Fuel System Flashcards
How many fuel cells are there?
5
How are the fuel cells organized?
RALF
Right - Aft and center
Left - Forward and dorsal
How many pounds of fuel can be held?
4084 total
3906 single point refueling
3866 over the wing
When does the fuel low light come on?
less than 250lbs for 7.5 sec
What is the solo restriction for fuel?
right must not be more than 2x the left as this creates CG issues
What do the boost pumps do?
Send low pressure fuel to the engine driven pumps
What is normal fuel px?
10 PSI
When does fuel px light come on?
6 PSI
When is fuel gravity flow sufficient?
below 25k in MAX
flameouts have happened at 7k
below 6k gravity flow is guaranteed
What are the fuel shutoff switches powered by?
Left DC
What are the numbers associated with fuel imbalances?
0-50: no display
60-190: white display
200+: red, Xfeed
What is the problem with fuel pressure light and crossfeed off?
Boost pump failure
What is the problem with fuel pressure light and crossfeed on?
Fuel leak
What powers crossfeeding?
Left DC, switch opens and closes valve in crossfeed fuel manifold
What can cause a rapid fuel imbalance?
crossfeed on and either both boost pumps on or off
What happens if crossfeed is left on until the tank is dry?
A dual flameout occurs
When is crossfeeding not recommended?
BILLL
Boost pump inop
Indicator failure
low altitude
low fuel
leak
When is there an exception to crossfeed?
Single engine with <250 pounds
Does fuel flow show AB values?
No, the fuel flow sensor is only on the main fuel flow line
What powers the fuel quantity indicators?
Right AC
How many fuel probes are there?
7
What does the red bar mean for fuel qty?
less than 250 for 7.5 sec
What should you do if you have a fuel low caution light?
Maintain positive pitch to prevent cavitation from uncovered boost pump inlets
How much is boost pump output reduced with 650lb in the system?
40%
Can you use MAX with less than 650lb?
No
When should you not taxi?
With less than 150lb each side
When should you avoid MAX?
in 0 or negative G flight exceeding 10 sec at 10K and 30 sec at 30K
What is the FF of AB?
7300 PPH at SL
11400 at Mach 1 SL
How many spray bars are on the AB?
16 spray bars
4 pilot spray bars
How is fuel flow metered?
throttle position and compressor discharge pressure
What is T2 cutback?
auto reduction in RPM and EGT to prevent over-pressurization and high corrected speed limits of compressor at low compressor inlet temps, when high altitude, low airspeed
What is T2 bias?
the sensor can read much higher than actual compressor inlet temp and increases stall susceptibility due to the misguided T2 read by main fuel control and T5 scheduling
