Nomex -- Myths and Realities of Flightsuits

[riffraff]

I've read through some of the older uniform threads as well as the current discussions on uniforms, etc. Some great ideas, some not-so-great (IMO).

I was somewhat intrigued by the (presumed) belief that the green nomex flight suit is somehow a safety item in the CAP setting. It's been known for decades that nomex is/was designed for use in short-duration, high-temperature, flash fires. The design scenario was based upon a the premise that a few seconds of protection was needed to allow the wearer to escape (eject) from a burning aircraft. These suits do not protect from heat and will not prevent heat transfer (to your skin). It was intended that a wool or cotton undergarment would be the first-line defense from the heat -- again it was assumed that the duration of protection was to be a few seconds (3 seconds, IIRC).

Current USAF flight suits are 4.5 ounce nomex fabric -- about the same as a middle-of-the-road t-shirt. In a general aviation setting (i.e. avgas fire), nomex provides provides no more protection than street clothes of similar fabric weight.

If you want to wear something to protect against a G-A fire scenario, you'll need to head down to your local fire department and look at their turnout gear. Yes, you'll see Nomex or Proban but it will have at least an inch of padding beneath it to delay heat penetration.

The reason I bring this up? First to point out that the protective properties in the CAP/G-A setting are myth insofar as fire-proof/fire-resistant properties go. While the chances of an aircraft fire are pretty remote, if you do have a fire, the you're better off in a pair of jeans and leather jacket than in a thin flightsuit.

The second reason is cost. With zero advantage in our operating setting, money spent on nomex is a waste if one thinks they're getting enhanced protection from it. A cotton flight suit made from a slightly heavier weight (6 ounce) would offer more true protection and cost considerably less.

I wish people would be more honest and just admit they like the green bags because they look cool and they get the rub-off 'coolness' factor because military aircrew wear them.

[IceNine]

Very nice assesment.

Now do all of those pockets have actual designed uses or are they just for stuffing random stuff in? 

I am just about to order my Zoom-Bag (because I think they are cool) 

[CASH172]

They're real cool.  I always get stares since I'm usually the only cadet wearing one anywhere. 

[fyrfitrmedic]

I was somewhat intrigued by the (presumed) belief that the green nomex flight suit is somehow a safety item in the CAP setting. It's been known for decades that nomex is/was designed for use in short-duration, high-temperature, flash fires. The design scenario was based upon a the premise that a few seconds of protection was needed to allow the wearer to escape (eject) from a burning aircraft. These suits do not protect from heat and will not prevent heat transfer (to your skin). It was intended that a wool or cotton undergarment would be the first-line defense from the heat -- again it was assumed that the duration of protection was to be a few seconds (3 seconds, IIRC).

Current USAF flight suits are 4.5 ounce nomex fabric -- about the same as a middle-of-the-road t-shirt. In a general aviation setting (i.e. avgas fire), nomex provides provides no more protection than street clothes of similar fabric weight.

Citation as to protection please?

In my past experience working in industrial emergency response, I've seen better results than that from 4.5 oz Nomex coveralls in subjects exposed to hydrocarbon-fuel fires for greater than three seconds. That includes an industrial accident involving an immediate family member.

[Hook]

Here are some older tests performed by the Army/Thiokol.  PDF is a link from this page.
http://stinet.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0664122

Here is NAVAIR testing from mid-80s
http://stinet.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA197512

[riffraff]

Citation as to protection please?

Google "nomex" and read away. If your relative survived a flash-fire, then I would agree that nomex (Proban, etc) probably helped. However, in a prolonged low-temp fire of prolonged duration (i.e. you have no chute and your CAP airplane has a open-flame, avgas fire in the cockpit while you're cruising along at 9,000 feet), nomex will provide absolutely no additional protection factor beyond natural fiber clothing of the same fabric weight/density.

Hold your mil-spec suit up to the light and tell me how much light comes through. Those same holes are where the heat will be coming through, along with direct heat transfer across the fabric to whatever is underneath. Back in the day, long-johns and insulated top were worn underneath the suit to provide a thermal barrier. Most folks today just wear the suit over shorts and t-shirt -- i.e. nothing to stop direct heat transfer to your skin.

