Piaggio P180 Avanti with 3 pitch control

Picture source.

I have seen that there is kind of sonic aircraft like B-1B Lancer that used elevator and canard or fins at the same time for pitch control. That quite understandable because it is fighter jet that required high precision control. There are another airplane that used canard but not elevator, like Tupelov Tu-144. But this Piaggio P180 Avanti is quite strange for me. It is equipped with elevator, canard, and also another additional device. I am not sure that propeller airplane needs what needed by the above B-1B Lancer.

Then my question are, what is that device (number 2 in the picture), what is that name, and what is that for? Are device number 2 and number 3 controllable?

  • 1
    $\begingroup$ Surface 2 is not for pitch but for directional stability and boundary layer control. $\endgroup$ Sep 18 '19 at 14:38
  • 4
    $\begingroup$ B-1 is not a "fighter". Also, Tu-144 certainly did have elevators, in the form of elevons. Its canard was probably not used as a primary pitch control. $\endgroup$ Sep 18 '19 at 16:24
  • 1
    $\begingroup$ What is that mean directional stability and boundary layer control? What is that boundary layer control and how it work? $\endgroup$ Sep 18 '19 at 19:10
  • $\begingroup$ @AirCraftLover, you may want to ask about boundary layers as a separate question in the Physics Stack Exchange. It's part of "fluid flow" or "fluid dynamics." Air flowing over the surfaces of an aircraft is an example of fluid flow; there are several different kinds of flow that occur near or next to a surface. A boundary layer is when the flow changes from one type to another. There's QUITE a bit of material to understand to answer the question "how it works." $\endgroup$
    – Forbin
    Sep 19 '19 at 19:17
  • $\begingroup$ OK, sure. Thanks. $\endgroup$ Sep 19 '19 at 19:28

Surface 1 is a horizontal stabilizer with elevator, just the same as on any other aircraft with a T tail arrangement.

Surface 2 is called a rear strake or a tail fin. There is one on each side of the fuselage. They provide extra stability during operation at high angles of attack when the fuselage is disturbing the airflow to the vertical tail. They are not movable.

Surface 3 is a canard, providing extra lift. The canards on P.180 have a trailing edge flap. The flap is necessary to counteract the nose down trim of the flaps in the main wing. Without the canard flaps the elevator would not have sufficient authority to maintain adequate pitch control when full flaps are deployed on main wings.

Surfaces 1 and 3 have movable parts, but surface 1 is the only surface connected to pitch axis control of P.180.

Piaggio P.180 article on Flying magazine explaining design features (and a lot more).

Rear strakes- tail fins on Wikipedia

  • $\begingroup$ Is that the trailing edge flap of the canard also acting like wing for the nose? $\endgroup$ Sep 18 '19 at 12:50
  • 3
    $\begingroup$ The whole canard (with the flap) is acting as a wing for the nose, that's what canards do. The canard trailing edge flap is there to add lift when flaps on the main wings are extended. This keeps the aircraft in balance. $\endgroup$
    – Jpe61
    Sep 18 '19 at 13:04

No. 2 is a ventral strake and No. 3 is a canard. Neither have actuated control surfaces on the P.180. The ventral strakes are there to provide additional directional stability and the canards provide a more direct longitudinal balance and control, alleviating tailplane loads, and improving low speed handling.

The Avanti was built for speed (400 KTAS in a turboprop!) and quite a bit was sacrificed for that. Note the thin, high aspect ratio wings and lifting body fuselage.

  • $\begingroup$ I believe the ventral strakes are also a remnant of the early (but short-lived) involvement of Learjet in the designing of the aircraft. Hence the same design can be found on the empennage of Learjets. $\endgroup$
    – Simon Opit
    Sep 18 '19 at 10:06
  • 1
    $\begingroup$ Ventral strakes are common a wide number of aircraft, not just Avantis and Learjets. In truth, just like preset trim tabs or dorsal strakes they are additions made to correct undesirable performance eharacteristics found in development or flight test ie “Band-Aids for bad airplane design”. $\endgroup$ Sep 18 '19 at 15:13
  • $\begingroup$ Agreed, they certainly are found on many other aircraft, from the Q400 to light amphibians. But I think the design is clearly very similar to the Lear. Anyway, the band-aid analogy is a good one, which why the Beech 1900D is covered in strakes and other 'aero-band-aids'. $\endgroup$
    – Simon Opit
    Sep 18 '19 at 20:31

Why there so many pitch control surfaces on the Piaggio P180 Avanti?

