Why bother with flaps on takeoff?

steingar said:
Now, for those who aren't familiar with Mooneys, there is a down side to takeoff flaps. They have to come out at 105 mph. That's the flap speed on the M20c's. Not a big deal, but something else to do on an already busy time of your flight.
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What is Vy for your plane? On our 201 it’s 88kts, which is 101mph. Yeah, that’s close to 105mph, but you should be pitching for no more than Vy off the runway. In our 201, rotate, pitch for 88, end of useable runway select gear up. Once the gear is up, select flaps up. All the while maintaining 88kts. After that speed up if you want.

And yes, I know, you’re manually pulling the gear and flaps up vs. the electric ones on the 201, but still, you should be trying to maintain Vy.
 
azure said:
He didn't say 105 was the white line, he said it was the maximum speed for takeoff flaps. I assume the white line is lower. That said, I'm surprised that takeoff flaps have such a low limiting speed in a Mooney, though it could be because they recommend more than 10* for takeoff (gathering that from his mention of two notches). In my Cardinal, takeoff flaps are allowed up to 130 kts... but they're only 10* and I usually try to stay well under that when using that first notch of flaps.
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My mooney white line is at 100, and I believe he has the same model.
 
Bill Jennings said:
What is Vy for your plane? On our 201 it’s 88kts, which is 101mph. Yeah, that’s close to 105mph, but you should be pitching for no more than Vy off the runway. In our 201, rotate, pitch for 88, end of useable runway select gear up. Once the gear is up, select flaps up. All the while maintaining 88kts. After that speed up if you want.

And yes, I know, you’re manually pulling the gear and flaps up vs. the electric ones on the 201, but still, you should be trying to maintain Vy.
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Vy in my model is 105. Again, I think he has the same.
 
azure said:
Ah, okay.
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I'm not sure who is right, but realistically it's pretty hard to not start putting flaps in above 100. The manuals only says this:

Flap operating range 63-100 mph
 
Salty said:
I've always considered the white line the limit for max flaps not any flaps.
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That's another one of those read the manual things.

Not all airplanes are the same. Even within the same manufacturer. My Baron had a white arc that was for full flaps only. Per the POH, the airspeed limit for approach flaps was at least 20 kts higher than the white arc.

The Beech 18, on the other hand, the white arc is a limiting speed for any flap deployment. And if you exceed that, you can expect to be stop drilling cracks at the next annual.
 
dmspilot said:
It doesn't in my experience. And it shouldn't make a difference. How and why would it?
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Pay closer attention, it absolutely does. The reason for this is that flap extension changes the airfoil pitching moment. Extending the flaps causes a nose-down pitching moment and retracting them removes that resulting in a relative nose-up pitching moment. Whether you notice it or not is up to you, but it is there.

https://en.wikipedia.org/wiki/Pitching_moment
 
Salty and I have essentially the same aircraft. Vy is 105, which is also flap speed. In my case I launch at Vx (80 mph) so I can get the gear retracted. Faster speeds in the Johnson bar equipped Mooneys can make gear retraction more difficult. Once the gear is sucked up, flaps come up, and I accelerate the aircraft to its cruise climb speed of 120 mph (we Mooney pilots don't like fling slowly). In the midst of all that I back prop and power to 25 squared. Like I said, takeoff is busy. Omitting take off flaps will make it somewhat less so, which is an advantage. Some Mooney pilots don't use talk off flaps, I do.
 
Wow, so Vy and Vfe the same speed, that does make for a more complicated takeoff. And yes, like a cruise climb of 120kts or so.

Some Mooney articles I’ve read do recommend no flap takeoffs when the runway length is more than sufficient. I’ve done it a few times, but mostly follow the POH and use takeoff flaps all the time.
 
Bill Jennings said:
Wow, so Vy and Vfe the same speed, that does make for a more complicated takeoff. And yes, like a cruise climb of 120kts or so.
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Theoretically you can break the aircraft with every takeoff. Realistically I doubt the flaps are that fragile. Nothing else seems is.
 
Bill Jennings said:
Wow, so Vy and Vfe the same speed, that does make for a more complicated takeoff. And yes, like a cruise climb of 120kts or so.

Some Mooney articles I’ve read do recommend no flap takeoffs when the runway length is more than sufficient. I’ve done it a few times, but mostly follow the POH and use takeoff flaps all the time.
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According to my manual Vy (105) is higher than Vfe (100). Depending on how you interpret the manual's one statement on flap speed. "Flap operating range 63-100 mph". If that means no flaps until below 100, that's a problem. If that means "no full flaps until below 100", not as big a deal.
 