Take a look at what a Nascar driver wears. True it's nomex but with a pretty thick insulating layer to protect against burns -- essentially a less bulky version of the fire departments bunker pants/jackets. These padded suits have a protection rating measured in seconds.

I would agree that flight suits look cool. I wear mine for the same reason but am not under any illusions that it's a matter of safety.

Some basic info:
"Nomex® also is used in apparel worn by military pilots and combat vehicle crew; auto racing drivers, pit crew members and track officials; and industrial workers at risk from flash fire and electric arc hazards."
source: Dupont pres release celebrating 40 years of nomex

From Personal Protection report. Note the reference to flash fire:
http://personalprotection.dupont.ca/pa_pdf/H-45528-02-01NOMEX-Case.pdf

There are hundreds of articles, reports, studies all supporting the benefits of nomex in flash fires.

Edit: Fixed obnoxiously long DuPont URL -TA

[Hawk200]

Nomex by nature is fire-resistant. Cotton or most natural fiber is not. Wool is close, but not completely.

Saying that Nomex offers no protection because it's the same weight as some heavier weight t-shirts is rather ignorant. The statement doesn't even account for the properties of the two materials.

But to simplify: If you're passing through a fire wearing a cotton shirt, it's going to ignite, and you're now carrying a fire with you. Nomex will char, but will not ignite unless exposed to high temps for longer periods. In five seconds, cotton will ignite and burn. Nomex won't.

Overall, it is a safety item. Do we need that level of protection? Probably not. For what I can get flightsuits for, it's worth the money.

[riffraff]

Nomex by nature is fire-resistant. Cotton or most natural fiber is not. Wool is close, but not completely.

Saying that Nomex offers no protection because it's the same weight as some heavier weight t-shirts is rather ignorant. The statement doesn't even account for the properties of the two materials.

Obviously you can believe what you want. Nomex will not prevent heat from transferring to your body. In a G-A fire scenario, it's the thickness of the material that affords the very limited protection from being burned and it's the heat that causes tissue damage.

Nowhere did I say that nomex didn't offer fire protection because of its weight. I said it doesn't afford any protection because its properties weren't designed to protect in a long-duration, open flame type fire scenario. Nomex was meant for flash fires.  It's a very simple premise: thicker, non-combustible materials afford more protection than thinner, non-combustible materials. 4.5 ounce nomex is not very thick.

[Hawk200]

Obviously you can believe what you want. Nomex will not prevent heat from transferring to your body. In a G-A fire scenario, it's the thickness of the material that affords the very limited protection from being burned and it's the heat that causes tissue damage.

Agreed. It won't stop heat transfer. The difference is whether heat is being transferred or whether or not you have fire directly on your skin. That's where the fire resistance makes the difference. I'd rather have fabric that's hot and charring next to my skin than actual flame. There's a major difference in the temperature.

Nowhere did I say that nomex didn't offer fire protection because of its weight. I said it doesn't afford any protection because its properties weren't designed to protect in a long-duration, open flame type fire scenario. Nomex was meant for flash fires.  It's a very simple premise: thicker, non-combustible materials afford more protection than thinner, non-combustible materials. 4.5 ounce nomex is not very thick.

Your first post seemed to imply that there was no protection difference between a Nomex garment and a well made T-shirt. My mistake.

What doesn't seem to be addressed here is that fire is fire. Period. It doesn't matter if I'm a CAP 172, or a Blackhawk. Either way, the fire is going to burn you. Considering the flashpoint of JP8 compared to avgas, nomex is going to give you even more time in a GA setting than in military aircraft.

And Nomex wasn't designed for flash fires. It was designed to be fire resistant. The nature of the fire is a moot point. Avgas probably burns at lower temps than military aviation fuels. Besides, all fires start with a spark. Although, it is less likely that you will get a fireball in GA as opposed to the military. Nomex will protect you either way.

If Nomex was only used in a flash fire type of environment, then firefighters probably wouldn't wear it. Just about everyone has seen firefighters going in to a building that's already burning. Why would they wear something that wouldn't offer any protection in sustained fires?

