- traveling at 55mph = 53.4-76.3 db
- effective range can be no more than 80 ft
3
Q
Attenuation
A
- process of keeping noise out
- structure of vehicle will reduce sound pressure level of siren approx. 35db
4
Q
Sound Frequency of Siren
A
- louder at some frequencies than others
- low frequencies are better able to penetrate body of civilian car
- on avg, sirens produce a max of 124db 10 ft in front of speaker
- Inverse square Law = every time distance doubles, decrease of 6db
- effective range at a 90-degree intersection was limited to 26-39 feet
5
Q
Effective range of a siren can be no more than ___ ft
A
80
6
Q
Windows up or down
A
- windows can incr. 10-15db
- while stopped, can decrease attenuation approx. 10db
7
Q
Localization
A
- once heard, civilian must figure out where it’s coming from
- when sound strikes body of vehicle, it blocks and redistributes over the surface, making it difficult to localize
- in urban environment, sound will reflect off of buildings, also blocking line of sight
- study:
1. in an open room control grp could pick out 45% angle of siren 91% of the time
2. seated in car, fell to 37.6% w/ window open,
26% with window closed
3. CONCLUDED: not practicable for civilian driver to ID the location of approaching siren
8
Q
Civilian response to a siren
A
- response of an approaching emergency vehicle to civilian is a complex process including, hearing the siren, localizing, and then reacting
- closing the distance too quickly doesn’t give the civilian enough time to react, will result in crash or failure to yield all together
9
Q
One of the earliest known uses of sound as a warning device
A
- found in the Bible, people affected by leprosy were made to warn others of their approach
-Eldred and Sharp “Are present horns, whistles and sirens necessary for communications?”
10
Q
Negative right-of-way intersections
A
where the fire apparatus faces a red light, stop sign, or other traffic control device which indications not having the right-of-way
11
Q
Notice of Approach
A
- amount of time and distance required for the civilian
- Emergency vehicle doesn’t have right-of-way until a civ vehicle receives the approach, reacts, and GRANTS right-of-way
12
Q
NFPA 1500
A
-requires complete stop under the following circumstances:
1. when directed by DLE
2. red lights
3. stop signs
4. neg. right-of-way intersections
5. blind intersections
6. when drive can’t account for all lanes
7. other hazard present
8. stopped school bus w/ flashing warning lights
- requires FFs to wear helmets when riding in open cab or open tiller seat, but no helmet in closed cabs
- as well as hearing pro when cabin exceeds 90db
13
Q
Account for all lanes of traffic
A
- see and clear all lanes of traffic before continuing
- if driver can’t see because of obstruction, wait for it to clear or for light to turn green (addresses in NFPA 1500)
14
Q
Caravanning
A
- when multiple emergency vehicles drive directly behind each other
- leave plenty of space
- may be blinded by emergency lights in front of them (use dimmers if possible)
- be cautious of civilian drives not accounting for multiple vehicles
15
Q
Cautions at Green Lights
A
- steady greens can also be dangerous
- take foot of accelerator and cover break pedal while scanning for hazards
- be weary when no vehicles are stopped at the red, acting as a natural barrier from distracted drivers
16
Q
Apparatus Vs Apparatus
A
- be aware of other trucks response routes
- attempt to contract via radio
17
Q
Rolling an intersection
A
- may result in serious crash, especially when there’s limited sight distance
- full stop allows time to look both ways and evaluate
- “Keep in mind, our job is to save lives, not trade lives. Not running reds and stop signs, you’re giving yourself permission to act as judge, jury and sometimes executioner for other innocent lives on the road”
18
Q
Traffic Preemption Devices
A
- ability to take intersection while approaching, also controls pedestrian signals
- benefits:
1. reduce response times
2. reduce # of emergency vehicle crashes - Disadvantages:
1. won’t resolve conflict w/ other emergency vehicles at the intersection (some will flood lights will flash to notify that another vehicle has captured or is attempting to)
2. interoperability
3. understanding how much time it will take to capture and change
19
Q
Light-Emitting Traffic Preemption
A
- strobe light mounted on vehicle, activated by detector head on traffic signal
- large flood light on traffic cross bar activated to notify that intersection is captured
- avg range = 2500 ft
-Limitations:
1. dirty emitter or receiver heads can reduce effectiveness
2. heads can be struck by object and knocked out of allignment
3. line of sight obstructions (trees, lrg vehicles)
4. fog, smoke, inclement weather
20
Q
Infrared-Activated Traffic Preemption
A
- uses infrared transmitter
- more discreet and often used on unmarked police cars
