Civvy/Mil Standards
Joined: Jul 2004
Posts: 46
Likes: 0
From: Canada
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.
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.
Joined: Apr 2006
Posts: 14
Likes: 0
From: USA
Simpler view
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.
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.
just watch the S-92 - trust me.
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.
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.
just watch the S-92 - trust me.
Last edited by Deiceman; 16th March 2007 at 20:05. Reason: typos
Joined: Nov 2004
Posts: 1,334
Likes: 0
From: Cambridgeshire, UK
Originally Posted by Nick Lappos
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.
Mart
Joined: Feb 2005
Posts: 340
Likes: 1
From: KPHL
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.
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.
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
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!
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!
