Basic Configuration for a "Safe" airplane

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Dan Thomas

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Well, how much do airbags weigh? Seems like the shoulder harness airbag solution in cars really cut down on serious injury/fatalities in cars. What's wrong with wider adoption of chutes for planes? What's the fatality rate for planes with chutes? If a crumple zone up front would help, how much would some extra sheet aluminum and longer longerons weigh? Seems like this is a solvable problem that is being held up by the regs on how you certify aircraft.
It reminds me of sailboat designs from the 80's, versus the way they became shaped in the 90's. Big change from narrow sterns and longish overhangs, to wider sterns with chines and plumb bows. The wider sterns and plumb bows added interior volume and initial stability, but had an impact on handling in following seas and other metrics. The buyers liked the new changes, but the old boy network hated the change from "traditional, time tested design". Sometimes we're our own worst enemies.
Well, how much do airbags weigh? Seems like the shoulder harness airbag solution in cars really cut down on serious injury/fatalities in cars. What's wrong with wider adoption of chutes for planes? What's the fatality rate for planes with chutes? If a crumple zone up front would help, how much would some extra sheet aluminum and longer longerons weigh? Seems like this is a solvable problem that is being held up by the regs on how you certify aircraft.
It reminds me of sailboat designs from the 80's, versus the way they became shaped in the 90's. Big change from narrow sterns and longish overhangs, to wider sterns with chines and plumb bows. The wider sterns and plumb bows added interior volume and initial stability, but had an impact on handling in following seas and other metrics. The buyers liked the new changes, but the old boy network hated the change from "traditional, time tested design". Sometimes we're our own worst enemies.
Amsafe makes airbag seat belts/shoulder harnesses for airplanes. They show up in newer Cessnas, for instance. They're fired by a deceleration sensor and trigger the release of compressed air into the bags from a tiny canister that has more than 6000 psi in it.

BRS makes 'chute systems for popular light airplanes. The one for the 172 weighs around 70+ pounds and takes up nearly half of the baggage compartment. You need at least 800 feet of altitude to have a chance of survival with it. Since a lot of accidents involve loss of control on takeoff or landing, there's a bunch of times when it's useless.

Both of these systems are expensive and have periodic overhaul requirements, which are also expensive.

I have worked on both systems, too.
 

Bigshu

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Both of these systems are expensive and have periodic overhaul requirements, which are also expensive.
Why? I get that airbags aren't cheap, but are they more expensive than they are for cars? Expensive or not, when the government got serious about improving crash worthiness, airbags were mandated. And car makers passed the cost on to consumers. But guess what? Cars are still vastly less expensive than aircraft that don't have airbags. Does your car's airbag require periodic overhaul? I've owned a lot of cars with airbags (my current car has 5!), and that would be news to me. I suspect that requirement is just more of the FAA over reach that is killing GA.
 

cluttonfred

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In all seriousness, I have thought about car-type pedals, but the nature of flying is more "set it and forget it" in terms of the power settings most of the time so a foot throttle is not really needed. If you have a steerable nosewheel with a decent turning radius, you could get away without differential brakes and just use a brake pedal on the floor. Still, I really like the idea of having no controls at all on the floor and being able to throw a bag or cooler down by your feet with no concerns. Installing dual brake circuits and a free-swiveling nosewheel does seem to be the simpler solution for ground handling.

The question I ask myself about my own suggestion is whether or not I could live without pitch control and with engine rpm and climb/cruise/descent state essentially locked together. You'd still need pitch trim but really just enough to dial in level flight at cruise rpm for a given weight and density altitude. After that it's full throttle to go up and throttle back to descend without touching the trim. You might not, for example, be able to trim to maximize your time aloft at low speed and low power settings without such a wide trim range that punching the throttle to full or dropping it back to idle without changing the trim might cause a stall or dive.

I'm exactly with you on these opinions. I agree that keeping the pilot task saturation low can lead to better situational awareness/pilot control. I think a little more coordination of controls in the design phase makes for a popular aircraft (thinking of the Ercoupe here). I'd be very interested in a modernized Ercoupe, with or without rudder pedals, designed for modern size occupants, with a single throttle control set up as you describe, with a flap/spoiler/ speedbreak interconnect. I think that would be a pretty safe, not neccessarily "sporty" airplane. If you didn't have rudder pedals, you could make the throttle a foot pedal on the right, and the spoiler/speedbrake a pedal on the left. How much easier to train a car driver with a system like that? NOW we'll see the flames!
 

cluttonfred

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I suppose with a decent power to weight ratio it need not be though I am not sure how you would make anything resembling a tight turn. If you add pitch control then it's just like flying an Ercoupe, but you'd still have to limit pitch authority to prevent stalls.

For me, such a control system would mean very boring flying.
 

