Jump to content

Weight and Balance


brendanw
 Share

Recommended Posts

So, I hope I'm starting this thread in a reasonably sensible spot given that W&B is such an integral part of flight preparation and operations. We're in the midst of our first flight preparations, W&B being part of the picture. May I suggest to the folks who run this site that a section titled 'First Flight Preparations' be added to the main page?

 

Anyway, here's what we have ...

 

We weighed our Cozy IV for the first time this past Saturday and all is well. We came in at 1184 - 592 on the right main, 591 on the left main, and 11 (10 lb nose ballast) on the nose. I'm now knee deep in the W&B Excel spreadsheet that I downloaded from the Cozy Builders site. Our CG is at 110 in, which is right about where it should be!!!

 

Questions:

 

1) According to the spreadsheet, a setup with a 210 lb pilot, full fuel and zero nose ballast would be beyond the aft CG limit. Putting 10 lbs of ballast in the nose gets you just fwd of the aft CG limit. Is this generally what everyone else gets?

 

2) If I add a 200 lb co-pilot to the above configuration (10 lb nose ballast), we're fwd of the fwd CG limit, requiring aft ballast. 35 lbs in the "baggage compartment" seems to get us just aft of the fwd CG limit. Again, is this generally what everyone else gets?

 

3) Assuming the one would need to maintain the aircraft in ground-level condition to fill the fuel tanks all the way up, do you normally stand there and hold the nose down while someone fills the tanks? What's the general MO here?

 

Thanks for your input at this most exciting time!!

 

Brendan and Don

Link to comment
Share on other sites

1) According to the spreadsheet, a setup with a 210 lb pilot, full fuel and zero nose ballast would be beyond the aft CG limit. Putting 10 lbs of ballast in the nose gets you just fwd of the aft CG limit. Is this generally what everyone else gets?

That's about right. There's always some variability. My empty CG is at about 112 in. - 110 is somewhat forward, but not completely out of line. You're a bit nose heavy - do you have the battery in the front, rather than on the spar?

 

2) If I add a 200 lb co-pilot to the above configuration (10 lb nose ballast), we're fwd of the fwd CG limit, requiring aft ballast. 35 lbs in the "baggage compartment" seems to get us just aft of the fwd CG limit. Again, is this generally what everyone else gets?

Umm, you're missing the point of the nose ballast. If you put someone heavy in the front passenger seat, you should take OUT the ballast in the nose, not put MORE ballast in the back. I can put 460 lb. in the front seat before reaching the forward CG limit, with NO nose ballast. With your empty CG being a bit further forward, I'd expect something like 420 - 440 lb. for you.

 

Basically, if I fly solo at 150 lb., I have 52 lb. of ballast in the nose to be AT the rear CG limit. If I have someone that weighs more than 105 lb. in the front seat with me, I remove ALL the ballast, and then the CG will also be at the rear limit. As the person gets heavier, the CG will move forward. With me at 150 lb, I could (if they were dense enough to actually fit in the plane) put a 310 lb. person in the co-pilot's seat before reaching the front CG limit. Not going to happen.

 

3) Assuming the one would need to maintain the aircraft in ground-level condition to fill the fuel tanks all the way up...

A generally incorrect assumption.

 

do you normally stand there and hold the nose down while someone fills the tanks? What's the general MO here?

No. If I have 52 lb. of ballast in the nose, the plane will sit level with no problem, and I can fuel it when level. However, with no ballast, I lower the nose 1/4 - 1/3 of the way down after stopping, and BEFORE getting out. This ensures that the plane won't go anywhere after both front-seaters get out of the plane. You can also fill the tanks about 95% of the way, even with the nose on the ground, so with it 1/4 - 1/3 down, I can still get the tanks almost completely full - well within a gallon/side.

 

Unless you're flying immediately, you really don't want the tanks completely full anyway - it'll warm up, expand, and blow some out the vents. You want to leave a little air space.

Link to comment
Share on other sites

You're a bit nose heavy - do you have the battery in the front, rather than on the spar?

The battery is in the rear up on on the spar. The forwardishness (I'm an engineer, i can make up these words) is likely due to the Strong Pitch Trim, electric noselift and the $1000/lb Garmin stack.

 

Umm, you're missing the point of the nose ballast. If you put someone heavy in the front passenger seat, you should take OUT the ballast in the nose, not put MORE ballast in the back.

You're right. I let the spreadsheet so the walking, rather than my brain. No worries, I'm better now!

 

I can put 460 lb. in the front seat before reaching the forward CG limit, with NO nose ballast. With your empty CG being a bit further forward, I'd expect something like 420 - 440 lb. for you.

