Sport Pilot Talk

Jack Tyler · Posted: Fri Jul 01, 2011 5:44 am Post subject: Why are LSA's limited to 1320#?

I thought this historical review (Flying, 4/2011) might be of interest to some Sport Pilots who will always be balancing the weight limits of LSA's against their cross country flight plans:

"WEIGHT MATTERS. EVEN in the light-sport aircraft world. As I wrote in last month’s column about the LSA categories, the maximum gross weight is one of the key factors in determining whether or not an aircraft meets the FAA’s LSA definition. How did the FAA come to that final 1,320-pound figure? Well, it wasn’t a direct route — or without considerable thought, to be sure.

First, some back story. The Sport Pilot/LSA rule — the result of a 10-year effort largely spearheaded by the EAA — grew out of Part 103, which governs single-seat ultralights. Though the vehicles allowed under Part 103 are loosely regulated, they don’t require a person to obtain a pilot certificate or have aeronautical knowledge to fly them. So when the United States Ultralight Association petitioned the FAA to amend Part 103 to allow two-seat and “fat” (overweight) single-seat ultralights, the FAA took it a step further. Instead of amending Part 103, it proposed the Sport Pilot/LSA rule, which would bring ultralights into the fold of pilot certification by way of the Sport Pilot license. But that wasn’t the only motivation for the rule. With pilot numbers on the decline, it was hoped that the rule would also grow new pilots by offering a certificate that would cost less to obtain and maintain than a private certificate. And that it would spur manufacture of new, affordable airplanes.

As the proposed Sport Pilot rule moved through the system, the Aviation Rulemaking Advisory Committee (comprised of representatives from the ultralight and light experimental communities) first looked to the European mircolight regulations for two-seat ultralight max gross weight, which was 992 pounds (or 450 kilograms).

“It was realized that number would make it difficult to design newly manufactured LSA,” says Joe Norris, EAA’s homebuilders community manager.

After more consideration by the ARAC, the number submitted in the final notice of proposed rule making was 1,232 pounds — or 560 kilograms, the gross weight limit used by Australian microlights and Canadian advanced ultralights. Now, it was thought, a broader range of vehicles could qualify. What more could be asked? Well, about 100 more pounds, apparently.

As the NPRM went through the comment process, an argument developed for additional weight. Among the reasons cited were that more weight would allow for currently produced type-certificated four-stroke engines and ballistic parachute recovery systems. Ultimately, the FAA acknowledged that the added weight might be a safety benefit to light-sport aircraft design. It was determined that a max gross weight of 1,320 pounds would suffice. By chance, this figure qualified certain standard-category aircraft that met that weight, like a Cub or Champ, for Sport Pilot certification. As you can imagine, this spurred more discussion, including why Cessna 150s, one of the most prolific trainers, couldn’t be included.

“In the FAA’s mind, allowing certain standard-category airplanes that met the LSA definition to be operated by sport pilots was a bonus,” says Norris. “The 150, seemingly a fit in most ways for the rule, didn’t meet the weight requirements.”

In the end, “deciding the final max gross weight was only part of a well-considered rule that allowed people to bring their nonpedigreed airplanes into the system and made room for new airplanes,” says Tom Peghiny, ARAC member and president of Flight Design.

And that’s why 1,320."

The author is Connie Sue White and the link is http://www.flyingmag.com/aircraft/lsasport/sport-pilot-why-1320

drseti · Joined: 28 Nov 2009 Posts: 1390 Location: Lock Haven PA

And, it doesn't hurt that 1320 pounds equates to exactly 600 kg. Gotta love those nice round numbers...

Jon V · Joined: 21 Apr 2011 Posts: 156 Location: Dallas...

Yeah, I think the real answer is probably:

"500kg was too little, 1000kg was too much."

Kinda like the Vh >/< 100MPH (87kt) rule. 100MPH is just an arbitrary round number, not some point where the physics of flight change or you run afoul of other regulatory impositions.

dstclair · Joined: 06 Mar 2008 Posts: 212 Location: Allen, TX

Actually, 600kg is just short of 1323 lbs. We got ripped off by 3lbs :D

drseti · Joined: 28 Nov 2009 Posts: 1390 Location: Lock Haven PA

Does that mean I can fly my plane 2.77 pounds over gross? (But only in Europe, of course...)

dstclair · Joined: 06 Mar 2008 Posts: 212 Location: Allen, TX

...or Australia :)

drseti · Joined: 28 Nov 2009 Posts: 1390 Location: Lock Haven PA

dstclair wrote: ...or Australia :)

Oh, that's right. In Oz, they have kilograms because (unlike the UK) they don't have pounds!

seaplane_tux · Posted: Sat Jul 02, 2011 12:32 am Post subject: Why are LSA's limited to 1320#?

