DECOMPRESSION

1
DECOMPRESSION

• OBJECTIVES
• To Increase Awareness Of The Potential Dangers
  Associated With Rapid Or Explosive Decompression.
• How To Be Prepared To Deal With Such An Event.

2
Boeing 307 Stratoliner
The First Airliner With A Pressurised Cabin
3
ADVANTAGES OF A PRESSURISED CABIN

• Flight Operations Above FL250
• Dispense With The Need To Wear Oxygen Masks
• Much Quieter Cabin
• Unprecedented Comfort
• Combined With The Introduction Of Jetliners The
  Associated Improvement In Safety And Lower
  Traveling Cost , Were Responsible For The
  Take-Off Of Mass Air Transportation In The Late
  1950s

4
DISADVANTAGES

• In The Event Of A Rapid Decompression
• Exposed To The Danger Of Hypoxia
• Possible Decompression Sickness
• Gastrointestinal Gas Expansion and Hypothermia
• Possibility Of Cyclonic Winds Sucked Out Of
  Cabin
• Other Physical Injuries Due To Flying Debris

5
SOME INFAMOUS ACCIDENTS

• BOAC Comet-1 YP (10.01.54) - Crashed
• AA DC10 Flt 96 (12.06.72) - Landed safely
• TA DC10 Flt 981 (03.03.74) - Crashed
• UA DC10 Flt 232 (19.07.89) - Crashed
• JAL B747 Flt 123 (12.08.85) - Crashed
• Aloha B737 Flt 243 (28.04.88) - Landed safely
• UA B747 Flt 811 (24.02.89) - Landed safely
• BA BAC111 Flt 5390 (10.06.90) - Landed safely
• Sunjet Aviation L35 (25.10.99) - Crashed
• CAL B747 Flt 611 (25.05.02) - Crashed

Source Aviation Safety Network
6
UNITED B-747 FLIGHT 811
7
ALOHA B-737 FLIGHT 243
8
DALTONS LAW OF PARTIAL PRESURE

• The Partial Pressure Exerted By Each Individual
  Gas In A Mixture Of Gases Is Independent Of The
  Pressure Of The Other Gases, and
• The Total Pressure Pm Exerted By A Mixture Of
  Gases Is Equal To The Sum Of The Partial
  Pressures Of All Gases

9
TIME OF USEFUL CONSCIOUSNESS
Source Fundamentals Of Aerospace Medicine
10
PHYSICAL CHARACTERISTICS OF EXPLOSIVE OR RAPID
DECOMPRESSION

• (Based On Actual Accounts RSAFs Hyperbaric
  Chamber Training Experience)
• Loud Explosion Loud Noise
• Fogging Up Due To Condensation
• Dust Particles Debris Flying Around
• Sudden Drop In Temperature Due To Sudden Drop In
  Cabin Pressure
• Sudden Expansion Of Air Trapped In Your Lungs
• Rush Of Air Whooshing Sound or Cyclonic Winds
  Out Towards The Ruptured Area

United B747 Flight 811, Aloha B737 Flight 243
BA BAC-111 Flight 5390
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FACTORS CONTROLLING THE TIME RATE OF
DECOMPRESSION

• Volume Of Pressurised Cabin
• Size Of Opening
• Pressure Ratio
• Pressure Differential

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PHYSIOLOGICAL EFFECTS OF RAPID OR EXPLOSIVE
DECOMPRESSION

• Lungs
• Ears Sinuses
• Gastrointestinal Tract
• Hypoxia
• Decompression Sickness
• Hypothermia

13
THE SIGNIFICANCE OF FL250

• With 100 Supplemental Oxygen, Hypoxia Is
  Checked.
• Prolonged Flight At FL250 With Unpressurised
  Cabin Even With 100 Oxygen - Will Not Prevent
  Possible Decompression Sickness.
• Time Of Useful Consciousness Is About 2 to 3
  Minutes.
• Cruising At FL250 Burns Significantly Less Fuel
  Than At 10000ft.

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SIMULATOR TRAINING CONSTRAINTS

• Only Able To Simulate Realistic Instrument
  Indications, System Failures And With Credible
  Sound Effects.
• Unable To Simulate Sudden Drop In Temperature,
  Condensation, Flying Dust Particles Associated
  Cyclonic Winds And Sudden Lung Expansion Of
  Occupants.
• Absence Of Dramatic Shock Effect.

15
HYPERBARIC CHAMBER TRAINING

• Realistic Simulation Of Virtually All
  Physiological Effects.
• Training Is Done By Qualified Flight Surgeons And
  Technicians Very Safe.
• Pilots With Hyperbaric Chamber Training
  Experience Should Better Appreciate The Onset
  Associated Effects Of Rapid Decompression.
• Every Chamber Run Is An Unforgettable Personal
  Experience.

