LSA -coments on the rules as it affects design

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Aircar

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Until just a few days ago I had not read the detail on the rules for LSA aircraft under the US rules and only peripherally followed the stories for and against LSA aircraft or whether or not it has flopped or expanded .

One provision that caught my eye was the limitation to just ONE engine (ruling out hybrid power apparently and the idea of a back up electric motor or even I suppose on board recharging by gasoline engine --for example the Rutan BiPod -- I can see why wing mounted twins might be restricted from at least initial relaxed training and operation standards (the assymetrics and control loss issue ) but not why any 'standby' second motor should be excluded on safety grounds .

The second thing was the prohibition of "lift enhancing devices" (even if the stall speed without such use was still below 51mph (itself an absurd figure --related to "51"% construction perhaps ) --is this a correct interpretation ? (and again no retractable landing gear except for a glider -- are these provisions anywhere justified ?

The Terrafugia roadable was unflapped and displayed attrocious take off and landing ability yet seems to meet the letter of the law --it seems to be an inherently bad specification if it sets a maximum full throttle airspeed and thereby penalizes a clean aircraft to have a higher power loading (more pounds per horsepower ) and hence a lower climb rate than a lighter but draggier design. seems like a bad specification .(as nearly always results from specifying arbitrary design limits or criteria which both limit competition (or unreward improvement) and define a bad result much like the original Australian ultralight category which specified a 400lb aircraft plus pilot plus fuel AUW and a 4lbs per sq ft wing loading (and a max height of 400 ft plus no crossing of made roads etc ) --later admitted to be set because there were no aircraft of that specification in existence (or Janes' all the worlds aircraft at least )

What has been experience so far with the LSA category from a design viewpoint.?
 

Dana

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I think you misunderstand a couple of points. The requirement for a single engine is, as you surmise, due to the higher pilot skill required to handle an engine out in a twin (whether asymmetric or just 50% power loss). I don't think it would be applied to a hybrid system, but nobody's tried to certify one yet. Ditto for retractable landing gear or controllable propellers; the goal is to keep the cockpit controls as simple as possible. Note that for retracts and controllable prop even a Private pilot now requires a "complex endorsement".

Flaps or other lifting devices aren't prohibited at all; the rules only say that the aircraft must meet the stall speed limits with flaps (if present) retracted.

The biggest complaint here is the weight limit, as it excludes quite a few older aircraft that would otherwise be suitable.

-Dana

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Aircar

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OK Dana I'll reread the bit about 'lift enhancing' - I had written to Terrafugia before their first flight about the trim problem they would encounter and how to add flaps that would not overwhelm the canard but got the "no flaps' quote but didn't follow up on that -- if complexity is the issue I can see why they might ban flaps altogether but if 'optional' that argument is moot . the 452 page version of the rule was too much like my bad memories of wading through turgid bureacratese so I am trying to get the expurgated version here.

I don't agree with the concept of some arbitrary physical quantity being specified which doesn't apply to any other everyday vehicle in that it has no definable significance --neither has maximum speed once you are a few hundred feet up (if flying downwind then the speed over ground for navigation or whatever is going to be much higher and with other aircraft in the air closing speeds likewise -- surely these things should be a PILOT function if anything just as we restrict the speeds for learner drivers and those on 'probationary' licences over here --as it is a 747 pilot off duty has to behave as if a neophyte .
 

autoreply

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While I'm not intimately familiar with the regulations, I think the limits are good ones. But history first. The Micro Light Aircraft category was initially created for powered trikes and the like. 1000 lbs MTOW, 35 kts stall, single engine, with much of the reasoning (too slow/simple to be dangerous) as the FAR 103.

But the last decade, this has evolved in designs that are almost as complex as a Bonanza or a Lancair. Look at the WT9 Dynamic for example. Retractable landing gear, fairly high approach speeds, extremely efficient flaps, variable pitch prop, turbo's Cirrus SR20-like cruise speeds...

Simply having a maximum stall speed encourages designers to use extremely efficient flaps. So you still have a very hot design and fairly high approach speeds on most landings. Cruise of the fastest MLA's is around 1750 mph, making navigation and G-loads considerably more complex. Fixed landing gear and fixed prop (another point of failure) make sense too for complexity and pilot work load.

As much as I'd love to see the top speed requirement removed, I do think it will quickly lead to "pocket rockets" that completely defy the idea behind LSA (simple, easy to fly aircraft).
 

