Flaps zero

Mconner7 · #1 05-01-2019, 07:45 AM

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

Bavafa · #2 05-01-2019, 09:26 AM

Interesting and have been meaning to test this to see what speed difference I get. Should be easy enough to test.

rdrcrmatt · #3 05-01-2019, 10:45 AM

I'd really like to see more data on this. Such as measured flap position (in degrees).

Mconner7 · #4 05-01-2019, 08:55 PM

I was surprised too, the obvious conclusion is the fuselage angle was lower and decreased drag.

Robertc · #5 05-01-2019, 09:17 PM

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

Mconner7 · #6 05-02-2019, 03:49 PM

Quote:

Originally Posted by Robertc

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

bizpilot · #7 05-02-2019, 05:12 PM

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

AviatorJ · #8 05-02-2019, 05:29 PM

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.

BobTurner · #9 05-02-2019, 11:53 PM

Quote:

Originally Posted by bizpilot

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.

Tim Lewis · #10 05-05-2019, 06:14 PM

Quote:

Originally Posted by AviatorJ

-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.

Quote:

Originally Posted by AviatorJ

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.