Strength of high-wing versus low-wing single piston aircraft
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Strength of high-wing versus low-wing single piston aircraft
I have been told that the strength of low-wing, "strutless" aircraft is signigicantly higher than that of high-winged "strutted" aircraft, most obvious example being the Cessna 152 / 172 trainers that many of us fly. The opinion given to me was that many more wings have come off Cessna's than high winged aircraft (example given was Mooney, who are I believe known for very strong wings). Another statement was "that is the strut breaks, you die". I'm not really sure what the significance of this statement is however, because perhaps it's the same thing as saying "that if the main spar in a Mooney wing breaks, you die..."
Even if this is true...if say the Mooney is a lot stronger, how often is a wing-loss accident reported? Isn't this incredibly rare?
I am not trying to make a ridiculous post or cause any trouble, just trying to see what the forum's opinion is of wings that require strut bracing as opposed to those that don't, and trying to get an idea of how many if any wing losses we've had on Cessna aircraft.
Even if this is true...if say the Mooney is a lot stronger, how often is a wing-loss accident reported? Isn't this incredibly rare?
I am not trying to make a ridiculous post or cause any trouble, just trying to see what the forum's opinion is of wings that require strut bracing as opposed to those that don't, and trying to get an idea of how many if any wing losses we've had on Cessna aircraft.
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If the strut brakes on my Baby, will I die?
###Ultra Long Hauler###
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If the strut breaks on your strut braced Cessna, well, it's not going to end well. That said, it is widely accepted that there has never been the failure of a strut braced Cessna in flight. I am aware of a 185 which was so badly overstressed recovering from a spin through cloud, that the wings were bent outboard of the strut. It still landed safely, and the wings were rebuilt.
I'm not knocking low wing aircraft, but their wing spar structure will be heavier as it concentrates all the load path through the thickness of the spar, rather than spreading it out higer and lower along the fuselage.
I believe that the only Cessna singles which have suffered an inflight strutural failure were the 177, and 210 strutless (though I have no details). Though the structure of these types is as strong as their strutted and low wing competitors, they are very sleek, and more prone to overspeed if upset, or mishandled. Overspeed will easily equate to overstress with unfortunate pilot technique. These two type, as others, but these in particular, should not be "fooled around" in!
I was recently involved in the approval of a repair scheme for the wing attachment of a Piper Seneca. As I came to understand the structure of that aircraft, and the criticality of one left and right pair of parts, I was very alarmed to know that they are not only corrosion sensative single point failure, but some were known by the factory to be cracked across, and allowed to remain so, with no further need for inspection. After all that, heaven help you if you want to replace them, as Piper no longer sells them!
All certified "normal" category aircraft pass the same structural requirements at certification. Have faith, they're safe. They will withstand at least 5.7G and still be landable. Just fly and maintain them well.
Though losing a wing, would be a very very big hazard, it is incredibly unlikely. There are many more common, simpler hazards, which are going to catch you first, watch for those!
I'm not knocking low wing aircraft, but their wing spar structure will be heavier as it concentrates all the load path through the thickness of the spar, rather than spreading it out higer and lower along the fuselage.
I believe that the only Cessna singles which have suffered an inflight strutural failure were the 177, and 210 strutless (though I have no details). Though the structure of these types is as strong as their strutted and low wing competitors, they are very sleek, and more prone to overspeed if upset, or mishandled. Overspeed will easily equate to overstress with unfortunate pilot technique. These two type, as others, but these in particular, should not be "fooled around" in!
I was recently involved in the approval of a repair scheme for the wing attachment of a Piper Seneca. As I came to understand the structure of that aircraft, and the criticality of one left and right pair of parts, I was very alarmed to know that they are not only corrosion sensative single point failure, but some were known by the factory to be cracked across, and allowed to remain so, with no further need for inspection. After all that, heaven help you if you want to replace them, as Piper no longer sells them!
All certified "normal" category aircraft pass the same structural requirements at certification. Have faith, they're safe. They will withstand at least 5.7G and still be landable. Just fly and maintain them well.
Though losing a wing, would be a very very big hazard, it is incredibly unlikely. There are many more common, simpler hazards, which are going to catch you first, watch for those!
You'd have to actually read the stats to know how many wings have come of aircraft, high vs low mounted, and then eliminate from that statistic those accidents that were caused by the pilot yanking them off by, say, getting disoriented in IMC, exceeding the design or safe operating speed, and pulling back on the pole.
In my experience, wing failures on a normally maintained light aircraft almost always occur because the pilot exceeded the design load. I've looked into this a bit, because I was quite interested in the nature of the various structures that insulate the body from a 1000ft plunge.
