Official FlightLine RC 2000mm B-24D/J Liberator Thread

[Mike O.]

Has anyone had to change out a flap.servo? Got one that is acting up. How is it wired and is it easy to get at?

[fhhuber]

I call BS! If it's such a no no, then why do so many guys set it up as a mix? Tell ya one thing. If you'd try to turn my Nieuport 17 without first initiating with the rudder and opposite aileron to hold the banking? You'll be picking up sticks!

Jim

You are flying the plane working to keep the nose pointed in direction of travel and wings level or banked an appropriate amount into the turn.

And exactly what you are trying to prevent is the normal result of cross-controlling where it banks one way and points the nose for the opposed turn. Your plane's natural tendency to bank on rudder being excessive with that aircraft.

The mix is done to correct for adverse yaw (when using ailerons and pretty much ignoring rudder) or to correct for the amount of bank induced by use of the rudder. For relatively mild maneuvers this is fine.
For large control deflection, the mix amount appropriate at mild throw won't be right, but modern computer radios can have the mixing done on a curve to deal with that, assuming you never want to really learn to coordinate your controls manually.

Some aircraft need little to no use of rudder to combat adverse yaw when you use differential aileron throw. Some need very little aileron correction for the roll on rudder. Some need significant elevator correction when using rudder.
Knowing how much correction your particular aircraft needs with any given control input is just part of flying.

My Kadet Sr had such extreme adverse yaw (without differential ailerons) that it could not be corrected with extreme use of rudder. Knowing the plane let me get away with demonstrating a bad situation for a long time... overconfidence from repeatedly demonstrating with the bad situation resulted in wiping out the airplane.

Cross controlling can be useful. An airliner that ran out of fuel used it to bleed off speed and altitude for a safe landing. ("Gimli Glider" Air Canada 143) It is also a notoriously unstable condition where the smallest mistake results in a spin.

[Clearblue]

I call BS! If it's such a no no, then why do so many guys set it up as a mix? Tell ya one thing. If you'd try to turn my Nieuport 17 without first initiating with the rudder and opposite aileron to hold the banking? You'll be picking up sticks!

Jim

[rifleman_btx]

^YES!

[Hardway]

Slip happens.......

[rifleman_btx]

Yup that's why I never hold a slip, unless landing in a cross wind. Then I'll hold it as long as i can until right when the mains touch down.

[fhhuber]

Same here, I cross-control on every plane I fly as SOP. not sure I understand why it is a no-no. Would love an explanation.

It has to do with potential for inducing a stall, snap-roll, spin sequence.

I used to play around with demonstrating extreme adverse yaw with a Kadet Sr, modified with barn door ailerons and flaps. 45 deg flaps, 50 deg available up and down elevator, 60 deg available rudder, I could apply full left aileron, full left rudder and do circles to the right.
This condition is EXTREMELY unstable with the aircraft flying pointed appx 40 deg to the line of travel. Just a fraction off on throttle and it would snap right over. (but being a Kadet SR, it recovered in 20 ft)
I trashed the Kadet playing that game 5 ft above the runway to let people see the extreme control throws. Snapped inverted and splattered.

Cross controlling is normally used in side-slips to control bank angle while angling the nose well off to the side vs line of travel. The wing "behind" the fuselage is blanketed by turbulence and highly likely to stall. Its a great way to lose altitude and airspeed at the same time. Its also a great way to put the airplane into a spin if you lose too much airspeed.
Typically a technique used on landing approach, you have ZERO room for recovery if it spins.

These are using LARGE deflections of the controls to create an unstable condition on purpose.

But that is different from moderating small deflection aileron opposed to rudder for the purpose of preventing the rudder rolling the aircraft more than is desired.
There's not much of an issue because you are keeping the nose pointed the direction of travel.

[rifleman_btx]

I always turn with rudder and ailerons. Mostly with rudder and control the angle of bank and turn angle with the ailerons.

[Trobinson99]

I flew for probably a couple of decades before I read someone on a forum saying that cross-controlling was a no-no. In all that time, I found myself naturally cross-controlling all the time, with all kinds of aircraft. I still don't understand what the problem is, as I've not noted any particular problem this causes. It's probably attributable to my old-lady slow flying style...

Same here, I cross-control on every plane I fly as SOP. not sure I understand why it is a no-no. Would love an explanation.

[RickVB]

Regarding the subject of needing to apply opposite aileron in a turn...

In the sailplane world, where high aspect, wide-span wings are being flown at slow speeds while thermalling, there exists a well known unwanted aerodynamic tendency known as the "over-banking tendency". When being turned at a relatively slow speed, the outer wing has a significantly higher airspeed than the inside wing and this results in higher lift on the outside wing, and this tends to cause the wing to want to increase the bank angle - ergo - the over-banking tendency. To correct for this unwanted effect, the pilot must apply reverse aileron to keep the bank angle constant throughout the turn. This results in the pilot needing to "cross-control" where the rudder is applied in one direction and the aileron is applied in the opposite direction. Most power pilots consider cross controls to be a no-no, but for sailplane pilots this is an everyday fact of life. (In a sailplane, the rudder is used for one reason: to maintain a streamlined attitude where the fuselage is aligned with the relative wind. This is the reason for the all-important yaw sting; a piece of yarn taped to the canopy in direct view of the pilot.)

