Observation about takeoff flaps and full aileron deflection

[AJ88V]

Maybe this is common knowledge, but it was pointed out to me by master CFI Lee Fox when I trained with him.

Takeoff flaps in the Mooney ('half flaps') set the wing up for maximum lift.  Less flaps, less lift / more flaps just add drag.

Ever notice that at full deflection your aileron will line up exactly with the takeoff flap setting?  Check it out next time you're setting up for takeoff.  Also a good way to check that your flaps are appropriately set for takeoff before hitting the RWY.   Cheers!

[PT20J]

In the Beaver, we used to check takeoff flap setting by comparing with full aileron deflection because the indicator was often considerably in error. (Apparently, it is difficult to rig correctly - or at least that's the excuse the service department used).

Full aileron deflection for all Mooneys (M20C and later) is 8 deg down.

Takeoff flap deflection for M20C through M20J is 15 deg down which is nearly twice the aileron deflection.

Takeoff flap deflection for the M20K and above is 10 deg down or slightly more than full aileron deflection.

So, flap/aileron alignment depends on the model. Always verify what your CFI tells you (I'm a  CFI, too and I'm wrong more than I care to think about )

[A64Pilot]

5 hours ago, AJ88V said:

Maybe this is common knowledge, but it was pointed out to me by master CFI Lee Fox when I trained with him.

Takeoff flaps in the Mooney ('half flaps') set the wing up for maximum lift.  Less flaps, less lift / more flaps just add drag.

Ever notice that at full deflection your aileron will line up exactly with the takeoff flap setting?  Check it out next time you're setting up for takeoff.  Also a good way to check that your flaps are appropriately set for takeoff before hitting the RWY.   Cheers!

That’s an old bush / Ag pilot belief. It’s predicated in the belief that an Aircraft manufacturer knew what they were doing when they set max deflection of the ailerons.

Idea is they are set to cause the most lift as possible and that more travel adds more drag than lift, drag of course causes adverse yaw and that’s not desirable.

Often with flaps there are three settings, first is mostly lift, second a mix of both increased lift and drag and full is mostly increased drag.

However if there is enough thrust to overcome the additional drag takeoff roll will be reduced with full flaps, there are no absolutes, however if your really heavy first notch, or usually 15 deg will often match max down aileron deflection is best to get a struggling Ag plane off of the runway. Full flap on turbine Thrush aircraft was only 15 deg for this reason, with a turbine you can get drag from the prop so no need in flaps for drag.

Oh, and for Certification at max gross weight an aircraft has to demonstrate capability to go around with full flaps.

But hot day, high altitude etc., maybe not.

On edit, don’t do what your CFI tells you, do what the POH says.

Edited December 12, 2024 by A64Pilot

[shawnd]

Is this video available somewhere for viewing? Would be fascinating to watch.  Perhaps could be uploaded to YouTube after getting permission from the right set of folks.

[shawnd]

Oh man, I agree. Let’s keep bad karma away from flying! 

[Will.iam]

You can buy off karma, just send $100 to MAPA and no karma will be given. In fact maybe good karma given for an extra $100!

[201Mooniac]

Is there still anyone at MAPA to take your money?

[201Mooniac]

58 minutes ago, bluehighwayflyer said:

Oh, They’ll take your money alright. Just mail them a check and find out for yourself.  

I actually tried that for my last renewal, many years ago at this point, and they never cashed the check.

[shawnd]

They cashed mine as well but I never got the awesome membership card. That’s all I really wanted - to be a card carrying Mooney MAPA member!

 

On the flip side it’s sad what happened to MAPA. They were great folks when it was active but life happens. I am an avid reader of the Mooney Flyer and donated to them in hopes of keeping them going. 

