Engine System Flashcards
recommended supply pressure for engine start
APU-20 psi
crossbleed- 25 psi
external air- 30 psi
stop start if you don’t have ___ psi of supply pressure after start button pressed
15 psi
What does the “J” technique cover to prep for engine start?
generator
bleed air
aux pump
boost pumps
When to use each ignition for engine start?
A-odd days
B-even days
A&B-icing present/anti-ice required or turbulence is encountered or expected
N2 indication within ___ secs of start button in/on
20 sec
turn ENG Shutoff switch on when-
min. 18% N2 (20% is normal ops)
oil press > 5 psi
why do we delay until 20% N2 to turn on ENG shutoff switch?
it results in faster and cooler starts
normal FF?
400-500 pph
stop start if FF > ___ pph
700 pph
EGT rise (light off) within ___ sec of fuel on
20 sec
N1 RPM indication should display prior to reaching ___ % N2 RPM
40%- OAT above 0 deg C
30%-OAT 0 deg C or less
starter cutout at ___% N2
51%
manually pull out the ENGINE START button if ti fails to release by ___
55% N2
light may take up to ___ sec to extinguish after start button pops out
30 sec
minimum engine idle values
degrees Celsius-> %N2:
-40 54
-20 56
0 58
15 60
30 62
45 64
ENGINE START button doesn’t engage (push start button in and it doesn’t stay in)–
verify/change ignition source
if it still doesn’t stay in, may be held in for start
air conditioning pack disagree during engine start–
momentary may occur
if it’s continuous PACK DISAG=pack has not shut down
deselect that pack manually prior to 18% N2
if past 18% N2-STOP START
button pops out at 51% N2, but light stays on. How long can it stay on?
up to 30 sec after button pops out
after that-STOP START
isolate all air sources to the engine before “Engine Clearing Procedure”
starter attempt limits
2 consecutive starts with no wait period
then wait 15 min until 3rd attempt
10 minute wait between subsequent attempts
max of 5 attempts in one hour, followed by 1 hour cooling period
memory aid: 2-15-10-5-1
restart limitations
engine rotation completely stopped before starter re-engaged (exception when starter engaged in an emergency below 20% N2)
wait 40 sec after N2 disappears from the MFD to ensure rotation stopped
motor engine to get EGT below 190 deg C before introducing fuel
(time, EGT, N2 disappearing)
STOP START/engine clearing procedure
announce “STOP START”
if button still engaged:
ENG Shutoff Switch-> OFF
motor for 30 sec
pull start button out
button popped out: ENG Shutoff Switch->OFF allow N2 to wind down below 20%, preferably 40 sec wait to complete stop (except in an emergency) engage engine start button motor for 30 sec pull start button out
max time engine can be motored
15 mins
for motoring duration greater than 90 seconds up to and including 15 minutes, cool the starter for-
5 mins for each 30 seconds of operation up to a maximum of 40 mins
hot start reasons
hung start that is allowed to progress
failure to cool an engine below 190 deg C
excessively high FF ~700 pph when fuel switch (ENG shutoff switch) turned on
rapidly climbing EGT that’s NOT parallel to N2
when deg C should you stop a hot start before?
495 deg C
annotate peak EGT above 495 deg C and duration above
hung start reasons
occurs when an engine is not able to reach idle
indications of a hung start
no perceptible N2 movement towards idle or N2 rolling back
continued EGT rise above normal start values
if allowed to continue-hot start may result
will engine respond to throttle movement in a hung start?
no
how to deal with a hung start?
STOP START
engine clearing procedure
sub-idle hung start indications
typically after start cut out when OAT > 20 deg C
very slow N2 acceleration between 56-60% N and continuous EGT rise
EGT will eventually exceed limits
when would you suspect sub-idle hung start?
lesser RPM compared to other engines
or if engine hasn’t reached RPM for the OAT
max EGT for start
495 deg C
stable N2
green, not in sub-idle, see table
stable EGT
less than 460 deg C (bleeds off) 490 deg C (bleeds on)
stable oil pressure
70 psi minimum
stable fuel flow
800-1200 pph
APU- how long between start attempts?
starter may be run for 1 min with 5 mins between attempts
APU-how many attempts in an hour?
3 starts attempted per rolling one hour cycle
min of 5 mins between attempts
(APU: 1,5,3)
APU starter operating limit/what is considered a start attempt?
1 min
any APU starter engagement
What does the APU override not work for?
fire and overspeed protection
Why do we have an APU?
to provide electrical power, air conditioning, and air for engine start
What CB do you always check prior to APU start and why?
FIREX AGENT DISCHARGE 1 POWER CB (OVHD E13) because the APU Fire Agent DISCH switch will be inpoerative if it is open (DO NOT RESET CB)
What needs to be retracted prior to/immediately after APU start?
slats, to prevent damage to slat seals
After turning off APU bleed air, how long do you wait before turning off the APU?
minimum of 2 minutes
