Differences between twin tail and single tail

I had this very wierd dream last night, it could take forever to describe, but the basics are seeing the BoB Lanc fly over with Sally B’s single tail fin, and it made me think, what are the advantages and disadvantages of either a twin tail or large fin.
Avro obviously went for the twin tail, so did Handley Page and Consolidated with the Lib, Vickers, Boeing and Shorts didn’t. So what were the advantages of either, it being noticeable that Consolidated went for a large single tail on the Privateer in the end. I would have thought that a twin tail was more complicated to operate and more prone to damage in action, any thoughts on this from you ultra mechanical types.

This point hasn’t been brought up on the previous posts—— The B17 came out in 1935, after being in service for several years it was followed by the B24. The designers of the 24s took into account the features of the 17 and tried to improve on them. Therefore the B24 had a longer range, could carry a bigger bomb load and was able to fly faster, perhaps the twin tails played a part. However, some of the deficiencies were that they didn’t take into account was that it could’nt fly combat at B17’s altitude, could’nt keep in as tight formation as 17’s and most importantly couldn’t take the punishment that the 17 took

An argument for single fins…as has been pointed out later Liberator variants had single fins..PB4Y-2, B-24N….and the family related B-32.
Also, the Convair B-36 started out with twin fins but went to a single fin & rudder for production.
Since these planes tened to lose fins as they matured..I think we can safely assume their designers thought single fins were better in light of operational experince and as the designs (and aeronautical knowledge) improved.

Anorak alert!!! 😮 (And probably for weight considerations) the Twin Stinson also changed to a single fin when it was produced as Piper Apache.
Likewise there was a later field modification for Beech 18s to go to a single tail.

Argument for twin (or more) finsLike other 30’s designs, the Boeing 314 flying boat started out with a single small fin…to improve stability it was produced with the familiar two additional fins.

Many aircraft’s tails grew over the yaers. Either because the designers simply got it wrong the first time, or they had to add to fin as power increased.

Not sure what this adds to the argument, but here goes…

I believe two single-engine dive bomber designs, the Vultee Vengeance and the Junkers Ju87 both started out with twin tails. Not sure whether the Ju87 ever flew with this configuration, but the prototype Vengeance (according to Peter Smith’s ‘Vengeance!’) in its initial configuration made it as far as the end of the taxiway on what was to be its first flight when the test pilot stopped the aircraft, jumped out and declared that he was not going to fly it until it had had its tail replaced.

Both designs ended up with a rather large single fin.

Another reason for a twin fin (apologies if it’s already been brought up and I missed it) is that the fuselage is less likely to blanket the airflow over the fin during a spin making recovery easier. Although I imagine if you get into a spin in a Halifax or a B17 you are probably in a bit of trouble anyway…

But the Ju87 had those strange winglets on the tailplanes/elevators also….!

TT

Not sure what this adds to the argument, but here goes…

I believe two single-engine dive bomber designs, the Vultee Vengeance and the Junkers Ju87 both started out with twin tails. Not sure whether the Ju87 ever flew with this configuration, but the prototype Vengeance (according to Peter Smith’s ‘Vengeance!’) in its initial configuration made it as far as the end of the taxiway on what was to be its first flight when the test pilot stopped the aircraft, jumped out and declared that he was not going to fly it until it had had its tail replaced.

Both designs ended up with a rather large single fin.

Another reason for a twin fin (apologies if it’s already been brought up and I missed it) is that the fuselage is less likely to blanket the airflow over the fin during a spin making recovery easier. Although I imagine if you get into a spin in a Halifax or a B17 you are probably in a bit of trouble anyway…

Second attempt.

The twin tail was also the achilles heel of the early Hally’s because of inadequate finarea in combination with two engines out on the same side, the rudders locked over with predictable results. So two small fins were not a good proposition as opposed to one large fin.

CB

Didn’t the Hampden have a serious rudder locking problem before the Halifax?

Not that I know of but the Hampden is a smaller aircraft with less powerful and two engines. The Harrow also had similar rudders.

Then again, I am not an aerodynamicist (or whatsit).

Cees

Second attempt.

