UAL747
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I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 4:24 pm

Hey guys, I know this is somewhat hobby related, but I really need some technical points of view. I've done some really crude drawings of an aircraft design that I did. Basically it's just my fantasy aircraft, but I wanted to have any input you had that I could make the design better and what I really needed to state, and or do to the drawing to make things more realistic for flight. Please don't hammer me with negative comments, just give some constructive advice. I'm no engineer (which is why I'm enlisting your help), but I wanted to see if you had any ideas of design changes, or comments.

Anyway, here are the pics: (Buries head in embarrassment as I am 29 and still drawing fantasy planes)




I would like to make the drawing and design as real as possible, and I know that's not always the case unless you can actually test it and determine what works best, but I thought I'd give it a shot from you guys.

Let me know what I'm missing.

Thanks!

UAL

Edit: Yeah, some things are fictitious, like the names of the engines, thrust, etc. And don't pay attention to the dimensions really. They are WAY off as stated. The cabin is supposed to be the size of a 4-door car though, if that helps any.

[Edited 2009-05-22 09:33:39]
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2H4
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 4:35 pm

Some random thoughts from a non-engineer:

- Man, that's a LOT of thrust given the size of the aircraft!

- The side view depicts a much greater wing sweep than the top view

- I'm not sure slats would be necessary, especially given their weight and complexity....but I suspect canards might be, a la the Beechcraft Starship.

2H4
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UAL747
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 4:39 pm



Quoting 2H4 (Reply 1):
- Man, that's a LOT of thrust given the size of the aircraft!

What would be the appropriate Thrust Rating do you think? 2500-5000lbs per engine?
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
2H4
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 4:46 pm



Quoting UAL747 (Reply 2):
What would be the appropriate Thrust Rating do you think? 2500-5000lbs per engine?

Well, as an example, the Cessna Citationjet has about 2000 lbs per engine....and that aircraft carries two on the flight deck and five in the pax cabin. I suspect you could update your images with smaller-diameter turbofans to reflect such engines.

My favorite thing about your aircraft is the layout. It's wild enough to be very intriguing to look at, yet it doesn't seem like an unfeasible aerodynamic/engineering challenge. Well, from my non-engineer perspective, anyway. I keep thinking "Jet Starship" when I look at it. Very cool.

2H4
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Soku39
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 5:10 pm

Most jets that are that small don't have/need APUs, they start up electrically.

Probably wouldn't need slats, could be dangerous as you could get way behind the power curve in an airplane that light, that also had slats.

Move Nav lights to the wingtips, so people could see you at a perpendicular angle.

Probably wont need the vortex generators if you have that much power and are moving that fast (unless you want to keep the slats and will need the aileron authority when flying slow), but for an aircraft like that control should never been an issue...

Just thoughts off the top of my head.
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David L
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 5:56 pm



Quoting 2H4 (Reply 3):
My favorite thing about your aircraft is the layout. It's wild enough to be very intriguing to look at, yet it doesn't seem like an unfeasible aerodynamic/engineering challenge.

Hmm... I'm thinking it might only be feasible with some degree of FBW - I'm not sure how inherently stable it would be.

However...

Quoting 2H4 (Reply 3):
Well, from my non-engineer perspective, anyway

... Ditto.  Smile
 
DiamondFlyer
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 6:11 pm

Looks interesting, from my non-engineeering standpoint. Has possibilities, but I think noise is going to be a real issue. Also, it seems to me those engines are way, way to powerful for an airplane this size. Looking at what dimensions you've got on it now, wingspan wise, its about the same as a Cessna Citation Mustang or Eclipse 500 VLJ. So basically, you've got a VLJ sized airplane, that you want to go 5000 nm with. I'm not real sure where your going to pack all that fuel in, but it might work. Realistically, you could probably power this on some form of the Pratt & Whitney PW600. Either the PW617 @ 1,615 lbs of thrust, or the proposed PW625 @ 2,500 lbs of thrust. Or, alternatively, you could use either the Williams FJ33 or FJ44. The latter of the two (FJ44) is currently used on the Cessna CJ1/2/3/4, Piper Jet and the Primer I.

-DiamondFlyer
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Fly2HMO
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 6:32 pm

Quoting 2H4 (Reply 1):
- Man, that's a LOT of thrust given the size of the aircraft!

There's no replacement for... uhh.. displacement? 


