A Physiological Safety Case Investigation.

A Physiological Safety Case Investigation.
F-22 Raptor
Multipurpose Fighter



Stealth: Greatly increases survivability and
lethality by denying the enemy critical
information required to successfully attack
the F-22
Integrated Avionics: Allows F-22 pilots
unprecedented awareness of enemy forces
through the fusion of on- and off-board
information
Supercruise: Enhances weapons effectiveness;
allows rapid transit through the battlespace;
reduces the enemy‘s time to counter attack
Single Best Air to Air Fighter
―If it finds you, it will kill you, and you won‘t know it was there!‖

Maximum speed: **At altitude: Mach 2.25 (1,500 mph, 2,410 km/h) [estimated]
◦
Supercruise: Mach 1.82 (1,220 mph, 1,963 km/h)

Range: >1,600 nmi (1,840 mi, 2,960 km)with 2 external fuel tanks
Combat radius: 410 nmi (with 100 nmi in supercruise) (471 mi, 759 km)
Ferry range: 2,000 mi (1,738 nmi, 3,219 km)
Service ceiling: >65,000 ft (19,812 m)

Armament









Guns: 1× 20 mm (0.787 in) M61A2 Vulcan 6-barreled Gatling cannon in right wing root, 480
rounds
Air to air loadout:
◦
◦
6× AIM-120 AMRAAM
2× AIM-9 Sidewinder
◦
◦
2× 1,000 lb (450 kg) JDAM or
8× 250 lb (110 kg) GBU-39 Small Diameter Bombs
Air to ground loadout:
2× AIM-120 AMRAAM and
2× AIM-9 Sidewinder for self-protection, and one of the following:
Harpoints: 4× under-wing pylon stations can be fitted to carry 600 U.S. gallon drop tanks or
weapons, each with a capacity of 5,000 lb (2,268 kg).


Incidents make the
news
Stealth Fighter Jet Chokes Yet Another Pilot

By Robert Beckhusen

07.10.12

2:58 PM

An F-22 prepares to refuel during a training flight. Photo


May 2012 – 60 Minutes
interviews 2 ANG pilots.
Two pilots say they've
gotten dizzy and
disoriented while flying the
F-22, due to a lack of
oxygen. The men are so
concerned about their
safety, and their colleagues,
that they put their careers
on the line by speaking with
"60 Minutes."


The F-22 pilots who
talked: Why they did
it
Breaking the chain of
command and appearing on
60 Minutes--in uniform--is
no small matter. Here's
what it took for two Air
Force pilots to tell their
story to the world.

60 Minutes Story aired May 6 2012

Several Investigations were underway!
◦ "We grounded it for a reason, you know, back a year ago," added Wilson, who's been
flying the F-22 for two years. "We haven't done a single thing to fix it. So I think we
need to reassess why we got back in the air in the first place.―
◦ Jeremy Gordon: ―The onset of this is insidious. Some pilots will go the entire mission,
land, and not know anything went wrong. There was a publicly announced incident of
a jet in Alaska hitting a tree and the pilot was not aware that he ran into a tree.‖
◦ Jeremy Gordon: Amongst F-22 pilots, there's a term called the "raptor cough.―
◦ To make matters worse, some of the pilots began coughing up black sputum. Air
Force doctors cut into oxygen hoses, found - as this doctor's photo shows - black
residue. And determined that the new filters that were supposed to be protecting
pilots were shedding charcoal and pilots were breathing it in.
◦ Lesley Stahl: Here's an email that we have seen from one of your fellow pilots. "I feel
I'm in the most expensive group of lab monkeys ever assembled."

Issues with the F-22‘s oxygen system were first
flagged in 2010 after a crash killed Capt. Jeff Haney
close to a military base in Alaska.
◦ An Air Force investigation put the crash down to pilot error,
maintaining that Haney did not activate the emergency
oxygen system in time to avert catastrophe. In the Press
this was blamed on Hypoxia.

In a separate incident, one pilot reportedly becoming
so disorientated that he skimmed some treetops
before pulling up.
◦ Found NOT to be Hypoxia related.

Pilots began coughing up black sputum
◦ No reports of this occurring
◦ Found in Oxygen Supply lines
◦ CXR and Sputum – all normal



From 2003 to April 2008, there were 6 F–22 physiological issues,
but between April 2008 and January 2011, that number had
doubled to 12. As a result of this, the Air Force Commander of
Air Combat Command restricted the F–22‘s maximum flight
attitude to 25,000 feet and directed a safety investigation board
to review the F–22‘s oxygen system.
In May of 2011, the Secretary of the Air Force directed the
Scientific Advisory Board to gather information and make
recommendations to address concerns relative to the F–22 life
support system. From May to September 2010, the F–22 fleet
stood down as a result of an upward trend in reports of
physiological incidents.
The Scientific Advisory Board [SAB] completed its work in January
of 2012, but did not determine a cause for the F–22 pilot
physiological problems. However, the board did make findings
and recommendations and concluded that either the supply or
the quality of the oxygen is contributing to the F–22 pilots‘
hypoxia-like symptoms.

Initial Scientific Advisory Board reported from
fiscal year 2002 to May 2011, the Air Force
incidence rate of 13 hypoxia events per 100,000
hours compared to 7.5 in the F-16, and 1.8 in
the F-15E (with a direct contributable cause), and
Navy reported 6.6 in the F-18E, F and G, over
roughly the same period.
◦ F-16 with a direct contributable causes usually
mechanical, recognized and corrected in flight.
◦ F-15E with a direct contributable causes all mechanical,
recognized and corrected in flight.
◦ F-18E, F and G, (Actually exceeded 18 per 100,000
hours at one point),



Alaska – Several Safety Investigation Boards
◦ With each incident a Safety Board was Convened 20082011
Langley Boards stood up with each incident 20102011.
Air Force Scientific Advisory Board – Spring 2011

Root Cause and Corrective Action [RCCA] analysis process initiated

F-22 SIB – ACC driven Safety Investigation –early
2011
Air Force Life Support Task Force - 2011

NASA- Advisory Board –April 2013

◦ F-22 Physiological Board
◦ Toxicology Board
◦ OBOGS Investigation


In a July 5 2012 press release issued by the Air Combat
Command, Major General Charles Lyon, the ACC‘s director
of operations, said that a number of initiatives were put
into place to protect F-22 pilots, including comprehensive
aircraft and life support system inspections.
―We have taken a 9-1-1 call approach,‖ Lyon is quoted as
saying in the press release. ―We have instructed our airmen
in the field that whenever they get any indication that
something may not be right, knock it off, and terminate
the flight. We focus all our attention on them and the safe
recovery of the aircraft.‖
◦ The F-22 was at that time the USAF‘s most expensive aircraft,
with the 185 jets currently in service costing an estimated $79
billion.

