Simple design for pressurized Sailplane

[Aesquire]

I took the U.S. Air Force class on high altitude survival because I had an opportunity to do a high jump from a balloon. Class work before & after the pressure tank. Plenty of videos out there on the course, which I highly recommend if going over 18'000 is something you want to do. The SOP is to have each student remove their mask and do simple math & write on a notepad as they got dumb. You start off laughing at the others, do your turn, usually feeling pretty good about yourself, then after going back on Oxygen, the scribbles and 3 times 6 equals 16 sobers you up, hard.

Like alcohol, one of the first higher brain function that shuts off is the self critical part. I really understand how you get into spins, death spirals, and thunderheads...seems like you're doing fine....

 

[BoKu]

This is basically a question for Bob (BoKu) is this ship maybe what inspired your thinking or similar to what you were thinking with Indigo Sky?

Oh, good lord, someone remembers that project!

I believe that the aircraft in the picture is indeed MOBA, but I can't remember if it was the inspiration for the idea of the removable forward fuselage envelope.

I think that mostly came from reading Tony Burton's book Stalking the Mountain Wave and finding out that the Alcor pressurization system was essentially useless. The canopy and other seals leaked so badly that they couldn't maintain more than a couple PSI of pressure.

Thinking on some way of reducing the seal perimeter to its bare minimum while simplifying its geometry led naturally to the idea of an inflatable seal based on a high-pressure bicycle inner tube. The idea is that the non-structural fuselage shell would slide back over the crew, and then rotate around its longitudinal axis through an angle of about 10 degrees to engage about a dozen locking lugs on the fuselage. Then you'd pressure up the inflatable seal with nitrogen to about 100psi and have essentially a leak-free interface.

 

[TFF]

I have a buddy who knew your buddy taking the A4. My friend ended up as the only enlisted man in the corp to be allowed to taxi and run engines for A4s. He has over 1000 hours in the rear of a TA4. He was told if the nose wheel leaves the ground constitutes theft. Ended up as the last Douglas A4 rep.

 

[proppastie]

My IA took a T33 around the pattern....claimed it took off on a fast taxi. Difference between AF and Marines. ...I think they gave him a plack.

 

[Riggerrob]

Dear Aesquith,
Skydivers are always pushing the limits of sanity and hypoxia.

Back when piston engines were the norm (1970s and 1980s) we only went to 12,500' because DC-3s and Beech 18s climbed so slowly.

During the late 1980s, I did a handful of tandem jumps from 19,000 feet. Boy was that dumb! ... as in stupid!
I had recently completed the RCAF's high altitude indoctrination course and regularly cleared hang-overs with 20 kilometre runs on Sunday mornings. Even so, by the time I carried a "254 pound" tandem student the length of a Dornier 228 cabin, I was puffing like a locomotive and seeing stars!
Nowadays, turboprop jump planes routinely take skydivers up to 14,000 or 15,000 feet MSL, but climb so fast that they spend less than 5 minutes above 10,000 feet. These planes often fly 4 or 5 loads per hour ... you do the math.
Young skydivers cannot recognize the difference between hypoxia and hang-overs.

 

[BoKu]

BTW, I'm pretty sure that this is the post and thread that sparked the initial query:

Pressurization=> structural big window?

 

[wsimpso1]

Also 25000 ft is the limit were one would survive (not function) without o2

You might want to revisit your source on this and edit the post - as written it can not be true. First, folks have flown much higher without bottled O2 and lived to talk about it. Second, Everest is 29029' and over 200 people have ascended it without supplemental oxygen - they spent days above 25,000' without bottled O2 to do that.

Billski

 

[Aerowerx]

I remember in high school English class, we read a short story about an RAF pilot that bailed out at 40,000 (or something like that). He did free-fall for 30,000 feet before pulling his chute. The entire story was his thoughts as he fell that far.

(My numbers may not be accurate, but he was smart enough to know that if he pulled the chord right away he would not survive.)

 

[Mad MAC]

You might want to revisit your source on this and edit the post - as written it can not be true. First, folks have flown much higher without bottled O2 and lived to talk about it. Second, Everest is 29029' and over 200 people have ascended it without supplemental oxygen - they spent days above 25,000' without bottled O2 to do that.
Billski

It was a not very clear reference to the driving rational to the requirement of FAR23. With regard to Everest one should note the level of altitude acclimation (they didn't have breakfast at sea level, typically spending weeks at base camp), nor that most make multiply attempts before succeeding, nor that many Everest deaths are O2 related, even in those using O2. The FAA would not be impressed with a fatality rate of 1 in a 1000 for depressurization events (Everest runs about 7 in 1000 per year, all causes).

 

[lr27]

According to the 1991 Naval Flight Surgeon's Manual, page 1-30, pure oxygen at 33,700 feet provides the same alveolar (sp?) partial pressure,of oxygen as air at sea level does.

 

[BoKu]

According to the 1991 Naval Flight Surgeon's Manual, page 1-30, pure oxygen at 33,700 feet provides the same alveolar (sp?) partial pressure,of oxygen as air at sea level does.

