Experiments in aircraft pressurisation were being conducted as far back as the early 1900s when aircraft were being constantly pushed to reach high altitudes.
In 1920 a Packard-Le Pere biplane reached a ceiling of over 37,000ft above McCook Field in Dayton Ohio. Piloted by Lt John Macready, oxygen was released directly into the enclosed cabin rather than an oxygen mask but as greater heights were achieved, the lack of atmospheric pressure at high altitudes resulted in a pilots heart enlarging and significant health issues.
While the first airliner to feature a pressurised cabin was a Boeing 307 Stratoliner built in 1938 it was the outbreak of WWII that really became the catalyst for aircraft development and pressurisation.
While piston engined aircraft were attaining higher and higher altitudes, very few cockpits were pressurised with pilots relying on their oxygen masks.
For large bombers where crew were required to move about the aircraft, a bailout oxygen bottle was carried or the crew member plugged into an oxygen line running the length of the aircraft.
While this worked for a while it became increasingly impractical and it was not until the production of the high latitude Boeing B-29 Super-fortress that a fully pressurised crew compartment was introduced.
The pressurised control system for the B-29 was developed by the Garrett AiResearch Manufacturing Company who went on to develop more advanced systems for post-war airlines such as the Lockheed Constellation.
For piston engined aircraft like the Douglas DC-6 and DC-7 the aircraft relied on engine supercharging to provide pressurised cabin air but with the advent of the jet airliner, with a significant increase in cruise altitudes, advanced aircraft engineering, design and construction were still struggling to come to terms with the stresses imposed on a fuselage with full pressurisation at such high altitudes.
A tragic example of this was the British de Havilland Comet.
Entering service in 1949, the Comet could cruise at over 36,000ft and was the first large diameter pressurised fuselage with banks of windows to be flown at this altitude.
While initially lauded as a breakthrough in passenger comfort and aircraft design, the Comet suffered two catastrophic airframe failures in 1954 resulting in the total loss of the aircraft and all passengers and crew.
Panic swept across the airline industry and resulted in the temporary grounding of a significant part of the world’s airline fleet as engineers struggled to understand what went wrong.
After extensive investigation and close analysis fo the wreckage using new engineering diagnostics, engineers discovered that the overriding problem was an inadequate understanding of the effects of progressive metal fatigue as the aircraft's fuselage underwent repeated stress cycles and the misunderstanding of how skin stresses are distributed around openings in the fuselage such as windows and rivet holes.
One legacy of these investigations is the oval windows we now see in commercial jet liners. The Comet windows were almost square in their design, which lead to cracking and failure at their corners. Another legacy was the introduction of thorough visual inspections of the outer skin, mandatory stress sampling of components and the introduction of radiography to detect cracks and flaws too small to be seen by the naked eye.
The Comet was redesigned but never really recovered from the two disasters and was soon superseded by the newer Boeing 707.
Unfortunately further catastrophic failures continued to occur - all traced back to issues relating to cabin pressurisation and airframe fatigue.
One of the most widely publicised examples of this was Aloha Airlines Flight 243 involving a Boeing 737.
The 737 had been flying continuous short routes which saw it accumulate over 35,496 flight hours prior to the accident - this also included 89,680 flight cycles (takeoffs and landings) - almost twice the number of cycles the airframe was designed to endure. Fortunately the aircraft was able to land despite substantial damage incurred by mid-flight decompression which resulted in the loss of one of the cabin crew.
Today, aircraft flight hours and stresses exerted on all components are rigorously monitored with ‘end-of-life’ status being assigned and checked continuously — especially in the world’s extensive trade of second hand aviation parts.
One of the biggest challenges for the many of the worlds military aircraft in relation to maintaining pressurisation, is found in the big cargo lifters like the Douglas C-33 Cargo Master and the later C-130 Hercules.
Both aircraft experience multiple pressurisation and depressurisations as their large rear doors are constantly being opened and closed mid-flight to facilitate cargo and parachutist drops.
A jet fighter has a relatively small cockpit and is easily pressurised and should accidental depressurisation occur, the impact on the aircraft and pilot is often recoverable. Not so for a fully-pressurised heavy cargo lifter wlike the C-130 Hercules. A rapid depressurisation at altitude for a C-130 can often be fatal.
For aircraft such as the Douglas C-130 Hercules, internal pressurisation is constantly being adjusted as the aircraft operates at different altitudes depending on its mission. Before the advent of today’s more advanced remote sensor controls, in earlier C-130s, cabin and fuselage pressure was adjusted manually by the flight engineer who sat just behind the overhead panel between the pilot and co-pilot.
This original AiResearch Cabin Pressure Controller enabled the engineer to adjust the aircrafts pressure to match its operating height and also the 'Rate of Pressurisation'. Both ‘Cabin Altitude’ and ‘Pressurisation Rate’ knobs are fully functional and combined with a highly detailed custom built model of the C-130 Hercules, Instrument Fact Sheet and Display Stand ,this Recovery Curios Aviation Collectable would make a fantastic gift for any aviation enthusiast.
PLEASE NOTE THAT THERE IS ONLY ONE OF THESE AVAILABLE
This C-130 Hercules Instrument comes complete with detailed Scale Model, Mango Wood Stand & Plaque plus Printed Fact Sheet featuring photo of instrument in aircraft cockpit.
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Your C-130 Hercules, Air Pressure Cabin Controller, Original Recovery Curios Warbird Collectable includes:
- Original Warbird instrument
- Highly detailed hand-built and airbrushed 1/72 plastic scale model of the aircraft,*
- Hand-crafted and beautifully finished 100yr, Far North Queensland Mango Wood display stand
- Detailed, 2-sided, printed and laminated Instrument Fact Sheet detailing aircraft and instrument
- Removable Magnetic Display Arm
The 1/72 scale hand-built and airbrushed plastic model is available with 'wheels & flaps up or down' and 'canopy and rear loading door open or closed' options with a choice of two Squadron markings and camouflage.
Upon order placement you will receive an email asking for your preferred configuration.
Your complete Recovery Curios Original Instrument Collectable is securely packed and delivery normally takes between 4 - 6 weeks approx.
Did you fly, crew or maintain a C-130 Hercules or have a friend, colleague or family member who did? Check out our PERSONALISED ORIGINAL INSTRUMENT COLLECTABLE OPTION here.