Flight Design "Safety Box" & possible LSA Implications

[CTLSi]

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[MrMorden]

I don't keep all the accident pics...but Google does.

[snaproll]

I saw the pictures of the second fatal of Remos, and it didn't look pretty. The airplane came apart like any plastic airplane - engine in front, tail in the back, the pilot rolling on the runway in the middle. The separation of front and back occured at the trailing edge of the wings down. Obviously the restraint system does nothing in such case.

Previously, I saw that happen to Jabiru, when an old lady landed a J-230 on top a hangar at Front Range. When the plane came apart, she fell into the gap between hangars and died there because professional first responders took their sweet time, and nobody else could fetch her. Pretty much what I expected from Australian plastic, honestly.

If CT has the same joke of survival cell that Remos has, then you're better off in a Cub's steel tube cage. Fortunately, CT comes with a chute and you should not test its survival cell unless you're suicidal.

Pete,
Appreciate your comments and view, but … there are misconceptions about the crashworthiness of most designs. I leave it to the experts like Paul to categorize each structure for survival based on energy absorption, etc. I unfortunately grew up in this business and have witnessed dozens of accidents, played crash crew, peeled bodies out of wrecks, and removed aircraft debris after crashes. While steel tube does appear to be a “safety cage”, it often is too ridged to absorb enough impact energy to save the pilot/crew. I have peeled dead bodies from steel tube structures where the maximum “G” load for human survival was exceeded but the frame was repairable. There are no perfect designs or perfect airplanes, all are a compromise of sort to achieve aerodynamics, weight, and stability. Each owner should fly what they are comfortable with and enjoy what they do. Constructive criticism, comments, and opinions are a plus for forums as this, and your opinions and input contribute to understanding various designs and structures. VR.. Don

[IFlyRC]

Is there another thread that discussed the crash worthiness of different airframes? I've been looking over the crash reports, but it's hard to decipher the results. The Flight Design safety cell does seem to hold up well. Some of the other designs resulted in a crumpled mess. It's impossible to beat the laws of physics, but it would be interesting to hear the analysis of the various designs.

[Jack Tyler]

Interesting pics, Andy - thanks for sharing those. Obviously, you've been collecting... <s>

[CTLSi]

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[FastEddieB]

Unlike the older planes, especially the heavy, draggy metal ones, the ONLY alternative they have is to land, and do so with a much shorter glide distance.

The FD has a long glide due to its slippery and lightweight design...

That sounded like a bit of an unwarranted assumption, so I quickly found POH's for the CTLS and the C150.

Both publish glide range:





Sure seems to me that from 5,000', let's say, they both glide about the same distance (about 7 1/2 miles).

You have a marvelous plane, but do not automatically assume its better in every area over older, time tested designs.

And on a minor "Stick and Rudder" note:

The FD has a long glide due to its slippery and lightweight design...

Question: are you under the impression that a lightweight plane can glide farther than a "heavy" one?

[CTLSi]

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[drseti]

What are gliders made from? Carbon fiber. Why aren't they made from metal and rivets? You can guess the rest...

I am assuming you are not a glider pilot, and thus can be forgiven for guessing wrong. Glide capabilities are a function of lift to drag ratio (L/D). This has very little to do with weight. The reason gliders are kept light has more to do with the power required of the tow plane to launch them aloft. Once in flight, it turns out, heavy gliders soar a bit better than light ones! This is why competition-class sailplanes carry water ballast tanks in the wings -- so they can be loaded (with water) exactly to the specific total weight that will best meet the performance objectives of a given flight. (If lighter were really better, then those ballast tanks would always be empty.)

[CharlieTango]

What are gliders made from? Carbon fiber. Why aren't they made from metal and rivets? You can guess the rest...

I am assuming you are not a glider pilot, and thus can be forgiven for guessing wrong. Glide capabilities are a function of lift to drag ratio (L/D). This has very little to do with weight. The reason gliders are kept light has more to do with the power required of the tow plane to launch them aloft. Once in flight, it turns out, heavy gliders soar a bit better than light ones! This is why competition-class sailplanes carry water ballast tanks in the wings -- so they can be loaded (with water) exactly to the specific total weight that will best meet the performance objectives of a given flight. (If lighter were really better, then those ballast tanks would always be empty.)

I've flown in metal and rivets gliders. The company was originally called the Schweizer Metal Aircraft Company.

[FastEddieB]

What are gliders made from? Carbon fiber. Why aren't they made from metal and rivets? You can guess the rest...

Let me be so bold as to suggest a slightly different response:


"Wow! Thanks, Eddie! First, I had no idea that those older planes glided so well - in fact as well as mine!

And second, you're right - I WAS under the impression that light planes could glide farther, all things being equal. I researched it and, counterintuitive as it may seem, weight is actually NOT a factor in how far a plane can glide. Weird but true!