Pops

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Lots of myths about the Ercoupe by people that don't know much about them. First- they can be stalled, just not from level flight. I have owned 2 Ercoupes, one with rudder pedals and one without. Never did get the one with rudder pedals to spin. Stall and slap in full rudder and it would just come down in a spiral. They are trickier to fly than a C-150 because you can't lower a wing in a crosswind while landing. Since they don't have flaps the flight manual says slow down to rock the wings right and left for a steeper decent. Third- With or without rudder pedals, the nose wheel is connected to the ailerons. Ercoupes has a higher rate of accidents of running off the end of the runway for a reason. Ercoupes have a crosswind component of 25 mph. That is higher than most airplanes. When landing in a crosswind the manual says land in a crab ( LG designed for the side load) but just as the main wheel touch down, lightly let the control wheel turn by itself when the nose gear contacts the ground the nose will serve and un-crap and line up with the ground track. That is when the trouble starts, this causes the upwind wing to increase in airspeed and the downwind wing to slow down in airspeed. this causes the upwind wing to lift and allows the crosswind to get under the wing that has a lot of dihedral and will lift the wing and main wheel on that side to come off the ground until you are rolling along on the other main wheel and the nose wheel. The airplane then will serve off in the downwind direction while running on the two wheels.
You can't stop from going off the side of the runway by turning the control wheel , if you do , you make things worse. The only thing that will help is adding power. The wing will come down and when the wheel is back on the ground and get on the brakes as much as possible to cut our airspeed. Good luck on that, the old Goodyear brakes with a 1" dia puck is about like dragging your feet. A set of Clevelands is a highly welcomed. By adding power you just increased you landing rollout and with poor brakes . Running off the end of the runway is a common thing.


Added-- One time I was landing on a 7K long runway and with rudder pedals, you just have the handbrake. Tower said to turn off the first taxi way to the right. Pulled the handbrake and there was no braking. Passed the taxiway about 35-40 mph and tower said "Just turnoff anywhere you can". The runway was slightly down hill and I rolled about 5K before turning off. Got it on the ramp. ( before a dumb Engish reporter used the term tarmac in 1974 instead of RAMP. Yes, I know about the macadam pads used to park the B-17's on in WW-2). If the brake puck wears down more that about 1/8" the master cylinder is so small in volume of brake fluid, you have no brakes. So since the puck is 1" in dia, ( same as a quarter coin) , I put a quarter behind each brake puck and had brakes again and refueled and when on my way.
 
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RogFlyer

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If and when one does get into trouble, some design features that assist survivability. An intrusion resistant safety cage and roll bar, ergonomic seating position, supportive seat, restraint system (best is a 5 point harness and lightweight helmet - no need for airbags), crumple zones to reduce safety cage decelerations. For a light plane, this would at least be a forward crumple zone and a base crumple zone.
 

Bigshu

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For me, such a control system would mean very boring flying.


BJC
Yes, but the topic is safer aircraft. The safest cars are pretty boring too. I think the aileron/rudder coupled approach with limited travel on the elevator, like an Ercoupe, could still be fun to fly ('coupe owners are pretty devoted), but safer as well. We just need a bigger Ercoupe. Maybe like the Tomahawk/Skipper, with a better airfoil?
 

TFF

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If you do not have normal flight confidence flying, you should be a passenger. You can be over confident and be stupid, or you can be under and indecisive. Those are the extremes. Most are in the middle. Some circumstances are out there and that is just life. If somehow you got into an inverted spin in a 172, well you are making history because nobody else could; enjoy the glory until you hit the ground.

I think anyone who who is not a pilot says, I’m not going to fly if all I can fly is a 172, shouldn’t fly.(Enter you personal aloof training aircraft) They are wanting to fly for the wrong reasons. Everybody wants as cool as they can afford times two. Not everyone gets to. Some get to move on and some don’t, but if you can’t do a decent job flying a 172 around, shouldn’t be allowed to.

Why? Because they are confusing concentration on flying, as hard. Flying flying is concentrating on flying the whole time. Landing a 172 requires the same brain work as landing a 747. There is lots of extra practice to land a big jet, but you do it the same way. I landed in a full motion sims a CRJ200 and an Airbus 300 first tries. Good enough to be a captain no, but it’s only training and opportunity between a 172 and an F4. Yes there are people who wash out, and I’m sorry. Those are an extreme end. Most of it is wrote.

Fly a helicopter and the concentration is times two. You don’t get to look out the window and go, what a pretty flower. It’s like racing a car. The drivers want to be lost in concentration. Not going fast. They might need to go faster to be lost in it as they gain experience, same with airplanes. If you can add bandwidth while flying a 172, it’s time for a Mooney or a Citabria. That’s from practice and experience.

