Civvy/Mil Standards

[rotorfloat]

From a design standpoint, what are the differences between a helicopter built to military-only specs vs one destined for FAA/JAA certification?
Blackhawk and S92 being 2 examples.

[Matthew Parsons]

I'm not aware of an exhaustive list of differences. Is their a design area you're considering in particular?

[Bertie Thruster]

ejector seats

[rotorfloat]

Ejector seats in a blackhawk eh?

I mean, what is different in the standards that prohibit, say, a blackhawk or a lynx from meeting civil certification?

I understand that doing so would cost a fortune. What's so different?

Whereas, on the other hand, for example, S92 variants were intended for civil/mil certification from the ground up.

[unstable load]

I would think that the basic design principles would be the same with the emphasis on military stuff being from the point of view of survivability and the expected hazards of being under fire etc, whilst the civvy stuff will be more from a commercial point of view with regards to operating costs, maintenance intervals and the old bottom line of the $$.

The main issue for civvy machines would be from the legal point of view with liability and certification issues topping the agenda to keep the manufacturer out of court in the event of a catastrophe/incident that could in any way be laid at their feet.

That's my take on it, but I am sure there are more qualified folks out there who could better answer this.

[topendtorque]

military-only specs

being able to crawl away from a vertical descent of 1500??? ft/min without use of collective was one of them I thought, way back when?

[NickLappos]

The question is a good one, and the answer will suprise ppruners who think of military as strong and civil as weak.

Generally the requirements match the job, and neither is "stronger", but lately, there isn't much difference, when the military buys civil aircraft and paintes them in fighting colors.

The Black Hawk was designed to US Mil standards, and does not meet FAR, it is much better in some ways, not as good in others. If you are being shot at, it is a dream, however! It is so different that it cannot be civil certified. Look at the S92 as what the BH would be if it met FAR, that is precisely why Sikorsky made the 92.

[Brian Abraham]

Nick, Just out of idle curiousity in what areas would the Black Hawk not meet FAR standards? Certainly not performance I'd imagine.

[NickLappos]

Actually, there is no precise mil standard for OEI performance, so the H-60 family meets no defined OEI standard! It is a screamer, but in FAA minds an unmeasured screamer.

The list goes on - one wonders what the ballistic tolerance of the EC-145 is, or how its crew is protected in crashes. The Huey it beat (and that was briefly a competitor) meets 1956 criteria! Similar questions can be asked about the 407.

[Graviman]

Actually, there is no precise mil standard for OEI performance, so the H-60 family meets no defined OEI standard! It is a screamer, but in FAA minds an unmeasured screamer.


That's an interesting one, Nick. Particularly since the subject of engine reliability comes up from time to time on this forum. What criterion should be applied for determining OEI performance of a helo?

Mart

[RVDT]

It is a screamer,...........That part would be courtesy of GE wouldn't it?

[diethelm]

That would seem to make non-FAR certified military aircraft technically as restricted category prohibiting them from flying over congested areas. However, I suspect as long as the military is using them they can fly over congested areas. Which then of course raises the logic question; if the military can fly a restricted category aircraft over congested areas why can't any one else?:confused:

Or another one, can a manufacturer fly a restricted category aircraft over a congested area like the military or can only the military fly a restricted category aircraft over a congested area? :ugh:

Which raises the obvious answer which is if the military is flying it, it is not restricted category but if a civilian or manufaturer is flying it, it is a restricted category aircraft which of course would make not one iota of common sense....:sad:

[wg13_dummy]

Military = Cheapest products with the most expensive price tag.

Civil = Most expensive products for the cheapest price.

[Shawn Coyle]

The list of differences is huge, and as far as I know, never fully defined.
Nick is right about the H-60 being a screamer as far as single engine performance goes at the design weight. And definitely the helicopter I'd want to be in to go to war in anything other than a gunship role. But the failure modes of things like the stabiliator wouldn't pass the civil standards, for example.
On the other hand, lots of new military machines are required to meet civilian standards for reasons that have nothing to do with military requirements, and lots to do with reducing the cost of maintenance.

