Looking for A-14 (or similar) pressure breathing diluter demand regulator

On Sunday, December 23, 2018 at 9:59:15 PM UTC-8, wrote:
I would like to correct a couple of statements made here with respect Bob Harris’s altitude record flight. My apologies for being slow to respond.
1) Bob Harris did not limit his climb “because he couldn't keep his mask on�. He terminated the climb because he believed one of his two oxygen systems had malfunctioned.
2) However, the statement that he was “forced down when his oxygen system started to fail� is also incorrect. His subsequent investigation showed that both oxygen systems were operating within specification. The problem was they were not operating identically. As Bob pointed out in his presentation to the World Gliding Championship at Benalla, Australia the following year, differences in the regulators’ pressure settings, stiction between the components, the lack of vibration in the sailplane to address that stiction and the fact that the regulators were at or near their operating limit, resulted in a substantial difference in the pressure he felt in his mask when he switched between the two systems. He interpreted this difference as an indication that one of the two had failed, but later determined it had not.
3) He did not suffer from any medical condition as a result of his record flight.
Mike Koerner

Thanks Mike. After reviewing Bob Harris's article I have a few observations:
1) the regulators he used we MD-2s not A-14s. These were manufactured by Cobham Life Support.
MD-2 regulators are obsolete; they were the 2894 series and they got replaced by 29255 series regulators. Very similar units. No idea how these compare to A-14s except they were both rated to ~50k'.

2) the account I heard, but did not verify, was that Bob terminated his flight because he couldn't keep his mask on (due to high pressure on the mask).. You note, and the article confirms, that he reported what he thought was a failed regulator (delivering higher pressure than expected). Is it possible that these reports are related i.e. the regulator he thought had failed was delivering higher pressure than the other one - and so it as forcing his mask off? Maybe a minor point but maybe not. At some point, if the mask is not tight enough it may be forced off and this is something to be prepared for. I added an extra strap on my mask as a backup to the 8 snap connections on my A-11 helmet for this reason.

3) I had heard, but did not confirm, that he vented his mask to the outside but in his article he clearly states he frosted up above 32,000' and was flying on instruments by 39,000' has he had zero visibility! I also experienced significant canopy icing on both my flights to 25k' and 28k'. I was able to "scrape and wipe" to maintain visibility but I expect this could be an overwhelming task at 30k' and above. I am looking at ways to apply film "windows" on both sides of my canopy and also vent my exhaled air to the outside. This is another significant issue to address.

Appreciate your feedback. It's obvious that lot's can go wrong attempting these high flights and the more accurate info we can learn from the better prepared we can be.

I also fly with an oximeter and have found the readings to be very informative for evaluating cannula versus mask performance. However, it would appear that even these can be misleading, if I recall the recent SSA article correctly, so again, good to know and more work to be done.

Jim
VVII

Growing up in Winnipeg, it was normal each fall to fit 'frost shields' to the car. "Frost shields' were a sheet of stiff plastic with a perimeter band of rubber, with an adhesive to stick to the car's glass windows, and sufficient additional rubber buttons to maintain an air gap everywhere. Canadian Tire stocked them in a variety of shapes and sizes. When visiting friends down south, we told them it was bullet proof glass.

It was standard practice to fit frost shields to gliders used to fly high in the southern Alberta wave at Cowley at least up to my first experiences there, and my diamond climbs, in the early 1980s. Then, Canadian Tire stopped stocking them. But, they did work.

Growing up in Winnipeg, it was normal each fall to fit 'frost shields' to
the car. "Frost shields' were a sheet of stiff plastic with a perimeter
band of rubber, with an adhesive to stick to the car's glass windows, and
sufficient additional rubber buttons to maintain an air gap everywhere.
Canadian Tire stocked them in a variety of shapes and sizes. When visiting
friends down south, we told them it was bullet proof glass.

It was standard practice to fit frost shields to gliders used to fly high
in the southern Alberta wave at Cowley at least up to my first experiences
there, and my diamond climbs, in the early 1980s. Then, Canadian Tire
stopped stocking them. But, they did work.

Indeed. There might BE a reason the frosty bits of North America have mostly
moved on from single-pane house windows.

In the soaring world, the participants with whom I spoke from the Sierra Wave
Projects could no longer (if ever) identify a
single-source/individual/"inventor" of "double-paned" canopies...but all
agreed they worked superbly for them. Triple panes were experimented with, but
their conclusion(s) were the additional benefit wasn't worth the
effort/nuisance, and, double-paning was good enough. They spent a LOT of time
above (say) 30k', often hours per flight...

The 'art' of double-paning glider canopies seems to be sufficiently arcane
that each (prolly statistically tiny) group of 'wave junkies' every generation
has to re-learn both: a) of the theoretical benefits, and b) how to
double-pane. Current SSA members can find several "How To" articles in back
issues of soaring post-1972 (and earlier?).

Somewhat-bendy plastic (e.g. lexan, these days), suitable cutting technology
(eg. box cutter, diamond scribe) and viscous/lowish-sticky goop are your
friends...