Flying is not sightseeing. Sightseeing is for passengers. I’m not saying you don’t get to look out the window and enjoy, but you only get to with practice and experience expanding the bandwidth. For many, they painted themselves into a box because they will never get the experience without life in a 172.

Safer airplanes is mostly pilots not forgetting to be pilots first. If you plane sheds it’s wings, or someone poured oatmeal in to your gas tank, and you want to walk away from the crash, that is improving the airplane.
 

Bigshu

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If and when one does get into trouble, some design features that assist survivability. An intrusion resistant safety cage and roll bar, ergonomic seating position, supportive seat, restraint system (best is a 5 point harness and lightweight helmet - no need for airbags), crumple zones to reduce safety cage decelerations. For a light plane, this would at least be a forward crumple zone and a base crumple zone.
I was thinking combining safer with enticing more people into flying. That being my goal, 5 point harnesses and helmets are not on the menu. I do think crumple zones front and below the safety cage would go a long way toward helping prevent injuries for those who are philosophically opposed to airframe chutes. There have been a lot of articles about how to replace stock seat stuffing with different layers of various density foam to improve support/crash safety.
 

Bigshu

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I think anyone who who is not a pilot says, I’m not going to fly if all I can fly is a 172, shouldn’t fly.(Enter you personal aloof training aircraft) They are wanting to fly for the wrong reasons. Everybody wants as cool as they can afford times two.
I try not to complain about what I fly in, but I've been around airplanes my whole life, and I'm in geezer territory now. I do see that people new to flying don't want to fly in old, beater airplanes. I think you can have cool, modern trainers that incorporate modern design and safety features. As to the thrill seeking mentality, a good CFI will discourage that pretty quickly, or at least force the student to behave like a prudent pilot until they get on their own. If they haven't learned there are no old, bold pilots by then, they're always going to be a hazard to others, and potentially damaging to the sport.
 

Protech Racing

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It's not a popular point of view, but I do believe that the aircraft with the least amount of demands on the pilot is, in fact, the safest. A plane with only two controls (up/down and left/right) could, in fact, be very safe if set up correctly:
  1. A single throttle lever which, when pulled back below the idle setting deploys spoilers/air brakes/landing flaps for adjusting glide path even with the engine off.
  2. A wheel/yoke/stick for turning left and right using rudder only, ailerons only, or interconnected rudder ailerons, no pitch control.
  3. Rugged tricycle gear steerable from the same wheel or yoke, or differential hand or foot brakes.
It wouldn't be very maneuverable or terribly exciting but it would also not be subject to pilot error causing a loss of control in the usual stall/spin scenario. You'd need to test passive stall/spin recovery in the case of violent turbulence. I imagine a nice modern cockpit like a Tesla with dual yokes and a large central lever like an inverted U for throttle/air brakes.

OK, I've got my fireproof Underoos on, flame away!
Thats my tandem wing exactly , minus the flaps . ;;
 

edwisch

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The two main killers in plane crashes are blunt trauma from the structure collapsing while not providing sufficient energy absorption and the post-crash fire.
I'd like to hear some discussion on this.
Jim
Hmm. Do you have any statistics on post-crash fire? I've not seen any to support your position.
 

Dan Thomas

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Why? I get that airbags aren't cheap, but are they more expensive than they are for cars? Expensive or not, when the government got serious about improving crash worthiness, airbags were mandated. And car makers passed the cost on to consumers. But guess what? Cars are still vastly less expensive than aircraft that don't have airbags. Does your car's airbag require periodic overhaul? I've owned a lot of cars with airbags (my current car has 5!), and that would be news to me. I suspect that requirement is just more of the FAA over reach that is killing GA.
Car airbags are inflated by an explosive charge. Like gunpowder. Airplane airbags, because they're strapped to your body, are inflated by compressed air that can leak away over time and is stored in a canister than can corrode and explode under your seat and send shrapnel everywhere The sensor is under the floor where, if you've ever been under the floor of an airplane, you know that there is a vast number of threats that can disable or unexpectedly trigger the system. Dirt, oil, mice, water, corrosion, chafing wires and cables, and so on. And airplanes sit 99.9% of the time, letting all this stuff happen with no interference.

Cars are NOT airplanes. I don't know how many times I've had to say that. The failure of a car airbag is a lot less serious in a 40 mph collision than in a stall-spin crash-and-burn against solid ground. Furthermore, there were around 93 million cars built and sold last year. There were about 1100 light GA airplanes. You think the manufacturing economies of scale just might be a factor here? And lawyers love airplane crashes and will sue everyone that had anything to do with that airplane, including the airbag manufacturer and the mechanic that didn't inform the owner that periodic maintenance and testing is required.

And car airbag recalls are always happening. My own Ford Ranger had to go in for one a year or two ago, and now there's another one coming up.
 
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