So, do we actually need Nomex? Maybe not. But having a little extra time is always a plus.

[NIN]

I wish people would be more honest and just admit they like the green bags because they look cool and they get the rub-off 'coolness' factor because military aircrew wear them.

Argh, you caught me.

Then again, those military aircrew wings on my nametag might mean I have some knowledge.

I'd rather take my chances with my Nomex, thanks. 

[O-Rex]

simply put, at extremely high temps, Nomex chars, instead of burning or melting.

Historically, CAP wears them for the same reason it wears BDU's: because in the past, they were easy to obtain.

[fyrfitrmedic]

Citation as to protection please?

Google "nomex" and read away. If your relative survived a flash-fire, then I would agree that nomex (Proban, etc) probably helped. However, in a prolonged low-temp fire of prolonged duration (i.e. you have no chute and your CAP airplane has a open-flame, avgas fire in the cockpit while you're cruising along at 9,000 feet), nomex will provide absolutely no additional protection factor beyond natural fiber clothing of the same fabric weight/density.

That doesn't count as a citation, nor does advertising product from the manufacturer.

The fire in question was not a flash fire.

I suppose you're going to tell me next that what I've personally witnessed in industrial emergency response was hallucination?

[riffraff]

fyrfitrmedic: I'm not going to debate the particulars of an industrial accident in which no information is provided beyond an authoritative opinion by you that nomex saved the person involved. I'm happy the person survived.

I can tell you for fact that nomex was designed for protection against flash fires. In particular, it was designed to provide 3 seconds protection against rapid combustion of atomized jet fuel (JP-4) in a pressurized environment (simulated aircraft cockpit).

In a flash fire environment, Nomex fibers swell up and close up the weave of the fabric during the carbonization process (conversion/dissipation of heat) and delays the heat transfer from the outside of the garment to whatever is inside (3 seconds for mil-spec 4.5 ounce sage green nomex). The scenario presumes ignition of a fuel vapor cloud -- ie flash fire. Upon completion of the carbonization process, the remains of the fabric become very brittle and break easily.

In a G-A fire, the fire-resistant feature remains but the fibers do not swell and close up. The relatively low temperatures pass directly through the weave and transfer upon whatever is beneath.

Nomex is fire-resistant, not fire proof. Technically this means it will self-extinguish when the ignition source is removed. It's also a misleading representation. Nomex does burn. It just stops burning when removed from the ignition source. Many other materials are also fire-resistant and/or self-extinguishing including leather and some natural fibers. However, all retain heat and all will transmit that heat to any exposed underlying tissue -- i.e. you can still be severely burned.

As for ads by DuPont: They created Nomex. Their spec sheets clearly spell out the time durations of protection for their various safety garments. Their mil-spec nomex specs clearly state flash fire protection. The Navy has the earliest data on Nomex -- going back to 1965. The mil-spec was written around the DuPont test data. Write to DuPont for the specs. It's what I did. You can also look at their newest tests using Thermo-Man -- a mannequin loaded with test sensors to measure temps inside the various fabrics in flash fires.

[fyrfitrmedic]

Riffraff:

Some links to the spec sheets would be useful.

At the risk of picking nits, Nomex fabric simply doesn't go >poof< and vanish away after three seconds. I know this from industrial incidents to which I responded previously and I know this from my own experiences, including having had bunker gear I was wearing take the full brunt of a rollover.

Nomex is far from a panacea, but it certainly buys more time than would street clothes.
   

[riffraff]

I will try and scan the data sheets I have later this weekend.

I don't disagree with most of your comments. My posts were somewhat pointed to promote discussion, not be confrontational.

This is more an academic exercise than anything else but hopefully will have folks think about what they're wearing and why they're wearing it.

I'm not personally aware of any G-A accidents involving inflight fires (but have seen/been involved with several military). I'm sure there have been some, at some point, but I have no first-hand knowledge of any in the G-A setting (I've been flying since 1980). This excludes post-impact fires from catastrophic accidents (non-survivable/cause of crash was not fire related). I've not been in CAP very long but would presume that there have been very few, if any, inflight infernos?