[PT20J]

I was out at the hangar today and looked into this. My M20J has the three position flap switch (up, takeoff, full) so the 15 deg takeoff position is quite repeatable and I recently checked it and it is exactly 15 degrees. With the flaps at takeoff, full down aileron deflection appears from the cockpit to be slightly lower at the the trailing edge than the flap trailing edge ( I measured 2.5 deg lower with a digital level). So, how can this be if the ailerons deflect 8 deg and the flaps 15? It's because the hinge line of the ailerons is about 5 inches ahead of the hinge line for the flaps. So, with hydraulic flaps (or electric flaps without the takeoff position on the switch), it is possible to check the takeoff flap position by comparing it to the fully deflected down aileron -- the flap trailing edge should be just a bit higher than the aileron trailing edge, but aligning them is going to be close enough.

What is more curious is why did Mooney change the takeoff setting from 15 degrees to 10 degrees starting with the K?

 

[Will.iam]

12 minutes ago, PT20J said:

I was out at the hangar today and looked into this. My M20J has the three position flap switch (up, takeoff, full) so the 15 deg takeoff position is quite repeatable and I recently checked it and it is exactly 15 degrees. With the flaps at takeoff, full down aileron deflection appears from the cockpit to be slightly lower at the the trailing edge than the flap trailing edge ( I measured 2.5 deg lower with a digital level). So, how can this be if the ailerons deflect 8 deg and the flaps 15? It's because the hinge line of the ailerons is about 5 inches ahead of the hinge line for the flaps. So, with hydraulic flaps (or electric flaps without the takeoff position on the switch), it is possible to check the takeoff flap position by comparing it to the fully deflected down aileron -- the flap trailing edge should be just a bit higher than the aileron trailing edge, but aligning them is going to be close enough.

What is more curious is why did Mooney change the takeoff setting from 15 degrees to 10 degrees starting with the K?

 

Don’t know and my flap switch doesn’t have a detent for takeoff flaps i wish it did. It’s an off setting in the middle. Up goes full flaps up and down is spring loaded to go back to the middle where it is off again. The first time i went around from flaps full i selected the up position and forgot it doesn’t spring back to the middle so it retracted the flap from full to up and i had a whole lot of nose up that i had to put alot of force on the yoke to counter. It was a quick lesson to either momentarily put the switch in the up position and tgen quickly back to middle position to stop them so i could catch up on trim or use partial power and as the trim removes pressure add more power or retract more flaps. Full to about half is way bigger a trim change than 10 degrees to up that is for sure. 

[Hank]

The electric flaps in my C are moved by a spring-loaded switch that returns to center when released. As long as I hold the switch over, the flaps move (until they hit the limit switches, then the motor grinds)--there is no "set and forget," I have to hold it.

Fortunately I can reach the switch with a finger while holding the throttle to idle, whether on final or rolling out on the runway. I don't brake until after the flaps are up, and haven't flat-spotted a tire.

[A64Pilot]

On 12/12/2024 at 8:22 PM, PT20J said:

 

What is more curious is why did Mooney change the takeoff setting from 15 degrees to 10 degrees starting with the K?

 

Piston 1340 Thrush had I think 40 degrees of flap, Thrush flaps are like a Mooney with electric flaps in that they are infinitely adjustable.

Anyway when the Turbine was installed by the Ayres Corp flight testing showed an excessive nose up pitching moment when doing a go-around at light weight so that is where the turbines 15 degree flaps came from.

When they installed the Garrett’s the rudder would lock if you did a stupid excessive slip, so rudder deflection was reduced.

On the K my guess and it is just a guess but mine is that maybe they are just a little more nose heavy and that might cause a little more trim change with flaps?

The Thrush of course has a few STC’s for turbine installation, none of which call for flap travel reduction and I never heard of an accident from it so apparently the average pilot can handle 40 degrees of flap.

Two different test pilots can fly the identical airplane and come up with different opinion on handling qualities, as much as we would like to think it’s purely scientific, but aircraft handling qualities are somewhat subjective, then add in the fact that many test pilots have to find something, they feel that if they don’t it looks like they aren’t doing their jobs, and I learned eventually that if the change they wanted was minor and didn’t hurt aircraft performance to just thank them, make the change, save who knows how much money and get the aircraft Certified months earlier, and possibly I made a friend as I WILL see that FAA check pilot again.

