dual/single vertical stabilizer
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dual/single vertical stabilizer
Hi all,
I have been having a look around for data on the above... specifically, why would you design a fighter with a single stablizer over a dual stabilizer fin.
The american and russian fighters seem to utilise a dual stabilizer design (on the whole except the F16) where as the european designers seem to go for a single stabilizer design????
if anyone can shed some light it would be appreciated
thanks
I have been having a look around for data on the above... specifically, why would you design a fighter with a single stablizer over a dual stabilizer fin.
The american and russian fighters seem to utilise a dual stabilizer design (on the whole except the F16) where as the european designers seem to go for a single stabilizer design????
if anyone can shed some light it would be appreciated
thanks
That used to be one of those 'Bloggs' questions we used to get at CFS groundschool during teaching practice sessions:
"Sir, why do aircraft like the F-15 have 2 fins?"
"To improve directional stability at high Mach No., Bloggs"
Followed by a 4-colour diagram of CL alpha curves, yaw angle etc.
This was fine, until one day I was playing 'Bloggs' and asked my colleague:
"Sir, why do aircraft like the Shackleton have 2 fins?"
"To...err, ahhrrghh - you bugger!"
"Sir, why do aircraft like the F-15 have 2 fins?"
"To improve directional stability at high Mach No., Bloggs"
Followed by a 4-colour diagram of CL alpha curves, yaw angle etc.
This was fine, until one day I was playing 'Bloggs' and asked my colleague:
"Sir, why do aircraft like the Shackleton have 2 fins?"
"To...err, ahhrrghh - you bugger!"
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"Sir, why do aircraft like the Shackleton have 2 fins?"
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The Iranian thingy is called a 'Saeqeh' - Thunderbolt. See pictures here: Saeqeh fighter planes tested successfully in Iran
And by the beard of the Prophet (may peace be upon him), may the infidels be struck down if they slander the glorious engineers of the Islamic Republic by suggesting that it is a rebuilt Northrop F-5! It is entirely indigenous!
(Or not.... they've even pinched the paint scheme from the Blue Angels...
)
S41
And by the beard of the Prophet (may peace be upon him), may the infidels be struck down if they slander the glorious engineers of the Islamic Republic by suggesting that it is a rebuilt Northrop F-5! It is entirely indigenous!
(Or not.... they've even pinched the paint scheme from the Blue Angels...
)S41
BAe Systems have a large number of wings left over from the Avro 707 series, so for the forseable future, all BAE aircraft will be saddled with a bloody huge fin.
CBA,
There are some images of twin-finned mock-ups at the following links. These were the early proposals in the various projects before the Eurofighter.
eurofighter @ starstreak.net • Index page
The Germans were proposing a twin-finned design called TFK-90.
TJ
There are some images of twin-finned mock-ups at the following links. These were the early proposals in the various projects before the Eurofighter.
eurofighter @ starstreak.net • Index page
The Germans were proposing a twin-finned design called TFK-90.
TJ
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Single and twin fin is a fascinating area. Going back to a number of projects, the choices have not always been obvious.
F-16 was two fins until quite late on, then jumped to one. F-14 was one fin and jumped to two. F-15 originally had (I am told) one fin and went to two. Early F-18 designs had one fin. And so it goes on.
The reason given by LM for designs like F-22 and F-35 was, in my view, as much to do with the aft fuselage structure and the difficulty of getting a single fin mounted above or in between the engines as much as the aerodynamic advantages. If you need two booms aft to mount horizontal tails, slapping the fin on the boom can look attractive to reduce weight. Twin fins are touted as superior to singles at high AOA, and especially where any yaw is encountered, where single fins can get severely stressed by vortices from leading edges (the Tornado F2 suffered from this). However, F-18 had the same problem with two fins, so go figure...
I have been told that the Tornado and Typhoon HUGE fins are down to the BAE chief designer at the time, who demanded high margins for directional stability at certain Mach numbers - I'm not an aerodynamicist, so can't be sure.
Two fins are a big help with signature - a single vertical fin will usually be a decent reflector, two canted fins can be engineered to reduce the RF return.
The Iranian aircraft is a straight F-5 copy, and any advantages gained by two fins are likely to be outweighed by the additional weight they will have to have incurred in adding structure on the aft fuselage to mount those two fins.
Regards
Engines
F-16 was two fins until quite late on, then jumped to one. F-14 was one fin and jumped to two. F-15 originally had (I am told) one fin and went to two. Early F-18 designs had one fin. And so it goes on.