Emphasis by press ―But despite the program‘s high costs,
the Raptors have yet to fire a shot in anger.‖


Air Combat Command established a Life Support System
Task Force, which continued to examine both the issues of
supply and quality of oxygen in the F-22. On April 23,
2012, the National Aeronautics and Space Administration,
NASA, accepted a request from the Air Combat Command
to form an independent investigative team to review Air
Combat Command's investigative process, ongoing root
cause analysis, and the F-22 life support system as a
whole to determine potential vulnerabilities to the pilot.
On July 24th, 2012 the Department of Defense announced
that Air Combat Command had determined that the root
cause of the F-22 pilot physiological issues is the supply
of oxygen delivered to the pilots, not the quality of oxygen
delivered to the pilots.
[H.A.S.C. No. 112-154] F-22 PILOT
PHYSIOLOGICAL ISSUES
 __________
 HEARING BEFORE THE SUBCOMMITTEE ON
TACTICAL AIR AND LAND FORCES OF THE
COMMITTEE ON ARMED SERVICES HOUSE OF
REPRESENTATIVES ONE HUNDRED TWELFTH
CONGRESS SECOND SESSION
 __________

HEARING HELD SEPTEMBER 13, 2012

Complex Issues







―I can‘t remember any part of the mission‖
Pilot was wanting to know where his helmet and
mission forms were. Advised they were in his right
and left hands. Returned to the ops desk and again
wanted to know where the items were. They were still
in his hands.
―Foggy and can‘t read the instruments correctly‖
―I really had to work to get a breath‖
―I couldn‘t process the information. I was behind the
jet from ‗knock-it-off‘ till back in the pattern.‖
Headaches and muscle aches for days post the
missions.
Resolved with Oxygen bottle activation or hyperbarics
post mission.

Systems Investigations
◦ OBOGS – On Board Oxygen Generation System
 Compared and contrasted
 System Testing
◦ Life Support Systems

Human Risk Factors – Two separate Boards
◦ Investigation of Physiology
◦ Toxicology Investigation
 Jet Studies
 Contaminant Studies
1) QUANTITY
The F-22 oxygen
delivery system is
failing to deliver
adequate O2 to the
pilot, resulting in
hypoxic symptoms that
threaten safety of flight
2) QUALITY
The F-22 oxygen
delivery system is
either producing or
failing to filter a toxic
compound(s) in the O2
to the pilot resulting in
hypoxic-like symptoms
that threaten safety of
flight
21
5/2011 – 5/2012
•
•
•
•
Tested aircraft
Developed MCM
Executed response protocol
Closed gaps
5/07/12 – 5/11/12
5/14/12 – 5/18/12
6/04/12 – 6/08/12
Chemist &
Detection Experts
Forum
Medical Expert
Incident Review
Investigative MCM
Deep Dive
Review Incident
Pilot Medical Data
Make RCCA
dispositions and
recommendations
Peer Review
MCM
5/2011 – 5/2012
•
•
•
•
Tested aircraft
Developed MCM
Executed response protocol
Closed gaps
•Over 2183 samples taken from the different incident aircraft.
•Numerous different types of samples taken from various parts of the
aircraft.
5/2011 – 5/2012
•
•
•
•
•
•
•
Tested aircraft
Developed MCM
Executed response protocol
Closed gaps
Molecular Characterization Matrix (MCM) has characterized over 900 compounds
detected in lab and aircraft environments utilizing 15 types of sampling media
Contains:
•
Peak compound levels detected from all testing efforts
•
Compound levels detected on incident jets
•
Generates Hazard Indexes for incident jets
•
Individual compound hazard assessments
•
Types of detection equipment required to ―see‖ compound
•
Filtration capabilities and interaction with OBOGS and C2A1 filter
•
Possible source information (aircraft fluids, materials, maintenance, etc)
Used to evaluate potential contamination impact on F-22
5/2011 – 5/2012
•
•
•
•
•
•
•
Tested aircraft
Developed MCM
Executed response protocol
Closed gaps
Post incident samples were taken from the jets
Pilot checklist completed
Pilot medical assessment completed by medical personnel
•
Blood and urine samples taken if deemed necessary
•
Additional medical tests run if deemed necessary
5/2011 – 5/2012
•
•
•
•
•
•
•
•
•
Tested aircraft
Developed MCM
Executed response protocol
Closed gaps
An Edwards jet was instrumented to collect real time data on quality of
air in flight
Field teams deployed to search for classes of compounds not detected by
testing at the jet
OBOGs testing conducted
Exhaustive fluid characterization on aircraft conducted to assess possible
source of compounds detected on post incident collections
Sample analysis performed to assess the quality of air in cockpit and
breathing systems
OGOGS Inlet
OBOGS Outlet
Compound
C3-C12 analysis
n
(of 39)
median
(ppbv)
min
(ppbv)
max
(ppbv)
n
(of 39)
median
(ppbv)
min
(ppbv)
max
(ppbv)
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Undecane
Dodecane
25
11
2
1
6
16
15
16
15
14
51
19
10.5
470
10
14.5
11
35.5
56
35
23
13
10
na
9.6
8.8
5.9
6.2
8.7
14
10000
35
11
na
510
170
82
250
160
94
27
10
2
1
4
18
8
16
19
14
210
33.5
44
39
17.5
11
22.5
22.5
31
24.5
23
21
26
na
13
6.6
7.6
5.9
6
6
14000
340
62
na
70
45
43
140
92
88
Compound
TO-15 analysis
n
(of 61)
median
(ppbv)
min
(ppbv)
max
(ppbv)
n
(of 61)
median
(ppbv)
min
(ppbv)
max
(ppbv)
Ethanol
Acetone
Methyl tert-Butyl Ether
2-Butanone (MEK)
n-Hexane
Chloroform
Benzene
Carbon Tetrachloride
Cyclohexane
n-Heptane
Toluene
n-Octane
Tetrachloroethene
Chlorobenzene
Ethylbenzene
m,p-Xylenes
Styrene
o-Xylene
n-Nonane
4-Ethyltoluene
1,3,5-Trimethylbenzene
1,2,4-Trimethylbenzene
Naphthalene
17
45
11
13
13
11
22
11
13
17
53
18
11
11
20
25
14
22
32
18
18
25
20
27
10
1.4
17
1.4
1
1.6
0.8
2.9
1.2
1.4
1.7
0.74
1.1
1.2
2.3
1.2
1.2
0.95
0.95
1
1
0.735
7
2.9
0.37
4.5
0.38
0.27
0.41
0.21
0.77
0.32
0.35
0.28
0.2
0.29
0.3
0.61
0.23
0.3
0.25
0.27
0.27
0.27
0.25
180
26000
9.2
110
9.5
6.8
10
5.3
19
8.1
19
7.1
4.9
7.2
7.7
15
7.8
7.7
13
6.8
6.8
6.8
6.4
18
56
12
14
13
12
20
12
16
18
57
23
12
11
23
29
12
26
30
18
19
26
15
16
21
1.4
13.4
1.4
1
1.11
0.8
2.9
0.615
1.9
0.85
0.74
1.1
0.73
1.9
1.2
0.96
0.95
0.37
0.52
1
0.45
4.6
4.1
0.37
4.6
0.38
0.28
0.42
0.21
0.78
0.33
0.36
0.2
0.2
0.29
0.21
0.62
0.32
0.31
0.26
0.16
0.18
0.27
0.19
120
25000
5
150
5
5
5
7
16
5.4
110
5.3
18
5
16
17
13
5
12
5
5
5
5