Himat

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Until The second thing was the prohibition of "lift enhancing devices" (even if the stall speed without such use was still below 51mph (itself an absurd figure --related to "51"% construction perhaps ) --is this a correct interpretation ? (and again no retractable landing gear except for a glider -- are these provisions anywhere justified ?
As I understand it, the Icon seaplane have retractable gear and is designet to the LSA rules.
Have they got an exemption, or are seaplanes free to have retractable gear under the LSA rules?
(If seaplanes are allowed retractable gear and landplanes not, that open for some "creative" thinking to bend the rules.)
 

TFF

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When looking at LSA in the US you have to look at the plane and the pilots. The only advantage LSA has in the US is no medical is required. There is no other advantage. For pilots who cant get a medical it is a boon, best thing ever, and if you dont want to get medicals you have a place to go. Other than that you are arbitrarily restricting your self. In piloting, the FAA considers it a lesser license, and because of that, you are deemed to have a simple airplane.
When it comes to design in the US their are no penalties for a regular experimental; you dont have to declare your design LSA, if Experimental, just make it fit the flight rules. The only time you have to declare it LSA is if you want to sell ready to fly or kit it as LSA, which is a mistake, you can sell it in experimental and lose the restrictions. The truth is 2 average Americans dont fit in an LSA plane so it is usually the last place you go to fly here in the US. Right now it is just a fringe movement; I only know of 2 true LSA airplanes here. One, a C162, is used in a flight school but 99% of its flights are for private license because you cant buy a new 150 and one by a guy who has a bunch of planes including a Cheyenne 1 and just wanted a toy. All the other LSA fliers I know are flying Champs, Cubs, and Taylorcrafts.
 

bmcj

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The second thing was the prohibition of "lift enhancing devices" (even if the stall speed without such use was still below 51mph (itself an absurd figure --related to "51"% construction perhaps ) --is this a correct interpretation ? (and again no retractable landing gear except for a glider -- are these provisions anywhere justified ?
I suspect the 51 mph is just a conversion from 45 kts.


As I understand it, the Icon seaplane have retractable gear and is designed to the LSA rules.
Have they got an exemption, or are seaplanes free to have retractable gear under the LSA rules?
(If seaplanes are allowed retractable gear and landplanes not, that open for some "creative" thinking to bend the rules.)
Yes, I believe they make an allowance for retractable landing gear on seaplanes.


Cruise of the fastest MLA's is around 1750 mph.
1750 mph? Really?!? :gig:
 

BBerson

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Electric motors are not approved for Light Sport Aircraft at this time, internal combustion only.
see here:http://www.sportpilot.org/learn/final_rule_synopsis.html

No light single seat SLSA have been approved so far, (as far as I can determine after extensive searching). And no light engines have been approved in the U.S. That's a shame, because the rule was supposed to improve the light end of aviation. But instead, the rule has been abused and allows the sale of heavy two-seaters such as the 180 hp Carbon Cub.
 

Vigilant1

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The second thing was the prohibition of "lift enhancing devices" (even if the stall speed without such use was still below 51mph (itself an absurd figure --related to "51"% construction perhaps ) --is this a correct interpretation ? (and again no retractable landing gear except for a glider -- are these provisions anywhere justified ?
As Dana notes, the US allows flaps on LSAs, but the aircraft has to be able to meet the stall 45 KCAS requirement without using them. And, IIRC, in Australia your LSC rules differ from the US LSA rules in allowing use of high-lift devices to meet the stall requirement. Also, I think the Australian rules don't set a max top speed for LSC.

In the US the biggest gripe about the LSA rules is the 1320 lb MTOW. I'm not sure why a simple 1320lb two-place airplane with a slow stall speed is somehow safer than a more structurally robust 1500 lb airplane with the same performance. Those among us of a suspicious nature might think the low weight was designed specifically to exclude C-150s, C-152s, Tomahawks, and other relatively common and "recent" aircraft in order to artificially create demand and a new market segment for companies selling high-dollar tiny airplanes. The way the rule was developed (with much industry participation) would contribute to these suspicions. More of an "industrial policy" than a "safety policy". Naahh . . .

