Offset Fins

[dinghao]

Found an older post that touches on this.My question: Other than the Mustang , which other high performance aircraft had this feature?

[Steve Nelson]

I think the P-47 and Corsair have offset fins..probably many others as well.

SN

[Matt Gunsch]

The T-6 fin is offset as well

[The Inspector]

The SPAD (AD-1 thru 6) most definitely has an off set vertical and the Bf-109's vertical is flat on one side and curved on the other to offset torque. The Italians made one wing slightly longer than the other on lots of their WW2 fighters to counter torque.
While it's vertical is symmetrical every 727 flew with about 1/4 degree of or so right rudder trim always rolled in.

[Steve Nelson]

While it's vertical is symmetrical every 727 flew with about 1/4 degree of or so right rudder trim always rolled in.

Interesting..I never thought about torque being an issue with turbine engines, but I suupose rotating mass is rotating mass.


France's Bloch fighters had another interesting way of compensating for torque, by angling the engine slightly to one side.

SN

[redvanner]

The SPAD (AD-1 thru 6) most definitely has an off set vertical and the Bf-109's vertical is flat on one side and curved on the other to offset torque. The Italians made one wing slightly longer than the other on lots of their WW2 fighters to counter torque.
While it's vertical is symmetrical every 727 flew with about 1/4 degree of or so right rudder trim always rolled in.

The Hispano Aviacion HA 1109 - 1112´s also have asymmetrical fins, as they are Bf 109 licence built airframes. However when the Spanish could not get DB engines, they used Hispano-Suiza engines, rotating the other way round (left) as DB´s and Merlins (right). So the flat and the curved side of the fin changed sides with the batch equipped with HS engines (compared to the original 109´s, and the later batch equipped with Merlins from the start).
However, when the original HS engines were refitted with Merlins in (at least part of) the first production lot, the Spanish did not change the fin. So these planes had the "wrong" fin, or at least the wrong side curved, adding to the torque effect. Those beasties were even nastier to handle during start and landing than the usual fishy handling of the 109.
The first airframe of Messerschmitt Stiftungs G-6 D-FMBB (not the current!) was such a composite, starting with Hispano-Suiza > RR Merlin > DB 605 (in fact a Volvo licence one ). It was crashed during start around a year after maiden, beeing a 100% loss. No harm to the pilot though, the engine went into the 2. airframe, the current G-6 D-FMBB.
Other ones known to have (had) the "wrong" fin are OFMC`s G-BOML, and Air Fighter Academy`s D-FMVS (formerly with Harold Kindsvater), (both Buchons HS > RR engines) and the currently rebuilt Fighter Factory`s G-4 at MeierMotors, when it still was a Buchon (the new fuselage got a different fin, correct for the DB 605 it will receive).

So the fishy handling qualities of some Buchons or 109s using Buchon airframes is not necessarily a fault of the original design by Willy Messerschmitt, but the result of using a fin that added to the torque instead of diminishing it. Of couse this is only true for the a/c originally built with Hispano engines, and later refitted with Merlins (and DB´s), not for the ones that got RR`s when they were built (those got the correct fin for the right hand turning RR´s, HA did know what they were doing!). Maybe the Spanish Air Force should have refitted the fins as well when changing from HS to RR, but they might have thought it to be unnecessary or just too expensive. And at least they knew.

I bet, initially some or most of the private owners did not.

Michael

[The Inspector]

While it's vertical is symmetrical every 727 flew with about 1/4 degree of or so right rudder trim always rolled in.

Interesting..I never thought about torque being an issue with turbine engines, but I suupose rotating mass is rotating mass.


France's Bloch fighters had another interesting way of compensating for torque, by angling the engine slightly to one side.

SN

And, if the yaw dampner went out on a 27, you'd better be way low and way, way slow within about 8 or 9 minutes or Dutch roll with coupling effect would prove your undoing.

