PROPELLORS EXAM REVISION Flashcards
1
Q
Describe the Hamilton Prop (5)
A
- 54H60-91
- 4 Bladed prop
- Electro-hydromatic (electrical inputs & hydraulic system)
- Fully feathering
- Reversible prop
2
Q
What is CTM
A
CTM: centrifugal twisting moment; mass of blades wants to align with the plane of rotation which tends to decrease blade angle.
3
Q
What is ATM
A
ATM: Aerodynamic twisting moment; Centre of pressure is forward of the blade pivot point so tends to increase blade angle.
4
Q
What is stronger of CTM & ATM and by how much?
A
CTM is the larger force for the C130, 20 times more powerful than ATM
5
Q
Flight/Alpha range properties
A
- Throttle setting 34-90deg
- Constant speeding prop
- Throttle schedules fuel flow only
6
Q
Ground/Beta range properties
A
- Throttle setting 0-34deg
- Controllable pitch propeller
- Throttle schedules FF and pitch/blade angle (for any throttle setting in ground range there is a subsequent blade setting)
7
Q
Purpose of feather override buttons
A
Give crew control of the feathering cycle should it terminate early or not terminate at all
8
Q
What electrical functions will occur if a fire handle is pulled?
A
- Fuel shutoff valve on FCU closes
- Oil shutoff valve closes
- Firewall hydraulic pressure shut off valve closes
- Firewall hydraulic suction shut off valve closes
- Firewall fuel shutoff valve closes
- Engine bleed air shut off valve closes
- Engine start circuits de-energised
- Prop feathered
- Extinguisher directional valves positioned
- Extinguisher agent discharge switch armed
9
Q
What is the purpose of the Barrell Assy?
A
Retains the blades % transmits TQ from prop shaft to the blades
10
Q
What is contained in the Dome Assy?
A
The pitch change mechanism and the low pitch stop assy
11
Q
What two sections make up the control Assy?
A
- Pump housing
- Valve housing
12
Q
What 3 sections can the Spinner Assy be broken down into?
A
- Front section
- Rear section
- 2x non-rotating afterbody sections
13
Q
What components does the pump housing contain? (4) & names
A
- 2x hydraulic fluid sumps (Atmospheric/pressurised)
- 3x prop driven pumps (Scavenge/main/Standby)
- 2x electrically driven pumps (au/aux scavenge)
- Low oil warning system
14
Q
How are the 5 pumps driven?
A
- 3x prop driven pumps: By a gear on the prop shaft
- 2x electrically driven pumps: BY an electric motor
15
Q
How are the aux pumps powered/energised?
A
- Powered: By a 115V AC aux pump motor
- Energised: when the condition lever is in feather or airstart or by pulling the fire handle
16
Q
Under what condition does the prop oil warning system illuminate?
- What does it look like?
A
- When fluid level is 2 quarts low
- PROP OIL annunciator in Tach indicator & master caution
17
Q
Main purpose of the prop governor?
A
- Corrects for off speed conditions
18
Q
What happens when an over/underspeed is detected by the flyweights?
A
- speed sensitive flyweights detect over/underspeed
- causes the pilot valve to move to port fluid into the pitch change mechanism.
- Corrects for offspeed by increasing/decreasing blade angle
- Once offspeed returns to 100%, flyweights and therefore the pilot valve nuetralise
19
Q
Two positions of the feather valve?
In which ways can the feather valve be positioned to feather?
A
Normal & Feather
- Manually
- Hydraulically
- Hydroelectrically
- The NTS plunger
20
Q
What occurs when feather valve is in ‘feather’? (2)
A
- isolates fluid path to governor
- Directs all hydrualic system pressure to the forward side of the prop dome
21
Q
How is the feather valve positioned to feather?
- Manually
A
- Manually: condition lever mechanically positions feather valve through linkages
22
Q
How is the feather valve positioned to feather?
