Originally Posted by
EyeWideShut
BOAC, Late Developer,
Points on physiology of the ear well taken. However, I hope neither of you is implying that a difference of 2,000ft/min over the JAA maximum of 500ft/min during ascent is hardly noticeable
EWS - I have an open mind about it. If by 'hardly noticeable' you mean no excrutiating pain on the way up experienced by anyone at +2500 feet per min then I can easily accept Sea Level to 2500 as a no real fuss situation. You might just have to gulp frequently to overcome it. Going higher at the same rate I have no idea. If you have a cold then I am sure you would have big problems but otherwise I am not sure you would. Like BOAC I am more sensitive than most I think. Personally I know the pain on the way down, but have never experienced anything worse than the dull pop-puffing feeling on the way up. As an A to B touring PPL, I have experienced 1000 feet per minute ascents straight off the runway to about 2400 feet in my favourite light aircraft and they are nothing to write home about either.
Perhaps aerobatic pilots and divers can offer more observations and any PP who has deliberately gone up at that rate unpressurised.
I don't know why JAA limit going up is set at +500ft/min cabin altitude. It could be for reasons other than discomfort.
I also know from more than one experience that cabin crews do not immediately alert the flight deck if only a few children are experiencing problems. They are more likely to put some hot water on a tissue in the bottom of a plastic cup and suggest the injured child then cups it over their ear! (Truly!)
Even if there was fuss in the cabin it might soon calm down as the effects of hypoxia took hold.
Before we leave this, some readers might be interested in a 2004 UK Department of Transport study of various types of cabin observation in two types, one of which was 733.
http://www.dft.gov.uk/stellent/group...ion_027562.pdf. Forgive me if this report has been highlighted before. It shows that +500/-300 limits are routinely broken albeit max breaches were measured at +554/-449 in the 6x733 study flights (greater routine breaches were measured on a sample of 7xBAe146 flights in the same study). Interestingly, they also measured max 733 cabin altitude at about 6800 with average 6500 in their sample which tallies better with what I was taught was the general case ('usually between 6000 and 8000, and certainly not above 8000'). We were also taught that the worst affected regular smokers experienced effects 5000 feet worse than healthy passengers and crew. 8000+5000=13000 hence the 8000 absolute maximum cabin altitude so that smokers (pilots or pax) do not get rendered unconscious on any regular basis.
By all means let's now get back to the other question you raised I will bump back down here for you:
Now, can we get back to the dispute over the single Switch Assumption scenario... please?
Let's start with the obvious question: Could the Ground Engineers Numbers One and Two of the Tsolakis Report open the door to exit the plane after their pressurisation test, if they had left the OFV almost closed at a 14.6-degree angle (which means the plane had barely 'depressurised' from its maximum 8psi differential reached during the test)?