Wing profile of Ho 229

[spicmart]

What can be said of the wing profile of the Ho 229?

 

[ThomasP]

Conventional (non-laminar flow) 14% T/C at about 1/3 the distance from the centerline, to 8% at the tip. Between the 14% sections the airfoil of the wing and fuselage T/C gradually increased to 16%. There was a built-in twist/wash-out. The wing outboard of the engines was of wooden construction, the wingtips were metal. The center lifting body was a steel tube frame with metal and wood formers, with wood skinning for the most part.

I ran across a report on the Ho 229 a number of years ago - I think it was a NACA report but am not sure, and am also not sure what designator they used for the airframe. It described the wing in detail (including the theoretical drag characteristics) and gave the approximate NACA equivalent - I think they compared it to the NACA 2414 series but again I do not remember for sure.

 

[spicmart]

Can you estimate what benefits or drawbacks a laminar profile would have contributed to the design?
Or why the eventual profile had been chosen?

 

[ThomasP]

I have read, in a book about the Ho 229, that the airfoil choice was made because of the wooden wings and the difficulty of keeping laminar flow in service. I do not know if this is accurate or not, but I suspect not, as from an engineering & manufacturing viewpoint I do not see why they would have thought it was more difficult with wooden wings than metal (if that is what was meant, but maybe they were referring to maintenance issues?). From my viewpoint I suspect that they actually just kept it simple since the 34°-35° swept wing would allow the aircraft to reach its critical Mach number of ~M.85 without getting fancy.

The NACA 2414 airfoil has a critical Mach number of M.8-M.85 when combined with the sweep angle, so it should have done the job just fine.

 

[Simon Thomas]

Appears from the report copying the Mustang section for the root aerofoil was not a success. The Horten IX was developed into the Go 229.

 

[Aeroweanie]

I figured it out from this drawing. The airfoil is a AVA 0 0 12.598-2 28/.55 thickness form added to camber from a NACA 1.1151R2 12.598. The main difference between the resulting airfoil and the NACA 1.1151R2 12.598 is that the trailing edge angle is reduced significantly.

 

[Bretoal2]

In a taii less plane, the airfoil must be a Double curvature one (i.e. where centerline has a double curvature).

Otherwise, no stability.

So, all "common" profiles have to be modified to get the rear curvature.

 

[Aeroweanie]

In a taii less plane, the airfoil must be a Double curvature one (i.e. where centerline has a double curvature).

Otherwise, no stability.

So, all "common" profiles have to be modified to get the rear curvature.

Pitch stability is dependent on the rate of change of pitching moment with lift, not the actual value of the pitching moment.

The pitching moment requirement for an airfoil for a flying wing is that it be zero or slightly positive. It it isn't, negative elevator deflection is required to get trim. This results in the reflexed camber line you refer to. The NACA 1R2 and 2R2 families of airfoils have such a reflexed camber line.

 

[Aeroweanie]

In a taii less plane, the airfoil must be a Double curvature one (i.e. where centerline has a double curvature).

Otherwise, no stability.

So, all "common" profiles have to be modified to get the rear curvature.

Pitch stability is dependent on the rate of change of pitching moment with lift, not the actual value of the pitching moment.

The pitching moment requirement for an airfoil for a flying wing is that it be zero or slightly positive. It it isn't, negative elevator deflection is required to get trim. This results in the reflexed camber line you refer to. The NACA 1R2 and 2R2 families of airfoils have such a reflexed camber line.

 

[Bretoal2]

Pitch stability is dependent on the rate of change of pitching moment with lift, not the actual value of the pitching moment.

The pitching moment requirement for an airfoil for a flying wing is that it be zero or slightly positive. It it isn't, negative elevator deflection is required to get trim. This results in the reflexed camber line you refer to. The NACA 1R2 and 2R2 families of airfoils have such a reflexed camber line.

Elevator? Which one? We're talking about tailless aircraft, so aircraft that have no control surfaces other than those on the main wing.

 

[Aeroweanie]

Elevator? Which one? We're talking about tailless aircraft, so aircraft that have no control surfaces other than those on the main wing.

By "elevator" I mean the pitch axis control surface.

 

[Bretoal2]

By "elevator" I mean the pitch axis control surface.

Yes, I guessed that.
But when we talk about the wing profile, we're talking about the "perfect" theoretical one, the one that isn't distorted by the action of the control surfaces or flaps. And this one must be a double-curved profile ; therefore, it can't correspond to the single-curved (or uncurved...) profiles of the standard range used for main wing' of aircrafts with a true tail.