Chemist and Detection Experts Forum – completed 5/11/12
•
Peer Review MCM content
•
Ensure data population complete and correct
•
Identify characterization gaps and possible risks

Medical Expert Incident Review – completed 5/25/12
•
Medical experts deployed to Boeing - Seattle
•
Review incident pilot data
•
Review incident pilot medical history

Investigative MCM Deep Dive – completed 6/8/12
•
Technical meeting for key members from MCM Team, Tox and
Doc Team, and Physio Team
•
Detailed review and assessment of contamination as a
potential cause
•
Identify and Prioritize remaining gaps
•
Recommend next actions
Legend:
Team Action
Data Team Action
Chemist Action
Medical Expert Action
Decision Point
Were any
samples
taken on
pilot or
jet?
NO
YES
Obtain
incident
specific
contaminan
t data
Develop
CNS
Hazard
Index for
each
incident
Review list of
top 10
compounds to
confirm validity
of CNS Hazard
Index
Review trends
and potential
source of
compounds
Review
medical data
and pilot
symptoms
Are pilot‘s
symptoms
consistent
with
contaminatio
n?
NO
Is Incident
CNS Hazard
Index less
than 1?
Symptoms
consistent
with
contamination
?
NO
YES
NO
Green
RCCA
YES
Contamination was
not a factor in the
incident
Is there a
probable
YES
explanation
for symptoms
in data?
NO
Green
RCCA
White
RCCA
Contamination was not a factor
in the incident
Insufficient data to conclude if
contamination was a contributor
YES
Red
RCCA
Contamination
caused the
event
Yellow
RCCA
Contamination
may have
contributed to
the event
◦ Development of CNS Hazard Index:
 Compound CNS Hazard Quotient = max level of
compound detected / ‖red‖ level
 Incident CNS Hazard Index = sum of all Compound CNS
Hazard Quotients
 An Incident CNS Hazard Index of 1 or greater would cause
CNS effects in pilots
 No Incident CNS Hazard Index, when adjusted, exceeded
0.3
 Adjusted example: IPA was subtracted from certain indices due to
artifact of post flight cleaning activity prior to sampling
 Team also considered effects of asphyxiants, metabolic
toxins, hemoglobin altering substances, and irritants
30
◦ Team reviewed a total of 21 incidents
◦ Data indicates that contamination is Not the root
cause to F-22 CNS symptoms
◦ Long term research studies would improve general
toxicological understanding of various aircraft
fluids
31
MBU-20/P Mask
HGU-55/P Helmet
Oxygen used to inflate
KMU-511/P helmet
bladder
Upper Pressure
Garment (UPG)
CRU-122 with
Integrated O2 Regulator
O2 to Mask
ATAGS connection
O2 to UPG
CRU-94 Integrated
Terminal Block (ITB)
UPG Over Pressure Vent
O2 from BRAG

ATAGS – Advanced Tactical Anti-G suit
◦
◦
◦
◦

Full body coverage
Pressure Suit functions as well
Human Testing up to 12-14 G‘s
No problems noted with F-22 Edwards prototype or
pre-production aircraft testing
JTAGs (Joint Tactical Anti-G suit) plus Combat
Edge
◦ Combined the advanced G-suit trousers with
Combat Edge vest
◦ Partial Pressure suit
Physiology Investigation
Med Team


No strong relationship
between incidents and
temperature/humidity
Relatively few high
temp incidents,
relatively few high temp
& high humidity
incidents
120
Centroid 1 Langley
Elmendorf
Centroid
1 Nellis
Centroid
2 Elmendorf
Holloman
80
Centroid 2 Holloman
◦ May be due to base
rather than weather
Langley
Centroid 2 Langley
Average Humidity

Centroid 1 Holloman
100
Still investigating
―periodicity‖ of events –
whether incidents are
more likely to occur
during certain months
Centroid
Nellis2 Nellis
60
Centroid 3 Elmendorf
Centroid 1
Centroid 3 Holloman
Centroid
3 Langley
Centroid
2
40
Centroid 3 Nellis
Centroid 3
Centroid 4 Elmendorf
Centroid
4 Holloman
Centroid
4
20
Centroid 4 Langley
Centroid 4 Nellis
Events
0
-40
-20
0
20
40
Average Temperature
60
80
100
120

Examine link between PT score (aerobic) and incident
likelihood, with PT score as proxy measure for VO2max
◦ Evidence inconclusive; not a strong enough relationship to
establish a link, but not weak enough to rule out


Bottom line: No definitive statement about relationship
between PT score and incident likelihood possible with
current data.
Additional findings:
◦ Analysis showed possible relationship with frequency of flying.
◦ Analysis showed no relationship between incidents and height,
weight, BMI, service component, or rank.