Here's another non-engineer opinion, but a pilot's one at that:

*It would seem to me as being rather unstable in the vertical (yaw) axis due to the plane's short overall length. As mentioned earlier, FBW could resolve this. Another option would be extending the wingtip vertical stabilizers even more, or adding a ventral strake.

*Double slotted flaps are probably unnecessary in a plane like this. Plain or single slot flaps would suffice and be easier to make. All the bizjets I've ever seen either have plain, single slot, or split flaps. I'll wait for 2H4 to pull out his weird airplanes vault to show other wise though   



*Spoilers?

*How are you supposed to enter the cabin?

*Can you elaborate on the "Vertical Stab Platfrom on tail/engine pylons"? Could you do a profile close-up of that arrangement? kinda hard to tell from the top down what it looks like.

*In lieu of the vertical stab mentioned above, another option would be canards.

*Dunno about you guys but seems like the center of lift would be very far back from the center of gravity. It could have considerable downward pitching moments. A possible solution would be mounting the engines farther back, or just keeping the big/heavy but powerful ones it already has  cool 

Overall I gotta say it looks very futuristic yet feasible and very aesthetically pleasing, a la Piaggio Avanti. Nice work  

[Edited 2009-05-22 11:39:13]
 
vikkyvik
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 6:37 pm



Quoting DiamondFlyer (Reply 6):
Looks interesting, from my non-engineeering standpoint. Has possibilities, but I think noise is going to be a real issue.

 checkmark 

If you want to fly Mach 0.75-0.80, you're probably going to need a sleeker nose. Try a fineness ratio of about 1.4-1.6, maybe (that's the ratio of nose length to fuselage diameter). The top view actually looks OK, but in the side view the nose looks a little stubby.

I'm thinking having the engines sitting right on top of the inboard wing is going to produce some "interesting" airflow, for the wing, the flaps, and the engine. Especially in landing configuration, the inboard section of the wing (where the flaps are) is the most heavily loaded part. The way I see it, if the inboard part of the wing stalls, then the separated airflow over the top of the wing is going to be going straight into the engine. I'm not sure what that will do, exactly, but I'd imagine it may disrupt the flow into the engine, at a time when you really don't want to do that  Smile

It looks like you have the elevator at the rear or the aircraft (though I could be wrong). If you assume that the aircraft CG is right near the wing's center-of-lift, that's not going to provide you with much moment-arm at all for the elevator (hence you typically see canards on rear-wing aircraft).

Same thing with the vertical stabilizers/rudders (which are on the winglets, right?). Looks to me like you don't have near enough surface area for the short moment-arm.

Anyway, just some thoughts  Smile
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David L
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 6:44 pm



Quoting FLY2HMO (Reply 7):
*It would seem to me as being rather unstable in the vertical (yaw) axis due to the plane's short overall length.

I was thinking pitch, too, as in...

Quoting Vikkyvik (Reply 8):
If you assume that the aircraft CG is right near the wing's center-of-lift, that's not going to provide you with much moment-arm at all for the elevator

 
2H4
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 8:16 pm



Quoting FLY2HMO (Reply 7):
*Dunno about you guys but seems like the center of lift would be very far back from the center of gravity. It could have considerable downward pitching moments. A possible solution would be mounting the engines farther back, or just keeping the big/heavy but powerful ones it already has

Or adding canards, like the Starship.

2H4
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rwessel
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RE: I'm An Amateur, But Can You Give Me Advice?

Fri May 22, 2009 10:44 pm

It's difficult to put high-lift devices (slats, flaps, etc.) on a single wing - almost all generate significant pitch changes when deployed, and the single wing makes it impossible to give the elevator much authority. And the lack of pitch authority limits your CG ranges as well, which, especially on a small aircraft, will cause problems loading it (and your passenger compartment is all well forward of the CG).

I'd also be concerned about your yaw stability. You have a *lot* of wetted are well forward of the CG, and fairly small vertical stabs only a bit behind the CG - not a good combination for directional stability. But I think pitch control is going to be your number one problem with this layout.

A significant increase in sweep would help address both problems, but then you have the issues associated with a sharply swept wing.

OTOH, with a pair of 10,000lb engines on a six-seater, discard the wings and go direct lift!  Wink
 
AirframeAS
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 2:54 am

A glass covered cockpit would be pretty heavy to deal with, I suggest using Lexan type plexiglass for the covering.
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UAL747
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 3:39 am

Let me ask a few questions based on your respoonses:

1. I made the design with the belief that having the large engines so far behind the center of the aircraft would actually leave room for the cabin/cockpit to be in front of the center of gravity, due to the sheer weight of the engines. How much would small engines that power this size of aircraft weigh?

