Are some high wing singles a bad idea for survey

[pelmet]

I did do a checkout flight in a Cardinal a few years ago. Different type of airfoil from your typical single engine Cessna and nice big doors. I also got a ride a few months back in a nice P210. Pretty cool but those wings sure are long. What supports them. No struts on any Cardinals and no struts on the newer C210's. Must be a lot of stress but I suppose these aircraft have been flying for a long time with a reasonable record.

But what about using them for survey. That is a rough life bouncing through the thermals at low level.

Take a look at this picture of what happened to a 210 in Australia being used for survey. Of course, I don't know much about the structural integrity of these aircraft but the first thing that entered my mind was....why the hell would you use a plane like that for survey. Wouldn't an old 210 with struts would be more appropriate.

https://www.google.ca/search?q=cessna+2 ... qxmLVwAUcM:


https://www.australianflying.com.au/lat ... c210-crash

[Squaretail]

What supports them.

The same thing that supports every other wing that doesn't have struts.

If one examines the wings of the strutless high wing Cessnas, the thing that should be immediately obvious is how much thicker those wings are. If it makes one feel better, there are more (4 instead of 3) bolts that are larger holding said wing on. Personally I'm not sure these airplanes really gain much aerodynamically over their strutted siblings, but that's up for debate. I don't think that over all they are much weaker structurally.

That said, if I recall, there are A/Ds addressing the carry through section of the 210 specifically. For whatever reason they seem prone to corrosion and cracking. I'd suspect that aside from low level survey use, many of them get overstressed from high speed pull outs since many of them were favored IFR machines before the Cirrus took the current reigning spot as the new doctor-killer. More than a few of them have been though some nasty shit. I'd go as far to say that almost every 210 owner I know has had their's through a CB or two. That's also how Scott Crossfield died.

[PilotDAR]

Survey and patrol ops have the potential to put the plane into a rougher life because of the requirement to fly a certain route and altitude regardless. It's not like the pilot can climb for smoother air, they must fly where they're needed to be, unless its simply too rough for the operation at all. This is a "load spectrum" and rather being a few instantaneous jolts, it is a cumulative fatigue effect on a structure over a long service life. Certainly, airframe loads, particularly rough air, have a more severe effect at faster speeds.

The Australian 210 accident which is a pivotal factor in renewed attention to this, had a failure of the center carry through beam, which was suspected to be a growing crack beginning at a point of corrosion. That was May 26, 2019, and to add insult to injury, was VH-SUX. Certainly a possible "harder use" load spectrum on that plane would aggravate the situation. The service bulletins recently issued for the 210's are demanding on a shorter time line, and those for the 177's are about the same demand, though on a longer airframe time in service. Cessna SB SEL-57-06 of June 24, 2019 for the strutless 210's requires an intrusive inspection at 4000 airframe hours for a "typical" use airframe, or at 1500 hours if the airframe use has been "severe". Patrol or survey may be "severe". SB -57-07 for the 177's states 15,000 hours "typical" and 2500 hours "severe" use.

The strut braced Cessnas will be alternately affected, with SB SEB93-5 of May 29, 2019 applicable to 205/206 and 207's. I have reason to believe that other strut braced Cessna may similarly be affected in the near future. FWIW, I did an approval for a C 206 with a spar cap defect. To support my proposal to approve the plane to fly with the defect, and 100 hour inspections, I hired out the full analysis. For this specific condition (not applicable to other defects or conditions, the conclusion reached by qualified analysis was that the defective wing was still okay for more than a million flight hours.

Cessna built fine airplanes, but in fairness, they did not intend an airframe with an unlimited life (though a million + hours sounds sort of like unlimited!)

[photofly]

I did do a checkout flight in a Cardinal a few years ago. Different type of airfoil from your typical single engine Cessna and nice big doors. I also got a ride a few months back in a nice P210. Pretty cool but those wings sure are long. What supports them. No struts on any Cardinals and no struts on the newer C210's.

There are no struts on any low wing GA planes (except the Cessna 188) or any transport aircraft either, and they have the same loads to deal with.

[pelmet]

I did do a checkout flight in a Cardinal a few years ago. Different type of airfoil from your typical single engine Cessna and nice big doors. I also got a ride a few months back in a nice P210. Pretty cool but those wings sure are long. What supports them. No struts on any Cardinals and no struts on the newer C210's.

There are no struts on any low wing GA planes (except the Cessna 188) or any transport aircraft either, and they have the same loads to deal with.

Good point,

It would be interesting to know if there are any structural differences that make them more robust. I think the wingspan is typically less, at least for the older types.

[jakeandelwood]

According to the late John Frank, the author of "Cessna 210 buyers guide" (i have the book and it's a wealth of knowledge on the 210) the later cantilever wing 210s can take a greater structural load than the earlier strut braced models, the carry thru spar is quite noticeable when you look up at the cabin ceiling. There has been a few accidents of low time ifr pilots tearing a wing of a 210, especially the later ones due to getting disoriented in cloud and getting into a spiral, Frank says the strutless wing models build up speed much quicker in a dive. According to the book the wingspan is the same (36'9" ) for most models except the last couple years which is 38'10".

[PilotDAR]

The strutted and cantilever Cessna 210's, as well as 206, and all the 180 series meet the same structural design requirements (the 172's, 152's & 150's meeting the higher strength "Utility" design requirement, and the Aerobats more yet). So yes, you can say that strutted and cantilever are the same "strength" airframes. However, the cantilever wing arrangement is concentrating the loads along smaller load paths, so stronger and heavier parts for the same final strength capacity, and more criticality of a failure (a small crack or defect gets worse faster. The massive spar carry through might have extra design excess, and perhaps results in a stronger yet plane.

Compare this to a biplane, where the wing structure is really the flying and landing wires, so the box structure of the upper and lower wings is where the strength is.

My experience has been that strutted and strutless Cessnas build up speed very quickly if they are RG's. It's the retracted gear which makes them more clean than wing struts. I would expect that an upset in a cantilever 210 and strutted 210 are close to equal in the danger of an overspeed/over stress. I have startled myself in a 182RG too, point it down, it speeds up fast! This is an element of why these aircraft are not spin approved. It's not that they won't spin and recover - they will. It's just that when recovering, there is a much smaller margin against overspeed/over G than the draggier fixed gear, lighter and draggier 172's and 152/150's.

One aspect of survey mods on wings, is that as long as the gross weight is not increased, weight carried out on the wings relieves the wing bending loads, the wings will experience lower bending forces with flight loads, as less of the total weight is in the fuselage. That's why well designed wing tip tanks (some twin Cessnas) allow thinner wings, the lift of wings is in between some of the load, as opposed to each wing being at one end of it. The trade off being that more weight at the wingtips creates more inertial force to overcome in a spin recovery - everything is a balance!