There are likely differences in event rates due to
AF base, Aircraft manufacturing block, or a
combination of both. However, it was not
possible to distinguish between the two.
Most definitive results: Tyndall and Block 10 are
statistically different than other bases/blocks
◦ No incidents in Block 10 or Tyndall, significantly lower
than others

Block 35 and Langley/Elmendorf had highest
incident rates
◦ However, most Block 35 sorties were at Langley and
Elmendorf; difficult to separate Block 35 from base

Based on 21 events
◦ Probability of ≥1 repeat pilot: 61.9%
◦ Probability of exactly 1 repeat pilot: 38.2%

Based on 24 events
◦ Probability of ≥1 repeat pilot: 70.0%
◦ Probability of exactly 1 repeat pilot: 40.0%

Interpretation: the distribution of incident
pilots is consistent with random chance



Overall, No strong evidence to conclude that immersion/Arctic
gear causes increased pilot HR – but needed a larger data base
F-22 pilots at Langley & Elmendorf show a lower average heart
rate (HR) than all other F-22 bases (Jan 2012 – May 2012), with
no strong overall trends from one month to another
Analysis by daily max temperature (instead of month) showed:
◦ No statistical clinical change in HR by temperature


Langley Jan-Apr vs. May: No statistical difference in HR during
May (average HR 88.6) vs. during cold months (average HR
89.3)
Elmo Jan-Apr vs. May: HR statistically lower in May (average HR
84.9) than in colder months (average HR 88.0)
80% of incident sorties had symptom onset at cabin
altitudes of 8000-9200 feet

◦ 8/10 sorties, one sortie had symptoms after flight and is
not counted
This cabin altitude corresponds roughly to aircraft
altitude of 8k-24k.

Symptom Onset vs Cabin Altitude - Post RTF Sorties
22,000
Cabin Altitude (4165)
Symptom Onset (4165)
Cabin Altitude (4138)
Symptom Onset (4138)
Cabin Altitude (4114)
Symptom Onset (4114)
Cabin Altitude (4112)
Symptom Onset (4112)
Cabin Altitude (4108)
Symptom Onset (4108)
Cabin Altitude (4173)
Symptom Onset (4173)
Cabin Altitude (4073)
Symptom Onset (4073)
Cabin Altitude (4161)
Symptom Onset (4161)
Cabin Altitude (4172)
Symptom Onset (4172)
Cabin Altitude (4060)
Symptom Onset (4060)
Cabin Altitude (4184)
Symptom Onset (4184)
20,000
CABIN ALTITUDE (ft)
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
0
10
20
30
40
50
60
70
80
90
100
110
120
T i m e (min)
130
140
150
160
170
180
190
200
210
220

Incident Rate increased
over time
Statistical analysis
pending
10
Axis Title

12
Incident Rate per 10,000 Sorties
8
6
4
2
0
F-22 Flying Conditions

Algorithm developed by 711 HPW to distinguish valid
data vs. poor data from Gz, stick input, oximeter artifact
◦
◦
◦
◦
◦
Amount of dropout in HR (heart rate) and SpO2 tracings
Steepness of desaturation
HR changes accompanying desaturations
Magnitude of desaturation
Variability in HR reading
HMPO has higher proportion
of sorties with high data
quality than finger-mounted
pulse ox
◦
◦
◦

High quality: Little to no dropout,
high SpO2 reading – definitive
conclusions can be drawn about
blood oxygen saturation
Marginal quality: Some dropout
and/or unexpected variability in
SpO2 reading – while some data are
usable, possible that definitive
conclusions would not be able to be
made
Low quality: High dropout and/or
unexpected variability in SpO2
reading – unlikely that definitive
conclusions could be made from the
data
80.0%
Proportion of Overall Sorties

70.0%
HMPO (n = 133)
67.7%
Finger PO (n = 138)
60.0%
50.0%
45.1%
40.0%
30.0%
30.1%
28.6%
16.5%
20.0%
15.8%
10.0%
0.0%
High
Marginal
Low
Pulse Oximeter Data Quality
Bottom Line: HMPO superior to finger-mounted pulse ox on all
metrics. HMPO is highly dependent upon appropriate helmet fit,
but provides overall better monitoring capability.

Compared pilot gear for incident sorties to gear for all non-incident sorties
◦ Gear for incident sorties obtained from wing safety
◦ Gear for non-incident sorties assumed Langley pilots wear immersion suit approx 1 Oct – 1
May, and Elmo pilot wear Arctic gear approx 15 Oct – 15 May
Findings:
◦ Arctic gear likely NOT associated with incidents; incident rate nearly identical for Elmo pilots
wearing Arctic gear vs. not wearing Arctic gear
◦ For Langley pilots, higher incident rate with poopy-suit than without poopy-suit, but not
enough evidence to state the difference is real; difference could be due to other factors such as
time of year
◦ There was little evidence to suggest Arctic gear is associated with incidents and very little
evidence to suggest poopy-suit is associated with incidents, but the number of incidents is
small at each base. If normalized across the fleet, higher incidents with climate control gear.
Elmendorf Events per 10,000 Sorties
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ATAGS, CEV, LPUs, Harness,
Flight Suit, with or without LPUs
ATAGS, CEV, LPUs, Harness,
Poopy-Suit, Flight Suit
Pilot Gear
Events per 10,000 Sorties
Langley Events per 10,000 Sorties
Events per 10,000 Sorties

7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
ATAGS, CEV, Survival Vest,
Harness, Black Jacket, Flight Suit
ATAGS, CEV, Survival Vest,
Harness, Flight Suit
Pilot Gear