The B-24 Liberator looks a lot like a sailplane with its high aspect wide-span wings. The over-banking tendency may be what is happening with this bird as well. For me, I don't think that applying a mix in the radio is a good idea, because the over-banking tendency varies significantly with airspeed and is most pronounced at slow speeds...

I flew for probably a couple of decades before I read someone on a forum saying that cross-controlling was a no-no. In all that time, I found myself naturally cross-controlling all the time, with all kinds of aircraft. I still don't understand what the problem is, as I've not noted any particular problem this causes. It's probably attributable to my old-lady slow flying style...

[themudduck]

So another month has gone by... no nose gear doors. Hey MRC, should I just give up and scratchbuild?

An idea for the MRC guys - perhaps the LG doors could be provided as a 3D file, that way we can just print our own doors?

[RickVB]

And while I'm at it, Alpha, back in December you started posting photos of the installed 3DP parts with the front turret and cockpit, but you never posted the top or rear turrets or waist gunner positions. Did you ever take photos of those?

[RickVB]

So another month has gone by... no nose gear doors. Hey MRC, should I just give up and scratchbuild?

[Clearblue]

I haven't flown mine yet either, but wanted to have some back up props for when I do get that chance. Motion has been out for a good while. So found and ordered some from rc castle. couple weeks, and I had em. http://www.rc-castle.com/index.php?r...roduct_id=7417

Jim.

[theoldALFER]

Well I have finished detailing my B-24 and waiting for the wind to die down here in sunny SW Florida to get my first flight in.

I do have a question though. My buddy also has the B-24 and, on his first landing, he came in with the left wing slightly down and proceeded to land somewhat on the "heavy" side (dropped it onto the paved runway). Result - one broken prop on the outboard motor. Since I have noticed that Motion RC is out of stock for the second time on props, is the B-24 a "PROP EATER?" Anyone have that issue?

Next, my two cents on the use of Rudder. Simply put, there's a reason aero type engineers put rudders on airplanes ( and It's not to keep their brother-in-law in the hinge manufacturers business in business) - Rudder is used to make a turn coordinated. Any one who has actually had their arse in the seat of an airplane and watched the turn and bank indicator will attest that the rudder keeps the ball in the center while the intrepid airman makes a turn. Same is true for our down sized RC aircraft - the still obey the laws of aerodynamics.

I think I'll stick my head outside and see if the winds are under 25 gusting to forty...

[ridgerunner]

Regarding the subject of needing to apply opposite aileron in a turn...

In the sailplane world, where high aspect, wide-span wings are being flown at slow speeds while thermalling, there exists a well known unwanted aerodynamic tendency known as the "over-banking tendency". When being turned at a relatively slow speed, the outer wing has a significantly higher airspeed than the inside wing and this results in higher lift on the outside wing, and this tends to cause the wing to want to increase the bank angle - ergo - the over-banking tendency. To correct for this unwanted effect, the pilot must apply reverse aileron to keep the bank angle constant throughout the turn. This results in the pilot needing to "cross-control" where the rudder is applied in one direction and the aileron is applied in the opposite direction. Most power pilots consider cross controls to be a no-no, but for sailplane pilots this is an everyday fact of life. (In a sailplane, the rudder is used for one reason: to maintain a streamlined attitude where the fuselage is aligned with the relative wind. This is the reason for the all-important yaw sting; a piece of yarn taped to the canopy in direct view of the pilot.)

The B-24 Liberator looks a lot like a sailplane with its high aspect wide-span wings. The over-banking tendency may be what is happening with this bird as well. For me, I don't think that applying a mix in the radio is a good idea, because the over-banking tendency varies significantly with airspeed and is most pronounced at slow speeds.

Note that I still need to finish assembly on my Lib and get out there and actually fly it! Spring has Sprung! (although we got snowed on last night here in Salt Lake City)

[Clearblue]

Hugh, don't get me wrong! I do use mixes.... And If it makes your life easier? Then by all means go for it. Different strokes brother. I just prefer do that particular mix with my fingers!

Jim.

[Hugh Wiedman]

Hugh you pretty much said it. Keeping the wing somewhat flat as you start giving rudder, add in opposite aileron so it doesn't tuck in if you will. As for a mix? I typically only mix flap to elevator, Or rudder to steering like on my A 10. Mixing your rudder to aileron would be easy enough if that's what you want? I prefer just to fly it. But understand why one would want to. As for the mix? Just start out 5% to 8% aileron. And maybe have it like you have your gain, on a switch so you can work up to what "feel" you are looking for.

Jim.

Jim, I think you're right on about just fly it. What's the point if I set up everything for auto pilot, might as well go to the beach. Guess I just had a brain freeze moment trying to get it to fly itself.

[Hugh Wiedman]

Hey Hugh, I know that field. You fly at Markham. Nice field!!

Sky Wolf,

Yes, Markham is a great field and the group that flies there are all good guys and gals. Not everyone who uses the field is a member of our club, Markham Park Pilots Association (MPPA), but nonetheless, we all stick together. We also have a group of large jet guys that have some amazing inventory (some of those $25,000 jobs), all involved with our resident jet expert, Franco of House of Power. There is usually at least a half dozen big jets out every day, and that's when us "puny" electric pilots sit back, watch and be amazed.

[Clearblue]

If you’re taking off in much of a crosswind with my Neiuport, you’d better be on the ailerons. Before the wind picks up wing because it’s changing directions faster than you can think about what input you need!