10 deg. Of flaps in a 6 /6A for take off and for short field take off. How ( for us dummies) do you determine 10 deg. ?
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10 deg. of flaps, take off and short field. How (for us dummies) do you determine 10 deg. ?
- Thread starter firemanken
- Start date
You can also measure the flap angle and apply tape, paint pen, or permanant marker to the flap to show when the leading edge of the flap extends past the trailing edge of the wing. That'll give you a visual reference.
Just for another data point, I had Fast Signs make up a black vinyl hyphen that I affixed to the left side flap near the aileron. I think it's about 1/2" wide by 1" long. In my case, it reveals itself at half flaps (20 degrees) so I can visually confirm at a quick glance the flap is where I think it is. You could do the same for 10 or 15 degrees. The one thousand one, one thousand two count--or one Mississippi, two Mississippi--should get you pretty close.
My flaps have stripes (as they become exposed from the trailing edge of the wing), 3" or so long, painted at 0, 10, 20 and 30 degrees. That works great during the day.
For night ops, I made a table in Excel showing how many seconds it took to go from 0 to 10, 10 to 20, 30 to 10, 20 to 10, 20 to 0 and 10 to 0. No need for x to 30 or y to reflex, as those are hard stops. If memory serves, I did the timing measurements three times for each interval--very consistent.
You can also realize that there’s almost no advantage to using flaps for takeoff on an RV…and you easily may get distracted and overspeed the flaps by failing to retract them in time, given how fast we accelerate. Only if it’s really muddy and soft, do I use flaps…and consider than a special circumstance…
If one has VPX you can use the "reflex" position as -10% flaps regardless, if you have a 10 or 14 wing. VPX gives one a CAS warning if overspeed but if one consistently uses 10 degrees for take-off it pretty intuitive to bump the flaps up before one overspeed's it. If I lose my engine at 200 ft at least, I've got some flaps in to fly it to the crash. 
This is what I did (the sharpie on the flap method), but also use the one one-thousand, two...method as well.
Yeah. It ain't rocket science. 12 degrees, 18 degrees? The difference doesn't matter enough to worry about.
I can agree with causing problems if you forget to retract the flaps. However, if you treat it as a standard operating procedure then you should be consistent enough to make it routine. I had only one experience early after first flight. That was enough for me to ingrain it in my standard operating procedure to make it a permanent part of every takeoff.
On the other hand, I disagree with your comment about “no advantage to using flaps for takeoff on an RV”. I have used flaps on just about every takeoff for the past 17 years flying my RV. In my initial testing I tested takeoffs with flaps and without. I also do some no flap landings and no flaps takeoffs for proficiency. There is a noticeable difference on my 9A with 180 hp engine and fixed pitch prop when taking off with 10-15 deg of flaps vs no flaps. If the best lift to drag ratio is basically at 10 deg of flaps for most aircraft why would an RV be different? When taking off don’t we always want the most lift we can generate? We want the plane flying as quickly as possible.
Measure the flap deflection and mark the position with tapr so you can see it when sitting inside your cockpit. Other people have programmed the EFIS but you need a flap position sensor which is difficult to install with an already built airplane. Even when it's programmed into my EFIS, I just glanced outside and know the deflection by looking at the tape.
I use flaps on EVERY take-off. I never use 10 degrees for take-off simply because it's not the optimal flap angle for a short take-off in the RV-6. I do not agree with Justa6 (post #8) that there is no advatange to using flaps on take-off - it's well-proven that the advantages are not only a shorter take-off roll but also that the tail comes up faster giving you better forward visibility for longer.
I use 20 degrees because I was able to prove beyond doubt that this provided the shortest take-off roll by having somebody physically measuring the distance on the ground. I have electric flaps and each bump of the flap switch cycles me through 10, 20, 30 and 40 flaps. You might find that somewhere between20 and 30 degrees is the sweet spot, but both 10 degrees and 40 degrees will give you a longer ground roll than somewhere closer to 20 degrees.
Here are the distances I previously posted:
0 deg 182 m = 597 ft
10 deg 165 m = 541 ft
20 deg 140 m = 459 ft
30 deg 140 m = 459 ft (Yes, it was about the same distance as 20 degrees but keep in mind I have 180 HP and not all RV-6's do.)
40 deg 167 m = 548 ft
So why would you not want to get airborne 138 feet shorter, ever?
As for indication of flap angle, lots of good suggestions here, although as previously posted elsewhere I use Kilroy. He works great.