Pilot fit checks discovered that numerous
flight crew ensembles were not fit according
to Technical Order Documents:
◦ 4 of 12 pilots wore wrong sized or ill-adjusted
UPGs;
◦ 3 of 12 pilots wore wrong sized or ill-adjusted
ATAGS;
◦ 12 of 12 helmets had issues with bayonets and chin
straps;
◦ 4 of 12 pilots wore ill-adjusted harnesses.
◦ Ill fitting gear worsened with use of extra garments
•Examined
In-flight respiratory symptoms
•
Neurologic symptoms
•
Neurologic + respiratory symptoms
•Combined
results from all sections (last
10 sorties and sorties ever) to increase
power
Findings



Of those who reported NOT ever having
RRS/cough, 2/36 (5.6%) reported having
abnormal in-flight symptoms.
Of those who DID report ever having RRS/cough,
19/86 (22.1%) reported having abnormal inflight symptoms.
Odds Ratio = 4.82. Compared to pilots who do
not experience cough/RRS, pilots with
cough/RRS have 4.8 times the odds of having
abnormal in-flight symptoms. Difference is
statistically significant, Χ2 p=0.027.
& In-Flight Symptoms
abnormal in-flight symptoms
•
Relationship Between Raptor Cough/RRS
Proportion of pilots reporting
connection between RRS/cough
and abnormal in-flight symptoms from
Aug 2011 F-22 Pilot Survey
25.0%
20.0%
15.0%
10.0%
5.0%
0.0%
Yes
No
Pilot ever report Raptor Cough/RRS?
Conclusions
•Pilots who experience
cough/RRS are more likely
to report having abnormal
in-flight symptoms



Proportion of sorties ≥90 minutes: 18%
Proportion of fight-pit-fight sorties: 20%
Average length of pre-sortie ground time:
30.2 minutes
Incident XX
Experienced
symptoms
Activated
EOS
Symptoms
relieved
Removed
mask
50
HAP/SIB
Gen Hoog
Hypoxia TIM 2
Hypoxia TIM 1
Incident Ex A
19 Apr
(Nellis)
Production
RCCA
2008
Incident 1 Incident 2
05 Jun
11 Aug
(Elmo)
(Nellis)
2009
Incident 3
19 Mar
(Langley)
Incident 4
13 Apr
(Langley)
Hypoxia Tim 3
Yeovil
25K Restriction
SAB
Incident Ex B Gen Martin
03 Mar
Class A
(Langley)
16 Nov
Stand Down
(Elmo) RCCA
2010
Unreported Incident 5
01 Oct
09 Mar
(Marietta) (Langley)
• OTI of fleet for shipping
plugs in MFV July 2008
• Removal of BYPASS in
BRAG Valve May-Aug
2009
Incident 6
22 Mar
(Elmo)
2011
Incident 7 Incident 9 Incident 10
16 Feb
18 Nov
27 Apr
(Nellis) (Langley)
(Elmo)
Incident 8
14 Dec
(Holloman)
• Flight Manual update to
manually select MAX at
30K’ Oct 2010
Incident 11
28 Apr
(Holloman)
Incident 12
03 May
(Elmo)
Incident 13
(Elmo)
03 May
Incident 14
A4044
03 May
(TY)
Incident Ex C
A4106 Gr
03 May
(HO)
Physio Incident/Mitigation Timeline
Incident 23 Incident 24 Incident 30
14 Mar
16 Feb
17 Feb
(Elmo)
(Elmo)
Incident 18 GR 5
GR 2
15 Nov
15 Nov
30 Sep
(Langley)
(HO)
(Tyndall)
GR 1
23 Sep
(TY)
GR 4
03 Nov
(Tyndall)
Incident 21 Incident 27
GR 7
14 Feb
1 Mar
14 Dec
(Elmo)
(Elmo)
(Tyndall)
RTF 21 Sep
2012
2011
GR 3
14 Oct
(Tyndall)
Incident 17
31 Oct
(Langley)
Incident 20 Incident 25 Incident 29
14 Dec
23 Feb
7 Mar
(Langley) (Langley)
(FF@TY)
Incident 15 Incident 16
20 Oct
20 Oct
(Langley) (Langley) Incident 19 Incident 22
15 Feb
14 Dec
(HO)
(HO)
Accommodations
RTF
• PulseOx
• Pilot and MX Baselines
• Response Protocol
GR 6
01 Dec
(Langley)
Incident 28
3 Mar
(Langley)
Incident 26
24 Feb
(TY)
Incident 22, Disregard GLOC
Incident 30, Disregard - CBleed Hot in flight
Detailed Chamber and Centrifuge Data


14 May 2012
Test Setup
◦ OBOGS in Max

Test Profile Options
◦ Standard equipment evaluation
 Gradual Onset Rate (GOR) ½ G per second
 Rapid Onset Rate (ROR) 6 G per second
 To 5/7/9 G with 10 second dwell at each
 Simulated Air Combat Maneuver (SACM) two peaks at 9
G
◦ 3 minute incident mission profile segment
◦ Operationally representative profiles
54
3/25/2014


16 April 2012
Test Setup
◦ OBOGS in Auto

Test Profile Options
◦ Standard Training Profiles
◦ Incident Profiles
◦ Operationally Representative Profile
55
3/25/2014
UPG Pressure
• UPG is designed to inflate during Positive Pressure Breathing (PPB) only
• During non-PPB operation, UPG should not inflate
• Test results show UPG fills and retains BRAG safety pressure at all times
• UPG pressure is often above mask pressure
• Pilots are forced to breathe against UPG restriction
6
Deep Breath #1
Deep Breath #2
4
InWg
2
Mask Pressure
UPG Pressure
0
Delta Pressure
Altitude: 8K
-2
Non-PPB Designed
UPG Pressure
-4
-6
230
235
Seconds
240
245
F-22 Baseline Configuration (w/ UPG), Mask-UPG Differential Pressure
UPG Pressure
• ASCC Breathing Standard Implications
• F-22 Baseline (wo/ UPG) appears to meet ASCC standard
(referenced to cabin ambient)
• F-22 Baseline (w/ UPG) does not meet ASCC (referenced to UPG
pressure)
2
ASCC Std
Exhalation
30
90
Inhalation
150
180
Flow Rate (alpm)
Mask Pressure, inWg
Mask Pressure (inWG)
ASCC Breathing Standard
10
5
0
-5
-10
F-22 Baseline wo UPG
Mask Pressure
F-22 Baseline (w/ UPG)
Delta Pressure
Altitude: 8K
0
-2
-4
*n=1
-6
0
20
40
60
80
100
120
140
Mask Flow, alpm
F-22 Baseline (w/UPG), F-22 Baseline w/o UPG Pressures
plotted against ASCC Standards
UPG pressure drives F-22 breathing resistance outside of ASCC standards
Work of Breathing
• F-22 Baseline w/o UPG had higher peak flows than F-22 Baseline (w/UPG) for
similar inhalation cycles
• UPG restricts pilot peak flow rate by one third
• UPG restricts thoracic expansion
• To maintain a similar tidal volume, the pilot must inhale longer
Deep Breath #1
4
Deep Breath #2
200
3
180
2
160
1
140
0
120
-1
100
-2
80
-3
60
-4
40
-5
20
-6
230
F-22 Baseline (w/UPG) Delta Pressure
lpm
InWg
F-22 Baseline w/o UPG Mask Pressure
F-22 Baseline w/o UPG Flow
F-22 Baseline (w/UPG) Flow
Altitude: 8K
0
232
234
236
238
seconds
240
242
244
F-22 Baseline (w/ UPG) vs. F-22 Baseline w/o UPG, Pressure – Flow Comparison
Pilots change inhalation patterns due to UPG effects