- avg range = 1500ft
21
Q
Sound-Activated Traffic Preemption
A
- directional microphone mounted on traffic signal arm
- Disadvantages:
1. tripping unintentionally due to loud horns or other sirens in the area
2. misread due to siren reflection
22
Q
Radio-Activated Traffic Preemption
A
- activated by radio transmitter
- Advantages:
1. not affected by line of sight, visual
obstruction, or weather
2. capable of warning other emergency vehicles of possible intersection conflict - Disadvantaged:
1. possibility of interference from other devices that use the same radio frequency
23
Q
NFPA 1451 (7.2.3)
A
requires initial training and annual retraining on traffic preemption systems
24
Q
Removing SCBAs from the cab
advantages
A
- helps ensure seatbelt use
- the extra moments it takes the crew to make up allows the Officer a few extra seconds to size-up the situation allowing for incr in situational awareness
- reduced injuries due to the bulk and weight making it more difficult to exit cab safely
- seatbelt worn correctly, not loose to donn SCBA
25
Q
Rollovers and Seatbelts (statistics)
A
According to US Fire Administration’s “Emergency Vehicle Safety Initiative”
- 3/4 people who are ejected will die
1. 8/10 fatalities in rollovers involve ejection
2. 22 times more likely to be ejected in rollover when not wearing seatbelt
3. 80% of FFs killed in crashes weren’t wearing seatbelts
4. Only 3% of crashes in the US are rollovers, yet, are 1/3 of all occupant fatalities (over 10,000 people each year)
26
Q
Delta-V
A
- the change in vehicles velocity over a period of time
- gauges severity of non-rollover crash
- manufacturers reduce severity by increasing the time it takes for the crash to stabilize by installing crumple zones and airbags.
- seatbelts will ensure that occupant is properly positioned to allow airbags and supplemental retaints to do their job
27
Q
Lap belts can cause…
A
head, spinal, and abdominal injuries as the FFs body is flung against lap belt
28
Q
Wearing helmets while responding
A
- NFPA 1500 states no helmets while riding inside enclosed passenger cab
- if a vehicle is rear-ended, seat headrest is designed to absorb crash energy and prevent whiplash or neck related injuries
- brim of helmet causes unnatural position which may contribute to more serious injuries
- decrease safety distance b/t head and roof during rollover
29
Q
“Where should FFs put their helmets?”
A
NFPA 1901 states they must be in an enclosed and latch compartment, or a bracket, able to contain its contents when subject to 9 g force longitudinal and 3 gs in any other direction
30
Q
Kinematics
A
- motion of bodies or objects inside the vehicle
- when driver slams on brakes and occupants head keeps moving forward
- if not restrained during rollover, an occupant/object can become a dangerous missile
31
Q
Roof Crush
A
- caused by weight of the vehicle
- high probability of roof coming in contact w/ heads and necks of FFs
- If properly restrained, there should be enough headspace to prevent
32
Q
Ambulances and Occupant Restraints
A
- difficult for emergency medical personnel to perform necessary medical procedures while properly restrained
- to facilitate better seatbelt use, first ID the primary care position, then train on how to use the position to provide Pt care
- training programs should include:
1. performing as much care as possible on scene
2. attempt to time Pt care w/ red lights and stop signs. If no urgency, pull over briefly
3. design ambulance so that equipment is in arms reach
4. when buying new trucks, research restraint system. If possible retrofit to other trucks
Know most appropriate place to secure a child safe seat in transport compartment. Infants should NEVER be positioned in a side-facing orientation, exposing them to flying equipment or airbags during crash
33
Q
NFPA Requirements
A
- apparatus should never move until all occupants are restrained.
- Don’t rely on display screen, always look to ensure
- only 3 exceptions: urgent Pt care, hose loading operations, and tiller training
34
Q
If there’s a seatbelt malfunction…
A
- that riding position is taken OOS
- if it’s the driver’s seatbelt, the whole truck is taken OOS
35
Q
Railroad Crossings
(Passive warning systems)
A
- unguarded, meaning not equipped w/ safety gates
- usually consists of advance warning signs, posted some distance before the crossing, as well as signs and road markings directly at the crossing
36
Q
Railroad Crossings
(Active warning systems)
A
- used at busier rail crossings
-include gates and flashing lights when train’s approaching - decision to install usually left to highway safety authorities. Considerations include:
1. # of vehicles that will cross
2. type of vehicles
3. # of trains that will use the tracks daily
4. Hx of collisions at the crossing
37
Q
Railroad Crossings
A
- it will take a train going 55mph 1 mile to emergency stop
- try to avoid routes w/ crossings if pos.
