The use of oxygen in helicopters

sph-4_noreg_ms22001_01_tn.jpg (20959 bytes)
SPH-4 helmet with MS22001 oxygen mask with is attached with an Hardman shell and snaps
to the posts on the helmet retention assembly. This mask configuration with its corrugated
oxygen hose was most likely used when spraying with defoliants in VietNam similar to the
fixed-wing Ranch Hand operations. Unknown

Message 1814, 14 Apr 2001:
When we discuss helicopter use in the U.S. military, we must remember that three different branches (if you include the Marine Corp as part of the Navy) use helicopters. So it isn't always possible to cover everything for everyone and I don't have all the details.
For starters, and I think this is important to note: Scott-Sierra's 1989 catalog carries both the A-14B (part # 28400) and A-8B oxygen masks. As I understand it, both of these masks can still be purchased brand new, as can parts for both masks. The US Navy did use the A-8B as an emergency mask in some of their non-tactical aircraft and batches of these masks surface periodically.
From the USAF side of the house, the HGU-39/P is not a helicopter helmet but designed for use by aircrew in tandem with the MBU-13/P bio-chemical mask. Hence the oxygen mask receivers. The reason most of these helmets do not have visors is that the MBU-13/P mask has a clear visor and there is a small sun visor that attaches directly to the mask. Any helmet mounted visor would scratch the mask's visor(s). I do think the HGU-39/P could be modified with a visor (probably dual visor) and used in USAF helicopters. (US Army) FM1-301, "Aeromedical Training for Flight Personnel" is very clear on the use of oxygen on Army Aircraft: The A-13A was the standard mask to be replaced (attrition) by the MBU-12/P. The MBU-5/P could also be used. These masks were affixed to the helmet via standard oxygen mask receivers (subdued color). There is a special diluter demand mask used in theC-12 (one was recently sold on E-Bay, it is a commercial mask). The OV-1 and U-21 Aircraft are equipped with pressure demand regulators.
The A-14 and A-8B masks were probably used for emergency use in Cargo and non-tactical aircraft. These masks are available from various sources and most do not have a microphone. The US Army masks pictured in FM1-301 appear (really bad quality photo in the manual) to have both a boom microphone, and mask mounted microphone. I think any tactical use of the A-14B or A-8B after about 1960 is unlikely (remember the USAF standardized the A-14B as the MBU-4/P and used it through the 1960s, but probably in older, low altitude aircraft).
The Navy has been experimenting with various HEED (Helicopter Emergency Egress Device). I do not have any operational details at this time. In the current iteration, the HGU-84/P (updated version of the HGU-67) US Navy helicopter configuration would be modified with o-mask receivers and the MBU-17(V1)/P is used if an oxygen mask is required. My guess is they did the same think a few years ago with the A-13A. But you don't find many Navy SPH-3s with oxygen mask bayonets.
More fuel for the fire, FIGMO

Message 1813, 14 Apr 2001:
Hi Pilot, Thanks for settling that even firmer. I learn a lot from these exchanges of information on flightgear. But what about this one (eBay auction 1134262915) An SPH-3B with an A-14 oxygen mask? Is that equally authoritative? I thought that the SPH-3B was introduced around 1970?
Cheers, Bluelight

Message 1809, 13 Apr 2001:
Hello again... I respond to a previous discussion in regards to a unusually configured APH w/02 mask offered on Ebay recently...this wasn't a home brewed bastardized abortion...this was the real deal friends. It just is very rarely seen in that configuration. While it isn't usually needed by the low and slow movers, it is true that often rotary winged aviators will fly with the 02 setup, it is not all that uncommon for such operations to require such a setup...high altitude mountain operations are such a situation. And on more than one night as I have prepared for a night op, I myself have been known to dip into 02 to increase my night vision prior to departure. Along with cross-country trips at or near the altitude limits of rotary craft occuring and with such sustained ops 02 would often be required, dependent upon aircraft and location. If you look back to the SPH-1 & 2 you will note additional snap points fitted to the helmet and later on in the series,(3 & 4 models) on the retention harness...these attachment points are for 02 equipment. After the 4 model most retention systems omited the snap points in leiu of bayonet recievers that have most likely been seen afixed to several helmets, this configuration is usually seen on the HGU-39 and I have seen them on several SPH-4's So there is my 2 cents worth on a by gone subject...better later than never at all!
Best Regards, Kirk Sunley.

Message 1759, 9 Apr 2001:
Looks like a really early APH-5 and a nice one to boot. Check out the old style lock knob, visor, visor housing and the M-33 microphone, not to mention the leather tabs. It appears to be in really nice condition. As configured, I'd say the helmet was used for helicopters or close air-ground operations. The mask looks like vintage WWII A-14 (B?). I would expect that a late 1950s, early 1960s APH-5 would have an MBU-4/P oxygen mask. My guess: really nice helmet, probably not a bad mask but the owner (surplus store???) put the two things together. In any case, it looks like a really nice, early example of the APH-5. Ask the seller what type of mask and if it is dated? For Chris Carey: Ever seen the MC-3A connector on the A-14 or MBU-4/P masks?
Cheers, FIGMO