Certain types developed a bit of a reputation for shedding parts. Invariably, this was not because they were less strong than their counterparts, it was usually because they had "slippery" airframes that gained speed rapidly in a spiral dive. They include the Cessna 210, and the Beech Bonanza. (Resp. Hi wing/lo wing.)
The only accidents involving structural failure I know of (my awareness will, of course, be far from complete) where the pilot was not the causative factor involve fatigue/inadequate maintenance. There was one P28R accident in the UK some time ago, where I believe the definitive cause could not be determined (what was the event that caused the outer wing panel to start unraveling) but generally, it's because the pilot, VFR rated, operated the aircraft into an area of reduced visibility/IMC, became spatially disoriented, allowed the aircraft to enter a spiral dive.
This general accident classification sometimes includes pilots operating an aircraft in IMC, too. Commonly they venture into an area of adverse weather (Cb/Ts, for example) and lose control of the steed.
The Bonanza sometimes has the nickname "fork-tailed doctor killer". It's a (somewhat complex) high performance type often favoured (or was often favoured) by those with spare money, who wanted something a bit perkier than a 172 or PA28.
I've never heard of a 172/152 wing coming off. They are unusually robust. (As are most light aircraft.)
In my experience, wing failures on a normally maintained light aircraft almost always occur because the pilot exceeded the design load. I've looked into this a bit, because I was quite interested in the nature of the various structures that insulate the body from a 1000ft plunge.
Certain types developed a bit of a reputation for shedding parts. Invariably, this was not because they were less strong than their counterparts, it was usually because they had "slippery" airframes that gained speed rapidly in a spiral dive. They include the Cessna 210, and the Beech Bonanza. (Resp. Hi wing/lo wing.)
The only accidents involving structural failure I know of (my awareness will, of course, be far from complete) where the pilot was not the causative factor involve fatigue/inadequate maintenance. There was one P28R accident in the UK some time ago, where I believe the definitive cause could not be determined (what was the event that caused the outer wing panel to start unraveling) but generally, it's because the pilot, VFR rated, operated the aircraft into an area of reduced visibility/IMC, became spatially disoriented, allowed the aircraft to enter a spiral dive.
This general accident classification sometimes includes pilots operating an aircraft in IMC, too. Commonly they venture into an area of adverse weather (Cb/Ts, for example) and lose control of the steed.
The Bonanza sometimes has the nickname "fork-tailed doctor killer". It's a (somewhat complex) high performance type often favoured (or was often favoured) by those with spare money, who wanted something a bit perkier than a 172 or PA28.
I've never heard of a 172/152 wing coming off. They are unusually robust. (As are most light aircraft.)
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The utility category has a 3.8G design load, as compared to the normal category.
There have been some main wing spar failures, especially on bigger aircraft where the loads are higher:
There's the famous firefighter Hercules clip.
And Swedish Customs had a catastrophic wing spar failure on one of their CASA C-212 killing all aboard a couple of years ago.
2006 Falsterbo Swedish Coast Guard crash - Wikipedia, the free encyclopedia
And the later models of the aircraft I own, the Aero Commander, have had a couple due to galvanic corrosion. The main spar was a stainless steel/aluminum sandwich, which proved to be prone to corrosion. It's subject to a permanent AD and have to be inspected or replaced with a new brace. Thankfully my old 520 doesn't have that as it was before they did the sandwich. Mine is all aluminum, so I'm in the clear. I do have a one time front spar inspection at 6000hrs, which is coming up in a few years, but it's a pretty cheap one off.
There was also a recent Robin R400 in the UK that had one wing come off after having hit a hay bale on a previous landing that had given undetectable wing box cracks. The Robin has a wooden main spar. This is however not something to fear in itself. Bellanca Vikings, Mooney M20A's, Extra 300 aerobatic and hundreds more have had and still have wooden main spars and they haven't had more failures than metal ones, if any.
It's of course every pilots nightmare to have a main spar failure, but thankfully they're very rare.
There have been some main wing spar failures, especially on bigger aircraft where the loads are higher:
There's the famous firefighter Hercules clip.
And Swedish Customs had a catastrophic wing spar failure on one of their CASA C-212 killing all aboard a couple of years ago.
2006 Falsterbo Swedish Coast Guard crash - Wikipedia, the free encyclopedia
And the later models of the aircraft I own, the Aero Commander, have had a couple due to galvanic corrosion. The main spar was a stainless steel/aluminum sandwich, which proved to be prone to corrosion. It's subject to a permanent AD and have to be inspected or replaced with a new brace. Thankfully my old 520 doesn't have that as it was before they did the sandwich. Mine is all aluminum, so I'm in the clear. I do have a one time front spar inspection at 6000hrs, which is coming up in a few years, but it's a pretty cheap one off.
