Here’s a little Piaggio video for you guys. The fastest biplane I’ve ever flown for sure:

https://m.youtube.com/watch?v=6bbDyhBNx1c

Awesome video!

One quibble / I think fuselage lift contribution is closer to 20% of lift at cruise! Will double check though…

I remember checking out this plane somewhere in Texas in 2020. Didn't go for it at the time.

How did you all conclude that fuselage lift is a good thing? Every pound of lift that is generated by the fuselage is a pound that is not generated by the wings. Wings are more efficient at generating lift, and therefore generate less induced drag. 20% fuselage lift sounds like a more sellable way of saying “x% more induced drag.”

Are you sure that this is a feature and not a bug? Is is possible that the designers noticed “Ah %#$@, the fuselage is generating lift — and drag!” and then the marketing folks said “Oh, cool, the fuselage is helping!”

We do have to take pitching moment into account, of course, and it’s possible that the fuselage is offloading the forward wing and horizontal stabilizer, allowing them to be smaller, lighter, and less draggy, but in general, bluff bodies aren’t particularly good lifting bodies.

And no, the fact that the P180 is faster than other similarly sized and similarly powered airplanes is not proof that fuselage lift is good. Drag is a sum of many contributions, and speed is very engine and altitude dependent.

Mind you, I still want one

Your friendly neighborhood engineer,
Martín

It is better than a fuselage that is only drag.

A fuselage is a necessary element to make the plane useful. Given that, if it generates lift, all the better.

I'm pretty sure my fuselage generates negligible lift during cruise flight.

Mike C.

It is better than a fuselage that is only drag.

A fuselage is a necessary element to make the plane useful. Given that, if it generates lift, all the better.

I'm pretty sure my fuselage generates negligible lift during cruise flight.

Mike C.

Martin / I believe the fuselage lift in Piaggio enables smaller wings and less drag in general. I have read before it is considered one of the most optimized production airframes ever built.

20% of lift would be better than none, which would just be additional induced drag.

The fact the cabin is 6’ wide (same as a Falcon 50) also might make an argument that a ‘bigger’ cabin is more useful than ‘bigger’ wings!

The triple lifting body patent was for fwd wing, main wing and tailplane. I believe the fuselage lift was an added bonus to the design.

The primary reason for the forward wing AND the fuselage lift is to eliminate the need for downward lift force on the tail in cruise. This is a huge benefit in induced drag reduction far more than any drag reduction emanating from the production of lift by the fuselage. The specs speak for themselves. Plus as Mike said above a "normal" fuselage just creates drag *mostly*

There was a joke going around at Cessna that with enough lifting surfaces, you could get interference thrust.

Hi,

Anyone care to comment on this discrepancy after a four hour flight? If you also have it, how do you deal with it? Maybe there's a way to update the FMS from the fuel sensors in flight?

I don’t have that issue nor do I have the Collins system, but it seems like the fuel flow sensor logic may need a slight tweak to the K factor. I don’t know how to do it on the Collins system but hopefully someone does(?).

edit: After I posted this, I realized one must first ask which is accurate, the totalizer or the quantity gauges? If the totalizer is the accurate part then obviously you need your fuel quantity gauges calibrated instead.

I have never seen a totalizer and fuel gauge stay in perfect sync, though this discrepancy is relatively large. Though, FWIW, in my Avanti I, my Garmin totalizer and OEM fuel quantity stay very tight, tighter than the fully OEM system in my TBM did. I wonder if that's because the center tank is less impacted by OAT and/or mitigated by the fuel/oil heater.

Some places I might investigate as well:
+ Is the ending discrepancy the same if you start will full tanks, or slightly less than full tanks? If you can put more than 2800 lbs (assuming you don't have extended tanks) into the plane, perhaps due to fueling temperature, but only load 2802 lbs on the totalizer, that can create a difference.
+ Does the difference simply increase linearly over the course of the trip? EG, changes in fuel temperature can create volumetric changes in fuel amount in systems that don't actually weigh fuel. Is the difference greater when you fly very high vs less high?

I would collect periodic data over the course of the flight and note original fueling qty and cruise flight level in the hope that helps identify the source of the issue.

Capacitance fuel gauges, which is what I presume the Piaggio has, require calibration for at least empty ad full points.

On my Citation, I ran each tank dry (transfer to other one) and discovered the fuel gauges read 200 lbs when the tanks were dry. If I was down to 400 lbs indicated, I actually had no fuel on board. It was trivial to adjust to a proper setting ( trim screws on back of gauge) to get it right. I presume such a thing is doable with the Piaggio.

People don't operate in the low fuel regime very often, so it would be ideal is every now and then, you ran the tanks dry on the ground and checked your fuel calibration. You may find it was way off and that explains the gauge readings.

Mike C.