The twin tail was also the achilles heel of the early Hally’s because of inadequate finarea in combination with two engines out on the same side, the rudders locked over with predictable results. So two small fins were not a good proposition as opposed to one large fin.

CB

Didn’t the Hampden have a serious rudder locking problem before the Halifax?

[QUOTE=Cees Broere;1081462]
The twin tail was also the achilles heel of the early Hally’s because of inadequate finarea in combination with two engines out on the same side, the rudders locked over with predictable results. So two small fins were not a good proposition as opposed to one large fin.

One of the proposals for a Mk 4 Shackleton replaced the twin fins with a single large unit.

Hmm that ‘Shack’ looks really quite handsome.

…prompting the question….’will it be at Legends?!!!’

I’ll get my outer-wear garment!

Single Fin Shack

One of the proposals for a Mk 4 Shackleton replaced the twin fins with a single large unit.

Could you imagine a Constellation with a single tail? Just wouldn’t look right IMHO.
Obviously Douglas experimented with the twin tail on the DC5, but went back to the single fin for the 6 and 7

With bombers it was felt that a clear field of fire astern was desirable. And to prevent shooting of your own tail, the twin tail was a logical answer. Mind you that is what I might consider the reason behind this.:o

The twin tail was also the achilles heel of the early Hally’s because of inadequate finarea in combination with two engines out on the same side, the rudders locked over with predictable results. So two small fins were not a good proposition as opposed to one large fin.

The Hastings (being developed from the Halifax) was originally designed with a twin tail as well but that was quickly changed into a single tail. Stability was the reason probably.
The Lib (or PBY-4) was more stable with a single tail than with twin tails as well. The B-32 Dominator, same story.:rolleyes:

Cheers

Cees

I remain to be convinced that the rudders on the SR71 are in the ‘slipstream’ of the engines 😉

Moggy

Oh alright you got me there, it was obviously just force of habit by Kelly…:D

Ask yourself… “which one fits in existing hangars, and if I have to build new hangars anyway, which one would require the cheapest hangar to build?”.[/QUOTE]

So would not have this been an argument towards providing a twin tail for the Stirling, considering contemporary hangar size forming the excuse for it’s short wingspan.

I have heard on a couple of documentaries on Kelly Johnson and his team at Lockheed, that they liked to have a rudder in the slipstream of each engine

I remain to be convinced that the rudders on the SR71 are in the ‘slipstream’ of the engines 😉

Moggy

There is also a more practical advantage to the multi-finned approach… look at the B-24, and then at the PB4Y-2 Privateer (the PB4Y-1 Liberator was a B-24 with USN radios, etc.).

Ask yourself… “which one fits in existing hangars, and if I have to build new hangars anyway, which one would require the cheapest hangar to build?”.

I have heard on a couple of documentaries on Kelly Johnson and his team at Lockheed, that they liked to have a rudder in the slipstream of each engine, where practical, to offset some of the effects of assymetric thrust. Some of the examples of this are:
Electra/Hudson/Ventura
P38
Constellation (4 was pushing it, so they stuck with 3)
Blackbird! (Remember the 1 Afterburner flypast at Mildenhall Air Fete with both Rudders on full deflection)
and there were probably others

It is true that there seemed to be a flurry of twin tail/fin designs in the late 1930’s early 1940’s and although the US manufacturers had a few types with twin tails, P38/B24, they seemed to return quickly to the single fin. The British use through the Heavy bombers of Halifax, Manchester and Lancaster continued on to the Lincoln and Shackelton postwar whereas the B-24 Liberator shed its twin tail in its PB4Y Privateer form.

I think generally the technical argument was based on a smaller total fin area being required by removal “outboard” of the fuselage slipstream, a futher benefit of control response at low airspeeds was claimed in having the fin/rudder being directly behind the thrust line and airflow of the engine/props, particularly on take-off etc.

I personally believe it had nothing to do with such technical theory or argument and that it was a simple extension of the old british view that “two heads are better than one”, and therefore so too should be two tails! smiles

(Of course the US took the British literally and built the F-82 Twin Mustang, but couldnt fit two cockpits to most other aircraft so the idea was shelved!)

regards

Mark Pilkington

A compound tail unit has greater redundancy, hence the fitting of same to the Warthog.

Moggy