[shrike]

The SPAD (AD-1 thru 6) most definitely has an off set vertical and the Bf-109's vertical is flat on one side and curved on the other to offset torque. The Italians made one wing slightly longer than the other on lots of their WW2 fighters to counter torque.
While it's vertical is symmetrical every 727 flew with about 1/4 degree of or so right rudder trim always rolled in.

The Hispano Aviacion HA 1109 - 1112´s also have asymmetrical fins, as they are Bf 109 licence built airframes. However when the Spanish could not get DB engines, they used Hispano-Suiza engines, rotating the other way round (left) as DB´s and Merlins (right). So the flat and the curved side of the fin changed sides with the batch equipped with HS engines (compared to the original 109´s, and the later batch equipped with Merlins from the start).
However, when the original HS engines were refitted with Merlins in (at least part of) the first production lot, the Spanish did not change the fin. So these planes had the "wrong" fin, or at least the wrong side curved, adding to the torque effect. Those beasties were even nastier to handle during start and landing than the usual fishy handling of the 109.
The first airframe of Messerschmitt Stiftungs G-6 D-FMBB (not the current!) was such a composite, starting with Hispano-Suiza > RR Merlin > DB 605 (in fact a Volvo licence one ). It was crashed during start around a year after maiden, beeing a 100% loss. No harm to the pilot though, the engine went into the 2. airframe, the current G-6 D-FMBB.
Other ones known to have (had) the "wrong" fin are OFMC`s G-BOML, and Air Fighter Academy`s D-FMVS (formerly with Harold Kindsvater), (both Buchons HS > RR engines) and the currently rebuilt Fighter Factory`s G-4 at MeierMotors, when it still was a Buchon (the new fuselage got a different fin, correct for the DB 605 it will receive).

So the fishy handling qualities of some Buchons or 109s using Buchon airframes is not necessarily a fault of the original design by Willy Messerschmitt, but the result of using a fin that added to the torque instead of diminishing it. Of couse this is only true for the a/c originally built with Hispano engines, and later refitted with Merlins (and DB´s), not for the ones that got RR`s when they were built (those got the correct fin for the right hand turning RR´s, HA did know what they were doing!). Maybe the Spanish Air Force should have refitted the fins as well when changing from HS to RR, but they might have thought it to be unnecessary or just too expensive. And at least they knew.

I bet, initially some or most of the private owners did not.

Michael

The Soviets had the same issue when they re-engined some lend lease P-40's with Klimov M-105 as a field expedient.

[Randy Wilson]

The Curtiss SB2C Helldiver has a significant offset and still requires 8 degrees nose right for takeoff.

Randy

[51fixer]

For Most A/C the Fin offset isn't a feature to reduce torque loads on the pilot during take off.
It is designed as a function of cruise and calculated based on cruise speed and engine power used at that speed.
Every other operating speed will require re-trimming of the controls and liberal use of the rudder.
Does it assist in counteracting torque in all aspects , yes but with varying effectiveness. BUT, at high power it really isn't that effective or noticeable.
If it was based on torque for takeoff then the offset would be around 6 - 8 degrees.
Many of the fastest Reno racers have centered the Vertical with no advise effects.
Spitfire series lacks any offset AFAIK. They put engines that rotate both ways in the same airframe. The tail on the Griffon powered versions have a taller tail and bigger rudder. There isn't any offset in the vertical.

[The Inspector]

Just about every picture of an F4U CORSAIR in flight is carrying about 1 or so degrees of right rudder in cruise.

[b29flteng]

I think the Hurricane had an offset fin too.

[Dan Jones]

The dorsal fin on my old 90hp Champ is offset! Does that count?

Dan

[famvburg]

There's a 1950-something Cessna 172 based here at my airport with a noticeable offset to its fin.

[dinghao]

Thanks for the responses...I always assumed the offset was for torque control on hi perf planes.
It does seem to make sense that it's there for help during all phases.