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Flaps zero

Mconner7

Well Known Member
Just back from our trip from Tampa Bay to Sedona and back. My flaps have four presets on the G3X. The cruise position is slightly negative but to my surprise, while flying in the mid to upper teens, I got 2-3 knots more speed with flaps at zero.

Our loading was full fuel, the wife and me, and about 100# of stuff.

I went to the negative position during descent.

Mark
 
Interesting and have been meaning to test this to see what speed difference I get. Should be easy enough to test.
 
I was surprised too, the obvious conclusion is the fuselage angle was lower and decreased drag.
 
How do you measure that? Top skin,bottom skin, average of two and do you ref to top of wing skin or to canopy rail? That?s an interesting thing to experiment with. Thanks. Bob
 
How do you measure that? Top skin,bottom skin, average of two and do you ref to top of wing skin or to canopy rail? That?s an interesting thing to experiment with. Thanks. Bob

Bob,
Not sure how to rig flaps as I bought the plane already flying. I am sure it is in the instructions. In a previous life as a Grumman owner, there was a rigging tool that was sat in top of the wing with a protractor that was aft of the trailing edge.

Mark
 
Mark, are you in a RV10? My neighbor who just flew his 10, says the max speed for flaps zero in a 10 is 122kts IAS. Seems strange to me that zero flap would have a speed restriction different from the airplanes VNE.
Bob Bisbee
1/2 RV14A
 
When my flaps are in line with the wing I called that trailing position at 0 degrees. You can find this by pulling a flat edge at the aft part of the wing and adjusting the flap to be inline with that.

-3 degrees up is reflex and the bottom of the flap at this point should be lined up with the bottom of the fuselage.

Full flaps down for me was around 31%. I set this up as full flaps and then I made the halfway mark between full and trailing as half-flaps.
* Keep in mind you have to pull up a bit on the flaps to get the play out and simulate airflow. Nothing violent just a bit of a pull.

This is all programmed in my VPX. I've testing take-off with Reflex, Trailing and half flaps. Obviously the more flaps the faster I get off the runway.

Then in climb I've testing Trailing and Reflex around 125 knots. Don't really notice any difference other than nose position on a 500 fpm climb.

In cruise around 150 knots I've tested trailing and reflex. I don't see any speed difference but my nose just sit down a bit more so maybe with a heavy load I would.

Bob- your neighbor probably decided to put that speed restriction in. I've flown over 122 plenty of times with my wings in the trailing position and nothing has flown off. My landing process is to descend with the flaps in reflex enter downwind about 130 knots, throttle to 40% and when a beam I put the flaps in trailing. Then the typical base/final flap increments.
 
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Mark, are you in a RV10? My neighbor who just flew his 10, says the max speed for flaps zero in a 10 is 122kts IAS. Seems strange to me that zero flap would have a speed restriction different from the airplanes VNE.
Bob Bisbee
1/2 RV14A

Not strange at all. At zero the upward force on the flap is opposed by the little push rod. At full up (-3 deg) the flap is against the aft spar. That said, my 2008 kit is placarded for 122 kias max 0 deg, but I *heard* that that restriction has been removed for newer kits.
 
-3 degrees up is reflex and the bottom of the flap at this point should be lined up with the bottom of the fuselage.

Fully retracted flap position (reflex) is defined on page 44-5 of the plans, where the flap inboard leading edge makes solid contact with the rear spar doubler plate. From what I've seen, the bottom of the flap is slightly above the bottom of the fuselage in this position.

Bob- your neighbor probably decided to put that speed restriction in. I've flown over 122 plenty of times with my wings in the trailing position and nothing has flown off.

The 122 knot limit is not arbitrary. The RV-10 Construction Manual, page 21, lists the flap limit speeds. 140mph (122 knots) for trail, 110 mph (95 knots) for 1/2 flaps, 110 mph (87 knots) for full flaps.
 
Thanks Tim,
Those speeds make sense and are easily kept within. At the mid to upper teens, the indicated speeds are well below this limitation. It is nice to know what flap settings are most efficient.

Mark
 
It is not too surprising that the airfoil works a little bit better at zero (trail) when at high altitude and loaded heavy. The reflex position should give higher speed down low, and at average loading.

BTW, I am the designer of that airfoil.
 
Fully retracted flap position (reflex) is defined on page 44-5 of the plans, where the flap inboard leading edge makes solid contact with the rear spar doubler plate. From what I've seen, the bottom of the flap is slightly above the bottom of the fuselage in this position.

I honestly had issues with that method. I ended up using a digital leveler to get the 3% and you are correct it about 1/16th higher.

The 122 knot limit is not arbitrary. The RV-10 Construction Manual, page 21, lists the flap limit speeds. 140mph (122 knots) for trail, 110 mph (95 knots) for 1/2 flaps, 110 mph (87 knots) for full flaps.

