Teaching weight and balance

[brianjohn]

Alright, I'm trying to take full advantage of the very knowledgable minds on these boards. In prepping for the big ride (no comments from the peanut gallery) next week, I am getting some very mixed signals about the best way to teach W/B to a student pilot. Everyone tells me to keep it very simple. Don't even bring out the WxA=M chart until the absolute very end. I don't want to give a two minute instructional period, so what all should and shouldn't be covered in such a lesson???
In other words, based on my thinking, if I give only the basic stuff, it will only last a minute before I do a sample weight, arm, and moment chart.
So can some of you experienced CFI's give me some good info on a W/B lesson plan that works or has worked for you?
Thanks in advance!

 

[dmspilot00]

"Don't even bring out the WxA=M chart until the absolute very end. "

I thought that part was simple! If you don't explain that, what else is there to explain?

The effect a weight has on the balance point of on object depends on the distance, thats why you have to multiply them. E.G. if you sit closer on a seesaw you have less an effect than if you sit farther ( 1ft * 170lbs < 2ft * 170lbs ).

Explain everything in a way you would want it to be explained to you if you have never learned it before.

 

[midlifeflyer]

I can understand a procedure where the airplane's chart would be last. The general order of presentation would go like:

1. What is weight and balance?
2. The general concept and formula of WXA=M (the old seesaw)
3. The relationship between weight, balance, airplane performance and CG (the seesaw becomes an airplane)
4. The effect of location of aircraft CG within and without the envelope.

Having established the general concepts and the importance to aircraft performance, the obvious questions becomes, How do we figure it out in the airplane? Now we move to the chart.

There's plenty to talk about in this basic stuff. No 3 alone can be subdivided and include discussions of the relationship between CL and CG, downward tail forces, stall speed and recovery effects, definitions of stability, controllability and maneuverability.

The biggest "danger" is to have too much data in your head and a poor way of presenting it to your "audience".

 

[skyking1976]

Try and find someone that flies a Piper Navajo and see if you can copy the w/b form out of their POH. It is w-m-a style but it is laid out in a grid and all you do is fill in the blanks. Maybe you can modify it to fit your airplane? Just my $.02

Skyking

 

[VNugget]

Don't even bring out the WxA=M chart until the absolute very end.

Are you referring to those graphs with a line with a different slope for each station?

If so, yeah, save those for last. They're silly, and IMHO even unnecessary.

Like everyone else said, start off with explaining the basic concept with the see-saw example.

After that, explain W*A=M (WAM - easy mnemonic) and draw the chart simply by putting the fields under their respective part of the equation.

 

[tarp]

BrianJohn

You said "the big ride" - do you mean the CFIA ride that YOU are taking?

If yes, I think someone said KISS rule. Do it. If this is your initial CFI ride, do it by the book. 1, 2, 3. Thank you sir, Done. W&B is not the place to show your creative side to an FAA inspector or examiner.

Do remember this - a perfect reason why an examiner may ask you to pick this subject. To teach a private student you would do all as explained above. But now the examiner says "OK, now how would you teach a commercial student - same subject?" What becomes important? Hopefully in the back of your head you are thinking floor boards and weight shift. Floor boards because in bigger aircraft there are sometimes weight restrictions based on lbs per square foot but in smaller airplanes they simply just list a max weight for a cargo compartment. And then comes weight shift delta problems. Now, there's a subject to glaze the eyes.

PS. When you get to the real world after your CFI ride, you will find that people already "get" most of the W&B problem through their own reading. You may have to explain some charts. I usually find that I get about 10% renegades that want to know why we must do the W&B since the airplane is obviously overbuilt, etc, etc. For these folks, I usually say that I will show them on the next lesson. The next time we show up, I have gone to the copier and copied the first 5 pages of the insurance policy. "See this", I say, "insurance policy for the airplane". They usually take it and examine the first page. Things like Dollar amounts on there. Then, I say "Remember the W&B discussion we had last week? Well one pound over and half an inch out of CG and you can do this" (rip up the policy) That usually sticks with them forever. (PS, I only copy 5 pages cause that's all I can rip - weakling!)