- ensure there is enough room on other side before crossing (containment or storage area)
- train will be at least 3 ft wider than the tracks
38
Q
When arriving at railroad crossing…
A
- turn off sirens, air horns, and other sound-producing devices to better hear approaching train
- slow down, open windows, look both ways
- if sight obstructions or severe curves present, stop and ask crew member to get out and check down the track
39
Q
If apparatus stalls or gets hung-up on crossing….
A
- quickly contact rail agency
- if unable to notify:
1. use fire or other agency(DLE) personnel to warn the train before arriving at crossing
2. reach them by radio to find a safe area about 2 miles from the crossing
3. from this location, road flare or flashlight should be waved in an exaggerated fashion side-to-side at waist level
4. this will signal them to stop
40
Q
“Operation Lifesaver”
(www.oli.org)
A
- useful tool for any fire apparatus operator or driver trainer
41
Q
On gravel roads there are no pavement markings or stop lines. The stop lines on each side of a single track grade crossing are at least __ ft apart. Remember to apply emergency brakes while waiting.
A
35
42
Q
Why use air brakes?
A
- several reasons on large trucks
1. infinite supply of air that will never run out
2. compressor can generate constant supply of air to power brake system, even if there’s an air leak
3. generates much more stopping power than hydraulic
4. much smaller application to brake pedal generates larger amount of stopping power
43
Q
Downside to air brakes
A
lag time- time it takes to pressurize the system w/ enough power to engage brakes
44
Q
Dual system air brakes
A
- in most vehicles w/ air brakes for redundancy
- one will operate the front and one for the rear (primary and secondary)
- if one system fails, you still have the other
45
Q
Spring brakes
A
- air brake chambers are divided into two sides: service brake side and spring brake side
- in spring brake side, air pressure compresses a powerful spring, which hold the brake in a released position for wheels to move freely. When “PARKING BRAKE” is pulled, it releases the pressure and spring, locking the wheels
- Also used as the EMERGENCY BRAKING SYSTEM. Acts as a failsafe if air leak causes pressure to go below a predetermined level. Instead of losing the system, the spring brake will engage and stop the truck
46
Q
Service brakes
A
- other side of the brake chamber
- AKA foundation brake
- used during routine driving
- can be equipped w/ drum or disc brake systems
47
Q
Operation of Drum brake system
A
- apply brakes
- air travels from tank, through lines, into brake chambers where…
- compressed air presses against rubber diaphragm, expanding it to push on the pushrod which…
- pushes on slack adjuster, turning the camshaft
- which will twist an S-cam which will expand the brake shoes and press the brake pads against the drum, creating friction
-size of brake chamber depends on size and weight of the truck and which axle, can range from 9, 12, 16, 30. and 36 sq in
- amnt of force depends on size; applying 100 lbs of pressure to a size 20 brake chamber = 2,000 lbs of force on the pushrod
- dist. pushrod has to travel to properly apply brakes is known as “stoke”
48
Q
Operation of Disk brake system
A
- apply brakes
- air travels from tank, through lines, into brake chambers where…
- compressed air presses against rubber diaphragm, expanding it to push on the pushrod which…
- pushes on slack adjuster, turning the power screw (instead of S-Cam on drums) which..
