It would be interesting to know on older designs, and on new designers, the process involved in calculating the MTOW.
I agree with the previous poster that it is a very dangerous game to second guess the professionals and makes it all to pointless to have engaged them in the first place if this is your intention. However, without advocating doing so, at least if you are determined to do so, it would seem to make sense to understand how they arrived at their calculation in the first place.
There is a case, but I dont know whether this is true in aviation, that in some walks of life the longer you go back the greater the tolerance that was built into many structural calculatons partly because our understanding was not as precise as it is today. I am also aware that there is some evidence in some areas of aviation that experience has demonstrated that the POH is not always the best course of action. For example I agree with an earlier poster with regard to the best approach speed for a 22. I can also recount where I very carefully followed the POH after an engine failure in a twin. Subsequently a number of representations were made that the POH probably did not set out the best course of action and it was, as a result, changed. So there is some evidence that the POH is not always the best document to follow, which comes full circle to the question of W and B and on what evidence you rely if you feel you can safely either exceed the manufacturers MTOW or COG calculations. In short, if you are basing your decision on “it seemed like a good idea at the time”, then you surely must be nuts, but if it is based on something more, then it would be interesting to have that discussion.
Peter wrote:
Nearly all readers of PuF are Germans and in common with most countries few of them ever go outside their own country – especially one which is so well organised.
They may be German speakers but I doubt they belong to that kind of group. P&F does not appeal to the 200$ burger crowd, apart from the trip reports it is too technical for them. P&F is the one aviation mag I know in Europe which really is for the serious pilots and airplane owners, who don’t just want to read plane porn but to be kept aware of what is going on and what is out there. At the moment, it is the only mag I still do subscribe to. They are also the only folks who run their on fleet of GA planes.
Quite a few of the membership here is also seen in the P&F forum. I’d think the crowd that reads P&F is pretty similar to the interest scope of this forum.
And I am in full agreement with Bosco and Flyer as to that Germans are probably the most active GA community with more than a small percentage of pilots who will fly across borders quite regularly. I’d count the Swiss to a similar crowd, mainly because they can’t do much more than a circuit without crossing a border, as well as the Austrians. And there are quite a lot of high performance planes around in these three countries as you need them to do some serious travelling.
Yes, speed is important for touring. I’d say 150 kts is the minimum a serious touring plane should have, combined with a at least 600-700 NM realistic range. 180→200 kt and 1200-1500 NM would be my definition of an ideal traveller, possibly including FIKI. There is quite a lot of such airframes around.
The tests P&F used to do (and I hope we will see more of them!) were and are exactly what serious buyers should be reading. Many “Pilot reports” in more pedestrian mags are pure plane porn, where some editor with often questionable qualifications for the job go for a free ride with a marketing pilot and then will deliver a nice picture book with 3 lines about performance and cost, but raving about the size of the ashtrays if you get my drift. That is not what I am interested in reding, but what a plane can actually do. Most of this does not even require a “test flight” but mainly the POH and a lot of research.
mh wrote:
Then you have to read the report again.When I read the report again, it reads the same as the first time.
Auszug aus dem Flug- und Wartungshandbuch CTSW: … Die getestete Höchstgeschwindigkeit (V_NE) ist 301 km/h, sie ist jedoch durch die maximale Auslösegeschwindigkeit des Junkers Rettungsgerätes auf 260 km/h IAS beschränkt…
Flight tests have shown the trim tab flutters at 275 kph, resulting in an emergency AD, reducing the VNE down to 225 kph, unless a modification of the trim tab is executed.
Flight tests carried out after the accident.
mh wrote:
A good structure breaks when it is supposed to break.
I watched a video of the static load testing of the A380 (I believe) wings. They are required to withstand 150% of the maximum load without breaking. They broke at 151% load. A very impressive feat of engineering indeed.
I used to be in the business of breaking wings (and I’m still alive 
) because one of the product lines of my company was static and fatigue test equipment.
Indeed properly designed aircraft wings are designed against 150% max load, verified on a static test rig. It is amazing to see how they bend up almost vertically. Really properly designed wings would break at multiple points just above 150%, but this is very hard to achieve apparently. If it breaks at just one spot, the rest of the structure is too strong and thus too heavy. Lots of funny stories too on these tests, like the shock wave of one break event blowing off the roof of the building. No, I’m not at liberty to disclose which at which company this happened, plus it would maybe embarrass a (ahem) major contributor to this forum, because it was in his home country
I seem to remember a great many years ago that GA aircraft being ferried from the USA to Europe were given special one off permissions to leave well above max weight because of the fuel load needed to cross the north Atlantic to the first available re-fuelling point. Can anyone point to any details on this please? (Or is my memory failing me in old age?)
Rumour has it they were really unsatisfied with 151%. Should have been 150% and the aircraft could have been lighter.
Airborne_Again wrote:
They are required to withstand 150% of the maximum load without breaking. They broke at 151% load. A very impressive feat of engineering indeed.
No. It’s a very impressive feat of manufacturing accuracy, but poor engineering as it leaves no error whatsoever to manufacturing defects or wear and tear, while still keeping the 150% design limit. Even the slightest repair, temperature difference, one one broken bolt etc, and you are off. But then again it’s a design limit, not a real limit, so the whole point of hitting the 150% line is just nonsense. They say an RV is within structural design limits even with half of the rivets. If it’s true or not I don’t know, but it probably is very close since it is designed for everybody to put together.
I always thought that the design margins are there to allow for the inevitable deviation from the design, be it temporary (bird strike, unnoticed damage) and ageing.
I have flown overweight many times. Nearly always, it was in accordance with a flight authority which included that permission. Examples being A Cessna 207 200 pounds over, Cessna 208 100 pounds over, Twin Otter 2500 pounds over, and 172 100 pounds over. All of those flight authorities included limitations, and in some cases a G meter to assure that 2.5G was not exceeded in flight. The structure can handle some additional weight at 1G, its when you start pulling G’s, the risk increases.
I have purchased a 300 pound gross weight increase kit for the 182 amphibian, but in truth, buy the time you finish the installation, and meet the conditions, it’s really not a 182 much any more.
In my very early days, I used to fly a private 182 for it owner from time to time, hauling his cargo on personal trips. The one day I arrived, and he had it all loaded. He told me: “Take ‘er easy, she’s heavy today.” Yes, it was. I still got out of the 1600 foot turf runway which was home, and the performance was still fine, but I noticed it wanted to be flown faster on approach to feel comfortable. I was able to weigh what was unloaded at the other end, and did the math. I have been a touch over 800 pounds overgross! Not safe! I had a stern talk to the owner. I flew jumpers in a 185 for two seasons, but gave up because of their apparent insistence on the aircraft carrying more than gross. Morally, I can risk myself and some cargo for a little overweight, but not other people.