2. I thought, in hindsight, about putting a canard forward of the wing after I finished the rendering for a vertical stablizer, and I think you might be right on the CG issue. However, what are the problems with stability with this addition? I've *heard* that aircraft with forward vertical stabs are more difficult to control, and require FBW technology for inputs. On the Starship, I've noticed there is 0 degrees of sweep on the forward stab, why is this? Also, where would be a good position to put a forward stab on this aircraft so that it does not affect airflow over the wing and the engines? I believe the Starship's and Piaggio's are fairly close to level with their wings.

3. Do vortex generators not benefit all aircraft? We even have them on our Cessna 335. I believe they were an addition, but they are definitely there.

4. Regarding the Yaw Control, I'm assuming that the horizontal stablizers should be similar in area to what a single horizontal stablizer should be, but divided in half since there are two of them. Am I correct, or because you have two, does that change anything? I'm going to guess that having them on the tips of the wings do something to their overall effectiveness.

- As I have it now, if you look just behind what is the "APU" on the top down drawing, there is a large single vertical stablizer in the middle at the very back of the aircraft. Also, in case this was not enough, I put stablizers built into the engine pylons, as I believe there are some rear-engined aircraft that DO use this feature, though I can't remember which one, but I think it's late model MD aircraft, like the MD-90 or 717, not sure...But, this thought did come to mind that it was A. too small, and B. had too much interference from the fuselage which rises up above it to get enough airflow over the top to actually be able to pull the nose upward.


Quoting FLY2HMO (Reply 7):
*It would seem to me as being rather unstable in the vertical (yaw) axis due to the plane's short overall length. As mentioned earlier, FBW could resolve this. Another option would be extending the wingtip vertical stabilizers even more, or adding a ventral strake.

Could you explain to me what a Ventral Strake is? I think that I have an idea, but would like that clarified.

Quoting Rwessel (Reply 11):
A significant increase in sweep would help address both problems,

Can you explain how a larger sweep would affect these issues a little more?

Thanks guys so much for the input on the hypothetical aircraft. It's really interesting to me, even if I'm boring you guys!

UAL
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
AirframeAS
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 3:47 am



Quoting Ual747 (Reply 13):
Do vortex generators not benefit all aircraft?

Not all aircraft have them. The A320's don't have them while the 737's do. It really depends on how the shape of the wing reacts to the airflow over the wing.
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UAL747
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 3:53 am

BTW, I will redraw this in a few days when I get enough comments and add the suggested features, and see what we all come up with. Again, thanks a lot guys! I've always drawn weird aircraft designs, but this makes it so much more fun to me when the effort is collaborative!

UAL
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DiamondFlyer
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 4:57 am

On engine weights:
A P&W 615F, as used on a Cessna Citation Mustang (510) weighs 310 pounds dry. The highest thrust version of the Williams FJ33 (1900 lbs) weighs approximately 300 pounds dry. The highest thrust version of the Williams FJ44 (3,600 lbs) weighs roughly 650 pounds dry. So, they are all fairly light engines.

And, to add to what I had earlier. I'm not sure if you've ever flown any of the Diamond Industries aircraft (DA-20/40/42), but that glass canopy design is going to be hotter than an oven. Literally, it can be 45-50 degree's F outside air temperature, and on a sunny day, you're going to be so hot, you wish you had air conditioning. Just a thought

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tdscanuck
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 5:04 am



Quoting Ual747 (Reply 13):
1. I made the design with the belief that having the large engines so far behind the center of the aircraft would actually leave room for the cabin/cockpit to be in front of the center of gravity, due to the sheer weight of the engines. How much would small engines that power this size of aircraft weigh?

You really don't want to be using weight to help counteract issues unless you absolutely have to. For cost reasons, if you just needed weight you'd be better off using ballast and normally-sized engines that using over-sized engines. However, using weight should be the weapon of last resort because of the knock-on effects (almost universally bad) that weight has on virtually every performance parameter.

Quoting Ual747 (Reply 13):
I thought, in hindsight, about putting a canard forward of the wing after I finished the rendering for a vertical stablizer, and I think you might be right on the CG issue. However, what are the problems with stability with this addition?