Compared to configurations
with no UPG, configuration
with UPG+Survival Vest has
significantly higher WOB


―Typical‖ WOB: 0.2-0.47
Joules/sec
Additional work from
UPG+Survival Vest is approx
0.5 Watts
Pre-G Mean (Joules/sec)
Pilot
4
6
7
8
9
10
12
E
-0.044
0.051
0.096
-0.026
-0.03
-0.017
0.24
0.038571
F
-0.024
-0.014
-0.028
0.53
0.116
G
1.246
0.526
0.332
0.387
0.408
0.478
0.43
0.543857
Pilot
4
6
7
8
9
10
12
Post-G Mean (Joules/sec)
E
F
G
-0.035
0.573
0.471
1.266
0.082
0.803
0.665
0.062
0.287
0.084
0.046
0.767
0.03
0.021
0.63
0.084
-0.002
0.517
0.197286 0.03175 0.691857
Work of Breathing
0.24 Joules/liter
1
E1 0.9 *UPG
0.3 Joules/sec
0
2 sec
65s
70s
75 s
Work [Joules]
-1
81s
no
UPG
-2
90s
6s non
11s non
1.1 Joules/liter
16s non
59 s non
-3
68 s non
71 s non
w/
UPG
-4
74 s non
1.3 Joules/sec
77 s non
-5
-6
0
0.5
1
1.5
2
Lung Volume [Liters]
2.5
3
3.5
4
Work of Breathing
E1
With UPG, Differential Pressure Factor of 1.0
Work/Time = 1.4 Joules/sec
Work/volume = 1.2 Joules/liter
Without UPG
Work/Time = 0.3 Joules/sec
Work/volume = 0.24 Joules/liter
Chest wall restriction has a significant reduction on the peak and
inspiratory flows. Miller et. al. showed that a 38-40% reduction in static
resting FVC (lung volume) was associated with a 20-30% reduction in
exercise capacity and Decreased Cardiac Output.
P-V Loops and Static Lung Loading
PSLL (static lung loading) = Pmouth – Pvest
1
0
P
Pmouth >
Pvest,
Positive static
load (easy
inhalation, hard
exhalation)
0
Pvest =
Pmouth,
No static load
cm H2O
10
Pvest > Pmouth,
Negative static load
(hard inhalation,
easy exhalation)
The external WOB is the same for each
case.
V, liters
Physiology
Root of the Problem


Multiple factors combining in various ways to
produce symptoms.
On ground – initial vulnerability is the high
Oxygen Content
◦ Leads to absorption atelectasis

High G loads
◦ Leads to acceleration atelectasis

Chest Wall Restriction – UPG
•
•
•
•
Inhibited inhalation
Prevents relief of atelectasis
Worsens recovery from G loads
May decrease cardiac output
• Multiple factors combining in various ways to produce
symptoms.
• C2A1 Filter - Removed from F-22
• Increased flow resistance to the mask
• Decreased lung ventilation
• Increases Functional Residual Capacity (unused lung
volume) and Respiratory Work per Minute
•
Theoretical - Ischemic hypoxia in the cerebral cortex
(reversible cellular damage) – Stagnant Hypoxia
• Decreased blood flow from various combination of sources
– High G Load, Shunting, Reduced Cardiac Output
• Vulnerable areas are the watershed areas – central cortex,
portions of the frontal cortex (working memory), and
hippocampus (episodic memory)

Breathing high percentage of O2 with OBOGS
operating in MAX
◦ Evidence: Medical reports indicate exposure to too high
O2 concentrations can result in atelectasis.
 Raptor incidents all have occurred with OBOGS operating in
Max (by selection or due to cockpit altitude >11K).
 Prior to Nov 2010 F-22 fleet spent ~24% of flight time above
28K – After Nov 2010 pilots changed to pro-actively select MAX
and reported incidence rate increased ~4 times.
 F-18 operates in MAX with comparable incident reporting rate.
Other USAF fighter platforms use dilution regulators – Markedly
less incidents reported. European platforms with OBOGS use
variable charge/vent ratios to provide just adequate O2 vs.
more than enough – Markedly less incidents reported.

What levels of reduced vital capacity are
feasible with the physiologic factors that were
described?
◦ Hyperoxia: 10 % reduction in vital capacity due to
atelectasis related to hyperoxia exposure (100%) for
30 minutes
◦ Acceleration Atelectasis: 20% persistent reduction in
vital capacity due to Gz of 4.5 to 9.0 in fighter pilots
and transient reductions of 28% were reported for
4.5 Gz and 25% for 9.0Gz SACM 4
◦ C2A1 Filters and Work of Breathing: 10% Internal
inspiratory restrictions greatly affected the WOB for
pilots in centrifuge runs, where the physical
workload is less than that of live jets





Central nervous system toxicity is caused by short exposure to
high partial pressures of oxygen at greater than atmospheric
pressure.
Pulmonary toxicity occurs with exposure to partial pressures of
oxygen greater than 0.5 bar (50 kPa), corresponding to an
oxygen fraction of 50% at normal atmospheric pressure.
At partial pressures of oxygen of 2 to 3 bar (200 to 300 kPa)—
100% oxygen at 2 to 3 times atmospheric pressure—pulmonary
symptoms may begin as early as 3 hours after exposure to
oxygen.
Decrements in vital capacity (lung volume) of up to 20 percent
have also been noted after hyperoxic exposure in a number of
experiments. This is presumably due to a combination of
absorptive atelectasis and shallow breaths secondary to pleuritic
(i.e., chest wall) pain (due to tracheobronchitis).
Hyperoxia increases aortic pressure and systemic vascular
resistance and decreases cardiac index, stroke index, oxygen
consumption, and oxygen transport.


