Vref

[wadeg]

Curious what others are using for their Vref on final in later models (ie 7 or SS). I go with 1.3x stall speed and that puts me at 58mph. It still isn't as steep of an approach as I had hoped for. I growl a little whenever I fly with my father in his RV-7A and see how incredibly steep he can make his approaches. If I held 60mph at the height he turns final at, I'd put down at the far end of the runway!

Just wondering what other people's Vref is.

[airlina]

I found in my Series 5 (IO-240) that 1.2 Vso works the best for me to eliminate float. For that steep approach you are looking for, an aggressive slip is in order as the flaps on the Kitfox don't add the drag that they do on your Dad"s RV. Once you get proficient with the slips, they become second nature and are a necessity for getting into the obstructed grass strips that I like to fly into. An added bonus is that your visibility significantly increases , so I can see the obstructions that I am dealing with. My home base has 80 foot trees at the end on the north approach, and it is always a riot to get over the trees , kick in an aggressive slip, drop like a rock and land without eating up a bunch of runway that a normal approach would. Practice at altitude first, then start using your new skill on your landings,slowly working to more and more aggressive slips. Have fun, Bruce

[Dave S]

Wadeg,

I also have a series 7, trigear W/912uls/warp tapered tip prop. When I first started flying it - my biggest issue was figuring out how to actually get down to the runway by the time I ran out of pattern.......but it comes to a person.

Everything that has been said is true. KF flaps add lift - no noticeable drag and they do not steepen the approach like cessna flaps do. Steep descents are accomplished with picking a reasonable approach speed and doing the slip thing for a kitfox.

I have settled on 60 MPH indicated for short final - but I never slow down from 65 till after completing the base to final turn. I normally bring the power to idle on downwind a bit past midfield. I don't know what a person would call it - but I also have an "over the threshold target speed" - that is 55 mph - usually within one wingspan of the ground for that - gets me in for the first runway turnoff every time.

Another deal with this has to do with the prop pitch and idle RPM. Meaning the prop can be used to add drag and steepen the approach (OK - I do covet a flight adjustable prop but can't pay for it). The frugal man's option (speaking of a rotax) is to have the throttle stops set back so the prop provides some drag with the throttle reduced below normal static idle on approach but then you have to be careful as you touchdown to crank in a bit of throttle to keep the rotax happy at its minimum idle rpm of 1800. I found that if the throttle stops are set for a ground idle of 1800 RPM - a closed throttle during the glide will yield a RPM of 2300 - doesn't provide much prop drag. By backing off the throttle stops a little - a person can reduce flight idle rpm to less than that - again BE CAREFUL the throttle has to be reset during touchdown to be sure the rpm then does not drop below 1800. Other engines do not have this limitation, of course. I think this issue has been discussed under other threads on this list.

So, power at idle - 60-65 MPH a person can do a very steep approach with a competent slip. Cancel the slip be a 60 - over the threshold at 55 - even with that rather conservative operation - not many other airplanes can roll out as short.

I think a person has to be careful about getting too crazy with extreme reduced speeds on final when the wheels are too far from the grass - at least for most of us of average skill. There are a few deals memorialized in the NTSB files for both approach and departure situations involving insufficient airspeed with too much air under the wheels. The airspeed over the stall speed is your buffer for who knows what wind conditions can crop up.

BTW - if you don't have a copy - the Kitfox company has an excellent book on how to fly these things and optimize such things as your interest in descent rates.

Sincerely,

Dave S
KF7 Trigear
912ULS warp

[Dorsal]

I have found the method outlined by Dave to work well for me.

[wadeg]

Thanks all for the good input. A good discussion. I think the best steepening method is the slip. Visibility is great and you have a quick means of returning to normal should it be necessary without being in a situation where you are relying upon the engine to hold you on the edge of the curve.
Thanks!