Fully moveable canard vs. hinged canard

[Tom180]

I'm exploring building a plans built canard aircraft, such as the Cozy Mark IV. I was surprised to see that it uses a fixed canard with a hinged elevator. I noticed the Velocity also uses this system.

Wouldn't a fully movable canard be simpler, cheaper and more reliable?

Does anyone know the trade offs involved?

 

[rb1957]

probably much the same as a conventional H. Stab (with an elevator) and an "all flying" H. Stab (with a pitch trim actuator). all flying (movable) H. Stba. were designed initially to overcome the movement of the CP in transsonice and supersonic flight; they needed more pitch control tahn a conventional elevator would provide.

clearly moving the entire surface means you can provide the same control force (lift) with a smaller input (inclination) hence less drag.

i would think that making an all flying H. Stab (or canard) would be more difficult than a conventional arrangment ... it got to be much easier to design a fixed structure with a movable surface attached, than to design a fixed pivot point and allow the entire surface to move + the actuator to carry the load. it'd also need a pretty "hairy" control system to react quickly to control inputs ... something "easily" done with hydraulic controlled surfaces.

 

[thruthefence]

Pretty much all the little Pipers have an "all flying" horizontal stab. Not many "Transonic" Cherokee 140 issues, I don't think.

Fred Weick ( Ercoupe)and John Thorp (many & various) were the designers

 

[berkshire]

The big problem with all flying tail or canard surfaces is feel.( stick forces per G), there is very little.
The Piper Cherokee has an anti servo tab built in to provide artificial stick feel. Several sailplanes like Schleichers Ka6e and the ASW 15 had springs loading the stick to provide artificial feel and if you were flying the aircraft out of trim you had to be careful not to let go of the stick or bad things happened.
The prototype Concept 70 sailplane had an all flying tail. A pilot flying the aircraft in a competition let go the stick to light a cigarette, while the aircraft was out of trim, the resulting bunt put his head through the canopy. The very next day the factory was working on modifying the production aircraft to stabilizer elevator combinations.
B.E.

 

[Dan320]

Berkshire, I beg to differ;
An all flying surface will float, i.e. weatherwane if you let go of the stick.
That will effectively end all lift produced by the surface.
A canard aircraft will then nose-dive, a conventional airplane may dive or nose up depending on CG position etc.
You will need an atni-servo tab as in the PA28 to negate the weathewaning tendency and couple the surface incidence to the aircraft longitudinal axle.

 

[berkshire]

Dan320 (Aerospace)
You are correct. The problem is in the spring systems used to produce artificial feel. The mass balance of the all flying control also has an influence on pitching.
B.E.

 

[plasgears]

Proceed with caution on your fully variable canard. I witnessed a home builder who changed his elevator to fully variable stabilator. It was a small one seater like the Jeanie Teeny. The first flight was scary even for onlookers. It was PIO in extremus.
He was remarkably calm after he landed; probably feeling relief for having cheated death. He explained the fully variable stabilator; he wanted more elevator, and he got in spades!

Build according to plans.

EAA Tech Counselor

 

[berkshire]

Hi Plasgears,
I am the liaison officer with the EAA.chapter I am in.
B.E.

 

[Tom180]

Thanks to everyone that responded. I currently own and fly a PA28-180, so I'm familiar with a stabilator and I know that the RV-12 recently switched to the stabilator design. As I understand both Piper and Vans chose the stabilator over a stabilizer because of reduce cost and simplicity of manufacture.

Just curious why that hasn't been tried on a Canard design if it's truly a simpler design. As plasgears stated any design changes should be approached most cautiously, especially one to a control system or surface.

 

[plasgears]

Berkshire,
Nice to hear you are assoc with EAA. I recently added Flight Advisor to my duties in the chapter. EAA says that builders who participate in TC and FA have zero accidents. I issue test cards to all those contemplating first flight soon. At most meetings I give brief comments on tech or flight issues. E.G. First flight should include probing for incipient stall at 3000 ft alt in all flap config's. then the pilot can plan a safe 1.3xVs approach for landing.

We are planning a briefing in March for all emergency responders on what to do when they come to a crash site. This includes fuel switch off, ignition off, and how to access occupants. Inverted low wings are a problem especially with sliding canopies. We encourage lift tail and prop up for access.