If the requirement for a Class 3 medical is dropped for private pilots (probably with some restrictions), the whole US LSA initiative will collapse. So, now we have a vested interest among some industries to keep the present medical rules in place. The FAA has no inherent motivation to loosen the rules (no FAA Administrator wants to answer press inquiries after some 70 YO has a heart attack and crashes his Piper into a school bus after the rules are relaxed, even if such things also occurred before the medical exams were lifted). Even some of our aviation interest groups (EAA, AOPA) might find that their loyalties are a bit divided on the issue.
 
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Hot Wings

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it seems to be an inherently bad specification if it sets a maximum full throttle airspeed and thereby penalizes a clean aircraft to have a higher power loading (more pounds per horsepower ) and hence a lower climb rate than a lighter but draggier design

It is a problem from that vantage point. Our part 103 has the same built in limitation and rewards high drag high power designs. I believe hybrid drive is the way around this problem, but so far no one has tried to see just how the FAA would interpret the "one engine" rule. If this does come up within the ASTM committee I can assure you that I will be arguing that one engine should be one primary source of power, and how that power is distributed to the air should be up to the designer and not the standards committee.

After all the whole purpose of the "one engine" rule is to create simple planes that don't require more than basic skill and attention from the pilot. As long as design with multiple motors has built in provisions to avoid asymmetrical thrust if one motor/prop combination should fail (easily detectable and manageable via software) then one should be able to argue that the hybrid drive train is far safer than a single internal combustion engine.

Since our part 103 has no limitation on using just one engine, or motor, that is where we might best prove, or disprove, the merits of a hybrid drive for aircraft. If it proves to be as much of an advantage for part 103 aircraft as I expect, then we would have a foundation from which to argue the case for hybrid LSA's.

Unfortunately as the ASTM standards as they are now, even if the FAA were to state that a hybrid drives are acceptable, make designing and building one to conform to the standards impossible. For example 5.9.1 says that engines must have a vibration survey done with a representative propeller. If the engine is never going to be directly connected to a propeller there is no way to satisfy this standard. We have also taken a look at setting standards for electric powered LSA's and have voted on a preliminary set of standards but at the rate this is progressing through the process I doubt if we will see any standards for several years.
 

Hot Wings

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The way the rule was developed (with much industry participation) would contribute to these suspicions. More of an "industrial policy" than a "safety policy". Naahh . . .

That is part of the definition of a "consensus standard". I do think there is some industrial/political manipulation of the standards. Even if it isn't intended the fact that there are voting members that have that have their time and expenses paid for by the companies for which they work tends to give them an advantage, if not on the actual vote, but on the overall direction that the committee takes and what areas get the most priority. Guys like me that have to pay our own way if we want to attend the various meetings and symposia are at a distinct disadvantage.

There are also representatives from the FAA and the DOT on the roster, but as far as I know they are non voting members.
 
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Dana

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When looking at LSA in the US you have to look at the plane and the pilots. The only advantage LSA has in the US is no medical is required. There is no other advantage.
Not quite. You can (at least theoretically) get a Sport Pilot certificate in less hours (and thus less cost) than a Private. A minor point perhaps since most people take longer anyway. There are also some advantages to the LSA registration: You can build an approved ELSA kit without having to comply with the 51% EAB rule. You can easily convert a SLSA (factory built) registration to ELSA and then do all of your own maintenance, and if you take the "16 hour course", do your own annuals, too.

-Dana

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Rom

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"(6) A single, reciprocating engine, if powered." It could be argued that the rule as written would limit the craft to to no more than one reciprocating engine. No mention of how many electric motors on board. Let the lawyers figure that out.
If one was designing electric craft that met the other catagories for LSA, I would go ahead and build it as an experimental and wait for the rules catch up.
 

autoreply

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1750 mph? Really?!? :gig:
Oops, that zero was too much, literally.
In the US the biggest gripe about the LSA rules is the 1320 lb MTOW. I'm not sure why a simple 1320lb two-place airplane with a slow stall speed is somehow safer than a more structurally robust 1500 lb airplane with the same performance.
Well, the LSA rules come from the MLA ones, as witnessed by the current market, virtually all of them are "converted" MLA's. Adding another 180 lbs wouldn't harm, but the though that heavier aircraft are somehow safer or stronger escapes me. I've heard far too often that the MLA's "can't possibly be safe" because they're so light. Most of the MLA's are certified in Germany (including most of the FAR 23 requirements) and have actually been tested far more thoroughly than what the LSA class requires. I'm also surprised by the frequent comments about the "too limited" payload. Several designs are around 600 lbs. 4 hours of cruise (120 lbs) leaves you with 480 lbs of payloads. Joking aside, even in the US almost all pilots fit in that weight limit don't they?
 