You can do a stable canard. There's a good discussion of the pros/cons of canards here:
http://www.airliners.net/aviation-forums/tech_ops/read.main/204723/

Quoting Ual747 (Reply 13):
I've *heard* that aircraft with forward vertical stabs are more difficult to control, and require FBW technology for inputs.

A forward vertical stab would be unstable, because C_N_beta would be positive (bad). Hence you'd need active stability control (FBW) to keep you stable. It would be incredibly difficult to certify such a thing in the civilian world (military can get away with it).

Quoting Ual747 (Reply 13):
On the Starship, I've noticed there is 0 degrees of sweep on the forward stab, why is this?

My guess is that the canard isn't working hard enough for it to matter. Straight wings are easier and cheaper to build and, excepting the transsonic issues, perform better. If the canard lift coefficient is a lot lower than the wing lift coefficient at cruise (which it should be), then there may not be any transsonic drag issue on the canard.

Quoting Ual747 (Reply 13):
Also, where would be a good position to put a forward stab on this aircraft so that it does not affect airflow over the wing and the engines?

That's likely not possible given the dimensions you're working with.

Quoting Ual747 (Reply 13):
Do vortex generators not benefit all aircraft?

They're not universally good, no. You pay a price in drag and weight in order to get their benefit. In many cases, they might be the cheapest solution to an aerodynamics problem but they're not always going to be beneficial if you don't already have a problem.

Quoting Ual747 (Reply 13):
Regarding the Yaw Control, I'm assuming that the horizontal stablizers should be similar in area to what a single horizontal stablizer should be, but divided in half since there are two of them. Am I correct, or because you have two, does that change anything?

They need to be a little bigger than double a single stab, because they're got smaller aspect ratios and will not be as effective.

Quoting Ual747 (Reply 13):
I put stablizers built into the engine pylons, as I believe there are some rear-engined aircraft that DO use this feature, though I can't remember which one, but I think it's late model MD aircraft, like the MD-90 or 717

You get some stability effect from any horizontal surface near the rear. I suspect you're thinking of the movable pylon flap on the MD-90, which is there to help with stall recovery.

Quoting Ual747 (Reply 13):
Could you explain to me what a Ventral Strake is?

It's an extension to the front of the vertical fin, running along the body. It helps with lateral stability and makes it harder to stall the vertical tail.

Quoting Ual747 (Reply 13):
Can you explain how a larger sweep would affect these issues a little more?

Sweep has a major effect on center of pressure. More sweep will move your center of pressure aft, increasing the distance between the center of pressure and the CG. That gives you more loading flexibility (but also requires a more powerful trim surface).

Tom.
 
ThirtyEcho
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 5:13 am

I can't imagine how hot that all glass cabin is going to get; try being #6 for takeoff in Phoenix in the summer with an OAT of 125 degrees.

In flight, it will be just as bad. No way for the crew or passengers to duck the sun's glare. That cabin is going to be like something out of "Lawrence of Arabia."

BTW, there isn't a door.
 
vikkyvik
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 6:01 am

Just an FYI, I think you may be mixing up horizontal and vertical stabilizers in the following:

Quoting Ual747 (Reply 13):
I thought, in hindsight, about putting a canard forward of the wing after I finished the rendering for a vertical stablizer, and I think you might be right on the CG issue. However, what are the problems with stability with this addition? I've *heard* that aircraft with forward vertical stabs are more difficult to control, and require FBW technology for inputs. On the Starship, I've noticed there is 0 degrees of sweep on the forward stab, why is this? Also, where would be a good position to put a forward stab on this aircraft so that it does not affect airflow over the wing and the engines? I believe the Starship's and Piaggio's are fairly close to level with their wings.



Quoting Ual747 (Reply 13):
Regarding the Yaw Control, I'm assuming that the horizontal stablizers should be similar in area to what a single horizontal stablizer should be, but divided in half since there are two of them. Am I correct, or because you have two, does that change anything? I'm going to guess that having them on the tips of the wings do something to their overall effectiveness.

Horizontal stabilizers are there for pitch stability and control. Vertical stabilizer (tail) is there for yaw stability and control.

Quoting Tdscanuck (Reply 17):

My guess is that the canard isn't working hard enough for it to matter. Straight wings are easier and cheaper to build and, excepting the transsonic issues, perform better. If the canard lift coefficient is a lot lower than the wing lift coefficient at cruise (which it should be), then there may not be any transsonic drag issue on the canard.