16
A TYPICAL HYPERBARIC CHAMBER
Every RSAF Fighter Transport Pilot Requires To
Undergo Hyperbaric Chamber Refresher Training
Once In Every 3 Years
17
A TYPICAL TRAINING PROFILE
18
CREW O2 MASK REGULATOR
19
TECHNICAL CREW O2 REQUIREMENTS
With 100 Oxygen Setting, An Intermediate Level
Off Altitude Of Up To 18,000ft Followed By 3
Hours Post Decompression Time At 14000ft, The
Endurance For

• 2 Crew Is 4hrs And 27 mins
• 3 Crew Is 2hrs And 38 mins
• 4 Crew Is 1hr And 43 mins

Extracted From B744 Supplementary Procedures
20
ALTITUDE EFFECTS OXYGEN REQUIREMENTS
Simplified Table - Source United States Naval
Flight Surgeon's Manual
21
B747-400F FIRE SUPPRESSION MAIN DECK, FWD
AFT COMPTS
22
REMEMBER!

• The B747-400F Main Deck Has No Fire Fighting
  Capability!

23
B744F MAIN DECK CARGO COMPT IS CLASS E COMPLIANT

• It must be completely lined with fire-resistant
  material.
• It must have a separate system of an approved
  type smoke or fire detector to give warning at
  the pilot or flight engineer station.
• It must have a means to shut off the ventilating
  air flow to or within the compartment and the
  controls for that means must be accessible to the
  flight crew in the crew compartment.
• It must have a means to exclude hazardous
  quantities of smoke, flames, or noxious gases
  from entering the flight crew compartment.
• Required crew emergency exits must be accessible
  under all cargo loading conditions.

Source FAR 121.221
24
CREW PAX O2 SYSTEMS

• The flight crew system comprises two 114 cubic
  foot bottles. At dispatch pressure of 1650 psi at
  21 C, the oxygen supply available for the flight
  is approximately 5,350 liters.
• The passenger oxygen system comprising nine 114
  cubic foot bottles, supplies free flow to 550
  masks. At dispatch pressure of 1650 psi at 21 C,
  the oxygen supply available for the flight is
  approximately 24,350 liters.

Extracted From B744 Supplementary Procedures
25
OXYGEN-CONSTRAINED ROUTES
FAR 121.329 JAR-OPS 1.780

• For flights at cabin pressure altitudes above
  10,000 feet, up to and including 14,000 feet,
  there must be enough oxygen for that part of the
  flight at those altitudes that is of more than 30
  minutes duration, for 10 of the passengers.
• 14000 to 15000ft 30
• Above 15000ft 100

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PAX CABIN O2 REQUIREMENTS FAR 121.329
JAR-OPS 1.780
27
OXYGEN-CONSTRAINED ROUTES

• Afghanistan V390, L750 N644
• Near The Vicinity Of Caucasian Mountain Range
  Georgia, Armenia Azerbaijan UR315, UN644,
• Iran G202, UL223, UP574, UL852, UL125, UL124
• Highest MSA Enroute UL125 N644 - FL190

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BRIEFING TO CREW-IN-CHARGE

• Company Supplementary Procedures

When Flying Over The O2-Constrained Routes In The
Event Of An Explosive Decompression
Special Cabin Crew Actions And Post
Decompression Drills
10,000ft -12,000ft 10 12,000ft -15,000ft
30 15,001ft And Above All
Extracted From B744 Supplementary Procedures
29
PAX O2 REQUIREMENT COMPUTATION

• Terrain clearance is based on MSA, which is
  2500ft above the highest terrain within 20nms
  either side of airway centerline.
• Critical Point is based on NIL wind. For every
  10kts wind component, the critical point moves
  into wind by 2nms.
• Emergency descent at MMO/VMO.
• Cruise speed at VMO
• Oxygen pressure is read from the status page.
• Oxygen quantity required is in liters for all
  endurance calculations.
• The total number of masks onboard the aircraft is
  550.
• For the designated routes, oxygen CPs have been
  established and the escape routes are defined in
  the attachments.
• The flight crew oxygen system endurance is
  adequate for the designated routes.
• If the actual route or profile differs from the
  planned routes provided, oxygen requirement can
  be determined using the tables in the Flight
  Planning Manual.

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DURATION OF OXYGEN (B744)
In The Event Of Depressurisation At FL390
Extracted From B744 Supplementary Procedures
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UL125
32
UL125
33
UL125
34
UL125
35
R654
36
R654
37
V390
38
V390
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L750
40
L750
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RAPID DESCENT

• This maneuver is designed to bring the airplane
  down smoothly to a safe altitude, in the minimum
  time, with the least possible passenger
  discomfort.
• If structural damage exists or is suspected,
  limit airspeed to current speed or less. Avoid
  high maneuvering loads.