Bob W.

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Do you have any resources for the CRU-79 where I can buy them, I have problems to install the A 14 or CRU-72/ MD-2 regulator in my cockpit due to limited space

On Thursday, December 27, 2018 at 11:28:43 AM UTC-8, wrote:
Do you have any resources for the CRU-79 where I can buy them, I have problems to install the A 14 or CRU-72/ MD-2 regulator in my cockpit due to limited space

Try:
Cobham Life Support
2734 Hickory Grove Road Davenport, IA 52804 USA
Tel: Fax:
+1 (563) 383 6000 +1 (563) 383 6323

https://www.cobham.com/mission-syste...lator/docview/

Jim
VVII

On Wednesday, December 26, 2018 at 5:47:38 PM UTC-7, wrote:
On Sunday, December 23, 2018 at 9:59:15 PM UTC-8, wrote:
I would like to correct a couple of statements made here with respect Bob Harris’s altitude record flight. My apologies for being slow to respond.
1) Bob Harris did not limit his climb “because he couldn't keep his mask on�. He terminated the climb because he believed one of his two oxygen systems had malfunctioned.
2) However, the statement that he was “forced down when his oxygen system started to fail� is also incorrect. His subsequent investigation showed that both oxygen systems were operating within specification. The problem was they were not operating identically. As Bob pointed out in his presentation to the World Gliding Championship at Benalla, Australia the following year, differences in the regulators’ pressure settings, stiction between the components, the lack of vibration in the sailplane to address that stiction and the fact that the regulators were at or near their operating limit, resulted in a substantial difference in the pressure he felt in his mask when he switched between the two systems. He interpreted this difference as an indication that one of the two had failed, but later determined it had not.
3) He did not suffer from any medical condition as a result of his record flight.
Mike Koerner

Thanks Mike. After reviewing Bob Harris's article I have a few observations:
1) the regulators he used we MD-2s not A-14s. These were manufactured by Cobham Life Support.
MD-2 regulators are obsolete; they were the 2894 series and they got replaced by 29255 series regulators. Very similar units. No idea how these compare to A-14s except they were both rated to ~50k'.

2) the account I heard, but did not verify, was that Bob terminated his flight because he couldn't keep his mask on (due to high pressure on the mask). You note, and the article confirms, that he reported what he thought was a failed regulator (delivering higher pressure than expected). Is it possible that these reports are related i.e. the regulator he thought had failed was delivering higher pressure than the other one - and so it as forcing his mask off? Maybe a minor point but maybe not. At some point, if the mask is not tight enough it may be forced off and this is something to be prepared for. I added an extra strap on my mask as a backup to the 8 snap connections on my A-11 helmet for this reason.

3) I had heard, but did not confirm, that he vented his mask to the outside but in his article he clearly states he frosted up above 32,000' and was flying on instruments by 39,000' has he had zero visibility! I also experienced significant canopy icing on both my flights to 25k' and 28k'. I was able to "scrape and wipe" to maintain visibility but I expect this could be an overwhelming task at 30k' and above. I am looking at ways to apply film "windows" on both sides of my canopy and also vent my exhaled air to the outside. This is another significant issue to address.

Appreciate your feedback. It's obvious that lot's can go wrong attempting these high flights and the more accurate info we can learn from the better prepared we can be.

I also fly with an oximeter and have found the readings to be very informative for evaluating cannula versus mask performance. However, it would appear that even these can be misleading, if I recall the recent SSA article correctly, so again, good to know and more work to be done.

Jim
VVII

I've used clear acetate (sorry can't recall the thickness, but thick enough to hold shape without wrinkling). I've used both sheets and pieces cut from rolls. I tape them to the interior of the canopy using Scotch Magic Tape (easier to remove or re-position though not clear). The slight air gap seems to be enough to keep frost from forming.

Frank Whiteley

On Wednesday, December 26, 2018 at 12:38:21 AM UTC-8, wrote:
Bob Harris’s altitude record flight is described in an article by Pat Valdata in the October '88 issue of Soaring Magazine. The article is available to SSA members in the on-line magazine archive. However, that article does not go into detail about the oxygen system issue.
I don’t know what else is available on-line, but I have a pdf of his Benalla presentation which includes both a discussion of the flight and his oxygen regulators’ performance. I would be happy to forward it to anyone who wants it. Email me (first initial last name at cox.net).
Mike Koerner

The article referenced is not in the October 88 issue, rather the February 88 issue.

Yeah, You're right. Thanks Jonathan.
Sorry folks.
Mike Koerner

At 21:32 30 October 2018, Keith Schwab wrote:
Hi Everyone!
I'm looking for an A-14 regulator, or something similar, to prepare for
higher altitude wave flights in the Sierra. Curious if anyone has an
one
laying around they might be willing to part with or lend for a season.
Thanks!
Keith




Check out the German want ads. This showed up today:

https://www.segelflug.de/osclass/ind...=item&id=31669

RO