Is a Marginally Stable Airplane Safe?

[Imtheking]

What is marginal stable airplane?

 

[D H]

What do you think? This looks like homework, and we do not do your homework for you at this site.

 

[Imtheking]

I searched many places but I can't get the meaning of it. Please If you know give me the answer. Please.

 

[gutemine]

A wild guess is that you are facing a poor translation of the German term 'grenzstabil' which means on the border of beeing stable - which is typically when the lift of the wings are only matching the weight of the plane, or it could be the point of minimal speed or maximal upward pointing angle before stalling, etc.

Just a hint on such language problems - try to search the technical term in your local language Wikipedia. If it is what you are looking for you could be lucky and find the article already translated in the English Wiki with the correct technical wording instead of doing strange Google like translations.

But I could be completely wrong also ...

gutemine

 

[D H]

Or he could just search for "marginal stability" ...

 

[Cyrus]

A wild guess is that you are facing a poor translation of the German term 'grenzstabil' which means on the border of beeing stable - which is typically when the lift of the wings are only matching the weight of the plane, or it could be the point of minimal speed or maximal upward pointing angle before stalling, etc.

Just a hint on such language problems - try to search the technical term in your local language Wikipedia. If it is what you are looking for you could be lucky and find the article already translated in the English Wiki with the correct technical wording instead of doing strange Google like translations.

But I could be completely wrong also ...

gutemine

Why do you offer an answer if you don't know what you're talking about? Do you think this is helpful to the OP??

 

[Danger]

The only times that I've heard the term were in reference to modern warcraft, whose manoeuvrability is so high that computers must be used to control them. The more stability a plane has, the less agility.

 

[D H]

Let's not help too much here. (So far, OK.) This looks very much like a homework problem, so we should not be giving out answers until the OP shows some work.

 

[Danger]

Sorry, D H. I figured that a basic definition would be okay so long are there were no technical details. (Actually, I'm not even sure that it's a proper one in the context of the question. )

 

[D H]

No problem, Danger. I guess I'm getting a bit jaded by some of the "why should I do any work when I can get the answer for free by hosing the internet with my question" questions. This post, to me, has that look and feel; that a google search yields several hits where someone has asked this very question adds to that feeing.

 

[Danger]

Quite understandable. I was unaware of that background material.

 

[xstarlogic]

I hope this might help:
www.aoe.vt.edu/~cdhall/courses/aoe2104/AircraftFlight.pdf[/URL]

But please don't post homework question here...

 

[gutemine]

Why do you offer an answer if you don't know what you're talking about? Do you think this is helpful to the OP??

Because I looked at the only other post he had so far which was about the shallowest angle of glide in aircraft.

Asuming that both questions could be related and maybe caused by a translation problem ist not such a bad suggestion - as English is not my mother language either I have a little bit experience in this area. But as I already said - I could be totally wrong also.

OPs then can comment and then the answering is getting much easier.

gutemine

 

[Cyrus]

Because I looked at the only other post he had so far which was about the shallowest angle of glide in aircraft.

Asuming that both questions could be related and maybe caused by a translation problem ist not such a bad suggestion - as English is not my mother language either I have a little bit experience in this area. But as I already said - I could be totally wrong also.

OPs then can comment and then the answering is getting much easier.

gutemine

Well, you were wrong. No offense, but I think you should take down your 'answer'.

 

[gutemine]

Doubt is not a pleasant condition, but certainty is absurd.

— Voltaire

I think he is now already sufficiently warned and when I edit it the quotes would be even more confusing for him.

 

[Imtheking]

I found the Stability Margin which is the "Distance between the Center of gravity and the Neutral point of airplae". But don't understand how this helps the stability...

 

[Cyrus]

I found the Stability Margin which is the "Distance between the Center of gravity and the Neutral point of airplae". But don't understand how this helps the stability...

Good. Now find out what the Neutral point means, and it will make sense.

 

[Cyrus]

Doubt is not a pleasant condition, but certainty is absurd.

— Voltaire

I like this quote, I'm going to make it a point to use it in conversation to sound smart tomorrow, lol.

 

[boneh3ad]

I'm going to make it a point to use it in conversation to sound smart tomorrow, lol.

Every time I try to do this, I forget within about 30 minutes.

 

[Cyrus]

Every time I try to do this, I forget within about 30 minutes.

Doubt is not a pleasant condition, but certainty is absurd.

— Voltaire

 

[boneh3ad]

Doubt is not a pleasant condition, but certainty is absurd.

— Voltaire

Nice try, but it doesn't really apply here, chief.

 

[Danger]

Maybe I'm missing something here because I didn't start flying until 1975, but I have never heard of a "neutral point" in relation to an aeroplane.

edit: Alright, I have heard of it, but it was in relation to the mile-high club, so I doubt that it is relevant to this thread.

 

[dtango]

Maybe I'm missing something here because I didn't start flying until 1975, but I have never heard of a "neutral point" in relation to an aeroplane.

Of course you have! You just didn't know it. I'm sure you were taught about CG movement for an airplane and the need to be sure how far aft the CG may move- for instance as you add passengers and bags for a GA airplane.

CG moving aft of the neutral point means bad juju!

 

[Danger]

Of course you have! You just didn't know it. I'm sure you were taught about CG movement for an airplane and the need to be sure how far aft the CG may move- for instance as you add passengers and bags for a GA airplane.

CG moving aft of the neutral point means bad juju!

Okay, yeah... I've never heard it called that, though.

 

[mugaliens]

Okay, yeah... I've never heard it called that, though.

It's not. They're confusing it with the center of pressure. The neutral point and the center of pressure are very closely related, but they're not synonomous.

 

[Cyrus]

It's not. They're confusing it with the center of pressure. The neutral point and the center of pressure are very closely related, but they're not synonomous.

No one's said anything about center of pressure here. I'm a bit confused about this post.

 

[mugaliens]

No one's said anything about center of pressure here. I'm a bit confused about this post.

When the CG is located at the neutral point, the aircraft is on the line between dynamic stability and instability. The neutral point is fixed. The center of pressure, however, changes with flight control manipulation. It's close to the neutral point, but not precisely so.

For dynamic stability the CG is located forward of both.