432 lb appears to be my front seat fwd CG limit with full fuel (no nose ballast this time!). I suppose that as the fuel burns off and the CG moves forward, I'll throw the cell phone, wallet, shoes, pee bottle, etc. into the back seat :)

 

Basically, if I fly solo at 150 lb., I have 52 lb. of ballast in the nose to be AT the rear CG limit. If I have someone that weighs more than 105 lb. in the front seat with me, I remove ALL the ballast, and then the CG will also be at the rear limit. As the person gets heavier, the CG will move forward. With me at 150 lb, I could (if they were dense enough to actually fit in the plane) put a 310 lb. person in the co-pilot's seat before reaching the front CG limit. Not going to happen.

We're in the same ballpark then. With me flying solo at about 200 lbs, it looks like I'll need about 15 lbs of nose ballast to keep just fwd of the aft CG

 

You can also fill the tanks about 95% of the way, even with the nose on the ground, so with it 1/4 - 1/3 down, I can still get the tanks almost completely full - well within a gallon/side.

No kidding?!?!? I guess I'll be crossing that bridge shortly. Having cut the filler holes (twice on the left wing thanks to Don's !@#$* measurements!) and being intimately familiar with their location, it just doesnt seem like you could fill the tanks all the way with the nose down. We'll see

 

You really don't want the tanks completely full anyway - it'll warm up, expand, and blow some out the vents. You want to leave a little air space.

Good point.

 

Thanks for all the info Marc

Link to comment
Share on other sites

  • 1 month later...

the cell phone, wallet, shoes, pee bottle, etc. into the back seat

And WHERE do you find the space for all these items in the front in a Cozy?

 

:)

I live in my own little world! but its OK, they know me here!

Chris Van Hoof, Johannesburg, South Africa operate from FASY (Baragwanath)

Cozy Mk IV, ZU-CZZ, IO-360 (200hp) 70x80 prop

Link to comment
Share on other sites

  • 5 months later...

Ok, it's sort of on W & B...

 

Here I am, having had a wonderful test flight to determine fuel consumption, using a fellow aviator for the navigation & some company. In flight the plane trims at midway and behaves fine.

 

All said & done, I get out my plane and so does the other fellow.

 

At this point my plane is empty in the front and (of course) no nose ballast, navigator walks away and before I can wind the wheel in ... it starts tipping.

 

Do you think I can keep this plane nose down by hand ... not on your nellie, there she tips over backward and lifts me with (I hung on at the pilot side.) (Calculated the C of G empty is about 108.5)

 

Once over, there is no way I can get this plane back down by myself, even hanging on the canard in total (all 200 Lb of my bulk)

 

How does this relate to your experiences?

 

OK, when the other airport buddies came to it was easy, but then so are most things when you have a crowd :-)

 

Regards,

 

Chris Van Hoof

I live in my own little world! but its OK, they know me here!

Chris Van Hoof, Johannesburg, South Africa operate from FASY (Baragwanath)

Cozy Mk IV, ZU-CZZ, IO-360 (200hp) 70x80 prop

Link to comment
Share on other sites

Ok, it's sort of on W & B...

 

Here I am, having had a wonderful test flight to determine fuel consumption, using a fellow aviator for the navigation & some company. In flight the plane trims at midway and behaves fine.

 

All said & done, I get out my plane and so does the other fellow.

 

At this point my plane is empty in the front and (of course) no nose ballast, navigator walks away and before I can wind the wheel in ... it starts tipping.

 

Do you think I can keep this plane nose down by hand ... not on your nellie, there she tips over backward and lifts me with (I hung on at the pilot side.) (Calculated the C of G empty is about 108.5)

 

Once over, there is no way I can get this plane back down by myself, even hanging on the canard in total (all 200 Lb of my bulk)

 

How does this relate to your experiences?

 

OK, when the other airport buddies came to it was easy, but then so are most things when you have a crowd :-)

 

Regards,

 

Chris Van Hoof

hope that did not hurt your prop or wheel pants. yes that is what happens. the pilot should always stand by the as the passengers get out. the passengers don't ever think this can happen. most don't know about the W&B of a cozy. I have seen this happen to a cozy IV when the co pilot who owns a cozy 3, jumped off the side even with the nose gear half retracted. the spring of the gear launched it over backwards as he jumped off.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

Link to comment
Share on other sites

Thanks for the reply,

 

No, this is not the first time :), it's my second at the drome (twice during construction) and my 4th overall.

1 & 2 were during construction while leaning over to grab a tool or moving the ballast.

3rd was while pushing the plane out for its very first flight and the wheel hooked on the hangar rail.

4th was by vigorous winding down of the wheel and having the plane parked slightly nose up - (& not accepting help when it was offered too)

 

the 2 blade prop was level when it happened, so no damage there.

 

Soon I'll be installing wheelpants and a spinner, then the lesson will be more expensive ...!

 

So, you others, try to learn from my experience, that way it's cheaper for you :)

I live in my own little world! but its OK, they know me here!

Chris Van Hoof, Johannesburg, South Africa operate from FASY (Baragwanath)

Cozy Mk IV, ZU-CZZ, IO-360 (200hp) 70x80 prop

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information