I use 20 degrees because I was able to prove beyond doubt that this provided the shortest take-off roll by having somebody physically measuring the distance on the ground. I have electric flaps and each bump of the flap switch cycles me through 10, 20, 30 and 40 flaps. You might find that somewhere between20 and 30 degrees is the sweet spot, but both 10 degrees and 40 degrees will give you a longer ground roll than somewhere closer to 20 degrees.
Here are the distances I previously posted:
0 deg 182 m = 597 ft
10 deg 165 m = 541 ft
20 deg 140 m = 459 ft
30 deg 140 m = 459 ft (Yes, it was about the same distance as 20 degrees but keep in mind I have 180 HP and not all RV-6's do.)
40 deg 167 m = 548 ft
So why would you not want to get airborne 138 feet shorter, ever?
As for indication of flap angle, lots of good suggestions here, although as previously posted elsewhere I use Kilroy. He works great.
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Have you ever wondered why the STOL contest guys yank their flaps on at the same moment they rotate, rather than setting them prior to the takeoff run?
The reason is that the drag from the flaps, has to be overcome with thrust…so while you kinda self answered the issue…Yes…it is “easier” to pop the tail up with flaps, the tail will come up almost immediately by pushing further forward on the stick…and all you have to do to get off short is keep the tail low.
Getting off short and great visibility, don’t necessarily go hand in hand.
As for shortest roll…all you are doing by putting 20 degrees of flap, is modify the angle of attack, while adding drag to your takeoff run. I have a rolling wheel for measuring and I’ve done it many times…the shortest distance I get off the ground with 10 gallons in each tank and me…at 600’msl and a 60 degree day…is within thirty feet typically over ten takeoffs…if you measure them you will find sometimes it’s flaps…sometimes no flaps..technique however is very different. You push a lot more earlier and you pull a lot more earlier without flaps…the flaps allow you to be slower and less forceful with the elevator and allow for a lazier rotation.
And to do it right…you have to stop each time and add a bit more gas…to make up for what you used last circuit.
But I haven’t seen them to shorten the takeoff distance. The increased lift, is offset by the increased drag, taking more thrust to overcome the effects…and increasing the time, hence distance.
From my perspective it goes against the grain of simplifying administrative duties at a critical phase of flight. And I don’t buy. For second that doing it as part of your normal procedure makes it better. And as an aside….a constant speed prop is blowing a heck of a lot of air past those inboard sections of flaps…while the relative wind from the airspeed indicator might not exceed the flap speed…the actuator and connecting rods and inboard three feet sure are, so at a minimum, you’re exceeding flap speed on the inboard connections, every time you do it.
Hard to find the good part in this practice when it’s fully considered.
The reason is that the drag from the flaps, has to be overcome with thrust…so while you kinda self answered the issue…Yes…it is “easier” to pop the tail up with flaps, the tail will come up almost immediately by pushing further forward on the stick…and all you have to do to get off short is keep the tail low.
Getting off short and great visibility, don’t necessarily go hand in hand.
As for shortest roll…all you are doing by putting 20 degrees of flap, is modify the angle of attack, while adding drag to your takeoff run. I have a rolling wheel for measuring and I’ve done it many times…the shortest distance I get off the ground with 10 gallons in each tank and me…at 600’msl and a 60 degree day…is within thirty feet typically over ten takeoffs…if you measure them you will find sometimes it’s flaps…sometimes no flaps..technique however is very different. You push a lot more earlier and you pull a lot more earlier without flaps…the flaps allow you to be slower and less forceful with the elevator and allow for a lazier rotation.
And to do it right…you have to stop each time and add a bit more gas…to make up for what you used last circuit.
But I haven’t seen them to shorten the takeoff distance. The increased lift, is offset by the increased drag, taking more thrust to overcome the effects…and increasing the time, hence distance.
From my perspective it goes against the grain of simplifying administrative duties at a critical phase of flight. And I don’t buy. For second that doing it as part of your normal procedure makes it better. And as an aside….a constant speed prop is blowing a heck of a lot of air past those inboard sections of flaps…while the relative wind from the airspeed indicator might not exceed the flap speed…the actuator and connecting rods and inboard three feet sure are, so at a minimum, you’re exceeding flap speed on the inboard connections, every time you do it.
Hard to find the good part in this practice when it’s fully considered.
I am aware this post was directed towards Mike’s statement but in reference to your comment about flaps gemerating more drag, well, that amount of drag generated is a dynamic issue. In my post I mentioned my purpose for using flaps is to take off with the “best lift to drag ratio (L/D)”. L/D will give the highest amount of lift you can achieve. You may have less drag with retracted flaps but you will not have the highest level of lift. Drag during take off is not the deciding factor. Lift is however! It is always a compromise. During the take off phase I choose to give up some drag penalty momentarily in order to achieve the maximum amount of lift I can. At take off LIFT is the most important thing to achieve! I want my plane configured to achieve the most of it I can until I leave the surface.