The reason given by LM for designs like F-22 and F-35 was, in my view, as much to do with the aft fuselage structure and the difficulty of getting a single fin mounted above or in between the engines as much as the aerodynamic advantages. If you need two booms aft to mount horizontal tails, slapping the fin on the boom can look attractive to reduce weight. Twin fins are touted as superior to singles at high AOA, and especially where any yaw is encountered, where single fins can get severely stressed by vortices from leading edges (the Tornado F2 suffered from this). However, F-18 had the same problem with two fins, so go figure...
I have been told that the Tornado and Typhoon HUGE fins are down to the BAE chief designer at the time, who demanded high margins for directional stability at certain Mach numbers - I'm not an aerodynamicist, so can't be sure.
Two fins are a big help with signature - a single vertical fin will usually be a decent reflector, two canted fins can be engineered to reduce the RF return.
The Iranian aircraft is a straight F-5 copy, and any advantages gained by two fins are likely to be outweighed by the additional weight they will have to have incurred in adding structure on the aft fuselage to mount those two fins.
Regards
Engines
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I should also think that the reason that naval aircraft have twin fins is to allow easier storage in confined carrier hangers.
There is also the benefit that you can have one removed by ground fire or SAM and still retain directional stability, supposedly (on certain aeroplanes).
There is also the benefit that you can have one removed by ground fire or SAM and still retain directional stability, supposedly (on certain aeroplanes).
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CirrusF:
Was not another advantage that airflow over the Rudder and fin from the inboard engines gave you rudder authority at lower speeds ?
"Sir, why do aircraft like the Shackleton have 2 fins?"
Because at that time it was considered that two elliptical vertical surfaces at each end of a horizontal tailplane gave less induced drag than a single, larger non-elliptical central fin.
Because at that time it was considered that two elliptical vertical surfaces at each end of a horizontal tailplane gave less induced drag than a single, larger non-elliptical central fin.
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Dual/single stabs
Or in the case of the YF-23, cantering the twin vertical stabs meant they could do away with the horizontal stabs.
YF-23 Black Widow II
YF-23 Black Widow II
Did the YF-23 designer own a 'doctor killer' Beechcraft Bonanza?
Or maybe he was inspired by an old British design, the Supermarine 508:
Or maybe he was inspired by an old British design, the Supermarine 508:
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Was not another advantage that airflow over the Rudder and fin from the inboard engines gave you rudder authority at lower speeds ?
Also the fins would be clear of boundary layer effect from the fuselage, and also they would block the creation of induced tip vortices from the tailplane (like the winglets on many modern aircraft).
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There is also the stealth consideration - a single fin needs to be mounted vertically, therefore possibly creating 'corner reflectors' with other bits of the ac it is at 90 degrees to. Twin fins can be moounted at an angle to avoid this (see F-117, F-22 etc).
Engines has a good point about "twin boom" designs - on the F-22, JSF, F-15, MiG-29 and Su-2x/3x, you'd need to add beef in the middle for a single fin.
Canting for stealth is another big consideration - the vertical tail gives you a large lateral RCS spike, albeit a narrow one.
However, in the case of the F-16, F-15 and F-18 (and I am willing to bet the Typhoon and Rafale as well) the decision was more like "do we have one tail and make it huge, so that it does not get blanketed at high alpha, or do we have two and run the risk of them getting buffeted and overstressed by the vortices?"
Canting for stealth is another big consideration - the vertical tail gives you a large lateral RCS spike, albeit a narrow one.
However, in the case of the F-16, F-15 and F-18 (and I am willing to bet the Typhoon and Rafale as well) the decision was more like "do we have one tail and make it huge, so that it does not get blanketed at high alpha, or do we have two and run the risk of them getting buffeted and overstressed by the vortices?"
Don't you get better authority with twin rudders in the event of an engine failure (on a two-engined aircraft of course)?
And if I recall correctly the original F-117 (Have Blue?) had *inward* canted fins, but both crash and the design was changed to the familiar outward canted design. Wonder what they would have looked like... *goes off to google*
Yep, right i was.
From F-117 Reunion
And if I recall correctly the original F-117 (Have Blue?) had *inward* canted fins, but both crash and the design was changed to the familiar outward canted design. Wonder what they would have looked like... *goes off to google*
Yep, right i was.
From F-117 Reunion