- engages the brake calipers which clamp the brake pads onto the brake disc. Causing friction
-size of brake chamber depends on size and weight of the truck and which axle, can range from 9, 12, 16, 30. and 36 sq in
- amnt of force depends on side; applying 100 lbs of pressure to a size 20 brake chamber = 2,000 lbs of force on the pushrod
49
Q
Inspecting the air brake system
(The Pennsylvania Department of Transportation–Commercial Driver’s License Manual recommends the following procedures)
A
- locate air compressor- if belt driven, check belts
- check slack adjusters- Park on level ground, chock wheels, release parking brake. If slack adjuster moves an inch or more, it needs to be adjusted. If loose there’s an underlying problem causing excessive wear
- check drums, brake assemblies, and air hoses for cracks, signs of excess wear or fluid leakage
- test air leakage rate- charge to 125psi, turn of engine, release parking brake, and time air pressure drop. Should be less than 2 psi per min
- next, apply at least 90 psi w/ pedal, after initial pressure drop, shouldn’t fall more than 3 psi per min
- Test low pressure warning signal (low pressure warning usually 60psi)
- check for spring activation- w/ vehicle chocked and off, step on and off pedal until brake knob pops out (usually 20-40psi)
- check rate of air pressure buildup- should build from 85psi to 100 psi in 45 sec for dual system. Pre 1975, single systems should go from 50psi to 95psi in 3 min
- check the air compressor governor- should turn on below 100psi and shut off around 125psi
- test parking brake- while engaged gently apply throttle
- Test service brakes- release, slowly drive forward, then stop
50
Q
NFPA 1911
A
Standard for service tests of fire pump systems and fire apparatus section (7.12) “braking systems”
51
Q
Brake fade
A
result of systems inability to burn off excess kinetic energy
52
Q
Mechanical Fade - Drum Brakes
A
- overweight or speeding vehicle may create more energy than brakes were designed for which may overheat and start to fade
- happens when FFs believe they should should shove more hose/equiment onto a truck, overloading it
- due to overheated, swollen brake drum, the brake shoes are no longer able to press the brake pads against the lining of the brake drum. Loses braking efficiency
53
Q
friction fade
A
- friction of brake pad is reduced
- two theories involving the binding agents that hold the composite brake pad together
1. over-heated pad gives off gas, forming a layer b/t pad and drum(or rotor)
2. binding agents begin to melt creating a slick surface - Glazing- when no longer able to grip
54
Q
fluid fade
A
- in hydraulic brakes
- while brake fluid isn’t compressible
- vaporized brake fluid is
- must be compressed before it’s able to reach the brake fluid to activate the brakes
55
Q
cascade failure
A
- if one brake starts to fade
- causes more stress on others
- eventually causing cascade failure
56
Q
Annual weight certification
A
- NFPA 1911 requirement
- weighed on certified scale by certified weigh master
57
Q
causes and types of brake imbalance
A
- improper adjustment
- mismatched parts
- failing relay valves
two types: - air imbalance- air must reach all brakes at the same time and each brake must have the same crack pressure (amnt of pressure needed to open the valve to engage brakes)
- torque imbalance- more torque = more braking power, when different sized slack adjuster or brake chamber is installed
58
Q
pushrod stroke
A
- if too long, delayed application and reduced efficiency
- checking them should be a routine part of every truck maintenance program
59
Q
applied stroke method
A
- chock, turn engine off, release brakes, visualize brake chambers under truck
- have someone apply brakes a few times until pressure b/t 90-100psi
- mark pushrod where it meets face of the brake chamber
- have assistant make full brake application
- measure dist b/t the mark and the face of the brake chamber
60
Q
Downshifting and auxiliary braking
A
- two methods to reduce brake fade and increase lifespan
- NFPA 1901- aux brakes required on vehicles w/ gross weight rating over 36,0000
- some activate when foot comes off break, others when brake pedal pressed, others are manual by hand control
- different power settings such as high, low, and/or a percentage
- shouldn’t be used on wet roads
61
Q
NFPA 1901- aux brakes required on vehicles w/ gross weight rating over ______
A
36,000 lbs
62
Q
Compression release engine retarder
A
- 4 functions of a piston: induction, compression, power, exhaust
- valve will open allowing air to escape during compression
- no energy left to push piston back down
- driveline will pull it back down, absorbing vehicle’s forward momentum
Engine turned from energy producing combustion engine into energy absorbing air compressor
63
Q
Exhaust retarder
A
- butterfly valve attached to exhaust manifold
- open and close to block exhaust from leaving manifold
- creating back pressure
- restricts movement of piston, slowing the driveline and wheels
64
Q
Electro-magnetic retarder
A
- series of electrical coils places around flywheel, which is attached to driveline
- when activated, they energize and slow the flywheel w/ magnetism
65
Q
Transmission retarder
A
- transmission fluid will enter flywheel chamber to slow it down
66
Q
Snub braking
A
- recommended when descending down a long grade
- produce same amount of heat as long/soft application
- prevent air imbalances w/ crack pressure valves
1. apply brakes hard enough to feel a slowdown
2. when reduced around 5 below a safe speed, release (about 3 seconds)
3. when speed incr within a safe speed, repeat
67
Q
Anti-lock brakes (ABS)
A
- w/o ABS - threshold breaking - brake to the point where tires are about to lock, release, then manually pump brakes
- w/ ABS - Stomp, Stay, Steer
1. Stomp on brake pedal
2. Stay on brake pedal
3. Steer around hazard
As ABS engages: - w/ hydraulic will cause pulsing feeling and strange noises from pedal
- w/ air brakes not much is felt, may hear hissing noise from wheels
68
Q
A
