I don't think you actually need published performance data to operate 702/703. Its really no different than operating off a steep hill runway, or out of mud, etc. Takeoff distances on floats are so variable with technique and conditions that it would be impossible to create an exhaustive chart.
I modded a 182, with 27+ STC's for a client. O-550, MT reversing prop amphib, GWI, and all kinds of wing mods. More than 20 hours of flight testing to approve. But, I was able to demonstrate that the factory, and existing STC performance charts were enough. I was asked by the owner to demonstrate it in and out of a very short Norwegian fjord grass runway years back (it's on Youtube). I did check the numbers, just to be legal for the insurance. 960 foot runway (which I walked first), charts said I'd need 890 feet of runway in and out. It worked with a comfortable reserve - 'cause the plane was better than the books). I flew it out of a really tight Norwegian lake in weird winds last summer, it was a Spidy senses exercise, not stop to look up the numbers, 'cause I did not have lake lengths and hill elevations anyway.
If I can show that performance is not decreased by a mod, or combination of mods, TC generally is open to an argument of "equal to or better than", and leave it at that, if I do some modest flight testing to gather than data to justify that determination. That'd be for a serial limited STC. If it's a full STC, and if TC thinks that there could be a future request for foreign validation, they know there will be more eyes on the file, and they tend to expect more data. I participated in flight testing for a multi mod Turbo Beaver last summer (a magnificent plane!). I gathered extensive climb data, but did not do the formal FTE data correction. TC allowed me to approve that Turbo Beaver with the multi mod combination by sSTC without the corrected climb data. When it came to the full STC, corrected data was required, so an FTE was hired to take my climb data and correct it. I don't know the cost of this effort. (incidentally, the formal correction resulted in climb numbers within one FPM of my uncorrected data, so I was not far off!). With the corrected data in to TC, I'm hopeful for the full STC to be issued this coming week.
Multi modded planes will continue to be a growing concern with TC. Now TC does deserve credit, because they realize, and have expressed to me, that in many cases, there is too much burden to show design compliance for multi mods, but it's a matter of figuring out how much is just right. TC compromises, I get the OK to issue the approval, and we all hope that someone does not go off the end of the lake into the treed, and we're in court trying to explain why the pilot did not have a full set of performance charts for exactly that configuration airplane, with the wave height and winds of the day, that amount of skuzz under the floats, and the water rudders left down.
The industry would help itself by succeeding in making less performance data work just as safely as a full book of charts. And this would go a lot better if pilots did not have performance related accidents, and then there were no lawsuits after the fact, saying that performance numbers were missing! Then, a case could be made to TC that less design compliance was required to be shown in this realm. TC are willing to listen, I've had the conversations with them!
So, with all that, I haven't really helped... Have I?
With respect to your modified airplane I don't understand what the issue is.The STC gives a higher MGTOW as part of POH supplement,so who is saying you can't use the higher gross ?
Finally this airplane has a restricted max weight for a reason. It is an absolute dog off the water at high weights. The upgross kits IMHO simply return the airplane from OK off the water at 3500 lbs to its previous major dogginess. Personally I think the solution to a lot of issues with this airplanes is pretend it is a straight C 180 with a really convenient baggage door and lots of room with only 4 seats installed and only load what you would put in a C 180.
The issue we have is that the authorities here in Europe won't accept the STC upgrade because the POH supplement does not state weight and balance and performance data for 3600 lbs. Aerocet has a revised weight and balance graph in their POH supplement but EDO don´t and authorities won`t approve the graph from Aerocet because of the different floats. We all know that there is no issue in real life but we need to get it approved in our operation manuals and for that we need at least a weight and balance document for 3600 lbs ,better revised performance tables too which obviously do not exist?
We found out that a combination of VG´s and WingX work best by far for our 206´s at max gross even in rough water where we put flaps 20 to 30 during take off run as a procedure. 550 is a good add on too. The 3600 lbs gives us better regularity to be able to accept 4 passengers. With weighty cruise ship customers we often end up just above 3500 lbs and have to reject the 4. passenger because of 20 or 50 lbs.
https://globalnews.ca/news/6169141/nort ... sb-report/
There is a simple solution yet the regulators refuse to act on the issue.
https://www.cbc.ca/news/canada/north/ca ... -1.5037433
Time for the FAA or TSB or TC or whom-ever to grow a set and cease float operations until the breakaway doors are
According to William Thompson, who was the Cessna test pilot who did the certification flight testing the 206 with EDO floats was never certified with a 40 deg flap setting due to a lack of pitch stability and an excessive rate of decent with power off and 40 flap. The lack of climb performance was with the flaps up. The airplane could not meet the minimum rate of climb required by the certification requirements. What is the STC number of the upgrade you are taking about because I have never seen a upgross kit for a stock unmodified C206 on floats ?ScandySky wrote: ↑Tue Nov 19, 2019 6:21 amThat is correct, but not meeting the min. climb rate at 3600 lbs after a balked landing was due to the slow flap retraction speed from flaps 40. Because of the pressure to complete the program back in 1977 the max flap setting was reduced to 30 and the MTOW was reduced to 3500lbs. But today you can buy the STC upgrade to 3600 lbs from EDO/Kenmore and also Aerocet
Big Pistons Forever wrote: ↑Sun Nov 24, 2019 10:21 pmAccording to William Thompson, who was the Cessna test pilot who did the certification flight testing the 206 with EDO floats was never certified with a 40 deg flap setting due to a lack of pitch stability and an excessive rate of decent with power off and 40 flap. The lack of climb performance was with the flaps up. The airplane could not meet the minimum rate of climb required by the certification requirements. I have never seen a gross weight increase for a stock C206 on EDO floats that did not include a wing extension or engine upgrade.ScandySky wrote: ↑Tue Nov 19, 2019 6:21 amThat is correct, but not meeting the min. climb rate at 3600 lbs after a balked landing was due to the slow flap retraction speed from flaps 40. Because of the pressure to complete the program back in 1977 the max flap setting was reduced to 30 and the MTOW was reduced to 3500lbs. But today you can buy the STC upgrade to 3600 lbs from EDO/Kenmore and also Aerocet
What is the STC number ?