march 26-27, 2003 international aircraft systems fire protection working group phoenix, az inerting...
DESCRIPTION
Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 3/26/03 Background FAA is seeking to improve upon existing fuel tank safety in fleet in the wake of TWA800 air disaster Inerting of fuel tanks could provide significant fuel tank protection. Focus of the testing is to validate the ability of the FAA simplified fuel tank inerting system to inert the CWT of a 747SP during a typical commercial flight profile Use modeling results to validate modeling methods with full-scale data Study inert gas distribution during the commercial missionTRANSCRIPT
March 26-27, 2003International Aircraft Systems Fire
Protection Working GroupPhoenix, Az
Inerting of a Scale 747SP Center-Wing Fuel Tank During a Typical Commercial Flight Profile
William CavageAAR-440 Fire Safety Research
Federal Aviation Administration
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________
Outline• Background• Model / Instrumentation• Test Data
– Effect of Holds at 5K Feet– Running System on Ground– Effect of Deposit Schemes– Starting Descent Altitude– Blocking Vent System Dive Port
• Summary
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Background
• FAA is seeking to improve upon existing fuel tank safety in fleet in the wake of TWA800 air disaster
• Inerting of fuel tanks could provide significant fuel tank protection.
• Focus of the testing is to validate the ability of the FAA simplified fuel tank inerting system to inert the CWT of a 747SP during a typical commercial flight profile
• Use modeling results to validate modeling methods with full-scale data
• Study inert gas distribution during the commercial mission
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Description of Model
• Quarter-scale model of Boeing 747SP CWT was built from three-quarter inch plywood by scaling drawings from Shepherd report– 24% length scale (1.4% Volume)– Spars and spanwise beams simulated with quarter-inch plywood
installed in slats with scaled penetration holes– Vent system simulated with PVC tubing plumbed to an
aluminum vent channel – Removable lid to allow for model maintenance and modification
• Model in 6x6x7 altitude chamber
• Model inerted with manual NEA mixer
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Photo of Model
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747 SP Bay Diagram with Volume Data
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Instrumentation
• Onboard oxygen analysis system (OBOAS) acquired bay oxygen concentration data– One sample port in each bay– Sample returned to tank through manifold
• Thermocouple in chamber gave temperature• Altitude measured by absolute pressure transducer• NEA Flow metered/measured with mass flow
controller and oxygen concentration determined with flow through type oxygen analyzer
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Onboard Oxygen Analysis System Block Diagram
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________
Altitude ChamberN
EA M
ixer
OxygenAnalyzer
Flow Controller
Scale Tank Testing Block Diagram
DAS
Nitr
ogen
CompressedAir
NEA Generator
Com
pute
r
T
OBOAS
PressureTransducer
Sample Return
Scale Tank Model
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Scope of Testing to Date
• All testing used same generic flight profile with different cruise times and different holds at 5K feet
• All testing uses same predicted system performance in terms of NEA flow and purity during above mentioned mission
• All tests had right side vent system blocked– Some tests had aft port on open vent side also blocked
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________OBIGG System Model
0
10
20
30
40
50
60
70
0 50 100 150 200 250 300 350
Time (min)
NEA
Flo
w (S
CFM
) / A
ltitu
de (k
ft)
0
2
4
6
8
10
12
14
Oxy
gen
Con
cent
ratio
n (%
O2)
NEA Flow Mission Profile NEA O2%
Climb
Cruise
Descent
System Model Data
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Effect of Hold at 5K Feet
• Baseline case (no hold) repeated with two different hold times– Hold at 5K feet– 5 and 10 minute holds
• Results indicate that holds using high flow mode have little effect on both tank average oxygen concentrations and worst bay oxygen concentrations– System is depositing NEA at approximate oxygen concentration as
tank– 5-10 minutes not that long to improve distribution for relatively
small spread
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60
Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 2 Bay 3
Bay 4 Bay 5 Bay 6
Descent Inerting Data - 39K FeetStarting [O2] 2%, No Hold
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
0 10 20 30 40 50 60
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
0
10
20
30
40
50
60
70
Altit
ude
(kft)
10 Minute Hold at 5K 5 Minute Hold at 5K No Hold Altitude - 10 Minute Hold Altitude - 5 Minute Hold Altitude - No Hold
Descent Inerting Data Comparison of Tank [O2]
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
0 10 20 30 40 50 60
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
0
10
20
30
40
50
60
70
Altit
ude
(kft)
10 Minute Hold at 5K 5 Minute Hold at 5K No Hold Altitude - 10 Minute Hold Altitude - 5 Minute Hold Altitude - No Hold
Descent Inerting Data Comparison of Bay 1 [O2]
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Effect of Hold at 5K Feet (Cont’d)
• Ideally like to decrease tank average oxygen concentration before you use high flow mode to improve distribution– Use low flow mode during a hold at 5K feet (lower’s average tank
oxygen concentration)– Switch back to high flow for final descent (distributes)
• Results illustrate this flow methodology improves overall average tank oxygen concentration at touchdown but doesn’t increase in the worst bay oxygen concentration – Using high flow mode to distribute gas has diminishing returns
• Effect of sample system minimal when checked
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60
Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 2 Bay 3
Bay 4 Bay 5 Bay 6
Descent Inerting Data - 39K FeetStarting [O2] 2%, 10 Min Hold at 5K
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 2 Bay 3 Bay 4 Bay 5 Bay 6