Anyway, thanks for pointing out not one, but two errors in my post. I'm here to learn and really appreciate it.

Thanks again!"



Just a thought!

[FastEddieB]

I just found out about an accident involving a Cirrus in Colorado:

http://www.9news.com/story/news/local/2 ... /14820813/

The "Safety Box" design of the Cirrus certainly helped avoid fatalities.

[zaitcev]

I think that the reason gliders went to carbon heavily nowadays is because they want high aspect ratio wings with somewhat thin airfoils. Older ragwing gliders, such as 2-33, used a thick wing into which I could stick my head. That wing actually had a ton of aluminum in it, and its thickness permitted a tall spar.

Competition gliders carry up to 500 lbs water ballast to make them heavier in speed contests. Heavier glider glides at exactly same angle as lighter one, but it does it a higher speed, therefore it wins contests.

The newest and hot homebuilt kit HP-24 is designed for 200 lbs water because they're trying to make it cheap and compact. Otherwise they'd put more in it.

The good old 150 is a great airplane. Unfortunately it's aluminum and thus darn heavy for modern lardbutt pilots. I simply cannot take my wife with modest baggage on a trip in a 150, but in a CT I can. Even with a chute! And that is despite the gross weight of 150 being 1/4 greater - the payload still sucks. That is the dramatic advantage of CT's composite construction, and not its aerodynamic performance.

[drseti]

That is the dramatic advantage of CT's composite construction, and not its aerodynamic performance.

Very true, Pete. The usual reason for going to composites is sleek compound curves, allowing significant drag reduction, hence high cruise speeds. Since speed is limited for an LSA, we cannot enjoy this particular advantage of composites. However, composites are definitely lighter than metal structures of similar strength, so plastic LSAs end up with higher useful loads than metal ones (at essentially the same speeds and glide performance).

[howardnmn]

"I saw the pictures of the second Remos fatal accident, and it didn't look pretty" very insightful comment. Have you ever seen a pretty fatal accident?

I bought a Remos because it was the safest LSA I could buy

It also has a Kevlar safety cage. I don't know if it's as good as a CT but I expect they're pretty similar, given both German carbon fiber of similar age and direct competitors.

The fuel system on my Remos is the best. After "vfr into IMC" the second leading cause of accidents are fuel system related. The Remos has a lockable grounded fuel filler that doesn't involve the risk of fueling on a ladder. It's a high wing a/c with filler at shoulder height. The site tube is readable in turbulence and in uncoordinated flight. The dynon skyview fuel totalizer appears to be accurate to within 1/10th of a gallon. If the wings shear off in a crash no fuel spills from wing root. The tank is designed to be ethanol resistant. Only One sump during preflight.

My Remos is super light. The weigh scales indicated 740 lbs after assembled from shipping container. That's with dual skyviews, a garmin 696, and a chute. Extra weight is a killer. Momentum is a function of weight x velocity squared. Weight plays a role in Fatal Base to final turns. How about heavier LSAs taking off at ten thousand foot density altitudes? I've done it with wife , weekend baggage and full fuel from truckee. A bit of pucker factor but definitely can't imagine lifting an extra 100 lbs of aircraft.

My Remos has the best build quality I've ever seen on an LSA. Built better means safer. If you see one on the flight line checkout the flap hinges and compare to other aircraft. Look inside at the firewall penetrations. It's like something you would see in aerospace installs. Compare the Remos voltage regulator to std Ducati.

The seats are as comfortable as they come. Ventilation and heating is great. There's a cockpit controllable flap on the oil cooler for faster warm ups. My skyview system has adsb in and out. I get traffic and weather. BTW I don't have to ask Remos GmbH for approval to periodically upgrade the dynon operating system.

The battery has a fuse on the starter cable. In a crash an unfused starter cable that shorts is instant ignition source.

My Remos is super easy to land. I'm a crappy pilot and my first three landings were greasers. I've been distracted and come in high and hot and still managed a decent landing on my 2100x 34 strip. Forward visibility is fantastic. Sounds crazy but I feel that turbulence penetration is as good as it gets in a light aircraft. As good as my old twin cessna 310. Controls are harmonized. Big tail feather make extreme cross winds manageable. Easy to fly and easy to land means safer.

My experience with Technical support has been wonderful. When I needed it I got an LOA overnight from Remos GmbH. (Christian Majunke has always responded to my questions within48 hours.) Most parts are replaced on condition. No five year hose replacement (which in itself poses risks). I keep a spare fuel pump that would have to be replaced in other LSAs after five years. The comprehensive maintenance manual is available on line and seem to be updated with my latest features

It's a high performance premium priced LSA but I feel it's very good value. I felt I owed to my family to buy -- irrespective of cost -- the safest LSA I could.

Someday my two young daughters may understand why daddy spent so much money on his new toy.