- Hydraulically
A
- Hydraulically: condition lever mechanically positions feather actuating valve through linkages, which ports hydraulic fluid to move feather valve to feather
23
Q
How is the feather valve positioned to feather?
- Hydroelectrically
A
- Hydroelectrically: Condition lever or fire handle energises feather solenoid valve, that ports hydraulic fluid to move feather valve to feather
24
Q
How is the feather valve positioned to feather?
- The NTS plunger
A
mechanically positions the feather & feather actuating valve
25
Names of the 3 positions of the Feather valve & NTS test switch & what do they indicate
NTS/NORMAL/VALVE
- NTS: Light & annunciator illuminate on an engine when the NTS plunger operates
- VALVE: Light & annunciator illuminate on actuation of the feather valve
26
What controls the motion of the Alpha & Beta shafts
- Alpha: The movement of the throttle & condition levers rotates the alpha shaft
- Beta: The changing angle of the No. 1 blade rotates the Beta shaft
27
Propellor operation; Ground range (7)
(controllable pitch; throttle sets blade angle)
- Throttle advanced
- Alpha shaft rotates
- Beta set cam positions governor pilot valve to increase blade angle
- Blade angle increases
- Beta shaft rotates
- Beta follow up cam nuetralises governor pilot valve
- FCU schedules more fuel
28
Propellor operation; Flight range (7)
(constant speeding; governor sets blade angle)
- Throttle advanced
- engine power output increases
- Prop overspeeds
- Flyweights position governor pilot valve to increase blade angle
- Blade angle increases
- Increase in blade angle absorbs higher engine power bringing engine back on speed
- Governor pilot valve returns to nuetral (due flyweights)
29
What is the purpose & function of the Alpha shaft Speed Set Cam
Controls the tension of the speeder spring in the governor
- Flight range; 100% rpm so the governor controls RPM
- Ground range; 113% rpm so the governor will not interfere with prop functioning as controllable pitch prop.
30
What is the purpose & function of the Alpha shaft Backup valve cam?
Opens the 'backup valve' below 28deg coord, allows full decrease pitch pressure to retract low pitch stops as throttle is moved into the ground range.
31
What is the purpose & function of the Beta shaft pressure cutout backup cam (86deg backup cam)
Prevents pressure surges from terminating the feather cycle prior to 86deg blade angle
32
What is the purpose & function of the Beta shaft indicator cam? In what range?
Actuates a switch to bring on the BETA flag below 15-17deg blade angle
33
What is the purpose of the low pitch stops?
Sets a minimum blade angle of 23.25deg when the throttle is in the flight range
Prevents prop from reducing blade angle into reverse in flight
34
When do the Low pitch stops retract?
| What is the indication that signals the low pitch stops have retracted?
- throttle through 28deg
| - Below 15-17deg blade angle the BETA flag will appear in the TQ indicator
35
What is the purpose of pitch lock?
| What are the 2 occasions when pitch lock will engage?
- Prevents CTM reducing the blade angle and therefore excessive overspeed and drag conditions
- overspeed (103.5%) or loss of hydraulic fluid pressure
36
Rough description of how pitchlock works (in what range?)
How are the ratchets usually held apart?
What direction will the blades still be able to move?
- Ratchet rings engage between 25-55deg and the rotating cam and piston are prevented from further reducing blade angle.
- Ratchet rings are usually held apart by hyd oil pressure
- Blade angle can still be increased (feathered)
37
Why are the blades feathered to 92.5deg rather than 90deg?
As feathering the blades to 92.5deg means that the blades will want to rotate backwards, therefore engaging the prop brake
38
What occurs when the feathering cycle is initiated? (4)
- Feather override button pulls in & illuminates
- Prop aux pump motor is energised
- Feather solenoid valve is energised
- Above 86deg, pressure cutout backup cam arms pressure cut-out switch
39
What provides hydraulic fluid power in the feathering cycle once prop rotation speed decreases & why?