For nomex vs street clothing, I would add that the major variable would be composition of clothing. A pair of poly-blend pants will go up in flames, regardless of thickness, etc. A pair of 100% wool trousers will provide a thermal barrier equal to nomex -- given all other factors are equal.

I would like for those reading to think about what they're wearing beneath their nomex. If you wear any blends (polypropylene long johns, cotton/poly t-shirts, etc), bear in mind that these items will ignite and nomex will do an equally good job keeping the heat inside your suit as it does keeping it out! Blaze orange nylon briefs and a black poly t-shirt with screened on logo will become permanent, baked on fixtures if you're unfortunate enough to be in a fire. Hey, I'm not judging, just making an observation 

When I was flying, we were issued nomex long johns and nomex tops. If not worn, white cotton was required. Reason: it takes longer for the heat to penetrate the additional fabric thickness and light colors reflect radiant heat while dark colors absorb it.

[fyrfitrmedic]

For nomex vs street clothing, I would add that the major variable would be composition of clothing. A pair of poly-blend pants will go up in flames, regardless of thickness, etc. A pair of 100% wool trousers will provide a thermal barrier to nomex -- given all other factors are equal.

I would like for those reading to think about what they're wearing beneath their nomex. If you wear any blends (polypropylene long johns, cotton/poly t-shirts, etc), bear in mind that these items will ignite and nomex will do an equally good job keeping the heat inside your suit as it does keeping it out! Blaze orange nylon briefs and a black poly t-shirt with screened on logo will become permanent, baked on fixtures if you're unfortunate enough to be in a fire. Hey, I'm not judging, just making an observation 

My instructors called this the "shrink-wrap effect" 

I think you're utterly spot-on about this; what's worn *under* the Nomex is equally important.

Until recently there was a dearth of flame-resistant undergarments that weren't Nomex-brand. These days brands like FlameX and XGO are available.  At a previous job we'd gotten samples of XGO; their stuff wasn't bad.

[Hawk200]

A pair of 100% wool trousers will provide a thermal barrier equal to nomex -- given all other factors are equal.

I would like for those reading to think about what they're wearing beneath their nomex. If you wear any blends (polypropylene long johns, cotton/poly t-shirts, etc), bear in mind that these items will ignite and nomex will do an equally good job keeping the heat inside your suit as it does keeping it out! Blaze orange nylon briefs and a black poly t-shirt with screened on logo will become permanent, baked on fixtures if you're unfortunate enough to be in a fire. Hey, I'm not judging, just making an observation 

When I was flying, we were issued nomex long johns and nomex tops. If not worn, white cotton was required. Reason: it takes longer for the heat to penetrate the additional fabric thickness and light colors reflect radiant heat while dark colors absorb it.

I wouldn't say wool is equal, but probably about 80 percent. Wool is close enough that the Air Force has actually been testing wool undergarments (among others) for wear with flightsuits.

While flying on Blackhawks, I wear cotton underneath. At least until I can afford some fire resistance stuff. Right now, getting a shirt in the proper color is difficult. The Army has a cotton shirt to wear under flight gear, but it's in the foliage green color. The reasoning is that the rest of the crew knows that your not wearing the polyester shirt because the green one is only made in cotton. And the old brown one is permitted. With the A2CU, the tan shirt isn't even authorized.

Any know if there's a manufacturer out there making fire resistant underwear in foliage?

[PHall]

I'm not personally aware of any G-A accidents involving inflight fires (but have seen/been involved with several military). I'm sure there have been some, at some point, but I have no first-hand knowledge of any in the G-A setting (I've been flying since 1980). This excludes post-impact fires from catastrophic accidents (non-survivable/cause of crash was not fire related). I've not been in CAP very long but would presume that there have been very few, if any, inflight infernos?

There's been more then a few. The "most famous" being being the in-flight cabin fire that killed "The Big Bopper" and Richie Valens in 1959.
Those old gasoline fueled cabin heaters used back then were an accident looking for a place to happen.

[NIN]

And the fire that killed Ricky Nelson in a DC-3...

