Ziggy From United States of America, joined Jun 2001, 178 posts, RR: 0 Posted (11 years 3 months 2 days 23 hours ago) and read 1127 times:
On the Beech 1900 series there are vertical fins or stablizers set below the horizontal stablizers. (like upside down winglets) I'm wondering if their purpose is like the winglets, to use the vortices to enhance proformance?
Illini_152 From United States of America, joined Jan 2001, 1000 posts, RR: 2 Reply 1, posted (11 years 3 months 2 days 21 hours ago) and read 1062 times:
I doubt it. If you look at the vertical stab on the 1900, is is amost identical in size to the stab on a 350 King Air and a 99 Airliner. More than likely the extra vertical surfaces were needed to increase lateral stability in the event of an engine failure, and rather than redesign the whole tail, Beechcraft just added a few extra surfaces on there.
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Mr Spaceman From Canada, joined Mar 2001, 2780 posts, RR: 15 Reply 2, posted (11 years 3 months 2 days 12 hours ago) and read 1019 times:
I've always wondered about those vertical fins on the tail of a beech 1900 myself. I also thought it had something to do with stability, as Illini_152 mentioned, because I'm used to seeing winglets on an aircrafts main wing at the very tip...not on the horizontal stab. Just an observation.
Hopefully someone will let us know for sure what they do...Illini_152 didn't seem certain, however I suspect he's correct about stability.
Regardless of their purpose do they have a specific name?
The MD-11 also has winglet type devices which are on the bottom surface of the wingtips. I feel these devices must deal with the forces of tip vortices because of their location.
P.S. Some people think that winglets are used to enhance performance, as mentioned by Ziggy, and some think their purpose is to reduce drag by reducing the vortex at the wingtip. Which is it? Can their purpose be for both reasons at the same time?
Staffan From , joined Dec 1969, posts, RR: Reply 7, posted (11 years 3 months 1 day 14 hours ago) and read 959 times:
The basics behind a wing is that there is high pressure under the wing and low pressure on top of it to create lift, this pressure differance is achieved by shaping the wing so that the air has to travel further to go above the wing than the air going underneath it.
Anyway, when you have this pressure differance, the air under the wing will try to 'escape' to the top of the wing by curling across the tip of the wing, this has two negative effects. The first is that you loose pressure under the wingtip, and the second is that a vortice is created. A vortice is very turbulent air spiraling off the tip of the wing, a motion started by the air flowing across it, this creates drag.
So, by mounting a winglet you can somewhat reduce the vortice and at the same time gain something from it. The winglet is shaped like a small wing, with a carefully calculated shape and and angle of attack, and when the secondary flow (across the wingtip) hits the winglet, alot of the energy in this air is used to create a liftforce pointed inwards and slightly forward (somtimes referred to as thrust), the result being that the air is slowed down and a much smaller vortice is created at the tip of the winglet.
If you do a forum search on the subject you'll find more info on it.
AJ From Australia, joined Nov 1999, 2376 posts, RR: 27 Reply 9, posted (11 years 3 months 6 hours ago) and read 934 times:
The vertical fins below the horizontal stabiliser and the fuselage allow for directional stability at high angles of attack due to the large (monsterous) bulk of the fuselage blanketing the tail.
The horizontal fins allow a more flexible CofG range.
UALPHLCS From , joined Dec 1969, posts, RR: Reply 11, posted (11 years 2 months 4 weeks ago) and read 902 times:
Thank you for this thread first of all its a question i always wondered about. In addition to the vertical surfaces on the tail could someone tell me about the little horizantal surfaces under the tail on the fuselage? In the first pic they are clearly visable right above the registration.
Speedbird001 From United Kingdom, joined May 2000, 30 posts, RR: 0 Reply 13, posted (11 years 2 months 3 weeks 6 days 8 hours ago) and read 883 times:
This is quite an interesting subject which I have heard the usual theory of lower pressure below the wing pushing up etc, but I have also heard another theory that the air molecules "stick" more to the top of the wing. Does anyone have more information on alternitive theorys for wing lift generation?
Ziggy From United States of America, joined Jun 2001, 178 posts, RR: 0 Reply 15, posted (11 years 2 months 3 weeks 6 days 2 hours ago) and read 859 times:
What happens is that you have a High pressure below the wing and low pressure above it. You have what is call a boundary layer or a still or slow moving air. This layer is if at most only 1/16 of an inch and could be smaller, but yet it's present. I'm sure a aero engineer could go into far more detail about this than I can. But that's it in a nut shell.
EssentialPowr From United States of America, joined Sep 2000, 1820 posts, RR: 2 Reply 16, posted (11 years 2 months 3 weeks 6 days 1 hour ago) and read 867 times:
I've watched this thread with some interest...
With regard to the 747 and the E2, the end plates on the vertical stabilizer are to enhance directional stability, as mentioned above. The reason for the endplates, as opposed to the std config, is due to the fact that the space shuttle on the 747, and the radome of the E2, certainly impedes airflow to the vertical fin...Grumman chose to build 1 tail, and used it for the C2 and E2 for the same reason as described below:
The 1900d is, as most know, simply an evolution of the B1900C, and of the King Air series. In particular, the tail shared by the -200, -300, -350, -1900c and -1900d is the same tail as introduced by the F90 in 1979, for a 750 shp application. As the a/c was lengthened to the -200 and above, the same tail worked simply b/c increasing the length of the a/c compensates for tail area.
(Witness the 747SP, the "short" 747 that has one of the largest vertical tails in the history of a/c production, to include the C5, AN 124, and B52.)
As horsepower increased, the vertical fin area reached a point where it HAD to be increased for the 1900d. So why not use the same part and not have to retool? BINGO.
So for the 1900d, which has a great deal of single engine Reserve HP to accomodate and engine out situation), extra vertical surface was needed, hence the endplates on the tail. It's also greater than 12,500 lbs, which places some additional constraints on the design.
The directional stab topic surfaced about 2 wks ago; my assumption for the hozizontal surfaces on the 1900d is the same as the for the endplates...it's cheaper to build the same vert tail for a variety of a/c, and simplify the 1900d as needed to account for its specific requirements in the pitch and yaw (and therefore roll) axes.
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 17, posted (11 years 2 months 3 weeks 5 days 19 hours ago) and read 851 times:
In short, the viscosity of the air will tend to make it follow the curved upper surface of the wing. This means there is a downward acceleration of the air. There's never an acceleration in a fluid without a negative pressure gradient, i e a region of lower than ambient pressure in this case. This is what generates lift.
You can also say that lift is generated by (mainly) the top surface of the wing accelerating the air downwards, creating a lift force proportional to the downward momentum (downwash) given to the air.
BTW, boundary layers can be well over 1/16th of an inch. The boundary layer thickness can be calculated from the reynolds number and the distance from the leading edge. It will increase in thickness faster in turbulent than in laminar flow. To get an appreciation of boundary layer thickness, note the distance between the fuselage and the intake lip on the radiator of a P51 or the #2 engine on a DC-10/MD-11. This distance is there to prevent boundary layer ingestion.
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