I’m saying that just maybe Mooney did it at the request of the FAA for some reason we will never know, because fighting to not make the change just wasn't worth it.

I promise you the darndest things get changed and you just can’t make sense of it, but as Paul Harvey used to say “and now for the rest of the story”

[A64Pilot]

On 12/12/2024 at 8:43 PM, Will.iam said:

Don’t know and my flap switch doesn’t have a detent for takeoff flaps i wish it did. It’s an off setting in the middle. Up goes full flaps up and down is spring loaded to go back to the middle where it is off again. The first time i went around from flaps full i selected the up position and forgot it doesn’t spring back to the middle so it retracted the flap from full to up and i had a whole lot of nose up that i had to put alot of force on the yoke to counter. It was a quick lesson to either momentarily put the switch in the up position and tgen quickly back to middle position to stop them so i could catch up on trim or use partial power and as the trim removes pressure add more power or retract more flaps. Full to about half is way bigger a trim change than 10 degrees to up that is for sure. 

What causes that excessive pitch attitude is flaps AND excessive up trim, if you don’t trim up so much you won’t have that excessive pitch up.

It’s not just Mooney’s either, my Maule was much worse, the difference was a Maules flaps were manual and you can lower them in an instant, but a Mooney’s take time, plus a C/B could pop. I learned in my Maule to not trim full up for landing, works in my Mooney too.

By the way, as bad as it was for you with I assume by yourself or one other, it’s much worse with people in the back, especially if there is baggage too, because of tge CG of course.

Edited December 15, 2024 by A64Pilot

[Will.iam]

27 minutes ago, A64Pilot said:

What causes that excessive pitch attitude is flaps AND excessive up trim, if you don’t trim up so much you won’t have that excessive pitch up.

It’s not just Mooney’s either, my Maule was much worse, the difference was a Maules flaps were manual and you can lower them in an instant, but a Mooney’s take time, plus a C/B could pop. I learned in my Maule to not trim full up for landing, works in my Mooney too.

By the way, as bad as it was for you with I assume by yourself or one other, it’s much worse with people in the back, especially if there is baggage too, because of tge CG of course.

Actually people in the back make it easier as i don’t have to put in so much nose up and a J FEC are less nose up as well. My K with the turbo and 2 more cylinders out front makes it almost full nose up with flaps by myself. In fact a couple of jugs of water in the baggage compartment makes a world of difference, one of the big reasons i want to go with the MT prop as that’s 11 lbs off the nose and would help greatly in the trim dept. 

[AJ88V]

1 hour ago, A64Pilot said:

What causes that excessive pitch attitude is flaps AND excessive up trim, if you don’t trim up so much you won’t have that excessive pitch up.

I believe deploying flaps moves the center of lift rearward along the cord of the wing, requiring more nose up trim to achieve the desired angle of attack with the balance point. Raising the flaps causes the center of lift to move forward to its normal flight location.  Without further control pressure to hold the nose down, the plane pitches up significantly until the pilot rolls in some nose down trim to rebalance the aircraft around the new center of lift.

[AJ88V]

10 hours ago, A64Pilot said:

What causes that excessive pitch attitude is flaps AND excessive up trim, if you don’t trim up so much you won’t have that excessive pitch up.

I replied previously to this like it was a question, but it was written as a (correct) statement.  We had a thread a few months ago on the Pre-J forum from a new owner concerned about wheelbarrowing on takeoff, and how healthy a tug on the yoke was needed to rotate.  This is exacerbated because many of us fly nose heavy with just front seaters.  To compensate, we (or at least I do) adjust by setting takeoff trim half a block or even a full block high on the indicator so she mostly just flies off the ground.  The problem with this trim setting is that you end with excessive pitch up when you remove the takeoff flaps (as A64 wrote).  Flying with this setup requires a strong forward push on the yoke while simultaneously adding down trim to the plane's new retracted-flap configuration.