Descent Inerting Data - 39K FeetBaseline 10 Min Hold in Low Flow Mode
FinalDescent
Hold Pattern Touchdown
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60
Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
) Bay 1 Bay 1 Bay 2 Bay 2 Bay 3 Bay 3 Bay 4 Bay 4 Bay 5 Bay 5 Bay 6 Bay 6
Descent Inerting Data - Check DataEffect of Sample System on Result
Continuous Intermittent
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Running System After Touchdown
• Repeated baseline case touchdown data with two tests that run system on ground after touchdown– 15 and 30 minutes system run times– one test only sampled beginning and end of ground sit time
• Running System in Low Flow Mode After Touchdown did little for worst bay oxygen concentration– Gave consistent benefit over time for tank average oxygen
• Running System in High Flow Mode After Touchdown did decrease bay oxygen concentration spread– Average oxygen concentration changed little– Again, diminishing returns on reducing spread
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
40 45 50 55 60 65 70 75 80
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
0
10
20
30
40
50
60
70
NEA
Flo
w (C
FH)
15 Minutes 30 Minutes
NEA Purity NEA Purity
NEA Flow NEA Flow
Run System After LandingLow Flow Mode - Average Tank [O2]
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
40 45 50 55 60 65 70 75 80
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
15 Minutes 30 Minutes
Run System After LandingLow Flow Mode - Bay 1 [O2]
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 2 Bay 3
Bay 4 Bay 5 Bay 6
Descent Inerting Data - 39K FeetRun System 10 Mins After Touchdown
Touchdown
System Off
(High Flow Mode)
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Deposit Scheme Comparison
• Compared running system after touchdown with two different deposit scenarios– Duel deposit method deposits low flow mode in bay 6 and high flow
mode in bays 1 and 3– Multi-deposit method deposits all flow into bay 6 and bay 2
(approximate equal split)– Baseline used low flow mode during 10 minute hold pattern
• Fancy deposit schemes did little to improve touchdown average or worst bay oxygen concentration– More work needed
• Repeatability check gave excellent results
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
High Flow Only During Hold Run for 10 Mins After TD Dual Deposit Method Multi-Deposit Method
Descent Inerting Data - From 39K Feet10 Min Hold @ 5K - System Low Flow
FinalDescent
Touchdown
Hold Pattern
Average Tank Oxygen Concentration
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
High Flow Only During Hold (Bay 1)
Run for 10 Mins After TD (Bay 1)
Dual Deposit Method (Bay 3)
Multi-Deposit Method (Bay 3)
Descent Inerting Data - From 39K Feet10 Min Hold @ 5K - System Low Flow Mode
FinalDescent Touchdown
Hold Pattern
Worst Bay Oxygen Concentration
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 1 Bay 2 Bay 2 Bay 3 Bay 3 Bay 4 Bay 4 Bay 5 Bay 5 Bay 6 Bay 6
Descent Inerting Data - 39K Feet10 Minute Hold with Switch to Low Flow
FinalDescent
Hold Pattern
Original Test Repeat Test
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Starting Altitude Comparison
• Compared original baseline descent case (from 39K feet) with two additional starting altitudes (32K and 25K)– Used same altitude profile with different starting point (same descent
rates) with no hold– Approximated system performance best possible
• Results were as expected– Starting altitude will have dramatic effect on resulting average oxygen
concentration provided the tank is consistently inert for all cases
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
0 5 10 15 20 25 30 35 40 45 50
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
Descent from 25K Descent from 32K Descent from 39K
Descent Inerting Data Comparison of Average Tank [O2]
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________Effect of Blocking Dive Port
• Existing venting scheme does not give optimal inerting efficiency– Illustrated in constant inerting tests– Would improve by blocking dive port (aft vent port) on open side
• Repeated baseline test data (no hold) with this venting configuration– No effect on average tank oxygen concentration– Had adverse effect on distribution with 2% higher spike in worst bay
and a full 3% greater resulting worst bay oxygen concentration
• Compared two deposit schemes with this venting config– Use 10 min hold for comparison case– Only small effect observed on bay 1 spike and on result
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
0 5 10 15 20 25 30 35 40 45 50
Time (min)
Oxy
gen
Con
cent
ratio
n (%
vol
)
Rear Vent on Open Side Blocked
Half Vent System Blocked
Descent Inerting Data - 39K FeetAverage Tank [O2] Data
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25 30 35 40 45 50Time (mins)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 1 Bay 2 Bay 2 Bay 3 Bay 3 Bay 4 Bay 4 Bay 5 Bay 5 Bay 6 Bay 6
Descent Inerting Data - 39K FeetComparison of Venting Configurations
Touchdown
Normally Blocked Rear Blocked Also
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________747SP Scale Fuel Tank Inerting Data
0
2
4
6
8
10
12
14
16
18
0 10 20 30 40 50 60Time (min)
Oxy
gen
Con
cent
ratio
n (%
Vol
)
Bay 1 Bay 1 Bay 2 Bay 2 Bay 3 Bay 3 Bay 4 Bay 4 Bay 5 Bay 5 Bay 6 Bay 6
Descent Inerting Data - 39K FeetComparison of Venting Configurations
Touchdown
Duel Deposit Single Deposit
Hold PatternFinal
Descent
ISFPWG Meeting - 3/26/03
Scale Fuel Tank Testing___________________________________
• Scale model data shows FAA inerting methodology sound given the predicted system performance– System could be slightly undersized
• Using high flow mode only, decent hold buy you very little in terms of average of worst bay oxygen concentrations
• Running system on ground after touchdown in high flow mode will decrease oxygen concentration spread, but has diminishing returns (when average oxygen concentration is near 12%)
• More elaborate deposit schemes and system methodologies give relatively small performance benefit, but could improve inerting capability significantly of a marginal system
Summary