[bayou06]

Nick,
Please expound on your statement regarding the certification of the B407. I know the B407 is a derivitive of the OH-58D and the B206 family. I understood the B407 was certified under the B206 certificate. Why do you say that there are questions on the certification of the B407?

BTW, I fly a B407 in the GOM and really love the way it performs. You can fly it with full seats and a full bag of gas. I've found that it takes a subtle control touch to fly well though.

Thanks for your insight.

Bayou06
B407 Driver

[flyby_heli]

What about the two Black Hawks that are being used for firefighting in Florida, the Firehawks? As far as I remember from the pictures I have seen, they have N-reg and no decals saying restricted anywhere. Anyone know what mods, if any, has been done to get those registered as civvy aircraft??

[rotorfloat]

flyby_heli, I think there's a few firehawk drivers on the boards here that can elaborate, but I'd guess that it's being operated by a government agency under a restricted CofA, ie, not for commercial use. Similar to police forces using exmil machines.

Nick, do you mean to say that ballistic tolerances are outdated? I recall somewhere that the MI24's canopy can withstand .50 cal rounds? Are any western machines as tolerant?

As for the OEI performance on the BH, does that mean you did no OEI flight testing or performance charts at all? Is there any OEI transients published?

If a crew were to have OEI, do they just adjust the controls as necessary to maintain desired flight (pull till the Nr horn comes on :} )

[22clipper]

A year or so ago the Danish airforce were off loading a bunch of H500s with heaps of spares. There were lots of rumors down here in Oz 'bout how you wouldn't touch 'em with a barge pole 'cause they wouldn't be certifiable in Australia. Everyone spoke like it was black & white, an open & shut case.

But there is at least one ex Kiowa with proper VH reg flying around down here. The owner runs it in the experimental class. As near as I can see he has the best of both worlds. He can modify the console to fit a mobile phone or whatever without all that TSO drama & the VH reg means he can fly it anywhere.

[perfrej]

From what I learned, an ex military machine - even though civilian from start like the Danish ones - cannot be certified to civil standards unless all maintenance history is traced, re-written to civilian standards, and found to be in compliance with the civilian standards throughout the history of the individual. Even though military organizations have excellent maintenance, like our Swedish military administration, their maintenence records are incompatible with the civil ones and they go by their own rules. Today, all maintenece of new military machines is performed and documented to civil JAR specs, which means that the new A109 Powers that have rolling in to the armed forces will have a market value when they are taken out of the military.

You can usually - in Europe - get a restricted category civil reg for an ex mil, but then someone has to have an approved EASA type certificate (supplemental) for the machine in question. Take the UH-1H, for example. There are seven approved STCs for UH-1H in the U.S., six of which were approved in Spain by the time they joined the EASA a few years back. So, if you have a Huey which is already on that STC it can be imported to Europe (if the yanks let you get am export certificate). If you find a military Huey, it can be certified on those STCs if the owner of the STC apporves it (expensive), then civil regged in restricted category, which usually means no cargo or passengers transported for hire, and that all on-bord must have a place in the mission crew. Basically, private flying and heavy lift in other words.

I'm ranting...

[NickLappos]

Lots of questions/clarifications:

Graviman - Military OEI criteria - Who cares? When you are going into battle, the standard is first operational capability (number of enemy dead, amount of territory gained) then your attrition, then your cost. Far different game than a civil equation of excellence! Remember, an Army General carefully calculates how many of his men a hill is worth. "Saving Private Ryan" was only slightly fictional...thus ballistic tolerance and survival after shootdown are valued more highly than the more improbably engine failure performance.

diethelm, a military or civil government can "mint" their own certification, and they are not bound by FAA/JAR rules in any way. There is not a way for the FAA to govern military certification or operations except when the military agrees to do so. A spitfire never saw a CAA inspector, and who cares, anyway? Winning a battle means calculations that care not a whit for what a civil standard means. In other words, a Kamakazi fighter probably is not Catagory A, and its reserve fuel included no need for an alternate!