Now wheelbarrowing is not a good thing on takeoff, and it's just weird to have to literally pull the airplane off the runway, but that's what the stock trim setting requires in my plane.  It also seems weird to use that much back pressure in a low speed maneuver so close to the ground, but it does avoid the rapid up pitch when retracting flaps, which is another risk-prone, low-speed maneuver close to the ground, arguably a more dangerous moment since you're higher with fewer recovery options.

So in which flight regime do you want to put in that heavy yoke control force, coming off the runway or while retracting flaps?  We all learn to do these things automatically.  I certainly don't suffer rapid pitching up from retracting flaps because I automatically increase yoke forward pressure as the flaps are raised, then start trimming out the pressure.  But is it better to have to pull the airplane off the runway with a more down-trim setting and not have a potential stall inducing event while retracting flaps (exacerbated by transitioning from a high-lift/takeoff flaps condition to a lower-lift/no-flaps condition)?

It's said that being a pilot is a license to learn. What I love about these forums is that you all post ideas that make me think. Thank you.

[Slick Nick]

@AJ88V You're not alone. I run my takeoff trim setting about a half a block high as well. I find my plane usually wants to start flying right around 60 knots, that's about when I let it come up off the runway anyway, initial climb is easy with that trim setting, but yes, I must roll a bunch in when retracting the flaps.

Edited December 15, 2024 by Slick Nick

[PT20J]

Try this on a M20J or earlier…

1. On the ground, set the trim so that the elevator is in trail with the stabilizer. This is the takeoff trim position. Note the position of the trim indicator. It should be within the takeoff band. If not, something needs adjusting.

2. Takeoff and level at 1000’ AGL. Slow to white arc and put the flaps in the takeoff position. Slow to 70 KIAS and set the trim to the position on the indicator you found in step 1. Pitch to 7 degrees and apply full power. The airplane should be approximately in trim. If not, adjust slightly and note the trim indicator position.

Now, if you set the trim indicator to the position determined in step 2, you should rotate for takeoff with perhaps 5 lb. of back pressure and not have unmanageable control pressures when you raise the flaps. If you have electric trim, you can thumb the trim while the flaps are in motion and most of the pitch force will balance out. 

EDIT: In other words, the proper takeoff trim setting should put you in the initial climb pretty much in trim.

Edited December 16, 2024 by PT20J

[0TreeLemur]

On 12/15/2024 at 6:28 AM, AJ88V said:

it's just weird to have to literally pull the airplane off the runway, but that's what the stock trim setting requires in my plane.

I believe it was Mooney test pilot Bill Wheat who wrote (somewhere) to the effect of "The takeoff trim setting requires the pilot to just slightly pull back on the yoke to lift off."   That's the way it was designed.

One could speculate that this is safer, because it requires pilot input to become airborne, which will happen when the pilot determines that the ship has enough forward speed to safely take to the air.   Makes sense, no?

 

[Hank]

17 hours ago, 0TreeLemur said:

I believe it was Mooney test pilot Bill Wheat who wrote (somewhere) to the effect of "The takeoff trim setting requires the pilot to just slightly pull back on the yoke to lift off."   That's the way it was designed.

For my C, the Owners Manual says:

[PT20J]

On 12/12/2024 at 5:22 PM, PT20J said:

What is more curious is why did Mooney change the takeoff setting from 15 degrees to 10 degrees starting with the K?

I asked Bob Kromer and he said that his recollection was that the original M20K test pilot thought that the pitch change with flap retraction might be too much for the average pilot using 15 degrees.

This makes sense. The CG is more forward in the K than the J which should increase the pitching moment as the center of lift moves with retraction. Takeoff flaps don't have much affect on the coefficient of lift: the reduction in stall speed is only about a knot from flaps up for either the J or K. The primary effect would seem to be to create a lower nose attitude. The Mooney flaps have longer span that many comparable designs, and since they affect more of the wing, they have a greater increase in lift coefficient than others -- but only when fully extended.