You mark 3 surfaces, but only one is movable, i.e. there is only one pitch control surface on the P180, not "so many".

what is that device (number 2 in the picture), what is that name, and what is that for?

Don't know the name myself, but it is there to guide the airflow around the back of he fuselage.

Are device number 2 and number 3 controllable?

not for continuous pitch control, see above and Jpe61's answer

  • $\begingroup$ In my understanding, pitch control is to control the nose up and/or down. The canard has it trailing edge which also acts to up/down the nose. So, it is also pitch control. I don't think that it is used to roll, moreover to yaw. Isn't it? $\endgroup$ Sep 18 '19 at 23:50
  • $\begingroup$ @AirCraftLover that's why I specified continuous. a flap is a discrete control, in a completely different category from what usually people refer to as "pitch control". the latter is usually reserved for surfaces connected to the stick, that can command any angle between their extreme deflections. A flap is none of that. $\endgroup$
    – Federico
    Sep 19 '19 at 5:10

There is really some useful information in all answers. Two design choices really make me wonder how hard engineers worked to create that aircraft.

First; ventral strakes or tail fins. They are canted 45 degrees. Which means they provide both pitch and directional stability. I also think they provide little bit of dihedral effect. Actually that maybe the main reason looking at straight mid-body wings and rectangular shape of engines. I’m sure they suffered from roll instability at the beginning. Canted ventral fins looks like a quick aerodynamic band-aid.

Second the front wings (as company calls them, not canards). It really wouldn’t make sense if they were really fixed small wings in front. They would make aircraft unstable in pitch. As the AOA increases lift of those front wings would increase also and aircraft would want to pitch up more and go out of control.

enter image description here

The truth is as @Jpe61 mentioned in his comment and as you can see at the beginning of that video they have trailing edge control surfaces. Looking at the location of wings and engines I think they suffered from aft CG problem and fixed that with the forward wings. I believe they produce downward lift though which provides stability at the expense of efficiency.

Lastly; I want to say that the more extra surfaces you see on an aircraft, thats the testament that basic aircraft has relatively more stability and control issues. Though that's not a bad thing on itself if its fixed properly.

Don't want to spark a discussion, but turns out that the most worshipped designs are the flawed ones. Don't believe me; look at P-51 Mustang or F-4 Phantom. :))

  • $\begingroup$ A fixed canard does not make an unstable aircraft. It will definitely reduce stability but you need a larger canard to actually make an unstable aircraft. $\endgroup$
    – Sanchises
    Sep 18 '19 at 11:48
  • $\begingroup$ What is the meaning of this As the AOA increases lift of those front wings would increase also and aircraft would want to pitch up more and go out of control? $\endgroup$ Sep 18 '19 at 12:57
  • $\begingroup$ So, when the * trailing edge control surfaces* activated or use? $\endgroup$ Sep 18 '19 at 12:59
  • 4
    $\begingroup$ No @Kolom, the front wings (or canards) are not added to the design to fix a CG problem. They are a positive lift producing surface, the goal of this design is to reduce the size of the main wing, thus reducing drag and making the aircraft more efficient. Also, they do not make the aircraft more unstable in pitch. They are designed so that when AOA is increased, they stall before the main wing. That will prevent the aircraft from entering a deep stall. You really should base your answers on solid knowledge, not opinions and/or guesswork. $\endgroup$
    – Jpe61
    Sep 18 '19 at 13:25
  • 3
    $\begingroup$ You should really do some reading on the P.180 @Kolom since the design features of the plane are well documented. There is no need for spaculation, the facts are readily available for you, should you choose to spare a moment for them. $\endgroup$
    – Jpe61
    Sep 18 '19 at 17:35

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