There was also a recent Robin R400 in the UK that had one wing come off after having hit a hay bale on a previous landing that had given undetectable wing box cracks. The Robin has a wooden main spar. This is however not something to fear in itself. Bellanca Vikings, Mooney M20A's, Extra 300 aerobatic and hundreds more have had and still have wooden main spars and they haven't had more failures than metal ones, if any.
It's of course every pilots nightmare to have a main spar failure, but thankfully they're very rare.
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Stick with 172's
There have been about 45,000 Cessna 172's built over more than 55 yrs.
They have been flown millions of hours in all kinds of weather by mostly low-time amateur pilots.
Some airframes have flown in excess of 30,000 hrs.
They have all been built to utility category standards.
There have been two cases of structural failure resulting in fatalities.
Both of these were caused by abrupt pushovers, in good weather, to the inverted, for unknown reasons.
No other airplane ever built can match that record for structural integrity.
And don't forget, the 172 is the only airplane ever to successfully penetrate Soviet air defenses all the way to Moscow.
They have been flown millions of hours in all kinds of weather by mostly low-time amateur pilots.
Some airframes have flown in excess of 30,000 hrs.
They have all been built to utility category standards.
There have been two cases of structural failure resulting in fatalities.
Both of these were caused by abrupt pushovers, in good weather, to the inverted, for unknown reasons.
No other airplane ever built can match that record for structural integrity.
And don't forget, the 172 is the only airplane ever to successfully penetrate Soviet air defenses all the way to Moscow.
Maybe we should go back to biplanes? This sounds like a debate of the thirties & forties. Show me a high wing strut braced monoplane competition aerobatic aeroplane. Think about it. Its about the design, not the configuration.
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There are very few GA aircraft types which have never had a wing failure.
I am pretty sure everything from Cessna and definitely everything from Piper has lost wings.
But it's bound to happen if you fly into bad enough weather at a high enough speed.
I fly a TB20 which has had only one known wing failure and that was in a CB in Sweden, reportedly. That's across 2000 airframes. The TBM700/850 has never had an in flight structural failure but one would jolly well hope so since it has radar so should not just casually pop into a CB
I don't see a fundamental difference between low wing and high wing ability to carry + or - G. It's just that every airframe will have been designed for the max certified G plus a margin, and not a lot more otherwise you just end up carrying unnecessary weight. You could easily build a plane which can take +/-20G but it would have a small payload If you built it out of composites it would cost too much. So a plane with a wing strut will in general have a weaker wing than one without, because of the strut being there.
Personally I far prefer low wing for far superior visibility in turns, much easier refuelling and the ability to easily visually inspect the fuel level, but it has disadvantages too: not so good for taking photos looking down, entry is harder for old/stiff people because they have to step up onto the wing.
Retractable gear design is a lot harder with a high wing, and high wing planes are very susceptible to being chucked around by surface wind (which is a problem for both parking where strapdowns are necessary a lot of the time whereas if you have a 1400kg low wing plane it would take a hurricane to shift it, and for crosswind performance).
But high wing planes are easier to land due to having much less ground effect so if you come in too fast it doesn't glide all the way down the runway
I am pretty sure everything from Cessna and definitely everything from Piper has lost wings.
But it's bound to happen if you fly into bad enough weather at a high enough speed.
I fly a TB20 which has had only one known wing failure and that was in a CB in Sweden, reportedly. That's across 2000 airframes. The TBM700/850 has never had an in flight structural failure but one would jolly well hope so since it has radar so should not just casually pop into a CB
I don't see a fundamental difference between low wing and high wing ability to carry + or - G. It's just that every airframe will have been designed for the max certified G plus a margin, and not a lot more otherwise you just end up carrying unnecessary weight. You could easily build a plane which can take +/-20G but it would have a small payload
If you built it out of composites it would cost too much. So a plane with a wing strut will in general have a weaker wing than one without, because of the strut being there.Personally I far prefer low wing for far superior visibility in turns, much easier refuelling and the ability to easily visually inspect the fuel level, but it has disadvantages too: not so good for taking photos looking down, entry is harder for old/stiff people because they have to step up onto the wing.
Retractable gear design is a lot harder with a high wing, and high wing planes are very susceptible to being chucked around by surface wind (which is a problem for both parking where strapdowns are necessary a lot of the time whereas if you have a 1400kg low wing plane it would take a hurricane to shift it, and for crosswind performance).
But high wing planes are easier to land due to having much less ground effect so if you come in too fast it doesn't glide all the way down the runway
Last edited by IO540; 13th Apr 2011 at 06:41.
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If you look inside the headlining of a Cessna 177 Cardinal (strut-less) you will what is effectively a low wing stricture mounted on the top of the fuselage instead of on the bottom. And of course the wheels are mounted on the fuselage as well which reduces the stresses on the wing.