Salty said:
According to my manual Vy (105) is higher than Vfe (100). Depending on how you interpret the manual's one statement on flap speed. "Flap operating range 63-100 mph". If that means no flaps until below 100, that's a problem. If that means "no full flaps until below 100", not as big a deal.
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I'm not a Mooney expert, but imo it's hard to interpret that as anything other than no flaps until 100.
 
Kritchlow said:
I'm not a Mooney expert, but imo it's hard to interpret that as anything other than no flaps until 100.
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I agree. I just don't want to. ;)
 
Sounds a little complicated in some of the Mooneys.

Normal takeoff in the 182E is flaps up. 20° recommended for max performance and soft field takeoffs.
 
The 310 is flaps up for normal takeoff. I went out yesterday and practiced short field for a couple and it calls for flaps 15. It does make it pop off the ground a little bit quicker.
 
dmspilot said:
In a low wing extending the flaps will reduce the down load on the tail, causing the nose to go down
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ChiefPilot said:
Extending the flaps causes a nose-down pitching moment and retracting them removes that resulting in a relative nose-up pitching moment.
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Are you trying to agree with me or disagree with me? Because that is exactly what I said. You are the one that needs to pay closer attention.
 
Radar Contact said:
The 310 is flaps up for normal takeoff. I went out yesterday and practiced short field for a couple and it calls for flaps 15. It does make it pop off the ground a little bit quicker.
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It's one of the challenges of light twins. You can take off much shorter with flaps, but the airplane wants to fly well before you get to red line.
 
Flaps does not reduce down load on the tail. Extending flaps effectively increases the curvature of the wing. Increased curvature increasing nose down pitching moment of the wing. This is why symetrical airfoils have no pitching moment.

On high wings, flaps also increases downwash on the tail, increasing downforce for that elevator setting. That force is creater thN that of the pitching moment, so flaps causes nose up on a cessna, vs nose down in a cherokee. Results may vary slightly for certain airplanes.
 
Fearless Tower said:
It's one of the challenges of light twins. You can take off much shorter with flaps, but the airplane wants to fly well before you get to red line.
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Yup. As I'm sure you know there is often a time of vonurability in most airplanes.
Part 135 eliminates most, part 121 eliminates all. Part 91??? Anyone's guess.
 
PilotRPI said:
This is why symetrical airfoils have no pitching moment.
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What are you trying to say? A symmetrical airfoil won't be symmetrical anymore with flaps. Whether the airfoil is symmetrical or not doesn't have to do anything to do with anything.

PilotRPI said:
Flaps does not reduce down load on the tail. Extending flaps effectively increases the curvature of the wing. Increased curvature increasing nose down pitching moment of the wing.

On high wings, flaps also increases downwash on the tail, increasing downforce for that elevator setting. That force is creater thN that of the pitching moment, so flaps causes nose up on a cessna, vs nose down in a cherokee. Results may vary slightly for certain airplanes.
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Of course flaps affect the airflow around the tail, as you stated in your second paragraph. There is an effect in both low wings and high wings. One exception would be a low-wing T-tail. In that case, the change in the center of lift might be noticeable but it's very small.
 
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Symmetrical airfoils have no pitching moment. Im trying to relate to thise interested that curvature of the airfoil creates pitching moment. Flaps on a symetrical airfoil make it no longer symetrical and add curvature, so it would then have a nose down pitching moment. Add flaps to a plane with a symmetrical airfoil and you should have to add downforce to the elevator to counter it.

Center of lift changes have much less of an effect than changes in airfoil pitching moment and can be ignored for these types of consoderations here.
 
Fearless Tower said:
It's one of the challenges of light twins. You can take off much shorter with flaps, but the airplane wants to fly well before you get to red line.
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After lift off, can you just hold it in ground effect until you get to a suitable speed, similar to a soft field takeoff?
 
PilotRPI said:
Symmetrical airfoils have no pitching moment.
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And a cambered airfoil does? So it is always pitching down inflight? That doesn't seem like it would end well. You're not making any sense.