Live Long and Prosper!
Yeah , my RV9 definitely has an advantage with 10 deg flaps in getting out of my 2000 ft turf. Its a 160hp FP but with 10 deg the tail will come off the ground in the first 20 ft of full throttle op of the TO roll. That makes the acceleration advance quickly and you're up and way before the 500 ft taxiway intersection. I always use 10 deg on a grass field TO for that reason ( to minimize tail wheel roll)
To the original post question: use your phones " incline O Meter" and mark on the flaps where 10 deg is and your set to go.
Stall speeds are noticeably different between 0-18 flap in my rv-10 (As much as 12 knots) not so much in my -7.
So all takeoffs on the-10 I’ll use flap for safety in case of an engine out. On the -7 I might not use flap if I’m on a long runway.
Not all rv’s have the same wing and stall characteristics.
Regards Peter
So all takeoffs on the-10 I’ll use flap for safety in case of an engine out. On the -7 I might not use flap if I’m on a long runway.
Not all rv’s have the same wing and stall characteristics.
Regards Peter
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IMHO, Not one of you correctly answered the question of how do you determine 10 degrees. It is measured. I used a digital protractor.
Everyone answered how they set the flaps to 10 degrees such as tape, marks, and counting so 10 degrees can be repeatable OR the merits of using or not using flaps for take off. Not how 10 degrees was determined.
If the question was how do you set the flaps for 10 degrees, then the answers would be correct.
Everyone answered how they set the flaps to 10 degrees such as tape, marks, and counting so 10 degrees can be repeatable OR the merits of using or not using flaps for take off. Not how 10 degrees was determined.
If the question was how do you set the flaps for 10 degrees, then the answers would be correct.
Do you think you are generating more lift at the moment of takeoff with using flaps?
What you are doing is generating the exact same coefficient of lift at the point of liftoff, in either configuration…while adding drag coefficient, which has to be undone later…and overcome with thrust. Since you can’t add more thrust…you are hindering acceleration, with drag.
With no flaps, you generate the exact same coefficient of lift at a higher angle of attack, which is then immediately reduced and acceleration rules the day.
To really see this demonstrated, take an observer and time both methods to 1,000feet and report back which one wins every time.
then for real…like I’ve outlined go measure which takeoff roll is shortest. With correct technique, no flaps is shortest.
You are saying the OP did not think about using a protractor to measure an angle and that he needed someone on this thread to tell him protractors measure angles?IMHO, Not one of you correctly answered the question of how do you determine 10 degrees. It is measured. I used a digital protractor.
Everyone answered how they set the flaps to 10 degrees such as tape, marks, and counting so 10 degrees can be repeatable OR the merits of using or not using flaps for take off. Not how 10 degrees was determined.
If the question was how do you set the flaps for 10 degrees, then the answers would be correct.
My original post was explaining how I determine measuring 10 degrees while flying and in the airplane (without a protractor).
skylor
Well Known Member
Well many of the canard guys are
I would say that argument is invalid since, with optimum flap, "the moment of takeoff" happens at a lower airspeed since flaps increase the effective angle of attack.
I fly a STOL capable aircraft, not an RV. Almost all my takeoffs start with 10 flap, pull about 30 at rotation, back to 10 for the initial climb out. This is only possible with manual flaps but it gives a significant reduction in takeoff ground roll if timed correctly.
Pretty much every certified aircraft POH that I've seen shows the shortest take off roll is achieved with flaps. Wonder what technique you know that Cessna, Piper, don't?
I agree
Bob, I appreciate the comment…any airplane with manual flaps can be yanked off the ground a bit shorter with a good yank of the flaps at the moment of rotation.
Electric flaps preclude that.
The point was asking about marking 10 degrees of flaps for takeoff…and my comment was that they make almost no difference and are one more administrative duty to attend to and 10 degrees make virtually no difference to takeoff distance,
20 degrees makes the slightest distance if you’re very agressive which is how Cessna also posts their number.
20 does come off about 20 feet shorter than no flaps, at the same weight. But from testing with a rolling wheel 10 doesn’t.
My point was simply why add the distraction, at a critical time, when it offers so little for normal operations.
You can thank Apple’s autocorrect for that one.
Where is Thread Drift when you need him! 
Add to that Cirrus and Pipestrel POH use flaps on take-off. So why not Vans RV's? (It's one less thing to do if you lose power at 300 ft)
Yep. Good point. Plan for the crash configuration
