Do you find the cg with landing gear up, down or both?

Thanks, Dave Trimmer

I would just balance it with gear down, then for craps and giggles just check the gear up balance. I dont however, think it matters all that much........ not 100% sure but just 98%

Depends on the plane. If the wing centerline is above the fuse center line. Then balance gear down. If the the wing center line is below or the same as the fuse center line. then balance wheel up. I have not seen to many planes that will balance the same both ways. Since this is in the beginners I will assume you are doing a trainer. Wheels down for sure.

David

Where can I find one of these Trainers with retracts???[sm=75_75.gif]

LOL that was my inital thought
I've read before that the diffrence is minute.... If it is that major, I know I would check both ways so I didnt have a nasty surprise when I would drop the wheels....where can I read the facts on this??? never really researched it due to the fact I doubt I will ever own anything with retracts. as they are just something else to fail.[&:]

That has pretty much been my feeling on retracts too, but I just couldn't resist the Warbirds.[&:] I have a new P-51 coming in the mail from Nitro Planes. I guess I better find out the correct answer to this question too as I am going to need it very soon! This will be my first Warbird & of course my first adventure with retracts as well. I hope mine goes better than some of my friends adventures with them have. I already had a look at the manual that comes with the plane because the plane arrived but I had to send it back for a new one because of some damage to the main wing. I didn't see anything saying to balance it one way or the other regarding the wheels up or down. So I will depend on our good friends right here in RCU to take care of me once again with the answer to this question.

It depends on whether the wheels move back when retracted like a spitfire or not.,some planes move forward when retracted. Balance the plane in the position where the wheels, which are quite heavy are in the most rearward position. Tail heavy warplanes don't fly long.

i would think that landing gear that retract back or forward would change the cg a little,gear that retract sideways into the wing,the weight would be the same and does not change down or up,if one wing mounted gear was more off center than the other i guess the lateral balance would be off slightly off.i worked as a crane mechanic all my life and worked closely with riggers,once the load was rigged less a fulcrum type load,the balance never changed.

Remember the wheels on most planes RAKE forward when down even if they retract straight sideways, so balancing with the wheels up is safer. Believe me when I say that most warplanes don't tolerate a rearward CG very well. They stall quickly at low speeds. They are not pattern planes, which usually have straight up and down gear.

my landing gear go straight back (like a p-40,hellcat or corsair).

I'm pretty sure the gear in the P-51 I'm waiting on will retract staright up & down sideways without rotating or moving forward. I will definitely look at them real well & give whatever movement they have consideration when balancing the plane. No need to worry about a tail-heavy Warbird here. I don't do tail-heavy on any kind of planes!! Thanks for all the good info guys. I knew it would be forthcoming.

yeah, i would rather have a really nose heavy plane than a slightly tail heavy one anyday... i know what your saying. looks like an article to write for my site.... look out google!!!

G'day Dave,
Balance with gear up, that is how you will be flying most of the flight, then when you put the wheels down, especially with a war bird that swings the wheels back & up, the balance point will move slightly forward for landing or take off.

I searched and searched for proven info for this topic. I FOUND NOTHING.[:@] so, I would have to agree with allan0899. This is the most plausible info around.

Yes alan's theory sounds like it makes good since to me too. I'm guessing that in the case of my P-51 where the gear just sweep straight in & out from the side the CG should pretty much remain the same up or down. Do you think that is correct alan? Thanks in advance for the info.

I guess I missed the point. I thought he meant inverted or upright to balance. Did not realize this was a retract question.

David

Oh no![X(] I never thought about that. I guess we just automatically thought he was referring to retracts when he asked with the gear up or down. Now I fear we have hi-jacked his thread. Sincere apoligies DaveTrimmer, that was certainly not my intention. Let us know if we misunderstood your original post. I'm really sorry if that is the case.


my landing gear go straight back (like a p-40,hellcat or corsair).

Nevermind, He is talking about retracts. ( I think[sm=confused.gif])

Balance a high wing plane right side up (Gear down). Balance a low wing plane upside down (Gear up). Planes with retracts should always be balaced with the gear up and inverted (low wing) or right side up (high wing).

now i'm confused again

[sm=71_71.gif][sm=72_72.gif][sm=75_75.gif][sm=wink_smile.gif]

Join the club!!

Ok, let's make sure we're all on the same sheet of music then. You are asking if you should balance your plane with the retracts up or down... correct????

Ken

Lol, I was wondering when one of you big strappers was going to show up![sm=50_50.gif]

Hmmm, is a "big strapper" a good thing or a bad thing?????

I've been semi-lurking the last couple of days. I'm playing "hired gun" in another forum this weekend.

So if I understand the question he wants to know if he should balance with the wheels up or down. I think it was said earlier but from what I understand he has retracts that have a fore-aft motion, meaning they fold up to the rear (Dave correct me if this is wrong). If that is the case then you need to understand what happens when you fold the landing gear up. Look at the attached drawing for this. With the landing gear down the main portion of the weight (the wheel) hangs straight down from the wing, but when you retract the gear that large weight shifts further back on the wing. Therefore the CG of the plane should shift backwards. If you balance the plane with the wheels down then the plane will become tail heavy when you lift the gear up, and since you will be doing most of your flying with the wheels up this probably isn't something you want to do. But instead, if you balance with the wheels up the CG of the plane will shift forward when you drop the gear making the plane nose heavy. A nose heave plane is always better to have. Remember the saying "A nose heavy plane flies poorly, a tail heavy plane flies once!"

So to sum all of that up quick and easy, you want to balance your plane with the landing gear up.

Hope this helps

Ken

ken your right and thanks everyone for straightning this all out for me.

Phew!!! Glad that ones over with!!!!!!!