Vigilant1

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Adding another 180 lbs wouldn't harm, but the though that heavier aircraft are somehow safer or stronger escapes me. I've heard far too often that the MLA's "can't possibly be safe" because they're so light.
I think it would be hard to make the case that adding structure to a design in a well-engineered way won't make it stronger. If we wanted to >>remove< 100 lbs from one of these 600 lb empty weight airplanes, could we do it while maintaining the same strength, at the same price? Conversely, at least on the face of it, adding structure (weight) can allow the airframe to be stronger. Yes, diminishing returns and possibly some sacrifice in performance, etc, but having the ability to add weight (while meeting the requirement of the regs) allows designers the freedom to work out those tradeoffs.
 

WBNH

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That's good discussion of the LSA's as distorted by the current market and manufacturers building fast glass ships that happen to ft within the LSA envelope...but it omits the origination of the LSA class in the U.S....while similar to Euro Microlight rules, it was enacted to close the two place "ultralight trainer" loop holes and prevent the FAA from having to hire a thousand more personnel to enforce all the unregistered "fat ultralights"...

LSA is not supposed to be Pipestrel and Skycatcher...it's supposed to be Flightstar II, Challenger, CGS Hawk, Kitfox, etc. For the light recreational aviator there are a lot of options without having to expand the current envelope to bring in the Cessna 150's.

LSA does not allow electric motors for SLSA or ELSA...but you can use electric power in any EAB and fly it under sport pilot certificate if the gross and speeds are within LSA limits. A Joby motor on a Kolb would be nice to see.
 

autoreply

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I think it would be hard to make the case that adding structure to a design in a well-engineered way won't make it stronger. If we wanted to >>remove< 100 lbs from one of these 600 lb empty weight airplanes, could we do it while maintaining the same strength, at the same price? Conversely, at least on the face of it, adding structure (weight) can allow the airframe to be stronger. Yes, diminishing returns and possibly some sacrifice in performance, etc, but having the ability to add weight (while meeting the requirement of the regs) allows designers the freedom to work out those tradeoffs.
Building an aircraft stronger doesn't make it any safer, unless it ends up so heavy that it won't leave the ground of course :gig:

Rather the contrary, more weight means higher speeds, lower performance (with the same engine) and so on. No manufacturer will make an aircraft stronger than it needs to be (limited by regulations), as witnessed by virtually all the certified aircraft flying around, they will break, just above the ultimate load. Extra weight margin is used to raise the payload (by a stronger structure), add fancy displays, airco's, leather seats, massive tires, wing folding systems and lots of other things that might or might not be useful but have little to do with safer aircraft. I have yet to discover the first GA company outside of the sailplane industry and Diamond that did something more substantial on a safety cockpit than telling the marketing department to put in some fancy words about their "safe design"...
That's good discussion of the LSA's as distorted by the current market and manufacturers building fast glass ships that happen to ft within the LSA envelope...but it omits the origination of the LSA class in the U.S....while similar to Euro Microlight rules, it was enacted to close the two place "ultralight trainer" loop holes and prevent the FAA from having to hire a thousand more personnel to enforce all the unregistered "fat ultralights"...

LSA is not supposed to be Pipestrel and Skycatcher...it's supposed to be Flightstar II, Challenger, CGS Hawk, Kitfox, etc. For the light recreational aviator there are a lot of options without having to expand the current envelope to bring in the Cessna 150's.
It doesn't say that in the regulations and it's not meant to be that either. When the LSA requirements were finalized, most of the nowadays well-selling LSA's were already flying around, certified under MLA and it doesn't take a genius to predict that if those are the only aircraft that fall within your future regulation they will probably also form a major part of the sales, together with what was flying under similar regulations in Australia and New Zealand...
 

fadec

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I wonder if designing aircraft which push the limits of the LSA category could actually be detrimental to the category in the long term. It may encourage the FAA to put further restictions on the category in an effort to exclude designs which it considers not in keeping with the original intention of the category. I am not that familiar with US rules but I get the impression that the FAA has not clearly defined its intentions for the category (at least not in public)

I suppose it could also go in the other direction and the FAA could widen the scope of the category.
 