PilotRPI said:
Flaps on a symetrical airfoil make it no longer symetrical and add curvature, so it would then have a nose down pitching moment.
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I'd bet a Cessna with either kind of airfoil will pitch up when you extend the flaps.
 
azure said:
He didn't say 105 was the white line, he said it was the maximum speed for takeoff flaps. I assume the white line is lower. That said, I'm surprised that takeoff flaps have such a low limiting speed in a Mooney, though it could be because they recommend more than 10* for takeoff (gathering that from his mention of two notches). In my Cardinal, takeoff flaps are allowed up to 130 kts... but they're only 10* and I usually try to stay well under that when using that first notch of flaps.
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Max flap speed in my Mooney is 125 mph, call it 108 knots. Max gear down speed is 120 mph, or 105 knots. Manual gear birds are limited to ~89 for gear down, but i dont remember if that's mph or knots.

The way the Owners Manual says, it's not clear if the flap speed is for full or partial flaps. My electric flaps are infintely variable, but there are only three markings on the indicator: Up (0°); Takeoff (15°); and Landing (33°). His description is of his hydraulic flaps, which should be 2 pumps for Takeoff and 4-1/2 or so for Landing.

I use Takeoff flaps only if the field is short, or I'm loaded heavy. I do not fly heavy into or out of short fields . . . .
 
Palmpilot said:
After lift off, can you just hold it in ground effect until you get to a suitable speed, similar to a soft field takeoff?
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You can if the departure area off the end of the runway is open, but not if there are trees, antennas, smokestacks, etc., out there. I was based for 7 years at a field with trees at both ends, with a 300'+ displacement if landing on 8; the preferred runway was 26, taking off over those close, tall trees. But we had 3000' of runway to deal with, I was never less than 200 agl when I reached them, and usually higher.
 
steingar said:
Salty and I have essentially the same aircraft. Vy is 105, which is also flap speed. In my case I launch at Vx (80 mph) so I can get the gear retracted. Faster speeds in the Johnson bar equipped Mooneys can make gear retraction more difficult. Once the gear is sucked up, flaps come up, and I accelerate the aircraft to its cruise climb speed of 120 mph (we Mooney pilots don't like fling slowly). In the midst of all that I back prop and power to 25 squared. Like I said, takeoff is busy. Omitting take off flaps will make it somewhat less so, which is an advantage. Some Mooney pilots don't use talk off flaps, I do.
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Wow. Lots of changes over the years. My 70 C has Vx = 80; Vy = 100 - Altitude; Vfe = 125; Vg = 120, all in mph, and all electric.

I push everything forward, rotate at 75 and trim a little. Then raise gear, usually around treetops. Initial climb at 85; if using flaps, they come up when clear of obstacles. Once clear of everything, I lower the nose to 100, adjust trim and climb happily to cruise altitude with all three levers against the panel.

With my carb, LOP cruise is less than ideal, so I level off, accelerate, set MP and RPM, lean and tweak the trim. It's a whole lot less busy than steiney . . .
 
Hank S said:
You can if the departure area off the end of the runway is open, but not if there are trees, antennas, smokestacks, etc., out there. I was based for 7 years at a field with trees at both ends, with a 300'+ displacement if landing on 8; the preferred runway was 26, taking off over those close, tall trees. But we had 3000' of runway to deal with, I was never less than 200 agl when I reached them, and usually higher.
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If you have to climb at less than the safe single-engine speed because of terrain and obstructions, that's a different issue.
 
Got about 1500 hours in a Mooney 201, and the biggest reason to use take off flap setting In my opinion is, it’s good to form good habits. Specifically if the fan in front quits spinning just after lift off and landing on the same 10,000 ft runway isn’t a option cause it’s behind you or will be soon, it’s good to have some flap out as your going to have enough to do in a short hurry and in all the chaos you might forget to get them out and that 5mph might be the difference between going home or not. Also it will be easier to look ahead with less pitch (at the same speed). Take off flaps below 100 don’t add a ton of drag but give a lot more authority, lift and increase the stall margin.

Same for landing and slower is almost always better. Better for safety (energy), tire wear and I promise your brakes will last longer as the plane really rolls out after touch down on a no flap landing and most pilots and controllers would prefer you to exit the runway as soon as possible and that means using more brake if the flaps arn’t out.