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And of course the wheels are mounted on the fuselage as well which reduces the stresses on the wing.
GA hulls are normally pretty flimsy.
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IO540
It's swings and roundabouts if you put the wheels on the wing then you have have a stronger spar if you put the wheels on the fuselage you have to have a stronger frames. Probably has little difference in weight.
High wing aircraft make a good shelter when it's raining:-)
It's swings and roundabouts if you put the wheels on the wing then you have have a stronger spar if you put the wheels on the fuselage you have to have a stronger frames. Probably has little difference in weight.
High wing aircraft make a good shelter when it's raining:-)
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"Show me a high wing strut braced monoplane competition aerobatic aeroplane."
The Bellanca Super Decathlon was doing quite well at standard level a couple of years ago......
The Bellanca Super Decathlon was doing quite well at standard level a couple of years ago......
The strength requirements are identical regardless of configuration.
In an unstrutted wing, the strength will be identical therefore.
A strutted wing will clearly not be as strong as an unstrutted wing, because much of the load is taken by the struts.
The strut itself is usually much stronger in tension than compression, because a long slender strut is very hard to make strong enough against buckling loads.
Even if it is strutted, the strength needs to be the same outboard of the strut attachments.
So, outboard of any strut attachment, I'd expect high and low wings to be the same. And if there are no struts, I'd expect high and low wings to be the same.
I'd expect the section of the wing inboard of the strut of a strutted wing to be less strong than the same part of an unstrutted wing, because the strut is doing a lot of the work.
It is possible, because of the mechanics of the strut, that a strutted wing designed just strong enough in negative g, is slightly stronger than it needs to be, in positive g.
I don't do that sort of work at present, but am still a CAA design signatory for small aeroplanes. Interestingly, I just worked out that of the 15 designs that are flying on my signature, every single one was high wing and either cable braced or strutted. I wonder why I never got a low wing to do?
G
In an unstrutted wing, the strength will be identical therefore.
A strutted wing will clearly not be as strong as an unstrutted wing, because much of the load is taken by the struts.
The strut itself is usually much stronger in tension than compression, because a long slender strut is very hard to make strong enough against buckling loads.
Even if it is strutted, the strength needs to be the same outboard of the strut attachments.
So, outboard of any strut attachment, I'd expect high and low wings to be the same. And if there are no struts, I'd expect high and low wings to be the same.
I'd expect the section of the wing inboard of the strut of a strutted wing to be less strong than the same part of an unstrutted wing, because the strut is doing a lot of the work.
It is possible, because of the mechanics of the strut, that a strutted wing designed just strong enough in negative g, is slightly stronger than it needs to be, in positive g.
I don't do that sort of work at present, but am still a CAA design signatory for small aeroplanes. Interestingly, I just worked out that of the 15 designs that are flying on my signature, every single one was high wing and either cable braced or strutted. I wonder why I never got a low wing to do?
G
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I'd expect the section of the wing inboard of the strut of a strutted wing to be less strong than the same part of an unstrutted wing, because the strut is doing a lot of the work.
Why do you say this? I would think that the wing is equally strong along its whole length, given that the ones I know (C172 and Auster) have spars that don't change.
As I see it, the struts are only there because the bottom of the spar stops at the cabin - the struts just stop the wing rotating relative to the fuselage.
I don't see that there would be extra strength for positive g operations but could see the struts putting in discontinuities during overload cases.
Don't you think?
I would think that the wing is equally strong along its whole length, given that the ones I know (C172 and Auster) have spars that don't change.
s I see it, the struts are only there because the bottom of the spar stops at the cabin - the struts just stop the wing rotating relative to the fuselage.
It may also be true that most or all of the strutted high wing designs were done in days before there were any formal structural requirements for GA aircraft.
Anything post 1950 definitely had to meet formal structural requirements, and most stuff post 1930.
G
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It may also be true that most or all of the strutted high wing designs were done in days before there were any formal structural requirements for GA aircraft.
You may be right but then again... when you look at the structure inside a C172, it's all pretty well engineered!
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172 breakup
I believe there has only ever been one recorded wing loss accident involving a C172.
ASN Aircraft accident 21-MAR-2003 Cessna 172S N219ME
I recall this being discussed in the past.
ASN Aircraft accident 21-MAR-2003 Cessna 172S N219ME
I recall this being discussed in the past.
MIA03FA043
@AdamFrisch,
It is my understanding that normal category is +3.8, and utility category +4.4/-1.7.
I seem to recall the minus value in the normal cat is about 1.4?
It is my understanding that normal category is +3.8, and utility category +4.4/-1.7.
I seem to recall the minus value in the normal cat is about 1.4?