Bigger tails?

[Maxrobot1]

Have you noticed that it semed that American warbirds tails seem to have grown during their progression and development?
I mean, look at just about any warbird and compare its early models and prototype to its final version. Examples are the B-17 from the "Shark tail" to the big tail, ,F4F with the taller tail of the FM-2, P-51H, etc. Even the B-24's later variants had a bigger tail.
Even later jets like the F11F and F-104 had tails changed during useage.
You would think that the designers would make the tail extra big from the start. Is it that the added weights of combat equipment made the craft unstable and the larger tail compensated or is it that the thin air of high altitude was not considered at first? (as with the B-17)
It seems that just about every U.S. combat plane benefited from redesigned tails.
It looks like other countries planes didn't change though.

 

[fastmongrel]

If you look at the changing pictures of fighter planes in the forum title you can see the difference in the tail of the 2 Spitfires.
The first Spit looks like a Mark 1 on the the second Spit (I dont know the Mark I am no expert but it is later because it has cannon) the tail fin is noticeably bigger

 

[imalko]

Germans did it too. Just look at the difference in tail size between Fw 190A and Fw 190D-9/Ta 152, Ju 88A and Ju 88G, late Bf 109G and Bf 109K in comparison to early variants...

 

[T Bolt]

This is kind of generalizing it, but most WW-II aircraft with any longevity of service life were updated with more powerful engines and had their weight increased a considerable amount as more equipment and fuel capacity was added. The power and to a lesser extent weight necessitated the increased area for control surfaces to maintain control of the aircraft. Just look at the difference in a Spitfire Mk1 with a an early Merlin at just over 1000hp and a Mk 24 with a Griffon 61 with twice the HP

 

[Knegel]

Hi,

afaik its more related to the additonal weight than the engine power. As more heavy the plane get, as more the plane will tend to swing with every controll(rudder) input, a bigger vertical stabilisator and/or a longer tail can compensate this.
This is specialy important for planes that operate at high alt or slow IAS.

Greetings,

Knegel

 

[Knegel]

Hi,

afaik its more related to the additonal weight than the engine power. As more heavy the plane get, as more the plane will tend to swing with every controll(rudder) input, a bigger vertical stabilisator and/or a longer tail can compensate this.
This is specialy important for planes that operate at high alt or slow IAS.

Greetings,

Knegel

 

[Glider]

I do hope that I remember this correctly and am happy to be corrected but I think it also has to do with directional stability.

When fighters were given bubble canopies the fuselages were cut down which reduced the wetted area which would have reduced the drag but also impacted the directional stability.

For this reason you find that the tail fins were increased in size (Spitfire) or an addition was made to the fin in the form of a fillet (P51).

I should add that this was in addition to the comments made about increased weight and having to operate at increased altitude. I think I am right when I say that the first Spit with an increased fin was the high altitude Mk VII.

Hope this helps and my memory is working

 

[Glider]

Duplicate posting

 

[Colin1]

I think I am right when I say that the first Spit with an increased fin was the high altitude Mk VII

I knew the HF VII had the revised rudder horn but had absolutely no idea if that made any difference to the tail surface area worth mentioning. I'm home now, so if we compare the Mk VII to its forebear, the Mk V (and therefore every model preceding it):

_______________Mk V________Mk VII
Tailplane________31.46_________31.46
Chord(ma)_______4.0__________4.0
Incidence________root 0________root 0
_______________tip +/-0.5______tip +/- 0.5
Elevator area_____13.26________13.26
Tab area________0.38__________0.38
Fin area_________4.61__________4.61
Rudder area_____8.23__________8.23
Tab area________0.35__________0.35

but an interesting comment from the official reports

Boscombe Down March 1943. BS229. Stability tests. Both lateral and directional stability was poorer than previous Spitfire marks and longitudinal neutral and poorer than the Mk V and VI. Increased horn balance on elevators.

 

[fastmongrel]

I knew the HF VII had the revised rudder horn but had absolutely no idea if that made any difference to the tail surface area worth mentioning. I'm home now, so if we compare the Mk VII to its forebear, the Mk V (and therefore every model preceding it):

_______________Mk V________Mk VII
Tailplane________31.46_________31.46
Chord(ma)_______4.0__________4.0
Incidence________root 0________root 0
_______________tip +/-0.5______tip +/- 0.5
Elevator area_____13.26________13.26
Tab area________0.38__________0.38
Fin area_________4.61__________4.61
Rudder area_____8.23__________8.23
Tab area________0.35__________0.35

but an interesting comment from the official reports

Boscombe Down March 1943. BS229. Stability tests. Both lateral and directional stability was poorer than previous Spitfire marks and longitudinal neutral and poorer than the Mk V and VI. Increased horn balance on elevators.

Thats odd the figures you have show the tail is the same size on the 2 marks but looking at pictures of the 2 aircraft the tail looks much bigger on the VII. Is it just the different shapes or am I reading the figures wrong. Which is a distinct possibility
MKVII

MKV

 

[Colin1]

Thats odd the figures you have show the tail is the same size on the 2 marks but looking at pictures of the 2 aircraft the tail looks much bigger on the VII. Is it just the different shapes or am I reading the figures wrong

Pretty sure I read them off correctly but I'll check when I get home

 

[Waynos]

The fin was exactly the same but the rudder was enlarged. AFAIK not all VII's (and not all IX's) were fitted with the bigger rudder though, so that may explain it.

 

[drgondog]

The vertical stabilizer size and location has two primary design inputs. Most important is low speed yaw control when the torgue of the engine and the low airspeed combinationrenders yaw control with rudder very difficult. At high speed, there generally is no issue but the 'tall tail' of the P-51H was about better yaw control in a high speed dive. The overall rudder area was about the same as the D, just taller.

Increasing gross weight not as critical as boosting engine horsepower/torque. The P-51H and (B/C) were all lighter than the D but the only addition to the D was the ventral 'fin' as noted below.

The low speed issue is more critical for carrier qual aircraft

Glider, the perception initially for the P-51D yaw in near transonic dive conditions was due to inadequate vertical stabilizer after the turtleback was removed, hence the addition of the ventral fin. That didn't appreciably alter the tendency to 'hunt' a little during the high speed dive. What solved the problem was extending the fuselage 13" when the H was designed - solving both the dive yaw issue and reducing dramatically the required trim and rudder pressures on take off.