wg13_dummy, I don't agree that mil machine are cheaper, at all. They are usually much more per pound than a similar civil helo. They spend their coin on different aspects, like a big torpedo to drop, or a turret that slews quickly and shoots fast. These attributes are expensive and important, and do not at all add to safety.

bayou06, I said nothing about a 407's civil certification, which is IMHO very nice. I said it meets no modern criteria as a military scout except that it is cheap. Anyone who goes into battle in an Apache or Black Hawk, (or would have in a Comanche) is in much better stead to come home that in a 407, which was bought by the Rumsfeld bunch that trades "now, cheap and poor" for "future, more expensive and excellent" with abandon. If you shoot the same bullet at a Black Hawk and a 145, you will get far far different damage, and that is the problem. The Army boards who set up the standards to which the H-60 and 64 were designed did so by tracking every bullet path of every hit in 3000 Hueys from Vietnam, and these standards made the survivability of these types fantastic. These rules were also applied to the Comanche, and the other helos bought by AVSCOM (the engineers hired by the Army to develop new helos). The "new" DoD of this modern era abandoned the rules, bypassed AVSCOM and just bought civil stuff off the shelf, and a generation of soldiers will pay.

flyby_heli, The firehawks are just Army Black Hawks with restricted tickets, which means that they can only fly the same missions as the Army flies, and that they cannot be used for hire with pax - everybody on board must be crew in some form or another (firefighters are crew to the mission at hand).

rotorfloat, I have no idea how my words sparked your confusion, except my ineptness at explaining. I am saying that the latest round of US Army purchases meets no ballistic or crashworthy criteria, and thus are a step backwards, and somehow you drew the opposite conclusion. Oh well. Furthermore, there is no rule that the H-60 had to meet about OEI performance, but it of course was tested to show its capability. This was a design fallout, not a hard requirement, if you understand the difference. Thus it is a screamer, but not by design and with little published data to back that up.

perfrej, There are two cases, and I think you mix them up a bit:
1) The machine is ex-military and no civil counterpart exists, like a Black Hawk or an Mi-24. It can be "certified" to ebter civil service as restricted, see above for that definition. No pax for hire, ever.
2) The machine has a civil design that has been fully certified, but the serial number machine you want to induct into civil commercial service is ex-military (because the military service that used it has low standards and bought it to begin with). In this case you must show that the machine you have is exactly (part by part) like its civil sister ships and that the exact machine you have has been maintained to the civil flight and maintenance manuals (part numbers, retirement intervals, and flight manual operating limits). Not a small task.

[plt_aeroeng]

Nick has fairly accurately captured the essence of the differences between civil and military certification.
There are some examples of crossing between the two categories.
Lockheed, for example, as a private venture decided to get FAR25 certification for its C130J, derived from a military airlifter. It learned some very expensive lessons about the process. It then learned some more expensive lessons when getting USAF certification for operational use.
Another good example is the Canadian "Griffon" tactical helicopter, which was bought as an off the shelf Bell 412 (civil certified). The Bell 412 can be loosely characterized as an updated civil certified twin Huey. Originally, Bell had suggested using a combined parts pool for civil and military parts, but had to segregate them all. Because of military procedures and operating conditions, parts could go from the civil pool into the military one, but not back.
However, there is a trend towards using FAR29 as a guide in designing newer helicopters, and some militaries are even using FAR29 compliance analysis in their selection procedures. Even crashworthiness, which Nick uses as an example of the differences, is converging in terms of the MIL-STD-1290 and FAR29 requirements. (If you look at AC-29C, you will even see a reference to MIL-STD-1290 for the fuel system.)
The militaries will continue to have features that have no civil equivalent, and still like to have things such as MIL-STD-1553B data buses which can't be civil certified (due to common failure mode issues, in part). For many airworthiness topics, the end goal is similar, though.
In the end, though, the desire to make helicopters last and not fall out of the sky is a powerful incentive to follow the best of both certification regimes.

[Deiceman]

In my simpler frame of reference, I believe the major difference between civvy and camo is the specification.