Oxygen requirements – balance of requirements
◦ 100% Oxygen is a requirement with altitudes in excess
of 33,000 ft.
◦ Below 18,000 ft. can give rise to symptoms such as
cough, retrosternal pain
◦ At lower altitudes under pressure can lead to ear
discomfort and decreased hearing
Preferential with high G load to have higher partial
pressures to combat the metabolic and physiologic needs
◦ During high G loads, 100% Oxygen associated with
collapse of the basal lung segments (acceleration
atelectasis), giving rise to chest pain, cough, and
dyspnea. Symptoms are aggravated by the use of anti-G
trousers, but prevented by the presence of at least 40%
nitrogen in the inspired gas.
Raptor Cough
Hyperoxia effects and Atelectasis


Noticeable during a debrief
Airborne staccato cough
◦ Increases airway resistance
◦ Atelctatic reset – expanding segments
◦ Possible hyperoxia effect

Chronic cough on the ground
◦ Single intermittent
 Hyperoxia
 Extinguished with time or extended ground rotation
and return to the aircraft
Life Support System
OBOGS and beyond
F-22A
OBOGS CONTROL AND WARNING DESIGN


Pressure drops in the line between the BRAG
valve and mask can cause resistance to pilot
inhalation.
Was not detected in incidents, but system
needs full experimentation.
In flight and Ground Oxygen System Evaluation
Bottles Collected to the Oxygen System and Cabin for Collection
Two variables
impact measured
OBOGS O2 output:
unit serial number
(s/n) and ambient
temperature.
◦ Not all OBOGS units
perform the same.
◦ For every 10 degree
increase in
temperature, there is
an increase of 1.3%
in measured OBOGS
O2 output
mean O2 = 86.8
Edwards
Elmendorf
Hickam
Hill
Holloman
Langley
Marietta
Nellis
Palmdale
Tyndall
100
95
90
OBOGS %O2

ANOCOV: slope = 0.13, r = 0.47, p = 0.0001
85
80
75
70
-10
0
10
20
30
40
50
60
Ambient Temperature (deg F)

70
80
Bottom line: little evidence to support variation in
OBOGS performance over time
90



The F-22 OBOGS unit is a highly capable air separation system
that can provide O2 at the desired flow rates and concentrations.
As demonstrated in qualification and acceptance tests, and
against sinusoidal waveform breathing simulators, the OBOGS
met delivery and purity requirements at all flow and
concentration ranges.
In tests, a very large fraction of hydrocarbons were rejected to
the nitrogen stream and only small fraction of those retained
over the bed. Further challenge of the bed (laden with these
hydrocarbon compounds) with moist gas also showed very little
displacement, suggesting the capability of the air separation
sorbent in preventing the leakage of these compounds into the
breathing air provided to the pilot.
In addition to the heavy hydrocarbon fractions, the volatile
organic compounds (VOCs) and inorganic contaminants (such as
sulfur and nitrogen oxides) may also be removed by the OBOGS
to a significant extent.

Life support system components (e.g.,
OBOGS, masks, valves) had all been
individually qualified, but the system was not
fully tested as an integrated system.
Carbon Monoxide
Can‘t get that through Zeolite
Summary
Lessons Learned



LSS, ECS and AFE are often treated as separate
systems and controlled at the interfaces. The
events experienced, however, are a result of the
complex interactions of these systems, and the
pilot.
If there are pressure drops in the line between
the BRAG valve and mask, they can cause
resistance to pilot inhalation.
There was a lack of sufficient human-systems
integration (HSI) testing before operational
deployment of the F-22. For example: Air Crew
Flight Equipment (AFE) currently in use was not a
part of the original testing of the F-22.

The teams found no evidence of a
contaminant producing a toxic exposure for
pilots flying the F-22. However, there is
potential for the pilot to be exposed to
irritant compounds expected in a jet fighter
environment.



Life support system components (e.g., OBOGS, masks, valves)
have all been individually qualified but have not been fully tested
as an integrated system.
The investigation process did not effectively engage with the
operational flight community over the course of the
investigation. Also, the investigation team‘s need for consistent
data from the operational community on incident events and
pilot post- incident data harvesting was not effectively
communicated to the operational wings.
The F-22 pilot community came to accept a number of
physiological phenomena as a ―normal‖ part of flying the Raptor.
These include the ―Raptor cough,‖ excessive fatigue, headaches,
and delayed ear blockages. The acceptance of these phenomena
as ―normal‖ could be seen as ―normalization of deviance.‖ This
was an early indicator of problems



Pilot interviews were very revealing
The Navy appears to have a significant number of
hypoxia events compared to the USAF. The Navy‘s
recent study ―In Flight Hypoxia Events in Tactical Jet
Aviation 2010‖, reported that ―Of the 566 aviators who
completed the survey, 112 (20%) reported experiencing
hypoxia symptoms in tactical jet aircraft‖ (Reference
15). The root cause of most of these events on the F18 fleet is ―unknown‖.
The OBOGS has inherent capability to filter Carbon
Monoxide and Carbon Dioxide. The measured levels of
COHb are not adequate to induce the types of CNS
effects observed. Nevertheless, the Navy is
supplementing the F-18‘s OBOGS by adding Carbon
Monoxide filtering capability to the existing OBOGS.

A small US Air Force working group was
aware of the potential issues years before the
actual accidents took place. The working
group formed in 2005 even proposed a series
of fixes to prevent the hypoxia and breathing
difficulties.
Ultimately it was all down to the human
machine interface
Priority #1
Boy what an adventure !