Just so, it's the partial pressure that does it. Air being 80% nitrogen, a healthy person generally has enough saturation margin that they can safely use 100% oxygen up to 35,000 and maintain effective consciousness. From there on up to about 45000 feet you'll want pressure breathing equipment to press the oxygen across the membranes of the alveoli. From 45k on up you should really have a pressure suit or a pressurized cabin. Bob Harris went to about 49k with military surplus pressure breathing regulators, but he probably left no few brain cells there.

 

[Aerowerx]

Just so, it's the partial pressure that does it. Air being 80% nitrogen, a healthy person generally has enough saturation margin that they can safely use 100% oxygen up to 35,000 and maintain effective consciousness. From there on up to about 45000 feet you'll want pressure breathing equipment to press the oxygen across the membranes of the alveoli. From 45k on up you should really have a pressure suit or a pressurized cabin. Bob Harris went to about 49k with military surplus pressure breathing regulators, but he probably left no few brain cells there.

Thank you BoKu!

That's the type of answer I wanted to my question.

 

[Riggerrob]

Also remember that most military oxygen standards are written for young men in peak physical condition.
OTOH most HBA pilots are older, stouter and quit running marathons many years ago. Ergo, few private pilots will be healthy or sane after a 30 minutes much above 10,000 feet.
I remember crossing the Rockies (cruising about 15,000') after a hard-week's work. Most of the other skydivers fell asleep. I stayed awake, reading the map, bit noticed that even twisting my shoulders (to look out the other window) put me in oxygen debt.

 

[cluttonfred]

As an aside, I'll just say that "simple" and "pressurized" should never be used in the same sentence when talking about airplanes. ;-)

 

[harrisonaero]

I took the U.S. Air Force class on high altitude survival because I had an opportunity to do a high jump from a balloon. Class work before & after the pressure tank. Plenty of videos out there on the course, which I highly recommend if going over 18'000 is something you want to do. The SOP is to have each student remove their mask and do simple math & write on a notepad as they got dumb. You start off laughing at the others, do your turn, usually feeling pretty good about yourself, then after going back on Oxygen, the scribbles and 3 times 6 equals 16 sobers you up, hard.

Like alcohol, one of the first higher brain function that shuts off is the self critical part. I really understand how you get into spins, death spirals, and thunderheads...seems like you're doing fine....

When I was doing certified seat crash testing at CAMI in OK City they told a story of testing a gal who was a drop dead gorgeous blonde Air Force pilot and literally never was affected by altitude tests in their chamber during the entire test. Of course airhead jokes were plentiful.

 

[paraplane]

Glad I started this discussion. From joyriding military jets to high altitude skydiving and mountain climbing! Pretty good I liked the post on the short story of the RAF pilot. Crazy. Bob thanks for reading this and for the comments. I actually was inspired to ask I think from another conversation where you had described the thought of using a bicycle inner tube and remembering that when I saw a photo online of the Yellow Sailplane in the photo I posted. I had run into that photo but couldn't find specifics on the ship and thought I'd ask. I thought it very resourceful thinking using a bike innertube. I'd started thinking of pressurization after my first sailplane flight with Nieman Walker of the Cal Poly Akaflieg in the Soar Avenals 2-33 It was quite an experience and one that I had been looking forward to for many years. The flight and surrounding experience was pretty great I could explain so much about that day one thing however was discouraging and that was a sinus pressure that developed after the flight. It may have been related to not having equalized my inner ear on descent. I had cleared my ears on the ascent but with the euphoria and exhilaration of the flight forgot to clear my ears on descent. I had a pretty bad sinus pressure and headache and then had to go to work that night. I have been a little upset thinking that this could be a physiological problem that could inhibit my ability to fly Sailplanes and other aircraft in the future. A desire I've had since childhood.

 

[lr27]

I used to have trouble clearing my ears when scuba diving. Then I started swimming to the bottom of a pool a few times a week. That seemed to help some.
When I have congestion, my ears don't clear well. Maybe you had a little? I wonder if there are decongestants that the FAA allows?

 

[paraplane]

Yeah I used to Freedive spearfish.
In cold water I was unable to equalize unless I used a special type of earplugs made for diving. I seem to have a slight inner ear problem in one of my ears that seems to be permanent though it could have to do with a long time sinusitis. I was afraid if I had a permanent inner ear problem I would possibly only be able to fly pressurized aircraft. I think the matter could have easily been that I was distracted, essentially task saturated and missed equalizing on descent. I may not have an inner ear problem at all. It just wasn't a good thought that I wouldn't be able to pursue a sailplane solo or other pilots license and I nearly immediately started looking into ways to continue and be able to fly if I do have a physiological condition.

 

[blane.c]

You might want to revisit your source on this and edit the post - as written it can not be true. First, folks have flown much higher without bottled O2 and lived to talk about it. Second, Everest is 29029' and over 200 people have ascended it without supplemental oxygen - they spent days above 25,000' without bottled O2 to do that.

Billski

As I understand it you cannot survive indefinitely above 18,000ft your body starts breaking down … or is it that it won't repair itself? Either way you get worse off physically the longer you stay. Short foray's can be tolerated but you will gradually weaken the entire time. I would think the temperature would be as much a problem as oxygen the extreme cold will wear on you mentally as well. Keep the plan simple get up get down.

 

[lr27]

Depending on one's definition of indefinitely, this could be true at any altitude.