What would cause a Rapid D?
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What would cause a Rapid D?
Other than a structural event, what would cause a Rapid D? On a recent flight, the other pilot said he understands that a pack problem could be a source.
I wonder if that is a valid statement. Have any of you read anything on this?
If there is no structural problem, after the Rapid D procedures are complete and you are level at FL100, does the emergency still exist? Would you overfly the nearest/suitable to get to a place where maintenance is available?
Each situation will be different, however, it is a curiosity question.
I wonder if that is a valid statement. Have any of you read anything on this?
If there is no structural problem, after the Rapid D procedures are complete and you are level at FL100, does the emergency still exist? Would you overfly the nearest/suitable to get to a place where maintenance is available?
Each situation will be different, however, it is a curiosity question.
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We once had a rapid loss of pressuer (well, not explosive, but above 2000fpm in the cabin and not controllable) during cruise in a 737-3 without any apparent structural problem or pack problem. An emergency descent was done according to standard boeing non-normal procedures and the flight completed without further problems.
In the post event check two failed pressure seal clamps on the apu duct (one at the aft pressure bulkhead, the other in the wheel well) were found which were not covered by the boeing mainentenance planning manual. The one at the bulkhead was out of position and the one in the wheel well was broken. In a fleet inspection on those pressure seal clamps nearly all of them were found to be installed incorrectly right from the production (back then the fleet average age was around 2 years and no D checks done yet).
In the post event check two failed pressure seal clamps on the apu duct (one at the aft pressure bulkhead, the other in the wheel well) were found which were not covered by the boeing mainentenance planning manual. The one at the bulkhead was out of position and the one in the wheel well was broken. In a fleet inspection on those pressure seal clamps nearly all of them were found to be installed incorrectly right from the production (back then the fleet average age was around 2 years and no D checks done yet).
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None,
Three types of issues can arise with pressurization systems.
The first is a 'pressurization problem'. This can be as simple as a bleed air source becoming unavailable. The worst case of a 'problem' might be a dual bleed fault. The outflow valve(s) will close and the cabin will climb at about 700-800 feet per minute.
The second is a 'rapid depressurization'. This could be caused by a fault in the pressurization system that drives the outflow valve to the open position. The cabin will climb rapidly and may be controllable in alternate auto modes or in the manual mode.
The third is an 'explosive depressurization' and would be caused by structural failure. The cabin will climb almost immediately to the aircraft altitude, fog will be present in the cockpit, years of accumulated dust will be flying around and probably a very loud 'bang' will have occurred. Of course the cabin is uncontrollable.
Each situation is unique and has different indications but pilot reponse should be the same. Get your O2 mask on, evaluate and act. My opinion is that in all situations where the cabin altitude is climbing the proper response is to start descending while you work through the issue and take appropriate actions.
best regards,
Bruce Waddington
Three types of issues can arise with pressurization systems.
The first is a 'pressurization problem'. This can be as simple as a bleed air source becoming unavailable. The worst case of a 'problem' might be a dual bleed fault. The outflow valve(s) will close and the cabin will climb at about 700-800 feet per minute.
The second is a 'rapid depressurization'. This could be caused by a fault in the pressurization system that drives the outflow valve to the open position. The cabin will climb rapidly and may be controllable in alternate auto modes or in the manual mode.
The third is an 'explosive depressurization' and would be caused by structural failure. The cabin will climb almost immediately to the aircraft altitude, fog will be present in the cockpit, years of accumulated dust will be flying around and probably a very loud 'bang' will have occurred. Of course the cabin is uncontrollable.
Each situation is unique and has different indications but pilot reponse should be the same. Get your O2 mask on, evaluate and act. My opinion is that in all situations where the cabin altitude is climbing the proper response is to start descending while you work through the issue and take appropriate actions.
best regards,
Bruce Waddington
Last edited by Bruce Waddington; 18th May 2009 at 03:56.
At the first hint of cabin altitude problems, it is prudent to get 1 pilot on oxy at once.
A quick check of supply duct pressure, outflow valve position and cabin RoC should then clarify the options.
A quick check of supply duct pressure, outflow valve position and cabin RoC should then clarify the options.
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I have had two rapid (as opposed to explosive) decompressions on two unrelated aircraft types. In both cases, surprisingly, the root cause was essentially the same - the aircraft decided (through squat switch logic and related fault conditions) that it was on the ground, and therefore dumped the cabin.
The good news is that I can tell you that decompression doesn't hurt - usual drills calmly executed, etc. Unfortunately, on the first aircraft mentioned, the "I'm on the ground" fault was intermittent. The bad news is that when we were a few seconds into the drills, the aircraft changed its' mind again and decided that it was airborne after all, at which point it re-pressurised with a "whump" - and that hurts like hell!
The good news is that I can tell you that decompression doesn't hurt - usual drills calmly executed, etc. Unfortunately, on the first aircraft mentioned, the "I'm on the ground" fault was intermittent. The bad news is that when we were a few seconds into the drills, the aircraft changed its' mind again and decided that it was airborne after all, at which point it re-pressurised with a "whump" - and that hurts like hell!
Being a technical forum, you may want to keep you terminology technical! 
By the (I'm sure very "hip and trendy") term "Rapid D" - do you mean "Rapid depressurization" or "Rapid Descent" ?
By the (I'm sure very "hip and trendy") term "Rapid D" - do you mean "Rapid depressurization" or "Rapid Descent" ?