Central nervous system toxicity is caused by
short exposure to high partial pressures of
oxygen at greater than atmospheric pressure.
◦ Pulmonary and ocular toxicity result from longer
exposure to elevated oxygen levels at normal pressure.
◦ Symptoms may include disorientation, breathing
problems, and vision changes such as myopia.
◦ Prolonged exposure to above-normal oxygen partial
pressures, or shorter exposures to very high partial
pressures, can cause oxidative damage to cell
membranes, the collapse of the alveoli in the lungs,
retinal detachment, and seizures.
◦ Oxygen toxicity is managed by reducing the exposure to
elevated oxygen levels. Studies show that, in the long
term, a robust recovery from most types of oxygen
toxicity is possible.

Pulmonary toxicity occurs with exposure to partial pressures of oxygen
greater than 0.5 bar (50 kPa), corresponding to an oxygen fraction of
50% at normal atmospheric pressure.
◦ Signs of pulmonary toxicity begins with evidence of tracheobronchitis, or
inflammation of the upper airways, after an asymptomatic period between 4 and 22
hours at greater than 95% oxygen,[with some studies suggesting symptoms usually
begin after approximately 14 hours at this level of oxygen.

At partial pressures of oxygen of 2 to 3 bar (200 to 300 kPa)—100%
oxygen at 2 to 3 times atmospheric pressure—these symptoms may
begin as early as 3 hours after exposure to oxygen.
◦

Experiments on breathing oxygen at pressures between 1 and 3 bars (100 and
300 kPa) show that pulmonary manifestations of oxygen toxicity are not the same for
norm baric conditions as they are for hyperbaric conditions. Evidence of decline in
lung function as measured by pulmonary function testing can occur as quickly as 24
hours of continuous exposure to 100% oxygen,[with evidence of diffuse alveolar
damage and the onset of acute respiratory distress syndrome usually occurring after
48 hours on 100% oxygen.
Breathing 100% oxygen also eventually leads to collapse of the alveoli
(atelectasis), while—at the same partial pressure of oxygen—the
presence of significant partial pressures of inert gases, typically
nitrogen, will prevent this effect.

Hyperoxia increases aortic pressure and
systemic vascular resistance and decreases
cardiac index, stroke index, oxygen
consumption, and oxygen transport.
◦ Hyperoxia increased SVRI -Systemic Vascular
resistance Index (20%) and reduced HR (-10%),
Cardiac Index (−10 % ), and stroke index (SI) (−7% )
but had no effect on AI (Arterial Stiffness Index)
◦ The effects of hyperoxia on CI and SVRI, but not the
other hemodynamic effects, persisted for up to 1 h
after restoration of air breathing.


In 2008 the F–22 began to experience a significantly
higher rate of hypoxia-like incidents with unknown
causes, as reported by the pilots. At that point, the
Air Force initiated what I will refer to as a four-tier
approach to finding the root cause for these
unexplained physiological incidents.
The first tier was a collaborative effort between the F–
22 system program office, the prime contractor and
its key subcontractors responsible for the
components of the F–22 life support system, and the
normal Air Force safety investigation structure. So
that collaborative effort started a process we have
come to know as the Root Cause and Corrective
Action [RCCA] analysis process that has continued 5
years.


The second tier was initiated after preliminary results
of the tragic fatal F–22 mishap that occurred in
November of 2010. When that mishap was outbriefed to the senior leadership in January of 2011,
the Air Combat Command established a Class E
safety investigation mishap board. That board was
chaired by an Air Force Major General, and it was
chartered to review all F–22 reported hypoxia-like
incidents. So, in conjunction with the RCCA team, or
the Root Cause and Corrective Action Analysis Team,
this safety investigation team developed and
implemented a multitude of tests and challenges to
each of the F–22s life support system components.

And after two troubling incidents in May of 2011,
the Air Force grounded the fleet of F–22 aircraft.
At that point, the Safety Investigation Board,
which had been unable to determine a failure
mode that might lead to the hypoxia-like events,
recommended that the Air Force modify one of
its test aircraft with a specialized array of sensors
and then execute a carefully developed series of
flight test profiles to determine if the root cause
could be assessed in the dynamic flight
environment as opposed to the ground testing
that had been done to that point.

Further, as a part of their investigation, the Safety Board determined there were
decisions made during the engineering, manufacturing and development phase of
the F–22‘s development that should be reviewed from a broader perspective, and
they recommended a broad area review of the F–22 program be conducted. So, in
June of 2011, the Secretary of the Air Force and the Chief of Staff of the Air Force
tasked the United States Air Force Scientific Advisory Board to perform a quicklook study on aircraft oxygen generation systems and to cover three areas: First,
continue the ongoing efforts to determine the root cause, to include gathering
data during dynamic in-flight testing, full reviews of both the life support
equipment and the aircraft‘s potential for passing contaminants into the cockpit
and/or the breathing air, and finally, to better understand the similarities and
differences between the F– 22 oxygen generation system and other military
aircraft; second, to better understand the conditions that would create hypoxialike symptoms at altitudes not normally associated with hypoxia, along with an
evaluation of the guidance associated with breathing air standards and the human
response to operating in the F–22‘s extraordinary envelope with less than 90
percent supplied oxygen; third, to review the policies, processes and procedural
changes that occurred during the F–22‘s development and fielding phase to
evaluate the implications with respect to design limitations, risk analysis, program
execution and the acquisition workforce. The study began in June of 2011, with
interim status reports provided to Secretary and the Chief until the final briefing
was approved by the entire Scientific Advisory Board and delivered to the Secretary
and the Chief on the 24th of January 2012.

The F–22 Restrictive Breathing Working
Group‘s hypothesis one, oxygen quantity,
describes the major contributor to the
previously unexplained physiological
incidents reported by F–22 pilots over the
past few years. The task force is confident
that the hypothesis two, oxygen quality, is
not the root cause of previously unexplained
physiological symptoms reported by F–22
pilots and ground crew.
ALTITUDE
(FEET)
BAROMETRIC
PRESSURE
(mmHg)
Sea level
104
760
97
10,000
67
523
90
20,000
40
349
70
30,000
21
226
20
ALVEOLAR
OXYGEN
( PAO2)
HEMOGLOBIN
SATURATION
% (Hb)