Military aircraft meet the military's specifications. If the spec is screwed up, so is the aircraft. Often improvements are not included as they are "not in the spec". Safety is never usually an issue, and as Nick says, ballistics are often a factor - but of course they are usually in the spec.:8

The FAA cares about safety - no laffing please - but essentially they can say " as long as it's safe, we don't care if it has a range of 8 miles and carries 2 people" - as long as it was intended to have a range of 8 miles and carry 2 people! It must meet it's intended function.
The Market will determine the other features that are traditionally in a spec - range, cost, payload etc.

So a commercial manufacturer will strive to get the best performance (or DOC or whatever) so that he can sell it - the FAA ensures it is safe.

Now, IF your design anticipated military requirements while designing a commercial helicopter, but don't burden the commercial viability - you have a winner.:D

just watch the S-92 - trust me.

[perfrej]

Lappos!

Point taken. Would a UH-1H not be equal to a 205?

[Graviman]

Graviman - Military OEI criteria - Who cares? When you are going into battle, the standard is first operational capability (number of enemy dead, amount of territory gained) then your attrition, then your cost. Far different game than a civil equation of excellence! Remember, an Army General carefully calculates how many of his men a hill is worth. "Saving Private Ryan" was only slightly fictional...thus ballistic tolerance and survival after shootdown are valued more highly than the more improbably engine failure performance.


Good point well made. Thanks Nick.

Mart

[Matthew Parsons]

I can't speak about every military in the world, but in general I think this attitude that military requirements are unconcerned about safety but are all about mission performance is completely invalid. I agree with what Nick has said, but the overall airworthiness situation goes beyond those specific examples.

For civilian and military airworthiness it is not about making something 100% safe. It is about making a product that carries an acceptable risk. To determine overall risk, you have to look beyond the failure modes and get into how the helicopter is being flown. The role itself comes with risks that airworthiness authorities must mitigate or accept. That becomes quite obvious in the military, such as the ballistics that has been discussed.

Another part of the role is what do you need your product to do to complete the role? A good example is the Bell 412. According to rumour, a civilian variant is limited to 5 degrees in a slope landing. It was determined that was insufficient for the Canadian military variant, so we had it increased to 10 degrees. The outcome of that is life of some parts is changed, so those parts don't go to civilian machines. Simple as that.

In Canada we've split airworthiness into three parts: operational, technical, and accident investigation. Apparently this model is being used by other countries and is gaining popularity. On the technical side its all about meeting specification requirements, proving equipment function, and determining safety. I spend much of my time reading through FAR and JAR documents in the process of obtaining military technical airworthiness.

A good example of how risk is mitigated is with OEI performance. For certain categories of civilian aircraft you have to load and/or fly your aircraft in such a way that you can lose an engine at anytime and successfully recover your aircraft. Other categories of civilian aircraft are certified to fly deep in the avoid curve with only one engine. The reason for the apparent disparity is because the mission needs to be done at a cost that is acceptable, and the risk when its just a pilot on board versus having many passengers is quite different.

In the military we are concerned with OEI performance. Whether you lose an aircraft to an RPG or an engine fail...you've still lost an aircraft, and perhaps the crew on board. We generate/validate data to help our pilots know what they can do when the engine fails. They and the commanders will know when the helicopter has poor OEI performance, and will consider the associated risks when mission planning. If it is fly into enemy fire to pick up some people who have no other out...probably not too concerned with OEI performance. If the mission is to demonstrate the capabilities of the machine to tens of thousands of people over/near populated areas...you'll probably find the orders demand a lighter helicopter.

Nick brought up a good point that is an unfortunate reality with todays budgets. The risk assessment now includes cost. A cheaper solution that comes with more risks may be accepted. Of course, this is not unique to military aviation, in fact it has been borrowed from civilian aviation, or more generally, from business.

[NickLappos]

Well said, Matthew!
I must be sure my words came out right, the military has concern for crew safety, but the risks are different. Crashworthiness and ballistics are worth more than OEI performance, for example, if the crew is to be saved.

What concerns me is the new purchases that toss all this old-think away and just buy cheap!