You know, I'm wondering, given the fact that the Starship cruised around Mach 0.6 (that's the number I found, at least), if it even really needed a swept main wing, or if it was something that they were forced to do to alleviate some issue (vert.stab. moment-arm, perhaps?).

Oh, wait, didn't the Starship actually have a variable-sweep canard? Looks like it in the following photos:


View Large View Medium
Click here for bigger photo!

Photo © Jaysen F. Snow - Midwest Tail Chasers



View Large View Medium
Click here for bigger photo!

Photo © David Lednicer



[Edited 2009-05-22 23:09:27]
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Starlionblue
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 10:33 am



Quoting Vikkyvik (Reply 19):
Just an FYI, I think you may be mixing up horizontal and vertical stabilizers in the following:

They are also "confused" in the drawing. As Vikkyvik says, horizontal stabilizers + elevators are horizontal and are used for pitch control and stability. Vertical Stabilizers + rudders are vertical and are used for yaw control and stability.

There are of course the usual exceptions and hybrids like V-tails.
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Goldenshield
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 11:40 am



Quoting FLY2HMO (Reply 7):
All the bizjets I've ever seen either have plain, single slot, or split flaps. I'll wait for 2H4 to pull out his weird airplanes vault to show other wise though

Single engine Cessnas use a combo fowler/slot system. The flap moves out 1/2 its length during the first 10-15 degrees of travel using a fowler motion, then pivots down the rest of the way forming the slot. So, while technically, it IS a slotted flap, its movement suggests otherwise. The MD-80 is a slotted flap as well, but it never moves aft, and just pivots along an axis instead.



I know, a bit OT, but still useful.  Smile
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David L
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 2:52 pm



Quoting Tdscanuck (Reply 17):
Quoting Ual747 (Reply 13):
Could you explain to me what a Ventral Strake is?

It's an extension to the front of the vertical fin

I'm not sure whether I'm being pedantic or just plain wrong (I do both pretty regularly) but wouldn't that be a dorsal strake? To me, "ventral" is associated with the belly area, be it on an aircraft or a fish, etc.
 
David L
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 3:29 pm



Quoting David L (Reply 22):

OK, I looked up the meaning of "ventral" and it relates to the "front" so I concede it would work.
I was confused by ventral and dorsal fins on fish. I guess they have to be stood on their tails before their fins are classified.  Smile
 
tdscanuck
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 4:08 pm



Quoting ThirtyEcho (Reply 18):
I can't imagine how hot that all glass cabin is going to get; try being #6 for takeoff in Phoenix in the summer with an OAT of 125 degrees.

In flight, it will be just as bad. No way for the crew or passengers to duck the sun's glare. That cabin is going to be like something out of "Lawrence of Arabia."

BTW, there isn't a door.

Could do it the way a Seawind does it...they just hinge the entire window and use that to get in/out. I can't find a picture with the canopy open, but you can get the idea pretty easily from the stock photos:
http://www.seawindpilots.com/photos.htm

Quoting Vikkyvik (Reply 19):

You know, I'm wondering, given the fact that the Starship cruised around Mach 0.6 (that's the number I found, at least), if it even really needed a swept main wing, or if it was something that they were forced to do to alleviate some issue (vert.stab. moment-arm, perhaps?).

Might have been to get the center of pressure farther back. Might also have been to get the propeller disks behind the fuselage for noise and thrown-blade reasons. Or something entirely different. But I think there must have been a reason beyond "it looks good."

Quoting David L (Reply 22):

Quoting Tdscanuck (Reply 17):
Quoting Ual747 (Reply 13):
Could you explain to me what a Ventral Strake is?

It's an extension to the front of the vertical fin

I'm not sure whether I'm being pedantic or just plain wrong (I do both pretty regularly) but wouldn't that be a dorsal strake? To me, "ventral" is associated with the belly area, be it on an aircraft or a fish, etc.

Crap. You're not being pedantic, you're absolutely right. Even with the correct definition of ventral=front, I think "ventral strake" in aircraft speak is the ones underneath, not the ones on the vertical fin.

Tom.
 
David L
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 5:15 pm



Quoting Tdscanuck (Reply 24):
You're not being pedantic, you're absolutely right.

Phew! Sorry.  biggrin 
 
Fly2HMO
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 5:16 pm



Quoting Goldenshield (Reply 21):
So, while technically, it IS a slotted flap, its movement suggests otherwise.