Message 1696, 7 Apr 2001:
Rich and DocBoink, Thanks for broadening my knowledge on O2 in helo ops. Maybe I should  talk to our flying safety guys about night operations. Our Search and   Rescue helicopters frequently fly at night under taxing conditions, not to mention our Navy heloes operating in the North Atlantic from  what must be the smallest helo decks anywhere. A little O2 during a  night landing might be a good idea.
Cheers, Bluelight

Message 1693, 7 Apr 2001:
Bluelight, This is an interesting query, as at first glance 02 by mask might seem superfluous to rotary wing flight op requirements. Suffice it to say that there are several reasons why 02 by mask might be beneficial to rotary wing crewmen. First among them is a reiteration of Rich's comment that 02 is desirable for any flight ops undertaken above FL10--this, of course, includes high altitude rotary wing flight ops. In Europe, specialised high altitude helicopters such as the Aerospatialle Gazelle and Llama are routinely used at or above FL14 in the Alps. In the Himalayas helicopter flights to even high altitudes are possible, again due to the special high-altitude turbine powerplants and blades used that allow such high flights by rotary wing craft.
Second, supplemental 02 is critically important for sustaining peak visual efficiency at altitude; this is most particularly true in night flying, due to the 02 needs of the highly vascularised retinal tissue of the eye and maintenance of proper rod & cone functions of that structure. As you know, night flight ops in the US Navy (and probably in the USAF and other air forces, as well) require mandatory 100% 02 for this reason. Extreme cold conditions also substantially increase the need for supplemental 02 to maintain normal parameters of human physiological function (examples would include high altitude mountaineering, as well as high altitude flight). In the infancy of helicopter operations, high altitude helicopter flight was not undertaken due to limitations in the rotary wing aircraft technology extant. Now that a variety of high efficiency turbine powerplants and specialised, high lift blade designs allow normal operations at substantially greater altitudes, availability of 02 by mask is a much more important safety factor for chopper crews than it originally was.
Occasionally, one will run across rotary wing flight helmets on eBay (usually SPH-4 types), clearly of US Army issue, that are mated with 02 masks issued to the helicopter crewman. All of these masks are of the demand type, but not infrequently one will see a pressure-demand type, since the latter type mask can perform equally well throughout the low and higher altitude envelope. As you may know, the original A-13 and A-13A masks came with a standard non pressure- compensated exhalation valve fitted (same as that found on the A-14 series). Conversion to pressure demand mode involved simple fitment of the standard pressure-compensated exhalation valve and one-way inlet check valves. Only in the early 50s was the MS22001 type mask routinely fitted at the factory with the pressure-compensated valve and inlet check valves, as they have been from then onwards. The MBU-4/P and A-14A/B masks were formerly used in chopper ops, but so were MS22001 types. The original WWII type A-14 demand mask, amazingly, was still used with early hardshell helmets such as the original "Type-1" (or P-1, as it is commonly called) as commonly as it was with the A-13A type pressure demand mask (in the late 40s). The original WWII type A-14 mask was not manufactured (to the best of my knowledge) after 1945, but the very similar A-14A mask was manufactured as late as 10-66 and probably used until the very early 70s for various situations. The A-14B mask and MBU-4/P masks commonly were used in 'low & slow' operations (including helicopters) until about the mid-60s. Thereafter, various MBU-3/P, MS22001, and MBU-5/P types were used exclusively in flight operations, while the later members of the A-14 family of masks continued to be used occasionally in such applications as ground-based physiological training (altitude chambers).
An original WWII A-14 mask manufactured in 1945 may reasonably have been used with an early hardshell helmet (such as the Type 1), but never with an APH-5A of early Vietnam vintage. It is of course possible that the A-14A, A-14B, or MBU-4/P masks were used with an APH-5A in US Army flight operations, but with regard to Don Pino's APH-5A helmet and A-14 mask combination on eBay, one would have to first identify the specific A-14 model in reference to determine whether or not the mask was 'correctly' paired with the APH-5A in question. When I looked at that helmet in Don Pino's shop, some months ago, I did take a closer look at the unit (since it was a matter of curiosity to me to see this mask paired up with that helmet), but I do not recall the specific identification of that mask at this time.
Perhaps Pilot has some additional information on use of 02 by rotary wing flyers that he might wish to make available to the forum?
Cheers, DocBoink

Message 1688, 6 Apr 2001:
Hi Rich, Makes sense. Serves me right for being born in a country where the field elevation never exceeds 600 ft.
Cheers, Bluelight

Message 1686, 6 Apr 2001:
According to my friends who flew choppers in VN, it was not uncommon in certain parts of the country to have to fly above 10,000 to clear mountains.

Message 1685, 6 Apr 2001:
What kind of operational conditions would dictate the use of oxygen in helicopters? If my memory serves me right (DocBoink, correct me if I am wrong) oxygen would usually not be needed below 10,000 ft.  Could this helmet/mask combination have been used for pilots and/or loadmasters in US Army CV-2 (later C-7A) Caribou fixed-wing aircraft during paradrop missions from higher altitudes? According to my information they were used by the US Army from 1959 until they were transferred to USAF in 1967. How does that tie in with the A-14 mask? When was it taken out of service?
Cheers, Bluelight

--- In flightgear@y..., Rich Mays <richmays@h...> wrote:
> This is an APH-5, NOT an AFH-1 ballistic helmet.
> The mask (I think) is proper- It's an A-14, which
> would be fine for helicopters at lower altitudes
> where pressure demand is not necessary. Looks good
> to my eyes.
> Rich