So,.... explain again...

How does 1320lbs/600KG make a plane safer and easier to fly :?:

:?

I don't think the FAA believes in "Safety" just power trips and kick backs :twisted:

Jon V · Joined: 21 Apr 2011 Posts: 156 Location: Dallas...

seaplane_tux wrote: So,.... explain again...

How does 1320lbs/600KG make a plane safer...

mv^2 / 2

(safer compared to 1000kg/to those outside the plane)

Jack Tyler · Posted: Sat Jul 02, 2011 4:59 am Post subject:

"How does 1320lbs/600KG make a plane safer and easier to fly?"

As I read it, the article is making two key points:
-- historically, slower & lighter aircraft had fewer rules because they represented less risk to pilots, no risk to passengers (since none could be carried), and less risk to the population at large because of the a/c's limited range, speed & weight. (I don't see any connection with 'easier to fly' and I find weight-shift a/c less intuitive to fly). Obviously, as a new class of a/c was considered that would require fewer-than-PPL rules, a new line had to be drawn between risk on the one hand and a/c capability on the other. And while 1320# - specifically - might be arbitrary, the desire to make this a practical option for pilots (and a/c buyers/owners), meant any weight limit had to consider the existing marketplace - e.g. the engines.then available.
-- Less arbitrary was the decision to align the USA weight limit with European standards, as that immediately guaranteed international trade and made a fleet of existing a/c available for purchase and use in the USA. (BTW the Australian limit is generally less than 600Kg).

It would be easy to quibble about each of the LSA restrictions as they were finalized, but it is like arguing about how long is a piece of string.

drseti · Joined: 28 Nov 2009 Posts: 1390 Location: Lock Haven PA

Jon V wrote: mv^2 / 2

For those not conversant with the physics: Jon is citing the kinetic energy equation. Translating, kinetic energy varies directly with mass, and directly with the square of velocity. So, reduce mass and you have less energy to dissipate in a landing (or accident). Reduce velocity, and you have a whole lot less kinetic energy to dissipate. Thus, low weight and low stall speed translate to safer aircraft (or so the theory goes).

As for the arbitrary nature of numbers, perhaps someone cares to explain why Part 103 ultralights were limited to 254 pounds empty? I sure can't come up with a good reason for that number. But, they had to draw the line somewhere.

seaplane_tux · Posted: Sat Jul 02, 2011 10:20 am Post subject: Why are LSA's limited to 1320#?

My point about any weight limit at all is...

The FAA uses the word "Safety" in every article they write but, when it comes down to what is safe they don't seem to have any idea.

The engineers built a very durable long lasting trainer in the Cessna 150 and 152. These planes have proven very reliable over the years with rugged landing gear. A training aircraft with a 500 lbs. useful load needs extra tough landing gear. My opinion, is that the 1320 limit subtracts from the durability and safety of the aircraft.

Jon V · Joined: 21 Apr 2011 Posts: 156 Location: Dallas...

Code: why Part 103 ultralights were limited to 254 pounds empty

Well you see you start with 100 because it's a nice round number.

Then you convert it from nautical miles to statute miles: ~115.077945
Then you convert that from kilograms to pounds: ~253.70343
Round it off: 254.

Obvious.

Jack Tyler · Posted: Sun Jul 03, 2011 4:58 am Post subject:

"A training aircraft with a 500 lbs. useful load needs extra tough landing gear. My opinion, is that the 1320 limit subtracts from the durability and safety of the aircraft."

Klaus, you can of course think this if you wish. But a landing gear's design - the structure itself, materials used, mounting location & method, etc. - of an a/c, LSA or other, would not seem to be dictated to any specific degree by its max weight limit any more than any Part 23 a/c design faces tradeoffs in weight, strength, useful load, speed, etc. OTOH if your view is that there are LSA a/c being produced with landing gear insufficiently robust for student training, which may well be the case, then that is a function of the design and build choices made by those mfgrs. It's not apparent to me how this relates to the 1320# weight restriction itself, because some LSA a/c do have robust landing gear.

Aerco · Joined: 26 Aug 2009 Posts: 68 Location: Corona CA

Jon V wrote: Code: why Part 103 ultralights were limited to 254 pounds empty

Well you see you start with 100 because it's a nice round number.

Then you convert it from nautical miles to statute miles: ~115.077945
Then you convert that from kilograms to pounds: ~253.70343
Round it off: 254.

Obvious.

Or, as another story goes: an FAA guy looking into the issue of Part 103 saw a Quicksilver-type of early ultralight and asked how much t weighed. "254 lbs" was the response. FAA guy writes this down and goes back to the office.....