Proposed gross weight increase for RAA registered Kitfox & Skyfox aircraft

[Fox 4]

This article by kitfox designer & manufacturer Dan Denny

 

some time ago states that kitfox airframes are quite ok to carry an extra 300 lbs if you choose to do so,

 

as the Skyfox could be considered a stronger version of the kitfox ,one could assume that an official weight increase to at least 550 kg should be sought from RAA.

 

One could make the point that at the time the skyfoxes were being produced ,they were only certified to 425kg because that was the maximum approved weight at that time ,test data showed that they easily passed all safety testing with plenty of margin

 

 

 

[F10]

Cargo pod a good/cool idea....The Skyfox baggage bay only good for 10KG, not bad... but if you were at a fly in or show, you would probably find people avoiding you after the third day.....

[tillmanr]

Later Kitfox 4s received a weight increase to540kg (1050 to 1200 lbs).

[kasper]

Just saw this thread ...

 

Skyfoxes are factory and would need MARAP to get through any increase ... and given the Skyfoxes have already had issue with the weld on the lower fuselage carry through on the lift strut failing in flight (fortunately the wing did not fold and a bent Skyfox made it to the ground) it would be a very brave Tech Manager who would consider an increase in Skyfox MTOW through MARAP...

 

Kitfoxes are build it yourself ... you can declare any MTOW you wish within the 600kg max allowed under 95.55 provided the claimed MTOW would still be a believable 45knt stall.  You claim the weight and you take the risk of the airframe failing - its EXPERIMENTAL for a reason.

[tillmanr]

The Kitfox 4-1050 and Kitfox4 1200 were specific Max weights when produced by Denney.

 

[facthunter]

I'd be very wary of putting extra load on the original Kitfox and the later Gazelle. The fuselage frames are not identical for strength I understand also. They have a low never exceed speed made more critical by dynamic (or other) load by the characteristics of the undercambered wing..  Nev

[F10]

I think Gazelles would be quite happy at a MAUW of around 550kg. Two blokes around 90kg and you really can’t take much fuel at a MAUW of 520…(basic is around 320). There is an AD out to have another carry through strut bolted on, below the original, after that incident. Apart from an aileron failure, (which had significant contributing factors) the old Gazelles have a pretty good record I think. Yes underwing camber is interesting, I must read up on it. Most positively cambered aerofoils have a nose down (leading edge down)  pitching moment at low angles of attack. At high AoA, it changes to nose up, with the CP moving forward on the cord line. At some point, there is no pitching moment on the wing. That CP position is referred to as the “aerodynamic centre”, upon which the tail plane stability will be designed I understand. Interesting stuff aerodynamics!

[Blueadventures]

On 18/05/2021 at 5:04 PM, kasper said:

Just saw this thread ...

 

Skyfoxes are factory and would need MARAP to get through any increase ... and given the Skyfoxes have already had issue with the weld on the lower fuselage carry through on the lift strut failing in flight (fortunately the wing did not fold and a bent Skyfox made it to the ground) it would be a very brave Tech Manager who would consider an increase in Skyfox MTOW through MARAP...

 

Kitfoxes are build it yourself ... you can declare any MTOW you wish within the 600kg max allowed under 95.55 provided the claimed MTOW would still be a believable 45knt stall.  You claim the weight and you take the risk of the airframe failing - its EXPERIMENTAL for a reason.

Agree re Skyfox's after owning a Ca21 version.  the Gazelles have a larger tube fitted at build time for the wing strut carry through.   I fitted the AD extra carry through tube to my CA21 taildragger.