DC6B Depressurisation

[WRosato]

Dear All,

I am researching an accident involving SE-BDY at NDOLA in the then Northern Rhodesia in 1961.

SE-BDY was a DC6B and I read an interesting analysis in a book called "Disasters in the Air" by Jan Bartelski. The technical aspects are a bit beyond me but I think the hypothesis is that: 1) DC6B's had a quirk that meant that "residual cabin pressure had to be dumped before landing". 2) The "static system" had a detached connection. Together the depressurisation and the compromise of the static system combined to make the pilots believe they were higher than they actually were. The author seems to know what he is talking about and mentions the positions of a manual release valve etc as supporting his theory.

I would be interested to speak to anyone who has knowledge/experience of DC6B's and could explain this to a layman.

Best

Bill

[punkalouver]

Dear All,

I am researching an accident involving SE-BDY at NDOLA in the then Northern Rhodesia in 1961.

SE-BDY was a DC6B and I read an interesting analysis in a book called "Disasters in the Air" by Jan Bartelski. The technical aspects are a bit beyond me but I think the hypothesis is that: 1) DC6B's had a quirk that meant that "residual cabin pressure had to be dumped before landing". 2) The "static system" had a detached connection. Together the depressurisation and the compromise of the static system combined to make the pilots believe they were higher than they actually were. The author seems to know what he is talking about and mentions the positions of a manual release valve etc as supporting his theory.

I would be interested to speak to anyone who has knowledge/experience of DC6B's and could explain this to a layman.

Best

Bill
I read the book many years ago. It has several accident theories which to me seemed like conspiracy theories. The DC-6 report seems to focus on a CFIT while the book is asking if a single bullet might have brought the craft down.

Only guesses, but my interpretation of point #1 is that the DC-6B is fully depressurized in flight so that it will be fully depressurized once it touches down which prevents a situation of residual pressure preventing the doors from opening quickly in an emergency.

My interpretation of point #2 is that there was a fault in the static system due to a line becoming disconnected which caused erroneous altimeter readings that led to the crew thinking they were higher than they actually were while on a night approach over poorly lit terrain.

[WRosato]

Thank you. That makes sense. The book discusses whether the altimeter connections had been replaced correctly and I think suggests that depressurising the plane too quickly before landing could have the effect of causing one of the connections to come loose.

Do you have any idea what the manual release valve that he mentions is, where it is located and what it looks like?

The book itself can be read at Internet Archive.

[megan]

Presuming the aircraft is the same as the military version, the C-118, there are three static sources, two on the nose just forward of the Captains position, one providing information to the captain and the other to the co-pilot, and one in the tail cone providing information to both pilots. Each pilot has a selector switch on the outboard side of his instrument panel where he is able to select "NORMAL" or "ALTERNATE". The only time pilots would both be using the same static source is if they both selected ALTERNATE.