While inflight fires do happen, the chances of them occurring in your average GA bug-smasher are pretty slim.    They don't even happen that often in military aircraft with all the CRFS and things like that. Heck, I bet the incidence of inflight fire went down a little when they banned smoking on DoD aircraft...

Honestly?  All this talk of heat transfer, 3 second flash fires and such essentially boils down to utter bull[mess] unless you've either been thru an aircraft fire or had to witness the aftermath.

I've not been thru the former, I have had to deal with the latter on more than one occasion.  Suffice to say, I'll take my chances with the protections afforded by Nomex no matter what the modality of the fire versus wearing "brand x" while flying. 

I do agree that *generally* Nomex is probably overkill for CAP ops. 

But I think back to something my helmet, leathers, boots and gloves-wearing father said to the kid on the crotch-rocket wearing nothing but thin nylon running shorts, sneakers and a pair of sunglasses  and laughing at him for being "overdressed":

"If I knew when it was I was going to need it, I'd only wear it then."

[PhotogPilot]

I'm not personally aware of any G-A accidents involving inflight fires (but have seen/been involved with several military). I'm sure there have been some, at some point, but I have no first-hand knowledge of any in the G-A setting (I've been flying since 1980). This excludes post-impact fires from catastrophic accidents (non-survivable/cause of crash was not fire related). I've not been in CAP very long but would presume that there have been very few, if any, inflight infernos?

There's been more then a few. The "most famous" being being the in-flight cabin fire that killed "The Big Bopper" and Richie Valens in 1959.
Those old gasoline fueled cabin heaters used back then were an accident looking for a place to happen.

Not to nit-pick, but....according to the CAB accident report....

The accident occurred in a sparsely inhabited area and there were not witnesses. Examination of the wreckage indicated that the first impact with the ground was made by the right wing tip when the aircraft was in a steep right bank and in a nose-low attitude. It was further determined that the aircraft was traveling at high speed on a heading of 315 degrees. Parts were scattered over a distance of 540 feet, at the end of which the main wreckage was found lying against a barbed wire fence. The three passengers were thrown clear of the wreckage, the pilot was found in the cockpit. The two front seat safety belts and the middle ones of the rear seat were torn free fro their attach points. The two rear outside belt ends remained attached to their respective fittings; the buckle of one was broken. None of the webbing was broken and no belts were about the occupants.

Although the aircraft was badly damaged, certain important facts were determined. There was no fire. All components were accounted fro at the wreckage site. There was no evidence of inflight structural failure or failure of the controls. The landing gear was retracted at the time of impact. The damaged engine was dismantled and examined; there was no evidence of engine malfunctioning or failure in flight. Both blades of the propeller were broken at the hub, giving evidence that the engine was producing power when ground impact occurred. The hub pitch-change mechanisms indicated that the blade pitch was in the cruise range.


Conclusion

At night, with an overcast sky, snow falling, no definite horizon, and a proposed flight over a sparsely settled area with an absence of ground lights, a requirement for control of the aircraft solely by reference to flight instruments can be predicated with virtual certainty.

The Board concludes that pilot Peterson, when a short distance from the airport, was confronted with this situation. Because of fluctuation of the rate instruments caused by gusty winds he would have been forced to concentrate and rely greatly on the attitude gyro, an instrument with which he was not completely familiar. The pitch display of this instrument is the reverse of the instrument he was accustomed to; therefore, he could have become confused and thought that he was making a climbing turn when in reality he was making a descending turn. The fact that the aircraft struck the ground in a steep turn but with the nose lowered only slightly, indicates that some control was being effected at the time. The weather briefing supplied to the pilot was seriously inadequate in that it failed to even mention adverse flying conditions which should have been highlighted.

Probable Cause

The Board determines that he probably cause of this accident was the pilot's unwise decision to embark on a flight which would necessitate flying solely by instruments when he was not properly certificated or qualified to do so. Contributing factors were serious deficiencies in the weather briefing, and the pilot's unfamiliarity with the instrument which determines the attitude of the aircraft.

By the Civil Aeronautics Board: James R. Dupree/ Chan Gurney/Harmar D. Denny/ G. Joseph Minetti/ Louis J. Hector