Good luck on your ride.

 

[bobbysamd]

Weight & Balance

Hey, where's your instructor? You are nearing a checkride. Shouldn't he/she be helping you?

At any rate, you should begin by explaining the importance of computing weight and balance - why it is calculated. Then explain how Weight x Arm = Moment. Then go to the teeter-totter analogy - a time-honored way of explaining weight, arm and moment. Of course, the CG is the fulcrum. You want to explain that you want achieve balance on both sides of the CG. At that point you can start some discussion about the pros and cons of aft CG versus forward CG. Keep that part very simple. I don't think that you necessarily have to delve into why with a forward CG it takes so many more foot-pounds more of pressure on the horizontal stabilizer to raise the airplane's nose, etc.

Somewhere in there you need to hammer home the importance of not over-grossing the airplane, etc.

Don't forget about common student errors in computing weight and balance, such as misreading graphs, incorrect arithmetic, etc.

One other point that might help you. How did your instructor teach you weight and balance? Chances are, if he/she taught it to you in a way that you understood, you could use the same explanation for the practical and later for your students.

Hope these points help some more. Shame on your instructor for not providing you with more guidance at the eleventh hour before your practical.

 

[brianjohn]

Thanks for the help. Fortunately, I have time to breath now. I had one lesson and my stage check (not necessary part 61, but needed none the less) cancelled because of these nasty midwest storms this week, so, I bumped the checkride back to the 28th so I would have time to get those lessons in and breath.
bobby-- my instructor has been here trying to do the best he can do, but once in awhile there is something that you just have to have a different perspective on before the light bulb will go on. That is why I seek your wise council, even though you were whooping it up when Mark Jackson made the sliding catch in the back of the endzone in '88!
One other thing I thought of was giving a book to a student and tell them to hold it real close to their chest. Doesn't require too much pressure to hold it, right?
Now extend your arm all the way out. The book suddenly feels heavier and needs more pressure, right? Your arm represents the "arm" in the airplane weight and balance configuration.
Does that make any sense?

 

[midlifeflyer]

One other thing I thought of was giving a book to a student and tell them to hold it real close to their chest. Doesn't require too much pressure to hold it, right?
Now extend your arm all the way out. The book suddenly feels heavier and needs more pressure, right? Your arm represents the "arm" in the airplane weight and balance configuration.
Does that make any sense?

I like it. But as tarp said, you have to watch out for creativity during the CFI oral. Not that these kinds of analogies aren't useful — i think they are — but rather that your particular analogy can leave a particular examiner cold.

For example, I often use a simple skiing analogy to talk about CG and it's effects on stability and controllability. But when I use it, it's with a student who I have experience with and have a good idea that this particular analogy will be helpful to this student's understanding. But unless I know the examiner pretty well or the personality mesh during the test seems just right, I'd leave it in my bag of tricks for another day.

 

[bobbysamd]

Weight & Balance

Thanks for the help . . . . even though you were whooping it up when Mark Jackson made the sliding catch in the back of the endzone in '88 . . . .

Not exactly. Let's try frustration and embarrassment. Dan Reeves did it with mirrors and No. 7 to get to every Super Bowl with the Broncos. But them up against a quality NFC team in those days, and so much for the mirrors. You saw what the Broncos were really all about. Except for Elway and a few others, you had a mediocre football team. Mediocre football teams don't win Super Bowls.

Now, Dan has another No. 7, in Atlanta, but finally a few quality players to help him. Now, we'll see . . . . .

One other thing I thought of was giving a book to a student and tell them to hold it real close to their chest.

After having trained something like fifteen intial CFI students, and having also tried creativity during one of my orals, I must second Midlifeflyer. Go easy on the creativity and stick with the traditional explanations that examiners have heard for years. Creativity is one quick way to dig yourself into a hole. Save the creativity for students whom you cannot reach through traditional explanations.

And, once more, good luck with your practical and let us know how it went.