Say there was a notoriously underfloated certified aircraft with few certified choices for floats, none of which were a truly appropriate displacement for the aircraft model as it had a nasty tendency to dig a downwind or outside float. The safe choice would be to up-float by 200-300 lbs.

Is there any history or precedent of successful field approvals for this scenario?

I have "heard of" floats that were field approved, but not for that reason.

Actually, appropriate displacement is about the easiest issue to deal with in a float installation. The bigger issues, that require some engineering know how and understanding of float dynamics is the design of the rigging. Install those floats with a little too much bird's mouth (the distance between the angles of the bottom of the wing vs the bottom of the float keels) or not quite enough, and that plane will not perform well, and could be....sketchy on the water.

I think in the case you noted, if you're serious, I'd find a DAR and ask them to assess the combination. And, I'd definitely want a DAR (or is it a DER?) who knows floats well. What that'll cost? No idea. But, these folks are certified to approve modifications.

The other wild card is the FSDO who's jurisdiction you reside in. When I was in Minnesota (12 years ago), they were still doing field approvals for some stuff. Other FSDOs, not at all. So, it'd be well to touch base with the Minneapolis FSDO first, and float the idea......

MTV

mtv wrote:I have "heard of" floats that were field approved, but not for that reason.

Actually, appropriate displacement is about the easiest issue to deal with in a float installation. The bigger issues, that require some engineering know how and understanding of float dynamics is the design of the rigging. Install those floats with a little too much bird's mouth (the distance between the angles of the bottom of the wing vs the bottom of the float keels) or not quite enough, and that plane will not perform well, and could be....sketchy on the water.

I think in the case you noted, if you're serious, I'd find a DAR and ask them to assess the combination. And, I'd definitely want a DAR (or is it a DER?) who knows floats well. What that'll cost? No idea. But, these folks are certified to approve modifications.

The other wild card is the FSDO who's jurisdiction you reside in. When I was in Minnesota (12 years ago), they were still doing field approvals for some stuff. Other FSDOs, not at all. So, it'd be well to touch base with the Minneapolis FSDO first, and float the idea......

MTV

I got my first ever field approval in the not too distant future, can one just shop FSDOs and apply at a cooperative one?

After all these are aircraft, they travel state to state like most people go from town to town

As a working pilot with a base location, few properties and a boat, combined with all the different state to state legal definitions of “reside” I’m not even sure where I even legally reside, nor would I ever make a statement as such, guess I could honestly be confident in saying “Tellus”

I know the Stinson 108s are pre listed for the EDO 2425 float. I have seen some set up with the EDO 2440 for just the reason you stated.
So what you are asking at least used to be possible.

mtv wrote:So, it'd be well to touch base with the Minneapolis FSDO first, and float the idea......

Niceeeeeee

Zzz wrote:Say there was a notoriously underfloated certified aircraft with few certified choices for floats, none of which were a truly appropriate displacement for the aircraft model as it had a nasty tendency to dig a downwind or outside float. The safe choice would be to up-float by 200-300 lbs.

Is there any history or precedent of successful field approvals for this scenario?

In today's environment, the one-time STC is most likely the direction you will be steered, however, that is a conversation for your FSDO and PMI. Floats have been adapted to differing airframes since the invention of the float. Clayton Scott (Jobmaster Company) adapted the EDO 5250 and 6470 as well as other lesser-known EDO models to the Beaver. These were STC's, as opposed to FA's. There are many other airframe/float adaptation examples to be had, these are two I am familiar with.

The physical task is a process supported by solid factual engineering data, most likely requiring the oversight of a DER. Engineering is validating structural integrity (safety). The details such as final rigging and float to wing incidence is a performance parameter. All of which must be considered as a package to achieve successful results. So, yes, as long as one complies, dare I say it, within the laws of physics, it can be done. You simply need to prove it with sound science and engineering. Whether it is fiscally prudent is a question only the one providing the funding can answer.

TR

Zzz wrote:Say there was a notoriously underfloated certified aircraft with few certified choices for floats, none of which were a truly appropriate displacement for the aircraft model as it had a nasty tendency to dig a downwind or outside float. The safe choice would be to up-float by 200-300 lbs. Is there any history or precedent of successful field approvals for this scenario?

Unless this is a purely hypothetical, generic question,
it seems like if you said what aircraft you're talking about,
someone here might have or know of an approved, better-performing float set-up.

Note on Field Approvals: Any FSDO can sign a field approval, not just your local jurisdiction FSDO, the secret is finding the right FSDO employee who understands what you are working on and the data and is comfortable signing off the approval. The old timers have/are retiring rapidly and the new employees are not so keen to sign off anything.

I have a friend who wanted a firewall battery on a 1958 C180 that was in process for 9 months or longer with PDX FSDO several years ago. He sent in all the documentation as was assured it would be completed in a few weeks. Never happened. I spoke to the AWP Regional Office Flight Standards guy and explained the situation. He told me any FSDO office can sign off, to call the PDX FSDO inspector and tell him LAX FSDO will be handling the paperwork and approval. I called the inspector and got his voicemail and left a message "Reference N123, battery box approval, please shred all the paperwork as LAX FSDO will be handling the field approval" I got a return phone call within 10 minutes and the inspector said I just signed the approval.