Sport Pilot Talk

Professor thank you for the physics lesson. Did I ever tell you it gave me headaches in high school? And please no chemistry! LOL Nice analysis thank you.

I understand the taxi issue. I never flew that SportStar at Brookhaven. I used to fly with Art at Queen City.

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Marcus - WA2DCI
PP ASEL IA

Daidalos Greek: Δαίδαλος
Remember don't fly too close to the Sun.

You may not understand the history. The LSA standards were designed to regulate the previously unlicensed FAT Utralights. Unlicensed Ultralights kept getting bigger and faster.

Once they came out with the rules very enterprising people here and abroad started designing aircraft to fit those rules. There were a number of legacy Part23 aircraft that fit the rules. The LSA industry as we know it today was an unintended conseguence of this rulemaking.

Check out http://www.barnstormers.com/ and search the Light-Sport category. You will see many of those FAT utralights with n-numbers for sale. Look for plane like CGS Hawk, Challenger, Kolb and Flightstar.

That is what the rules were supposed to capture.

See http://ssax8b.hubpages.com/hub/There-no ... ts-Anymore
http://www.all-about-ultralights.com/faq.htm#3.

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Marcus - WA2DCI
PP ASEL IA

Daidalos Greek: Δαίδαλος
Remember don't fly too close to the Sun.

Great discussion and example Professor. Thank you!
The Bonanza is about 2.5 times heavier than the SportStar.
So if hypothetically LSA's were allowed another 300# gross weight would the kenetic energy increase be that significant?

(Hope I don't make you sharpen ALL of your pencils!)

Excellent link above Marcus.
http://ssax8b.hubpages.com/hub/There-no ... ts-Anymore

I was familiar with the concept of the ultralight being the reason for the LSA regulation, but never read the whole history behind it.

So... if we were to continue on with the story... basically all of us flying LSA airplanes are basically flying a legal derivative of an enclosed 2-seat ultralight in the FAA's eyes!!

Bingo... you got it. It also had another unitnended consequence. Besides bringing these previously non-licensed pilots in to the fold so to speak. There were many older pilots like myself, who for one reason or another did not want to jump through the hoops to get an expensice SI medical.

These pilots were used to certificated airplanes and instruments. The non-certified avionics choices also exploded.

At a recent pilot club meeting some pilots with medicals kept telling me how they wanted to checkout in an LSA because they wanted to experience a "glass panel". I was telling them how I miss steam gauges.

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Marcus - WA2DCI
PP ASEL IA

Daidalos Greek: Δαίδαλος
Remember don't fly too close to the Sun.

300 lbs is about 23% of 1320. So, if gross weight could be increased another 300#, without changing stall speed, then KE would also go up about 23%.



The above calculation was done in my head, without any pencils at all. (Deciding whether 23% is significant, or insignificant, is another matter -- it will require lots of pencils...)

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The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven
http://AvSport.org fly@AvSport.org

Hi Paul, you wrote:

"There's a safety reason for keeping the max gross weight low. Kinetic energy (which must be dissipated in the event of an accident) varies directly with mass, and with the square of velocity. Keeping the plane both light and slow significantly limits kinetic energy, which minimizes the likelihood of injury in the event of an accident. Increasing gross (even if stall speed remains constant) will inevitably increase the fatality rate."

You are correct about the relationship between mass, speed and kinetic energy, but I don't think it applies to passengers. Your logic is correct if the airplane hits you, but not if you are in it. If true, then heavier cars would kill occupants more often than lighter cars, all other factors being equal. In fact, generally, the opposite is true.

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FredG
Iowa City

I'm like that in that I don't want to jumbo through a medical.
The big issue for me is not steam gauge vs. gass panel.
(Although so many really exiting things are happening with glass panel.)

I just want an EXCITING aircraft that feels like a sports car, not a mini van!
So LSA is more condusive to modern exciting aircraft (without having to shell out hundreds of thousands of dollars.)

Yet I could be very happy in an Exta aerobatic plane (mostly steam guages)... which is where I might be headed someday... Of course, then I will have to deal with the medical jumbo as well!

The difference is that cars have many heavy weight devices in place to protect occupants, where aircraft is all lightweight with very litte structural protection. If there is kenetic energy going on in an airplace crash there is very little to protect the occupants from such forces.

Designrs - unless there is a mechanism to transfer the kinetic energy of the airplane to the occupant, then it isn't a factor( certainly not the dominant factor).

If two airplanes were to hit something on the ground or in the air, then the damage done to the thing hit is proportional to the mass and square of the velocity. In such a case, the kinetic energy is transferred. But, from the perspective of the occupant, its rapid deceleration, blunt trauma, fire, and other factors that cause injury. There are related to the kinetic energy of the airplane to the extent that the occupant is moving at the same speed as the airplane.

Thanks!

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FredG
Iowa City

I would think the mechanism of transfer would be physical contact between the airframe and the occupants. Automobiles typically have crush zones to absorb a significant portion of the kinetic energy in a collision. Aircraft, unfortunately, do not. If an airframe collapses around its occupants, there will be blunt force trauma, so indeed G loads will be the least of your problems.

That said, lower mass is better, from the standpoint of the occupants (as is lower landing speed). These are the chief reasons why, though the accident rate in LSAs is still disappointingly high, the injury and fatality rates are significantly lower than they are for GA as a whole.

_________________
The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven
http://AvSport.org fly@AvSport.org

Paul, we agree that as speed increases, hazard to occupants increases.

But, again, the kinetic energy of the vehicle (airplane, car, etc) is not the issue. If it were, then a 15 MPH train crash should kill all of the train occupants (given the enormous kinetic energy of a train) and a 15 MPH bike accident should result in no harm to the rider. This is contrary to empirical reality. Factors other than the kinetic energy of the vehicle are what causes harm.

Thanks!

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FredG
Iowa City

Absolutely true, Fred. One of those factors is the nature of the object with which the vehicle collides. If one assumes an immovable, inelastic barrier (which the Earth certainly behaves like, when an airplane collides with it), then all of the kinetic energy ends up transferred to the occupants. So, if a train hits a truly immovable and inelastic object, there will indeed be major loss of life, even at slow velocity.

That's a worst case assumption, to be sure -- but often (sadly) is the case with airplane accidents.

That said, I will certainly stipulate that velocity dominates the KE equation, with mass playing a somewhat less significant role, since KE varies with the square of velocity, but with mass only to the first power.

_________________
The opinions expressed in this post are those of one CFI, and do not necessarily represent the position of the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS
AvSport of Lock Haven
http://AvSport.org fly@AvSport.org