I know, I have over 200hrs in type  cool  I guess you could say for the first 10deg its a fowler, and the rest a slotted.


Back to bizjets, I think most Citations are either single slot or plain.
 
UAL747
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 5:46 pm

Quoting FLY2HMO (Reply 26):
I know, I have over 200hrs in type    I guess you could say for the first 10deg its a fowler, and the rest a slotted.

On the topic of flaps, what are on the Cessna 335/340's and I think 310's?

They actually come out of the bottom of the wing, but do not change the camber of the wing...

The only way I can describe it is it's like a spoiler, but on the bottom of the wing.

UAL

[Edited 2009-05-23 10:47:26]
"Bangkok Tower, United 890 Heavy. Bangkok Tower, United 890 Heavy.....Okay, fine, we'll just turn 190 and Visual Our Way
 
Goldenshield
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 6:10 pm



Quoting Ual747 (Reply 27):
They actually come out of the bottom of the wing, but do not change the camber of the wing...

That would be Split flaps. (See the image in reply 7.)
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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 10:27 pm



Quoting Vikkyvik (Reply 19):
Oh, wait, didn't the Starship actually have a variable-sweep canard?

Yes indeed. Here's a side-by-side example:

http://i40.tinypic.com/dxh7wx.jpg


Quoting Tdscanuck (Reply 24):
Might have been to get the center of pressure farther back. Might also have been to get the propeller disks behind the fuselage for noise and thrown-blade reasons. Or something entirely different. But I think there must have been a reason beyond "it looks good."

The canards extend/retract with the flaps, so I suspect they sweep to counter the center of pressure shift with flap extension/retraction.

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RE: I'm An Amateur, But Can You Give Me Advice?

Sat May 23, 2009 11:28 pm



Quoting FLY2HMO (Reply 7):
All the bizjets I've ever seen either have plain, single slot, or split flaps. I'll wait for 2H4 to pull out his weird airplanes vault to show other wise though

I'll gladly stand corrected, but I'm pretty sure Falcons have Fowler flaps.

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RE: I'm An Amateur, But Can You Give Me Advice?

Sun May 24, 2009 1:30 am



Quoting David L (Reply 23):
OK, I looked up the meaning of "ventral" and it relates to the "front" so I concede it would work.
I was confused by ventral and dorsal fins on fish. I guess they have to be stood on their tails before their fins are classified.

"Ventral" comes from latin, where "ventro" means belly. So it is more "belly" than "front". Since we stand upright, it has also come to mean "frontal".

To continue the etymological discussion, "dorso" means back in Latin (and Italian).
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RE: I'm An Amateur, But Can You Give Me Advice?

Sun May 24, 2009 5:22 am



Quoting 2H4 (Reply 29):
Yes indeed. Here's a side-by-side example:

Sweet, thanks!

That thing looks like it'd come mighty close to chopping the pilots' feet off when it moves to the swept position  Smile

Quoting 2H4 (Reply 29):
Quoting Tdscanuck (Reply 24):
Might have been to get the center of pressure farther back. Might also have been to get the propeller disks behind the fuselage for noise and thrown-blade reasons. Or something entirely different. But I think there must have been a reason beyond "it looks good."

The canards extend/retract with the flaps, so I suspect they sweep to counter the center of pressure shift with flap extension/retraction.

I think Tdscanuck was referring to the main wing sweep.
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RE: I'm An Amateur, But Can You Give Me Advice?

Sun May 24, 2009 6:34 am



Quoting Ual747 (Reply 27):

They actually come out of the bottom of the wing, but do not change the camber of the wing...

The only way I can describe it is it's like a spoiler, but on the bottom of the wing.

Split flap...from an aerodynamic point of view, it behaves like increased camber (and increased AoA).

Quoting Vikkyvik (Reply 32):

I think Tdscanuck was referring to the main wing sweep.

Yep, but I think 2H4 is right about why they move the canard.

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RE: I'm An Amateur, But Can You Give Me Advice?

Sun May 24, 2009 9:45 am



Quoting Starlionblue (Reply 31):
"Ventral" comes from latin, where "ventro" means belly. So it is more "belly" than "front". Since we stand upright, it has also come to mean "frontal".

To continue the etymological discussion, "dorso" means back in Latin (and Italian).

That's pretty much the logic I was using. My only doubt was whether or not the use was as strict in aeronautics or if the "human" usage (i.e. front/rear) had prevailed in some cases. That's another loose end tied up.  Smile

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