Well - I am amazed at the legacy of marketing Edward Simmonds put forward in the late 40s regarding float senders. Edward was for lack of a better term, a wartime optimizer. Edward was sent to the US at the outbreak of WW2 to find innovations in the USA that could help the war effort in Europe. One of those innovations was the Elastic Stop Nut or Nylock This new company partially owned by Mr. Simmonds, contained his initials should not be missed and ESNA went on to capture the market and partially eliminate the tedious and time-consuming wire tying of fasteners in wartime. Edward’s next venture was to use an American capacitive process measurement system and apply this to aircraft. He hired a good Polish engineer to work on the program and came up with a new way to measure fuel in aircraft - using picofarads.
Edward was a marketing genius - his Simmonds Electroprecision ads depicting that floats won’t work in aircraft live on 70+ years after their introduction. I can’t think of another advertising campaign that has that long of legs. It is, however - Marketing and not factual. His ads depict a situation where neither his system nor the one he is replacing will work (Aircraft in a steep dive) he just fails to tell you that small factual bit of information.
So floats aside from 70-year-old legacy marketing - Cirrus has been using CiES senders since 2012. 1.) Cirrus does not stock CiES replacement senders for the existing aircraft fleet. 2.) The CiES Mean Time to Failure in the SR22T is over 90,000 hours or 9 Cirrus aircraft lifetimes. 3.) CiES has supplied over 90,000 fuel senders to the GA legacy fleet. So we can support bold marketing statements with factual information in fact we would be foolish to publish frosting in this litigious environment without the cake to support it.
Capacitive systems deteriorate over time and are subject to corrosion and contamination issues and are extremely sensitive to wiring issues. No capacitive system available for any aircraft has a guarantee of mean time to failure over 10,000 hrs. Capacitive systems require wiring in the fuel tank as the aircraft fuel is an integral electrical component in the system (See FAA Fuel Safety and Lightning Requirements) The no moving parts is an attribute, one that was hyped by Mr. Simmonds, but in my experience, it may be the systems only attribute. Measuring small electrical differences in an aircraft is challenging and is the reason for the dual redundancy of these systems in Transport aircraft. Imagine having a redundant fuel quantity system in GA.
Steel automotive senders in aluminum aircraft are/were the issue, as dissimilar metals in the presence of the water in fuel is the obvious failure point, not the fact that the float pivots. Aircraft float systems from the 1950s made from either Brass or aluminum still work and we have a storeroom full to illustrate this. Cessna 195, DC4, DHC-2
So yes - Floats are not the issue in fuel measurement as buoyancy works. Genius level marketing that floats do not work lives on in the collective aviation conscience. Poor design choices by a majority of GA manufacturers in the 1960’s, 1970’s and 1980’s reinforced that opinion.
The major safety takeaway is that no Cirrus outfitted with CiES senders has had a fuel starvation or exhaustion incident or accident related to fuel indication … to date (Knock on wood). This is now a 10-year-old statement and somewhere north of 20,000 Cirrus fuel senders.
So to some - workarounds (Time, totalizers, and visual inspection) are the key element to fuel safety as that is what most of us were taught. However, these workarounds used by themselves cannot make the same safety statement, as pilots suffer fuel related incidents and accidents at a similar historic rate without change over the last 10 years (Nall report as the reference)
So in this industry - independent data-supported marketing is crucial and definitely not bold.