I missed that. I had seen 1/2 and full flap but honestly thought people just assigned random numbers for trailing. At least on my plane it seems to support a much higher number with no flutter or control issues.

Thanks for the info
 
It is not too surprising that the airfoil works a little bit better at zero (trail) when at high altitude and loaded heavy. The reflex position should give higher speed down low, and at average loading.

BTW, I am the designer of that airfoil.

Near gross weight, at what altitude would you expect the flaps zero (trail) to begin increasing the cruise speed.

A guess from the designer could save me an hour or two of testing, because I’m gonna try. :)
 
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It is not too surprising that the airfoil works a little bit better at zero (trail) when at high altitude and loaded heavy. The reflex position should give higher speed down low, and at average loading.

BTW, I am the designer of that airfoil.

Thanks for a great wing. I marvel at how efficient it is at high altitude despite its low aspect ratio.

Mark
 
Flap Speed

According to this post Van's lifted the speed restriction for first notch (-3 to 0)

"I had a conversation yesterday with Vans regarding flap speeds. As most of you know, Vans published Flap speeds for the -10 are as follows:

"FLAP SPEED: On the RV-10, 140 mph statute for “trail” (3º deflection), 110 mph statute for “½ flap” (18ºdeflection), and 100 mph statute for “full flap” (33º deflection)."

According to Vans Tech support, engineering has decided through analysis and/or testing, to eliminate the speed restriction for the 0 degree "in trail" position of the flaps. They had no idea when the documentation would be changed to reflect this new data."
 
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Have others tested with zero-degree flaps above 12,000?

Did anyone (else) find any pitch instability with the AP?
 
It is not too surprising that the airfoil works a little bit better at zero (trail) when at high altitude and loaded heavy. The reflex position should give higher speed down low, and at average loading.

BTW, I am the designer of that airfoil.

I think many of us who have and do fly above 10,000' and with reasonable loads have found this to be true.

Ashley Miller down here uses trail for take off and climb all the time. I rarely do. But it does yield a knot or two in flight up high. Without doubt Steve you designed a good wing profile there. :)

The RV10 is a pretty good mix of all the compromises you find in aviation, the wing is part of the secret sauce. Like the Bonanza, it will be a thing of legend in the years to come.
 
Have others tested with zero-degree flaps above 12,000?

Did anyone (else) find any pitch instability with the AP?

I tried full up and in-trail at 14,000’ (indicated - 16,000’ density alt) but lighter weight (2 adults, some luggage). I was unable to discern any difference in airspeed, although it was not perfectly smooth so one or two kias I probably would have missed.
Autopilot (Trio Pro) worked absolutely perfectly, as usual. I was at a somewhat forward cg so I wouldn’t expect any issue with pitch stability.
 
I've now made the following practice and it's working well.

Take off, 0°.
Cruise climb, flaps to reflex -3°
Cruise -3° to DA of 10-12k then 0° above that. We've noted a change of 1-2kias, so as others mention, within margin of error.
Back to 0° when slowing for an IAP or 2-3k AGL above my destination while on the descent (usually around 110-120kts - I didn't see the restriction previously mentioned)
Half flaps (I think I have them set around 17°) under 100kias. I'm thinking I'll adjust that practice
Full flaps, under 87kias.
 
I tried full up and in-trail at 14,000’ (indicated - 16,000’ density alt) but lighter weight (2 adults, some luggage). I was unable to discern any difference in airspeed, although it was not perfectly smooth so one or two kias I probably would have missed.
Autopilot (Trio Pro) worked absolutely perfectly, as usual. I was at a somewhat forward cg so I wouldn’t expect any issue with pitch stability.

Thanks Bob, my 10 Friend tested and did get the 2-3 kts. Pilot only, and 60# gear in the back for W&B, full fuel on TO. The Garmin G3X AP would sit there then begin an ever increasing pitch oscillation accompanied by altitude error. It must be the AP settings, but were set per Garmin instructions.

I have not analyzed the data, but it could be a trim overshoot issue too.
 
According to this post Van's lifted the speed restriction for first notch (-3 to 0)

"I had a conversation yesterday with Vans regarding flap speeds. As most of you know, Vans published Flap speeds for the -10 are as follows:

"FLAP SPEED: On the RV-10, 140 mph statute for “trail” (3º deflection), 110 mph statute for “½ flap” (18ºdeflection), and 100 mph statute for “full flap” (33º deflection)."

According to Vans Tech support, engineering has decided through analysis and/or testing, to eliminate the speed restriction for the 0 degree "in trail" position of the flaps. They had no idea when the documentation would be changed to reflect this new data."


Does anyone know where the recommended V speeds for the RV-10 are located in the plans?

The "Final flight test" section that I have DOES NOT list anything for the -10...
 
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