Sent from my iPhone using Tapatalk Pro
 
Fearless Tower said:
It's one of the challenges of light twins. You can take off much shorter with flaps, but the airplane wants to fly well before you get to red line.
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Very true. I refuse to allow it to rotate prior to Vmc + 5. Usually if runway isn't a factor I rotate just before blue line and break ground at blue line.
 
vanman said:
We only have two friends in flying. Altitude is first and speed is second. Our objective should be to get as high as possible as fast as possible without compromising our safety and our equipment (mainly the engine). The first issue is the ground roll. There are two area which slow the airplane down, the drag from the wheels on the ground and the aerodynamic drag of the plane (including the flaps if they are down). There's a lot more drag with the wheels than the plane.
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The last, or maybe the time before last, time this came up, I actually did teh googles and found a NACA (not a typo) paper from like 1940(?) on the effect of flaps on ground roll. There was words and math that came to the conclusion that flaps help shorten ground roll with the advantages stated above. Also, there seemed to be a lot more unimproved runways back then, because the paper also mentioned (iirc) reduced exposure to "debris". Less time on ground, less gravel dings, I guess.
 
Aaronk25 said:
Got about 1500 hours in a Mooney 201, and the biggest reason to use take off flap setting In my opinion is, it’s good to form good habits. Specifically if the fan in front quits spinning just after lift off and landing on the same 10,000 ft runway isn’t a option cause it’s behind you or will be soon, it’s good to have some flap out as your going to have enough to do in a short hurry and in all the chaos you might forget to get them out and that 5mph might be the difference between going home or not. Also it will be easier to look ahead with less pitch (at the same speed). Take off flaps below 100 don’t add a ton of drag but give a lot more authority, lift and increase the stall margin.

Same for landing and slower is almost always better. Better for safety (energy), tire wear and I promise your brakes will last longer as the plane really rolls out after touch down on a no flap landing and most pilots and controllers would prefer you to exit the runway as soon as possible and that means using more brake if the flaps arn’t out.

Sent from my iPhone using Tapatalk Pro
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When the whole "touch and goes are dangerous" thing came up (and when I was still reading mooneyspace), I realized that you could both land and take off with flaps half, so no configuration change needed on the runway to execute a touch and go. That fact was ignored and the whole "you might raise your gear on rollout trying to get ready to take off" thing kept going. Dunno why. Practicing touch and goes has saved me and the plane more than once, so I'm going to keep doing them.
 
I was getting a rental checkout a couple years ago in an Arrow, PA28-200R. The CFI said try this for a short field take off. Flaps up, at some speed I don't remember, rotate and put in the first notch at the same time. Worked pretty good. I did not like taking my hand off the throttle though.
 
Hank S said:
Wow. Lots of changes over the years. My 70 C has Vx = 80; Vy = 100 - Altitude; Vfe = 125; Vg = 120, all in mph, and all electric.

I push everything forward, rotate at 75 and trim a little. Then raise gear, usually around treetops. Initial climb at 85; if using flaps, they come up when clear of obstacles. Once clear of everything, I lower the nose to 100, adjust trim and climb happily to cruise altitude with all three levers against the panel.

With my carb, LOP cruise is less than ideal, so I level off, accelerate, set MP and RPM, lean and tweak the trim. It's a whole lot less busy than steiney . . .
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Mine is about 8 years older and manual everything. I rotate at about 60, take off about 70 (I don't stare at the airspeed while taking off, mind you), and climb out at 80. Gear comes up as soon as I see positive rate, sooner the better. Like I said, if the speed builds the gear becomes very difficult to retract. Most folks flying J-bar Mooneys do similarly. Flaps come out as soon as I can. All that said, most of my flying is in North Central Flatistan. Even when there are trees I'm usually clear of them by the time the gear is up. I might have to change thing around if I'm flying in terrain.
 
luvflyin said:
I was getting a rental checkout a couple years ago in an Arrow, PA28-200R. The CFI said try this for a short field take off. Flaps up, at some speed I don't remember, rotate and put in the first notch at the same time. Worked pretty good. I did not like taking my hand off the throttle though.
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I love how CFIs just like to make up their own techniques. I don’t like making configuration changes on the roll. If only there was a manual he could look at to show you the proper short field technique...
 
jordane93 said:
I love how CFIs just like to make up their own techniques. I don’t like making configuration changes on the roll. If only there was a manual he could look at to show you the proper short field technique...
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Yeah. I don't think that's in there. I've heard of that technique a couple times since then. Probably here somewhere, I dunno. I decided I wasn't going to do it on my own. If I owned one, maybe. It's the takin the hand off the throttle that freaks me out.
 
luvflyin said:
Yeah. I don't think that's in there. I've heard of that technique a couple times since then. Probably here somewhere, I dunno. I decided I wasn't going to do it on my own. If I owned one, maybe. It's the takin the hand off the throttle that freaks me out.
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I’m all for trying new techniques but I’m pretty by the book and usually just default to whatever the POH says.
 
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