42
RAPID DESCENT (FCTM)
43
LANDING GEAR UP Vs DOWN
44
ALTIMETER SETTINGS

• When QNE Of 1013.25hPa Is Set
• Under ISA Conditions Indicated Altitude And
  True Altitude Is The Same
• Under ISA Conditions Airplane Is Flying Higher
  Than Indicated Safe
• Under ISA Conditions Airplane Is Flying Lower
  Than Indicated Dangerous

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BELOW TRANSITION LEVEL

• If Area QNH Is Higher Than 1013.25hPa The
  Airplane Is Flying Higher Than Indicated Safe
• If Area QNH Is Lower Than Indicated The Airplane
  Is Flying Lower Than Indicated Dangerous
  Altimeter Must Be Reset

49
MINIMUM SECTOR ALTITUDE (MSA)

• LIDO Computerised Flight Plan Definition
• Minimum Safety Altitude for the segment
• It is calculated using the worldwide terrain
  database and padded with a safety margin. The
  margin is 2000ft for terrain below 8000ft and
  2500ft for terrain equal to or greater than
  8000ft.
• All terrain within 20nm either side of the
  segment centerline is considered plus a turn
  radius to cater for turning. If the MSA is above
  10000ft, an asterisk will be mark against it.

Extracted From LIDO Flight Plan Manual
50
DISPATCH WITH PASSENGER OXYGEN SYSTEM INOPERATIVE

• MEL Allows To Dispatch Provided The Following 5
  Conditions Are Satisfied
• Flight Planned Not Above FL250
• MSA Enroute Does Not Exceed FL140
• Pressurisation System Operative
• Portable Oxygen Carried For 10 Of Pax
• Passengers Are Briefed

Crew Have 4 Minutes To Descend To lt14,000ft.
See B744 MEL Chapter 35.21.1
51
CREW OXYGEN DEPLETION AND ACTIONS DURING CRUISE
PHASE

• Descend To FL250 Initially
• TOU Is 2-3 Minutes At FL250
• Checked Fuel Remaining On Board
• Compare Air Miles At FL250 10000ft
• Check Enroute MSA
• Check Enroute Alternates
• Decide Course Of Actions
• Revise Rapid Decompression Drills

Source Decision Making In The Cockpit By
Professor Judith Orasano
52
COMMUNICATIONS AFTER RAPID OR EXPLOSIVE
DECOMPRESSION

• The flight deck noise level is extremely high,
  the Pilot-Pilot and Pilot-ATC communications can
  be extremely difficult or impossible.
• It may be a good idea to keep the oxygen masks on
  for better Pilot-Pilot Pilot-ATC
  communications.
• Insist to ATC not to switch frequency to
  prevent loss of Pilot-ATC communications.

NTSB Findings Of ALOHA B737 Flight 243
53
APPROACH LANDING CONSIDERATIONS

• Fly LRC At 14,000ft Or 10,000ft
• On Initial Approach, Descend At 500fpm To
  Minimise Further Injuries To Ears/Sinuses And To
  Prevent Further Discomfort.
• Begin Approach At 10,000ft From At Least 80nm
  From Landing Runway.
• At 240kt Initial Approach Speed, It Takes At
  Least 20mins 80nm To Descend From 10,000ft To A
  Sea-level Airport.

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DAMAGE ASSESSMENT AND LOW SPEED HANDLING
CHECKS

• Carry Out The Actions At 10,000ft AMSL
• Reduce Speed At Maximum 20kt Decrements
• Select Each Appropriate Flaps Setting
• Stop At The Onset Of Buffeting
• No More Than 15 Angle Of Bank
• Increase Back 20kt Final Approach Speed
• If Aircraft Rolls Or Incipient Stall Develops,
  Recover The Airplane As Per QRH Actions

Extracted Modified From B744 FCTM
55
SUGGESTED FURTHER READINGS

• United States Naval Flight Surgeon's Manual
  Third Edition 1991 Chapter 1 Physiology of
  Flight. Naval Aerospace Medical Institute.
• Rapid Decompression Creative Thinking
  Problem Solving In Flying Papers Written By
  Capt Eddie Foo.
• CRM By Dr. Robert L. Helmreich.
• Accident Investigation Reports On UA Flight 811,
  ALOHA Flight 243, BA BAC-111 Flight 5390
  Others.
• A visit To Aeromedical Centre Paya Lebar

56
AEROMEDICAL CENTRE

• The Aeromedical Centre (Paya Lebar) Is Prepared
  To Conduct An Introductory Hyperbaric Chamber
  Training For SIA Pilots At Cost Price Of S3000/-
  Per Session.
• Each Session Can Accommodate Up To A Maximum Of
  16 Pilots.
• For Further Details You May Contact
• Dr. Richard Tan richard_tan_at_aeromedicalcentre.com

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THINK OUTSIDE OF THE BOX!

• There Is Plenty Of Light And Life Out There!

58
THE END

• For Further Information,
• Please Write Directly To
• Capt Eddie Foo S N

eddiefoo_at_starhub.net.sg
9th April 2005