The aux pump, due to the main and standby pump output decaying (mechanically driven)
40
What occurs when the blades reach the fully feathered position? (6)
- Feather latches engage with rotating cam & halt its movement
- Hydraulic pressure increases to 1000psi
- Pressure cutout switch closes
- Feather override button pops out & light off
- Prop aux pump deenergised
- Feather solenoid valve deenergised
41
Airstart - how does it work?
- Condition lever is moved to air start position
- Energises prop aux pump
- Governor senses underspeed
- Blade angle decreases to correct, as this happens, air flow is used to drive prop
- Normal engine start system operates
42
When the prop brake is engaged during airstart, what happens?
The prop brake will drag until 23% rpm is reached when oil pressure is sufficient to hold the brake released
43
Pitchlocked propeller; if 96% rpm cannot be maintained when slowing towards 150KTAS;
- What can be assumed?
- What will shutdown at higher airspeed do?
- That blade angle is locked high (towards feather)
| - Shutdown at higher airspeed will produce an acceptable windmilling drag & rpm, should prop not feather
44
What are the three types of electronic governing?
| General signal flow?
- Speed stabilisation
- Throttle anticipation
- Syncrophasing
X ---- Synchrophaser box ---- Speed bias motor
45
Describe Speed stabilisation
Opposes any change in rpm. A change in rpm will be sensed by the tacho-generator
46
Describe throttle anticipation
Senses movement of the throttle & provides input into the governor before the offspeed condition occurs
47
Describe synchophasing
Ensures all engines run at the same rpm and synced to decrease vibe & noise. No 2 or 3 selected as master.
48
Limit to the synchrophaser box & speed bias motor limits
- Sync box: Can only adjust rpm to +/- 2%
| - Speed bias motor: limits travel to only +6% and -4%
49
RPM LIMITS
| - LSGI
- LSGI: 69 - 75.5%
50
Master caution indicator switches discrete when Tach indicator is;
- Weight off wheels
- Weight on wheels
- Weight off wheels;
> 102% RPM for less than 5 secs
>94 but <98% RPM (flap 0-42%)
>94 but <97% RPM (flap 42-100%)
- Weight on wheels
>106% RPM
51
Prop aux pump limits
1 min on, 1 min off
| Not to exceed 2mins operation in any 30min period
52
Prop static feather limit (2)
- max 23secs for blades to go from reverse to feather
| - If override button doesn't pop out within 6 secs of prop feathering, pull out manually & maintenance rqd
53
Reverse torque limit?
symmetrical TQ differences are >1000 in lbs, record
54
What two systems power the anti - ice system?
- 115V RH AC powers all except;
| - 28V LH DC, which powers the timer
55
What brings the icing system online?
Four ON/OFF prop ice control switches that work in conjunction with the prop & engine anti-icing master switch (AUTO/RESET/MANUAL)
56
engine anti-icing master switch (AUTO/RESET/MANUAL) functions
- AUTO: activates when ice is detected & individual ice protection switches are ON
- RESET: will turn off ice protection systems when icing no longer exits
- MANUAL: Allows manual control of individual switches
57
What does PHASE A power for the icing system?
Used to anti-ice the fwd portion of the front spinner & afterbody
58
What does PHASE B power for the icing system?
| Timer?
Used to DEICE the aft portion of the front spinner and the forward portion of the rear spinner
Timer applies power one at a time, for 15secs every 1min cycle
59
What does PHASE C power for the icing system?
| Timer?
Used to DEICE the aft part of the rear spinner & leading edges of the blades
Timer applies power one at a time, for 15secs every 1min cycle
60
How is power transferred for the icing system?
Transferred to the rotating prop through brush block and slip ring assy
61
RPM limit: Normal ground idle
- Normal ground idle: 94 - 102%
62
RPM limit: Max reverse
- Max reverse: 96 - 106%
63
RPM limit: Flight idle
- Flight idle: 92.5 - 100.5%
64
RPM limit: T/O & flight
- Take off/flight: 98 - 102%
