History of Pressurized Cabins

1943

Post-war piston airliners such as the Lockheed Constellation (1943) extended the technology to civilian service. cabin pressurization enabled the Constellation to have certified service ceilings from 24,000 ft to 28,000 ft.

1942

1949

The world’s first commercial jet airliner was the British de Havilland Comet (1949) designed with a service ceiling of 36,000 ft (11,000 m). It was the first time that a large diameter, pressurized fuselage with windows had been built and flown at this altitude. Initially, the design was very successful but two catastrophic airframe failures in 1954 resulting in the total loss of the aircraft

World War II was a catalyst for aircraft development, led to the first bomber with cabin pressurization (though restricted to crew areas), the Boeing B-29 Superfortress.

1938

The first airliner with a pressurized cabin was the Boeing 307 Stratoliner, built in 1938, prior to World War II, though only ten were produced.

Advent of Ground Testing

of Pressurized Fuselages

Extensive investigation and groundbreaking engineering analysis of the wreckage led to a number of very significant engineering advances that solved the basic problems of pressurized fuselage design at altitude. The critical problem proved to be a combination of an inadequate understanding of the effect of progressive metal fatigue as the fuselage undergoes repeated stress cycles coupled with a misunderstanding of how aircraft skin stresses are redistributed around openings in the fuselage such as windows and rivet holes.

1935

The End

The XC-35 was a development of the Lockheed Model 10 Electra per a 1935 request by the United States Army Air Corps for an aircraft with a pressurized cabin.

Why fly higher?

• Military advantages in combat
• Fuel efficiencies
• Reduced turbulence = Passenger comfort

Industry wide changes in fatigue analysis help increase safety worldwide

1921

- Repair Assessment Program

- Corrosion Control Prevention Program

- Supplemental Structural Inspection Program

- High Cycle Fatigue

- Damage Tolerance Assessment

- Limit of Viability for Legacy A/C

Airco DH.9A - the first aircraft to fly with a pressurized cockpit module.

Notable Aircraft Fatigue Failures

-Two de Havilland Comet passenger jets broke up in mid-air and crashed within a few months of each other in 1954.

The Need

1918

Above 12,500 to 14,000 ft

* Hypoxia

* Altitude sickness

* Decompression sickness

* Barotrauma

WWI we had 55 planes. French Designer Georges Lepere designed a two-seat escort fighter.

Pressurized Cabins

creates a safe and comfortable environment for aircraft passengers at high altitudes

-The 1988 Aloha Airlines Flight 243 suffered an explosive decompression due to fatigue failure of an improper repair.

-The 1985 Japan Airlines Flight 123 crashed after the aircraft lost its vertical stabilizer due to faulty repairs on the aft pressure bulkhead.

Cabin Altitude

An empty bottle, closed during a commercial flight with a cabin altitude of around 8,000 ft, is crushed by the pressure at ground level after descent.

Pressurized Cabins

Mechanics of Pressurization

Outflow Valve & Pressure Relief Valve

Pressurization is controlled by an ECS (Environmental Control System). The most common source of compressed air is from the compressor stage of a gas turbine engine called bleed air.

Unplanned Decompression

Aft Pressure

Bulkhead

Any failure of cabin pressurization above 10,000 ft requires an emergency descento to 8,000 ft and the deployment of an oxygen mask for each seat.

by Manny Parras

&

Ben Johnston