Dana

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...it omits the origination of the LSA class in the U.S....while similar to Euro Microlight rules, it was enacted to close the two place "ultralight trainer" loop holes and prevent the FAA from having to hire a thousand more personnel to enforce all the unregistered "fat ultralights"...

LSA is not supposed to be Pipestrel and Skycatcher...it's supposed to be Flightstar II, Challenger, CGS Hawk, Kitfox, etc...
That was the origin of the rulemaking, and how it was sold, but somewhere along the way it got taken over by the makers of the aircraft that currently represent the bulk of the LSA market... the LSA certification is far simpler than the traditional certification path, but it's still too onerous for all but a tiny number of manufacturers. Even the former king of ultralights, Quicksilver, has no LSA certificated models.

LSA does not allow electric motors for SLSA or ELSA...
I don't think it specifically prohibits electric motors; it doesn't mention them at all. Presumably nobody at the FAA thought they would be practical (IMHO the jury is still out on that one).

-Dana

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Aircar

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I have some grudging sympathy for the writers of rules and have seen this 'bracket creep' effect take place in our original ultralight class that also came out of the impossibility to police the growing powered hang glider fleet -- as such a lot of these rules are written for ease of administration or offloading the onus in case of mishap . Agreeing that the need for some limit on weight is probably the easiest way to draw a line for regulators still leaves the setting of an abitrary 'speed limit' as a problem --do we have government added 'dragerons' to enforce it somehow if the designer 'screws up' and it goes faster ? And if it exceeds the sacred speed one up or with the adjustable propeller 'adjusted' appropriately ?

The 'lift enhancing devices' clause is now clearer (it is not a ban like in standard class gliders for example) but in some weather it would be preferable to have an aircraft with higher wing loading and stall speed as a safety matter --negative flaps also 'de stress' the wing in rough air effectively .

I find the prohibition on twin engines less agreeable particularly as this general sort of aircraft will usually be able to stay airborne on half the power needed to fly at 2.5 times stall speed -- and the unreliability of engines is probably one of the primary sources of failure . Twin engine designs like the Lazair and Cri Cri would seem to be ruled out categorically despite being benign by design ( surely the usual clause "unless a compensating feature can be shown to provide an equal or better level of safety" could be inserted to maintain the spirit of the law --unless it is but buried in the unabridged version of the rules ) Push pull centreline twins do have the issue of KNOWING that an engine has failed if it is the rear one but Rutan has shown that even that is no problem with the Defiant and even fixed pitch props and would be easier to arrange with a higher span -- the Starship configuration is another way to get a minimum assymetry with power loss on one side that would be 'ruled' out . Besides the safety issues there are other considerations for MULTI engine layouts using smaller and cheaper engines or electric motors -- the odds of losing a given fraction of power are less with more motors provided the thrust moments are low (didn't the electric CriCri have four electric motors -two in each pod with push pull props ? )

I am against any sort of arbitrary restrictions in general and my interest is in getting past the 'critical mass' threshold for mass use of flying vehicles --as you all know .. in that respect the LSA rules are cited as being responsible for the Terrafugia roadable and several others in the pipeline --how the rules influence the real world safety of these aircraft will impact on the future of that whole class of aircraft as well.

I would like to see the elimination of the "No Fly zone' that presently exists where just about everybody lives and goes about their daily affairs --suburbia and the places where cars are accepted to operate on an 'acceptable risk' basis . (but were once just as restricted or even banned for similar unfounded fears --the "red flag act ' or " locomotives on highways act of 1861 " in england that was only lifted in 1896 --after an MP defied the law by driving a horseless carriage into the grounds of Parliament --shock horror, WITHOUT a man in front waving a red flag . Today it seems quaint or almost incredible that such groundless restrictions were enforced but they indeed were for 35 years . I would suggest that the restrictions on use of the airspace around towns and cities is just as unfounded given the current level of electronic aids,reliability of power and the possibility to create sufficient landing and take off places without any hazard or ill effects to those nearby . LSA could function as a means to further the goal of real everyday flying machines being as close as your own driveway and only a fw hundred yards to come and go by air (that the LSA rules have prompted the first roadable vehicle for a long time is perhaps significant . Finding a 'thin end of the wedge' was essential to get motor cars on to the roads and the same thing could be found in new rules like LSA for flying cars if they were flexible enough for failsafe power etc -just my take on it anyway.
 
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